











	       Xlib - C Language X Interface

		   X Consortium Standard

		 X Version 11, Release 6.4






			James Gettys
	       Cambridge Research Laboratory
	       Digital Equipment Corporation


		    Robert W. Scheifler
	      Laboratory for Computer Science
	   Massachusetts Institute of Technology



		  with contributions from



		Chuck Adams, Tektronix, Inc.

	  Vania Joloboff, Open Software Foundation

		Hideki Hiura, SunSoft, Inc.

	   Bill McMahon, Hewlett-Packard Company

     Ron Newman, Massachusetts Institute of Technology

	       Al Tabayoyon, Tektronix, Inc.

	       Glenn Widener, Tektronix, Inc.

		Shigeru Yamada, Fujitsu OSSI





























The X Window System is a trademark of X Consortium, Inc.

TekHVC is a trademark of Tektronix, Inc.



Copyright (C) 1985, 1986, 1987, 1988, 1989, 1990, 1991,
1994,1996 X Consortium

Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documenta-
tion files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use,
copy, modify, merge, publish, distribute, sublicense, and/or
sell copies of the Software, and to permit persons to whom
the Software is furnished to do so, subject to the following
conditions:

The above copyright notice and this permission notice shall
be included in all copies or substantial portions of the
Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PUR-
POSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE X CONSOR-
TIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
OR OTHER DEALINGS IN THE SOFTWARE.

Except as contained in this notice, the name of the X Con-
sortium shall not be used in advertising or otherwise to
promote the sale, use or other dealings in this Software
without prior written authorization from the X Consortium.




Copyright (C) 1985, 1986, 1987, 1988, 1989, 1990, 1991 by
Digital Equipment Corporation

Portions Copyright (C) 1990, 1991 by Tektronix, Inc.













Permission to use, copy, modify and distribute this documen-
tation for any purpose and without fee is hereby granted,
provided that the above copyright notice appears in all
copies and that both that copyright notice and this permis-
sion notice appear in all copies, and that the names of Dig-
ital and Tektronix not be used in in advertising or public-
ity pertaining to this documentation without specific, writ-
ten prior permission.  Digital and Tektronix makes no repre-
sentations about the suitability of this documentation for
any purpose.  It is provided ``as is'' without express or
implied warranty.

























































		      Acknowledgments



The design and implementation of the first 10 versions of X
were primarily the work of three individuals: Robert Schei-
fler of the MIT Laboratory for Computer Science and Jim Get-
tys of Digital Equipment Corporation and Ron Newman of MIT,
both at MIT Project Athena.  X version 11, however, is the
result of the efforts of dozens of individuals at almost as
many locations and organizations.  At the risk of offending
some of the players by exclusion, we would like to acknowl-
edge some of the people who deserve special credit and
recognition for their work on Xlib.  Our apologies to anyone
inadvertently overlooked.

Release 1

Our thanks does to Ron Newman (MIT Project Athena), who con-
tributed substantially to the design and implementation of
the Version 11 Xlib interface.

Our thanks also goes to Ralph Swick (Project Athena and Dig-
ital) who kept it all together for us during the early
releases.  He handled literally thousands of requests from
people everywhere and saved the sanity of at least one of
us.  His calm good cheer was a foundation on which we could
build.

Our thanks also goes to Todd Brunhoff (Tektronix) who was
``loaned'' to Project Athena at exactly the right moment to
provide very capable and much-needed assistance during the
alpha and beta releases.  He was responsible for the suc-
cessful integration of sources from multiple sites; we would
not have had a release without him.

Our thanks also goes to Al Mento and Al Wojtas of Digital's
ULTRIX Documentation Group.  With good humor and cheer, they
took a rough draft and made it an infinitely better and more
useful document.  The work they have done will help many
everywhere.  We also would like to thank Hal Murray (Digital
SRC) and Peter George (Digital VMS) who contributed much by
proofreading the early drafts of this document.

Our thanks also goes to Jeff Dike (Digital UEG), Tom Benson,
Jackie Granfield, and Vince Orgovan (Digital VMS) who helped
with the library utilities implementation; to Hania Gajewska
(Digital UEG-WSL) who, along with Ellis Cohen (CMU and
Siemens), was instrumental in the semantic design of the
window manager properties; and to Dave Rosenthal (Sun
Microsystems) who also contributed to the protocol and pro-
vided the sample generic color frame buffer device-dependent












code.

The alpha and beta test participants deserve special recog-
nition and thanks as well.  It is significant that the bug
reports (and many fixes) during alpha and beta test came
almost exclusively from just a few of the alpha testers,
mostly hardware vendors working on product implementations
of X.  The continued public contribution of vendors and uni-
versities is certainly to the benefit of the entire X commu-
nity.

Our special thanks must go to Sam Fuller, Vice-President of
Corporate Research at Digital, who has remained committed to
the widest public availability of X and who made it possible
to greatly supplement MIT's resources with the Digital staff
in order to make version 11 a reality.	Many of the people
mentioned here are part of the Western Software Laboratory
(Digital UEG-WSL) of the ULTRIX Engineering group and work
for Smokey Wallace, who has been vital to the project's suc-
cess.  Others not mentioned here worked on the toolkit and
are acknowledged in the X Toolkit documentation.

Of course, we must particularly thank Paul Asente, formerly
of Stanford University and now of Digital UEG-WSL, who wrote
W, the predecessor to X, and Brian Reid, formerly of Stan-
ford University and now of Digital WRL, who had much to do
with W's design.

Finally, our thanks goes to MIT,  Digital Equipment Corpora-
tion, and IBM for providing the environment where it could
happen.

Release 4

Our thanks go to Jim Fulton (MIT X Consortium) for designing
and specifying the new Xlib functions for Inter-Client Com-
munication Conventions (ICCCM) support.

We also thank Al Mento of Digital for his continued effort
in maintaining this document and Jim Fulton and Donna Con-
verse (MIT X Consortium) for their much-appreciated efforts
in reviewing the changes.

Release 5

The principal authors of the Input Method facilities are
Vania Joloboff (Open Software Foundation) and Bill McMahon
(Hewlett-Packard).  The principal author of the rest of the
internationalization facilities is Glenn Widener (Tek-
tronix).  Our thanks to them for keeping their sense of
humor through a long and sometimes difficult design process.
Although the words and much of the design are due to them,
many others have contributed substantially to the design and
implementation.  Tom McFarland (HP) and Frank Rojas (IBM)












deserve particular recognition for their contributions.
Other contributors were: Tim Anderson (Motorola), Alka Bad-
shah (OSF), Gabe Beged-Dov (HP), Chih-Chung Ko (III), Vera
Cheng (III), Michael Collins (Digital), Walt Daniels (IBM),
Noritoshi Demizu (OMRON), Keisuke Fukui (Fujitsu), Hitoshoi
Fukumoto (Nihon Sun), Tim Greenwood (Digital), John Harvey
(IBM), Hideki Hiura (Sun), Fred Horman (AT&T), Norikazu
Kaiya (Fujitsu), Yuji Kamata (IBM), Yutaka Kataoka (Waseda
University), Ranee Khubchandani (Sun), Akira Kon (NEC),
Hiroshi Kuribayashi (OMRON), Teruhiko Kurosaka (Sun), Seiji
Kuwari (OMRON), Sandra Martin (OSF), Narita Masahiko
(Fujitsu), Masato Morisaki (NTT), Nelson Ng (Sun), Takashi
Nishimura (NTT America), Makato Nishino (IBM), Akira Ohsone
(Nihon Sun), Chris Peterson (MIT), Sam Shteingart (AT&T),
Manish Sheth (AT&T), Muneiyoshi Suzuki (NTT), Cori Mehring
(Digital), Shoji Sugiyama (IBM), and Eiji Tosa (IBM).

We are deeply indebted to Tatsuya Kato (NTT), Hiroshi Kurib-
ayashi (OMRON), Seiji Kuwari (OMRON), Muneiyoshi Suzuki
(NTT), and Li Yuhong (OMRON) for producing one of the first
complete sample implementation of the internationalization
facilities, and Hiromu Inukai (Nihon Sun), Takashi Fujiwara
(Fujitsu), Hideki Hiura (Sun), Yasuhiro Kawai (Oki Tech-
nosystems Laboratory), Kazunori Nishihara (Fuji Xerox),
Masaki Takeuchi (Sony), Katsuhisa Yano (Toshiba), Makoto
Wakamatsu (Sony Corporation) for producing the another com-
plete sample implementation of the internationalization
facilities.

The principal authors (design and implementation) of the
Xcms color management facilities are Al Tabayoyon (Tek-
tronix) and Chuck Adams (Tektronix).  Joann Taylor (Tek-
tronix), Bob Toole (Tektronix), and Keith Packard (MIT X
Consortium) also contributed significantly to the design.
Others who contributed are: Harold Boll (Kodak), Ken Bron-
stein (HP), Nancy Cam (SGI), Donna Converse (MIT X Consor-
tium), Elias Israel (ISC), Deron Johnson (Sun), Jim King
(Adobe), Ricardo Motta (HP), Chuck Peek (IBM), Wil Plouffe
(IBM), Dave Sternlicht (MIT X Consortium), Kumar Talluri
(AT&T), and Richard Verberg (IBM).

We also once again thank Al Mento of Digital for his work in
formatting and reformatting text for this manual, and for
producing man pages.  Thanks also to Clive Feather (IXI) for
proof-reading and finding a number of small errors.

Release 6

Stephen Gildea (X Consortium) authored the threads support.
Ovais Ashraf (Sun) and Greg Olsen (Sun) contributed substan-
tially by testing the facilities and reporting bugs in a
timely fashion.














The principal authors of the internationalization facili-
ties, including Input and Output Methods, are Hideki Hiura
(SunSoft) and Shigeru Yamada (Fujitsu OSSI).  Although the
words and much of the design are due to them, many others
have contributed substantially to the design and implementa-
tion.  They are: Takashi Fujiwara (Fujitsu), Yoshio Horiuchi
(IBM), Makoto Inada (Digital), Hiromu Inukai (Nihon Sun-
Soft), Song JaeKyung (KAIST), Franky Ling (Digital), Tom
McFarland (HP), Hiroyuki Miyamoto (Digital), Masahiko Narita
(Fujitsu), Frank Rojas (IBM), Hidetoshi Tajima (HP), Masaki
Takeuchi (Sony), Makoto Wakamatsu (Sony), Masaki Wakao
(IBM), Katsuhisa Yano(Toshiba) and Jinsoo Yoon (KAIST).

The principal producers of the sample implementation of the
internationalization facilities are: Jeffrey Bloomfield
(Fujitsu OSSI), Takashi Fujiwara (Fujitsu), Hideki Hiura
(SunSoft), Yoshio Horiuchi (IBM), Makoto Inada (Digital),
Hiromu Inukai (Nihon SunSoft), Song JaeKyung (KAIST), Riki
Kawaguchi (Fujitsu), Franky Ling (Digital), Hiroyuki
Miyamoto (Digital), Hidetoshi Tajima (HP), Toshimitsu Tera-
zono (Fujitsu), Makoto Wakamatsu (Sony), Masaki Wakao (IBM),
Shigeru Yamada (Fujitsu OSSI) and Katsuhisa Yano (Toshiba).

The coordinators of the integration, testing, and release of
this implementation of the internationalization facilities
are Nobuyuki Tanaka (Sony) and Makoto Wakamatsu (Sony).

Others who have contributed to the architectural design or
testing of the sample implementation of the international-
ization facilities are: Hector Chan (Digital), Michael Kung
(IBM), Joseph Kwok (Digital), Hiroyuki Machida (Sony), Nel-
son Ng (SunSoft), Frank Rojas (IBM), Yoshiyuki Segawa
(Fujitsu OSSI), Makiko Shimamura (Fujitsu), Shoji Sugiyama
(IBM), Lining Sun (SGI), Masaki Takeuchi (Sony), Jinsoo Yoon
(KAIST) and Akiyasu Zen (HP).




Jim Gettys
Cambridge Research Laboratory
Digital Equipment Corporation

Robert W. Scheifler
Laboratory for Computer Science
Massachusetts Institute of Technology






















			 Chapter 1

		    Introduction to Xlib



The X Window System is a network-transparent window system
that was designed at MIT.  X display servers run on comput-
ers with either monochrome or color bitmap display hardware.
The server distributes user input to and accepts output
requests from various client programs located either on the
same machine or elsewhere in the network.  Xlib is a C sub-
routine library that application programs (clients) use to
interface with the window system by means of a stream con-
nection.  Although a client usually runs on the same machine
as the X server it is talking to, this need not be the case.

Xlib - C Language X Interface is a reference guide to the
low-level C language interface to the X Window System proto-
col.  It is neither a tutorial nor a user's guide to pro-
gramming the X Window System.  Rather, it provides a
detailed description of each function in the library as well
as a discussion of the related background information.	Xlib
- C Language X Interface assumes a basic understanding of a
graphics window system and of the C programming language.
Other higher-level abstractions (for example, those provided
by the toolkits for X) are built on top of the Xlib library.
For further information about these higher-level libraries,
see the appropriate toolkit documentation.  The X Window
System Protocol provides the definitive word on the behavior
of X.  Although additional information appears here, the
protocol document is the ruling document.

To provide an introduction to X programming, this chapter
discusses:

o    Overview of the X Window System

o    Errors

o    Standard header files

o    Generic values and types

o    Naming and argument conventions within Xlib

o    Programming considerations

o    Character sets and encodings

o    Formatting conventions




			      1





Xlib - C Library			    X11, Release 6.4


1.1.  Overview of the X Window System

Some of the terms used in this book are unique to X, and
other terms that are common to other window systems have
different meanings in X.  You may find it helpful to refer
to the glossary, which is located at the end of the book.

The X Window System supports one or more screens containing
overlapping windows or subwindows.  A screen is a physical
monitor and hardware that can be color, grayscale, or
monochrome.  There can be multiple screens for each display
or workstation.  A single X server can provide display ser-
vices for any number of screens.  A set of screens for a
single user with one keyboard and one pointer (usually a
mouse) is called a display.

All the windows in an X server are arranged in strict hier-
archies.  At the top of each hierarchy is a root window,
which covers each of the display screens.  Each root window
is partially or completely covered by child windows.  All
windows, except for root windows, have parents.  There is
usually at least one window for each application program.
Child windows may in turn have their own children.  In this
way, an application program can create an arbitrarily deep
tree on each screen.  X provides graphics, text, and raster
operations for windows.

A child window can be larger than its parent.  That is, part
or all of the child window can extend beyond the boundaries
of the parent, but all output to a window is clipped by its
parent.  If several children of a window have overlapping
locations, one of the children is considered to be on top of
or raised over the others, thus obscuring them.  Output to
areas covered by other windows is suppressed by the window
system unless the window has backing store.  If a window is
obscured by a second window, the second window obscures only
those ancestors of the second window that are also ancestors
of the first window.

A window has a border zero or more pixels in width, which
can be any pattern (pixmap) or solid color you like.  A win-
dow usually but not always has a background pattern, which
will be repainted by the window system when uncovered.
Child windows obscure their parents, and graphic operations
in the parent window usually are clipped by the children.

Each window and pixmap has its own coordinate system.  The
coordinate system has the X axis horizontal and the Y axis
vertical with the origin [0, 0] at the upper-left corner.
Coordinates are integral, in terms of pixels, and coincide
with pixel centers.  For a window, the origin is inside the
border at the inside, upper-left corner.





			      2





Xlib - C Library			    X11, Release 6.4


X does not guarantee to preserve the contents of windows.
When part or all of a window is hidden and then brought back
onto the screen, its contents may be lost.  The server then
sends the client program an Expose event to notify it that
part or all of the window needs to be repainted.  Programs
must be prepared to regenerate the contents of windows on
demand.

X also provides off-screen storage of graphics objects,
called pixmaps.  Single plane (depth 1) pixmaps are some-
times referred to as bitmaps.  Pixmaps can be used in most
graphics functions interchangeably with windows and are used
in various graphics operations to define patterns or tiles.
Windows and pixmaps together are referred to as drawables.

Most of the functions in Xlib just add requests to an output
buffer.  These requests later execute asynchronously on the
X server.  Functions that return values of information
stored in the server do not return (that is, they block)
until an explicit reply is received or an error occurs.  You
can provide an error handler, which will be called when the
error is reported.

If a client does not want a request to execute asyn-
chronously, it can follow the request with a call to XSync,
which blocks until all previously buffered asynchronous
events have been sent and acted on.  As an important side
effect, the output buffer in Xlib is always flushed by a
call to any function that returns a value from the server or
waits for input.

Many Xlib functions will return an integer resource ID,
which allows you to refer to objects stored on the X server.
These can be of type Window, Font, Pixmap, Colormap, Cursor,
and GContext, as defined in the file <X11/X.h>.  These
resources are created by requests and are destroyed (or
freed) by requests or when connections are closed.  Most of
these resources are potentially sharable between applica-
tions, and in fact, windows are manipulated explicitly by
window manager programs.  Fonts and cursors are shared auto-
matically across multiple screens.  Fonts are loaded and
unloaded as needed and are shared by multiple clients.
Fonts are often cached in the server.  Xlib provides no sup-
port for sharing graphics contexts between applications.

Client programs are informed of events.  Events may either
be side effects of a request (for example, restacking win-
dows generates Expose events) or completely asynchronous
(for example, from the keyboard).  A client program asks to
be informed of events.	Because other applications can send
events to your application, programs must be prepared to
handle (or ignore) events of all types.





			      3





Xlib - C Library			    X11, Release 6.4


Input events (for example, a key pressed or the pointer
moved) arrive asynchronously from the server and are queued
until they are requested by an explicit call (for example,
XNextEvent or XWindowEvent).  In addition, some library
functions (for example, XRaiseWindow) generate Expose and
ConfigureRequest events.  These events also arrive asyn-
chronously, but the client may wish to explicitly wait for
them by calling XSync after calling a function that can
cause the server to generate events.

1.2.  Errors

Some functions return Status, an integer error indication.
If the function fails, it returns a zero.  If the function
returns a status of zero, it has not updated the return
arguments.  Because C does not provide multiple return val-
ues, many functions must return their results by writing
into client-passed storage.  By default, errors are handled
either by a standard library function or by one that you
provide.  Functions that return pointers to strings return
NULL pointers if the string does not exist.

The X server reports protocol errors at the time that it
detects them.  If more than one error could be generated for
a given request, the server can report any of them.

Because Xlib usually does not transmit requests to the
server immediately (that is, it buffers them), errors can be
reported much later than they actually occur.  For debugging
purposes, however, Xlib provides a mechanism for forcing
synchronous behavior (see section 11.8.1).  When synchro-
nization is enabled, errors are reported as they are gener-
ated.

When Xlib detects an error, it calls an error handler, which
your program can provide.  If you do not provide an error
handler, the error is printed, and your program terminates.

1.3.  Standard Header Files

The following include files are part of the Xlib standard:

o    <X11/Xlib.h>

     This is the main header file for Xlib.  The majority of
     all Xlib symbols are declared by including this file.
     This file also contains the preprocessor symbol Xlib-
     SpecificationRelease.  This symbol is defined to have
     the 6 in this release of the standard.  (Release 5 of
     Xlib was the first release to have this symbol.)

o    <X11/X.h>





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Xlib - C Library			    X11, Release 6.4


     This file declares types and constants for the X proto-
     col that are to be used by applications.  It is
     included automatically from <X11/Xlib.h>, so applica-
     tion code should never need to reference this file
     directly.

o    <X11/Xcms.h>

     This file contains symbols for much of the color man-
     agement facilities described in chapter 6.  All func-
     tions, types, and symbols with the prefix ``Xcms'',
     plus the Color Conversion Contexts macros, are declared
     in this file.  <X11/Xlib.h> must be included before
     including this file.

o    <X11/Xutil.h>

     This file declares various functions, types, and sym-
     bols used for inter-client communication and applica-
     tion utility functions, which are described in chapters
     14 and 16.  <X11/Xlib.h> must be included before
     including this file.

o    <X11/Xresource.h>

     This file declares all functions, types, and symbols
     for the resource manager facilities, which are
     described in chapter 15.  <X11/Xlib.h> must be included
     before including this file.

o    <X11/Xatom.h>

     This file declares all predefined atoms, which are sym-
     bols with the prefix ``XA_''.

o    <X11/cursorfont.h>

     This file declares the cursor symbols for the standard
     cursor font, which are listed in appendix B.  All cur-
     sor symbols have the prefix ``XC_''.

o    <X11/keysymdef.h>

     This file declares all standard KeySym values, which
     are symbols with the prefix ``XK_''.  The KeySyms are
     arranged in groups, and a preprocessor symbol controls
     inclusion of each group.  The preprocessor symbol must
     be defined prior to inclusion of the file to obtain the
     associated values.  The preprocessor symbols are
     XK_MISCELLANY, XK_XKB_KEYS, XK_3270, XK_LATIN1,
     XK_LATIN2, XK_LATIN3, XK_LATIN4, XK_KATAKANA, XK_ARA-
     BIC, XK_CYRILLIC, XK_GREEK, XK_TECHNICAL, XK_SPECIAL,
     XK_PUBLISHING, XK_APL, XK_HEBREW, XK_THAI, and
     XK_KOREAN.



			      5





Xlib - C Library			    X11, Release 6.4


o    <X11/keysym.h>

     This file defines the preprocessor symbols XK_MISCEL-
     LANY, XK_XKB_KEYS, XK_LATIN1, XK_LATIN2, XK_LATIN3,
     XK_LATIN4, and XK_GREEK and then includes
     <X11/keysymdef.h>.

o    <X11/Xlibint.h>

     This file declares all the functions, types, and sym-
     bols used for extensions, which are described in
     appendix C.  This file automatically includes
     <X11/Xlib.h>.

o    <X11/Xproto.h>

     This file declares types and symbols for the basic X
     protocol, for use in implementing extensions.  It is
     included automatically from <X11/Xlibint.h>, so appli-
     cation and extension code should never need to refer-
     ence this file directly.

o    <X11/Xprotostr.h>

     This file declares types and symbols for the basic X
     protocol, for use in implementing extensions.  It is
     included automatically from <X11/Xproto.h>, so applica-
     tion and extension code should never need to reference
     this file directly.

o    <X11/X10.h>

     This file declares all the functions, types, and sym-
     bols used for the X10 compatibility functions, which
     are described in appendix D.

1.4.  Generic Values and Types

The following symbols are defined by Xlib and used through-
out the manual:

o    Xlib defines the type Bool and the Boolean values True
     and False.

o    None is the universal null resource ID or atom.

o    The type XID is used for generic resource IDs.

o    The type XPointer is defined to be char* and is used as
     a generic opaque pointer to data.







			      6





Xlib - C Library			    X11, Release 6.4


1.5.  Naming and Argument Conventions within Xlib

Xlib follows a number of conventions for the naming and syn-
tax of the functions.  Given that you remember what informa-
tion the function requires, these conventions are intended
to make the syntax of the functions more predictable.

The major naming conventions are:

o    To differentiate the X symbols from the other symbols,
     the library uses mixed case for external symbols.	It
     leaves lowercase for variables and all uppercase for
     user macros, as per existing convention.

o    All Xlib functions begin with a capital X.

o    The beginnings of all function names and symbols are
     capitalized.

o    All user-visible data structures begin with a capital
     X.  More generally, anything that a user might derefer-
     ence begins with a capital X.

o    Macros and other symbols do not begin with a capital X.
     To distinguish them from all user symbols, each word in
     the macro is capitalized.

o    All elements  of or variables in a data structure are
     in lowercase.  Compound words, where needed, are con-
     structed with underscores (_).

o    The display argument, where used, is always first in
     the argument list.

o    All resource objects, where used, occur at the begin-
     ning of the argument list immediately after the display
     argument.

o    When a  graphics context is present together with
     another type of resource (most commonly, a drawable),
     the graphics context occurs in the argument list after
     the other resource.  Drawables outrank all other
     resources.

o    Source arguments always precede the destination argu-
     ments in the argument list.

o    The x argument always precedes the y argument in the
     argument list.

o    The width argument always precedes the height argument
     in the argument list.





			      7





Xlib - C Library			    X11, Release 6.4


o    Where the x, y, width, and height arguments are used
     together, the x and y arguments always precede the
     width and height arguments.

o    Where a mask is accompanied with a structure, the mask
     always precedes the pointer to the structure in the
     argument list.

1.6.  Programming Considerations

The major programming considerations are:

o    Coordinates and sizes in X are actually 16-bit quanti-
     ties.  This decision was made to minimize the bandwidth
     required for a given level of performance.  Coordinates
     usually are declared as an int in the interface.  Val-
     ues larger than 16 bits are truncated silently.  Sizes
     (width and height) are declared as unsigned quantities.

o    Keyboards are the greatest variable between different
     manufacturers' workstations.  If you want your program
     to be portable, you should be particularly conservative
     here.

o    Many display systems have limited amounts of off-screen
     memory.  If you can, you should minimize use of pixmaps
     and backing store.

o    The user should have control of his screen real estate.
     Therefore, you should write your applications to react
     to window management rather than presume control of the
     entire screen.  What you do inside of your top-level
     window, however, is up to your application.  For fur-
     ther information, see chapter 14 and the Inter-Client
     Communication Conventions Manual.

1.7.  Character Sets and Encodings

Some of the Xlib functions make reference to specific char-
acter sets and character encodings.  The following are the
most common:

o    X Portable Character Set

     A basic set of 97 characters, which are assumed to
     exist in all locales supported by Xlib.  This set con-
     tains the following characters:


a..z A..Z 0..9 !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~ <space>,
<tab>, and <newline>






			      8





Xlib - C Library			    X11, Release 6.4


     This set is the left/lower half of the graphic charac-
     ter set of ISO8859-1 plus space, tab, and newline.  It
     is also the set of graphic characters in 7-bit ASCII
     plus the same three control characters.  The actual
     encoding of these characters on the host is system
     dependent.

o    Host Portable Character Encoding

     The encoding of the X Portable Character Set on the
     host.  The encoding itself is not defined by this stan-
     dard, but the encoding must be the same in all locales
     supported by Xlib on the host.  If a string is said to
     be in the Host Portable Character Encoding, then it
     only contains characters from the X Portable Character
     Set, in the host encoding.

o    Latin-1

     The coded character set defined by the ISO 8859-1 stan-
     dard.

o    Latin Portable Character Encoding

     The encoding of the X Portable Character Set using the
     Latin-1 codepoints plus ASCII control characters.	If a
     string is said to be in the Latin Portable Character
     Encoding, then it only contains characters from the X
     Portable Character Set, not all of Latin-1.

o    STRING Encoding

     Latin-1, plus tab and newline.

o    UTF-8 Encoding

     The ASCII compatible character encoding scheme defined
     by the ISO 10646-1 standard.

o    POSIX Portable Filename Character Set

     The set of 65 characters, which can be used in naming
     files on a POSIX-compliant host, that are correctly
     processed in all locales.	The set is:


     a..z A..Z 0..9 ._-


1.8.  Formatting Conventions

Xlib - C Language X Interface uses the following conven-
tions:




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Xlib - C Library			    X11, Release 6.4


o    Global symbols are printed in this special font.  These
     can be either function names, symbols defined in
     include files, or structure names.  When declared and
     defined, function arguments are printed in italics.  In
     the explanatory text that follows, they usually are
     printed in regular type.

o    Each function is introduced by a general discussion
     that distinguishes it from other functions.  The func-
     tion declaration itself follows, and each argument is
     specifically explained.  Although ANSI C function pro-
     totype syntax is not used, Xlib header files normally
     declare functions using function prototypes in ANSI C
     environments.  General discussion of the function, if
     any is required, follows the arguments.  Where applica-
     ble, the last paragraph of the explanation lists the
     possible Xlib error codes that the function can gener-
     ate.  For a complete discussion of the Xlib error
     codes, see section 11.8.2.

o    To eliminate any ambiguity between those arguments that
     you pass and those that a function returns to you, the
     explanations for all arguments that you pass start with
     the word specifies or, in the case of multiple argu-
     ments, the word specify.  The explanations for all
     arguments that are returned to you start with the word
     returns or, in the case of multiple arguments, the word
     return.  The explanations for all arguments that you
     can pass and are returned start with the words speci-
     fies and returns.

o    Any pointer to a structure that is used to return a
     value is designated as such by the _return suffix as
     part of its name.	All other pointers passed to these
     functions are used for reading only.  A few arguments
     use pointers to structures that are used for both input
     and output and are indicated by using the _in_out suf-
     fix.



















			     10





Xlib - C Library			    X11, Release 6.4




			    Chapter 2

			Display Functions



Before your program can use a display, you must establish a
connection to the X server.  Once you have established a
connection, you then can use the Xlib macros and functions
discussed in this chapter to return information about the
display.  This chapter discusses how to:

o    Open (connect to) the display

o    Obtain information about the display, image formats, or
     screens

o    Generate a NoOperation protocol request

o    Free client-created data

o    Close (disconnect from) a display

o    Use X Server connection close operations

o    Use Xlib with threads

o    Use internal connections

2.1.  Opening the Display

To open a connection to the X server that controls a dis-
play, use XOpenDisplay.

__
|
Display *XOpenDisplay(display_name)
      char *display_name;


display_name
	  Specifies the hardware display name, which deter-
	  mines the display and communications domain to be
	  used.  On a POSIX-conformant system, if the dis-
	  play_name is NULL, it defaults to the value of the
	  DISPLAY environment variable.
|__

The encoding and interpretation of the display name are
implementation-dependent.  Strings in the Host Portable
Character Encoding are supported; support for other charac-
ters is implementation-dependent.  On POSIX-conformant



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Xlib - C Library			    X11, Release 6.4


systems, the display name or DISPLAY environment variable
can be a string in the format:

__
|
	  hostname:number.screen_number


hostname  Specifies the name of the host machine on which
	  the display is physically attached.  You follow
	  the hostname with either a single colon (:) or a
	  double colon (::).

number	  Specifies the number of the display server on that
	  host machine.  You may optionally follow this dis-
	  play number with a period (.).  A single CPU can
	  have more than one display.  Multiple displays are
	  usually numbered starting with zero.

screen_number
	  Specifies the screen to be used on that server.
	  Multiple screens can be controlled by a single X
	  server.  The screen_number sets an internal vari-
	  able that can be accessed by using the Default-
	  Screen macro or the XDefaultScreen function if you
	  are using languages other than C (see section
	  2.2.1).
|__

For example, the following would specify screen 1 of display
0 on the machine named ``dual-headed'':


     dual-headed:0.1


The XOpenDisplay function returns a Display structure that
serves as the connection to the X server and that contains
all the information about that X server.  XOpenDisplay con-
nects your application to the X server through TCP or DECnet
communications protocols, or through some local inter-pro-
cess communication protocol.  If the hostname is a host
machine name and a single colon (:) separates the hostname
and display number, XOpenDisplay connects using TCP streams.
If the hostname is not specified, Xlib uses whatever it
believes is the fastest transport.  If the hostname is a
host machine name and a double colon (::) separates the
hostname and display number, XOpenDisplay connects using
DECnet.  A single X server can support any or all of these
transport mechanisms simultaneously.  A particular Xlib
implementation can support many more of these transport
mechanisms.





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Xlib - C Library			    X11, Release 6.4


If successful, XOpenDisplay returns a pointer to a Display
structure, which is defined in <X11/Xlib.h>.  If XOpenDis-
play does not succeed, it returns NULL.  After a successful
call to XOpenDisplay, all of the screens in the display can
be used by the client.	The screen number specified in the
display_name argument is returned by the DefaultScreen macro
(or the XDefaultScreen function).  You can access elements
of the Display and Screen structures only by using the
information macros or functions.  For information about
using macros and functions to obtain information from the
Display structure, see section 2.2.1.

X servers may implement various types of access control
mechanisms (see section 9.8).

2.2.  Obtaining Information about the Display, Image For-
mats, or Screens

The Xlib library provides a number of useful macros and cor-
responding functions that return data from the Display
structure.  The macros are used for C programming, and their
corresponding function equivalents are for other language
bindings.  This section discusses the:

o    Display macros

o    Image format functions and macros

o    Screen information macros

All other members of the Display structure (that is, those
for which no macros are defined) are private to Xlib and
must not be used.  Applications must never directly modify
or inspect these private members of the Display structure.

			    Note

     The XDisplayWidth, XDisplayHeight, XDisplayCells,
     XDisplayPlanes, XDisplayWidthMM, and XDisplay-
     HeightMM functions in the next sections are mis-
     named.  These functions really should be named
     Screenwhatever and XScreenwhatever, not Display-
     whatever or XDisplaywhatever.  Our apologies for
     the resulting confusion.


2.2.1.	Display Macros

Applications should not directly modify any part of the Dis-
play and Screen structures.  The members should be consid-
ered read-only, although they may change as the result of
other operations on the display.





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Xlib - C Library			    X11, Release 6.4


The following lists the C language macros, their correspond-
ing function equivalents that are for other language bind-
ings, and what data both can return.


__
|
AllPlanes

unsigned long XAllPlanes()

|__

Both return a value with all bits set to 1 suitable for use
in a plane argument to a procedure.


Both BlackPixel and WhitePixel can be used in implementing a
monochrome application.  These pixel values are for perma-
nently allocated entries in the default colormap.  The
actual RGB (red, green, and blue) values are settable on
some screens and, in any case, may not actually be black or
white.	The names are intended to convey the expected rela-
tive intensity of the colors.
__
|
BlackPixel(display, screen_number)

unsigned long XBlackPixel(display, screen_number)
      Display *display;
      int screen_number;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

Both return the black pixel value for the specified screen.
















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Xlib - C Library			    X11, Release 6.4

__
|
WhitePixel(display, screen_number)

unsigned long XWhitePixel(display, screen_number)
      Display *display;
      int screen_number;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

Both return the white pixel value for the specified screen.


__
|
ConnectionNumber(display)

int XConnectionNumber(display)
      Display *display;


display   Specifies the connection to the X server.
|__

Both return a connection number for the specified display.
On a POSIX-conformant system, this is the file descriptor of
the connection.


__
|
DefaultColormap(display, screen_number)

Colormap XDefaultColormap(display, screen_number)
      Display *display;
      int screen_number;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

Both return the default colormap ID for allocation on the
specified screen.  Most routine allocations of color should
be made out of this colormap.




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Xlib - C Library			    X11, Release 6.4

__
|
DefaultDepth(display, screen_number)

int XDefaultDepth(display, screen_number)
      Display *display;
      int screen_number;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

Both return the depth (number of planes) of the default root
window for the specified screen.  Other depths may also be
supported on this screen (see XMatchVisualInfo).


To determine the number of depths that are available on a
given screen, use XListDepths.
__
|
int *XListDepths(display, screen_number, count_return)
      Display *display;
      int screen_number;
      int *count_return;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.

count_return
	  Returns the number of depths.
|__

The XListDepths function returns the array of depths that
are available on the specified screen.	If the specified
screen_number is valid and sufficient memory for the array
can be allocated, XListDepths sets count_return to the num-
ber of available depths.  Otherwise, it does not set
count_return and returns NULL.	To release the memory allo-
cated for the array of depths, use XFree.










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Xlib - C Library			    X11, Release 6.4

__
|
DefaultGC(display, screen_number)

GC XDefaultGC(display, screen_number)
      Display *display;
      int screen_number;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

Both return the default graphics context for the root window
of the specified screen.  This GC is created for the conve-
nience of simple applications and contains the default GC
components with the foreground and background pixel values
initialized to the black and white pixels for the screen,
respectively.  You can modify its contents freely because it
is not used in any Xlib function.  This GC should never be
freed.


__
|
DefaultRootWindow(display)

Window XDefaultRootWindow(display)
      Display *display;


display   Specifies the connection to the X server.
|__

Both return the root window for the default screen.


__
|
DefaultScreenOfDisplay(display)

Screen *XDefaultScreenOfDisplay(display)
      Display *display;


display   Specifies the connection to the X server.
|__

Both return a pointer to the default screen.






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Xlib - C Library			    X11, Release 6.4

__
|
ScreenOfDisplay(display, screen_number)

Screen *XScreenOfDisplay(display, screen_number)
      Display *display;
      int screen_number;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

Both return a pointer to the indicated screen.


__
|
DefaultScreen(display)

int XDefaultScreen(display)
      Display *display;


display   Specifies the connection to the X server.
|__

Both return the default screen number referenced by the
XOpenDisplay function.	This macro or function should be
used to retrieve the screen number in applications that will
use only a single screen.


__
|
DefaultVisual(display, screen_number)

Visual *XDefaultVisual(display, screen_number)
      Display *display;
      int screen_number;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

Both return the default visual type for the specified
screen.  For further information about visual types, see
section 3.1.



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Xlib - C Library			    X11, Release 6.4

__
|
DisplayCells(display, screen_number)

int XDisplayCells(display, screen_number)
      Display *display;
      int screen_number;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

Both return the number of entries in the default colormap.


__
|
DisplayPlanes(display, screen_number)

int XDisplayPlanes(display, screen_number)
      Display *display;
      int screen_number;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

Both return the depth of the root window of the specified
screen.  For an explanation of depth, see the glossary.


__
|
DisplayString(display)

char *XDisplayString(display)
      Display *display;


display   Specifies the connection to the X server.
|__

Both return the string that was passed to XOpenDisplay when
the current display was opened.  On POSIX-conformant sys-
tems, if the passed string was NULL, these return the value
of the DISPLAY environment variable when the current display
was opened.  These are useful to applications that invoke



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Xlib - C Library			    X11, Release 6.4


the fork system call and want to open a new connection to
the same display from the child process as well as for
printing error messages.


__
|
long XExtendedMaxRequestSize(display)
     Display *display;


display   Specifies the connection to the X server.
|__

The XExtendedMaxRequestSize function returns zero if the
specified display does not support an extended-length proto-
col encoding; otherwise, it returns the maximum request size
(in 4-byte units) supported by the server using the
extended-length encoding.  The Xlib functions XDrawLines,
XDrawArcs, XFillPolygon, XChangeProperty, XSetClipRectan-
gles, and XSetRegion will use the extended-length encoding
as necessary, if supported by the server.  Use of the
extended-length encoding in other Xlib functions (for exam-
ple, XDrawPoints, XDrawRectangles, XDrawSegments, XFillArcs,
XFillRectangles, XPutImage) is permitted but not required;
an Xlib implementation may choose to split the data across
multiple smaller requests instead.


__
|
long XMaxRequestSize(display)
     Display *display;


display   Specifies the connection to the X server.
|__

The XMaxRequestSize function returns the maximum request
size (in 4-byte units) supported by the server without using
an extended-length protocol encoding.  Single protocol
requests to the server can be no larger than this size
unless an extended-length protocol encoding is supported by
the server.  The protocol guarantees the size to be no
smaller than 4096 units (16384 bytes).	Xlib automatically
breaks data up into multiple protocol requests as necessary
for the following functions: XDrawPoints, XDrawRectangles,
XDrawSegments, XFillArcs, XFillRectangles, and XPutImage.









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Xlib - C Library			    X11, Release 6.4

__
|
LastKnownRequestProcessed(display)

unsigned long XLastKnownRequestProcessed(display)
     Display *display;


display   Specifies the connection to the X server.
|__

Both extract the full serial number of the last request
known by Xlib to have been processed by the X server.  Xlib
automatically sets this number when replies, events, and
errors are received.


__
|
NextRequest(display)

unsigned long XNextRequest(display)
     Display *display;


display   Specifies the connection to the X server.
|__

Both extract the full serial number that is to be used for
the next request.  Serial numbers are maintained separately
for each display connection.


__
|
ProtocolVersion(display)

int XProtocolVersion(display)
      Display *display;


display   Specifies the connection to the X server.
|__

Both return the major version number (11) of the X protocol
associated with the connected display.












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Xlib - C Library			    X11, Release 6.4

__
|
ProtocolRevision(display)

int XProtocolRevision(display)
      Display *display;


display   Specifies the connection to the X server.
|__

Both return the minor protocol revision number of the X
server.


__
|
QLength(display)

int XQLength(display)
      Display *display;


display   Specifies the connection to the X server.
|__

Both return the length of the event queue for the connected
display.  Note that there may be more events that have not
been read into the queue yet (see XEventsQueued).


__
|
RootWindow(display, screen_number)

Window XRootWindow(display, screen_number)
      Display *display;
      int screen_number;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

Both return the root window.  These are useful with func-
tions that need a drawable of a particular screen and for
creating top-level windows.








			     22





Xlib - C Library			    X11, Release 6.4

__
|
ScreenCount(display)

int XScreenCount(display)
      Display *display;


display   Specifies the connection to the X server.
|__

Both return the number of available screens.


__
|
ServerVendor(display)

char *XServerVendor(display)
      Display *display;


display   Specifies the connection to the X server.
|__

Both return a pointer to a null-terminated string that pro-
vides some identification of the owner of the X server
implementation.  If the data returned by the server is in
the Latin Portable Character Encoding, then the string is in
the Host Portable Character Encoding.  Otherwise, the con-
tents of the string are implementation-dependent.


__
|
VendorRelease(display)

int XVendorRelease(display)
      Display *display;


display   Specifies the connection to the X server.
|__

Both return a number related to a vendor's release of the X
server.

2.2.2.	Image Format Functions and Macros

Applications are required to present data to the X server in
a format that the server demands.  To help simplify applica-
tions, most of the work required to convert the data is pro-
vided by Xlib (see sections 8.7 and 16.8).





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Xlib - C Library			    X11, Release 6.4


The XPixmapFormatValues structure provides an interface to
the pixmap format information that is returned at the time
of a connection setup.	It contains:

__
|
typedef struct {
     int depth;
     int bits_per_pixel;
     int scanline_pad;
} XPixmapFormatValues;

|__


To obtain the pixmap format information for a given display,
use XListPixmapFormats.
__
|
XPixmapFormatValues *XListPixmapFormats(display, count_return)
      Display *display;
      int *count_return;


display   Specifies the connection to the X server.

count_return
	  Returns the number of pixmap formats that are sup-
	  ported by the display.
|__

The XListPixmapFormats function returns an array of XPixmap-
FormatValues structures that describe the types of Z format
images supported by the specified display.  If insufficient
memory is available, XListPixmapFormats returns NULL.  To
free the allocated storage for the XPixmapFormatValues
structures, use XFree.

The following lists the C language macros, their correspond-
ing function equivalents that are for other language bind-
ings, and what data they both return for the specified
server and screen.  These are often used by toolkits as well
as by simple applications.














			     24





Xlib - C Library			    X11, Release 6.4

__
|
ImageByteOrder(display)

int XImageByteOrder(display)
      Display *display;


display   Specifies the connection to the X server.
|__

Both specify the required byte order for images for each
scanline unit in XY format (bitmap) or for each pixel value
in Z format.  The macro or function can return either LSB-
First or MSBFirst.


__
|
BitmapUnit(display)

int XBitmapUnit(display)
      Display *display;


display   Specifies the connection to the X server.
|__

Both return the size of a bitmap's scanline unit in bits.
The scanline is calculated in multiples of this value.


__
|
BitmapBitOrder(display)

int XBitmapBitOrder(display)
      Display *display;


display   Specifies the connection to the X server.
|__

Within each bitmap unit, the left-most bit in the bitmap as
displayed on the screen is either the least significant or
most significant bit in the unit.  This macro or function
can return LSBFirst or MSBFirst.











			     25





Xlib - C Library			    X11, Release 6.4

__
|
BitmapPad(display)

int XBitmapPad(display)
      Display *display;


display   Specifies the connection to the X server.
|__

Each scanline must be padded to a multiple of bits returned
by this macro or function.


__
|
DisplayHeight(display, screen_number)

int XDisplayHeight(display, screen_number)
      Display *display;
      int screen_number;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

Both return an integer that describes the height of the
screen in pixels.


__
|
DisplayHeightMM(display, screen_number)

int XDisplayHeightMM(display, screen_number)
      Display *display;
      int screen_number;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

Both return the height of the specified screen in millime-
ters.





			     26





Xlib - C Library			    X11, Release 6.4

__
|
DisplayWidth(display, screen_number)

int XDisplayWidth(display, screen_number)
      Display *display;
      int screen_number;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

Both return the width of the screen in pixels.


__
|
DisplayWidthMM(display, screen_number)

int XDisplayWidthMM(display, screen_number)
      Display *display;
      int screen_number;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

Both return the width of the specified screen in millime-
ters.

2.2.3.	Screen Information Macros

The following lists the C language macros, their correspond-
ing function equivalents that are for other language bind-
ings, and what data they both can return.  These macros or
functions all take a pointer to the appropriate screen
structure.













			     27





Xlib - C Library			    X11, Release 6.4

__
|
BlackPixelOfScreen(screen)

unsigned long XBlackPixelOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the black pixel value of the specified screen.


__
|
WhitePixelOfScreen(screen)

unsigned long XWhitePixelOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the white pixel value of the specified screen.


__
|
CellsOfScreen(screen)

int XCellsOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the number of colormap cells in the default col-
ormap of the specified screen.


__
|
DefaultColormapOfScreen(screen)

Colormap XDefaultColormapOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the default colormap of the specified screen.



			     28





Xlib - C Library			    X11, Release 6.4

__
|
DefaultDepthOfScreen(screen)

int XDefaultDepthOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the depth of the root window.


__
|
DefaultGCOfScreen(screen)

GC XDefaultGCOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return a default graphics context (GC) of the specified
screen, which has the same depth as the root window of the
screen.  The GC must never be freed.


__
|
DefaultVisualOfScreen(screen)

Visual *XDefaultVisualOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the default visual of the specified screen.  For
information on visual types, see section 3.1.















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Xlib - C Library			    X11, Release 6.4

__
|
DoesBackingStore(screen)

int XDoesBackingStore(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return a value indicating whether the screen supports
backing stores.  The value returned can be one of When-
Mapped, NotUseful, or Always (see section 3.2.4).


__
|
DoesSaveUnders(screen)

Bool XDoesSaveUnders(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return a Boolean value indicating whether the screen
supports save unders.  If True, the screen supports save
unders.  If False, the screen does not support save unders
(see section 3.2.5).


__
|
DisplayOfScreen(screen)

Display *XDisplayOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the display of the specified screen.













			     30





Xlib - C Library			    X11, Release 6.4

__
|
int XScreenNumberOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

The XScreenNumberOfScreen function returns the screen index
number of the specified screen.


__
|
EventMaskOfScreen(screen)

long XEventMaskOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the event mask of the root window for the speci-
fied screen at connection setup time.


__
|
WidthOfScreen(screen)

int XWidthOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the width of the specified screen in pixels.


__
|
HeightOfScreen(screen)

int XHeightOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the height of the specified screen in pixels.




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Xlib - C Library			    X11, Release 6.4

__
|
WidthMMOfScreen(screen)

int XWidthMMOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the width of the specified screen in millime-
ters.


__
|
HeightMMOfScreen(screen)

int XHeightMMOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the height of the specified screen in millime-
ters.


__
|
MaxCmapsOfScreen(screen)

int XMaxCmapsOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the maximum number of installed colormaps sup-
ported by the specified screen (see section 9.3).















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Xlib - C Library			    X11, Release 6.4

__
|
MinCmapsOfScreen(screen)

int XMinCmapsOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the minimum number of installed colormaps sup-
ported by the specified screen (see section 9.3).


__
|
PlanesOfScreen(screen)

int XPlanesOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the depth of the root window.


__
|
RootWindowOfScreen(screen)

Window XRootWindowOfScreen(screen)
      Screen *screen;


screen	  Specifies the appropriate Screen structure.
|__

Both return the root window of the specified screen.

2.3.  Generating a NoOperation Protocol Request

To execute a NoOperation protocol request, use XNoOp.
__
|
XNoOp(display)
      Display *display;


display   Specifies the connection to the X server.
|__

The XNoOp function sends a NoOperation protocol request to



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Xlib - C Library			    X11, Release 6.4


the X server, thereby exercising the connection.

2.4.  Freeing Client-Created Data

To free in-memory data that was created by an Xlib function,
use XFree.
__
|
XFree(data)
     void *data;


data	  Specifies the data that is to be freed.
|__

The XFree function is a general-purpose Xlib routine that
frees the specified data.  You must use it to free any
objects that were allocated by Xlib, unless an alternate
function is explicitly specified for the object.  A NULL
pointer cannot be passed to this function.

2.5.  Closing the Display

To close a display or disconnect from the X server, use
XCloseDisplay.

__
|
XCloseDisplay(display)
      Display *display;


display   Specifies the connection to the X server.
|__

The XCloseDisplay function closes the connection to the X
server for the display specified in the Display structure
and destroys all windows, resource IDs (Window, Font,
Pixmap, Colormap, Cursor, and GContext), or other resources
that the client has created on this display, unless the
close-down mode of the resource has been changed (see XSet-
CloseDownMode).  Therefore, these windows, resource IDs, and
other resources should never be referenced again or an error
will be generated.  Before exiting, you should call
XCloseDisplay explicitly so that any pending errors are
reported as XCloseDisplay performs a final XSync operation.

XCloseDisplay can generate a BadGC error.


Xlib provides a function to permit the resources owned by a
client to survive after the client's connection is closed.
To change a client's close-down mode, use XSetCloseDownMode.




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Xlib - C Library			    X11, Release 6.4

__
|
XSetCloseDownMode(display, close_mode)
      Display *display;
      int close_mode;


display   Specifies the connection to the X server.

close_mode
	  Specifies the client close-down mode.  You can
	  pass DestroyAll, RetainPermanent, or RetainTempo-
	  rary.
|__

The XSetCloseDownMode defines what will happen to the
client's resources at connection close.  A connection starts
in DestroyAll mode.  For information on what happens to the
client's resources when the close_mode argument is Retain-
Permanent or RetainTemporary, see section 2.6.

XSetCloseDownMode can generate a BadValue error.

2.6.  Using X Server Connection Close Operations

When the X server's connection to a client is closed either
by an explicit call to XCloseDisplay or by a process that
exits, the X server performs the following automatic opera-
tions:

o    It disowns all selections owned by the client (see
     XSetSelectionOwner).

o    It performs an XUngrabPointer and XUngrabKeyboard if
     the client has actively grabbed the pointer or the key-
     board.

o    It performs an XUngrabServer if the client has grabbed
     the server.

o    It releases all passive grabs made by the client.

o    It marks all resources (including colormap entries)
     allocated by the client either as permanent or tempo-
     rary, depending on whether the close-down mode is
     RetainPermanent or RetainTemporary.  However, this does
     not prevent other client applications from explicitly
     destroying the resources (see XSetCloseDownMode).

When the close-down mode is DestroyAll, the X server
destroys all of a client's resources as follows:

o    It examines each window in the client's save-set to
     determine if it is an inferior (subwindow) of a window
     created by the client.  (The save-set is a list of



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Xlib - C Library			    X11, Release 6.4


     other clients' windows that are referred to as save-set
     windows.)	If so, the X server reparents the save-set
     window to the closest ancestor so that the save-set
     window is not an inferior of a window created by the
     client.  The reparenting leaves unchanged the absolute
     coordinates (with respect to the root window) of the
     upper-left outer corner of the save-set window.

o    It performs a MapWindow request on the save-set window
     if the save-set window is unmapped.  The X server does
     this even if the save-set window was not an inferior of
     a window created by the client.

o    It destroys all windows created by the client.

o    It performs the appropriate free request on each non-
     window resource created by the client in the server
     (for example, Font, Pixmap, Cursor, Colormap, and GCon-
     text).

o    It frees all colors and colormap entries allocated by a
     client application.

Additional processing occurs when the last connection to the
X server closes.  An X server goes through a cycle of having
no connections and having some connections.  When the last
connection to the X server closes as a result of a connec-
tion closing with the close_mode of DestroyAll, the X server
does the following:

o    It resets its state as if it had just been started.
     The X server begins by destroying all lingering
     resources from clients that have terminated in Retain-
     Permanent or RetainTemporary mode.

o    It deletes all but the predefined atom identifiers.

o    It deletes all properties on all root windows (see sec-
     tion 4.3).

o    It resets all device maps and attributes (for example,
     key click, bell volume, and acceleration) as well as
     the access control list.

o    It restores the standard root tiles and cursors.

o    It restores the default font path.

o    It restores the input focus to state PointerRoot.

However, the X server does not reset if you close a connec-
tion with a close-down mode set to RetainPermanent or
RetainTemporary.




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Xlib - C Library			    X11, Release 6.4


2.7.  Using Xlib with Threads

On systems that have threads, support may be provided to
permit multiple threads to use Xlib concurrently.


To initialize support for concurrent threads, use XInit-
Threads.
__
|
Status XInitThreads();

|__

The XInitThreads function initializes Xlib support for con-
current threads.  This function must be the first Xlib func-
tion a multi-threaded program calls, and it must complete
before any other Xlib call is made.  This function returns a
nonzero status if initialization was successful; otherwise,
it returns zero.  On systems that do not support threads,
this function always returns zero.

It is only necessary to call this function if multiple
threads might use Xlib concurrently.  If all calls to Xlib
functions are protected by some other access mechanism (for
example, a mutual exclusion lock in a toolkit or through
explicit client programming), Xlib thread initialization is
not required.  It is recommended that single-threaded pro-
grams not call this function.



To lock a display across several Xlib calls, use XLockDis-
play.
__
|
void XLockDisplay(display)
      Display *display;


display   Specifies the connection to the X server.
|__

The XLockDisplay function locks out all other threads from
using the specified display.  Other threads attempting to
use the display will block until the display is unlocked by
this thread.  Nested calls to XLockDisplay work correctly;
the display will not actually be unlocked until XUnlockDis-
play has been called the same number of times as XLockDis-
play.  This function has no effect unless Xlib was success-
fully initialized for threads using XInitThreads.


To unlock a display, use XUnlockDisplay.



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Xlib - C Library			    X11, Release 6.4

__
|
void XUnlockDisplay(display)
      Display *display;


display   Specifies the connection to the X server.
|__

The XUnlockDisplay function allows other threads to use the
specified display again.  Any threads that have blocked on
the display are allowed to continue.  Nested locking works
correctly; if XLockDisplay has been called multiple times by
a thread, then XUnlockDisplay must be called an equal number
of times before the display is actually unlocked.  This
function has no effect unless Xlib was successfully initial-
ized for threads using XInitThreads.

2.8.  Using Internal Connections

In addition to the connection to the X server, an Xlib
implementation may require connections to other kinds of
servers (for example, to input method servers as described
in chapter 13).  Toolkits and clients that use multiple dis-
plays, or that use displays in combination with other
inputs, need to obtain these additional connections to cor-
rectly block until input is available and need to process
that input when it is available.  Simple clients that use a
single display and block for input in an Xlib event function
do not need to use these facilities.

To track internal connections for a display, use XAddConnec-
tionWatch.

























			     38





Xlib - C Library			    X11, Release 6.4

__
|
typedef void (*XConnectionWatchProc)(display, client_data, fd, opening, watch_data)
      Display *display;
      XPointer client_data;
      int fd;
      Bool opening;
      XPointer *watch_data;

Status XAddConnectionWatch(display, procedure, client_data)
      Display *display;
      XWatchProc procedure;
      XPointer client_data;


display   Specifies the connection to the X server.

procedure Specifies the procedure to be called.

client_data
	  Specifies the additional client data.
|__

The XAddConnectionWatch function registers a procedure to be
called each time Xlib opens or closes an internal connection
for the specified display.  The procedure is passed the dis-
play, the specified client_data, the file descriptor for the
connection, a Boolean indicating whether the connection is
being opened or closed, and a pointer to a location for pri-
vate watch data.  If opening is True, the procedure can
store a pointer to private data in the location pointed to
by watch_data; when the procedure is later called for this
same connection and opening is False, the location pointed
to by watch_data will hold this same private data pointer.

This function can be called at any time after a display is
opened.  If internal connections already exist, the regis-
tered procedure will immediately be called for each of them,
before XAddConnectionWatch returns.  XAddConnectionWatch
returns a nonzero status if the procedure is successfully
registered; otherwise, it returns zero.

The registered procedure should not call any Xlib functions.
If the procedure directly or indirectly causes the state of
internal connections or watch procedures to change, the
result is not defined.	If Xlib has been initialized for
threads, the procedure is called with the display locked and
the result of a call by the procedure to any Xlib function
that locks the display is not defined unless the executing
thread has externally locked the display using XLockDisplay.


To stop tracking internal connections for a display, use
XRemoveConnectionWatch.




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Xlib - C Library			    X11, Release 6.4

__
|
Status XRemoveConnectionWatch(display, procedure, client_data)
      Display *display;
      XWatchProc procedure;
      XPointer client_data;


display   Specifies the connection to the X server.

procedure Specifies the procedure to be called.

client_data
	  Specifies the additional client data.
|__

The XRemoveConnectionWatch function removes a previously
registered connection watch procedure.	The client_data must
match the client_data used when the procedure was initially
registered.



To process input on an internal connection, use XProcessIn-
ternalConnection.
__
|
void XProcessInternalConnection(display, fd)
      Display *display;
      int fd;


display   Specifies the connection to the X server.

fd	  Specifies the file descriptor.
|__

The XProcessInternalConnection function processes input
available on an internal connection.  This function should
be called for an internal connection only after an operating
system facility (for example, select or poll) has indicated
that input is available; otherwise, the effect is not
defined.


To obtain all of the current internal connections for a dis-
play, use XInternalConnectionNumbers.











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Xlib - C Library			    X11, Release 6.4

__
|
Status XInternalConnectionNumbers(display, fd_return, count_return)
      Display *display;
      int **fd_return;
      int *count_return;


display   Specifies the connection to the X server.

fd_return Returns the file descriptors.

count_return
	  Returns the number of file descriptors.
|__

The XInternalConnectionNumbers function returns a list of
the file descriptors for all internal connections currently
open for the specified display.  When the allocated list is
no longer needed, free it by using XFree.  This functions
returns a nonzero status if the list is successfully allo-
cated; otherwise, it returns zero.




































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Xlib - C Library			    X11, Release 6.4




			 Chapter 3

		      Window Functions



In the X Window System, a window is a rectangular area on
the screen that lets you view graphic output.  Client appli-
cations can display overlapping and nested windows on one or
more screens that are driven by X servers on one or more
machines.  Clients who want to create windows must first
connect their program to the X server by calling XOpenDis-
play.  This chapter begins with a discussion of visual types
and window attributes.	The chapter continues with a discus-
sion of the Xlib functions you can use to:

o    Create windows

o    Destroy windows

o    Map windows

o    Unmap windows

o    Configure windows

o    Change window stacking order

o    Change window attributes

This chapter also identifies the window actions that may
generate events.

Note that it is vital that your application conform to the
established conventions for communicating with window man-
agers for it to work well with the various window managers
in use (see section 14.1).  Toolkits generally adhere to
these conventions for you, relieving you of the burden.
Toolkits also often supersede many functions in this chapter
with versions of their own.  For more information, refer to
the documentation for the toolkit that you are using.

3.1.  Visual Types

On some display hardware, it may be possible to deal with
color resources in more than one way.  For example, you may
be able to deal with a screen of either 12-bit depth with
arbitrary mapping of pixel to color (pseudo-color) or 24-bit
depth with 8 bits of the pixel dedicated to each of red,
green, and blue.  These different ways of dealing with the
visual aspects of the screen are called visuals.  For each
screen of the display, there may be a list of valid visual



			     42





Xlib - C Library			    X11, Release 6.4


types supported at different depths of the screen.  Because
default windows and visual types are defined for each
screen, most simple applications need not deal with this
complexity.  Xlib provides macros and functions that return
the default root window, the default depth of the default
root window, and the default visual type (see sections 2.2.1
and 16.7).

Xlib uses an opaque Visual structure that contains informa-
tion about the possible color mapping.	The visual utility
functions (see section 16.7) use an XVisualInfo structure to
return this information to an application.  The members of
this structure pertinent to this discussion are class,
red_mask, green_mask, blue_mask, bits_per_rgb, and col-
ormap_size.  The class member specifies one of the possible
visual classes of the screen and can be StaticGray, Static-
Color, TrueColor, GrayScale, PseudoColor, or DirectColor.

The following concepts may serve to make the explanation of
visual types clearer.  The screen can be color or grayscale,
can have a colormap that is writable or read-only, and can
also have a colormap whose indices are decomposed into sepa-
rate RGB pieces, provided one is not on a grayscale screen.
This leads to the following diagram:



			     Color	    Gray-scale
			 R/O	  R/W	   R/O	    R/W
	+-------------+--------+--------+--------+-------+
	|Undecomposed | Static | Pseudo | Static | Gray  |
	|  Colormap   | Color  | Color	|  Gray  | Scale |
	+-------------+--------+--------+--------+-------+
	| Decomposed  |  True  | Direct |
	|  Colormap   | Color  | Color	|
	+-------------+--------+--------+



Conceptually, as each pixel is read out of video memory for
display on the screen, it goes through a look-up stage by
indexing into a colormap.  Colormaps can be manipulated
arbitrarily on some hardware, in limited ways on other hard-
ware, and not at all on other hardware.  The visual types
affect the colormap and the RGB values in the following
ways:


o    For PseudoColor, a pixel value indexes a colormap to
     produce independent RGB values, and the RGB values can
     be changed dynamically.

o    GrayScale is treated the same way as PseudoColor except
     that the primary that drives the screen is undefined.



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Xlib - C Library			    X11, Release 6.4


     Thus, the client should always store the same value for
     red, green, and blue in the colormaps.

o    For DirectColor, a pixel value is decomposed into sepa-
     rate RGB subfields, and each subfield separately
     indexes the colormap for the corresponding value.	The
     RGB values can be changed dynamically.

o    TrueColor is treated the same way as DirectColor except
     that the colormap has predefined, read-only RGB values.
     These RGB values are server dependent but provide lin-
     ear or near-linear ramps in each primary.

o    StaticColor is treated the same way as PseudoColor
     except that the colormap has predefined, read-only,
     server-dependent RGB values.

o    StaticGray is treated the same way as StaticColor
     except that the RGB values are equal for any single
     pixel value, thus resulting in shades of gray.  Stat-
     icGray with a two-entry colormap can be thought of as
     monochrome.

The red_mask, green_mask, and blue_mask members are only
defined for DirectColor and TrueColor.	Each has one con-
tiguous set of bits with no intersections.  The bits_per_rgb
member specifies the log base 2 of the number of distinct
color values (individually) of red, green, and blue.  Actual
RGB values are unsigned 16-bit numbers.  The colormap_size
member defines the number of available colormap entries in a
newly created colormap.  For DirectColor and TrueColor, this
is the size of an individual pixel subfield.


To obtain the visual ID from a Visual, use XVisualIDFromVi-
sual.
__
|
VisualID XVisualIDFromVisual(visual)
       Visual *visual;


visual	  Specifies the visual type.
|__

The XVisualIDFromVisual function returns the visual ID for
the specified visual type.

3.2.  Window Attributes

All InputOutput windows have a border width of zero or more
pixels, an optional background, an event suppression mask
(which suppresses propagation of events from children), and
a property list (see section 4.3).  The window border and



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Xlib - C Library			    X11, Release 6.4


background can be a solid color or a pattern, called a tile.
All windows except the root have a parent and are clipped by
their parent.  If a window is stacked on top of another win-
dow, it obscures that other window for the purpose of input.
If a window has a background (almost all do), it obscures
the other window for purposes of output.  Attempts to output
to the obscured area do nothing, and no input events (for
example, pointer motion) are generated for the obscured
area.

Windows also have associated property lists (see section
4.3).

Both InputOutput and InputOnly windows have the following
common attributes, which are the only attributes of an Inpu-
tOnly window:

o    win-gravity

o    event-mask

o    do-not-propagate-mask

o    override-redirect

o    cursor

If you specify any other attributes for an InputOnly window,
a BadMatch error results.

InputOnly windows are used for controlling input events in
situations where InputOutput windows are unnecessary.  Inpu-
tOnly windows are invisible; can only be used to control
such things as cursors, input event generation, and grab-
bing; and cannot be used in any graphics requests.  Note
that InputOnly windows cannot have InputOutput windows as
inferiors.

Windows have borders of a programmable width and pattern as
well as a background pattern or tile.  Pixel values can be
used for solid colors.	The background and border pixmaps
can be destroyed immediately after creating the window if no
further explicit references to them are to be made.  The
pattern can either be relative to the parent or absolute.
If ParentRelative, the parent's background is used.

When windows are first created, they are not visible (not
mapped) on the screen.	Any output to a window that is not
visible on the screen and that does not have backing store
will be discarded.  An application may wish to create a win-
dow long before it is mapped to the screen.  When a window
is eventually mapped to the screen (using XMapWindow), the X
server generates an Expose event for the window if backing
store has not been maintained.



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Xlib - C Library			    X11, Release 6.4


A window manager can override your choice of size, border
width, and position for a top-level window.  Your program
must be prepared to use the actual size and position of the
top window.  It is not acceptable for a client application
to resize itself unless in direct response to a human com-
mand to do so.	Instead, either your program should use the
space given to it, or if the space is too small for any use-
ful work, your program might ask the user to resize the win-
dow.  The border of your top-level window is considered fair
game for window managers.

To set an attribute of a window, set the appropriate member
of the XSetWindowAttributes structure and OR in the corre-
sponding value bitmask in your subsequent calls to XCre-
ateWindow and XChangeWindowAttributes, or use one of the
other convenience functions that set the appropriate
attribute.  The symbols for the value mask bits and the
XSetWindowAttributes structure are:







































			     46





Xlib - C Library			    X11, Release 6.4

__
|
/* Window attribute value mask bits */

#define   CWBackPixmap		      (1L<<0)
#define   CWBackPixel		      (1L<<1)
#define   CWBorderPixmap	      (1L<<2)
#define   CWBorderPixel 	      (1L<<3)
#define   CWBitGravity		      (1L<<4)
#define   CWWinGravity		      (1L<<5)
#define   CWBackingStore	      (1L<<6)
#define   CWBackingPlanes	      (1L<<7)
#define   CWBackingPixel	      (1L<<8)
#define   CWOverrideRedirect	      (1L<<9)
#define   CWSaveUnder		      (1L<<10)
#define   CWEventMask		      (1L<<11)
#define   CWDontPropagate	      (1L<<12)
#define   CWColormap		      (1L<<13)
#define   CWCursor		      (1L<<14)


/* Values */

typedef struct {
     Pixmap background_pixmap;/* background, None, or ParentRelative */
     unsigned long background_pixel;/* background pixel */
     Pixmap border_pixmap;    /* border of the window or CopyFromParent */
     unsigned long border_pixel;/* border pixel value */
     int bit_gravity;	      /* one of bit gravity values */
     int win_gravity;	      /* one of the window gravity values */
     int backing_store;       /* NotUseful, WhenMapped, Always */
     unsigned long backing_planes;/* planes to be preserved if possible */
     unsigned long backing_pixel;/* value to use in restoring planes */
     Bool save_under;	      /* should bits under be saved? (popups) */
     long event_mask;	      /* set of events that should be saved */
     long do_not_propagate_mask;/* set of events that should not propagate */
     Bool override_redirect;  /* boolean value for override_redirect */
     Colormap colormap;       /* color map to be associated with window */
     Cursor cursor;	      /* cursor to be displayed (or None) */
} XSetWindowAttributes;

|__

The following lists the defaults for each window attribute
and indicates whether the attribute is applicable to
InputOutput and InputOnly windows:

-------------------------------------------------------------
Attribute		Default 	InputOut-   Inpu-
					put	    tOnly
-------------------------------------------------------------
background-pixmap	None		   Yes	       No
background-pixel	Undefined	   Yes	       No





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Xlib - C Library			    X11, Release 6.4


-------------------------------------------------------------
Attribute		Default 	InputOut-   Inpu-
					put	    tOnly
-------------------------------------------------------------
border-pixmap		CopyFromPar-	   Yes	       No
			ent
border-pixel		Undefined	   Yes	       No
bit-gravity		ForgetGravity	   Yes	       No
win-gravity		NorthWest-	   Yes	      Yes
			Gravity
backing-store		NotUseful	   Yes	       No
backing-planes		All ones	   Yes	       No
backing-pixel		zero		   Yes	       No
save-under		False		   Yes	       No
event-mask		empty set	   Yes	      Yes
do-not-propagate-mask	empty set	   Yes	      Yes
override-redirect	False		   Yes	      Yes
colormap		CopyFromPar-	   Yes	       No
			ent
cursor			None		   Yes	      Yes
-------------------------------------------------------------


3.2.1.	Background Attribute

Only InputOutput windows can have a background.  You can set
the background of an InputOutput window by using a pixel or
a pixmap.

The background-pixmap attribute of a window specifies the
pixmap to be used for a window's background.  This pixmap
can be of any size, although some sizes may be faster than
others.  The background-pixel attribute of a window speci-
fies a pixel value used to paint a window's background in a
single color.

You can set the background-pixmap to a pixmap, None
(default), or ParentRelative.  You can set the background-
pixel of a window to any pixel value (no default).  If you
specify a background-pixel, it overrides either the default
background-pixmap or any value you may have set in the back-
ground-pixmap.	A pixmap of an undefined size that is filled
with the background-pixel is used for the background.  Range
checking is not performed on the background pixel; it simply
is truncated to the appropriate number of bits.

If you set the background-pixmap, it overrides the default.
The background-pixmap and the window must have the same
depth, or a BadMatch error results.  If you set background-
pixmap to None, the window has no defined background.  If
you set the background-pixmap to ParentRelative:

o    The parent window's background-pixmap is used.  The
     child window, however, must have the same depth as its



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Xlib - C Library			    X11, Release 6.4


     parent, or a BadMatch error results.

o    If the parent window has a background-pixmap of None,
     the window also has a background-pixmap of None.

o    A copy of the parent window's background-pixmap is not
     made.  The parent's background-pixmap is examined each
     time the child window's background-pixmap is required.

o    The background tile origin always aligns with the par-
     ent window's background tile origin.  If the back-
     ground-pixmap is not ParentRelative, the background
     tile origin is the child window's origin.

Setting a new background, whether by setting background-
pixmap or background-pixel, overrides any previous back-
ground.  The background-pixmap can be freed immediately if
no further explicit reference is made to it (the X server
will keep a copy to use when needed).  If you later draw
into the pixmap used for the background, what happens is
undefined because the X implementation is free to make a
copy of the pixmap or to use the same pixmap.

When no valid contents are available for regions of a window
and either the regions are visible or the server is main-
taining backing store, the server automatically tiles the
regions with the window's background unless the window has a
background of None.  If the background is None, the previous
screen contents from other windows of the same depth as the
window are simply left in place as long as the contents come
from the parent of the window or an inferior of the parent.
Otherwise, the initial contents of the exposed regions are
undefined.  Expose events are then generated for the
regions, even if the background-pixmap is None (see section
10.9).

3.2.2.	Border Attribute

Only InputOutput windows can have a border.  You can set the
border of an InputOutput window by using a pixel or a
pixmap.

The border-pixmap attribute of a window specifies the pixmap
to be used for a window's border.  The border-pixel
attribute of a window specifies a pixmap of undefined size
filled with that pixel be used for a window's border.  Range
checking is not performed on the background pixel; it simply
is truncated to the appropriate number of bits.  The border
tile origin is always the same as the background tile ori-
gin.

You can also set the border-pixmap to a pixmap of any size
(some may be faster than others) or to CopyFromParent
(default).  You can set the border-pixel to any pixel value



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(no default).

If you set a border-pixmap, it overrides the default.  The
border-pixmap and the window must have the same depth, or a
BadMatch error results.  If you set the border-pixmap to
CopyFromParent, the parent window's border-pixmap is copied.
Subsequent changes to the parent window's border attribute
do not affect the child window.  However, the child window
must have the same depth as the parent window, or a BadMatch
error results.

The border-pixmap can be freed immediately if no further
explicit reference is made to it.  If you later draw into
the pixmap used for the border, what happens is undefined
because the X implementation is free either to make a copy
of the pixmap or to use the same pixmap.  If you specify a
border-pixel, it overrides either the default border-pixmap
or any value you may have set in the border-pixmap.  All
pixels in the window's border will be set to the border-
pixel.	Setting a new border, whether by setting border-
pixel or by setting border-pixmap, overrides any previous
border.

Output to a window is always clipped to the inside of the
window.  Therefore, graphics operations never affect the
window border.

3.2.3.	Gravity Attributes

The bit gravity of a window defines which region of the win-
dow should be retained when an InputOutput window is
resized.  The default value for the bit-gravity attribute is
ForgetGravity.	The window gravity of a window allows you to
define how the InputOutput or InputOnly window should be
repositioned if its parent is resized.	The default value
for the win-gravity attribute is NorthWestGravity.

If the inside width or height of a window is not changed and
if the window is moved or its border is changed, then the
contents of the window are not lost but move with the win-
dow.  Changing the inside width or height of the window
causes its contents to be moved or lost (depending on the
bit-gravity of the window) and causes children to be recon-
figured (depending on their win-gravity).  For a change of
width and height, the (x, y) pairs are defined:


----------------------------------------
Gravity Direction   Coordinates
----------------------------------------
NorthWestGravity    (0, 0)
NorthGravity	    (Width/2, 0)
NorthEastGravity    (Width, 0)




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WestGravity	    (0, Height/2)
CenterGravity	    (Width/2, Height/2)
EastGravity	    (Width, Height/2)
SouthWestGravity    (0, Height)
SouthGravity	    (Width/2, Height)
SouthEastGravity    (Width, Height)
----------------------------------------


When a window with one of these bit-gravity values is
resized, the corresponding pair defines the change in posi-
tion of each pixel in the window.  When a window with one of
these win-gravities has its parent window resized, the cor-
responding pair defines the change in position of the window
within the parent.  When a window is so repositioned, a
GravityNotify event is generated (see section 10.10.5).

A bit-gravity of StaticGravity indicates that the contents
or origin should not move relative to the origin of the root
window.  If the change in size of the window is coupled with
a change in position (x, y), then for bit-gravity the change
in position of each pixel is (-x, -y), and for win-gravity
the change in position of a child when its parent is so
resized is (-x, -y).  Note that StaticGravity still only
takes effect when the width or height of the window is
changed, not when the window is moved.

A bit-gravity of ForgetGravity indicates that the window's
contents are always discarded after a size change, even if a
backing store or save under has been requested.  The window
is tiled with its background and zero or more Expose events
are generated.	If no background is defined, the existing
screen contents are not altered.  Some X servers may also
ignore the specified bit-gravity and always generate Expose
events.

The contents and borders of inferiors are not affected by
their parent's bit-gravity.  A server is permitted to ignore
the specified bit-gravity and use Forget instead.

A win-gravity of UnmapGravity is like NorthWestGravity (the
window is not moved), except the child is also unmapped when
the parent is resized, and an UnmapNotify event is gener-
ated.

3.2.4.	Backing Store Attribute

Some implementations of the X server may choose to maintain
the contents of InputOutput windows.  If the X server main-
tains the contents of a window, the off-screen saved pixels
are known as backing store.  The backing store advises the X
server on what to do with the contents of a window.  The
backing-store attribute can be set to NotUseful (default),
WhenMapped, or Always.



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A backing-store attribute of NotUseful advises the X server
that maintaining contents is unnecessary, although some X
implementations may still choose to maintain contents and,
therefore, not generate Expose events.	A backing-store
attribute of WhenMapped advises the X server that maintain-
ing contents of obscured regions when the window is mapped
would be beneficial.  In this case, the server may generate
an Expose event when the window is created.  A backing-store
attribute of Always advises the X server that maintaining
contents even when the window is unmapped would be benefi-
cial.  Even if the window is larger than its parent, this is
a request to the X server to maintain complete contents, not
just the region within the parent window boundaries.  While
the X server maintains the window's contents, Expose events
normally are not generated, but the X server may stop main-
taining contents at any time.

When the contents of obscured regions of a window are being
maintained, regions obscured by noninferior windows are
included in the destination of graphics requests (and
source, when the window is the source).  However, regions
obscured by inferior windows are not included.

3.2.5.	Save Under Flag

Some server implementations may preserve contents of
InputOutput windows under other InputOutput windows.  This
is not the same as preserving the contents of a window for
you.  You may get better visual appeal if transient windows
(for example, pop-up menus) request that the system preserve
the screen contents under them, so the temporarily obscured
applications do not have to repaint.

You can set the save-under flag to True or False (default).
If save-under is True, the X server is advised that, when
this window is mapped, saving the contents of windows it
obscures would be beneficial.

3.2.6.	Backing Planes and Backing Pixel Attributes

You can set backing planes to indicate (with bits set to 1)
which bit planes of an InputOutput window hold dynamic data
that must be preserved in backing store and during save
unders.  The default value for the backing-planes attribute
is all bits set to 1.  You can set backing pixel to specify
what bits to use in planes not covered by backing planes.
The default value for the backing-pixel attribute is all
bits set to 0.	The X server is free to save only the speci-
fied bit planes in the backing store or the save under and
is free to regenerate the remaining planes with the speci-
fied pixel value.  Any extraneous bits in these values (that
is, those bits beyond the specified depth of the window) may
be simply ignored.  If you request backing store or save
unders, you should use these members to minimize the amount



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of off-screen memory required to store your window.

3.2.7.	Event Mask and Do Not Propagate Mask Attributes

The event mask defines which events the client is interested
in for this InputOutput or InputOnly window (or, for some
event types, inferiors of this window).  The event mask is
the bitwise inclusive OR of zero or more of the valid event
mask bits.  You can specify that no maskable events are
reported by setting NoEventMask (default).

The do-not-propagate-mask attribute defines which events
should not be propagated to ancestor windows when no client
has the event type selected in this InputOutput or InputOnly
window.  The do-not-propagate-mask is the bitwise inclusive
OR of zero or more of the following masks: KeyPress, KeyRe-
lease, ButtonPress, ButtonRelease, PointerMotion, But-
ton1Motion, Button2Motion, Button3Motion, Button4Motion,
Button5Motion, and ButtonMotion.  You can specify that all
events are propagated by setting NoEventMask (default).

3.2.8.	Override Redirect Flag

To control window placement or to add decoration, a window
manager often needs to intercept (redirect) any map or con-
figure request.  Pop-up windows, however, often need to be
mapped without a window manager getting in the way.  To con-
trol whether an InputOutput or InputOnly window is to ignore
these structure control facilities, use the override-redi-
rect flag.

The override-redirect flag specifies whether map and config-
ure requests on this window should override a Substructur-
eRedirectMask on the parent.  You can set the override-redi-
rect flag to True or False (default).  Window managers use
this information to avoid tampering with pop-up windows (see
also chapter 14).

3.2.9.	Colormap Attribute

The colormap attribute specifies which colormap best
reflects the true colors of the InputOutput window.  The
colormap must have the same visual type as the window, or a
BadMatch error results.  X servers capable of supporting
multiple hardware colormaps can use this information, and
window managers can use it for calls to XInstallColormap.
You can set the colormap attribute to a colormap or to Copy-
FromParent (default).

If you set the colormap to CopyFromParent, the parent win-
dow's colormap is copied and used by its child.  However,
the child window must have the same visual type as the par-
ent, or a BadMatch error results.  The parent window must
not have a colormap of None, or a BadMatch error results.



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The colormap is copied by sharing the colormap object
between the child and parent, not by making a complete copy
of the colormap contents.  Subsequent changes to the parent
window's colormap attribute do not affect the child window.

3.2.10.  Cursor Attribute

The cursor attribute specifies which cursor is to be used
when the pointer is in the InputOutput or InputOnly window.
You can set the cursor to a cursor or None (default).

If you set the cursor to None, the parent's cursor is used
when the pointer is in the InputOutput or InputOnly window,
and any change in the parent's cursor will cause an immedi-
ate change in the displayed cursor.  By calling XFreeCursor,
the cursor can be freed immediately as long as no further
explicit reference to it is made.

3.3.  Creating Windows

Xlib provides basic ways for creating windows, and toolkits
often supply higher-level functions specifically for creat-
ing and placing top-level windows, which are discussed in
the appropriate toolkit documentation.	If you do not use a
toolkit, however, you must provide some standard information
or hints for the window manager by using the Xlib inter-
client communication functions (see chapter 14).

If you use Xlib to create your own top-level windows (direct
children of the root window), you must observe the following
rules so that all applications interact reasonably across
the different styles of window management:

o    You must never fight with the window manager for the
     size or placement of your top-level window.

o    You must be able to deal with whatever size window you
     get, even if this means that your application just
     prints a message like ``Please make me bigger'' in its
     window.

o    You should only attempt to resize or move top-level
     windows in direct response to a user request.  If a
     request to change the size of a top-level window fails,
     you must be prepared to live with what you get.  You
     are free to resize or move the children of top-level
     windows as necessary.  (Toolkits often have facilities
     for automatic relayout.)

o    If you do not use a toolkit that automatically sets
     standard window properties, you should set these prop-
     erties for top-level windows before mapping them.





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For further information, see chapter 14 and the Inter-Client
Communication Conventions Manual.

XCreateWindow is the more general function that allows you
to set specific window attributes when you create a window.
XCreateSimpleWindow creates a window that inherits its
attributes from its parent window.

The X server acts as if InputOnly windows do not exist for
the purposes of graphics requests, exposure processing, and
VisibilityNotify events.  An InputOnly window cannot be used
as a drawable (that is, as a source or destination for
graphics requests).  InputOnly and InputOutput windows act
identically in other respects (properties, grabs, input con-
trol, and so on).  Extension packages can define other
classes of windows.

To create an unmapped window and set its window attributes,
use XCreateWindow.






































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Xlib - C Library			    X11, Release 6.4

__
|
Window XCreateWindow(display, parent, x, y, width, height, border_width, depth,
		       class, visual, valuemask, attributes)
      Display *display;
      Window parent;
      int x, y;
      unsigned int width, height;
      unsigned int border_width;
      int depth;
      unsigned int class;
      Visual *visual;
      unsigned long valuemask;
      XSetWindowAttributes *attributes;


display   Specifies the connection to the X server.

parent	  Specifies the parent window.

x
y	  Specify the x and y coordinates, which are the
	  top-left outside corner of the created window's
	  borders and are relative to the inside of the par-
	  ent window's borders.

width
height	  Specify the width and height, which are the cre-
	  ated window's inside dimensions and do not include
	  the created window's borders.  The dimensions must
	  be nonzero, or a BadValue error results.

border_width
	  Specifies the width of the created window's border
	  in pixels.

depth	  Specifies the window's depth.  A depth of Copy-
	  FromParent means the depth is taken from the par-
	  ent.

class	  Specifies the created window's class.  You can
	  pass InputOutput, InputOnly, or CopyFromParent.  A
	  class of CopyFromParent means the class is taken
	  from the parent.

visual	  Specifies the visual type.  A visual of Copy-
	  FromParent means the visual type is taken from the
	  parent.

valuemask Specifies which window attributes are defined in
	  the attributes argument.  This mask is the bitwise
	  inclusive OR of the valid attribute mask bits.  If
	  valuemask is zero, the attributes are ignored and
	  are not referenced.




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attributes
	  Specifies the structure from which the values (as
	  specified by the value mask) are to be taken.  The
	  value mask should have the appropriate bits set to
	  indicate which attributes have been set in the
	  structure.
|__

The XCreateWindow function creates an unmapped subwindow for
a specified parent window, returns the window ID of the cre-
ated window, and causes the X server to generate a CreateNo-
tify event.  The created window is placed on top in the
stacking order with respect to siblings.

The coordinate system has the X axis horizontal and the Y
axis vertical with the origin [0, 0] at the upper-left cor-
ner.  Coordinates are integral, in terms of pixels, and
coincide with pixel centers.  Each window and pixmap has its
own coordinate system.	For a window, the origin is inside
the border at the inside, upper-left corner.

The border_width for an InputOnly window must be zero, or a
BadMatch error results.  For class InputOutput, the visual
type and depth must be a combination supported for the
screen, or a BadMatch error results.  The depth need not be
the same as the parent, but the parent must not be a window
of class InputOnly, or a BadMatch error results.  For an
InputOnly window, the depth must be zero, and the visual
must be one supported by the screen.  If either condition is
not met, a BadMatch error results.  The parent window, how-
ever, may have any depth and class.  If you specify any
invalid window attribute for a window, a BadMatch error
results.

The created window is not yet displayed (mapped) on the
user's display.  To display the window, call XMapWindow.
The new window initially uses the same cursor as its parent.
A new cursor can be defined for the new window by calling
XDefineCursor.	The window will not be visible on the screen
unless it and all of its ancestors are mapped and it is not
obscured by any of its ancestors.

XCreateWindow can generate BadAlloc, BadColor, BadCursor,
BadMatch, BadPixmap, BadValue, and BadWindow errors.


To create an unmapped InputOutput subwindow of a given par-
ent window, use XCreateSimpleWindow.









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__
|
Window XCreateSimpleWindow(display, parent, x, y, width, height, border_width,
			     border, background)
      Display *display;
      Window parent;
      int x, y;
      unsigned int width, height;
      unsigned int border_width;
      unsigned long border;
      unsigned long background;


display   Specifies the connection to the X server.

parent	  Specifies the parent window.

x
y	  Specify the x and y coordinates, which are the
	  top-left outside corner of the new window's bor-
	  ders and are relative to the inside of the parent
	  window's borders.

width
height	  Specify the width and height, which are the cre-
	  ated window's inside dimensions and do not include
	  the created window's borders.  The dimensions must
	  be nonzero, or a BadValue error results.

border_width
	  Specifies the width of the created window's border
	  in pixels.

border	  Specifies the border pixel value of the window.

background
	  Specifies the background pixel value of the win-
	  dow.

|__

The XCreateSimpleWindow function creates an unmapped
InputOutput subwindow for a specified parent window, returns
the window ID of the created window, and causes the X server
to generate a CreateNotify event.  The created window is
placed on top in the stacking order with respect to sib-
lings.	Any part of the window that extends outside its par-
ent window is clipped.	The border_width for an InputOnly
window must be zero, or a BadMatch error results.  XCreateS-
impleWindow inherits its depth, class, and visual from its
parent.  All other window attributes, except background and
border, have their default values.

XCreateSimpleWindow can generate BadAlloc, BadMatch, Bad-
Value, and BadWindow errors.



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3.4.  Destroying Windows

Xlib provides functions that you can use to destroy a window
or destroy all subwindows of a window.


To destroy a window and all of its subwindows, use XDestroy-
Window.
__
|
XDestroyWindow(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window.
|__

The XDestroyWindow function destroys the specified window as
well as all of its subwindows and causes the X server to
generate a DestroyNotify event for each window.  The window
should never be referenced again.  If the window specified
by the w argument is mapped, it is unmapped automatically.
The ordering of the DestroyNotify events is such that for
any given window being destroyed, DestroyNotify is generated
on any inferiors of the window before being generated on the
window itself.	The ordering among siblings and across sub-
hierarchies is not otherwise constrained.  If the window you
specified is a root window, no windows are destroyed.
Destroying a mapped window will generate Expose events on
other windows that were obscured by the window being
destroyed.

XDestroyWindow can generate a BadWindow error.


To destroy all subwindows of a specified window, use XDe-
stroySubwindows.
__
|
XDestroySubwindows(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window.
|__

The XDestroySubwindows function destroys all inferior win-
dows of the specified window, in bottom-to-top stacking



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order.	It causes the X server to generate a DestroyNotify
event for each window.	If any mapped subwindows were actu-
ally destroyed, XDestroySubwindows causes the X server to
generate Expose events on the specified window.  This is
much more efficient than deleting many windows one at a time
because much of the work need be performed only once for all
of the windows, rather than for each window.  The subwindows
should never be referenced again.

XDestroySubwindows can generate a BadWindow error.

3.5.  Mapping Windows

A window is considered mapped if an XMapWindow call has been
made on it.  It may not be visible on the screen for one of
the following reasons:

o    It is obscured by another opaque window.

o    One of its ancestors is not mapped.

o    It is entirely clipped by an ancestor.

Expose events are generated for the window when part or all
of it becomes visible on the screen.  A client receives the
Expose events only if it has asked for them.  Windows retain
their position in the stacking order when they are unmapped.

A window manager may want to control the placement of sub-
windows.  If SubstructureRedirectMask has been selected by a
window manager on a parent window (usually a root window), a
map request initiated by other clients on a child window is
not performed, and the window manager is sent a MapRequest
event.	However, if the override-redirect flag on the child
had been set to True (usually only on pop-up menus), the map
request is performed.

A tiling window manager might decide to reposition and
resize other clients' windows and then decide to map the
window to its final location.  A window manager that wants
to provide decoration might reparent the child into a frame
first.	For further information, see sections 3.2.8 and
10.10.	Only a single client at a time can select for Sub-
structureRedirectMask.

Similarly, a single client can select for ResizeRedirectMask
on a parent window.  Then, any attempt to resize the window
by another client is suppressed, and the client receives a
ResizeRequest event.


To map a given window, use XMapWindow.





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__
|
XMapWindow(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window.
|__

The XMapWindow function maps the window and all of its sub-
windows that have had map requests.  Mapping a window that
has an unmapped ancestor does not display the window but
marks it as eligible for display when the ancestor becomes
mapped.  Such a window is called unviewable.  When all its
ancestors are mapped, the window becomes viewable and will
be visible on the screen if it is not obscured by another
window.  This function has no effect if the window is
already mapped.

If the override-redirect of the window is False and if some
other client has selected SubstructureRedirectMask on the
parent window, then the X server generates a MapRequest
event, and the XMapWindow function does not map the window.
Otherwise, the window is mapped, and the X server generates
a MapNotify event.

If the window becomes viewable and no earlier contents for
it are remembered, the X server tiles the window with its
background.  If the window's background is undefined, the
existing screen contents are not altered, and the X server
generates zero or more Expose events.  If backing-store was
maintained while the window was unmapped, no Expose events
are generated.	If backing-store will now be maintained, a
full-window exposure is always generated.  Otherwise, only
visible regions may be reported.  Similar tiling and expo-
sure take place for any newly viewable inferiors.

If the window is an InputOutput window, XMapWindow generates
Expose events on each InputOutput window that it causes to
be displayed.  If the client maps and paints the window and
if the client begins processing events, the window is
painted twice.	To avoid this, first ask for Expose events
and then map the window, so the client processes input
events as usual.  The event list will include Expose for
each window that has appeared on the screen.  The client's
normal response to an Expose event should be to repaint the
window.  This method usually leads to simpler programs and
to proper interaction with window managers.

XMapWindow can generate a BadWindow error.





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To map and raise a window, use XMapRaised.
__
|
XMapRaised(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window.
|__

The XMapRaised function essentially is similar to XMapWindow
in that it maps the window and all of its subwindows that
have had map requests.	However, it also raises the speci-
fied window to the top of the stack.  For additional infor-
mation, see XMapWindow.

XMapRaised can generate multiple BadWindow errors.


To map all subwindows for a specified window, use XMapSub-
windows.
__
|
XMapSubwindows(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window.
|__

The XMapSubwindows function maps all subwindows for a speci-
fied window in top-to-bottom stacking order.  The X server
generates Expose events on each newly displayed window.
This may be much more efficient than mapping many windows
one at a time because the server needs to perform much of
the work only once, for all of the windows, rather than for
each window.

XMapSubwindows can generate a BadWindow error.

3.6.  Unmapping Windows

Xlib provides functions that you can use to unmap a window
or all subwindows.


To unmap a window, use XUnmapWindow.




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__
|
XUnmapWindow(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window.
|__

The XUnmapWindow function unmaps the specified window and
causes the X server to generate an UnmapNotify event.  If
the specified window is already unmapped, XUnmapWindow has
no effect.  Normal exposure processing on formerly obscured
windows is performed.  Any child window will no longer be
visible until another map call is made on the parent.  In
other words, the subwindows are still mapped but are not
visible until the parent is mapped.  Unmapping a window will
generate Expose events on windows that were formerly
obscured by it.

XUnmapWindow can generate a BadWindow error.


To unmap all subwindows for a specified window, use XUnmap-
Subwindows.
__
|
XUnmapSubwindows(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window.
|__

The XUnmapSubwindows function unmaps all subwindows for the
specified window in bottom-to-top stacking order.  It causes
the X server to generate an UnmapNotify event on each sub-
window and Expose events on formerly obscured windows.
Using this function is much more efficient than unmapping
multiple windows one at a time because the server needs to
perform much of the work only once, for all of the windows,
rather than for each window.

XUnmapSubwindows can generate a BadWindow error.

3.7.  Configuring Windows






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Xlib provides functions that you can use to move a window,
resize a window, move and resize a window, or change a win-
dow's border width.  To change one of these parameters, set
the appropriate member of the XWindowChanges structure and
OR in the corresponding value mask in subsequent calls to
XConfigureWindow.  The symbols for the value mask bits and
the XWindowChanges structure are:
__
|
/* Configure window value mask bits */

#define   CWX			      (1<<0)
#define   CWY			      (1<<1)
#define   CWWidth		      (1<<2)
#define   CWHeight		      (1<<3)
#define   CWBorderWidth 	      (1<<4)
#define   CWSibling		      (1<<5)
#define   CWStackMode		      (1<<6)


/* Values */

typedef struct {
     int x, y;
     int width, height;
     int border_width;
     Window sibling;
     int stack_mode;
} XWindowChanges;

|__

The x and y members are used to set the window's x and y
coordinates, which are relative to the parent's origin and
indicate the position of the upper-left outer corner of the
window.  The width and height members are used to set the
inside size of the window, not including the border, and
must be nonzero, or a BadValue error results.  Attempts to
configure a root window have no effect.

The border_width member is used to set the width of the bor-
der in pixels.	Note that setting just the border width
leaves the outer-left corner of the window in a fixed posi-
tion but moves the absolute position of the window's origin.
If you attempt to set the border-width attribute of an Inpu-
tOnly window nonzero, a BadMatch error results.

The sibling member is used to set the sibling window for
stacking operations.  The stack_mode member is used to set
how the window is to be restacked and can be set to Above,
Below, TopIf, BottomIf, or Opposite.

If the override-redirect flag of the window is False and if
some other client has selected SubstructureRedirectMask on



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the parent, the X server generates a ConfigureRequest event,
and no further processing is performed.  Otherwise, if some
other client has selected ResizeRedirectMask on the window
and the inside width or height of the window is being
changed, a ResizeRequest event is generated, and the current
inside width and height are used instead.  Note that the
override-redirect flag of the window has no effect on Resiz-
eRedirectMask and that SubstructureRedirectMask on the par-
ent has precedence over ResizeRedirectMask on the window.

When the geometry of the window is changed as specified, the
window is restacked among siblings, and a ConfigureNotify
event is generated if the state of the window actually
changes.  GravityNotify events are generated after Config-
ureNotify events.  If the inside width or height of the win-
dow has actually changed, children of the window are
affected as specified.

If a window's size actually changes, the window's subwindows
move according to their window gravity.  Depending on the
window's bit gravity, the contents of the window also may be
moved (see section 3.2.3).

If regions of the window were obscured but now are not,
exposure processing is performed on these formerly obscured
windows, including the window itself and its inferiors.  As
a result of increasing the width or height, exposure pro-
cessing is also performed on any new regions of the window
and any regions where window contents are lost.

The restack check (specifically, the computation for Bot-
tomIf, TopIf, and Opposite) is performed with respect to the
window's final size and position (as controlled by the other
arguments of the request), not its initial position.  If a
sibling is specified without a stack_mode, a BadMatch error
results.

If a sibling and a stack_mode are specified, the window is
restacked as follows:

Above	     The window is placed just above the sibling.
Below	     The window is placed just below the sibling.
TopIf	     If the sibling occludes the window, the window is
	     placed at the top of the stack.
BottomIf     If the window occludes the sibling, the window is
	     placed at the bottom of the stack.
Opposite     If the sibling occludes the window, the window is
	     placed at the top of the stack.  If the window
	     occludes the sibling, the window is placed at the
	     bottom of the stack.


If a stack_mode is specified but no sibling is specified,
the window is restacked as follows:



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Above	     The window is placed at the top of the stack.
Below	     The window is placed at the bottom of the stack.
TopIf	     If any sibling occludes the window, the window is
	     placed at the top of the stack.
BottomIf     If the window occludes any sibling, the window is
	     placed at the bottom of the stack.
Opposite     If any sibling occludes the window, the window is
	     placed at the top of the stack.  If the window
	     occludes any sibling, the window is placed at the
	     bottom of the stack.


Attempts to configure a root window have no effect.


To configure a window's size, location, stacking, or border,
use XConfigureWindow.
__
|
XConfigureWindow(display, w, value_mask, values)
      Display *display;
      Window w;
      unsigned int value_mask;
      XWindowChanges *values;


display   Specifies the connection to the X server.

w	  Specifies the window to be reconfigured.

value_mask
	  Specifies which values are to be set using infor-
	  mation in the values structure.  This mask is the
	  bitwise inclusive OR of the valid configure window
	  values bits.

values	  Specifies the XWindowChanges structure.
|__

The XConfigureWindow function uses the values specified in
the XWindowChanges structure to reconfigure a window's size,
position, border, and stacking order.  Values not specified
are taken from the existing geometry of the window.

If a sibling is specified without a stack_mode or if the
window is not actually a sibling, a BadMatch error results.
Note that the computations for BottomIf, TopIf, and Opposite
are performed with respect to the window's final geometry
(as controlled by the other arguments passed to XConfig-
ureWindow), not its initial geometry.  Any backing store
contents of the window, its inferiors, and other newly visi-
ble windows are either discarded or changed to reflect the
current screen contents (depending on the implementation).




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XConfigureWindow can generate BadMatch, BadValue, and Bad-
Window errors.


To move a window without changing its size, use XMoveWindow.
__
|
XMoveWindow(display, w, x, y)
      Display *display;
      Window w;
      int x, y;


display   Specifies the connection to the X server.

w	  Specifies the window to be moved.

x
y	  Specify the x and y coordinates, which define the
	  new location of the top-left pixel of the window's
	  border or the window itself if it has no border.
|__

The XMoveWindow function moves the specified window to the
specified x and y coordinates, but it does not change the
window's size, raise the window, or change the mapping state
of the window.	Moving a mapped window may or may not lose
the window's contents depending on if the window is obscured
by nonchildren and if no backing store exists.	If the con-
tents of the window are lost, the X server generates Expose
events.  Moving a mapped window generates Expose events on
any formerly obscured windows.

If the override-redirect flag of the window is False and
some other client has selected SubstructureRedirectMask on
the parent, the X server generates a ConfigureRequest event,
and no further processing is performed.  Otherwise, the win-
dow is moved.

XMoveWindow can generate a BadWindow error.


To change a window's size without changing the upper-left
coordinate, use XResizeWindow.













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__
|
XResizeWindow(display, w, width, height)
      Display *display;
      Window w;
      unsigned int width, height;


display   Specifies the connection to the X server.

w	  Specifies the window.

width
height	  Specify the width and height, which are the inte-
	  rior dimensions of the window after the call com-
	  pletes.
|__

The XResizeWindow function changes the inside dimensions of
the specified window, not including its borders.  This func-
tion does not change the window's upper-left coordinate or
the origin and does not restack the window.  Changing the
size of a mapped window may lose its contents and generate
Expose events.	If a mapped window is made smaller, changing
its size generates Expose events on windows that the mapped
window formerly obscured.

If the override-redirect flag of the window is False and
some other client has selected SubstructureRedirectMask on
the parent, the X server generates a ConfigureRequest event,
and no further processing is performed.  If either width or
height is zero, a BadValue error results.

XResizeWindow can generate BadValue and BadWindow errors.


To change the size and location of a window, use XMoveRe-
sizeWindow.




















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__
|
XMoveResizeWindow(display, w, x, y, width, height)
      Display *display;
      Window w;
      int x, y;
      unsigned int width, height;


display   Specifies the connection to the X server.

w	  Specifies the window to be reconfigured.

x
y	  Specify the x and y coordinates, which define the
	  new position of the window relative to its parent.

width
height	  Specify the width and height, which define the
	  interior size of the window.
|__

The XMoveResizeWindow function changes the size and location
of the specified window without raising it.  Moving and
resizing a mapped window may generate an Expose event on the
window.  Depending on the new size and location parameters,
moving and resizing a window may generate Expose events on
windows that the window formerly obscured.

If the override-redirect flag of the window is False and
some other client has selected SubstructureRedirectMask on
the parent, the X server generates a ConfigureRequest event,
and no further processing is performed.  Otherwise, the win-
dow size and location are changed.

XMoveResizeWindow can generate BadValue and BadWindow
errors.


To change the border width of a given window, use XSetWin-
dowBorderWidth.

















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__
|
XSetWindowBorderWidth(display, w, width)
      Display *display;
      Window w;
      unsigned int width;


display   Specifies the connection to the X server.

w	  Specifies the window.

width	  Specifies the width of the window border.
|__

The XSetWindowBorderWidth function sets the specified win-
dow's border width to the specified width.

XSetWindowBorderWidth can generate a BadWindow error.

3.8.  Changing Window Stacking Order


Xlib provides functions that you can use to raise, lower,
circulate, or restack windows.


To raise a window so that no sibling window obscures it, use
XRaiseWindow.
__
|
XRaiseWindow(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window.
|__

The XRaiseWindow function raises the specified window to the
top of the stack so that no sibling window obscures it.  If
the windows are regarded as overlapping sheets of paper
stacked on a desk, then raising a window is analogous to
moving the sheet to the top of the stack but leaving its x
and y location on the desk constant.  Raising a mapped win-
dow may generate Expose events for the window and any mapped
subwindows that were formerly obscured.

If the override-redirect attribute of the window is False
and some other client has selected SubstructureRedirectMask
on the parent, the X server generates a ConfigureRequest
event, and no processing is performed.	Otherwise, the win-
dow is raised.



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XRaiseWindow can generate a BadWindow error.


To lower a window so that it does not obscure any sibling
windows, use XLowerWindow.
__
|
XLowerWindow(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window.
|__

The XLowerWindow function lowers the specified window to the
bottom of the stack so that it does not obscure any sibling
windows.  If the windows are regarded as overlapping sheets
of paper stacked on a desk, then lowering a window is analo-
gous to moving the sheet to the bottom of the stack but
leaving its x and y location on the desk constant.  Lowering
a mapped window will generate Expose events on any windows
it formerly obscured.

If the override-redirect attribute of the window is False
and some other client has selected SubstructureRedirectMask
on the parent, the X server generates a ConfigureRequest
event, and no processing is performed.	Otherwise, the win-
dow is lowered to the bottom of the stack.

XLowerWindow can generate a BadWindow error.


To circulate a subwindow up or down, use XCirculateSubwin-
dows.




















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__
|
XCirculateSubwindows(display, w, direction)
      Display *display;
      Window w;
      int direction;


display   Specifies the connection to the X server.

w	  Specifies the window.

direction Specifies the direction (up or down) that you want
	  to circulate the window.  You can pass RaiseLowest
	  or LowerHighest.
|__

The XCirculateSubwindows function circulates children of the
specified window in the specified direction.  If you specify
RaiseLowest, XCirculateSubwindows raises the lowest mapped
child (if any) that is occluded by another child to the top
of the stack.  If you specify LowerHighest, XCirculateSub-
windows lowers the highest mapped child (if any) that
occludes another child to the bottom of the stack.  Exposure
processing is then performed on formerly obscured windows.
If some other client has selected SubstructureRedirectMask
on the window, the X server generates a CirculateRequest
event, and no further processing is performed.	If a child
is actually restacked, the X server generates a CirculateNo-
tify event.

XCirculateSubwindows can generate BadValue and BadWindow
errors.


To raise the lowest mapped child of a window that is par-
tially or completely occluded by another child, use XCircu-
lateSubwindowsUp.
__
|
XCirculateSubwindowsUp(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window.
|__

The XCirculateSubwindowsUp function raises the lowest mapped
child of the specified window that is partially or com-
pletely occluded by another child.  Completely unobscured
children are not affected.  This is a convenience function
equivalent to XCirculateSubwindows with RaiseLowest



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specified.

XCirculateSubwindowsUp can generate a BadWindow error.


To lower the highest mapped child of a window that partially
or completely occludes another child, use XCirculateSubwin-
dowsDown.
__
|
XCirculateSubwindowsDown(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window.
|__

The XCirculateSubwindowsDown function lowers the highest
mapped child of the specified window that partially or com-
pletely occludes another child.  Completely unobscured chil-
dren are not affected.	This is a convenience function
equivalent to XCirculateSubwindows with LowerHighest speci-
fied.

XCirculateSubwindowsDown can generate a BadWindow error.


To restack a set of windows from top to bottom, use
XRestackWindows.
__
|
XRestackWindows(display, windows, nwindows);
      Display *display;
      Window windows[];
      int nwindows;


display   Specifies the connection to the X server.

windows   Specifies an array containing the windows to be
	  restacked.

nwindows  Specifies the number of windows to be restacked.
|__

The XRestackWindows function restacks the windows in the
order specified, from top to bottom.  The stacking order of
the first window in the windows array is unaffected, but the
other windows in the array are stacked underneath the first
window, in the order of the array.  The stacking order of
the other windows is not affected.  For each window in the



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window array that is not a child of the specified window, a
BadMatch error results.

If the override-redirect attribute of a window is False and
some other client has selected SubstructureRedirectMask on
the parent, the X server generates ConfigureRequest events
for each window whose override-redirect flag is not set, and
no further processing is performed.  Otherwise, the windows
will be restacked in top-to-bottom order.

XRestackWindows can generate a BadWindow error.

3.9.  Changing Window Attributes


Xlib provides functions that you can use to set window
attributes.  XChangeWindowAttributes is the more general
function that allows you to set one or more window
attributes provided by the XSetWindowAttributes structure.
The other functions described in this section allow you to
set one specific window attribute, such as a window's back-
ground.


To change one or more attributes for a given window, use
XChangeWindowAttributes.































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__
|
XChangeWindowAttributes(display, w, valuemask, attributes)
      Display *display;
      Window w;
      unsigned long valuemask;
      XSetWindowAttributes *attributes;


display   Specifies the connection to the X server.

w	  Specifies the window.

valuemask Specifies which window attributes are defined in
	  the attributes argument.  This mask is the bitwise
	  inclusive OR of the valid attribute mask bits.  If
	  valuemask is zero, the attributes are ignored and
	  are not referenced.  The values and restrictions
	  are the same as for XCreateWindow.


attributes
	  Specifies the structure from which the values (as
	  specified by the value mask) are to be taken.  The
	  value mask should have the appropriate bits set to
	  indicate which attributes have been set in the
	  structure (see section 3.2).
|__

Depending on the valuemask, the XChangeWindowAttributes
function uses the window attributes in the XSetWindowAt-
tributes structure to change the specified window
attributes.  Changing the background does not cause the win-
dow contents to be changed.  To repaint the window and its
background, use XClearWindow.  Setting the border or chang-
ing the background such that the border tile origin changes
causes the border to be repainted.  Changing the background
of a root window to None or ParentRelative restores the
default background pixmap.  Changing the border of a root
window to CopyFromParent restores the default border pixmap.
Changing the win-gravity does not affect the current posi-
tion of the window.  Changing the backing-store of an
obscured window to WhenMapped or Always, or changing the
backing-planes, backing-pixel, or save-under of a mapped
window may have no immediate effect.  Changing the colormap
of a window (that is, defining a new map, not changing the
contents of the existing map) generates a ColormapNotify
event.	Changing the colormap of a visible window may have
no immediate effect on the screen because the map may not be
installed (see XInstallColormap).  Changing the cursor of a
root window to None restores the default cursor.  Whenever
possible, you are encouraged to share colormaps.

Multiple clients can select input on the same window.  Their
event masks are maintained separately.	When an event is



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generated, it is reported to all interested clients.  How-
ever, only one client at a time can select for Substructur-
eRedirectMask, ResizeRedirectMask, and ButtonPressMask.  If
a client attempts to select any of these event masks and
some other client has already selected one, a BadAccess
error results.	There is only one do-not-propagate-mask for
a window, not one per client.

XChangeWindowAttributes can generate BadAccess, BadColor,
BadCursor, BadMatch, BadPixmap, BadValue, and BadWindow
errors.


To set the background of a window to a given pixel, use
XSetWindowBackground.
__
|
XSetWindowBackground(display, w, background_pixel)
      Display *display;
      Window w;
      unsigned long background_pixel;


display   Specifies the connection to the X server.

w	  Specifies the window.

background_pixel
	  Specifies the pixel that is to be used for the
	  background.
|__

The XSetWindowBackground function sets the background of the
window to the specified pixel value.  Changing the back-
ground does not cause the window contents to be changed.
XSetWindowBackground uses a pixmap of undefined size filled
with the pixel value you passed.  If you try to change the
background of an InputOnly window, a BadMatch error results.

XSetWindowBackground can generate BadMatch and BadWindow
errors.



To set the background of a window to a given pixmap, use
XSetWindowBackgroundPixmap.











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__
|
XSetWindowBackgroundPixmap(display, w, background_pixmap)
      Display *display;
      Window w;
      Pixmap background_pixmap;


display   Specifies the connection to the X server.

w	  Specifies the window.

background_pixmap
	  Specifies the background pixmap, ParentRelative,
	  or None.
|__

The XSetWindowBackgroundPixmap function sets the background
pixmap of the window to the specified pixmap.  The back-
ground pixmap can immediately be freed if no further
explicit references to it are to be made.  If ParentRelative
is specified, the background pixmap of the window's parent
is used, or on the root window, the default background is
restored.  If you try to change the background of an Inpu-
tOnly window, a BadMatch error results.  If the background
is set to None, the window has no defined background.

XSetWindowBackgroundPixmap can generate BadMatch, BadPixmap,
and BadWindow errors.

			    Note

     XSetWindowBackground and XSetWindowBackground-
     Pixmap do not change the current contents of the
     window.



To change and repaint a window's border to a given pixel,
use XSetWindowBorder.


















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__
|
XSetWindowBorder(display, w, border_pixel)
      Display *display;
      Window w;
      unsigned long border_pixel;


display   Specifies the connection to the X server.

w	  Specifies the window.

border_pixel
	  Specifies the entry in the colormap.
|__

The XSetWindowBorder function sets the border of the window
to the pixel value you specify.  If you attempt to perform
this on an InputOnly window, a BadMatch error results.

XSetWindowBorder can generate BadMatch and BadWindow errors.


To change and repaint the border tile of a given window, use
XSetWindowBorderPixmap.
__
|
XSetWindowBorderPixmap(display, w, border_pixmap)
      Display *display;
      Window w;
      Pixmap border_pixmap;


display   Specifies the connection to the X server.

w	  Specifies the window.

border_pixmap
	  Specifies the border pixmap or CopyFromParent.
|__

The XSetWindowBorderPixmap function sets the border pixmap
of the window to the pixmap you specify.  The border pixmap
can be freed immediately if no further explicit references
to it are to be made.  If you specify CopyFromParent, a copy
of the parent window's border pixmap is used.  If you
attempt to perform this on an InputOnly window, a BadMatch
error results.

XSetWindowBorderPixmap can generate BadMatch, BadPixmap, and
BadWindow errors.


To set the colormap of a given window, use XSetWindowCol-
ormap.



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__
|
XSetWindowColormap(display, w, colormap)
      Display *display;
      Window w;
      Colormap colormap;


display   Specifies the connection to the X server.

w	  Specifies the window.

colormap  Specifies the colormap.
|__

The XSetWindowColormap function sets the specified colormap
of the specified window.  The colormap must have the same
visual type as the window, or a BadMatch error results.

XSetWindowColormap can generate BadColor, BadMatch, and Bad-
Window errors.


To define which cursor will be used in a window, use XDe-
fineCursor.
__
|
XDefineCursor(display, w, cursor)
      Display *display;
      Window w;
      Cursor cursor;


display   Specifies the connection to the X server.

w	  Specifies the window.

cursor	  Specifies the cursor that is to be displayed or
	  None.
|__

If a cursor is set, it will be used when the pointer is in
the window.  If the cursor is None, it is equivalent to XUn-
defineCursor.

XDefineCursor can generate BadCursor and BadWindow errors.


To undefine the cursor in a given window, use XUndefineCur-
sor.








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__
|
XUndefineCursor(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window.
|__

The XUndefineCursor function undoes the effect of a previous
XDefineCursor for this window.	When the pointer is in the
window, the parent's cursor will now be used.  On the root
window, the default cursor is restored.

XUndefineCursor can generate a BadWindow error.








































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			 Chapter 4

		Window Information Functions



After you connect the display to the X server and create a
window, you can use the Xlib window information functions
to:

o    Obtain information about a window

o    Translate screen coordinates

o    Manipulate property lists

o    Obtain and change window properties

o    Manipulate selections

4.1.  Obtaining Window Information

Xlib provides functions that you can use to obtain informa-
tion about the window tree, the window's current attributes,
the window's current geometry, or the current pointer coor-
dinates.  Because they are most frequently used by window
managers, these functions all return a status to indicate
whether the window still exists.


To obtain the parent, a list of children, and number of
children for a given window, use XQueryTree.























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__
|
Status XQueryTree(display, w, root_return, parent_return, children_return, nchildren_return)
      Display *display;
      Window w;
      Window *root_return;
      Window *parent_return;
      Window **children_return;
      unsigned int *nchildren_return;


display   Specifies the connection to the X server.

w	  Specifies the window whose list of children, root,
	  parent, and number of children you want to obtain.

root_return
	  Returns the root window.

parent_return
	  Returns the parent window.

children_return
	  Returns the list of children.

nchildren_return
	  Returns the number of children.
|__

The XQueryTree function returns the root ID, the parent win-
dow ID, a pointer to the list of children windows (NULL when
there are no children), and the number of children in the
list for the specified window.	The children are listed in
current stacking order, from bottom-most (first) to top-most
(last).  XQueryTree returns zero if it fails and nonzero if
it succeeds.  To free a non-NULL children list when it is no
longer needed, use XFree.

XQueryTree can generate a BadWindow error.


To obtain the current attributes of a given window, use
XGetWindowAttributes.















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__
|
Status XGetWindowAttributes(display, w, window_attributes_return)
      Display *display;
      Window w;
      XWindowAttributes *window_attributes_return;


display   Specifies the connection to the X server.

w	  Specifies the window whose current attributes you
	  want to obtain.

window_attributes_return
	  Returns the specified window's attributes in the
	  XWindowAttributes structure.
|__

The XGetWindowAttributes function returns the current
attributes for the specified window to an XWindowAttributes
structure.

__
|
typedef struct {
     int x, y;		      /* location of window */
     int width, height;       /* width and height of window */
     int border_width;	      /* border width of window */
     int depth; 	      /* depth of window */
     Visual *visual;	      /* the associated visual structure */
     Window root;	      /* root of screen containing window */
     int class; 	      /* InputOutput, InputOnly*/
     int bit_gravity;	      /* one of the bit gravity values */
     int win_gravity;	      /* one of the window gravity values */
     int backing_store;       /* NotUseful, WhenMapped, Always */
     unsigned long backing_planes;/* planes to be preserved if possible */
     unsigned long backing_pixel;/* value to be used when restoring planes */
     Bool save_under;	      /* boolean, should bits under be saved? */
     Colormap colormap;       /* color map to be associated with window */
     Bool map_installed;      /* boolean, is color map currently installed*/
     int map_state;	      /* IsUnmapped, IsUnviewable, IsViewable */
     long all_event_masks;    /* set of events all people have interest in*/
     long your_event_mask;    /* my event mask */
     long do_not_propagate_mask;/* set of events that should not propagate */
     Bool override_redirect;  /* boolean value for override-redirect */
     Screen *screen;	      /* back pointer to correct screen */
} XWindowAttributes;

|__

The x and y members are set to the upper-left outer corner
relative to the parent window's origin.  The width and
height members are set to the inside size of the window, not
including the border.  The border_width member is set to the
window's border width in pixels.  The depth member is set to



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the depth of the window (that is, bits per pixel for the
object).  The visual member is a pointer to the screen's
associated Visual structure.  The root member is set to the
root window of the screen containing the window.  The class
member is set to the window's class and can be either
InputOutput or InputOnly.

The bit_gravity member is set to the window's bit gravity
and can be one of the following:


ForgetGravity	  EastGravity
NorthWestGrav-	  SouthWestGrav-
ity		  ity
NorthGravity	  SouthGravity
NorthEastGrav-	  SouthEastGrav-
ity		  ity
WestGravity	  StaticGravity
CenterGravity


The win_gravity member is set to the window's window gravity
and can be one of the following:


UnmapGravity	  EastGravity
NorthWestGrav-	  SouthWestGrav-
ity		  ity
NorthGravity	  SouthGravity
NorthEastGrav-	  SouthEastGrav-
ity		  ity
WestGravity	  StaticGravity
CenterGravity


For additional information on gravity, see section 3.2.3.

The backing_store member is set to indicate how the X server
should maintain the contents of a window and can be When-
Mapped, Always, or NotUseful.  The backing_planes member is
set to indicate (with bits set to 1) which bit planes of the
window hold dynamic data that must be preserved in back-
ing_stores and during save_unders.  The backing_pixel member
is set to indicate what values to use for planes not set in
backing_planes.

The save_under member is set to True or False.	The colormap
member is set to the colormap for the specified window and
can be a colormap ID or None.  The map_installed member is
set to indicate whether the colormap is currently installed
and can be True or False.  The map_state member is set to
indicate the state of the window and can be IsUnmapped,
IsUnviewable, or IsViewable.  IsUnviewable is used if the
window is mapped but some ancestor is unmapped.



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The all_event_masks member is set to the bitwise inclusive
OR of all event masks selected on the window by all clients.
The your_event_mask member is set to the bitwise inclusive
OR of all event masks selected by the querying client.	The
do_not_propagate_mask member is set to the bitwise inclusive
OR of the set of events that should not propagate.

The override_redirect member is set to indicate whether this
window overrides structure control facilities and can be
True or False.	Window manager clients should ignore the
window if this member is True.

The screen member is set to a screen pointer that gives you
a back pointer to the correct screen.  This makes it easier
to obtain the screen information without having to loop over
the root window fields to see which field matches.

XGetWindowAttributes can generate BadDrawable and BadWindow
errors.


To obtain the current geometry of a given drawable, use
XGetGeometry.


































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__
|
Status XGetGeometry(display, d, root_return, x_return, y_return, width_return,
		      height_return, border_width_return, depth_return)
	Display *display;
	Drawable d;
	Window *root_return;
	int *x_return, *y_return;
	unsigned int *width_return, *height_return;
	unsigned int *border_width_return;
	unsigned int *depth_return;


display   Specifies the connection to the X server.

d	  Specifies the drawable, which can be a window or a
	  pixmap.

root_return
	  Returns the root window.

x_return
y_return  Return the x and y coordinates that define the
	  location of the drawable.  For a window, these
	  coordinates specify the upper-left outer corner
	  relative to its parent's origin.  For pixmaps,
	  these coordinates are always zero.

width_return
height_return
	  Return the drawable's dimensions (width and
	  height).  For a window, these dimensions specify
	  the inside size, not including the border.

border_width_return
	  Returns the border width in pixels.  If the draw-
	  able is a pixmap, it returns zero.

depth_return
	  Returns the depth of the drawable (bits per pixel
	  for the object).
|__

The XGetGeometry function returns the root window and the
current geometry of the drawable.  The geometry of the draw-
able includes the x and y coordinates, width and height,
border width, and depth.  These are described in the argu-
ment list.  It is legal to pass to this function a window
whose class is InputOnly.

XGetGeometry can generate a BadDrawable error.







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4.2.  Translating Screen Coordinates

Applications sometimes need to perform a coordinate trans-
formation from the coordinate space of one window to another
window or need to determine which window the pointing device
is in.	XTranslateCoordinates and XQueryPointer fulfill
these needs (and avoid any race conditions) by asking the X
server to perform these operations.


To translate a coordinate in one window to the coordinate
space of another window, use XTranslateCoordinates.
__
|
Bool XTranslateCoordinates(display, src_w, dest_w, src_x, src_y, dest_x_return,
			    dest_y_return, child_return)
      Display *display;
      Window src_w, dest_w;
      int src_x, src_y;
      int *dest_x_return, *dest_y_return;
      Window *child_return;


display   Specifies the connection to the X server.

src_w	  Specifies the source window.

dest_w	  Specifies the destination window.

src_x
src_y	  Specify the x and y coordinates within the source
	  window.

dest_x_return
dest_y_return
	  Return the x and y coordinates within the destina-
	  tion window.

child_return
	  Returns the child if the coordinates are contained
	  in a mapped child of the destination window.
|__

If XTranslateCoordinates returns True, it takes the src_x
and src_y coordinates relative to the source window's origin
and returns these coordinates to dest_x_return and
dest_y_return relative to the destination window's origin.
If XTranslateCoordinates returns False, src_w and dest_w are
on different screens, and dest_x_return and dest_y_return
are zero.  If the coordinates are contained in a mapped
child of dest_w, that child is returned to child_return.
Otherwise, child_return is set to None.





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XTranslateCoordinates can generate a BadWindow error.


To obtain the screen coordinates of the pointer or to deter-
mine the pointer coordinates relative to a specified window,
use XQueryPointer.
__
|
Bool XQueryPointer(display, w, root_return, child_return, root_x_return, root_y_return,
		     win_x_return, win_y_return, mask_return)
      Display *display;
      Window w;
      Window *root_return, *child_return;
      int *root_x_return, *root_y_return;
      int *win_x_return, *win_y_return;
      unsigned int *mask_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

root_return
	  Returns the root window that the pointer is in.

child_return
	  Returns the child window that the pointer is
	  located in, if any.

root_x_return
root_y_return
	  Return the pointer coordinates relative to the
	  root window's origin.

win_x_return
win_y_return
	  Return the pointer coordinates relative to the
	  specified window.

mask_return
	  Returns the current state of the modifier keys and
	  pointer buttons.
|__

The XQueryPointer function returns the root window the
pointer is logically on and the pointer coordinates relative
to the root window's origin.  If XQueryPointer returns
False, the pointer is not on the same screen as the speci-
fied window, and XQueryPointer returns None to child_return
and zero to win_x_return and win_y_return.  If XQueryPointer
returns True, the pointer coordinates returned to
win_x_return and win_y_return are relative to the origin of
the specified window.  In this case, XQueryPointer returns
the child that contains the pointer, if any, or else None to



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child_return.

XQueryPointer returns the current logical state of the key-
board buttons and the modifier keys in mask_return.  It sets
mask_return to the bitwise inclusive OR of one or more of
the button or modifier key bitmasks to match the current
state of the mouse buttons and the modifier keys.

Note that the logical state of a device (as seen through
Xlib) may lag the physical state if device event processing
is frozen (see section 12.1).

XQueryPointer can generate a BadWindow error.

4.3.  Properties and Atoms

A property is a collection of named, typed data.  The window
system has a set of predefined properties (for example, the
name of a window, size hints, and so on), and users can
define any other arbitrary information and associate it with
windows.  Each property has a name, which is an ISO Latin-1
string.  For each named property, a unique identifier (atom)
is associated with it.	A property also has a type, for
example, string or integer.  These types are also indicated
using atoms, so arbitrary new types can be defined.  Data of
only one type may be associated with a single property name.
Clients can store and retrieve properties associated with
windows.  For efficiency reasons, an atom is used rather
than a character string.  XInternAtom can be used to obtain
the atom for property names.

A property is also stored in one of several possible for-
mats.  The X server can store the information as 8-bit quan-
tities, 16-bit quantities, or 32-bit quantities.  This per-
mits the X server to present the data in the byte order that
the client expects.

			    Note

     If you define further properties of complex type,
     you must encode and decode them yourself.	These
     functions must be carefully written if they are to
     be portable.  For further information about how to
     write a library extension, see appendix C.

The type of a property is defined by an atom, which allows
for arbitrary extension in this type scheme.

Certain property names are predefined in the server for com-
monly used functions.  The atoms for these properties are
defined in <X11/Xatom.h>.  To avoid name clashes with user
symbols, the #define name for each atom has the XA_ prefix.
For an explanation of the functions that let you get and set
much of the information stored in these predefined



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properties, see chapter 14.

The core protocol imposes no semantics on these property
names, but semantics are specified in other X Consortium
standards, such as the Inter-Client Communication Conven-
tions Manual and the X Logical Font Description Conventions.

You can use properties to communicate other information
between applications.  The functions described in this sec-
tion let you define new properties and get the unique atom
IDs in your applications.

Although any particular atom can have some client interpre-
tation within each of the name spaces, atoms occur in five
distinct name spaces within the protocol:

o    Selections

o    Property names

o    Property types

o    Font properties

o    Type of a ClientMessage event (none are built into the
     X server)


The built-in selection property names are:


PRIMARY
SECONDARY


The built-in property names are:

CUT_BUFFER0	       RESOURCE_MANAGER
CUT_BUFFER1	       WM_CLASS
CUT_BUFFER2	       WM_CLIENT_MACHINE
CUT_BUFFER3	       WM_COLORMAP_WINDOWS
CUT_BUFFER4	       WM_COMMAND
CUT_BUFFER5	       WM_HINTS
CUT_BUFFER6	       WM_ICON_NAME
CUT_BUFFER7	       WM_ICON_SIZE
RGB_BEST_MAP	       WM_NAME
RGB_BLUE_MAP	       WM_NORMAL_HINTS
RGB_DEFAULT_MAP        WM_PROTOCOLS
RGB_GRAY_MAP	       WM_STATE
RGB_GREEN_MAP	       WM_TRANSIENT_FOR
RGB_RED_MAP	       WM_ZOOM_HINTS






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The built-in property types are:


ARC		       POINT
ATOM		       RGB_COLOR_MAP
BITMAP		       RECTANGLE
CARDINAL	       STRING
COLORMAP	       VISUALID
CURSOR		       WINDOW
DRAWABLE	       WM_HINTS
FONT		       WM_SIZE_HINTS
INTEGER
PIXMAP


The built-in font property names are:

MIN_SPACE	       STRIKEOUT_DESCENT
NORM_SPACE	       STRIKEOUT_ASCENT
MAX_SPACE	       ITALIC_ANGLE
END_SPACE	       X_HEIGHT
SUPERSCRIPT_X	       QUAD_WIDTH
SUPERSCRIPT_Y	       WEIGHT
SUBSCRIPT_X	       POINT_SIZE
SUBSCRIPT_Y	       RESOLUTION
UNDERLINE_POSITION     COPYRIGHT
UNDERLINE_THICKNESS    NOTICE
FONT_NAME	       FAMILY_NAME
FULL_NAME	       CAP_HEIGHT


For further information about font properties, see section
8.5.


To return an atom for a given name, use XInternAtom.





















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__
|
Atom XInternAtom(display, atom_name, only_if_exists)
      Display *display;
      char *atom_name;
      Bool only_if_exists;


display   Specifies the connection to the X server.

atom_name Specifies the name associated with the atom you
	  want returned.

only_if_exists
	  Specifies a Boolean value that indicates whether
	  the atom must be created.
|__

The XInternAtom function returns the atom identifier associ-
ated with the specified atom_name string.  If only_if_exists
is False, the atom is created if it does not exist.  There-
fore, XInternAtom can return None.  If the atom name is not
in the Host Portable Character Encoding, the result is
implementation-dependent.  Uppercase and lowercase matter;
the strings ``thing'', ``Thing'', and ``thinG'' all desig-
nate different atoms.  The atom will remain defined even
after the client's connection closes.  It will become unde-
fined only when the last connection to the X server closes.

XInternAtom can generate BadAlloc and BadValue errors.


To return atoms for an array of names, use XInternAtoms.

























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__
|
Status XInternAtoms(display, names, count, only_if_exists, atoms_return)
      Display *display;
      char **names;
      int count;
      Bool only_if_exists;
      Atom *atoms_return;


display   Specifies the connection to the X server.

names	  Specifies the array of atom names.

count	  Specifies the number of atom names in the array.

only_if_exists
	  Specifies a Boolean value that indicates whether
	  the atom must be created.

atoms_return
	  Returns the atoms.
|__

The XInternAtoms function returns the atom identifiers asso-
ciated with the specified names.  The atoms are stored in
the atoms_return array supplied by the caller.	Calling this
function is equivalent to calling XInternAtom for each of
the names in turn with the specified value of
only_if_exists, but this function minimizes the number of
round-trip protocol exchanges between the client and the X
server.

This function returns a nonzero status if atoms are returned
for all of the names; otherwise, it returns zero.

XInternAtoms can generate BadAlloc and BadValue errors.


To return a name for a given atom identifier, use XGetAtom-
Name.
__
|
char *XGetAtomName(display, atom)
      Display *display;
      Atom atom;


display   Specifies the connection to the X server.

atom	  Specifies the atom for the property name you want
	  returned.
|__

The XGetAtomName function returns the name associated with



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the specified atom.  If the data returned by the server is
in the Latin Portable Character Encoding, then the returned
string is in the Host Portable Character Encoding.  Other-
wise, the result is implementation-dependent.  To free the
resulting string, call XFree.

XGetAtomName can generate a BadAtom error.


To return the names for an array of atom identifiers, use
XGetAtomNames.
__
|
Status XGetAtomNames(display, atoms, count, names_return)
      Display *display;
      Atom *atoms;
      int count;
      char **names_return;


display   Specifies the connection to the X server.

atoms	  Specifies the array of atoms.

count	  Specifies the number of atoms in the array.

names_return
	  Returns the atom names.
|__

The XGetAtomNames function returns the names associated with
the specified atoms.  The names are stored in the
names_return array supplied by the caller.  Calling this
function is equivalent to calling XGetAtomName for each of
the atoms in turn, but this function minimizes the number of
round-trip protocol exchanges between the client and the X
server.

This function returns a nonzero status if names are returned
for all of the atoms; otherwise, it returns zero.

XGetAtomNames can generate a BadAtom error.

4.4.  Obtaining and Changing Window Properties

You can attach a property list to every window.  Each prop-
erty has a name, a type, and a value (see section 4.3).  The
value is an array of 8-bit, 16-bit, or 32-bit quantities,
whose interpretation is left to the clients.  The type char
is used to represent 8-bit quantities, the type short is
used to represent 16-bit quantities, and the type long is
used to represent 32-bit quantities.





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Xlib provides functions that you can use to obtain, change,
update, or interchange window properties.  In addition, Xlib
provides other utility functions for inter-client communica-
tion (see chapter 14).


To obtain the type, format, and value of a property of a
given window, use XGetWindowProperty.

















































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__
|
int XGetWindowProperty(display, w, property, long_offset, long_length, delete, req_type,
			actual_type_return, actual_format_return, nitems_return, bytes_after_return,
			prop_return)
      Display *display;
      Window w;
      Atom property;
      long long_offset, long_length;
      Bool delete;
      Atom req_type;
      Atom *actual_type_return;
      int *actual_format_return;
      unsigned long *nitems_return;
      unsigned long *bytes_after_return;
      unsigned char **prop_return;


display   Specifies the connection to the X server.

w	  Specifies the window whose property you want to
	  obtain.

property  Specifies the property name.

long_offset
	  Specifies the offset in the specified property (in
	  32-bit quantities) where the data is to be
	  retrieved.

long_length
	  Specifies the length in 32-bit multiples of the
	  data to be retrieved.

delete	  Specifies a Boolean value that determines whether
	  the property is deleted.

req_type  Specifies the atom identifier associated with the
	  property type or AnyPropertyType.

actual_type_return
	  Returns the atom identifier  that defines the
	  actual type of the property.

actual_format_return
	  Returns the actual format of the property.

nitems_return
	  Returns the actual number of 8-bit, 16-bit, or
	  32-bit items stored in the prop_return data.

bytes_after_return
	  Returns the number of bytes remaining to be read
	  in the property if a partial read was performed.




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prop_return
	  Returns the data in the specified format.
|__

The XGetWindowProperty function returns the actual type of
the property; the actual format of the property; the number
of 8-bit, 16-bit, or 32-bit items transferred; the number of
bytes remaining to be read in the property; and a pointer to
the data actually returned.  XGetWindowProperty sets the
return arguments as follows:

o    If the specified property does not exist for the speci-
     fied window, XGetWindowProperty returns None to
     actual_type_return and the value zero to actual_for-
     mat_return and bytes_after_return.  The nitems_return
     argument is empty.  In this case, the delete argument
     is ignored.

o    If the specified property exists but its type does not
     match the specified type, XGetWindowProperty returns
     the actual property type to actual_type_return, the
     actual property format (never zero) to actual_for-
     mat_return, and the property length in bytes (even if
     the actual_format_return is 16 or 32) to
     bytes_after_return.  It also ignores the delete argu-
     ment.  The nitems_return argument is empty.

o    If the specified property exists and either you assign
     AnyPropertyType to the req_type argument or the speci-
     fied type matches the actual property type, XGetWindow-
     Property returns the actual property type to
     actual_type_return and the actual property format
     (never zero) to actual_format_return.  It also returns
     a value to bytes_after_return and nitems_return, by
     defining the following values:

	  N = actual length of the stored property in bytes
	       (even if the format is 16 or 32)
	  I = 4 * long_offset
	  T = N - I
	  L = MINIMUM(T, 4 * long_length)
	  A = N - (I + L)

     The returned value starts at byte index I in the prop-
     erty (indexing from zero), and its length in bytes is
     L.  If the value for long_offset causes L to be nega-
     tive, a BadValue error results.  The value of
     bytes_after_return is A, giving the number of trailing
     unread bytes in the stored property.

If the returned format is 8, the returned data is repre-
sented as a char array.  If the returned format is 16, the
returned data is represented as a short array and should be
cast to that type to obtain the elements.  If the returned



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format is 32, the returned data is represented as a long
array and should be cast to that type to obtain the ele-
ments.

XGetWindowProperty always allocates one extra byte in
prop_return (even if the property is zero length) and sets
it to zero so that simple properties consisting of charac-
ters do not have to be copied into yet another string before
use.

If delete is True and bytes_after_return is zero, XGetWin-
dowProperty deletes the property from the window and gener-
ates a PropertyNotify event on the window.

The function returns Success if it executes successfully.
To free the resulting data, use XFree.

XGetWindowProperty can generate BadAtom, BadValue, and Bad-
Window errors.


To obtain a given window's property list, use XListProper-
ties.
__
|
Atom *XListProperties(display, w, num_prop_return)
      Display *display;
      Window w;
      int *num_prop_return;


display   Specifies the connection to the X server.

w	  Specifies the window whose property list you want
	  to obtain.

num_prop_return
	  Returns the length of the properties array.
|__

The XListProperties function returns a pointer to an array
of atom properties that are defined for the specified window
or returns NULL if no properties were found.  To free the
memory allocated by this function, use XFree.

XListProperties can generate a BadWindow error.


To change a property of a given window, use XChangeProperty.








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__
|
XChangeProperty(display, w, property, type, format, mode, data, nelements)
      Display *display;
      Window w;
      Atom property, type;
      int format;
      int mode;
      unsigned char *data;
      int nelements;


display   Specifies the connection to the X server.

w	  Specifies the window whose property you want to
	  change.

property  Specifies the property name.

type	  Specifies the type of the property.  The X server
	  does not interpret the type but simply passes it
	  back to an application that later calls XGetWin-
	  dowProperty.

format	  Specifies whether the data should be viewed as a
	  list of 8-bit, 16-bit, or 32-bit quantities.	Pos-
	  sible values are 8, 16, and 32.  This information
	  allows the X server to correctly perform byte-swap
	  operations as necessary.  If the format is 16-bit
	  or 32-bit, you must explicitly cast your data
	  pointer to an (unsigned char *) in the call to
	  XChangeProperty.

mode	  Specifies the mode of the operation.	You can pass
	  PropModeReplace, PropModePrepend, or PropModeAp-
	  pend.

data	  Specifies the property data.

nelements Specifies the number of elements of the specified
	  data format.
|__

The XChangeProperty function alters the property for the
specified window and causes the X server to generate a Prop-
ertyNotify event on that window.  XChangeProperty performs
the following:

o    If mode is PropModeReplace, XChangeProperty discards
     the previous property value and stores the new data.

o    If mode is PropModePrepend or PropModeAppend, XChange-
     Property inserts the specified data before the begin-
     ning of the existing data or onto the end of the exist-
     ing data, respectively.  The type and format must match



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     the existing property value, or a BadMatch error
     results.  If the property is undefined, it is treated
     as defined with the correct type and format with zero-
     length data.

If the specified format is 8, the property data must be a
char array.  If the specified format is 16, the property
data must be a short array.  If the specified format is 32,
the property data must be a long array.

The lifetime of a property is not tied to the storing
client.  Properties remain until explicitly deleted, until
the window is destroyed, or until the server resets.  For a
discussion of what happens when the connection to the X
server is closed, see section 2.6.  The maximum size of a
property is server dependent and can vary dynamically
depending on the amount of memory the server has available.
(If there is insufficient space, a BadAlloc error results.)

XChangeProperty can generate BadAlloc, BadAtom, BadMatch,
BadValue, and BadWindow errors.


To rotate a window's property list, use XRotateWindowProper-
ties.

__
|
XRotateWindowProperties(display, w, properties, num_prop, npositions)
      Display *display;
      Window w;
      Atom properties[];
      int num_prop;
      int npositions;


display   Specifies the connection to the X server.

w	  Specifies the window.

properties
	  Specifies the array of properties that are to be
	  rotated.

num_prop  Specifies the length of the properties array.

npositions
	  Specifies the rotation amount.
|__

The XRotateWindowProperties function allows you to rotate
properties on a window and causes the X server to generate
PropertyNotify events.	If the property names in the proper-
ties array are viewed as being numbered starting from zero



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and if there are num_prop property names in the list, then
the value associated with property name I becomes the value
associated with property name (I + npositions) mod N for all
I from zero to N - 1.  The effect is to rotate the states by
npositions places around the virtual ring of property names
(right for positive npositions, left for negative nposi-
tions).  If npositions mod N is nonzero, the X server gener-
ates a PropertyNotify event for each property in the order
that they are listed in the array.  If an atom occurs more
than once in the list or no property with that name is
defined for the window, a BadMatch error results.  If a
BadAtom or BadMatch error results, no properties are
changed.

XRotateWindowProperties can generate BadAtom, BadMatch, and
BadWindow errors.


To delete a property on a given window, use XDeleteProperty.
__
|
XDeleteProperty(display, w, property)
      Display *display;
      Window w;
      Atom property;


display   Specifies the connection to the X server.

w	  Specifies the window whose property you want to
	  delete.

property  Specifies the property name.
|__

The XDeleteProperty function deletes the specified property
only if the property was defined on the specified window and
causes the X server to generate a PropertyNotify event on
the window unless the property does not exist.

XDeleteProperty can generate BadAtom and BadWindow errors.

4.5.  Selections

Selections are one method used by applications to exchange
data.  By using the property mechanism, applications can
exchange data of arbitrary types and can negotiate the type
of the data.  A selection can be thought of as an indirect
property with a dynamic type.  That is, rather than having
the property stored in the X server, the property is main-
tained by some client (the owner).  A selection is global in
nature (considered to belong to the user but be maintained
by clients) rather than being private to a particular window
subhierarchy or a particular set of clients.



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Xlib provides functions that you can use to set, get, or
request conversion of selections.  This allows applications
to implement the notion of current selection, which requires
that notification be sent to applications when they no
longer own the selection.  Applications that support selec-
tion often highlight the current selection and so must be
informed when another application has acquired the selection
so that they can unhighlight the selection.

When a client asks for the contents of a selection, it spec-
ifies a selection target type.	This target type can be used
to control the transmitted representation of the contents.
For example, if the selection is ``the last thing the user
clicked on'' and that is currently an image, then the target
type might specify whether the contents of the image should
be sent in XY format or Z format.

The target type can also be used to control the class of
contents transmitted, for example, asking for the ``looks''
(fonts, line spacing, indentation, and so forth) of a para-
graph selection, not the text of the paragraph.  The target
type can also be used for other purposes.  The protocol does
not constrain the semantics.


To set the selection owner, use XSetSelectionOwner.
__
|
XSetSelectionOwner(display, selection, owner, time)
      Display *display;
      Atom selection;
      Window owner;
      Time time;


display   Specifies the connection to the X server.

selection Specifies the selection atom.

owner	  Specifies the owner of the specified selection
	  atom.  You can pass a window or None.

time	  Specifies the time.  You can pass either a times-
	  tamp or CurrentTime.
|__

The XSetSelectionOwner function changes the owner and last-
change time for the specified selection and has no effect if
the specified time is earlier than the current last-change
time of the specified selection or is later than the current
X server time.	Otherwise, the last-change time is set to
the specified time, with CurrentTime replaced by the current
server time.  If the owner window is specified as None, then
the owner of the selection becomes None (that is, no owner).



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Otherwise, the owner of the selection becomes the client
executing the request.

If the new owner (whether a client or None) is not the same
as the current owner of the selection and the current owner
is not None, the current owner is sent a SelectionClear
event.	If the client that is the owner of a selection is
later terminated (that is, its connection is closed) or if
the owner window it has specified in the request is later
destroyed, the owner of the selection automatically reverts
to None, but the last-change time is not affected.  The
selection atom is uninterpreted by the X server.  XGetSelec-
tionOwner returns the owner window, which is reported in
SelectionRequest and SelectionClear events.  Selections are
global to the X server.

XSetSelectionOwner can generate BadAtom and BadWindow
errors.


To return the selection owner, use XGetSelectionOwner.
__
|
Window XGetSelectionOwner(display, selection)
      Display *display;
      Atom selection;


display   Specifies the connection to the X server.

selection Specifies the selection atom whose owner you want
	  returned.
|__

The XGetSelectionOwner function returns the window ID asso-
ciated with the window that currently owns the specified
selection.  If no selection was specified, the function
returns the constant None.  If None is returned, there is no
owner for the selection.

XGetSelectionOwner can generate a BadAtom error.


To request conversion of a selection, use XConvertSelection.













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__
|
XConvertSelection(display, selection, target, property, requestor, time)
      Display *display;
      Atom selection, target;
      Atom property;
      Window requestor;
      Time time;


display   Specifies the connection to the X server.

selection Specifies the selection atom.

target	  Specifies the target atom.

property  Specifies the property name.	You also can pass
	  None.

requestor Specifies the requestor.

time	  Specifies the time.  You can pass either a times-
	  tamp or CurrentTime.
|__

XConvertSelection requests that the specified selection be
converted to the specified target type:

o    If the specified selection has an owner, the X server
     sends a SelectionRequest event to that owner.

o    If no owner for the specified selection exists, the X
     server generates a SelectionNotify event to the
     requestor with property None.

The arguments are passed on unchanged in either of the
events.  There are two predefined selection atoms: PRIMARY
and SECONDARY.

XConvertSelection can generate BadAtom and BadWindow errors.


















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			 Chapter 5

		Pixmap and Cursor Functions



Once you have connected to an X server, you can use the Xlib
functions to:

o    Create and free pixmaps

o    Create, recolor, and free cursors

5.1.  Creating and Freeing Pixmaps

Pixmaps can only be used on the screen on which they were
created.  Pixmaps are off-screen resources that are used for
various operations, such as defining cursors as tiling pat-
terns or as the source for certain raster operations.  Most
graphics requests can operate either on a window or on a
pixmap.  A bitmap is a single bit-plane pixmap.


To create a pixmap of a given size, use XCreatePixmap.
__
|
Pixmap XCreatePixmap(display, d, width, height, depth)
      Display *display;
      Drawable d;
      unsigned int width, height;
      unsigned int depth;


display   Specifies the connection to the X server.

d	  Specifies which screen the pixmap is created on.

width
height	  Specify the width and height, which define the
	  dimensions of the pixmap.

depth	  Specifies the depth of the pixmap.
|__

The XCreatePixmap function creates a pixmap of the width,
height, and depth you specified and returns a pixmap ID that
identifies it.	It is valid to pass an InputOnly window to
the drawable argument.	The width and height arguments must
be nonzero, or a BadValue error results.  The depth argument
must be one of the depths supported by the screen of the
specified drawable, or a BadValue error results.




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The server uses the specified drawable to determine on which
screen to create the pixmap.  The pixmap can be used only on
this screen and only with other drawables of the same depth
(see XCopyPlane for an exception to this rule).  The initial
contents of the pixmap are undefined.

XCreatePixmap can generate BadAlloc, BadDrawable, and Bad-
Value errors.


To free all storage associated with a specified pixmap, use
XFreePixmap.
__
|
XFreePixmap(display, pixmap)
      Display *display;
      Pixmap pixmap;


display   Specifies the connection to the X server.

pixmap	  Specifies the pixmap.
|__

The XFreePixmap function first deletes the association
between the pixmap ID and the pixmap.  Then, the X server
frees the pixmap storage when there are no references to it.
The pixmap should never be referenced again.

XFreePixmap can generate a BadPixmap error.

5.2.  Creating, Recoloring, and Freeing Cursors

Each window can have a different cursor defined for it.
Whenever the pointer is in a visible window, it is set to
the cursor defined for that window.  If no cursor was
defined for that window, the cursor is the one defined for
the parent window.

From X's perspective, a cursor consists of a cursor source,
mask, colors, and a hotspot.  The mask pixmap determines the
shape of the cursor and must be a depth of one.  The source
pixmap must have a depth of one, and the colors determine
the colors of the source.  The hotspot defines the point on
the cursor that is reported when a pointer event occurs.
There may be limitations imposed by the hardware on cursors
as to size and whether a mask is implemented.
XQueryBestCursor can be used to find out what sizes are pos-
sible.	There is a standard font for creating cursors, but
Xlib provides functions that you can use to create cursors
from an arbitrary font or from bitmaps.


To create a cursor from the standard cursor font, use



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XCreateFontCursor.
__
|
#include <X11/cursorfont.h>
Cursor XCreateFontCursor(display, shape)
      Display *display;
      unsigned int shape;


display   Specifies the connection to the X server.

shape	  Specifies the shape of the cursor.
|__

X provides a set of standard cursor shapes in a special font
named cursor.  Applications are encouraged to use this
interface for their cursors because the font can be cus-
tomized for the individual display type.  The shape argument
specifies which glyph of the standard fonts to use.

The hotspot comes from the information stored in the cursor
font.  The initial colors of a cursor are a black foreground
and a white background (see XRecolorCursor).  For further
information about cursor shapes, see appendix B.

XCreateFontCursor can generate BadAlloc and BadValue errors.


To create a cursor from font glyphs, use XCreateGlyphCursor.




























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__
|
Cursor XCreateGlyphCursor(display, source_font, mask_font, source_char, mask_char,
			   foreground_color, background_color)
      Display *display;
      Font source_font, mask_font;
      unsigned int source_char, mask_char;
      XColor *foreground_color;
      XColor *background_color;


display   Specifies the connection to the X server.

source_font
	  Specifies the font for the source glyph.

mask_font Specifies the font for the mask glyph or None.

source_char
	  Specifies the character glyph for the source.

mask_char Specifies the glyph character for the mask.

foreground_color
	  Specifies the RGB values for the foreground of the
	  source.

background_color
	  Specifies the RGB values for the background of the
	  source.
|__

The XCreateGlyphCursor function is similar to XCre-
atePixmapCursor except that the source and mask bitmaps are
obtained from the specified font glyphs.  The source_char
must be a defined glyph in source_font, or a BadValue error
results.  If mask_font is given, mask_char must be a defined
glyph in mask_font, or a BadValue error results.  The
mask_font and character are optional.  The origins of the
source_char and mask_char (if defined) glyphs are positioned
coincidently and define the hotspot.  The source_char and
mask_char need not have the same bounding box metrics, and
there is no restriction on the placement of the hotspot rel-
ative to the bounding boxes.  If no mask_char is given, all
pixels of the source are displayed.  You can free the fonts
immediately by calling XFreeFont if no further explicit ref-
erences to them are to be made.

For 2-byte matrix fonts, the 16-bit value should be formed
with the byte1 member in the most significant byte and the
byte2 member in the least significant byte.

XCreateGlyphCursor can generate BadAlloc, BadFont, and Bad-
Value errors.




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To create a cursor from two bitmaps, use XCreatePixmapCur-
sor.
__
|
Cursor XCreatePixmapCursor(display, source, mask, foreground_color, background_color, x, y)
      Display *display;
      Pixmap source;
      Pixmap mask;
      XColor *foreground_color;
      XColor *background_color;
      unsigned int x, y;


display   Specifies the connection to the X server.

source	  Specifies the shape of the source cursor.

mask	  Specifies the cursor's source bits to be displayed
	  or None.

foreground_color
	  Specifies the RGB values for the foreground of the
	  source.

background_color
	  Specifies the RGB values for the background of the
	  source.

x
y	  Specify the x and y coordinates, which indicate
	  the hotspot relative to the source's origin.
|__

The XCreatePixmapCursor function creates a cursor and
returns the cursor ID associated with it.  The foreground
and background RGB values must be specified using fore-
ground_color and background_color, even if the X server only
has a StaticGray or GrayScale screen.  The foreground color
is used for the pixels set to 1 in the source, and the back-
ground color is used for the pixels set to 0.  Both source
and mask, if specified, must have depth one (or a BadMatch
error results) but can have any root.  The mask argument
defines the shape of the cursor.  The pixels set to 1 in the
mask define which source pixels are displayed, and the pix-
els set to 0 define which pixels are ignored.  If no mask is
given, all pixels of the source are displayed.	The mask, if
present, must be the same size as the pixmap defined by the
source argument, or a BadMatch error results.  The hotspot
must be a point within the source, or a BadMatch error
results.

The components of the cursor can be transformed arbitrarily
to meet display limitations.  The pixmaps can be freed imme-
diately if no further explicit references to them are to be



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made.  Subsequent drawing in the source or mask pixmap has
an undefined effect on the cursor.  The X server might or
might not make a copy of the pixmap.

XCreatePixmapCursor can generate BadAlloc and BadPixmap
errors.


To determine useful cursor sizes, use XQueryBestCursor.
__
|
Status XQueryBestCursor(display, d, width, height, width_return, height_return)
      Display *display;
      Drawable d;
      unsigned int width, height;
      unsigned int *width_return, *height_return;


display   Specifies the connection to the X server.

d	  Specifies the drawable, which indicates the
	  screen.

width
height	  Specify the width and height of the cursor that
	  you want the size information for.

width_return
height_return
	  Return the best width and height that is closest
	  to the specified width and height.
|__

Some displays allow larger cursors than other displays.  The
XQueryBestCursor function provides a way to find out what
size cursors are actually possible on the display.  It
returns the largest size that can be displayed.  Applica-
tions should be prepared to use smaller cursors on displays
that cannot support large ones.

XQueryBestCursor can generate a BadDrawable error.


To change the color of a given cursor, use XRecolorCursor.













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__
|
XRecolorCursor(display, cursor, foreground_color, background_color)
      Display *display;
      Cursor cursor;
      XColor *foreground_color, *background_color;


display   Specifies the connection to the X server.

cursor	  Specifies the cursor.

foreground_color
	  Specifies the RGB values for the foreground of the
	  source.

background_color
	  Specifies the RGB values for the background of the
	  source.
|__

The XRecolorCursor function changes the color of the speci-
fied cursor, and if the cursor is being displayed on a
screen, the change is visible immediately.  The pixel mem-
bers of the XColor structures are ignored; only the RGB val-
ues are used.

XRecolorCursor can generate a BadCursor error.


To free (destroy) a given cursor, use XFreeCursor.
__
|
XFreeCursor(display, cursor)
      Display *display;
      Cursor cursor;


display   Specifies the connection to the X server.

cursor	  Specifies the cursor.
|__

The XFreeCursor function deletes the association between the
cursor resource ID and the specified cursor.  The cursor
storage is freed when no other resource references it.	The
specified cursor ID should not be referred to again.

XFreeCursor can generate a BadCursor error.









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			 Chapter 6

		 Color Management Functions



Each X window always has an associated colormap that pro-
vides a level of indirection between pixel values and colors
displayed on the screen.  Xlib provides functions that you
can use to manipulate a colormap.  The X protocol defines
colors using values in the RGB color space.  The RGB color
space is device dependent; rendering an RGB value on differ-
ing output devices typically results in different colors.
Xlib also provides a means for clients to specify color
using device-independent color spaces for consistent results
across devices.  Xlib supports device-independent color
spaces derivable from the CIE XYZ color space.	This
includes the CIE XYZ, xyY, L*u*v*, and L*a*b* color spaces
as well as the TekHVC color space.

This chapter discusses how to:

o    Create, copy, and destroy a colormap

o    Specify colors by name or value

o    Allocate, modify, and free color cells

o    Read entries in a colormap

o    Convert between color spaces

o    Control aspects of color conversion

o    Query the color gamut of a screen

o    Add new color spaces

All functions, types, and symbols in this chapter with the
prefix ``Xcms'' are defined in <X11/Xcms.h>.  The remaining
functions and types are defined in <X11/Xlib.h>.

Functions in this chapter manipulate the representation of
color on the screen.  For each possible value that a pixel
can take in a window, there is a color cell in the colormap.
For example, if a window is 4 bits deep, pixel values 0
through 15 are defined.  A colormap is a collection of color
cells.	A color cell consists of a triple of red, green, and
blue (RGB) values.  The hardware imposes limits on the num-
ber of significant bits in these values.  As each pixel is
read out of display memory, the pixel is looked up in a col-
ormap.	The RGB value of the cell determines what color is



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displayed on the screen.  On a grayscale display with a
black-and-white monitor, the values are combined to deter-
mine the brightness on the screen.

Typically, an application allocates color cells or sets of
color cells to obtain the desired colors.  The client can
allocate read-only cells.  In which case, the pixel values
for these colors can be shared among multiple applications,
and the RGB value of the cell cannot be changed.  If the
client allocates read/write cells, they are exclusively
owned by the client, and the color associated with the pixel
value can be changed at will.  Cells must be allocated (and,
if read/write, initialized with an RGB value) by a client to
obtain desired colors.	The use of pixel value for an unal-
located cell results in an undefined color.

Because colormaps are associated with windows, X supports
displays with multiple colormaps and, indeed, different
types of colormaps.  If there are insufficient colormap
resources in the display, some windows will display in their
true colors, and others will display with incorrect colors.
A window manager usually controls which windows are dis-
played in their true colors if more than one colormap is
required for the color resources the applications are using.
At any time, there is a set of installed colormaps for a
screen.  Windows using one of the installed colormaps dis-
play with true colors, and windows using other colormaps
generally display with incorrect colors.  You can control
the set of installed colormaps by using XInstallColormap and
XUninstallColormap.

Colormaps are local to a particular screen.  Screens always
have a default colormap, and programs typically allocate
cells out of this colormap.  Generally, you should not write
applications that monopolize color resources.  Although some
hardware supports multiple colormaps installed at one time,
many of the hardware displays built today support only a
single installed colormap, so the primitives are written to
encourage sharing of colormap entries between applications.

The DefaultColormap macro returns the default colormap.  The
DefaultVisual macro returns the default visual type for the
specified screen.  Possible visual types are StaticGray,
GrayScale, StaticColor, PseudoColor, TrueColor, or Direct-
Color (see section 3.1).

6.1.  Color Structures

Functions that operate only on RGB color space values use an
XColor structure, which contains:







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__
|
typedef struct {
     unsigned long pixel;/* pixel value */
     unsigned short red, green, blue;/* rgb values */
     char flags;	 /* DoRed, DoGreen, DoBlue */
     char pad;
} XColor;

|__

The red, green, and blue values are always in the range 0 to
65535 inclusive, independent of the number of bits actually
used in the display hardware.  The server scales these val-
ues down to the range used by the hardware.  Black is repre-
sented by (0,0,0), and white is represented by
(65535,65535,65535).  In some functions, the flags member
controls which of the red, green, and blue members is used
and can be the inclusive OR of zero or more of DoRed,
DoGreen, and DoBlue.


Functions that operate on all color space values use an Xcm-
sColor structure.  This structure contains a union of sub-
structures, each supporting color specification encoding for
a particular color space.  Like the XColor structure, the
XcmsColor structure contains pixel and color specification
information (the spec member in the XcmsColor structure).
__
|

typedef unsigned long XcmsColorFormat;/* Color Specification Format */

typedef struct {
     union {
	  XcmsRGB RGB;
	  XcmsRGBi RGBi;
	  XcmsCIEXYZ CIEXYZ;
	  XcmsCIEuvY CIEuvY;
	  XcmsCIExyY CIExyY;
	  XcmsCIELab CIELab;
	  XcmsCIELuv CIELuv;
	  XcmsTekHVC TekHVC;
	  XcmsPad Pad;
     } spec;
     unsigned long pixel;
     XcmsColorFormat format;
} XcmsColor;		 /* Xcms Color Structure */

|__

Because the color specification can be encoded for the vari-
ous color spaces, encoding for the spec member is identified
by the format member, which is of type XcmsColorFormat.  The
following macros define standard formats.



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__
|
#define   XcmsUndefined-     0x00000000
	  Format
#define   XcmsCIEXYZFormat   0x00000001       /* CIE XYZ */
#define   XcmsCIEuvYFormat   0x00000002       /* CIE u'v'Y */
#define   XcmsCIExyYFormat   0x00000003       /* CIE xyY */
#define   XcmsCIELabFormat   0x00000004       /* CIE L*a*b*
					      */
#define   XcmsCIELuvFormat   0x00000005       /* CIE L*u*v*
					      */
#define   XcmsTekHVCFormat   0x00000006       /* TekHVC */
#define   XcmsRGBFormat      0x80000000       /* RGB Device
					      */
#define   XcmsRGBiFormat     0x80000001       /* RGB Inten-
					      sity */

|__

Formats for device-independent color spaces are distinguish-
able from those for device-dependent spaces by the 32nd bit.
If this bit is set, it indicates that the color specifica-
tion is in a device-dependent form; otherwise, it is in a
device-independent form.  If the 31st bit is set, this indi-
cates that the color space has been added to Xlib at run
time (see section 6.12.4).  The format value for a color
space added at run time may be different each time the pro-
gram is executed.  If references to such a color space must
be made outside the client (for example, storing a color
specification in a file), then reference should be made by
color space string prefix (see XcmsFormatOfPrefix and Xcm-
sPrefixOfFormat).

Data types that describe the color specification encoding
for the various color spaces are defined as follows:























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__
|

typedef double XcmsFloat;

typedef struct {
     unsigned short red; /* 0x0000 to 0xffff */
     unsigned short green;/* 0x0000 to 0xffff */
     unsigned short blue;/* 0x0000 to 0xffff */
} XcmsRGB;		 /* RGB Device */



typedef struct {
     XcmsFloat red;	 /* 0.0 to 1.0 */
     XcmsFloat green;	 /* 0.0 to 1.0 */
     XcmsFloat blue;	 /* 0.0 to 1.0 */
} XcmsRGBi;		 /* RGB Intensity */



typedef struct {
     XcmsFloat X;
     XcmsFloat Y;	 /* 0.0 to 1.0 */
     XcmsFloat Z;
} XcmsCIEXYZ;		 /* CIE XYZ */



typedef struct {
     XcmsFloat u_prime;  /* 0.0 to ~0.6 */
     XcmsFloat v_prime;  /* 0.0 to ~0.6 */
     XcmsFloat Y;	 /* 0.0 to 1.0 */
} XcmsCIEuvY;		 /* CIE u'v'Y */



typedef struct {
     XcmsFloat x;	 /* 0.0 to ~.75 */
     XcmsFloat y;	 /* 0.0 to ~.85 */
     XcmsFloat Y;	 /* 0.0 to 1.0 */
} XcmsCIExyY;		 /* CIE xyY */



typedef struct {
     XcmsFloat L_star;	 /* 0.0 to 100.0 */
     XcmsFloat a_star;
     XcmsFloat b_star;
} XcmsCIELab;		 /* CIE L*a*b* */



typedef struct {
     XcmsFloat L_star;	 /* 0.0 to 100.0 */



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     XcmsFloat u_star;
     XcmsFloat v_star;
} XcmsCIELuv;		 /* CIE L*u*v* */



typedef struct {
     XcmsFloat H;	 /* 0.0 to 360.0 */
     XcmsFloat V;	 /* 0.0 to 100.0 */
     XcmsFloat C;	 /* 0.0 to 100.0 */
} XcmsTekHVC;		 /* TekHVC */



typedef struct {
     XcmsFloat pad0;
     XcmsFloat pad1;
     XcmsFloat pad2;
     XcmsFloat pad3;
} XcmsPad;		 /* four doubles */

|__

The device-dependent formats provided allow color specifica-
tion in:

o    RGB Intensity (XcmsRGBi)

     Red, green, and blue linear intensity values, floating-
     point values from 0.0 to 1.0, where 1.0 indicates full
     intensity, 0.5 half intensity, and so on.

o    RGB Device (XcmsRGB)

     Red, green, and blue values appropriate for the speci-
     fied output device.  XcmsRGB values are of type
     unsigned short, scaled from 0 to 65535 inclusive, and
     are interchangeable with the red, green, and blue val-
     ues in an XColor structure.

It is important to note that RGB Intensity values are not
gamma corrected values.  In contrast, RGB Device values gen-
erated as a result of converting color specifications are
always gamma corrected, and RGB Device values acquired as a
result of querying a colormap or passed in by the client are
assumed by Xlib to be gamma corrected.	The term RGB value
in this manual always refers to an RGB Device value.

6.2.  Color Strings

Xlib provides a mechanism for using string names for colors.
A color string may either contain an abstract color name or
a numerical color specification.  Color strings are case-
insensitive.



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Color strings are used in the following functions:

o    XAllocNamedColor

o    XcmsAllocNamedColor

o    XLookupColor

o    XcmsLookupColor

o    XParseColor

o    XStoreNamedColor

Xlib supports the use of abstract color names, for example,
red or blue.  A value for this abstract name is obtained by
searching one or more color name databases.  Xlib first
searches zero or more client-side databases; the number,
location, and content of these databases is implementation-
dependent and might depend on the current locale.  If the
name is not found, Xlib then looks for the color in the X
server's database.  If the color name is not in the Host
Portable Character Encoding, the result is implementation-
dependent.

A numerical color specification consists of a color space
name and a set of values in the following syntax:

__
|
<color_space_name>:<value>/.../<value>

|__

The following are examples of valid color strings.


"CIEXYZ:0.3227/0.28133/0.2493"
"RGBi:1.0/0.0/0.0"
"rgb:00/ff/00"
"CIELuv:50.0/0.0/0.0"

The syntax and semantics of numerical specifications are
given for each standard color space in the following sec-
tions.

6.2.1.	RGB Device String Specification

An RGB Device specification is identified by the prefix
``rgb:'' and conforms to the following syntax:


rgb:<red>/<green>/<blue>




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    <red>, <green>, <blue> := h | hh | hhh | hhhh
    h := single hexadecimal digits (case insignificant)


Note that h indicates the value scaled in 4 bits, hh the
value scaled in 8 bits, hhh the value scaled in 12 bits, and
hhhh the value scaled in 16 bits, respectively.

Typical examples are the strings ``rgb:ea/75/52'' and
``rgb:ccc/320/320'', but mixed numbers of hexadecimal digit
strings (``rgb:ff/a5/0'' and ``rgb:ccc/32/0'') are also
allowed.

For backward compatibility, an older syntax for RGB Device
is supported, but its continued use is not encouraged.	The
syntax is an initial sharp sign character followed by a
numeric specification, in one of the following formats:


#RGB		    (4 bits each)
#RRGGBB 	    (8 bits each)
#RRRGGGBBB	    (12 bits each)
#RRRRGGGGBBBB	    (16 bits each)


The R, G, and B represent single hexadecimal digits.  When
fewer than 16 bits each are specified, they represent the
most significant bits of the value (unlike the ``rgb:'' syn-
tax, in which values are scaled).  For example, the string
``#3a7'' is the same as ``#3000a0007000''.

6.2.2.	RGB Intensity String Specification

An RGB intensity specification is identified by the prefix
``rgbi:'' and conforms to the following syntax:


rgbi:<red>/<green>/<blue>


Note that red, green, and blue are floating-point values
between 0.0 and 1.0, inclusive.  The input format for these
values is an optional sign, a string of numbers possibly
containing a decimal point, and an optional exponent field
containing an E or e followed by a possibly signed integer
string.

6.2.3.	Device-Independent String Specifications

The standard device-independent string specifications have
the following syntax:


CIEXYZ:<X>/<Y>/<Z>



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CIEuvY:<u>/<v>/<Y>
CIExyY:<x>/<y>/<Y>
CIELab:<L>/<a>/<b>
CIELuv:<L>/<u>/<v>
TekHVC:<H>/<V>/<C>


All of the values (C, H, V, X, Y, Z, a, b, u, v, y, x) are
floating-point values.	The syntax for these values is an
optional plus or minus sign, a string of digits possibly
containing a decimal point, and an optional exponent field
consisting of an ``E'' or ``e'' followed by an optional plus
or minus followed by a string of digits.

6.3.  Color Conversion Contexts and Gamut Mapping

When Xlib converts device-independent color specifications
into device-dependent specifications and vice versa, it uses
knowledge about the color limitations of the screen hard-
ware.  This information, typically called the device pro-
file, is available in a Color Conversion Context (CCC).

Because a specified color may be outside the color gamut of
the target screen and the white point associated with the
color specification may differ from the white point inherent
to the screen, Xlib applies gamut mapping when it encounters
certain conditions:

o    Gamut compression occurs when conversion of device-
     independent color specifications to device-dependent
     color specifications results in a color out of the tar-
     get screen's gamut.

o    White adjustment occurs when the inherent white point
     of the screen differs from the white point assumed by
     the client.

Gamut handling methods are stored as callbacks in the CCC,
which in turn are used by the color space conversion rou-
tines.	Client data is also stored in the CCC for each call-
back.  The CCC also contains the white point the client
assumes to be associated with color specifications (that is,
the Client White Point).  The client can specify the gamut
handling callbacks and client data as well as the Client
White Point.  Xlib does not preclude the X client from per-
forming other forms of gamut handling (for example, gamut
expansion); however, Xlib does not provide direct support
for gamut handling other than white adjustment and gamut
compression.

Associated with each colormap is an initial CCC transpar-
ently generated by Xlib.  Therefore, when you specify a col-
ormap as an argument to an Xlib function, you are indirectly
specifying a CCC.  There is a default CCC associated with



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each screen.  Newly created CCCs inherit attributes from the
default CCC, so the default CCC attributes can be modified
to affect new CCCs.

Xcms functions in which gamut mapping can occur return Sta-
tus and have specific status values defined for them, as
follows:

o    XcmsFailure indicates that the function failed.

o    XcmsSuccess indicates that the function succeeded.  In
     addition, if the function performed any color conver-
     sion, the colors did not need to be compressed.

o    XcmsSuccessWithCompression indicates the function per-
     formed color conversion and at least one of the colors
     needed to be compressed.  The gamut compression method
     is determined by the gamut compression procedure in the
     CCC that is specified directly as a function argument
     or in the CCC indirectly specified by means of the col-
     ormap argument.

6.4.  Creating, Copying, and Destroying Colormaps

To create a colormap for a screen, use XCreateColormap.
__
|
Colormap XCreateColormap(display, w, visual, alloc)
      Display *display;
      Window w;
      Visual *visual;
      int alloc;


display   Specifies the connection to the X server.

w	  Specifies the window on whose screen you want to
	  create a colormap.

visual	  Specifies a visual type supported on the screen.
	  If the visual type is not one supported by the
	  screen, a BadMatch error results.

alloc	  Specifies the colormap entries to be allocated.
	  You can pass AllocNone or AllocAll.
|__

The XCreateColormap function creates a colormap of the spec-
ified visual type for the screen on which the specified win-
dow resides and returns the colormap ID associated with it.
Note that the specified window is only used to determine the
screen.





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The initial values of the colormap entries are undefined for
the visual classes GrayScale, PseudoColor, and DirectColor.
For StaticGray, StaticColor, and TrueColor, the entries have
defined values, but those values are specific to the visual
and are not defined by X.  For StaticGray, StaticColor, and
TrueColor, alloc must be AllocNone, or a BadMatch error
results.  For the other visual classes, if alloc is Alloc-
None, the colormap initially has no allocated entries, and
clients can allocate them.  For information about the visual
types, see section 3.1.

If alloc is AllocAll, the entire colormap is allocated
writable.  The initial values of all allocated entries are
undefined.  For GrayScale and PseudoColor, the effect is as
if an XAllocColorCells call returned all pixel values from
zero to N - 1, where N is the colormap entries value in the
specified visual.  For DirectColor, the effect is as if an
XAllocColorPlanes call returned a pixel value of zero and
red_mask, green_mask, and blue_mask values containing the
same bits as the corresponding masks in the specified
visual.  However, in all cases, none of these entries can be
freed by using XFreeColors.

XCreateColormap can generate BadAlloc, BadMatch, BadValue,
and BadWindow errors.


To create a new colormap when the allocation out of a previ-
ously shared colormap has failed because of resource exhaus-
tion, use XCopyColormapAndFree.
__
|
Colormap XCopyColormapAndFree(display, colormap)
      Display *display;
      Colormap colormap;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.
|__

The XCopyColormapAndFree function creates a colormap of the
same visual type and for the same screen as the specified
colormap and returns the new colormap ID.  It also moves all
of the client's existing allocation from the specified col-
ormap to the new colormap with their color values intact and
their read-only or writable characteristics intact and frees
those entries in the specified colormap.  Color values in
other entries in the new colormap are undefined.  If the
specified colormap was created by the client with alloc set
to AllocAll, the new colormap is also created with AllocAll,
all color values for all entries are copied from the speci-
fied colormap, and then all entries in the specified



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colormap are freed.  If the specified colormap was not cre-
ated by the client with AllocAll, the allocations to be
moved are all those pixels and planes that have been allo-
cated by the client using XAllocColor, XAllocNamedColor,
XAllocColorCells, or XAllocColorPlanes and that have not
been freed since they were allocated.

XCopyColormapAndFree can generate BadAlloc and BadColor
errors.


To destroy a colormap, use XFreeColormap.
__
|
XFreeColormap(display, colormap)
      Display *display;
      Colormap colormap;


display   Specifies the connection to the X server.

colormap  Specifies the colormap that you want to destroy.
|__

The XFreeColormap function deletes the association between
the colormap resource ID and the colormap and frees the col-
ormap storage.	However, this function has no effect on the
default colormap for a screen.	If the specified colormap is
an installed map for a screen, it is uninstalled (see XUnin-
stallColormap).  If the specified colormap is defined as the
colormap for a window (by XCreateWindow, XSetWindowColormap,
or XChangeWindowAttributes), XFreeColormap changes the col-
ormap associated with the window to None and generates a
ColormapNotify event.  X does not define the colors dis-
played for a window with a colormap of None.

XFreeColormap can generate a BadColor error.

6.5.  Mapping Color Names to Values


To map a color name to an RGB value, use XLookupColor.















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__
|
Status XLookupColor(display, colormap, color_name, exact_def_return, screen_def_return)
      Display *display;
      Colormap colormap;
      char *color_name;
      XColor *exact_def_return, *screen_def_return;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

color_name
	  Specifies the color name string (for example, red)
	  whose color definition structure you want
	  returned.

exact_def_return
	  Returns the exact RGB values.

screen_def_return
	  Returns the closest RGB values provided by the
	  hardware.
|__

The XLookupColor function looks up the string name of a
color with respect to the screen associated with the speci-
fied colormap.	It returns both the exact color values and
the closest values provided by the screen with respect to
the visual type of the specified colormap.  If the color
name is not in the Host Portable Character Encoding, the
result is implementation-dependent.  Use of uppercase or
lowercase does not matter.  XLookupColor returns nonzero if
the name is resolved; otherwise, it returns zero.

XLookupColor can generate a BadColor error.


To map a color name to the exact RGB value, use XParseColor.


















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__
|
Status XParseColor(display, colormap, spec, exact_def_return)
	Display *display;
	Colormap colormap;
	char *spec;
	XColor *exact_def_return;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

spec	  Specifies the color name string; case is ignored.

exact_def_return
	  Returns the exact color value for later use and
	  sets the DoRed, DoGreen, and DoBlue flags.
|__

The XParseColor function looks up the string name of a color
with respect to the screen associated with the specified
colormap.  It returns the exact color value.  If the color
name is not in the Host Portable Character Encoding, the
result is implementation-dependent.  Use of uppercase or
lowercase does not matter.  XParseColor returns nonzero if
the name is resolved; otherwise, it returns zero.

XParseColor can generate a BadColor error.


To map a color name to a value in an arbitrary color space,
use XcmsLookupColor.

























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__
|
Status XcmsLookupColor(display, colormap, color_string, color_exact_return, color_screen_return,
			       result_format)
      Display *display;
      Colormap colormap;
      char *color_string;
      XcmsColor *color_exact_return, *color_screen_return;
      XcmsColorFormat result_format;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

color_string
	  Specifies the color string.

color_exact_return
	  Returns the color specification parsed from the
	  color string or parsed from the corresponding
	  string found in a color-name database.

color_screen_return
	  Returns the color that can be reproduced on the
	  screen.

result_format
	  Specifies the color format for the returned color
	  specifications (color_screen_return and
	  color_exact_return arguments).  If the format is
	  XcmsUndefinedFormat and the color string contains
	  a numerical color specification, the specification
	  is returned in the format used in that numerical
	  color specification.	If the format is XcmsUnde-
	  finedFormat and the color string contains a color
	  name, the specification is returned in the format
	  used to store the color in the database.
|__

The XcmsLookupColor function looks up the string name of a
color with respect to the screen associated with the speci-
fied colormap.	It returns both the exact color values and
the closest values provided by the screen with respect to
the visual type of the specified colormap.  The values are
returned in the format specified by result_format.  If the
color name is not in the Host Portable Character Encoding,
the result is implementation-dependent.  Use of uppercase or
lowercase does not matter.  XcmsLookupColor returns XcmsSuc-
cess or XcmsSuccessWithCompression if the name is resolved;
otherwise, it returns XcmsFailure.  If XcmsSuccessWithCom-
pression is returned, the color specification returned in
color_screen_return is the result of gamut compression.





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6.6.  Allocating and Freeing Color Cells

There are two ways of allocating color cells: explicitly as
read-only entries, one pixel value at a time, or read/write,
where you can allocate a number of color cells and planes
simultaneously.  A read-only cell has its RGB value set by
the server.  Read/write cells do not have defined colors
initially; functions described in the next section must be
used to store values into them.  Although it is possible for
any client to store values into a read/write cell allocated
by another client, read/write cells normally should be con-
sidered private to the client that allocated them.

Read-only colormap cells are shared among clients.  The
server counts each allocation and freeing of the cell by
clients.  When the last client frees a shared cell, the cell
is finally deallocated.  If a single client allocates the
same read-only cell multiple times, the server counts each
such allocation, not just the first one.


To allocate a read-only color cell with an RGB value, use
XAllocColor.
__
|
Status XAllocColor(display, colormap, screen_in_out)
      Display *display;
      Colormap colormap;
      XColor *screen_in_out;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

screen_in_out
	  Specifies and returns the values actually used in
	  the colormap.
|__

The XAllocColor function allocates a read-only colormap
entry corresponding to the closest RGB value supported by
the hardware.  XAllocColor returns the pixel value of the
color closest to the specified RGB elements supported by the
hardware and returns the RGB value actually used.  The cor-
responding colormap cell is read-only.	In addition, XAlloc-
Color returns nonzero if it succeeded or zero if it failed.
Multiple clients that request the same effective RGB value
can be assigned the same read-only entry, thus allowing
entries to be shared.  When the last client deallocates a
shared cell, it is deallocated.  XAllocColor does not use or
affect the flags in the XColor structure.





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XAllocColor can generate a BadColor error.


To allocate a read-only color cell with a color in arbitrary
format, use XcmsAllocColor.
__
|
Status XcmsAllocColor(display, colormap, color_in_out, result_format)
      Display *display;
      Colormap colormap;
      XcmsColor *color_in_out;
      XcmsColorFormat result_format;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

color_in_out
	  Specifies the color to allocate and returns the
	  pixel and color that is actually used in the col-
	  ormap.

result_format
	  Specifies the color format for the returned color
	  specification.
|__

The XcmsAllocColor function is similar to XAllocColor except
the color can be specified in any format.  The XcmsAlloc-
Color function ultimately calls XAllocColor to allocate a
read-only color cell (colormap entry) with the specified
color.	XcmsAllocColor first converts the color specified to
an RGB value and then passes this to XAllocColor.  XcmsAl-
locColor returns the pixel value of the color cell and the
color specification actually allocated.  This returned color
specification is the result of converting the RGB value
returned by XAllocColor into the format specified with the
result_format argument.  If there is no interest in a
returned color specification, unnecessary computation can be
bypassed if result_format is set to XcmsRGBFormat.  The cor-
responding colormap cell is read-only.	If this routine
returns XcmsFailure, the color_in_out color specification is
left unchanged.

XcmsAllocColor can generate a BadColor error.


To allocate a read-only color cell using a color name and
return the closest color supported by the hardware in RGB
format, use XAllocNamedColor.






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__
|
Status XAllocNamedColor(display, colormap, color_name, screen_def_return, exact_def_return)
      Display *display;
      Colormap colormap;
      char *color_name;
      XColor *screen_def_return, *exact_def_return;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

color_name
	  Specifies the color name string (for example, red)
	  whose color definition structure you want
	  returned.

screen_def_return
	  Returns the closest RGB values provided by the
	  hardware.

exact_def_return
	  Returns the exact RGB values.
|__

The XAllocNamedColor function looks up the named color with
respect to the screen that is associated with the specified
colormap.  It returns both the exact database definition and
the closest color supported by the screen.  The allocated
color cell is read-only.  The pixel value is returned in
screen_def_return.  If the color name is not in the Host
Portable Character Encoding, the result is implementation-
dependent.  Use of uppercase or lowercase does not matter.
If screen_def_return and exact_def_return point to the same
structure, the pixel field will be set correctly, but the
color values are undefined.  XAllocNamedColor returns
nonzero if a cell is allocated; otherwise, it returns zero.

XAllocNamedColor can generate a BadColor error.


To allocate a read-only color cell using a color name and
return the closest color supported by the hardware in an
arbitrary format, use XcmsAllocNamedColor.













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__
|
Status XcmsAllocNamedColor(display, colormap, color_string, color_screen_return, color_exact_return,
			    result_format)
      Display *display;
      Colormap colormap;
      char *color_string;
      XcmsColor *color_screen_return;
      XcmsColor *color_exact_return;
      XcmsColorFormat result_format;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

color_string
	  Specifies the color string whose color definition
	  structure is to be returned.

color_screen_return
	  Returns the pixel value of the color cell and
	  color specification that actually is stored for
	  that cell.

color_exact_return
	  Returns the color specification parsed from the
	  color string or parsed from the corresponding
	  string found in a color-name database.

result_format
	  Specifies the color format for the returned color
	  specifications (color_screen_return and
	  color_exact_return arguments).  If the format is
	  XcmsUndefinedFormat and the color string contains
	  a numerical color specification, the specification
	  is returned in the format used in that numerical
	  color specification.	If the format is XcmsUnde-
	  finedFormat and the color string contains a color
	  name, the specification is returned in the format
	  used to store the color in the database.
|__

The XcmsAllocNamedColor function is similar to XAllocNamed-
Color except that the color returned can be in any format
specified.  This function ultimately calls XAllocColor to
allocate a read-only color cell with the color specified by
a color string.  The color string is parsed into an Xcms-
Color structure (see XcmsLookupColor), converted to an RGB
value, and finally passed to XAllocColor.  If the color name
is not in the Host Portable Character Encoding, the result
is implementation-dependent.  Use of uppercase or lowercase
does not matter.





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This function returns both the color specification as a
result of parsing (exact specification) and the actual color
specification stored (screen specification).  This screen
specification is the result of converting the RGB value
returned by XAllocColor into the format specified in
result_format.	If there is no interest in a returned color
specification, unnecessary computation can be bypassed if
result_format is set to XcmsRGBFormat.	If
color_screen_return and color_exact_return point to the same
structure, the pixel field will be set correctly, but the
color values are undefined.

XcmsAllocNamedColor can generate a BadColor error.


To allocate read/write color cell and color plane combina-
tions for a PseudoColor model, use XAllocColorCells.
__
|
Status XAllocColorCells(display, colormap, contig, plane_masks_return, nplanes,
			  pixels_return, npixels)
      Display *display;
      Colormap colormap;
      Bool contig;
      unsigned long plane_masks_return[];
      unsigned int nplanes;
      unsigned long pixels_return[];
      unsigned int npixels;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

contig	  Specifies a Boolean value that indicates whether
	  the planes must be contiguous.

plane_mask_return
	  Returns an array of plane masks.

nplanes   Specifies the number of plane masks that are to be
	  returned in the plane masks array.

pixels_return
	  Returns an array of pixel values.

npixels   Specifies the number of pixel values that are to
	  be returned in the pixels_return array.
|__

The XAllocColorCells function allocates read/write color
cells.	The number of colors must be positive and the number
of planes nonnegative, or a BadValue error results.  If
ncolors and nplanes are requested, then ncolors pixels and



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nplane plane masks are returned.  No mask will have any bits
set to 1 in common with any other mask or with any of the
pixels.  By ORing together each pixel with zero or more
masks, ncolors * 2nplanes distinct pixels can be produced.
All of these are allocated writable by the request.  For
GrayScale or PseudoColor, each mask has exactly one bit set
to 1.  For DirectColor, each has exactly three bits set to
1.  If contig is True and if all masks are ORed together, a
single contiguous set of bits set to 1 will be formed for
GrayScale or PseudoColor and three contiguous sets of bits
set to 1 (one within each pixel subfield) for DirectColor.
The RGB values of the allocated entries are undefined.	XAl-
locColorCells returns nonzero if it succeeded or zero if it
failed.

XAllocColorCells can generate BadColor and BadValue errors.


To allocate read/write color resources for a DirectColor
model, use XAllocColorPlanes.





































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__
|
Status XAllocColorPlanes(display, colormap, contig, pixels_return, ncolors, nreds, ngreens,
			   nblues, rmask_return, gmask_return, bmask_return)
      Display *display;
      Colormap colormap;
      Bool contig;
      unsigned long pixels_return[];
      int ncolors;
      int nreds, ngreens, nblues;
      unsigned long *rmask_return, *gmask_return, *bmask_return;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

contig	  Specifies a Boolean value that indicates whether
	  the planes must be contiguous.

pixels_return
	  Returns an array of pixel values.  XAllocColor-
	  Planes returns the pixel values in this array.

ncolors   Specifies the number of pixel values that are to
	  be returned in the pixels_return array.

nreds
ngreens
nblues
	  Specify the number of red, green, and blue planes.
	  The value you pass must be nonnegative.

rmask_return
gmask_return
bmask_return
	  Return bit masks for the red, green, and blue
	  planes.
|__

The specified ncolors must be positive; and nreds, ngreens,
and nblues must be nonnegative, or a BadValue error results.
If ncolors colors, nreds reds, ngreens greens, and nblues
blues are requested, ncolors pixels are returned; and the
masks have nreds, ngreens, and nblues bits set to 1, respec-
tively.  If contig is True, each mask will have a contiguous
set of bits set to 1.  No mask will have any bits set to 1
in common with any other mask or with any of the pixels.
For DirectColor, each mask will lie within the corresponding
pixel subfield.  By ORing together subsets of masks with
each pixel value, ncolors * 2(nreds+ngreens+nblues) distinct
pixel values can be produced.  All of these are allocated by
the request.  However, in the colormap, there are only ncol-
ors * 2nreds independent red entries, ncolors * 2ngreens
independent green entries, and ncolors * 2nblues independent



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blue entries.  This is true even for PseudoColor.  When the
colormap entry of a pixel value is changed (using XStoreCol-
ors, XStoreColor, or XStoreNamedColor), the pixel is decom-
posed according to the masks, and the corresponding indepen-
dent entries are updated.  XAllocColorPlanes returns nonzero
if it succeeded or zero if it failed.

XAllocColorPlanes can generate BadColor and BadValue errors.


To free colormap cells, use XFreeColors.
__
|
XFreeColors(display, colormap, pixels, npixels, planes)
      Display *display;
      Colormap colormap;
      unsigned long pixels[];
      int npixels;
      unsigned long planes;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

pixels	  Specifies an array of pixel values that map to the
	  cells in the specified colormap.

npixels   Specifies the number of pixels.

planes	  Specifies the planes you want to free.
|__

The XFreeColors function frees the cells represented by pix-
els whose values are in the pixels array.  The planes argu-
ment should not have any bits set to 1 in common with any of
the pixels.  The set of all pixels is produced by ORing
together subsets of the planes argument with the pixels.
The request frees all of these pixels that were allocated by
the client (using XAllocColor, XAllocNamedColor, XAllocCol-
orCells, and XAllocColorPlanes).  Note that freeing an indi-
vidual pixel obtained from XAllocColorPlanes may not actu-
ally allow it to be reused until all of its related pixels
are also freed.  Similarly, a read-only entry is not actu-
ally freed until it has been freed by all clients, and if a
client allocates the same read-only entry multiple times, it
must free the entry that many times before the entry is
actually freed.

All specified pixels that are allocated by the client in the
colormap are freed, even if one or more pixels produce an
error.	If a specified pixel is not a valid index into the
colormap, a BadValue error results.  If a specified pixel is
not allocated by the client (that is, is unallocated or is



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only allocated by another client) or if the colormap was
created with all entries writable (by passing AllocAll to
XCreateColormap), a BadAccess error results.  If more than
one pixel is in error, the one that gets reported is arbi-
trary.

XFreeColors can generate BadAccess, BadColor, and BadValue
errors.

6.7.  Modifying and Querying Colormap Cells


To store an RGB value in a single colormap cell, use XStore-
Color.
__
|
XStoreColor(display, colormap, color)
      Display *display;
      Colormap colormap;
      XColor *color;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

color	  Specifies the pixel and RGB values.
|__

The XStoreColor function changes the colormap entry of the
pixel value specified in the pixel member of the XColor
structure.  You specified this value in the pixel member of
the XColor structure.  This pixel value must be a read/write
cell and a valid index into the colormap.  If a specified
pixel is not a valid index into the colormap, a BadValue
error results.	XStoreColor also changes the red, green,
and/or blue color components.  You specify which color com-
ponents are to be changed by setting DoRed, DoGreen, and/or
DoBlue in the flags member of the XColor structure.  If the
colormap is an installed map for its screen, the changes are
visible immediately.

XStoreColor can generate BadAccess, BadColor, and BadValue
errors.


To store multiple RGB values in multiple colormap cells, use
XStoreColors.









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__
|
XStoreColors(display, colormap, color, ncolors)
      Display *display;
      Colormap colormap;
      XColor color[];
      int ncolors;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

color	  Specifies an array of color definition structures
	  to be stored.

ncolors   Specifies the number of XColor structures in the
	  color definition array.
|__

The XStoreColors function changes the colormap entries of
the pixel values specified in the pixel members of the
XColor structures.  You specify which color components are
to be changed by setting DoRed, DoGreen, and/or DoBlue in
the flags member of the XColor structures.  If the colormap
is an installed map for its screen, the changes are visible
immediately.  XStoreColors changes the specified pixels if
they are allocated writable in the colormap by any client,
even if one or more pixels generates an error.	If a speci-
fied pixel is not a valid index into the colormap, a Bad-
Value error results.  If a specified pixel either is unallo-
cated or is allocated read-only, a BadAccess error results.
If more than one pixel is in error, the one that gets
reported is arbitrary.

XStoreColors can generate BadAccess, BadColor, and BadValue
errors.


To store a color of arbitrary format in a single colormap
cell, use XcmsStoreColor.

















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__
|
Status XcmsStoreColor(display, colormap, color)
      Display *display;
      Colormap colormap;
      XcmsColor *color;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

color	  Specifies the color cell and the color to store.
	  Values specified in this XcmsColor structure
	  remain unchanged on return.
|__

The XcmsStoreColor function converts the color specified in
the XcmsColor structure into RGB values.  It then uses this
RGB specification in an XColor structure, whose three flags
(DoRed, DoGreen, and DoBlue) are set, in a call to XStore-
Color to change the color cell specified by the pixel member
of the XcmsColor structure.  This pixel value must be a
valid index for the specified colormap, and the color cell
specified by the pixel value must be a read/write cell.  If
the pixel value is not a valid index, a BadValue error
results.  If the color cell is unallocated or is allocated
read-only, a BadAccess error results.  If the colormap is an
installed map for its screen, the changes are visible imme-
diately.

Note that XStoreColor has no return value; therefore, an
XcmsSuccess return value from this function indicates that
the conversion to RGB succeeded and the call to XStoreColor
was made.  To obtain the actual color stored, use XcmsQuery-
Color.	Because of the screen's hardware limitations or
gamut compression, the color stored in the colormap may not
be identical to the color specified.

XcmsStoreColor can generate BadAccess, BadColor, and Bad-
Value errors.


To store multiple colors of arbitrary format in multiple
colormap cells, use XcmsStoreColors.













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__
|
Status XcmsStoreColors(display, colormap, colors, ncolors, compression_flags_return)
      Display *display;
      Colormap colormap;
      XcmsColor colors[];
      int ncolors;
      Bool compression_flags_return[];


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

colors	  Specifies the color specification array of Xcms-
	  Color structures, each specifying a color cell and
	  the color to store in that cell.  Values specified
	  in the array remain unchanged upon return.

ncolors   Specifies the number of XcmsColor structures in
	  the color-specification array.

compression_flags_return
	  Returns an array of Boolean values indicating com-
	  pression status.  If a non-NULL pointer is sup-
	  plied, each element of the array is set to True if
	  the corresponding color was compressed and False
	  otherwise.  Pass NULL if the compression status is
	  not useful.
|__

The XcmsStoreColors function converts the colors specified
in the array of XcmsColor structures into RGB values and
then uses these RGB specifications in XColor structures,
whose three flags (DoRed, DoGreen, and DoBlue) are set, in a
call to XStoreColors to change the color cells specified by
the pixel member of the corresponding XcmsColor structure.
Each pixel value must be a valid index for the specified
colormap, and the color cell specified by each pixel value
must be a read/write cell.  If a pixel value is not a valid
index, a BadValue error results.  If a color cell is unallo-
cated or is allocated read-only, a BadAccess error results.
If more than one pixel is in error, the one that gets
reported is arbitrary.	If the colormap is an installed map
for its screen, the changes are visible immediately.

Note that XStoreColors has no return value; therefore, an
XcmsSuccess return value from this function indicates that
conversions to RGB succeeded and the call to XStoreColors
was made.  To obtain the actual colors stored, use Xcms-
QueryColors.  Because of the screen's hardware limitations
or gamut compression, the colors stored in the colormap may
not be identical to the colors specified.





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XcmsStoreColors can generate BadAccess, BadColor, and Bad-
Value errors.


To store a color specified by name in a single colormap
cell, use XStoreNamedColor.
__
|
XStoreNamedColor(display, colormap, color, pixel, flags)
      Display *display;
      Colormap colormap;
      char *color;
      unsigned long pixel;
      int flags;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

color	  Specifies the color name string (for example,
	  red).

pixel	  Specifies the entry in the colormap.

flags	  Specifies which red, green, and blue components
	  are set.
|__

The XStoreNamedColor function looks up the named color with
respect to the screen associated with the colormap and
stores the result in the specified colormap.  The pixel
argument determines the entry in the colormap.	The flags
argument determines which of the red, green, and blue compo-
nents are set.	You can set this member to the bitwise
inclusive OR of the bits DoRed, DoGreen, and DoBlue.  If the
color name is not in the Host Portable Character Encoding,
the result is implementation-dependent.  Use of uppercase or
lowercase does not matter.  If the specified pixel is not a
valid index into the colormap, a BadValue error results.  If
the specified pixel either is unallocated or is allocated
read-only, a BadAccess error results.

XStoreNamedColor can generate BadAccess, BadColor, BadName,
and BadValue errors.

The XQueryColor and XQueryColors functions take pixel values
in the pixel member of XColor structures and store in the
structures the RGB values for those pixels from the speci-
fied colormap.	The values returned for an unallocated entry
are undefined.	These functions also set the flags member in
the XColor structure to all three colors.  If a pixel is not
a valid index into the specified colormap, a BadValue error
results.  If more than one pixel is in error, the one that



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gets reported is arbitrary.


To query the RGB value of a single colormap cell, use
XQueryColor.
__
|
XQueryColor(display, colormap, def_in_out)
      Display *display;
      Colormap colormap;
      XColor *def_in_out;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

def_in_out
	  Specifies and returns the RGB values for the pixel
	  specified in the structure.
|__

The XQueryColor function returns the current RGB value for
the pixel in the XColor structure and sets the DoRed,
DoGreen, and DoBlue flags.

XQueryColor can generate BadColor and BadValue errors.


To query the RGB values of multiple colormap cells, use
XQueryColors.
__
|
XQueryColors(display, colormap, defs_in_out, ncolors)
      Display *display;
      Colormap colormap;
      XColor defs_in_out[];
      int ncolors;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

defs_in_out
	  Specifies and returns an array of color definition
	  structures for the pixel specified in the struc-
	  ture.

ncolors   Specifies the number of XColor structures in the
	  color definition array.
|__

The XQueryColors function returns the RGB value for each



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pixel in each XColor structure and sets the DoRed, DoGreen,
and DoBlue flags in each structure.


XQueryColors can generate BadColor and BadValue errors.


To query the color of a single colormap cell in an arbitrary
format, use XcmsQueryColor.
__
|
Status XcmsQueryColor(display, colormap, color_in_out, result_format)
      Display *display;
      Colormap colormap;
      XcmsColor *color_in_out;
      XcmsColorFormat result_format;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

color_in_out
	  Specifies the pixel member that indicates the
	  color cell to query.	The color specification
	  stored for the color cell is returned in this Xcm-
	  sColor structure.

result_format
	  Specifies the color format for the returned color
	  specification.
|__

The XcmsQueryColor function obtains the RGB value for the
pixel value in the pixel member of the specified XcmsColor
structure and then converts the value to the target format
as specified by the result_format argument.  If the pixel is
not a valid index in the specified colormap, a BadValue
error results.

XcmsQueryColor can generate BadColor and BadValue errors.


To query the color of multiple colormap cells in an arbi-
trary format, use XcmsQueryColors.












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__
|
Status XcmsQueryColors(display, colormap, colors_in_out, ncolors, result_format)
      Display *display;
      Colormap colormap;
      XcmsColor colors_in_out[];
      unsigned int ncolors;
      XcmsColorFormat result_format;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

colors_in_out
	  Specifies an array of XcmsColor structures, each
	  pixel member indicating the color cell to query.
	  The color specifications for the color cells are
	  returned in these structures.

ncolors   Specifies the number of XcmsColor structures in
	  the color-specification array.

result_format
	  Specifies the color format for the returned color
	  specification.
|__

The XcmsQueryColors function obtains the RGB values for
pixel values in the pixel members of XcmsColor structures
and then converts the values to the target format as speci-
fied by the result_format argument.  If a pixel is not a
valid index into the specified colormap, a BadValue error
results.  If more than one pixel is in error, the one that
gets reported is arbitrary.

XcmsQueryColors can generate BadColor and BadValue errors.

6.8.  Color Conversion Context Functions

This section describes functions to create, modify, and
query Color Conversion Contexts (CCCs).

Associated with each colormap is an initial CCC transpar-
ently generated by Xlib.  Therefore, when you specify a col-
ormap as an argument to a function, you are indirectly spec-
ifying a CCC.  The CCC attributes that can be modified by
the X client are:

o    Client White Point

o    Gamut compression procedure and client data

o    White point adjustment procedure and client data




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The initial values for these attributes are implementation
specific.  The CCC attributes for subsequently created CCCs
can be defined by changing the CCC attributes of the default
CCC.  There is a default CCC associated with each screen.

6.8.1.	Getting and Setting the Color Conversion Context of
a Colormap


To obtain the CCC associated with a colormap, use XcmsCCCOf-
Colormap.
__
|
XcmsCCC XcmsCCCOfColormap(display, colormap)
      Display *display;
      Colormap colormap;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.
|__

The XcmsCCCOfColormap function returns the CCC associated
with the specified colormap.  Once obtained, the CCC
attributes can be queried or modified.	Unless the CCC asso-
ciated with the specified colormap is changed with XcmsSetC-
CCOfColormap, this CCC is used when the specified colormap
is used as an argument to color functions.


To change the CCC associated with a colormap, use XcmsSetCC-
COfColormap.
__
|
XcmsCCC XcmsSetCCCOfColormap(display, colormap, ccc)
      Display *display;
      Colormap colormap;
      XcmsCCC ccc;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.

ccc	  Specifies the CCC.
|__

The XcmsSetCCCOfColormap function changes the CCC associated
with the specified colormap.  It returns the CCC previously
associated with the colormap.  If they are not used again in
the application, CCCs should be freed by calling Xcms-
FreeCCC.  Several colormaps may share the same CCC without
restriction; this includes the CCCs generated by Xlib with



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each colormap.	Xlib, however, creates a new CCC with each
new colormap.

6.8.2.	Obtaining the Default Color Conversion Context

You can change the default CCC attributes for subsequently
created CCCs by changing the CCC attributes of the default
CCC.  A default CCC is associated with each screen.


To obtain the default CCC for a screen, use XcmsDefaultCCC.
__
|
XcmsCCC XcmsDefaultCCC(display, screen_number)
      Display *display;
      int screen_number;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

The XcmsDefaultCCC function returns the default CCC for the
specified screen.  Its visual is the default visual of the
screen.  Its initial gamut compression and white point
adjustment procedures as well as the associated client data
are implementation specific.

6.8.3.	Color Conversion Context Macros

Applications should not directly modify any part of the Xcm-
sCCC.  The following lists the C language macros, their cor-
responding function equivalents for other language bindings,
and what data they both can return.


__
|
DisplayOfCCC(ccc)
     XcmsCCC ccc;

Display *XcmsDisplayOfCCC(ccc)
     XcmsCCC ccc;


ccc	  Specifies the CCC.
|__

Both return the display associated with the specified CCC.





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__
|
VisualOfCCC(ccc)
     XcmsCCC ccc;

Visual *XcmsVisualOfCCC(ccc)
     XcmsCCC ccc;


ccc	  Specifies the CCC.
|__

Both return the visual associated with the specified CCC.


__
|
ScreenNumberOfCCC(ccc)
     XcmsCCC ccc;

int XcmsScreenNumberOfCCC(ccc)
     XcmsCCC ccc;


ccc	  Specifies the CCC.
|__

Both return the number of the screen associated with the
specified CCC.


__
|
ScreenWhitePointOfCCC(ccc)
     XcmsCCC ccc;

XcmsColor *XcmsScreenWhitePointOfCCC(ccc)
     XcmsCCC ccc;


ccc	  Specifies the CCC.
|__

Both return the white point of the screen associated with
the specified CCC.













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__
|
ClientWhitePointOfCCC(ccc)
     XcmsCCC ccc;

XcmsColor *XcmsClientWhitePointOfCCC(ccc)
     XcmsCCC ccc;


ccc	  Specifies the CCC.
|__

Both return the Client White Point of the specified CCC.

6.8.4.	Modifying Attributes of a Color Conversion Context

To set the Client White Point in the CCC, use XcmsSetWhite-
Point.
__
|
Status XcmsSetWhitePoint(ccc, color)
      XcmsCCC ccc;
      XcmsColor *color;


ccc	  Specifies the CCC.

color	  Specifies the new Client White Point.
|__

The XcmsSetWhitePoint function changes the Client White
Point in the specified CCC.  Note that the pixel member is
ignored and that the color specification is left unchanged
upon return.  The format for the new white point must be
XcmsCIEXYZFormat, XcmsCIEuvYFormat, XcmsCIExyYFormat, or
XcmsUndefinedFormat.  If the color argument is NULL, this
function sets the format component of the Client White Point
specification to XcmsUndefinedFormat, indicating that the
Client White Point is assumed to be the same as the Screen
White Point.

This function returns nonzero status if the format for the
new white point is valid; otherwise, it returns zero.



To set the gamut compression procedure and corresponding
client data in a specified CCC, use XcmsSetCompressionProc.










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__
|
XcmsCompressionProc XcmsSetCompressionProc(ccc, compression_proc, client_data)
      XcmsCCC ccc;
      XcmsCompressionProc compression_proc;
      XPointer client_data;


ccc	  Specifies the CCC.

compression_proc
	  Specifies the gamut compression procedure that is
	  to be applied when a color lies outside the
	  screen's color gamut.  If NULL is specified and a
	  function using this CCC must convert a color spec-
	  ification to a device-dependent format and encoun-
	  ters a color that lies outside the screen's color
	  gamut, that function will return XcmsFailure.

client_data
	  Specifies client data for the gamut compression
	  procedure or NULL.
|__

The XcmsSetCompressionProc function first sets the gamut
compression procedure and client data in the specified CCC
with the newly specified procedure and client data and then
returns the old procedure.


To set the white point adjustment procedure and correspond-
ing client data in a specified CCC, use XcmsSetWhiteAdjust-
Proc.

__
|    XcmsWhiteAdjustProc XcmsSetWhiteAdjustProc(ccc, white_adjust_proc, client_data)
      XcmsCCC ccc;
      XcmsWhiteAdjustProc white_adjust_proc;
      XPointer client_data;


ccc	  Specifies the CCC.

white_adjust_proc
	  Specifies the white point adjustment procedure.

client_data
	  Specifies client data for the white point adjust-
	  ment procedure or NULL.
|__

The XcmsSetWhiteAdjustProc function first sets the white
point adjustment procedure and client data in the specified
CCC with the newly specified procedure and client data and
then returns the old procedure.



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6.8.5.	Creating and Freeing a Color Conversion Context

You can explicitly create a CCC within your application by
calling XcmsCreateCCC.	These created CCCs can then be used
by those functions that explicitly call for a CCC argument.
Old CCCs that will not be used by the application should be
freed using XcmsFreeCCC.


To create a CCC, use XcmsCreateCCC.















































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__
|
XcmsCCC XcmsCreateCCC(display, screen_number, visual, client_white_point, compression_proc,
		    compression_client_data, white_adjust_proc, white_adjust_client_data)
      Display *display;
      int screen_number;
      Visual *visual;
      XcmsColor *client_white_point;
      XcmsCompressionProc compression_proc;
      XPointer compression_client_data;
      XcmsWhiteAdjustProc white_adjust_proc;
      XPointer white_adjust_client_data;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.

visual	  Specifies the visual type.

client_white_point
	  Specifies the Client White Point.  If NULL is
	  specified, the Client White Point is to be assumed
	  to be the same as the Screen White Point.  Note
	  that the pixel member is ignored.

compression_proc
	  Specifies the gamut compression procedure that is
	  to be applied when a color lies outside the
	  screen's color gamut.  If NULL is specified and a
	  function using this CCC must convert a color spec-
	  ification to a device-dependent format and encoun-
	  ters a color that lies outside the screen's color
	  gamut, that function will return XcmsFailure.

compression_client_data
	  Specifies client data for use by the gamut com-
	  pression procedure or NULL.

white_adjust_proc
	  Specifies the white adjustment procedure that is
	  to be applied when the Client White Point differs
	  from the Screen White Point.	NULL indicates that
	  no white point adjustment is desired.

white_adjust_client_data
	  Specifies client data for use with the white point
	  adjustment procedure or NULL.
|__

The XcmsCreateCCC function creates a CCC for the specified
display, screen, and visual.




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To free a CCC, use XcmsFreeCCC.
__
|
void XcmsFreeCCC(ccc)
      XcmsCCC ccc;


ccc	  Specifies the CCC.
|__

The XcmsFreeCCC function frees the memory used for the spec-
ified CCC.  Note that default CCCs and those currently asso-
ciated with colormaps are ignored.

6.9.  Converting between Color Spaces


To convert an array of color specifications in arbitrary
color formats to a single destination format, use XcmsCon-
vertColors.





































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__
|
Status XcmsConvertColors(ccc, colors_in_out, ncolors, target_format, compression_flags_return)
      XcmsCCC ccc;
      XcmsColor colors_in_out[];
      unsigned int ncolors;
      XcmsColorFormat target_format;
      Bool compression_flags_return[];


ccc	  Specifies the CCC.  If conversion is between
	  device-independent color spaces only (for example,
	  TekHVC to CIELuv), the CCC is necessary only to
	  specify the Client White Point.

colors_in_out
	  Specifies an array of color specifications.  Pixel
	  members are ignored and remain unchanged upon
	  return.

ncolors   Specifies the number of XcmsColor structures in
	  the color-specification array.

target_format
	  Specifies the target color specification format.

compression_flags_return
	  Returns an array of Boolean values indicating com-
	  pression status.  If a non-NULL pointer is sup-
	  plied, each element of the array is set to True if
	  the corresponding color was compressed and False
	  otherwise.  Pass NULL if the compression status is
	  not useful.
|__

The XcmsConvertColors function converts the color specifica-
tions in the specified array of XcmsColor structures from
their current format to a single target format, using the
specified CCC.	When the return value is XcmsFailure, the
contents of the color specification array are left
unchanged.

The array may contain a mixture of color specification for-
mats (for example, 3 CIE XYZ, 2 CIE Luv, and so on).  When
the array contains both device-independent and device-depen-
dent color specifications and the target_format argument
specifies a device-dependent format (for example, XcmsRGBi-
Format, XcmsRGBFormat), all specifications are converted to
CIE XYZ format and then to the target device-dependent for-
mat.

6.10.  Callback Functions

This section describes the gamut compression and white point
adjustment callbacks.



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The gamut compression procedure specified in the CCC is
called when an attempt to convert a color specification from
XcmsCIEXYZ to a device-dependent format (typically XcmsRGBi)
results in a color that lies outside the screen's color
gamut.	If the gamut compression procedure requires client
data, this data is passed via the gamut compression client
data in the CCC.

During color specification conversion between device-inde-
pendent and device-dependent color spaces, if a white point
adjustment procedure is specified in the CCC, it is trig-
gered when the Client White Point and Screen White Point
differ.  If required, the client data is obtained from the
CCC.

6.10.1.  Prototype Gamut Compression Procedure

The gamut compression callback interface must adhere to the
following:






































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__
|
typedef Status (*XcmsCompressionProc)(ccc, colors_in_out, ncolors, index, compression_flags_return)
      XcmsCCC ccc;
      XcmsColor colors_in_out[];
      unsigned int ncolors;
      unsigned int index;
      Bool compression_flags_return[];


ccc	  Specifies the CCC.

colors_in_out
	  Specifies an array of color specifications.  Pixel
	  members should be ignored and must remain
	  unchanged upon return.

ncolors   Specifies the number of XcmsColor structures in
	  the color-specification array.

index	  Specifies the index into the array of XcmsColor
	  structures for the encountered color specification
	  that lies outside the screen's color gamut.  Valid
	  values are 0 (for the first element) to ncolors -
	  1.

compression_flags_return
	  Returns an array of Boolean values for indicating
	  compression status.  If a non-NULL pointer is sup-
	  plied and a color at a given index is compressed,
	  then True should be stored at the corresponding
	  index in this array; otherwise, the array should
	  not be modified.
|__

When implementing a gamut compression procedure, consider
the following rules and assumptions:

o    The gamut compression procedure can attempt to compress
     one or multiple specifications at a time.

o    When called, elements 0 to index - 1 in the color spec-
     ification array can be assumed to fall within the
     screen's color gamut.  In addition, these color speci-
     fications are already in some device-dependent format
     (typically XcmsRGBi).  If any modifications are made to
     these color specifications, they must be in their ini-
     tial device-dependent format upon return.

o    When called, the element in the color specification
     array specified by the index argument contains the
     color specification outside the screen's color gamut
     encountered by the calling routine.  In addition, this
     color specification can be assumed to be in XcmsCIEXYZ.
     Upon return, this color specification must be in



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     XcmsCIEXYZ.

o    When called, elements from index to ncolors - 1 in the
     color specification array may or may not fall within
     the screen's color gamut.	In addition, these color
     specifications can be assumed to be in XcmsCIEXYZ.  If
     any modifications are made to these color specifica-
     tions, they must be in XcmsCIEXYZ upon return.

o    The color specifications passed to the gamut compres-
     sion procedure have already been adjusted to the Screen
     White Point.  This means that at this point the color
     specification's white point is the Screen White Point.

o    If the gamut compression procedure uses a device-inde-
     pendent color space not initially accessible for use in
     the color management system, use XcmsAddColorSpace to
     ensure that it is added.

6.10.2.  Supplied Gamut Compression Procedures

The following equations are useful in describing gamut com-
pression functions:


CIELabPsychometricChroma=sqrt(a_star2+b_star2)

CIELabPsychometricHue=tan-1[______]

CIELuvPsychometricChroma=sqrt(u_star2+v_star2)

CIELuvPsychometricHue=tan-1[______]


The gamut compression callback procedures provided by Xlib
are as follows:

o    XcmsCIELabClipL

     This brings the encountered out-of-gamut color specifi-
     cation into the screen's color gamut by reducing or
     increasing CIE metric lightness (L*) in the CIE L*a*b*
     color space until the color is within the gamut.  If
     the Psychometric Chroma of the color specification is
     beyond maximum for the Psychometric Hue Angle, then
     while maintaining the same Psychometric Hue Angle, the
     color will be clipped to the CIE L*a*b* coordinates of
     maximum Psychometric Chroma.  See XcmsCIELabQueryMaxC.
     No client data is necessary.

o    XcmsCIELabClipab

     This brings the encountered out-of-gamut color specifi-
     cation into the screen's color gamut by reducing



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     Psychometric Chroma, while maintaining Psychometric Hue
     Angle, until the color is within the gamut.  No client
     data is necessary.

o    XcmsCIELabClipLab

     This brings the encountered out-of-gamut color specifi-
     cation into the screen's color gamut by replacing it
     with CIE L*a*b* coordinates that fall within the color
     gamut while maintaining the original Psychometric Hue
     Angle and whose vector to the original coordinates is
     the shortest attainable.  No client data is necessary.

o    XcmsCIELuvClipL

     This brings the encountered out-of-gamut color specifi-
     cation into the screen's color gamut by reducing or
     increasing CIE metric lightness (L*) in the CIE L*u*v*
     color space until the color is within the gamut.  If
     the Psychometric Chroma of the color specification is
     beyond maximum for the Psychometric Hue Angle, then,
     while maintaining the same Psychometric Hue Angle, the
     color will be clipped to the CIE L*u*v* coordinates of
     maximum Psychometric Chroma.  See XcmsCIELuvQueryMaxC.
     No client data is necessary.

o    XcmsCIELuvClipuv

     This brings the encountered out-of-gamut color specifi-
     cation into the screen's color gamut by reducing Psy-
     chometric Chroma, while maintaining Psychometric Hue
     Angle, until the color is within the gamut.  No client
     data is necessary.

o    XcmsCIELuvClipLuv

     This brings the encountered out-of-gamut color specifi-
     cation into the screen's color gamut by replacing it
     with CIE L*u*v* coordinates that fall within the color
     gamut while maintaining the original Psychometric Hue
     Angle and whose vector to the original coordinates is
     the shortest attainable.  No client data is necessary.

o    XcmsTekHVCClipV

     This brings the encountered out-of-gamut color specifi-
     cation into the screen's color gamut by reducing or
     increasing the Value dimension in the TekHVC color
     space until the color is within the gamut.  If Chroma
     of the color specification is beyond maximum for the
     particular Hue, then, while maintaining the same Hue,
     the color will be clipped to the Value and Chroma coor-
     dinates that represent maximum Chroma for that particu-
     lar Hue.  No client data is necessary.



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o    XcmsTekHVCClipC

     This brings the encountered out-of-gamut color specifi-
     cation into the screen's color gamut by reducing the
     Chroma dimension in the TekHVC color space until the
     color is within the gamut.  No client data is neces-
     sary.

o    XcmsTekHVCClipVC

     This brings the encountered out-of-gamut color specifi-
     cation into the screen's color gamut by replacing it
     with TekHVC coordinates that fall within the color
     gamut while maintaining the original Hue and whose vec-
     tor to the original coordinates is the shortest attain-
     able.  No client data is necessary.

6.10.3.  Prototype White Point Adjustment Procedure

The white point adjustment procedure interface must adhere
to the following:




































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__
|
typedef Status (*XcmsWhiteAdjustProc)(ccc, initial_white_point, target_white_point, target_format,
		colors_in_out, ncolors, compression_flags_return)
       XcmsCCC ccc;
       XcmsColor *initial_white_point;
       XcmsColor *target_white_point;
       XcmsColorFormat target_format;
       XcmsColor colors_in_out[];
       unsigned int ncolors;
       Bool compression_flags_return[];


ccc	  Specifies the CCC.

initial_white_point
	  Specifies the initial white point.

target_white_point
	  Specifies the target white point.

target_format
	  Specifies the target color specification format.

colors_in_out
	  Specifies an array of color specifications.  Pixel
	  members should be ignored and must remain
	  unchanged upon return.

ncolors   Specifies the number of XcmsColor structures in
	  the color-specification array.

compression_flags_return
	  Returns an array of Boolean values for indicating
	  compression status.  If a non-NULL pointer is sup-
	  plied and a color at a given index is compressed,
	  then True should be stored at the corresponding
	  index in this array; otherwise, the array should
	  not be modified.
|__


6.10.4.  Supplied White Point Adjustment Procedures

White point adjustment procedures provided by Xlib are as
follows:

o    XcmsCIELabWhiteShiftColors

     This uses the CIE L*a*b* color space for adjusting the
     chromatic character of colors to compensate for the
     chromatic differences between the source and destina-
     tion white points.  This procedure simply converts the
     color specifications to XcmsCIELab using the source
     white point and then converts to the target



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     specification format using the destination's white
     point.  No client data is necessary.

o    XcmsCIELuvWhiteShiftColors

     This uses the CIE L*u*v* color space for adjusting the
     chromatic character of colors to compensate for the
     chromatic differences between the source and destina-
     tion white points.  This procedure simply converts the
     color specifications to XcmsCIELuv using the source
     white point and then converts to the target specifica-
     tion format using the destination's white point.  No
     client data is necessary.

o    XcmsTekHVCWhiteShiftColors

     This uses the TekHVC color space for adjusting the
     chromatic character of colors to compensate for the
     chromatic differences between the source and destina-
     tion white points.  This procedure simply converts the
     color specifications to XcmsTekHVC using the source
     white point and then converts to the target specifica-
     tion format using the destination's white point.  An
     advantage of this procedure over those previously
     described is an attempt to minimize hue shift.  No
     client data is necessary.

From an implementation point of view, these white point
adjustment procedures convert the color specifications to a
device-independent but white-point-dependent color space
(for example, CIE L*u*v*, CIE L*a*b*, TekHVC) using one
white point and then converting those specifications to the
target color space using another white point.  In other
words, the specification goes in the color space with one
white point but comes out with another white point, result-
ing in a chromatic shift based on the chromatic displacement
between the initial white point and target white point.  The
CIE color spaces that are assumed to be white-point-indepen-
dent are CIE u'v'Y, CIE XYZ, and CIE xyY.  When developing a
custom white point adjustment procedure that uses a device-
independent color space not initially accessible for use in
the color management system, use XcmsAddColorSpace to ensure
that it is added.

As an example, if the CCC specifies a white point adjustment
procedure and if the Client White Point and Screen White
Point differ, the XcmsAllocColor function will use the white
point adjustment procedure twice:

o    Once to convert to XcmsRGB

o    A second time to convert from XcmsRGB





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For example, assume the specification is in XcmsCIEuvY and
the adjustment procedure is XcmsCIELuvWhiteShiftColors.
During conversion to XcmsRGB, the call to XcmsAllocColor
results in the following series of color specification con-
versions:

o    From XcmsCIEuvY to XcmsCIELuv using the Client White
     Point

o    From XcmsCIELuv to XcmsCIEuvY using the Screen White
     Point

o    From XcmsCIEuvY to XcmsCIEXYZ (CIE u'v'Y and XYZ are
     white-point-independent color spaces)

o    From XcmsCIEXYZ to XcmsRGBi

o    From XcmsRGBi to XcmsRGB

The resulting RGB specification is passed to XAllocColor,
and the RGB specification returned by XAllocColor is con-
verted back to XcmsCIEuvY by reversing the color conversion
sequence.

6.11.  Gamut Querying Functions

This section describes the gamut querying functions that
Xlib provides.	These functions allow the client to query
the boundary of the screen's color gamut in terms of the CIE
L*a*b*, CIE L*u*v*, and TekHVC color spaces.  Functions are
also provided that allow you to query the color specifica-
tion of:

o    White (full-intensity red, green, and blue)

o    Red (full-intensity red while green and blue are zero)

o    Green (full-intensity green while red and blue are
     zero)

o    Blue (full-intensity blue while red and green are zero)

o    Black (zero-intensity red, green, and blue)

The white point associated with color specifications passed
to and returned from these gamut querying functions is
assumed to be the Screen White Point.  This is a reasonable
assumption, because the client is trying to query the
screen's color gamut.

The following naming convention is used for the Max and Min
functions:





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Xcms<color_space>QueryMax<dimensions>

Xcms<color_space>QueryMin<dimensions>


The <dimensions> consists of a letter or letters that iden-
tify the dimensions of the color space that are not fixed.
For example, XcmsTekHVCQueryMaxC is given a fixed Hue and
Value for which maximum Chroma is found.

6.11.1.  Red, Green, and Blue Queries

To obtain the color specification for black (zero-intensity
red, green, and blue), use XcmsQueryBlack.
__
|
Status XcmsQueryBlack(ccc, target_format, color_return)
      XcmsCCC ccc;
      XcmsColorFormat target_format;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

target_format
	  Specifies the target color specification format.

color_return
	  Returns the color specification in the specified
	  target format for zero-intensity red, green, and
	  blue.  The white point associated with the
	  returned color specification is the Screen White
	  Point.  The value returned in the pixel member is
	  undefined.
|__

The XcmsQueryBlack function returns the color specification
in the specified target format for zero-intensity red,
green, and blue.


To obtain the color specification for blue (full-intensity
blue while red and green are zero), use XcmsQueryBlue.













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__
|
Status XcmsQueryBlue(ccc, target_format, color_return)
      XcmsCCC ccc;
      XcmsColorFormat target_format;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

target_format
	  Specifies the target color specification format.

color_return
	  Returns the color specification in the specified
	  target format for full-intensity blue while red
	  and green are zero.  The white point associated
	  with the returned color specification is the
	  Screen White Point.  The value returned in the
	  pixel member is undefined.
|__

The XcmsQueryBlue function returns the color specification
in the specified target format for full-intensity blue while
red and green are zero.


To obtain the color specification for green (full-intensity
green while red and blue are zero), use XcmsQueryGreen.
__
|
Status XcmsQueryGreen(ccc, target_format, color_return)
      XcmsCCC ccc;
      XcmsColorFormat target_format;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

target_format
	  Specifies the target color specification format.

color_return
	  Returns the color specification in the specified
	  target format for full-intensity green while red
	  and blue are zero.  The white point associated
	  with the returned color specification is the
	  Screen White Point.  The value returned in the
	  pixel member is undefined.
|__

The XcmsQueryGreen function returns the color specification
in the specified target format for full-intensity green



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while red and blue are zero.


To obtain the color specification for red (full-intensity
red while green and blue are zero), use XcmsQueryRed.
__
|
Status XcmsQueryRed(ccc, target_format, color_return)
      XcmsCCC ccc;
      XcmsColorFormat target_format;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

target_format
	  Specifies the target color specification format.

color_return
	  Returns the color specification in the specified
	  target format for full-intensity red while green
	  and blue are zero.  The white point associated
	  with the returned color specification is the
	  Screen White Point.  The value returned in the
	  pixel member is undefined.
|__

The XcmsQueryRed function returns the color specification in
the specified target format for full-intensity red while
green and blue are zero.


To obtain the color specification for white (full-intensity
red, green, and blue), use XcmsQueryWhite.






















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__
|
Status XcmsQueryWhite(ccc, target_format, color_return)
      XcmsCCC ccc;
      XcmsColorFormat target_format;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

target_format
	  Specifies the target color specification format.

color_return
	  Returns the color specification in the specified
	  target format for full-intensity red, green, and
	  blue.  The white point associated with the
	  returned color specification is the Screen White
	  Point.  The value returned in the pixel member is
	  undefined.
|__

The XcmsQueryWhite function returns the color specification
in the specified target format for full-intensity red,
green, and blue.

6.11.2.  CIELab Queries

The following equations are useful in describing the CIELab
query functions:


CIELabPsychometricChroma=sqrt(a_star2+b_star2)

CIELabPsychometricHue=tan-1[______]


To obtain the CIE L*a*b* coordinates of maximum Psychometric
Chroma for a given Psychometric Hue Angle and CIE metric
lightness (L*), use XcmsCIELabQueryMaxC.

















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__
|
Status XcmsCIELabQueryMaxC(ccc, hue_angle, L_star, color_return)
      XcmsCCC ccc;
      XcmsFloat hue_angle;
      XcmsFloat L_star;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

hue_angle Specifies the hue angle (in degrees) at which to
	  find maximum chroma.

L_star	  Specifies the lightness (L*) at which to find max-
	  imum chroma.

color_return
	  Returns the CIE L*a*b* coordinates of maximum
	  chroma displayable by the screen for the given hue
	  angle and lightness.	The white point associated
	  with the returned color specification is the
	  Screen White Point.  The value returned in the
	  pixel member is undefined.
|__

The XcmsCIELabQueryMaxC function, given a hue angle and
lightness, finds the point of maximum chroma displayable by
the screen.  It returns this point in CIE L*a*b* coordi-
nates.


To obtain the CIE L*a*b* coordinates of maximum CIE metric
lightness (L*) for a given Psychometric Hue Angle and Psy-
chometric Chroma, use XcmsCIELabQueryMaxL.






















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__
|
Status XcmsCIELabQueryMaxL(ccc, hue_angle, chroma, color_return)
      XcmsCCC ccc;
      XcmsFloat hue_angle;
      XcmsFloat chroma;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

hue_angle Specifies the hue angle (in degrees) at which to
	  find maximum lightness.

chroma	  Specifies the chroma at which to find maximum
	  lightness.

color_return
	  Returns the CIE L*a*b* coordinates of maximum
	  lightness displayable by the screen for the given
	  hue angle and chroma.  The white point associated
	  with the returned color specification is the
	  Screen White Point.  The value returned in the
	  pixel member is undefined.
|__

The XcmsCIELabQueryMaxL function, given a hue angle and
chroma, finds the point in CIE L*a*b* color space of maximum
lightness (L*) displayable by the screen.  It returns this
point in CIE L*a*b* coordinates.  An XcmsFailure return
value usually indicates that the given chroma is beyond max-
imum for the given hue angle.


To obtain the CIE L*a*b* coordinates of maximum Psychometric
Chroma for a given Psychometric Hue Angle, use XcmsCIELab-
QueryMaxLC.




















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__
|
Status XcmsCIELabQueryMaxLC(ccc, hue_angle, color_return)
      XcmsCCC ccc;
      XcmsFloat hue_angle;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

hue_angle Specifies the hue angle (in degrees) at which to
	  find maximum chroma.

color_return
	  Returns the CIE L*a*b* coordinates of maximum
	  chroma displayable by the screen for the given hue
	  angle.  The white point associated with the
	  returned color specification is the Screen White
	  Point.  The value returned in the pixel member is
	  undefined.
|__

The XcmsCIELabQueryMaxLC function, given a hue angle, finds
the point of maximum chroma displayable by the screen.	It
returns this point in CIE L*a*b* coordinates.


To obtain the CIE L*a*b* coordinates of minimum CIE metric
lightness (L*) for a given Psychometric Hue Angle and Psy-
chometric Chroma, use XcmsCIELabQueryMinL.



























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__
|
Status XcmsCIELabQueryMinL(ccc, hue_angle, chroma, color_return)
      XcmsCCC ccc;
      XcmsFloat hue_angle;
      XcmsFloat chroma;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

hue_angle Specifies the hue angle (in degrees) at which to
	  find minimum lightness.

chroma	  Specifies the chroma at which to find minimum
	  lightness.

color_return
	  Returns the CIE L*a*b* coordinates of minimum
	  lightness displayable by the screen for the given
	  hue angle and chroma.  The white point associated
	  with the returned color specification is the
	  Screen White Point.  The value returned in the
	  pixel member is undefined.
|__

The XcmsCIELabQueryMinL function, given a hue angle and
chroma, finds the point of minimum lightness (L*) dis-
playable by the screen.  It returns this point in CIE L*a*b*
coordinates.  An XcmsFailure return value usually indicates
that the given chroma is beyond maximum for the given hue
angle.

6.11.3.  CIELuv Queries

The following equations are useful in describing the CIELuv
query functions:


CIELuvPsychometricChroma=sqrt(u_star2+v_star2)

CIELuvPsychometricHue=tan-1[______]



To obtain the CIE L*u*v* coordinates of maximum Psychometric
Chroma for a given Psychometric Hue Angle and CIE metric
lightness (L*), use XcmsCIELuvQueryMaxC.









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__
|
Status XcmsCIELuvQueryMaxC(ccc, hue_angle, L_star, color_return)
      XcmsCCC ccc;
      XcmsFloat hue_angle;
      XcmsFloat L_star;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

hue_angle Specifies the hue angle (in degrees) at which to
	  find maximum chroma.

L_star	  Specifies the lightness (L*) at which to find max-
	  imum chroma.

color_return
	  Returns the CIE L*u*v* coordinates of maximum
	  chroma displayable by the screen for the given hue
	  angle and lightness.	The white point associated
	  with the returned color specification is the
	  Screen White Point.  The value returned in the
	  pixel member is undefined.
|__

The XcmsCIELuvQueryMaxC function, given a hue angle and
lightness, finds the point of maximum chroma displayable by
the screen.  It returns this point in CIE L*u*v* coordi-
nates.


To obtain the CIE L*u*v* coordinates of maximum CIE metric
lightness (L*) for a given Psychometric Hue Angle and Psy-
chometric Chroma, use XcmsCIELuvQueryMaxL.






















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__
|
Status XcmsCIELuvQueryMaxL(ccc, hue_angle, chroma, color_return)
      XcmsCCC ccc;
      XcmsFloat hue_angle;
      XcmsFloat chroma;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

hue_angle Specifies the hue angle (in degrees) at which to
	  find maximum lightness.

L_star	  Specifies the lightness (L*) at which to find max-
	  imum lightness.

color_return
	  Returns the CIE L*u*v* coordinates of maximum
	  lightness displayable by the screen for the given
	  hue angle and chroma.  The white point associated
	  with the returned color specification is the
	  Screen White Point.  The value returned in the
	  pixel member is undefined.
|__

The XcmsCIELuvQueryMaxL function, given a hue angle and
chroma, finds the point in CIE L*u*v* color space of maximum
lightness (L*) displayable by the screen.  It returns this
point in CIE L*u*v* coordinates.  An XcmsFailure return
value usually indicates that the given chroma is beyond max-
imum for the given hue angle.


To obtain the CIE L*u*v* coordinates of maximum Psychometric
Chroma for a given Psychometric Hue Angle, use XcmsCIELuv-
QueryMaxLC.




















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__
|
Status XcmsCIELuvQueryMaxLC(ccc, hue_angle, color_return)
      XcmsCCC ccc;
      XcmsFloat hue_angle;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

hue_angle Specifies the hue angle (in degrees) at which to
	  find maximum chroma.

color_return
	  Returns the CIE L*u*v* coordinates of maximum
	  chroma displayable by the screen for the given hue
	  angle.  The white point associated with the
	  returned color specification is the Screen White
	  Point.  The value returned in the pixel member is
	  undefined.
|__

The XcmsCIELuvQueryMaxLC function, given a hue angle, finds
the point of maximum chroma displayable by the screen.	It
returns this point in CIE L*u*v* coordinates.


To obtain the CIE L*u*v* coordinates of minimum CIE metric
lightness (L*) for a given Psychometric Hue Angle and Psy-
chometric Chroma, use XcmsCIELuvQueryMinL.



























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__
|
Status XcmsCIELuvQueryMinL(ccc, hue_angle, chroma, color_return)
      XcmsCCC ccc;
      XcmsFloat hue_angle;
      XcmsFloat chroma;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

hue_angle Specifies the hue angle (in degrees) at which to
	  find minimum lightness.

chroma	  Specifies the chroma at which to find minimum
	  lightness.

color_return
	  Returns the CIE L*u*v* coordinates of minimum
	  lightness displayable by the screen for the given
	  hue angle and chroma.  The white point associated
	  with the returned color specification is the
	  Screen White Point.  The value returned in the
	  pixel member is undefined.
|__

The XcmsCIELuvQueryMinL function, given a hue angle and
chroma, finds the point of minimum lightness (L*) dis-
playable by the screen.  It returns this point in CIE L*u*v*
coordinates.  An XcmsFailure return value usually indicates
that the given chroma is beyond maximum for the given hue
angle.

6.11.4.  TekHVC Queries

To obtain the maximum Chroma for a given Hue and Value, use
XcmsTekHVCQueryMaxC.




















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__
|
Status XcmsTekHVCQueryMaxC(ccc, hue, value, color_return)
      XcmsCCC ccc;
      XcmsFloat hue;
      XcmsFloat value;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

hue	  Specifies the Hue in which to find the maximum
	  Chroma.

value	  Specifies the Value in which to find the maximum
	  Chroma.

color_return
	  Returns the maximum Chroma along with the actual
	  Hue and Value  at which the maximum Chroma was
	  found.  The white point associated with the
	  returned color specification is the Screen White
	  Point.  The value returned in the pixel member is
	  undefined.
|__

The XcmsTekHVCQueryMaxC function, given a Hue and Value,
determines the maximum Chroma in TekHVC color space dis-
playable by the screen.  It returns the maximum Chroma along
with the actual Hue and Value at which the maximum Chroma
was found.


To obtain the maximum Value for a given Hue and Chroma, use
XcmsTekHVCQueryMaxV.






















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__
|
Status XcmsTekHVCQueryMaxV(ccc, hue, chroma, color_return)
      XcmsCCC ccc;
      XcmsFloat hue;
      XcmsFloat chroma;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

hue	  Specifies the Hue in which to find the maximum
	  Value.

chroma	  Specifies the chroma at which to find maximum
	  Value.

color_return
	  Returns the maximum Value along with the Hue and
	  Chroma at which the maximum Value was found.	The
	  white point associated with the returned color
	  specification is the Screen White Point.  The
	  value returned in the pixel member is undefined.
|__

The XcmsTekHVCQueryMaxV function, given a Hue and Chroma,
determines the maximum Value in TekHVC color space dis-
playable by the screen.  It returns the maximum Value and
the actual Hue and Chroma at which the maximum Value was
found.


To obtain the maximum Chroma and Value at which it is
reached for a specified Hue, use XcmsTekHVCQueryMaxVC.























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__
|
Status XcmsTekHVCQueryMaxVC(ccc, hue, color_return)
      XcmsCCC ccc;
      XcmsFloat hue;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

hue	  Specifies the Hue in which to find the maximum
	  Chroma.

color_return
	  Returns the color specification in XcmsTekHVC for
	  the maximum Chroma, the Value at which that maxi-
	  mum Chroma is reached, and the actual Hue at which
	  the maximum Chroma was found.  The white point
	  associated with the returned color specification
	  is the Screen White Point.  The value returned in
	  the pixel member is undefined.
|__

The XcmsTekHVCQueryMaxVC function, given a Hue, determines
the maximum Chroma in TekHVC color space displayable by the
screen and the Value at which that maximum Chroma is
reached.  It returns the maximum Chroma, the Value at which
that maximum Chroma is reached, and the actual Hue for which
the maximum Chroma was found.


To obtain a specified number of TekHVC specifications such
that they contain maximum Values for a specified Hue and the
Chroma at which the maximum Values are reached, use Xcm-
sTekHVCQueryMaxVSamples.






















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__
|
Status XcmsTekHVCQueryMaxVSamples(ccc, hue, colors_return, nsamples)
      XcmsCCC ccc;
      XcmsFloat hue;
      XcmsColor colors_return[];
      unsigned int nsamples;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

hue	  Specifies the Hue for maximum Chroma/Value sam-
	  ples.

nsamples  Specifies the number of samples.

colors_return
	  Returns nsamples of color specifications in Xcm-
	  sTekHVC such that the Chroma is the maximum
	  attainable for the Value and Hue.  The white point
	  associated with the returned color specification
	  is the Screen White Point.  The value returned in
	  the pixel member is undefined.
|__

The XcmsTekHVCQueryMaxVSamples returns nsamples of maximum
Value, the Chroma at which that maximum Value is reached,
and the actual Hue for which the maximum Chroma was found.
These sample points may then be used to plot the maximum
Value/Chroma boundary of the screen's color gamut for the
specified Hue in TekHVC color space.


To obtain the minimum Value for a given Hue and Chroma, use
XcmsTekHVCQueryMinV.






















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__
|
Status XcmsTekHVCQueryMinV(ccc, hue, chroma, color_return)
      XcmsCCC ccc;
      XcmsFloat hue;
      XcmsFloat chroma;
      XcmsColor *color_return;


ccc	  Specifies the CCC.  The CCC's Client White Point
	  and white point adjustment procedures are ignored.

hue	  Specifies the Hue in which to find the minimum
	  Value.

value	  Specifies the Value in which to find the minimum
	  Value.

color_return
	  Returns the minimum Value and the actual Hue and
	  Chroma at which the minimum Value was found.	The
	  white point associated with the returned color
	  specification is the Screen White Point.  The
	  value returned in the pixel member is undefined.
|__

The XcmsTekHVCQueryMinV function, given a Hue and Chroma,
determines the minimum Value in TekHVC color space dis-
playable by the screen.  It returns the minimum Value and
the actual Hue and Chroma at which the minimum Value was
found.

6.12.  Color Management Extensions

The Xlib color management facilities can be extended in two
ways:

o    Device-Independent Color Spaces

     Device-independent color spaces that are derivable to
     CIE XYZ space can be added using the XcmsAddColorSpace
     function.

o    Color Characterization Function Set

     A Color Characterization Function Set consists of
     device-dependent color spaces and their functions that
     convert between these color spaces and the CIE XYZ
     color space, bundled together for a specific class of
     output devices.  A function set can be added using the
     XcmsAddFunctionSet function.







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6.12.1.  Color Spaces

The CIE XYZ color space serves as the hub for all conver-
sions between device-independent and device-dependent color
spaces.  Therefore, the knowledge to convert an XcmsColor
structure to and from CIE XYZ format is associated with each
color space.  For example, conversion from CIE L*u*v* to RGB
requires the knowledge to convert from CIE L*u*v* to CIE XYZ
and from CIE XYZ to RGB.  This knowledge is stored as an
array of functions that, when applied in series, will con-
vert the XcmsColor structure to or from CIE XYZ format.
This color specification conversion mechanism facilitates
the addition of color spaces.

Of course, when converting between only device-independent
color spaces or only device-dependent color spaces, short-
cuts are taken whenever possible.  For example, conversion
from TekHVC to CIE L*u*v* is performed by intermediate con-
version to CIE u*v*Y and then to CIE L*u*v*, thus bypassing
conversion between CIE u*v*Y and CIE XYZ.

6.12.2.  Adding Device-Independent Color Spaces

To add a device-independent color space, use XcmsAddCol-
orSpace.
__
|
Status XcmsAddColorSpace(color_space)
      XcmsColorSpace *color_space;


color_space
	  Specifies the device-independent color space to
	  add.
|__

The XcmsAddColorSpace function makes a device-independent
color space (actually an XcmsColorSpace structure) accessi-
ble by the color management system.  Because format values
for unregistered color spaces are assigned at run time, they
should be treated as private to the client.  If references
to an unregistered color space must be made outside the
client (for example, storing color specifications in a file
using the unregistered color space), then reference should
be made by color space prefix (see XcmsFormatOfPrefix and
XcmsPrefixOfFormat).

If the XcmsColorSpace structure is already accessible in the
color management system, XcmsAddColorSpace returns XcmsSuc-
cess.

Note that added XcmsColorSpaces must be retained for refer-
ence by Xlib.




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6.12.3.  Querying Color Space Format and Prefix

To obtain the format associated with the color space associ-
ated with a specified color string prefix, use XcmsFormatOf-
Prefix.
__
|
XcmsColorFormat XcmsFormatOfPrefix(prefix)
      char *prefix;


prefix	  Specifies the string that contains the color space
	  prefix.
|__

The XcmsFormatOfPrefix function returns the format for the
specified color space prefix (for example, the string
``CIEXYZ'').  The prefix is case-insensitive.  If the color
space is not accessible in the color management system,
XcmsFormatOfPrefix returns XcmsUndefinedFormat.


To obtain the color string prefix associated with the color
space specified by a color format, use XcmsPrefixOfFormat.
__
|
char *XcmsPrefixOfFormat(format)
      XcmsColorFormat format;


format	  Specifies the color specification format.
|__

The XcmsPrefixOfFormat function returns the string prefix
associated with the color specification encoding specified
by the format argument.  Otherwise, if no encoding is found,
it returns NULL.  The returned string must be treated as
read-only.

6.12.4.  Creating Additional Color Spaces

Color space specific information necessary for color space
conversion and color string parsing is stored in an XcmsCol-
orSpace structure.  Therefore, a new structure containing
this information is required for each additional color
space.	In the case of device-independent color spaces, a
handle to this new structure (that is, by means of a global
variable) is usually made accessible to the client program
for use with the XcmsAddColorSpace function.

If a new XcmsColorSpace structure specifies a color space
not registered with the X Consortium, they should be treated
as private to the client because format values for unregis-
tered color spaces are assigned at run time.  If references



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to an unregistered color space must be made outside the
client (for example, storing color specifications in a file
using the unregistered color space), then reference should
be made by color space prefix (see XcmsFormatOfPrefix and
XcmsPrefixOfFormat).
__
|

typedef (*XcmsConversionProc)();
typedef XcmsConversionProc *XcmsFuncListPtr;
			 /* A NULL terminated list of function pointers*/

typedef struct _XcmsColorSpace {
     char *prefix;
     XcmsColorFormat format;
     XcmsParseStringProc parseString;
     XcmsFuncListPtr to_CIEXYZ;
     XcmsFuncListPtr from_CIEXYZ;
     int inverse_flag;
} XcmsColorSpace;

|__

The prefix member specifies the prefix that indicates a
color string is in this color space's string format.  For
example, the strings ``ciexyz'' or ``CIEXYZ'' for CIE XYZ,
and ``rgb'' or ``RGB'' for RGB.  The prefix is case insensi-
tive.  The format member specifies the color specification
format.  Formats for unregistered color spaces are assigned
at run time.  The parseString member contains a pointer to
the function that can parse a color string into an XcmsColor
structure.  This function returns an integer (int): nonzero
if it succeeded and zero otherwise.  The to_CIEXYZ and
from_CIEXYZ members contain pointers, each to a NULL termi-
nated list of function pointers.  When the list of functions
is executed in series, it will convert the color specified
in an XcmsColor structure from/to the current color space
format to/from the CIE XYZ format.  Each function returns an
integer (int): nonzero if it succeeded and zero otherwise.
The white point to be associated with the colors is speci-
fied explicitly, even though white points can be found in
the CCC.  The inverse_flag member, if nonzero, specifies
that for each function listed in to_CIEXYZ, its inverse
function can be found in from_CIEXYZ such that:


Given:	n = number of functions in each list

for each i, such that 0 <= i < n
    from_CIEXYZ[n - i - 1] is the inverse of to_CIEXYZ[i].


This allows Xlib to use the shortest conversion path, thus
bypassing CIE XYZ if possible (for example, TekHVC to CIE



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L*u*v*).

6.12.5.  Parse String Callback

The callback in the XcmsColorSpace structure for parsing a
color string for the particular color space must adhere to
the following software interface specification:
__
|
typedef int (*XcmsParseStringProc)(color_string, color_return)
      char *color_string;
      XcmsColor *color_return;


color_string
	  Specifies the color string to parse.

color_return
	  Returns the color specification in the color
	  space's format.
|__


6.12.6.  Color Specification Conversion Callback

Callback functions in the XcmsColorSpace structure for con-
verting a color specification between device-independent
spaces must adhere to the following software interface spec-
ification:




























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__
|
Status ConversionProc(ccc, white_point, colors_in_out, ncolors)
      XcmsCCC ccc;
      XcmsColor *white_point;
      XcmsColor *colors_in_out;
      unsigned int ncolors;


ccc	  Specifies the CCC.

white_point
	  Specifies the white point associated with color
	  specifications.  The pixel member should be
	  ignored, and the entire structure remain unchanged
	  upon return.

colors_in_out
	  Specifies an array of color specifications.  Pixel
	  members should be ignored and must remain
	  unchanged upon return.

ncolors   Specifies the number of XcmsColor structures in
	  the color-specification array.
|__


Callback functions in the XcmsColorSpace structure for con-
verting a color specification to or from a device-dependent
space must adhere to the following software interface speci-
fication:



























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__
|
Status ConversionProc(ccc, colors_in_out, ncolors, compression_flags_return)
      XcmsCCC ccc;
      XcmsColor *colors_in_out;
      unsigned int ncolors;
      Bool compression_flags_return[];


ccc	  Specifies the CCC.

colors_in_out
	  Specifies an array of color specifications.  Pixel
	  members should be ignored and must remain
	  unchanged upon return.

ncolors   Specifies the number of XcmsColor structures in
	  the color-specification array.

compression_flags_return
	  Returns an array of Boolean values for indicating
	  compression status.  If a non-NULL pointer is sup-
	  plied and a color at a given index is compressed,
	  then True should be stored at the corresponding
	  index in this array; otherwise, the array should
	  not be modified.
|__

Conversion functions are available globally for use by other
color spaces.  The conversion functions provided by Xlib
are:

-------------------------------------------------------------
Function	     Converts from	  Converts to
-------------------------------------------------------------
XcmsCIELabToCIEXYZ   XcmsCIELabFormat	  XcmsCIEXYZFormat
XcmsCIELuvToCIEuvY   XcmsCIELuvFormat	  XcmsCIEuvYFormat
XcmsCIEXYZToCIELab   XcmsCIEXYZFormat	  XcmsCIELabFormat
XcmsCIEXYZToCIEuvY   XcmsCIEXYZFormat	  XcmsCIEuvYFormat
XcmsCIEXYZToCIExyY   XcmsCIEXYZFormat	  XcmsCIExyYFormat
XcmsCIEXYZToRGBi     XcmsCIEXYZFormat	  XcmsRGBiFormat
XcmsCIEuvYToCIELuv   XcmsCIEuvYFormat	  XcmsCIELabFormat
XcmsCIEuvYToCIEXYZ   XcmsCIEuvYFormat	  XcmsCIEXYZFormat
XcmsCIEuvYToTekHVC   XcmsCIEuvYFormat	  XcmsTekHVCFormat
XcmsCIExyYToCIEXYZ   XcmsCIExyYFormat	  XcmsCIEXYZFormat
XcmsRGBToRGBi	     XcmsRGBFormat	  XcmsRGBiFormat
XcmsRGBiToCIEXYZ     XcmsRGBiFormat	  XcmsCIEXYZFormat
XcmsRGBiToRGB	     XcmsRGBiFormat	  XcmsRGBFormat
XcmsTekHVCToCIEuvY   XcmsTekHVCFormat	  XcmsCIEuvYFormat
-------------------------------------------------------------








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6.12.7.  Function Sets

Functions to convert between device-dependent color spaces
and CIE XYZ may differ for different classes of output
devices (for example, color versus gray monitors).  There-
fore, the notion of a Color Characterization Function Set
has been developed.  A function set consists of device-
dependent color spaces and the functions that convert color
specifications between these device-dependent color spaces
and the CIE XYZ color space appropriate for a particular
class of output devices.  The function set also contains a
function that reads color characterization data off root
window properties.  It is this characterization data that
will differ between devices within a class of output
devices.  For details about how color characterization data
is stored in root window properties, see the section on
Device Color Characterization in the Inter-Client Communica-
tion Conventions Manual.  The LINEAR_RGB function set is
provided by Xlib and will support most color monitors.
Function sets may require data that differs from those
needed for the LINEAR_RGB function set.  In that case, its
corresponding data may be stored on different root window
properties.

6.12.8.  Adding Function Sets

To add a function set, use XcmsAddFunctionSet.
__
|
Status XcmsAddFunctionSet(function_set)
      XcmsFunctionSet *function_set;


function_set
	  Specifies the function set to add.
|__

The XcmsAddFunctionSet function adds a function set to the
color management system.  If the function set uses device-
dependent XcmsColorSpace structures not accessible in the
color management system, XcmsAddFunctionSet adds them.	If
an added XcmsColorSpace structure is for a device-dependent
color space not registered with the X Consortium, they
should be treated as private to the client because format
values for unregistered color spaces are assigned at run
time.  If references to an unregistered color space must be
made outside the client (for example, storing color specifi-
cations in a file using the unregistered color space), then
reference should be made by color space prefix (see XcmsFor-
matOfPrefix and XcmsPrefixOfFormat).

Additional function sets should be added before any calls to
other Xlib routines are made.  If not, the XcmsPerScrnInfo
member of a previously created XcmsCCC does not have the



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opportunity to initialize with the added function set.

6.12.9.  Creating Additional Function Sets

The creation of additional function sets should be required
only when an output device does not conform to existing
function sets or when additional device-dependent color
spaces are necessary.  A function set consists primarily of
a collection of device-dependent XcmsColorSpace structures
and a means to read and store a screen's color characteriza-
tion data.  This data is stored in an XcmsFunctionSet struc-
ture.  A handle to this structure (that is, by means of
global variable) is usually made accessible to the client
program for use with XcmsAddFunctionSet.

If a function set uses new device-dependent XcmsColorSpace
structures, they will be transparently processed into the
color management system.  Function sets can share an Xcms-
ColorSpace structure for a device-dependent color space.  In
addition, multiple XcmsColorSpace structures are allowed for
a device-dependent color space; however, a function set can
reference only one of them.  These XcmsColorSpace structures
will differ in the functions to convert to and from CIE XYZ,
thus tailored for the specific function set.
__
|

typedef struct _XcmsFunctionSet {
     XcmsColorSpace **DDColorSpaces;
     XcmsScreenInitProc screenInitProc;
     XcmsScreenFreeProc screenFreeProc;
} XcmsFunctionSet;

|__

The DDColorSpaces member is a pointer to a NULL terminated
list of pointers to XcmsColorSpace structures for the
device-dependent color spaces that are supported by the
function set.  The screenInitProc member is set to the call-
back procedure (see the following interface specification)
that initializes the XcmsPerScrnInfo structure for a partic-
ular screen.

The screen initialization callback must adhere to the fol-
lowing software interface specification:












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__
|
typedef Status (*XcmsScreenInitProc)(display, screen_number, screen_info)
      Display *display;
      int screen_number;
      XcmsPerScrnInfo *screen_info;


display   Specifies the connection to the X server.

screen_number
	  Specifies the appropriate screen number on the
	  host server.

screen_info
	  Specifies the XcmsPerScrnInfo structure, which
	  contains the per screen information.
|__

The screen initialization callback in the XcmsFunctionSet
structure fetches the color characterization data (device
profile) for the specified screen, typically off properties
on the screen's root window.  It then initializes the speci-
fied XcmsPerScrnInfo structure.  If successful, the proce-
dure fills in the XcmsPerScrnInfo structure as follows:

o    It sets the screenData member to the address of the
     created device profile data structure (contents known
     only by the function set).

o    It next sets the screenWhitePoint member.

o    It next sets the functionSet member to the address of
     the XcmsFunctionSet structure.

o    It then sets the state member to XcmsInitSuccess and
     finally returns XcmsSuccess.

If unsuccessful, the procedure sets the state member to Xcm-
sInitFailure and returns XcmsFailure.

The XcmsPerScrnInfo structure contains:
















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__
|

typedef struct _XcmsPerScrnInfo {
     XcmsColor screenWhitePoint;
     XPointer functionSet;
     XPointer screenData;
     unsigned char state;
     char pad[3];
} XcmsPerScrnInfo;

|__

The screenWhitePoint member specifies the white point inher-
ent to the screen.  The functionSet member specifies the
appropriate function set.  The screenData member specifies
the device profile.  The state member is set to one of the
following:

o    XcmsInitNone indicates initialization has not been pre-
     viously attempted.

o    XcmsInitFailure indicates initialization has been pre-
     viously attempted but failed.

o    XcmsInitSuccess indicates initialization has been pre-
     viously attempted and succeeded.

The screen free callback must adhere to the following soft-
ware interface specification:
__
|
typedef void (*XcmsScreenFreeProc)(screenData)
      XPointer screenData;


screenData
	  Specifies the data to be freed.
|__

This function is called to free the screenData stored in an
XcmsPerScrnInfo structure.
















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			 Chapter 7

		 Graphics Context Functions



A number of resources are used when performing graphics
operations in X.  Most information about performing graphics
(for example, foreground color, background color, line
style, and so on) is stored in resources called graphics
contexts (GCs).  Most graphics operations (see chapter 8)
take a GC as an argument.  Although in theory the X protocol
permits sharing of GCs between applications, it is expected
that applications will use their own GCs when performing
operations.  Sharing of GCs is highly discouraged because
the library may cache GC state.

Graphics operations can be performed to either windows or
pixmaps, which collectively are called drawables.  Each
drawable exists on a single screen.  A GC is created for a
specific screen and drawable depth and can only be used with
drawables of matching screen and depth.

This chapter discusses how to:

o    Manipulate graphics context/state

o    Use graphics context convenience functions

7.1.  Manipulating Graphics Context/State

Most attributes of graphics operations are stored in GCs.
These include line width, line style, plane mask, fore-
ground, background, tile, stipple, clipping region, end
style, join style, and so on.  Graphics operations (for
example, drawing lines) use these values to determine the
actual drawing operation.  Extensions to X may add addi-
tional components to GCs.  The contents of a GC are private
to Xlib.

Xlib implements a write-back cache for all elements of a GC
that are not resource IDs to allow Xlib to implement the
transparent coalescing of changes to GCs.  For example, a
call to XSetForeground of a GC followed by a call to XSet-
LineAttributes results in only a single-change GC protocol
request to the server.	GCs are neither expected nor encour-
aged to be shared between client applications, so this
write-back caching should present no problems.	Applications
cannot share GCs without external synchronization.  There-
fore, sharing GCs between applications is highly discour-
aged.




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To set an attribute of a GC, set the appropriate member of
the XGCValues structure and OR in the corresponding value
bitmask in your subsequent calls to XCreateGC.	The symbols
for the value mask bits and the XGCValues structure are:





















































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__
|
/* GC attribute value mask bits */

#define   GCFunction		      (1L<<0)
#define   GCPlaneMask		      (1L<<1)
#define   GCForeground		      (1L<<2)
#define   GCBackground		      (1L<<3)
#define   GCLineWidth		      (1L<<4)
#define   GCLineStyle		      (1L<<5)
#define   GCCapStyle		      (1L<<6)
#define   GCJoinStyle		      (1L<<7)
#define   GCFillStyle		      (1L<<8)
#define   GCFillRule		      (1L<<9)
#define   GCTile		      (1L<<10)
#define   GCStipple		      (1L<<11)
#define   GCTileStipXOrigin	      (1L<<12)
#define   GCTileStipYOrigin	      (1L<<13)
#define   GCFont		      (1L<<14)
#define   GCSubwindowMode	      (1L<<15)
#define   GCGraphicsExposures	      (1L<<16)
#define   GCClipXOrigin 	      (1L<<17)
#define   GCClipYOrigin 	      (1L<<18)
#define   GCClipMask		      (1L<<19)
#define   GCDashOffset		      (1L<<20)
#define   GCDashList		      (1L<<21)
#define   GCArcMode		      (1L<<22)


/* Values */

typedef struct {
     int function;	      /* logical operation */
     unsigned long plane_mask;/* plane mask */
     unsigned long foreground;/* foreground pixel */
     unsigned long background;/* background pixel */
     int line_width;	      /* line width (in pixels) */
     int line_style;	      /* LineSolid, LineOnOffDash, LineDoubleDash */
     int cap_style;	      /* CapNotLast, CapButt, CapRound, CapProjecting */
     int join_style;	      /* JoinMiter, JoinRound, JoinBevel */
     int fill_style;	      /* FillSolid, FillTiled, FillStippled FillOpaqueStippled*/
     int fill_rule;	      /* EvenOddRule, WindingRule */
     int arc_mode;	      /* ArcChord, ArcPieSlice */
     Pixmap tile;	      /* tile pixmap for tiling operations */
     Pixmap stipple;	      /* stipple 1 plane pixmap for stippling */
     int ts_x_origin;	      /* offset for tile or stipple operations */
     int ts_y_origin;
     Font font; 	      /* default text font for text operations */
     int subwindow_mode;      /* ClipByChildren, IncludeInferiors */
     Bool graphics_exposures; /* boolean, should exposures be generated */
     int clip_x_origin;       /* origin for clipping */
     int clip_y_origin;
     Pixmap clip_mask;	      /* bitmap clipping; other calls for rects */
     int dash_offset;	      /* patterned/dashed line information */
     char dashes;



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} XGCValues;

|__

The default GC values are:

----------------------------------------------------------------------------------
Component	     Default
----------------------------------------------------------------------------------
function	     GXcopy
plane_mask	     All ones
foreground	     0
background	     1
line_width	     0
line_style	     LineSolid
cap_style	     CapButt
join_style	     JoinMiter
fill_style	     FillSolid
fill_rule	     EvenOddRule
arc_mode	     ArcPieSlice
tile		     Pixmap of unspecified size filled with foreground pixel
		     (that is, client specified pixel if any, else 0)
		     (subsequent changes to foreground do not affect this pixmap)
stipple 	     Pixmap of unspecified size filled with ones
ts_x_origin	     0
ts_y_origin	     0
font		     <implementation dependent>
subwindow_mode	     ClipByChildren
graphics_exposures   True
clip_x_origin	     0
clip_y_origin	     0
clip_mask	     None
dash_offset	     0
dashes		     4 (that is, the list [4, 4])
----------------------------------------------------------------------------------


Note that foreground and background are not set to any val-
ues likely to be useful in a window.

The function attributes of a GC are used when you update a
section of a drawable (the destination) with bits from some-
where else (the source).  The function in a GC defines how
the new destination bits are to be computed from the source
bits and the old destination bits.  GXcopy is typically the
most useful because it will work on a color display, but
special applications may use other functions, particularly
in concert with particular planes of a color display.  The
16 GC functions, defined in <X11/X.h>, are:








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-----------------------------------------------
Function Name	  Value   Operation
-----------------------------------------------
GXclear 	   0x0	  0
GXand		   0x1	  src AND dst
GXandReverse	   0x2	  src AND NOT dst
GXcopy		   0x3	  src
GXandInverted	   0x4	  (NOT src) AND dst
GXnoop		   0x5	  dst
GXxor		   0x6	  src XOR dst
GXor		   0x7	  src OR dst
GXnor		   0x8	  (NOT src) AND (NOT
			  dst)
GXequiv 	   0x9	  (NOT src) XOR dst
GXinvert	   0xa	  NOT dst
GXorReverse	   0xb	  src OR (NOT dst)
GXcopyInverted	   0xc	  NOT src
GXorInverted	   0xd	  (NOT src) OR dst
GXnand		   0xe	  (NOT src) OR (NOT
			  dst)
GXset		   0xf	  1
-----------------------------------------------


Many graphics operations depend on either pixel values or
planes in a GC.  The planes attribute is of type long, and
it specifies which planes of the destination are to be modi-
fied, one bit per plane.  A monochrome display has only one
plane and will be the least significant bit of the word.  As
planes are added to the display hardware, they will occupy
more significant bits in the plane mask.

In graphics operations, given a source and destination
pixel, the result is computed bitwise on corresponding bits
of the pixels.	That is, a Boolean operation is performed in
each bit plane.  The plane_mask restricts the operation to a
subset of planes.  A macro constant AllPlanes can be used to
refer to all planes of the screen simultaneously.  The
result is computed by the following:


     ((src FUNC dst) AND plane-mask) OR (dst AND (NOT plane-mask))


Range checking is not performed on the values for fore-
ground, background, or plane_mask.  They are simply trun-
cated to the appropriate number of bits.  The line-width is
measured in pixels and either can be greater than or equal
to one (wide line) or can be the special value zero (thin
line).

Wide lines are drawn centered on the path described by the
graphics request.  Unless otherwise specified by the join-
style or cap-style, the bounding box of a wide line with



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endpoints [x1, y1], [x2, y2] and width w is a rectangle with
vertices at the following real coordinates:


     [x1-(w*sn/2), y1+(w*cs/2)], [x1+(w*sn/2), y1-(w*cs/2)],
     [x2-(w*sn/2), y2+(w*cs/2)], [x2+(w*sn/2), y2-(w*cs/2)]


Here sn is the sine of the angle of the line, and cs is the
cosine of the angle of the line.  A pixel is part of the
line and so is drawn if the center of the pixel is fully
inside the bounding box (which is viewed as having
infinitely thin edges).  If the center of the pixel is
exactly on the bounding box, it is part of the line if and
only if the interior is immediately to its right (x increas-
ing direction).  Pixels with centers on a horizontal edge
are a special case and are part of the line if and only if
the interior or the boundary is immediately below (y
increasing direction) and the interior or the boundary is
immediately to the right (x increasing direction).

Thin lines (zero line-width) are one-pixel-wide lines drawn
using an unspecified, device-dependent algorithm.  There are
only two constraints on this algorithm.

1.   If a line is drawn unclipped from [x1,y1] to [x2,y2]
     and if another line is drawn unclipped from
     [x1+dx,y1+dy] to [x2+dx,y2+dy], a point [x,y] is
     touched by drawing the first line if and only if the
     point [x+dx,y+dy] is touched by drawing the second
     line.

2.   The effective set of points comprising a line cannot be
     affected by clipping.  That is, a point is touched in a
     clipped line if and only if the point lies inside the
     clipping region and the point would be touched by the
     line when drawn unclipped.

A wide line drawn from [x1,y1] to [x2,y2] always draws the
same pixels as a wide line drawn from [x2,y2] to [x1,y1],
not counting cap-style and join-style.	It is recommended
that this property be true for thin lines, but this is not
required.  A line-width of zero may differ from a line-width
of one in which pixels are drawn.  This permits the use of
many manufacturers' line drawing hardware, which may run
many times faster than the more precisely specified wide
lines.

In general, drawing a thin line will be faster than drawing
a wide line of width one.  However, because of their differ-
ent drawing algorithms, thin lines may not mix well aesthet-
ically with wide lines.  If it is desirable to obtain pre-
cise and uniform results across all displays, a client
should always use a line-width of one rather than a line-



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width of zero.

The line-style defines which sections of a line are drawn:

LineSolid	The full path of the line is drawn.
LineDou-	The full path of the line is drawn, but the
bleDash 	even dashes are filled differently from the
		odd dashes (see fill-style) with CapButt
		style used where even and odd dashes meet.
LineOnOffDash	Only the even dashes are drawn, and cap-style
		applies to all internal ends of the individ-
		ual dashes, except CapNotLast is treated as
		CapButt.


The cap-style defines how the endpoints of a path are drawn:

CapNotLast	This is equivalent to CapButt except that for
		a line-width of zero the final endpoint is
		not drawn.
CapButt 	The line is square at the endpoint (perpen-
		dicular to the slope of the line) with no
		projection beyond.
CapRound	The line has a circular arc with the diameter
		equal to the line-width, centered on the end-
		point.	(This is equivalent to CapButt for
		line-width of zero).
CapProjecting	The line is square at the end, but the path
		continues beyond the endpoint for a distance
		equal to half the line-width.  (This is
		equivalent to CapButt for line-width of
		zero).


The join-style defines how corners are drawn for wide lines:

JoinMiter	The outer edges of two lines extend to meet
		at an angle.  However, if the angle is less
		than 11 degrees, then a JoinBevel join-style
		is used instead.
JoinRound	The corner is a circular arc with the diame-
		ter equal to the line-width, centered on the
		joinpoint.
JoinBevel	The corner has CapButt endpoint styles with
		the triangular notch filled.


For a line with coincident endpoints (x1=x2, y1=y2), when
the cap-style is applied to both endpoints, the semantics
depends on the line-width and the cap-style:







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CapNotLast	thin	The results are device dependent, but
			the desired effect is that nothing is
			drawn.
CapButt 	thin	The results are device dependent, but
			the desired effect is that a single
			pixel is drawn.
CapRound	thin	The results are the same as for Cap-
			Butt/thin.
CapProjecting	thin	The results are the same as for Cap-
			Butt/thin.
CapButt 	wide	Nothing is drawn.
CapRound	wide	The closed path is a circle, centered at
			the endpoint, and with the diameter
			equal to the line-width.
CapProjecting	wide	The closed path is a square, aligned
			with the coordinate axes, centered at
			the endpoint, and with the sides equal
			to the line-width.


For a line with coincident endpoints (x1=x2, y1=y2), when
the join-style is applied at one or both endpoints, the
effect is as if the line was removed from the overall path.
However, if the total path consists of or is reduced to a
single point joined with itself, the effect is the same as
when the cap-style is applied at both endpoints.

The tile/stipple represents an infinite two-dimensional
plane, with the tile/stipple replicated in all dimensions.
When that plane is superimposed on the drawable for use in a
graphics operation, the upper-left corner of some instance
of the tile/stipple is at the coordinates within the draw-
able specified by the tile/stipple origin.  The tile/stipple
and clip origins are interpreted relative to the origin of
whatever destination drawable is specified in a graphics
request.  The tile pixmap must have the same root and depth
as the GC, or a BadMatch error results.  The stipple pixmap
must have depth one and must have the same root as the GC,
or a BadMatch error results.  For stipple operations where
the fill-style is FillStippled but not FillOpaqueStippled,
the stipple pattern is tiled in a single plane and acts as
an additional clip mask to be ANDed with the clip-mask.
Although some sizes may be faster to use than others, any
size pixmap can be used for tiling or stippling.

The fill-style defines the contents of the source for line,
text, and fill requests.  For all text and fill requests
(for example, XDrawText, XDrawText16, XFillRectangle,
XFillPolygon, and XFillArc); for line requests with line-
style LineSolid (for example, XDrawLine, XDrawSegments,
XDrawRectangle, XDrawArc); and for the even dashes for line
requests with line-style LineOnOffDash or LineDoubleDash,
the following apply:




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FillSolid	     Foreground
FillTiled	     Tile
FillOpaqueStippled   A tile with the same width and height as
		     stipple, but with background everywhere
		     stipple has a zero and with foreground
		     everywhere stipple has a one
FillStippled	     Foreground masked by stipple


When drawing lines with line-style LineDoubleDash, the odd
dashes are controlled by the fill-style in the following
manner:

FillSolid	     Background
FillTiled	     Same as for even dashes
FillOpaqueStippled   Same as for even dashes
FillStippled	     Background masked by stipple


Storing a pixmap in a GC might or might not result in a copy
being made.  If the pixmap is later used as the destination
for a graphics request, the change might or might not be
reflected in the GC.  If the pixmap is used simultaneously
in a graphics request both as a destination and as a tile or
stipple, the results are undefined.

For optimum performance, you should draw as much as possible
with the same GC (without changing its components).  The
costs of changing GC components relative to using different
GCs depend on the display hardware and the server implemen-
tation.  It is quite likely that some amount of GC informa-
tion will be cached in display hardware and that such hard-
ware can only cache a small number of GCs.

The dashes value is actually a simplified form of the more
general patterns that can be set with XSetDashes.  Specify-
ing a value of N is equivalent to specifying the two-element
list [N, N] in XSetDashes.  The value must be nonzero, or a
BadValue error results.

The clip-mask restricts writes to the destination drawable.
If the clip-mask is set to a pixmap, it must have depth one
and have the same root as the GC, or a BadMatch error
results.  If clip-mask is set to None, the pixels are always
drawn regardless of the clip origin.  The clip-mask also can
be set by calling the XSetClipRectangles or XSetRegion func-
tions.	Only pixels where the clip-mask has a bit set to 1
are drawn.  Pixels are not drawn outside the area covered by
the clip-mask or where the clip-mask has a bit set to 0.
The clip-mask affects all graphics requests.  The clip-mask
does not clip sources.	The clip-mask origin is interpreted
relative to the origin of whatever destination drawable is
specified in a graphics request.




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You can set the subwindow-mode to ClipByChildren or Include-
Inferiors.  For ClipByChildren, both source and destination
windows are additionally clipped by all viewable InputOutput
children.  For IncludeInferiors, neither source nor destina-
tion window is clipped by inferiors.  This will result in
including subwindow contents in the source and drawing
through subwindow boundaries of the destination.  The use of
IncludeInferiors on a window of one depth with mapped infe-
riors of differing depth is not illegal, but the semantics
are undefined by the core protocol.

The fill-rule defines what pixels are inside (drawn) for
paths given in XFillPolygon requests and can be set to Even-
OddRule or WindingRule.  For EvenOddRule, a point is inside
if an infinite ray with the point as origin crosses the path
an odd number of times.  For WindingRule, a point is inside
if an infinite ray with the point as origin crosses an
unequal number of clockwise and counterclockwise directed
path segments.	A clockwise directed path segment is one
that crosses the ray from left to right as observed from the
point.	A counterclockwise segment is one that crosses the
ray from right to left as observed from the point.  The case
where a directed line segment is coincident with the ray is
uninteresting because you can simply choose a different ray
that is not coincident with a segment.

For both EvenOddRule and WindingRule, a point is infinitely
small, and the path is an infinitely thin line.  A pixel is
inside if the center point of the pixel is inside and the
center point is not on the boundary.  If the center point is
on the boundary, the pixel is inside if and only if the
polygon interior is immediately to its right (x increasing
direction).  Pixels with centers on a horizontal edge are a
special case and are inside if and only if the polygon inte-
rior is immediately below (y increasing direction).

The arc-mode controls filling in the XFillArcs function and
can be set to ArcPieSlice or ArcChord.	For ArcPieSlice, the
arcs are pie-slice filled.  For ArcChord, the arcs are chord
filled.

The graphics-exposure flag controls GraphicsExpose event
generation for XCopyArea and XCopyPlane requests (and any
similar requests defined by extensions).


To create a new GC that is usable on a given screen with a
depth of drawable, use XCreateGC.









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__
|
GC XCreateGC(display, d, valuemask, values)
      Display *display;
      Drawable d;
      unsigned long valuemask;
      XGCValues *values;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

valuemask Specifies which components in the GC are to be set
	  using the information in the specified values
	  structure.  This argument is the bitwise inclusive
	  OR of zero or more of the valid GC component mask
	  bits.

values	  Specifies any values as specified by the value-
	  mask.
|__

The XCreateGC function creates a graphics context and
returns a GC.  The GC can be used with any destination draw-
able having the same root and depth as the specified draw-
able.  Use with other drawables results in a BadMatch error.

XCreateGC can generate BadAlloc, BadDrawable, BadFont, Bad-
Match, BadPixmap, and BadValue errors.


To copy components from a source GC to a destination GC, use
XCopyGC.
__
|
XCopyGC(display, src, valuemask, dest)
      Display *display;
      GC src, dest;
      unsigned long valuemask;


display   Specifies the connection to the X server.

src	  Specifies the components of the source GC.

valuemask Specifies which components in the GC are to be
	  copied to the destination GC.  This argument is
	  the bitwise inclusive OR of zero or more of the
	  valid GC component mask bits.

dest	  Specifies the destination GC.
|__

The XCopyGC function copies the specified components from



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the source GC to the destination GC.  The source and desti-
nation GCs must have the same root and depth, or a BadMatch
error results.	The valuemask specifies which component to
copy, as for XCreateGC.

XCopyGC can generate BadAlloc, BadGC, and BadMatch errors.


To change the components in a given GC, use XChangeGC.
__
|
XChangeGC(display, gc, valuemask, values)
      Display *display;
      GC gc;
      unsigned long valuemask;
      XGCValues *values;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

valuemask Specifies which components in the GC are to be
	  changed using information in the specified values
	  structure.  This argument is the bitwise inclusive
	  OR of zero or more of the valid GC component mask
	  bits.

values	  Specifies any values as specified by the value-
	  mask.
|__

The XChangeGC function changes the components specified by
valuemask for the specified GC.  The values argument con-
tains the values to be set.  The values and restrictions are
the same as for XCreateGC.  Changing the clip-mask overrides
any previous XSetClipRectangles request on the context.
Changing the dash-offset or dash-list overrides any previous
XSetDashes request on the context.  The order in which com-
ponents are verified and altered is server dependent.  If an
error is generated, a subset of the components may have been
altered.

XChangeGC can generate BadAlloc, BadFont, BadGC, BadMatch,
BadPixmap, and BadValue errors.


To obtain components of a given GC, use XGetGCValues.









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__
|
Status XGetGCValues(display, gc, valuemask, values_return)
      Display *display;
      GC gc;
      unsigned long valuemask;
      XGCValues *values_return;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

valuemask Specifies which components in the GC are to be
	  returned in the values_return argument.  This
	  argument is the bitwise inclusive OR of zero or
	  more of the valid GC component mask bits.

values_return
	  Returns the GC values in the specified XGCValues
	  structure.
|__

The XGetGCValues function returns the components specified
by valuemask for the specified GC.  If the valuemask con-
tains a valid set of GC mask bits (GCFunction, GCPlaneMask,
GCForeground, GCBackground, GCLineWidth, GCLineStyle, GCCap-
Style, GCJoinStyle, GCFillStyle, GCFillRule, GCTile, GCStip-
ple, GCTileStipXOrigin, GCTileStipYOrigin, GCFont, GCSubwin-
dowMode, GCGraphicsExposures, GCClipXOrigin, GCCLipYOrigin,
GCDashOffset, or GCArcMode) and no error occurs, XGetGCVal-
ues sets the requested components in values_return and
returns a nonzero status.  Otherwise, it returns a zero sta-
tus.  Note that the clip-mask and dash-list (represented by
the GCClipMask and GCDashList bits, respectively, in the
valuemask) cannot be requested.  Also note that an invalid
resource ID (with one or more of the three most significant
bits set to 1) will be returned for GCFont, GCTile, and
GCStipple if the component has never been explicitly set by
the client.


To free a given GC, use XFreeGC.















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__
|
XFreeGC(display, gc)
      Display *display;
      GC gc;


display   Specifies the connection to the X server.

gc	  Specifies the GC.
|__

The XFreeGC function destroys the specified GC as well as
all the associated storage.

XFreeGC can generate a BadGC error.


To obtain the GContext resource ID for a given GC, use
XGContextFromGC.
__
|
GContext XGContextFromGC(gc)
      GC gc;


gc	  Specifies the GC for which you want the resource
	  ID.
|__


Xlib usually defers sending changes to the components of a
GC to the server until a graphics function is actually
called with that GC.  This permits batching of component
changes into a single server request.  In some circum-
stances, however, it may be necessary for the client to
explicitly force sending the changes to the server.  An
example might be when a protocol extension uses the GC indi-
rectly, in such a way that the extension interface cannot
know what GC will be used.  To force sending GC component
changes, use XFlushGC.
__
|
void XFlushGC(display, gc)
      Display *display;
      GC gc;


display   Specifies the connection to the X server.

gc	  Specifies the GC.
|__






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7.2.  Using Graphics Context Convenience Routines

This section discusses how to set the:

o    Foreground, background, plane mask, or function compo-
     nents

o    Line attributes and dashes components

o    Fill style and fill rule components

o    Fill tile and stipple components

o    Font component

o    Clip region component

o    Arc mode, subwindow mode, and graphics exposure compo-
     nents

7.2.1.	Setting the Foreground, Background, Function, or
Plane Mask

To set the foreground, background, plane mask, and function
components for a given GC, use XSetState.
































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__
|
XSetState(display, gc, foreground, background, function, plane_mask)
      Display *display;
      GC gc;
      unsigned long foreground, background;
      int function;
      unsigned long plane_mask;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

foreground
	  Specifies the foreground you want to set for the
	  specified GC.

background
	  Specifies the background you want to set for the
	  specified GC.

function  Specifies the function you want to set for the
	  specified GC.

plane_mask
	  Specifies the plane mask.
|__

XSetState can generate BadAlloc, BadGC, and BadValue errors.


To set the foreground of a given GC, use XSetForeground.
__
|
XSetForeground(display, gc, foreground)
      Display *display;
      GC gc;
      unsigned long foreground;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

foreground
	  Specifies the foreground you want to set for the
	  specified GC.
|__

XSetForeground can generate BadAlloc and BadGC errors.


To set the background of a given GC, use XSetBackground.




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__
|
XSetBackground(display, gc, background)
      Display *display;
      GC gc;
      unsigned long background;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

background
	  Specifies the background you want to set for the
	  specified GC.
|__

XSetBackground can generate BadAlloc and BadGC errors.


To set the display function in a given GC, use XSetFunction.
__
|
XSetFunction(display, gc, function)
      Display *display;
      GC gc;
      int function;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

function  Specifies the function you want to set for the
	  specified GC.
|__

XSetFunction can generate BadAlloc, BadGC, and BadValue
errors.


To set the plane mask of a given GC, use XSetPlaneMask.
















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__
|
XSetPlaneMask(display, gc, plane_mask)
      Display *display;
      GC gc;
      unsigned long plane_mask;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

plane_mask
	  Specifies the plane mask.
|__

XSetPlaneMask can generate BadAlloc and BadGC errors.

7.2.2.	Setting the Line Attributes and Dashes

To set the line drawing components of a given GC, use XSet-
LineAttributes.




































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__
|
XSetLineAttributes(display, gc, line_width, line_style, cap_style, join_style)
      Display *display;
      GC gc;
      unsigned int line_width;
      int line_style;
      int cap_style;
      int join_style;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

line_width
	  Specifies the line-width you want to set for the
	  specified GC.

line_style
	  Specifies the line-style you want to set for the
	  specified GC.  You can pass LineSolid, LineOnOff-
	  Dash, or LineDoubleDash.

cap_style Specifies the line-style and cap-style you want to
	  set for the specified GC.  You can pass CapNot-
	  Last, CapButt, CapRound, or CapProjecting.

join_style
	  Specifies the line join-style you want to set for
	  the specified GC.  You can pass JoinMiter, Join-
	  Round, or JoinBevel.
|__

XSetLineAttributes can generate BadAlloc, BadGC, and Bad-
Value errors.


To set the dash-offset and dash-list for dashed line styles
of a given GC, use XSetDashes.


















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__
|
XSetDashes(display, gc, dash_offset, dash_list, n)
	Display *display;
	GC gc;
	int dash_offset;
	char dash_list[];
	int n;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

dash_offset
	  Specifies the phase of the pattern for the dashed
	  line-style you want to set for the specified GC.

dash_list Specifies the dash-list for the dashed line-style
	  you want to set for the specified GC.

n	  Specifies the number of elements in dash_list.
|__

The XSetDashes function sets the dash-offset and dash-list
attributes for dashed line styles in the specified GC.
There must be at least one element in the specified
dash_list, or a BadValue error results.  The initial and
alternating elements (second, fourth, and so on) of the
dash_list are the even dashes, and the others are the odd
dashes.  Each element specifies a dash length in pixels.
All of the elements must be nonzero, or a BadValue error
results.  Specifying an odd-length list is equivalent to
specifying the same list concatenated with itself to produce
an even-length list.

The dash-offset defines the phase of the pattern, specifying
how many pixels into the dash-list the pattern should actu-
ally begin in any single graphics request.  Dashing is con-
tinuous through path elements combined with a join-style but
is reset to the dash-offset between each sequence of joined
lines.

The unit of measure for dashes is the same for the ordinary
coordinate system.  Ideally, a dash length is measured along
the slope of the line, but implementations are only required
to match this ideal for horizontal and vertical lines.
Failing the ideal semantics, it is suggested that the length
be measured along the major axis of the line.  The major
axis is defined as the x axis for lines drawn at an angle of
between -45 and +45 degrees or between 135 and 225 degrees
from the x axis.  For all other lines, the major axis is the
y axis.





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XSetDashes can generate BadAlloc, BadGC, and BadValue
errors.

7.2.3.	Setting the Fill Style and Fill Rule

To set the fill-style of a given GC, use XSetFillStyle.
__
|
XSetFillStyle(display, gc, fill_style)
      Display *display;
      GC gc;
      int fill_style;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

fill_style
	  Specifies the fill-style you want to set for the
	  specified GC.  You can pass FillSolid, FillTiled,
	  FillStippled, or FillOpaqueStippled.
|__

XSetFillStyle can generate BadAlloc, BadGC, and BadValue
errors.


To set the fill-rule of a given GC, use XSetFillRule.
__
|
XSetFillRule(display, gc, fill_rule)
      Display *display;
      GC gc;
      int fill_rule;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

fill_rule Specifies the fill-rule you want to set for the
	  specified GC.  You can pass EvenOddRule or Windin-
	  gRule.
|__

XSetFillRule can generate BadAlloc, BadGC, and BadValue
errors.

7.2.4.	Setting the Fill Tile and Stipple

Some displays have hardware support for tiling or stippling
with patterns of specific sizes.  Tiling and stippling oper-
ations that restrict themselves to those specific sizes run



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much faster than such operations with arbitrary size pat-
terns.	Xlib provides functions that you can use to deter-
mine the best size, tile, or stipple for the display as well
as to set the tile or stipple shape and the tile or stipple
origin.


To obtain the best size of a tile, stipple, or cursor, use
XQueryBestSize.
__
|
Status XQueryBestSize(display, class, which_screen, width, height, width_return, height_return)
      Display *display;
      int class;
      Drawable which_screen;
      unsigned int width, height;
      unsigned int *width_return, *height_return;


display   Specifies the connection to the X server.

class	  Specifies the class that you are interested in.
	  You can pass TileShape, CursorShape, or Stipple-
	  Shape.

which_screen
	  Specifies any drawable on the screen.

width
height	  Specify the width and height.

width_return
height_return
	  Return the width and height of the object best
	  supported by the display hardware.
|__

The XQueryBestSize function returns the best or closest size
to the specified size.	For CursorShape, this is the largest
size that can be fully displayed on the screen specified by
which_screen.  For TileShape, this is the size that can be
tiled fastest.	For StippleShape, this is the size that can
be stippled fastest.  For CursorShape, the drawable indi-
cates the desired screen.  For TileShape and StippleShape,
the drawable indicates the screen and possibly the window
class and depth.  An InputOnly window cannot be used as the
drawable for TileShape or StippleShape, or a BadMatch error
results.

XQueryBestSize can generate BadDrawable, BadMatch, and Bad-
Value errors.


To obtain the best fill tile shape, use XQueryBestTile.



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__
|
Status XQueryBestTile(display, which_screen, width, height, width_return, height_return)
      Display *display;
      Drawable which_screen;
      unsigned int width, height;
      unsigned int *width_return, *height_return;


display   Specifies the connection to the X server.

which_screen
	  Specifies any drawable on the screen.

width
height	  Specify the width and height.

width_return
height_return
	  Return the width and height of the object best
	  supported by the display hardware.
|__

The XQueryBestTile function returns the best or closest
size, that is, the size that can be tiled fastest on the
screen specified by which_screen.  The drawable indicates
the screen and possibly the window class and depth.  If an
InputOnly window is used as the drawable, a BadMatch error
results.

XQueryBestTile can generate BadDrawable and BadMatch errors.


To obtain the best stipple shape, use XQueryBestStipple.
























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__
|
Status XQueryBestStipple(display, which_screen, width, height, width_return, height_return)
      Display *display;
      Drawable which_screen;
      unsigned int width, height;
      unsigned int *width_return, *height_return;


display   Specifies the connection to the X server.

which_screen
	  Specifies any drawable on the screen.

width
height	  Specify the width and height.

width_return
height_return
	  Return the width and height of the object best
	  supported by the display hardware.
|__

The XQueryBestStipple function returns the best or closest
size, that is, the size that can be stippled fastest on the
screen specified by which_screen.  The drawable indicates
the screen and possibly the window class and depth.  If an
InputOnly window is used as the drawable, a BadMatch error
results.

XQueryBestStipple can generate BadDrawable and BadMatch
errors.


To set the fill tile of a given GC, use XSetTile.
__
|
XSetTile(display, gc, tile)
      Display *display;
      GC gc;
      Pixmap tile;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

tile	  Specifies the fill tile you want to set for the
	  specified GC.
|__

The tile and GC must have the same depth, or a BadMatch
error results.





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XSetTile can generate BadAlloc, BadGC, BadMatch, and Bad-
Pixmap errors.


To set the stipple of a given GC, use XSetStipple.
__
|
XSetStipple(display, gc, stipple)
      Display *display;
      GC gc;
      Pixmap stipple;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

stipple   Specifies the stipple you want to set for the
	  specified GC.
|__

The stipple must have a depth of one, or a BadMatch error
results.

XSetStipple can generate BadAlloc, BadGC, BadMatch, and Bad-
Pixmap errors.


To set the tile or stipple origin of a given GC, use
XSetTSOrigin.
__
|
XSetTSOrigin(display, gc, ts_x_origin, ts_y_origin)
      Display *display;
      GC gc;
      int ts_x_origin, ts_y_origin;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

ts_x_origin
ts_y_origin
	  Specify the x and y coordinates of the tile and
	  stipple origin.
|__

When graphics requests call for tiling or stippling, the
parent's origin will be interpreted relative to whatever
destination drawable is specified in the graphics request.

XSetTSOrigin can generate BadAlloc and BadGC errors.




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7.2.5.	Setting the Current Font

To set the current font of a given GC, use XSetFont.
__
|
XSetFont(display, gc, font)
      Display *display;
      GC gc;
      Font font;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

font	  Specifies the font.
|__

XSetFont can generate BadAlloc, BadFont, and BadGC errors.

7.2.6.	Setting the Clip Region

Xlib provides functions that you can use to set the clip-
origin and the clip-mask or set the clip-mask to a list of
rectangles.


To set the clip-origin of a given GC, use XSetClipOrigin.
__
|
XSetClipOrigin(display, gc, clip_x_origin, clip_y_origin)
      Display *display;
      GC gc;
      int clip_x_origin, clip_y_origin;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

clip_x_origin
clip_y_origin
	  Specify the x and y coordinates of the clip-mask
	  origin.
|__

The clip-mask origin is interpreted relative to the origin
of whatever destination drawable is specified in the graph-
ics request.

XSetClipOrigin can generate BadAlloc and BadGC errors.


To set the clip-mask of a given GC to the specified pixmap,



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use XSetClipMask.
__
|
XSetClipMask(display, gc, pixmap)
      Display *display;
      GC gc;
      Pixmap pixmap;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

pixmap	  Specifies the pixmap or None.
|__

If the clip-mask is set to None, the pixels are always drawn
(regardless of the clip-origin).

XSetClipMask can generate BadAlloc, BadGC, BadMatch, and
BadPixmap errors.


To set the clip-mask of a given GC to the specified list of
rectangles, use XSetClipRectangles.
































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__
|
XSetClipRectangles(display, gc, clip_x_origin, clip_y_origin, rectangles, n, ordering)
      Display *display;
      GC gc;
      int clip_x_origin, clip_y_origin;
      XRectangle rectangles[];
      int n;
      int ordering;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

clip_x_origin
clip_y_origin
	  Specify the x and y coordinates of the clip-mask
	  origin.

rectangles
	  Specifies an array of rectangles that define the
	  clip-mask.

n	  Specifies the number of rectangles.

ordering  Specifies the ordering relations on the rectan-
	  gles.  You can pass Unsorted, YSorted, YXSorted,
	  or YXBanded.
|__

The XSetClipRectangles function changes the clip-mask in the
specified GC to the specified list of rectangles and sets
the clip origin.  The output is clipped to remain contained
within the rectangles.	The clip-origin is interpreted rela-
tive to the origin of whatever destination drawable is spec-
ified in a graphics request.  The rectangle coordinates are
interpreted relative to the clip-origin.  The rectangles
should be nonintersecting, or the graphics results will be
undefined.  Note that the list of rectangles can be empty,
which effectively disables output.  This is the opposite of
passing None as the clip-mask in XCreateGC, XChangeGC, and
XSetClipMask.

If known by the client, ordering relations on the rectangles
can be specified with the ordering argument.  This may pro-
vide faster operation by the server.  If an incorrect order-
ing is specified, the X server may generate a BadMatch
error, but it is not required to do so.  If no error is gen-
erated, the graphics results are undefined.  Unsorted means
the rectangles are in arbitrary order.	YSorted means that
the rectangles are nondecreasing in their Y origin.
YXSorted additionally constrains YSorted order in that all
rectangles with an equal Y origin are nondecreasing in their
X origin.  YXBanded additionally constrains YXSorted by



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requiring that, for every possible Y scanline, all rectan-
gles that include that scanline have an identical Y origins
and Y extents.

XSetClipRectangles can generate BadAlloc, BadGC, BadMatch,
and BadValue errors.

Xlib provides a set of basic functions for performing region
arithmetic.  For information about these functions, see sec-
tion 16.5.

7.2.7.	Setting the Arc Mode, Subwindow Mode, and Graphics
Exposure

To set the arc mode of a given GC, use XSetArcMode.
__
|
XSetArcMode(display, gc, arc_mode)
      Display *display;
      GC gc;
      int arc_mode;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

arc_mode  Specifies the arc mode.  You can pass ArcChord or
	  ArcPieSlice.
|__

XSetArcMode can generate BadAlloc, BadGC, and BadValue
errors.


To set the subwindow mode of a given GC, use XSetSubwindow-
Mode.




















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__
|
XSetSubwindowMode(display, gc, subwindow_mode)
      Display *display;
      GC gc;
      int subwindow_mode;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

subwindow_mode
	  Specifies the subwindow mode.  You can pass Clip-
	  ByChildren or IncludeInferiors.
|__

XSetSubwindowMode can generate BadAlloc, BadGC, and BadValue
errors.


To set the graphics-exposures flag of a given GC, use XSet-
GraphicsExposures.
__
|
XSetGraphicsExposures(display, gc, graphics_exposures)
      Display *display;
      GC gc;
      Bool graphics_exposures;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

graphics_exposures
	  Specifies a Boolean value that indicates whether
	  you want GraphicsExpose and NoExpose events to be
	  reported when calling XCopyArea and XCopyPlane
	  with this GC.
|__

XSetGraphicsExposures can generate BadAlloc, BadGC, and Bad-
Value errors.














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			 Chapter 8

		     Graphics Functions



Once you have established a connection to a display, you can
use the Xlib graphics functions to:

o    Clear and copy areas

o    Draw points, lines, rectangles, and arcs

o    Fill areas

o    Manipulate fonts

o    Draw text

o    Transfer images between clients and the server

If the same drawable and GC is used for each call, Xlib
batches back-to-back calls to XDrawPoint, XDrawLine,
XDrawRectangle, XFillArc, and XFillRectangle.  Note that
this reduces the total number of requests sent to the
server.

8.1.  Clearing Areas

Xlib provides functions that you can use to clear an area or
the entire window.  Because pixmaps do not have defined
backgrounds, they cannot be filled by using the functions
described in this section.  Instead, to accomplish an analo-
gous operation on a pixmap, you should use XFillRectangle,
which sets the pixmap to a known value.


To clear a rectangular area of a given window, use XClear-
Area.
















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__
|
XClearArea(display, w, x, y, width, height, exposures)
      Display *display;
      Window w;
      int x, y;
      unsigned int width, height;
      Bool exposures;


display   Specifies the connection to the X server.

w	  Specifies the window.

x
y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the window and specify the
	  upper-left corner of the rectangle.

width
height	  Specify the width and height, which are the dimen-
	  sions of the rectangle.

exposures Specifies a Boolean value that indicates if Expose
	  events are to be generated.
|__

The XClearArea function paints a rectangular area in the
specified window according to the specified dimensions with
the window's background pixel or pixmap.  The subwindow-mode
effectively is ClipByChildren.	If width is zero, it is
replaced with the current width of the window minus x.	If
height is zero, it is replaced with the current height of
the window minus y.  If the window has a defined background
tile, the rectangle clipped by any children is filled with
this tile.  If the window has background None, the contents
of the window are not changed.	In either case, if exposures
is True, one or more Expose events are generated for regions
of the rectangle that are either visible or are being
retained in a backing store.  If you specify a window whose
class is InputOnly, a BadMatch error results.

XClearArea can generate BadMatch, BadValue, and BadWindow
errors.


To clear the entire area in a given window, use XClearWin-
dow.










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__
|
XClearWindow(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window.
|__

The XClearWindow function clears the entire area in the
specified window and is equivalent to XClearArea (display,
w, 0, 0, 0, 0, False).	If the window has a defined back-
ground tile, the rectangle is tiled with a plane-mask of all
ones and GXcopy function.  If the window has background
None, the contents of the window are not changed.  If you
specify a window whose class is InputOnly, a BadMatch error
results.

XClearWindow can generate BadMatch and BadWindow errors.

8.2.  Copying Areas

Xlib provides functions that you can use to copy an area or
a bit plane.


To copy an area between drawables of the same root and
depth, use XCopyArea.



























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__
|
XCopyArea(display, src, dest, gc, src_x, src_y, width, height,	dest_x, dest_y)
      Display *display;
      Drawable src, dest;
      GC gc;
      int src_x, src_y;
      unsigned int width, height;
      int dest_x, dest_y;


display   Specifies the connection to the X server.

src
dest	  Specify the source and destination rectangles to
	  be combined.

gc	  Specifies the GC.

src_x
src_y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the source rectangle and
	  specify its upper-left corner.

width
height	  Specify the width and height, which are the dimen-
	  sions of both the source and destination rectan-
	  gles.

dest_x
dest_y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the destination rectangle
	  and specify its upper-left corner.
|__

The XCopyArea function combines the specified rectangle of
src with the specified rectangle of dest.  The drawables
must have the same root and depth, or a BadMatch error
results.

If regions of the source rectangle are obscured and have not
been retained in backing store or if regions outside the
boundaries of the source drawable are specified, those
regions are not copied.  Instead, the following occurs on
all corresponding destination regions that are either visi-
ble or are retained in backing store.  If the destination is
a window with a background other than None, corresponding
regions of the destination are tiled with that background
(with plane-mask of all ones and GXcopy function).  Regard-
less of tiling or whether the destination is a window or a
pixmap, if graphics-exposures is True, then GraphicsExpose
events for all corresponding destination regions are gener-
ated.  If graphics-exposures is True but no GraphicsExpose
events are generated, a NoExpose event is generated.  Note
that by default graphics-exposures is True in new GCs.



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This function uses these GC components: function, plane-
mask, subwindow-mode, graphics-exposures, clip-x-origin,
clip-y-origin, and clip-mask.

XCopyArea can generate BadDrawable, BadGC, and BadMatch
errors.


To copy a single bit plane of a given drawable, use XCopy-
Plane.
__
|
XCopyPlane(display, src, dest, gc, src_x, src_y, width, height, dest_x, dest_y, plane)
      Display *display;
      Drawable src, dest;
      GC gc;
      int src_x, src_y;
      unsigned int width, height;
      int dest_x, dest_y;
      unsigned long plane;


display   Specifies the connection to the X server.

src
dest	  Specify the source and destination rectangles to
	  be combined.

gc	  Specifies the GC.

src_x
src_y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the source rectangle and
	  specify its upper-left corner.

width
height	  Specify the width and height, which are the dimen-
	  sions of both the source and destination rectan-
	  gles.

dest_x
dest_y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the destination rectangle
	  and specify its upper-left corner.

plane	  Specifies the bit plane.  You must set exactly one
	  bit to 1.
|__

The XCopyPlane function uses a single bit plane of the spec-
ified source rectangle combined with the specified GC to
modify the specified rectangle of dest.  The drawables must
have the same root but need not have the same depth.  If the
drawables do not have the same root, a BadMatch error



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results.  If plane does not have exactly one bit set to 1
and the value of plane is not less than 2n, where n is the
depth of src, a BadValue error results.

Effectively, XCopyPlane forms a pixmap of the same depth as
the rectangle of dest and with a size specified by the
source region.	It uses the foreground/background pixels in
the GC (foreground everywhere the bit plane in src contains
a bit set to 1, background everywhere the bit plane in src
contains a bit set to 0) and the equivalent of a CopyArea
protocol request is performed with all the same exposure
semantics.  This can also be thought of as using the speci-
fied region of the source bit plane as a stipple with a
fill-style of FillOpaqueStippled for filling a rectangular
area of the destination.

This function uses these GC components: function, plane-
mask, foreground, background, subwindow-mode, graphics-expo-
sures, clip-x-origin, clip-y-origin, and clip-mask.

XCopyPlane can generate BadDrawable, BadGC, BadMatch, and
BadValue errors.

8.3.  Drawing Points, Lines, Rectangles, and Arcs

Xlib provides functions that you can use to draw:

o    A single point or multiple points

o    A single line or multiple lines

o    A single rectangle or multiple rectangles

o    A single arc or multiple arcs

Some of the functions described in the following sections
use these structures:

__
|
typedef struct {
     short x1, y1, x2, y2;
} XSegment;

|__












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__
|
typedef struct {
     short x, y;
} XPoint;

|__

__
|
typedef struct {
     short x, y;
     unsigned short width, height;
} XRectangle;

|__

__
|
typedef struct {
     short x, y;
     unsigned short width, height;
     short angle1, angle2;	       /* Degrees * 64 */
} XArc;

|__

All x and y members are signed integers.  The width and
height members are 16-bit unsigned integers.  You should be
careful not to generate coordinates and sizes out of the
16-bit ranges, because the protocol only has 16-bit fields
for these values.

8.3.1.	Drawing Single and Multiple Points


To draw a single point in a given drawable, use XDrawPoint.





















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__
|
XDrawPoint(display, d, gc, x, y)
      Display *display;
      Drawable d;
      GC gc;
      int x, y;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

x
y	  Specify the x and y coordinates where you want the
	  point drawn.
|__


To draw multiple points in a given drawable, use XDraw-
Points.
__
|
XDrawPoints(display, d, gc, points, npoints, mode)
      Display *display;
      Drawable d;
      GC gc;
      XPoint *points;
      int npoints;
      int mode;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

points	  Specifies an array of points.

npoints   Specifies the number of points in the array.

mode	  Specifies the coordinate mode.  You can pass
	  CoordModeOrigin or CoordModePrevious.
|__

The XDrawPoint function uses the foreground pixel and func-
tion components of the GC to draw a single point into the
specified drawable; XDrawPoints draws multiple points this
way.  CoordModeOrigin treats all coordinates as relative to
the origin, and CoordModePrevious treats all coordinates
after the first as relative to the previous point.  XDraw-
Points draws the points in the order listed in the array.



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Both functions use these GC components: function, plane-
mask, foreground, subwindow-mode, clip-x-origin, clip-y-ori-
gin, and clip-mask.

XDrawPoint can generate BadDrawable, BadGC, and BadMatch
errors.  XDrawPoints can generate BadDrawable, BadGC, Bad-
Match, and BadValue errors.

8.3.2.	Drawing Single and Multiple Lines


To draw a single line between two points in a given draw-
able, use XDrawLine.
__
|
XDrawLine(display, d, gc, x1, y1, x2, y2)
      Display *display;
      Drawable d;
      GC gc;
      int x1, y1, x2, y2;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

x1
y1
x2
y2	  Specify the points (x1, y1) and (x2, y2) to be
	  connected.
|__


To draw multiple lines in a given drawable, use XDrawLines.




















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__
|
XDrawLines(display, d, gc, points, npoints, mode)
      Display *display;
      Drawable d;
      GC gc;
      XPoint *points;
      int npoints;
      int mode;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

points	  Specifies an array of points.

npoints   Specifies the number of points in the array.

mode	  Specifies the coordinate mode.  You can pass
	  CoordModeOrigin or CoordModePrevious.
|__


To draw multiple, unconnected lines in a given drawable, use
XDrawSegments.
__
|
XDrawSegments(display, d, gc, segments, nsegments)
      Display *display;
      Drawable d;
      GC gc;
      XSegment *segments;
      int nsegments;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

segments  Specifies an array of segments.

nsegments Specifies the number of segments in the array.
|__

The XDrawLine function uses the components of the specified
GC to draw a line between the specified set of points (x1,
y1) and (x2, y2).  It does not perform joining at coincident
endpoints.  For any given line, XDrawLine does not draw a
pixel more than once.  If lines intersect, the intersecting
pixels are drawn multiple times.



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The XDrawLines function uses the components of the specified
GC to draw npoints-1 lines between each pair of points
(point[i], point[i+1]) in the array of XPoint structures.
It draws the lines in the order listed in the array.  The
lines join correctly at all intermediate points, and if the
first and last points coincide, the first and last lines
also join correctly.  For any given line, XDrawLines does
not draw a pixel more than once.  If thin (zero line-width)
lines intersect, the intersecting pixels are drawn multiple
times.	If wide lines intersect, the intersecting pixels are
drawn only once, as though the entire PolyLine protocol
request were a single, filled shape.  CoordModeOrigin treats
all coordinates as relative to the origin, and CoordModePre-
vious treats all coordinates after the first as relative to
the previous point.

The XDrawSegments function draws multiple, unconnected
lines.	For each segment, XDrawSegments draws a line between
(x1, y1) and (x2, y2).	It draws the lines in the order
listed in the array of XSegment structures and does not per-
form joining at coincident endpoints.  For any given line,
XDrawSegments does not draw a pixel more than once.  If
lines intersect, the intersecting pixels are drawn multiple
times.

All three functions use these GC components: function,
plane-mask, line-width, line-style, cap-style, fill-style,
subwindow-mode, clip-x-origin, clip-y-origin, and clip-mask.
The XDrawLines function also uses the join-style GC compo-
nent.  All three functions also use these GC mode-dependent
components: foreground, background, tile, stipple, tile-
stipple-x-origin, tile-stipple-y-origin, dash-offset, and
dash-list.

XDrawLine, XDrawLines, and XDrawSegments can generate Bad-
Drawable, BadGC, and BadMatch errors.  XDrawLines also can
generate BadValue errors.

8.3.3.	Drawing Single and Multiple Rectangles


To draw the outline of a single rectangle in a given draw-
able, use XDrawRectangle.














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__
|
XDrawRectangle(display, d, gc, x, y, width, height)
      Display *display;
      Drawable d;
      GC gc;
      int x, y;
      unsigned int width, height;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

x
y	  Specify the x and y coordinates, which specify the
	  upper-left corner of the rectangle.

width
height	  Specify the width and height, which specify the
	  dimensions of the rectangle.
|__


To draw the outline of multiple rectangles in a given draw-
able, use XDrawRectangles.
__
|
XDrawRectangles(display, d, gc, rectangles, nrectangles)
      Display *display;
      Drawable d;
      GC gc;
      XRectangle rectangles[];
      int nrectangles;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

rectangles
	  Specifies an array of rectangles.

nrectangles
	  Specifies the number of rectangles in the array.
|__

The XDrawRectangle and XDrawRectangles functions draw the
outlines of the specified rectangle or rectangles as if a
five-point PolyLine protocol request were specified for each
rectangle:



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     [x,y] [x+width,y] [x+width,y+height] [x,y+height] [x,y]

For the specified rectangle or rectangles, these functions
do not draw a pixel more than once.  XDrawRectangles draws
the rectangles in the order listed in the array.  If rectan-
gles intersect, the intersecting pixels are drawn multiple
times.

Both functions use these GC components: function, plane-
mask, line-width, line-style, cap-style, join-style, fill-
style, subwindow-mode, clip-x-origin, clip-y-origin, and
clip-mask.  They also use these GC mode-dependent compo-
nents: foreground, background, tile, stipple, tile-stipple-
x-origin, tile-stipple-y-origin, dash-offset, and dash-list.

XDrawRectangle and XDrawRectangles can generate BadDrawable,
BadGC, and BadMatch errors.

8.3.4.	Drawing Single and Multiple Arcs



To draw a single arc in a given drawable, use XDrawArc.


































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__
|
XDrawArc(display, d, gc, x, y, width, height, angle1, angle2)
      Display *display;
      Drawable d;
      GC gc;
      int x, y;
      unsigned int width, height;
      int angle1, angle2;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

x
y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the drawable and specify the
	  upper-left corner of the bounding rectangle.

width
height	  Specify the width and height, which are the major
	  and minor axes of the arc.

angle1	  Specifies the start of the arc relative to the
	  three-o'clock position from the center, in units
	  of degrees * 64.

angle2	  Specifies the path and extent of the arc relative
	  to the start of the arc, in units of degrees * 64.
|__


To draw multiple arcs in a given drawable, use XDrawArcs.






















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__
|
XDrawArcs(display, d, gc, arcs, narcs)
      Display *display;
      Drawable d;
      GC gc;
      XArc *arcs;
      int narcs;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

arcs	  Specifies an array of arcs.

narcs	  Specifies the number of arcs in the array.
|__

XDrawArc draws a single circular or elliptical arc, and
XDrawArcs draws multiple circular or elliptical arcs.  Each
arc is specified by a rectangle and two angles.  The center
of the circle or ellipse is the center of the rectangle, and
the major and minor axes are specified by the width and
height.  Positive angles indicate counterclockwise motion,
and negative angles indicate clockwise motion.	If the mag-
nitude of angle2 is greater than 360 degrees, XDrawArc or
XDrawArcs truncates it to 360 degrees.

For an arc specified as [x,y,width,height,angle1,angle2],
the origin of the major and minor axes is at
[x+_____,y+______], and the infinitely thin path describing
the entire circle or ellipse intersects the horizontal axis
at [x,y+______] and [x+width,y+______] and intersects the
vertical axis at [x+_____,y] and [x+_____,y+height].  These
coordinates can be fractional and so are not truncated to
discrete coordinates.  The path should be defined by the
ideal mathematical path.  For a wide line with line-width
lw, the bounding outlines for filling are given by the two
infinitely thin paths consisting of all points whose perpen-
dicular distance from the path of the circle/ellipse is
equal to lw/2 (which may be a fractional value).  The cap-
style and join-style are applied the same as for a line cor-
responding to the tangent of the circle/ellipse at the end-
point.

For an arc specified as [x,y,width,height,angle1,angle2],
the angles must be specified in the effectively skewed coor-
dinate system of the ellipse (for a circle, the angles and
coordinate systems are identical).  The relationship between
these angles and angles expressed in the normal coordinate
system of the screen (as measured with a protractor) is as
follows:



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     skewed-angle=atan(tan(normal-angle)*______)+adjust


The skewed-angle and normal-angle are expressed in radians
(rather than in degrees scaled by 64) in the range [0,2] and
where atan returns a value in the range [-_,_] and adjust
is:


     0	       for normal-angle in the range [0,_]
	       for normal-angle in the range [_,_]
     2	       for normal-angle in the range [_,2]


For any given arc, XDrawArc and XDrawArcs do not draw a
pixel more than once.  If two arcs join correctly and if the
line-width is greater than zero and the arcs intersect,
XDrawArc and XDrawArcs do not draw a pixel more than once.
Otherwise, the intersecting pixels of intersecting arcs are
drawn multiple times.  Specifying an arc with one endpoint
and a clockwise extent draws the same pixels as specifying
the other endpoint and an equivalent counterclockwise
extent, except as it affects joins.

If the last point in one arc coincides with the first point
in the following arc, the two arcs will join correctly.  If
the first point in the first arc coincides with the last
point in the last arc, the two arcs will join correctly.  By
specifying one axis to be zero, a horizontal or vertical
line can be drawn.  Angles are computed based solely on the
coordinate system and ignore the aspect ratio.

Both functions use these GC components: function, plane-
mask, line-width, line-style, cap-style, join-style, fill-
style, subwindow-mode, clip-x-origin, clip-y-origin, and
clip-mask.  They also use these GC mode-dependent compo-
nents: foreground, background, tile, stipple, tile-stipple-
x-origin, tile-stipple-y-origin, dash-offset, and dash-list.

XDrawArc and XDrawArcs can generate BadDrawable, BadGC, and
BadMatch errors.

8.4.  Filling Areas

Xlib provides functions that you can use to fill:

o    A single rectangle or multiple rectangles

o    A single polygon

o    A single arc or multiple arcs






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8.4.1.	Filling Single and Multiple Rectangles



To fill a single rectangular area in a given drawable, use
XFillRectangle.
__
|
XFillRectangle(display, d, gc, x, y, width, height)
      Display *display;
      Drawable d;
      GC gc;
      int x, y;
      unsigned int width, height;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

x
y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the drawable and specify the
	  upper-left corner of the rectangle.

width
height	  Specify the width and height, which are the dimen-
	  sions of the rectangle to be filled.
|__


To fill multiple rectangular areas in a given drawable, use
XFillRectangles.






















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__
|
XFillRectangles(display, d, gc, rectangles, nrectangles)
      Display *display;
      Drawable d;
      GC gc;
      XRectangle *rectangles;
      int nrectangles;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

rectangles
	  Specifies an array of rectangles.

nrectangles
	  Specifies the number of rectangles in the array.
|__

The XFillRectangle and XFillRectangles functions fill the
specified rectangle or rectangles as if a four-point
FillPolygon protocol request were specified for each rectan-
gle:


     [x,y] [x+width,y] [x+width,y+height] [x,y+height]


Each function uses the x and y coordinates, width and height
dimensions, and GC you specify.

XFillRectangles fills the rectangles in the order listed in
the array.  For any given rectangle, XFillRectangle and
XFillRectangles do not draw a pixel more than once.  If
rectangles intersect, the intersecting pixels are drawn mul-
tiple times.

Both functions use these GC components: function, plane-
mask, fill-style, subwindow-mode, clip-x-origin, clip-y-ori-
gin, and clip-mask.  They also use these GC mode-dependent
components: foreground, background, tile, stipple, tile-
stipple-x-origin, and tile-stipple-y-origin.

XFillRectangle and XFillRectangles can generate BadDrawable,
BadGC, and BadMatch errors.

8.4.2.	Filling a Single Polygon


To fill a polygon area in a given drawable, use XFillPoly-
gon.



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__
|
XFillPolygon(display, d, gc, points, npoints, shape, mode)
      Display *display;
      Drawable d;
      GC gc;
      XPoint *points;
      int npoints;
      int shape;
      int mode;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

points	  Specifies an array of points.

npoints   Specifies the number of points in the array.

shape	  Specifies a shape that helps the server to improve
	  performance.	You can pass Complex, Convex, or
	  Nonconvex.

mode	  Specifies the coordinate mode.  You can pass
	  CoordModeOrigin or CoordModePrevious.
|__

XFillPolygon fills the region closed by the specified path.
The path is closed automatically if the last point in the
list does not coincide with the first point.  XFillPolygon
does not draw a pixel of the region more than once.  Coord-
ModeOrigin treats all coordinates as relative to the origin,
and CoordModePrevious treats all coordinates after the first
as relative to the previous point.

Depending on the specified shape, the following occurs:

o    If shape is Complex, the path may self-intersect.	Note
     that contiguous coincident points in the path are not
     treated as self-intersection.

o    If shape is Convex, for every pair of points inside the
     polygon, the line segment connecting them does not
     intersect the path.  If known by the client, specifying
     Convex can improve performance.  If you specify Convex
     for a path that is not convex, the graphics results are
     undefined.

o    If shape is Nonconvex, the path does not self-inter-
     sect, but the shape is not wholly convex.	If known by
     the client, specifying Nonconvex instead of Complex may
     improve performance.  If you specify Nonconvex for a



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     self-intersecting path, the graphics results are unde-
     fined.

The fill-rule of the GC controls the filling behavior of
self-intersecting polygons.

This function uses these GC components: function, plane-
mask, fill-style, fill-rule, subwindow-mode, clip-x-origin,
clip-y-origin, and clip-mask.  It also uses these GC mode-
dependent components: foreground, background, tile, stipple,
tile-stipple-x-origin, and tile-stipple-y-origin.

XFillPolygon can generate BadDrawable, BadGC, BadMatch, and
BadValue errors.

8.4.3.	Filling Single and Multiple Arcs

To fill a single arc in a given drawable, use XFillArc.
__
|
XFillArc(display, d, gc,  x, y, width, height, angle1, angle2)
      Display *display;
      Drawable d;
      GC gc;
      int x, y;
      unsigned int width, height;
      int angle1, angle2;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

x
y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the drawable and specify the
	  upper-left corner of the bounding rectangle.

width
height	  Specify the width and height, which are the major
	  and minor axes of the arc.

angle1	  Specifies the start of the arc relative to the
	  three-o'clock position from the center, in units
	  of degrees * 64.

angle2	  Specifies the path and extent of the arc relative
	  to the start of the arc, in units of degrees * 64.
|__


To fill multiple arcs in a given drawable, use XFillArcs.



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__
|
XFillArcs(display, d, gc, arcs, narcs)
      Display *display;
      Drawable d;
      GC gc;
      XArc *arcs;
      int narcs;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

arcs	  Specifies an array of arcs.

narcs	  Specifies the number of arcs in the array.
|__

For each arc, XFillArc or XFillArcs fills the region closed
by the infinitely thin path described by the specified arc
and, depending on the arc-mode specified in the GC, one or
two line segments.  For ArcChord, the single line segment
joining the endpoints of the arc is used.  For ArcPieSlice,
the two line segments joining the endpoints of the arc with
the center point are used.  XFillArcs fills the arcs in the
order listed in the array.  For any given arc, XFillArc and
XFillArcs do not draw a pixel more than once.  If regions
intersect, the intersecting pixels are drawn multiple times.

Both functions use these GC components: function, plane-
mask, fill-style, arc-mode, subwindow-mode, clip-x-origin,
clip-y-origin, and clip-mask.  They also use these GC mode-
dependent components: foreground, background, tile, stipple,
tile-stipple-x-origin, and tile-stipple-y-origin.

XFillArc and XFillArcs can generate BadDrawable, BadGC, and
BadMatch errors.

8.5.  Font Metrics

A font is a graphical description of a set of characters
that are used to increase efficiency whenever a set of
small, similar sized patterns are repeatedly used.

This section discusses how to:

o    Load and free fonts

o    Obtain and free font names

o    Compute character string sizes




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o    Compute logical extents

o    Query character string sizes

The X server loads fonts whenever a program requests a new
font.  The server can cache fonts for quick lookup.  Fonts
are global across all screens in a server.  Several levels
are possible when dealing with fonts.  Most applications
simply use XLoadQueryFont to load a font and query the font
metrics.

Characters in fonts are regarded as masks.  Except for image
text requests, the only pixels modified are those in which
bits are set to 1 in the character.  This means that it
makes sense to draw text using stipples or tiles (for exam-
ple, many menus gray-out unusable entries).









































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__
|    The XFontStruct structure contains all of the information
for the font and consists of the font-specific information
as well as a pointer to an array of XCharStruct structures
for the characters contained in the font.  The XFontStruct,
XFontProp, and XCharStruct structures contain:


typedef struct {
     short lbearing;	      /* origin to left edge of raster */
     short rbearing;	      /* origin to right edge of raster */
     short width;	      /* advance to next char's origin */
     short ascent;	      /* baseline to top edge of raster */
     short descent;	      /* baseline to bottom edge of raster */
     unsigned short attributes;/* per char flags (not predefined) */
} XCharStruct;



typedef struct {
     Atom name;
     unsigned long card32;
} XFontProp;



typedef struct {	      /* normal 16 bit characters are two bytes */
    unsigned char byte1;
    unsigned char byte2;
} XChar2b;



typedef struct {
     XExtData *ext_data;      /* hook for extension to hang data */
     Font fid;		      /* Font id for this font */
     unsigned direction;      /* hint about the direction font is painted */
     unsigned min_char_or_byte2;/* first character */
     unsigned max_char_or_byte2;/* last character */
     unsigned min_byte1;      /* first row that exists */
     unsigned max_byte1;      /* last row that exists */
     Bool all_chars_exist;    /* flag if all characters have nonzero size */
     unsigned default_char;   /* char to print for undefined character */
     int n_properties;	      /* how many properties there are */
     XFontProp *properties;   /* pointer to array of additional properties */
     XCharStruct min_bounds;  /* minimum bounds over all existing char */
     XCharStruct max_bounds;  /* maximum bounds over all existing char */
     XCharStruct *per_char;   /* first_char to last_char information */
     int ascent;	      /* logical extent above baseline for spacing */
     int descent;	      /* logical descent below baseline for spacing */
} XFontStruct;

|__

X supports single byte/character, two bytes/character



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matrix, and 16-bit character text operations.  Note that any
of these forms can be used with a font, but a single
byte/character text request can only specify a single byte
(that is, the first row of a 2-byte font).  You should view
2-byte fonts as a two-dimensional matrix of defined charac-
ters: byte1 specifies the range of defined rows and byte2
defines the range of defined columns of the font.  Single
byte/character fonts have one row defined, and the byte2
range specified in the structure defines a range of charac-
ters.

The bounding box of a character is defined by the
XCharStruct of that character.	When characters are absent
from a font, the default_char is used.	When fonts have all
characters of the same size, only the information in the
XFontStruct min and max bounds are used.

The members of the XFontStruct have the following semantics:

o    The direction member can be either FontLeftToRight or
     FontRightToLeft.  It is just a hint as to whether most
     XCharStruct elements have a positive (FontLeftToRight)
     or a negative (FontRightToLeft) character width metric.
     The core protocol defines no support for vertical text.

o    If the min_byte1 and max_byte1 members are both zero,
     min_char_or_byte2 specifies the linear character index
     corresponding to the first element of the per_char
     array, and max_char_or_byte2 specifies the linear char-
     acter index of the last element.

     If either min_byte1 or max_byte1 are nonzero, both
     min_char_or_byte2 and max_char_or_byte2 are less than
     256, and the 2-byte character index values correspond-
     ing to the per_char array element N (counting from 0)
     are:

	  byte1 = N/D + min_byte1
	  byte2 = N\D + min_char_or_byte2

     where:

	     D = max_char_or_byte2 - min_char_or_byte2 + 1
	     / = integer division
	     \ = integer modulus

o    If the per_char pointer is NULL, all glyphs between the
     first and last character indexes inclusive have the
     same information, as given by both min_bounds and
     max_bounds.

o    If all_chars_exist is True, all characters in the
     per_char array have nonzero bounding boxes.




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o    The default_char member specifies the character that
     will be used when an undefined or nonexistent character
     is printed.  The default_char is a 16-bit character
     (not a 2-byte character).	For a font using 2-byte
     matrix format, the default_char has byte1 in the most-
     significant byte and byte2 in the least significant
     byte.  If the default_char itself specifies an unde-
     fined or nonexistent character, no printing is per-
     formed for an undefined or nonexistent character.

o    The min_bounds and max_bounds members contain the most
     extreme values of each individual XCharStruct component
     over all elements of this array (and ignore nonexistent
     characters).  The bounding box of the font (the small-
     est rectangle enclosing the shape obtained by superim-
     posing all of the characters at the same origin [x,y])
     has its upper-left coordinate at:

	       [x + min_bounds.lbearing, y - max_bounds.ascent]


     Its width is:

	       max_bounds.rbearing - min_bounds.lbearing


     Its height is:

	       max_bounds.ascent + max_bounds.descent


o    The ascent member is the logical extent of the font
     above the baseline that is used for determining line
     spacing.  Specific characters may extend beyond this.

o    The descent member is the logical extent of the font at
     or below the baseline that is used for determining line
     spacing.  Specific characters may extend beyond this.

o    If the baseline is at Y-coordinate y, the logical
     extent of the font is inclusive between the Y-coordi-
     nate values (y - font.ascent) and (y + font.descent -
     1).  Typically, the minimum interline spacing between
     rows of text is given by ascent + descent.

For a character origin at [x,y], the bounding box of a char-
acter (that is, the smallest rectangle that encloses the
character's shape) described in terms of XCharStruct compo-
nents is a rectangle with its upper-left corner at:


     [x + lbearing, y - ascent]





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Its width is:


     rbearing - lbearing


Its height is:


     ascent + descent


The origin for the next character is defined to be:


     [x + width, y]


The lbearing member defines the extent of the left edge of
the character ink from the origin.  The rbearing member
defines the extent of the right edge of the character ink
from the origin.  The ascent member defines the extent of
the top edge of the character ink from the origin.  The
descent member defines the extent of the bottom edge of the
character ink from the origin.	The width member defines the
logical width of the character.

Note that the baseline (the y position of the character ori-
gin) is logically viewed as being the scanline just below
nondescending characters.  When descent is zero, only pixels
with Y-coordinates less than y are drawn, and the origin is
logically viewed as being coincident with the left edge of a
nonkerned character.  When lbearing is zero, no pixels with
X-coordinate less than x are drawn.  Any of the XCharStruct
metric members could be negative.  If the width is negative,
the next character will be placed to the left of the current
origin.

The X protocol does not define the interpretation of the
attributes member in the XCharStruct structure.  A nonexis-
tent character is represented with all members of its
XCharStruct set to zero.

A font is not guaranteed to have any properties.  The inter-
pretation of the property value (for example, long or
unsigned long) must be derived from a priori knowledge of
the property.  A basic set of font properties is specified
in the X Consortium standard X Logical Font Description Con-
ventions.

8.5.1.	Loading and Freeing Fonts

Xlib provides functions that you can use to load fonts, get
font information, unload fonts, and free font information.



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A few font functions use a GContext resource ID or a font ID
interchangeably.


To load a given font, use XLoadFont.
__
|
Font XLoadFont(display, name)
      Display *display;
      char *name;


display   Specifies the connection to the X server.

name	  Specifies the name of the font, which is a null-
	  terminated string.
|__

The XLoadFont function loads the specified font and returns
its associated font ID.  If the font name is not in the Host
Portable Character Encoding, the result is implementation-
dependent.  Use of uppercase or lowercase does not matter.
When the characters ``?'' and ``*'' are used in a font name,
a pattern match is performed and any matching font is used.
In the pattern, the ``?'' character will match any single
character, and the ``*'' character will match any number of
characters.  A structured format for font names is specified
in the X Consortium standard X Logical Font Description Con-
ventions.  If XLoadFont was unsuccessful at loading the
specified font, a BadName error results.  Fonts are not
associated with a particular screen and can be stored as a
component of any GC.  When the font is no longer needed,
call XUnloadFont.

XLoadFont can generate BadAlloc and BadName errors.


To return information about an available font, use XQuery-
Font.
__
|
XFontStruct *XQueryFont(display, font_ID)
      Display *display;
      XID font_ID;


display   Specifies the connection to the X server.

font_ID   Specifies the font ID or the GContext ID.
|__

The XQueryFont function returns a pointer to the XFontStruct
structure, which contains information associated with the
font.  You can query a font or the font stored in a GC.  The



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font ID stored in the XFontStruct structure will be the
GContext ID, and you need to be careful when using this ID
in other functions (see XGContextFromGC).  If the font does
not exist, XQueryFont returns NULL.  To free this data, use
XFreeFontInfo.


To perform a XLoadFont and XQueryFont in a single operation,
use XLoadQueryFont.
__
|
XFontStruct *XLoadQueryFont(display, name)
      Display *display;
      char *name;


display   Specifies the connection to the X server.

name	  Specifies the name of the font, which is a null-
	  terminated string.
|__

The XLoadQueryFont function provides the most common way for
accessing a font.  XLoadQueryFont both opens (loads) the
specified font and returns a pointer to the appropriate
XFontStruct structure.	If the font name is not in the Host
Portable Character Encoding, the result is implementation-
dependent.  If the font does not exist, XLoadQueryFont
returns NULL.

XLoadQueryFont can generate a BadAlloc error.


To unload the font and free the storage used by the font
structure that was allocated by XQueryFont or XLoadQuery-
Font, use XFreeFont.
__
|
XFreeFont(display, font_struct)
      Display *display;
      XFontStruct *font_struct;


display   Specifies the connection to the X server.

font_struct
	  Specifies the storage associated with the font.
|__

The XFreeFont function deletes the association between the
font resource ID and the specified font and frees the
XFontStruct structure.	The font itself will be freed when
no other resource references it.  The data and the font
should not be referenced again.



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XFreeFont can generate a BadFont error.


To return a given font property, use XGetFontProperty.
__
|
Bool XGetFontProperty(font_struct, atom, value_return)
      XFontStruct *font_struct;
      Atom atom;
      unsigned long *value_return;


font_struct
	  Specifies the storage associated with the font.

atom	  Specifies the atom for the property name you want
	  returned.

value_return
	  Returns the value of the font property.
|__

Given the atom for that property, the XGetFontProperty func-
tion returns the value of the specified font property.
XGetFontProperty also returns False if the property was not
defined or True if it was defined.  A set of predefined
atoms exists for font properties, which can be found in
<X11/Xatom.h>.	This set contains the standard properties
associated with a font.  Although it is not guaranteed, it
is likely that the predefined font properties will be pre-
sent.


To unload a font that was loaded by XLoadFont, use XUnload-
Font.
__
|
XUnloadFont(display, font)
      Display *display;
      Font font;


display   Specifies the connection to the X server.

font	  Specifies the font.
|__

The XUnloadFont function deletes the association between the
font resource ID and the specified font.  The font itself
will be freed when no other resource references it.  The
font should not be referenced again.

XUnloadFont can generate a BadFont error.




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8.5.2.	Obtaining and Freeing Font Names and Information

You obtain font names and information by matching a wildcard
specification when querying a font type for a list of avail-
able sizes and so on.


To return a list of the available font names, use XList-
Fonts.
__
|
char **XListFonts(display, pattern, maxnames, actual_count_return)
      Display *display;
      char *pattern;
      int maxnames;
      int *actual_count_return;


display   Specifies the connection to the X server.

pattern   Specifies the null-terminated pattern string that
	  can contain wildcard characters.

maxnames  Specifies the maximum number of names to be
	  returned.

actual_count_return
	  Returns the actual number of font names.
|__

The XListFonts function returns an array of available font
names (as controlled by the font search path; see XSetFont-
Path) that match the string you passed to the pattern argu-
ment.  The pattern string can contain any characters, but
each asterisk (*) is a wildcard for any number of charac-
ters, and each question mark (?) is a wildcard for a single
character.  If the pattern string is not in the Host
Portable Character Encoding, the result is implementation-
dependent.  Use of uppercase or lowercase does not matter.
Each returned string is null-terminated.  If the data
returned by the server is in the Latin Portable Character
Encoding, then the returned strings are in the Host Portable
Character Encoding.  Otherwise, the result is implementa-
tion-dependent.  If there are no matching font names, XList-
Fonts returns NULL.  The client should call XFreeFontNames
when finished with the result to free the memory.


To free a font name array, use XFreeFontNames.








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__
|
XFreeFontNames(list)
      char *list[];


list	  Specifies the array of strings you want to free.
|__

The XFreeFontNames function frees the array and strings
returned by XListFonts or XListFontsWithInfo.


To obtain the names and information about available fonts,
use XListFontsWithInfo.
__
|
char **XListFontsWithInfo(display, pattern, maxnames, count_return, info_return)
      Display *display;
      char *pattern;
      int maxnames;
      int *count_return;
      XFontStruct **info_return;


display   Specifies the connection to the X server.

pattern   Specifies the null-terminated pattern string that
	  can contain wildcard characters.

maxnames  Specifies the maximum number of names to be
	  returned.

count_return
	  Returns the actual number of matched font names.

info_return
	  Returns the font information.
|__

The XListFontsWithInfo function returns a list of font names
that match the specified pattern and their associated font
information.  The list of names is limited to size specified
by maxnames.  The information returned for each font is
identical to what XLoadQueryFont would return except that
the per-character metrics are not returned.  The pattern
string can contain any characters, but each asterisk (*) is
a wildcard for any number of characters, and each question
mark (?) is a wildcard for a single character.	If the pat-
tern string is not in the Host Portable Character Encoding,
the result is implementation-dependent.  Use of uppercase or
lowercase does not matter.  Each returned string is null-
terminated.  If the data returned by the server is in the
Latin Portable Character Encoding, then the returned strings
are in the Host Portable Character Encoding.  Otherwise, the



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result is implementation-dependent.  If there are no match-
ing font names, XListFontsWithInfo returns NULL.

To free only the allocated name array, the client should
call XFreeFontNames.  To free both the name array and the
font information array or to free just the font information
array, the client should call XFreeFontInfo.


To free font structures and font names, use XFreeFontInfo.
__
|
XFreeFontInfo(names, free_info, actual_count)
      char **names;
      XFontStruct *free_info;
      int actual_count;


names	  Specifies the list of font names.


free_info Specifies the font information.


actual_count
	  Specifies the actual number of font names.

|__

The XFreeFontInfo function frees a font structure or an
array of font structures and optionally an array of font
names.	If NULL is passed for names, no font names are
freed.	If a font structure for an open font (returned by
XLoadQueryFont) is passed, the structure is freed, but the
font is not closed; use XUnloadFont to close the font.

8.5.3.	Computing Character String Sizes

Xlib provides functions that you can use to compute the
width, the logical extents, and the server information about
8-bit and 2-byte text strings.	The width is computed by
adding the character widths of all the characters.  It does
not matter if the font is an 8-bit or 2-byte font.  These
functions return the sum of the character metrics in pixels.


To determine the width of an 8-bit character string, use
XTextWidth.









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__
|
int XTextWidth(font_struct, string, count)
      XFontStruct *font_struct;
      char *string;
      int count;


font_struct
	  Specifies the font used for the width computation.

string	  Specifies the character string.

count	  Specifies the character count in the specified
	  string.
|__


To determine the width of a 2-byte character string, use
XTextWidth16.
__
|
int XTextWidth16(font_struct, string, count)
      XFontStruct *font_struct;
      XChar2b *string;
      int count;


font_struct
	  Specifies the font used for the width computation.

string	  Specifies the character string.

count	  Specifies the character count in the specified
	  string.
|__


8.5.4.	Computing Logical Extents

To compute the bounding box of an 8-bit character string in
a given font, use XTextExtents.
















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__
|
XTextExtents(font_struct, string, nchars, direction_return, font_ascent_return,
	      font_descent_return, overall_return)
      XFontStruct *font_struct;
      char *string;
      int nchars;
      int *direction_return;
      int *font_ascent_return, *font_descent_return;
      XCharStruct *overall_return;



font_struct
	  Specifies the XFontStruct structure.

string	  Specifies the character string.

nchars	  Specifies the number of characters in the charac-
	  ter string.

direction_return
	  Returns the value of the direction hint (FontLeft-
	  ToRight or FontRightToLeft).

font_ascent_return
	  Returns the font ascent.

font_descent_return
	  Returns the font descent.

overall_return
	  Returns the overall size in the specified
	  XCharStruct structure.
|__


To compute the bounding box of a 2-byte character string in
a given font, use XTextExtents16.



















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__
|
XTextExtents16(font_struct, string, nchars, direction_return, font_ascent_return,
		font_descent_return, overall_return)
      XFontStruct *font_struct;
      XChar2b *string;
      int nchars;
      int *direction_return;
      int *font_ascent_return, *font_descent_return;
      XCharStruct *overall_return;



font_struct
	  Specifies the XFontStruct structure.

string	  Specifies the character string.

nchars	  Specifies the number of characters in the charac-
	  ter string.

direction_return
	  Returns the value of the direction hint (FontLeft-
	  ToRight or FontRightToLeft).

font_ascent_return
	  Returns the font ascent.

font_descent_return
	  Returns the font descent.

overall_return
	  Returns the overall size in the specified
	  XCharStruct structure.
|__

The XTextExtents and XTextExtents16 functions perform the
size computation locally and, thereby, avoid the round-trip
overhead of XQueryTextExtents and XQueryTextExtents16.	Both
functions return an XCharStruct structure, whose members are
set to the values as follows.

The ascent member is set to the maximum of the ascent met-
rics of all characters in the string.  The descent member is
set to the maximum of the descent metrics.  The width member
is set to the sum of the character-width metrics of all
characters in the string.  For each character in the string,
let W be the sum of the character-width metrics of all char-
acters preceding it in the string.  Let L be the left-side-
bearing metric of the character plus W.  Let R be the right-
side-bearing metric of the character plus W.  The lbearing
member is set to the minimum L of all characters in the
string.  The rbearing member is set to the maximum R.





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For fonts defined with linear indexing rather than 2-byte
matrix indexing, each XChar2b structure is interpreted as a
16-bit number with byte1 as the most significant byte.	If
the font has no defined default character, undefined charac-
ters in the string are taken to have all zero metrics.

8.5.5.	Querying Character String Sizes

To query the server for the bounding box of an 8-bit charac-
ter string in a given font, use XQueryTextExtents.
__
|
XQueryTextExtents(display, font_ID, string, nchars, direction_return, font_ascent_return,
		    font_descent_return, overall_return)
      Display *display;
      XID font_ID;
      char *string;
      int nchars;
      int *direction_return;
      int *font_ascent_return, *font_descent_return;
      XCharStruct *overall_return;


display   Specifies the connection to the X server.

font_ID   Specifies either the font ID or the GContext ID
	  that contains the font.

string	  Specifies the character string.

nchars	  Specifies the number of characters in the charac-
	  ter string.

direction_return
	  Returns the value of the direction hint (FontLeft-
	  ToRight or FontRightToLeft).

font_ascent_return
	  Returns the font ascent.

font_descent_return
	  Returns the font descent.

overall_return
	  Returns the overall size in the specified
	  XCharStruct structure.
|__


To query the server for the bounding box of a 2-byte charac-
ter string in a given font, use XQueryTextExtents16.






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__
|
XQueryTextExtents16(display, font_ID, string, nchars, direction_return, font_ascent_return,
			font_descent_return, overall_return)
      Display *display;
      XID font_ID;
      XChar2b *string;
      int nchars;
      int *direction_return;
      int *font_ascent_return, *font_descent_return;
      XCharStruct *overall_return;


display   Specifies the connection to the X server.

font_ID   Specifies either the font ID or the GContext ID
	  that contains the font.

string	  Specifies the character string.

nchars	  Specifies the number of characters in the charac-
	  ter string.

direction_return
	  Returns the value of the direction hint (FontLeft-
	  ToRight or FontRightToLeft).

font_ascent_return
	  Returns the font ascent.

font_descent_return
	  Returns the font descent.

overall_return
	  Returns the overall size in the specified
	  XCharStruct structure.
|__

The XQueryTextExtents and XQueryTextExtents16 functions
return the bounding box of the specified 8-bit and 16-bit
character string in the specified font or the font contained
in the specified GC.  These functions query the X server
and, therefore, suffer the round-trip overhead that is
avoided by XTextExtents and XTextExtents16.  Both functions
return a XCharStruct structure, whose members are set to the
values as follows.

The ascent member is set to the maximum of the ascent met-
rics of all characters in the string.  The descent member is
set to the maximum of the descent metrics.  The width member
is set to the sum of the character-width metrics of all
characters in the string.  For each character in the string,
let W be the sum of the character-width metrics of all char-
acters preceding it in the string.  Let L be the left-side-
bearing metric of the character plus W.  Let R be the right-



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side-bearing metric of the character plus W.  The lbearing
member is set to the minimum L of all characters in the
string.  The rbearing member is set to the maximum R.

For fonts defined with linear indexing rather than 2-byte
matrix indexing, each XChar2b structure is interpreted as a
16-bit number with byte1 as the most significant byte.	If
the font has no defined default character, undefined charac-
ters in the string are taken to have all zero metrics.

Characters with all zero metrics are ignored.  If the font
has no defined default_char, the undefined characters in the
string are also ignored.

XQueryTextExtents and XQueryTextExtents16 can generate Bad-
Font and BadGC errors.

8.6.  Drawing Text

This section discusses how to draw:

o    Complex text

o    Text characters

o    Image text characters

The fundamental text functions XDrawText and XDrawText16 use
the following structures:

__
|
typedef struct {
     char *chars;	      /* pointer to string */
     int nchars;	      /* number of characters */
     int delta; 	      /* delta between strings */
     Font font; 	      /* Font to print it in, None don't change */
} XTextItem;



typedef struct {
     XChar2b *chars;	      /* pointer to two-byte characters */
     int nchars;	      /* number of characters */
     int delta; 	      /* delta between strings */
     Font font; 	      /* font to print it in, None don't change */
} XTextItem16;

|__

If the font member is not None, the font is changed before
printing and also is stored in the GC.	If an error was gen-
erated during text drawing, the previous items may have been
drawn.	The baseline of the characters are drawn starting at



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the x and y coordinates that you pass in the text drawing
functions.

For example, consider the background rectangle drawn by
XDrawImageString.  If you want the upper-left corner of the
background rectangle to be at pixel coordinate (x,y), pass
the (x,y + ascent) as the baseline origin coordinates to the
text functions.  The ascent is the font ascent, as given in
the XFontStruct structure.  If you want the lower-left cor-
ner of the background rectangle to be at pixel coordinate
(x,y), pass the (x,y - descent + 1) as the baseline origin
coordinates to the text functions.  The descent is the font
descent, as given in the XFontStruct structure.

8.6.1.	Drawing Complex Text


To draw 8-bit characters in a given drawable, use XDrawText.
__
|
XDrawText(display, d, gc, x, y, items, nitems)
      Display *display;
      Drawable d;
      GC gc;
      int x, y;
      XTextItem *items;
      int nitems;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

x
y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the specified drawable and
	  define the origin of the first character.

items	  Specifies an array of text items.

nitems	  Specifies the number of text items in the array.
|__


To draw 2-byte characters in a given drawable, use XDraw-
Text16.









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__
|
XDrawText16(display, d, gc, x, y, items, nitems)
      Display *display;
      Drawable d;
      GC gc;
      int x, y;
      XTextItem16 *items;
      int nitems;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

x
y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the specified drawable and
	  define the origin of the first character.

items	  Specifies an array of text items.

nitems	  Specifies the number of text items in the array.
|__

The XDrawText16 function is similar to XDrawText except that
it uses 2-byte or 16-bit characters.  Both functions allow
complex spacing and font shifts between counted strings.

Each text item is processed in turn.  A font member other
than None in an item causes the font to be stored in the GC
and used for subsequent text.  A text element delta speci-
fies an additional change in the position along the x axis
before the string is drawn.  The delta is always added to
the character origin and is not dependent on any character-
istics of the font.  Each character image, as defined by the
font in the GC, is treated as an additional mask for a fill
operation on the drawable.  The drawable is modified only
where the font character has a bit set to 1.  If a text item
generates a BadFont error, the previous text items may have
been drawn.

For fonts defined with linear indexing rather than 2-byte
matrix indexing, each XChar2b structure is interpreted as a
16-bit number with byte1 as the most significant byte.

Both functions use these GC components: function, plane-
mask, fill-style, font, subwindow-mode, clip-x-origin, clip-
y-origin, and clip-mask.  They also use these GC mode-depen-
dent components: foreground, background, tile, stipple,
tile-stipple-x-origin, and tile-stipple-y-origin.





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XDrawText and XDrawText16 can generate BadDrawable, BadFont,
BadGC, and BadMatch errors.

8.6.2.	Drawing Text Characters

To draw 8-bit characters in a given drawable, use XDraw-
String.
__
|
XDrawString(display, d, gc, x, y, string, length)
      Display *display;
      Drawable d;
      GC gc;
      int x, y;
      char *string;
      int length;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

x
y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the specified drawable and
	  define the origin of the first character.

string	  Specifies the character string.

length	  Specifies the number of characters in the string
	  argument.
|__


To draw 2-byte characters in a given drawable, use XDraw-
String16.



















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__
|
XDrawString16(display, d, gc, x, y, string, length)
      Display *display;
      Drawable d;
      GC gc;
      int x, y;
      XChar2b *string;
      int length;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

x
y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the specified drawable and
	  define the origin of the first character.

string	  Specifies the character string.

length	  Specifies the number of characters in the string
	  argument.
|__

Each character image, as defined by the font in the GC, is
treated as an additional mask for a fill operation on the
drawable.  The drawable is modified only where the font
character has a bit set to 1.  For fonts defined with 2-byte
matrix indexing and used with XDrawString16, each byte is
used as a byte2 with a byte1 of zero.

Both functions use these GC components: function, plane-
mask, fill-style, font, subwindow-mode, clip-x-origin, clip-
y-origin, and clip-mask.  They also use these GC mode-depen-
dent components: foreground, background, tile, stipple,
tile-stipple-x-origin, and tile-stipple-y-origin.

XDrawString and XDrawString16 can generate BadDrawable,
BadGC, and BadMatch errors.

8.6.3.	Drawing Image Text Characters

Some applications, in particular terminal emulators, need to
print image text in which both the foreground and background
bits of each character are painted.  This prevents annoying
flicker on many displays.


To draw 8-bit image text characters in a given drawable, use
XDrawImageString.




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__
|
XDrawImageString(display, d, gc, x, y, string, length)
      Display *display;
      Drawable d;
      GC gc;
      int x, y;
      char *string;
      int length;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

x
y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the specified drawable and
	  define the origin of the first character.

string	  Specifies the character string.

length	  Specifies the number of characters in the string
	  argument.
|__


To draw 2-byte image text characters in a given drawable,
use XDrawImageString16.



























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__
|
XDrawImageString16(display, d, gc, x, y, string, length)
      Display *display;
      Drawable d;
      GC gc;
      int x, y;
      XChar2b *string;
      int length;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

x
y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the specified drawable and
	  define the origin of the first character.

string	  Specifies the character string.

length	  Specifies the number of characters in the string
	  argument.
|__

The XDrawImageString16 function is similar to XDrawIm-
ageString except that it uses 2-byte or 16-bit characters.
Both functions also use both the foreground and background
pixels of the GC in the destination.

The effect is first to fill a destination rectangle with the
background pixel defined in the GC and then to paint the
text with the foreground pixel.  The upper-left corner of
the filled rectangle is at:


     [x, y - font-ascent]


The width is:


     overall-width


The height is:


     font-ascent + font-descent






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The overall-width, font-ascent, and font-descent are as
would be returned by XQueryTextExtents using gc and string.
The function and fill-style defined in the GC are ignored
for these functions.  The effective function is GXcopy, and
the effective fill-style is FillSolid.

For fonts defined with 2-byte matrix indexing and used with
XDrawImageString, each byte is used as a byte2 with a byte1
of zero.

Both functions use these GC components: plane-mask, fore-
ground, background, font, subwindow-mode, clip-x-origin,
clip-y-origin, and clip-mask.

XDrawImageString and XDrawImageString16 can generate Bad-
Drawable, BadGC, and BadMatch errors.


8.7.  Transferring Images between Client and Server

Xlib provides functions that you can use to transfer images
between a client and the server.  Because the server may
require diverse data formats, Xlib provides an image object
that fully describes the data in memory and that provides
for basic operations on that data.  You should reference the
data through the image object rather than referencing the
data directly.	However, some implementations of the Xlib
library may efficiently deal with frequently used data for-
mats by replacing functions in the procedure vector with
special case functions.  Supported operations include
destroying the image, getting a pixel, storing a pixel,
extracting a subimage of an image, and adding a constant to
an image (see section 16.8).

All the image manipulation functions discussed in this sec-
tion make use of the XImage structure, which describes an
image as it exists in the client's memory.




















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__
|
typedef struct _XImage {
     int width, height;       /* size of image */
     int xoffset;	      /* number of pixels offset in X direction */
     int format;	      /* XYBitmap, XYPixmap, ZPixmap */
     char *data;	      /* pointer to image data */
     int byte_order;	      /* data byte order, LSBFirst, MSBFirst */
     int bitmap_unit;	      /* quant. of scanline 8, 16, 32 */
     int bitmap_bit_order;    /* LSBFirst, MSBFirst */
     int bitmap_pad;	      /* 8, 16, 32 either XY or ZPixmap */
     int depth; 	      /* depth of image */
     int bytes_per_line;      /* accelerator to next scanline */
     int bits_per_pixel;      /* bits per pixel (ZPixmap) */
     unsigned long red_mask;  /* bits in z arrangement */
     unsigned long green_mask;
     unsigned long blue_mask;
     XPointer obdata;	      /* hook for the object routines to hang on */
     struct funcs {	      /* image manipulation routines */
	  struct _XImage *(*create_image)();
	  int (*destroy_image)();
	  unsigned long (*get_pixel)();
	  int (*put_pixel)();
	  struct _XImage *(*sub_image)();
	  int (*add_pixel)();
     } f;
} XImage;

|__


To initialize the image manipulation routines of an image
structure, use XInitImage.
__
|
Status XInitImage(image)
      XImage *image;


ximage	  Specifies the image.
|__

The XInitImage function initializes the internal image
manipulation routines of an image structure, based on the
values of the various structure members.  All fields other
than the manipulation routines must already be initialized.
If the bytes_per_line member is zero, XInitImage will assume
the image data is contiguous in memory and set the
bytes_per_line member to an appropriate value based on the
other members; otherwise, the value of bytes_per_line is not
changed.  All of the manipulation routines are initialized
to functions that other Xlib image manipulation functions
need to operate on the type of image specified by the rest
of the structure.




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This function must be called for any image constructed by
the client before passing it to any other Xlib function.
Image structures created or returned by Xlib do not need to
be initialized in this fashion.

This function returns a nonzero status if initialization of
the structure is successful.  It returns zero if it detected
some error or inconsistency in the structure, in which case
the image is not changed.


To combine an image with a rectangle of a drawable on the
display, use XPutImage.
__
|
XPutImage(display, d, gc, image, src_x, src_y, dest_x, dest_y, width, height)
	Display *display;
	Drawable d;
	GC gc;
	XImage *image;
	int src_x, src_y;
	int dest_x, dest_y;
	unsigned int width, height;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

image	  Specifies the image you want combined with the
	  rectangle.

src_x	  Specifies the offset in X from the left edge of
	  the image defined by the XImage structure.

src_y	  Specifies the offset in Y from the top edge of the
	  image defined by the XImage structure.

dest_x
dest_y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the drawable and are the
	  coordinates of the subimage.

width
height	  Specify the width and height of the subimage,
	  which define the dimensions of the rectangle.
|__

The XPutImage function combines an image with a rectangle of
the specified drawable.  The section of the image defined by
the src_x, src_y, width, and height arguments is drawn on
the specified part of the drawable.  If XYBitmap format is



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used, the depth of the image must be one, or a BadMatch
error results.	The foreground pixel in the GC defines the
source for the one bits in the image, and the background
pixel defines the source for the zero bits.  For XYPixmap
and ZPixmap, the depth of the image must match the depth of
the drawable, or a BadMatch error results.

If the characteristics of the image (for example, byte_order
and bitmap_unit) differ from what the server requires,
XPutImage automatically makes the appropriate conversions.

This function uses these GC components: function, plane-
mask, subwindow-mode, clip-x-origin, clip-y-origin, and
clip-mask.  It also uses these GC mode-dependent components:
foreground and background.

XPutImage can generate BadDrawable, BadGC, BadMatch, and
BadValue errors.


To return the contents of a rectangle in a given drawable on
the display, use XGetImage.  This function specifically sup-
ports rudimentary screen dumps.


































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__
|
XImage *XGetImage(display, d, x, y, width, height, plane_mask, format)
	Display *display;
	Drawable d;
	int x, y;
	unsigned int width, height;
	unsigned long plane_mask;
	int format;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

x
y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the drawable and define the
	  upper-left corner of the rectangle.

width
height	  Specify the width and height of the subimage,
	  which define the dimensions of the rectangle.

plane_mask
	  Specifies the plane mask.

format	  Specifies the format for the image.  You can pass
	  XYPixmap or ZPixmap.
|__

The XGetImage function returns a pointer to an XImage struc-
ture.  This structure provides you with the contents of the
specified rectangle of the drawable in the format you spec-
ify.  If the format argument is XYPixmap, the image contains
only the bit planes you passed to the plane_mask argument.
If the plane_mask argument only requests a subset of the
planes of the display, the depth of the returned image will
be the number of planes requested.  If the format argument
is ZPixmap, XGetImage returns as zero the bits in all planes
not specified in the plane_mask argument.  The function per-
forms no range checking on the values in plane_mask and
ignores extraneous bits.

XGetImage returns the depth of the image to the depth member
of the XImage structure.  The depth of the image is as spec-
ified when the drawable was created, except when getting a
subset of the planes in XYPixmap format, when the depth is
given by the number of bits set to 1 in plane_mask.

If the drawable is a pixmap, the given rectangle must be
wholly contained within the pixmap, or a BadMatch error
results.  If the drawable is a window, the window must be
viewable, and it must be the case that if there were no
inferiors or overlapping windows, the specified rectangle of



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the window would be fully visible on the screen and wholly
contained within the outside edges of the window, or a Bad-
Match error results.  Note that the borders of the window
can be included and read with this request.  If the window
has backing-store, the backing-store contents are returned
for regions of the window that are obscured by noninferior
windows.  If the window does not have backing-store, the
returned contents of such obscured regions are undefined.
The returned contents of visible regions of inferiors of a
different depth than the specified window's depth are also
undefined.  The pointer cursor image is not included in the
returned contents.  If a problem occurs, XGetImage returns
NULL.

XGetImage can generate BadDrawable, BadMatch, and BadValue
errors.


To copy the contents of a rectangle on the display to a
location within a preexisting image structure, use XGet-
SubImage.




































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__
|
XImage *XGetSubImage(display, d, x, y, width, height, plane_mask, format, dest_image, dest_x,
		     dest_y)
      Display *display;
      Drawable d;
      int x, y;
      unsigned int width, height;
      unsigned long plane_mask;
      int format;
      XImage *dest_image;
      int dest_x, dest_y;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

x
y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the drawable and define the
	  upper-left corner of the rectangle.

width
height	  Specify the width and height of the subimage,
	  which define the dimensions of the rectangle.

plane_mask
	  Specifies the plane mask.

format	  Specifies the format for the image.  You can pass
	  XYPixmap or ZPixmap.

dest_image
	  Specifies the destination image.

dest_x
dest_y	  Specify the x and y coordinates, which are rela-
	  tive to the origin of the destination rectangle,
	  specify its upper-left corner, and determine where
	  the subimage is placed in the destination image.
|__

The XGetSubImage function updates dest_image with the speci-
fied subimage in the same manner as XGetImage.	If the for-
mat argument is XYPixmap, the image contains only the bit
planes you passed to the plane_mask argument.  If the format
argument is ZPixmap, XGetSubImage returns as zero the bits
in all planes not specified in the plane_mask argument.  The
function performs no range checking on the values in
plane_mask and ignores extraneous bits.  As a convenience,
XGetSubImage returns a pointer to the same XImage structure
specified by dest_image.





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The depth of the destination XImage structure must be the
same as that of the drawable.  If the specified subimage
does not fit at the specified location on the destination
image, the right and bottom edges are clipped.	If the draw-
able is a pixmap, the given rectangle must be wholly con-
tained within the pixmap, or a BadMatch error results.	If
the drawable is a window, the window must be viewable, and
it must be the case that if there were no inferiors or over-
lapping windows, the specified rectangle of the window would
be fully visible on the screen and wholly contained within
the outside edges of the window, or a BadMatch error
results.  If the window has backing-store, then the backing-
store contents are returned for regions of the window that
are obscured by noninferior windows.  If the window does not
have backing-store, the returned contents of such obscured
regions are undefined.	The returned contents of visible
regions of inferiors of a different depth than the specified
window's depth are also undefined.  If a problem occurs,
XGetSubImage returns NULL.

XGetSubImage can generate BadDrawable, BadGC, BadMatch, and
BadValue errors.



































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			 Chapter 9

	    Window and Session Manager Functions



Although it is difficult to categorize functions as exclu-
sively for an application, a window manager, or a session
manager, the functions in this chapter are most often used
by window managers and session managers.  It is not expected
that these functions will be used by most application pro-
grams.	Xlib provides management functions to:

o    Change the parent of a window

o    Control the lifetime of a window

o    Manage installed colormaps

o    Set and retrieve the font search path

o    Grab the server

o    Kill a client

o    Control the screen saver

o    Control host access

9.1.  Changing the Parent of a Window

To change a window's parent to another window on the same
screen, use XReparentWindow.  There is no way to move a win-
dow between screens.





















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__
|
XReparentWindow(display, w, parent, x, y)
      Display *display;
      Window w;
      Window parent;
      int x, y;


display   Specifies the connection to the X server.

w	  Specifies the window.

parent	  Specifies the parent window.

x
y	  Specify the x and y coordinates of the position in
	  the new parent window.
|__

If the specified window is mapped, XReparentWindow automati-
cally performs an UnmapWindow request on it, removes it from
its current position in the hierarchy, and inserts it as the
child of the specified parent.	The window is placed in the
stacking order on top with respect to sibling windows.

After reparenting the specified window, XReparentWindow
causes the X server to generate a ReparentNotify event.  The
override_redirect member returned in this event is set to
the window's corresponding attribute.  Window manager
clients usually should ignore this window if this member is
set to True.  Finally, if the specified window was origi-
nally mapped, the X server automatically performs a MapWin-
dow request on it.

The X server performs normal exposure processing on formerly
obscured windows.  The X server might not generate Expose
events for regions from the initial UnmapWindow request that
are immediately obscured by the final MapWindow request.  A
BadMatch error results if:

o    The new parent window is not on the same screen as the
     old parent window.

o    The new parent window is the specified window or an
     inferior of the specified window.

o    The new parent is InputOnly, and the window is not.

o    The specified window has a ParentRelative background,
     and the new parent window is not the same depth as the
     specified window.

XReparentWindow can generate BadMatch and BadWindow errors.




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9.2.  Controlling the Lifetime of a Window

The save-set of a client is a list of other clients' windows
that, if they are inferiors of one of the client's windows
at connection close, should not be destroyed and should be
remapped if they are unmapped.	For further information
about close-connection processing, see section 2.6.  To
allow an application's window to survive when a window man-
ager that has reparented a window fails, Xlib provides the
save-set functions that you can use to control the longevity
of subwindows that are normally destroyed when the parent is
destroyed.  For example, a window manager that wants to add
decoration to a window by adding a frame might reparent an
application's window.  When the frame is destroyed, the
application's window should not be destroyed but be returned
to its previous place in the window hierarchy.

The X server automatically removes windows from the save-set
when they are destroyed.


To add or remove a window from the client's save-set, use
XChangeSaveSet.
__
|
XChangeSaveSet(display, w, change_mode)
      Display *display;
      Window w;
      int change_mode;


display   Specifies the connection to the X server.

w	  Specifies the window that you want to add to or
	  delete from the client's save-set.

change_mode
	  Specifies the mode.  You can pass SetModeInsert or
	  SetModeDelete.
|__

Depending on the specified mode, XChangeSaveSet either
inserts or deletes the specified window from the client's
save-set.  The specified window must have been created by
some other client, or a BadMatch error results.

XChangeSaveSet can generate BadMatch, BadValue, and BadWin-
dow errors.


To add a window to the client's save-set, use XAddToSaveSet.






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__
|
XAddToSaveSet(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window that you want to add to the
	  client's save-set.
|__

The XAddToSaveSet function adds the specified window to the
client's save-set.  The specified window must have been cre-
ated by some other client, or a BadMatch error results.

XAddToSaveSet can generate BadMatch and BadWindow errors.


To remove a window from the client's save-set, use XRemove-
FromSaveSet.
__
|
XRemoveFromSaveSet(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window that you want to delete from
	  the client's save-set.
|__

The XRemoveFromSaveSet function removes the specified window
from the client's save-set.  The specified window must have
been created by some other client, or a BadMatch error
results.

XRemoveFromSaveSet can generate BadMatch and BadWindow
errors.

9.3.  Managing Installed Colormaps

The X server maintains a list of installed colormaps.  Win-
dows using these colormaps are guaranteed to display with
correct colors; windows using other colormaps may or may not
display with correct colors.  Xlib provides functions that
you can use to install a colormap, uninstall a colormap, and
obtain a list of installed colormaps.

At any time, there is a subset of the installed maps that is
viewed as an ordered list and is called the required list.
The length of the required list is at most M, where M is the



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minimum number of installed colormaps specified for the
screen in the connection setup.  The required list is main-
tained as follows.  When a colormap is specified to XIn-
stallColormap, it is added to the head of the list; the list
is truncated at the tail, if necessary, to keep its length
to at most M.  When a colormap is specified to XUninstall-
Colormap and it is in the required list, it is removed from
the list.  A colormap is not added to the required list when
it is implicitly installed by the X server, and the X server
cannot implicitly uninstall a colormap that is in the
required list.


To install a colormap, use XInstallColormap.
__
|
XInstallColormap(display, colormap)
      Display *display;
      Colormap colormap;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.
|__

The XInstallColormap function installs the specified col-
ormap for its associated screen.  All windows associated
with this colormap immediately display with true colors.
You associated the windows with this colormap when you cre-
ated them by calling XCreateWindow, XCreateSimpleWindow,
XChangeWindowAttributes, or XSetWindowColormap.

If the specified colormap is not already an installed col-
ormap, the X server generates a ColormapNotify event on each
window that has that colormap.	In addition, for every other
colormap that is installed as a result of a call to XIn-
stallColormap, the X server generates a ColormapNotify event
on each window that has that colormap.

XInstallColormap can generate a BadColor error.


To uninstall a colormap, use XUninstallColormap.













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__
|
XUninstallColormap(display, colormap)
      Display *display;
      Colormap colormap;


display   Specifies the connection to the X server.

colormap  Specifies the colormap.
|__

The XUninstallColormap function removes the specified col-
ormap from the required list for its screen.  As a result,
the specified colormap might be uninstalled, and the X
server might implicitly install or uninstall additional col-
ormaps.  Which colormaps get installed or uninstalled is
server dependent except that the required list must remain
installed.

If the specified colormap becomes uninstalled, the X server
generates a ColormapNotify event on each window that has
that colormap.	In addition, for every other colormap that
is installed or uninstalled as a result of a call to XUnin-
stallColormap, the X server generates a ColormapNotify event
on each window that has that colormap.

XUninstallColormap can generate a BadColor error.


To obtain a list of the currently installed colormaps for a
given screen, use XListInstalledColormaps.
__
|
Colormap *XListInstalledColormaps(display, w, num_return)
      Display *display;
      Window w;
      int *num_return;


display   Specifies the connection to the X server.

w	  Specifies the window that determines the screen.

num_return
	  Returns the number of currently installed col-
	  ormaps.
|__

The XListInstalledColormaps function returns a list of the
currently installed colormaps for the screen of the speci-
fied window.  The order of the colormaps in the list is not
significant and is no explicit indication of the required
list.  When the allocated list is no longer needed, free it
by using XFree.



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XListInstalledColormaps can generate a BadWindow error.

9.4.  Setting and Retrieving the Font Search Path

The set of fonts available from a server depends on a font
search path.  Xlib provides functions to set and retrieve
the search path for a server.


To set the font search path, use XSetFontPath.
__
|
XSetFontPath(display, directories, ndirs)
      Display *display;
      char **directories;
      int ndirs;


display   Specifies the connection to the X server.

directories
	  Specifies the directory path used to look for a
	  font.  Setting the path to the empty list restores
	  the default path defined for the X server.

ndirs	  Specifies the number of directories in the path.
|__

The XSetFontPath function defines the directory search path
for font lookup.  There is only one search path per X
server, not one per client.  The encoding and interpretation
of the strings are implementation-dependent, but typically
they specify directories or font servers to be searched in
the order listed.  An X server is permitted to cache font
information internally; for example, it might cache an
entire font from a file and not check on subsequent opens of
that font to see if the underlying font file has changed.
However, when the font path is changed, the X server is
guaranteed to flush all cached information about fonts for
which there currently are no explicit resource IDs allo-
cated.	The meaning of an error from this request is imple-
mentation-dependent.

XSetFontPath can generate a BadValue error.


To get the current font search path, use XGetFontPath.










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__
|
char **XGetFontPath(display, npaths_return)
      Display *display;
      int *npaths_return;



display   Specifies the connection to the X server.

npaths_return
	  Returns the number of strings in the font path
	  array.
|__

The XGetFontPath function allocates and returns an array of
strings containing the search path.  The contents of these
strings are implementation-dependent and are not intended to
be interpreted by client applications.	When it is no longer
needed, the data in the font path should be freed by using
XFreeFontPath.


To free data returned by XGetFontPath, use XFreeFontPath.
__
|
XFreeFontPath(list)
      char **list;



list	  Specifies the array of strings you want to free.
|__

The XFreeFontPath function frees the data allocated by XGet-
FontPath.

9.5.  Grabbing the Server

Xlib provides functions that you can use to grab and ungrab
the server.  These functions can be used to control process-
ing of output on other connections by the window system
server.  While the server is grabbed, no processing of
requests or close downs on any other connection will occur.
A client closing its connection automatically ungrabs the
server.  Although grabbing the server is highly discouraged,
it is sometimes necessary.


To grab the server, use XGrabServer.








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__
|
XGrabServer(display)
      Display *display;


display   Specifies the connection to the X server.
|__

The XGrabServer function disables processing of requests and
close downs on all other connections than the one this
request arrived on.  You should not grab the X server any
more than is absolutely necessary.


To ungrab the server, use XUngrabServer.
__
|
XUngrabServer(display)
      Display *display;


display   Specifies the connection to the X server.
|__

The XUngrabServer function restarts processing of requests
and close downs on other connections.  You should avoid
grabbing the X server as much as possible.

9.6.  Killing Clients

Xlib provides a function to cause the connection to a client
to be closed and its resources to be destroyed.  To destroy
a client, use XKillClient.
__
|
XKillClient(display, resource)
      Display *display;
      XID resource;


display   Specifies the connection to the X server.

resource  Specifies any resource associated with the client
	  that you want to destroy or AllTemporary.
|__

The XKillClient function forces a close down of the client
that created the resource if a valid resource is specified.
If the client has already terminated in either RetainPerma-
nent or RetainTemporary mode, all of the client's resources
are destroyed.	If AllTemporary is specified, the resources
of all clients that have terminated in RetainTemporary are
destroyed (see section 2.5).  This permits implementation of
window manager facilities that aid debugging.  A client can



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set its close-down mode to RetainTemporary.  If the client
then crashes, its windows would not be destroyed.  The pro-
grammer can then inspect the application's window tree and
use the window manager to destroy the zombie windows.

XKillClient can generate a BadValue error.

9.7.  Controlling the Screen Saver

Xlib provides functions that you can use to set or reset the
mode of the screen saver, to force or activate the screen
saver, or to obtain the current screen saver values.


To set the screen saver mode, use XSetScreenSaver.
__
|
XSetScreenSaver(display, timeout, interval, prefer_blanking, allow_exposures)
      Display *display;
      int timeout, interval;
      int prefer_blanking;
      int allow_exposures;


display   Specifies the connection to the X server.

timeout   Specifies the timeout, in seconds, until the
	  screen saver turns on.

interval  Specifies the interval, in seconds, between screen
	  saver alterations.

prefer_blanking
	  Specifies how to enable screen blanking.  You can
	  pass DontPreferBlanking, PreferBlanking, or
	  DefaultBlanking.

allow_exposures
	  Specifies the screen save control values.  You can
	  pass DontAllowExposures, AllowExposures, or
	  DefaultExposures.
|__

Timeout and interval are specified in seconds.	A timeout of
0 disables the screen saver (but an activated screen saver
is not deactivated), and a timeout of -1 restores the
default.  Other negative values generate a BadValue error.
If the timeout value is nonzero, XSetScreenSaver enables the
screen saver.  An interval of 0 disables the random-pattern
motion.  If no input from devices (keyboard, mouse, and so
on) is generated for the specified number of timeout seconds
once the screen saver is enabled, the screen saver is acti-
vated.




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For each screen, if blanking is preferred and the hardware
supports video blanking, the screen simply goes blank.	Oth-
erwise, if either exposures are allowed or the screen can be
regenerated without sending Expose events to clients, the
screen is tiled with the root window background tile ran-
domly re-origined each interval seconds.  Otherwise, the
screens' state do not change, and the screen saver is not
activated.  The screen saver is deactivated, and all screen
states are restored at the next keyboard or pointer input or
at the next call to XForceScreenSaver with mode ScreenSaver-
Reset.

If the server-dependent screen saver method supports peri-
odic change, the interval argument serves as a hint about
how long the change period should be, and zero hints that no
periodic change should be made.  Examples of ways to change
the screen include scrambling the colormap periodically,
moving an icon image around the screen periodically, or
tiling the screen with the root window background tile, ran-
domly re-origined periodically.

XSetScreenSaver can generate a BadValue error.


To force the screen saver on or off, use XForceScreenSaver.
__
|
XForceScreenSaver(display, mode)
      Display *display;
      int mode;


display   Specifies the connection to the X server.

mode	  Specifies the mode that is to be applied.  You can
	  pass ScreenSaverActive or ScreenSaverReset.
|__

If the specified mode is ScreenSaverActive and the screen
saver currently is deactivated, XForceScreenSaver activates
the screen saver even if the screen saver had been disabled
with a timeout of zero.  If the specified mode is Screen-
SaverReset and the screen saver currently is enabled,
XForceScreenSaver deactivates the screen saver if it was
activated, and the activation timer is reset to its initial
state (as if device input had been received).

XForceScreenSaver can generate a BadValue error.


To activate the screen saver, use XActivateScreenSaver.






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__
|
XActivateScreenSaver(display)
      Display *display;


display   Specifies the connection to the X server.
|__


To reset the screen saver, use XResetScreenSaver.
__
|
XResetScreenSaver(display)
      Display *display;


display   Specifies the connection to the X server.
|__


To get the current screen saver values, use XGetScreenSaver.
__
|
XGetScreenSaver(display, timeout_return, interval_return, prefer_blanking_return,
		  allow_exposures_return)
      Display *display;
      int *timeout_return, *interval_return;
      int *prefer_blanking_return;
      int *allow_exposures_return;


display   Specifies the connection to the X server.

timeout_return
	  Returns the timeout, in seconds, until the screen
	  saver turns on.

interval_return
	  Returns the interval between screen saver invoca-
	  tions.

prefer_blanking_return
	  Returns the current screen blanking preference
	  (DontPreferBlanking, PreferBlanking, or Default-
	  Blanking).

allow_exposures_return
	  Returns the current screen save control value
	  (DontAllowExposures, AllowExposures, or DefaultEx-
	  posures).
|__






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9.8.  Controlling Host Access

This section discusses how to:

o    Add, get, or remove hosts from the access control list

o    Change, enable, or disable access

X does not provide any protection on a per-window basis.  If
you find out the resource ID of a resource, you can manipu-
late it.  To provide some minimal level of protection, how-
ever, connections are permitted only from machines you
trust.	This is adequate on single-user workstations but
obviously breaks down on timesharing machines.	Although
provisions exist in the X protocol for proper connection
authentication, the lack of a standard authentication server
leaves host-level access control as the only common mecha-
nism.

The initial set of hosts allowed to open connections typi-
cally consists of:

o    The host the window system is running on.

o    On POSIX-conformant systems, each host listed in the
     /etc/X?.hosts file.  The ? indicates the number of the
     display.  This file should consist of host names sepa-
     rated by newlines.  DECnet nodes must terminate in ::
     to distinguish them from Internet hosts.

If a host is not in the access control list when the access
control mechanism is enabled and if the host attempts to
establish a connection, the server refuses the connection.
To change the access list, the client must reside on the
same host as the server and/or must have been granted per-
mission in the initial authorization at connection setup.

Servers also can implement other access control policies in
addition to or in place of this host access facility.  For
further information about other access control implementa-
tions, see ``X Window System Protocol.''

9.8.1.	Adding, Getting, or Removing Hosts

Xlib provides functions that you can use to add, get, or
remove hosts from the access control list.  All the host
access control functions use the XHostAddress structure,
which contains:









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__
|
typedef struct {
     int family;	      /* for example FamilyInternet */
     int length;	      /* length of address, in bytes */
     char *address;	      /* pointer to where to find the address */
} XHostAddress;

|__

The family member specifies which protocol address family to
use (for example, TCP/IP or DECnet) and can be FamilyInter-
net, FamilyDECnet, or FamilyChaos.  The length member speci-
fies the length of the address in bytes.  The address member
specifies a pointer to the address.

For TCP/IP, the address should be in network byte order.
For the DECnet family, the server performs no automatic
swapping on the address bytes.	A Phase IV address is 2
bytes long.  The first byte contains the least significant 8
bits of the node number.  The second byte contains the most
significant 2 bits of the node number in the least signifi-
cant 2 bits of the byte and the area in the most significant
6 bits of the byte.


To add a single host, use XAddHost.
__
|
XAddHost(display, host)
      Display *display;
      XHostAddress *host;


display   Specifies the connection to the X server.

host	  Specifies the host that is to be added.
|__

The XAddHost function adds the specified host to the access
control list for that display.	The server must be on the
same host as the client issuing the command, or a BadAccess
error results.

XAddHost can generate BadAccess and BadValue errors.


To add multiple hosts at one time, use XAddHosts.










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__
|
XAddHosts(display, hosts, num_hosts)
      Display *display;
      XHostAddress *hosts;
      int num_hosts;


display   Specifies the connection to the X server.

hosts	  Specifies each host that is to be added.

num_hosts Specifies the number of hosts.
|__

The XAddHosts function adds each specified host to the
access control list for that display.  The server must be on
the same host as the client issuing the command, or a BadAc-
cess error results.

XAddHosts can generate BadAccess and BadValue errors.


To obtain a host list, use XListHosts.
__
|
XHostAddress *XListHosts(display, nhosts_return, state_return)
      Display *display;
      int *nhosts_return;
      Bool *state_return;


display   Specifies the connection to the X server.

nhosts_return
	  Returns the number of hosts currently in the
	  access control list.

state_return
	  Returns the state of the access control.
|__

The XListHosts function returns the current access control
list as well as whether the use of the list at connection
setup was enabled or disabled.	XListHosts allows a program
to find out what machines can make connections.  It also
returns a pointer to a list of host structures that were
allocated by the function.  When no longer needed, this mem-
ory should be freed by calling XFree.


To remove a single host, use XRemoveHost.






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__
|
XRemoveHost(display, host)
      Display *display;
      XHostAddress *host;


display   Specifies the connection to the X server.

host	  Specifies the host that is to be removed.
|__

The XRemoveHost function removes the specified host from the
access control list for that display.  The server must be on
the same host as the client process, or a BadAccess error
results.  If you remove your machine from the access list,
you can no longer connect to that server, and this operation
cannot be reversed unless you reset the server.

XRemoveHost can generate BadAccess and BadValue errors.


To remove multiple hosts at one time, use XRemoveHosts.
__
|
XRemoveHosts(display, hosts, num_hosts)
      Display *display;
      XHostAddress *hosts;
      int num_hosts;


display   Specifies the connection to the X server.

hosts	  Specifies each host that is to be removed.

num_hosts Specifies the number of hosts.
|__

The XRemoveHosts function removes each specified host from
the access control list for that display.  The X server must
be on the same host as the client process, or a BadAccess
error results.	If you remove your machine from the access
list, you can no longer connect to that server, and this
operation cannot be reversed unless you reset the server.

XRemoveHosts can generate BadAccess and BadValue errors.

9.8.2.	Changing, Enabling, or Disabling Access Control

Xlib provides functions that you can use to enable, disable,
or change access control.

For these functions to execute successfully, the client
application must reside on the same host as the X server
and/or have been given permission in the initial



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authorization at connection setup.


To change access control, use XSetAccessControl.
__
|
XSetAccessControl(display, mode)
      Display *display;
      int mode;


display   Specifies the connection to the X server.

mode	  Specifies the mode.  You can pass EnableAccess or
	  DisableAccess.
|__

The XSetAccessControl function either enables or disables
the use of the access control list at each connection setup.

XSetAccessControl can generate BadAccess and BadValue
errors.


To enable access control, use XEnableAccessControl.
__
|
XEnableAccessControl(display)
      Display *display;


display   Specifies the connection to the X server.
|__

The XEnableAccessControl function enables the use of the
access control list at each connection setup.

XEnableAccessControl can generate a BadAccess error.


To disable access control, use XDisableAccessControl.
__
|
XDisableAccessControl(display)
      Display *display;


display   Specifies the connection to the X server.
|__

The XDisableAccessControl function disables the use of the
access control list at each connection setup.





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XDisableAccessControl can generate a BadAccess error.
























































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			 Chapter 10

			   Events



A client application communicates with the X server through
the connection you establish with the XOpenDisplay function.
A client application sends requests to the X server over
this connection.  These requests are made by the Xlib func-
tions that are called in the client application.  Many Xlib
functions cause the X server to generate events, and the
user's typing or moving the pointer can generate events
asynchronously.  The X server returns events to the client
on the same connection.

This chapter discusses the following topics associated with
events:

o    Event types

o    Event structures

o    Event masks

o    Event processing

Functions for handling events are dealt with in the next
chapter.

10.1.  Event Types

An event is data generated asynchronously by the X server as
a result of some device activity or as side effects of a
request sent by an Xlib function.  Device-related events
propagate from the source window to ancestor windows until
some client application has selected that event type or
until the event is explicitly discarded.  The X server gen-
erally sends an event to a client application only if the
client has specifically asked to be informed of that event
type, typically by setting the event-mask attribute of the
window.  The mask can also be set when you create a window
or by changing the window's event-mask.  You can also mask
out events that would propagate to ancestor windows by
manipulating the do-not-propagate mask of the window's
attributes.  However, MappingNotify events are always sent
to all clients.

An event type describes a specific event generated by the X
server.  For each event type, a corresponding constant name
is defined in <X11/X.h>, which is used when referring to an
event type.  The following table lists the event category



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and its associated event type or types.  The processing
associated with these events is discussed in section 10.5.



-------------------------------------------------------------
Event Category		 Event Type
-------------------------------------------------------------
Keyboard events 	 KeyPress, KeyRelease
Pointer events		 ButtonPress, ButtonRelease, Motion-
			 Notify
Window crossing events	 EnterNotify, LeaveNotify
Input focus events	 FocusIn, FocusOut
Keymap state notifica-	 KeymapNotify
tion event
Exposure events 	 Expose, GraphicsExpose, NoExpose
Structure control	 CirculateRequest, ConfigureRequest,
events			 MapRequest, ResizeRequest
Window state notifica-	 CirculateNotify, ConfigureNotify,
tion events		 CreateNotify, DestroyNotify, Gravi-
			 tyNotify, MapNotify, MappingNotify,
			 ReparentNotify, UnmapNotify,
			 VisibilityNotify
Colormap state notifi-	 ColormapNotify
cation event
Client communication	 ClientMessage, PropertyNotify,
events			 SelectionClear, SelectionNotify,
			 SelectionRequest
-------------------------------------------------------------


10.2.  Event Structures

For each event type, a corresponding structure is declared
in <X11/Xlib.h>.  All the event structures have the follow-
ing common members:

__
|
typedef struct {
     int type;
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window window;
} XAnyEvent;

|__

The type member is set to the event type constant name that
uniquely identifies it.  For example, when the X server
reports a GraphicsExpose event to a client application, it
sends an XGraphicsExposeEvent structure with the type member
set to GraphicsExpose.	The display member is set to a



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pointer to the display the event was read on.  The
send_event member is set to True if the event came from a
SendEvent protocol request.  The serial member is set from
the serial number reported in the protocol but expanded from
the 16-bit least-significant bits to a full 32-bit value.
The window member is set to the window that is most useful
to toolkit dispatchers.

The X server can send events at any time in the input
stream.  Xlib stores any events received while waiting for a
reply in an event queue for later use.	Xlib also provides
functions that allow you to check events in the event queue
(see section 11.3).

In addition to the individual structures declared for each
event type, the XEvent structure is a union of the individ-
ual structures declared for each event type.  Depending on
the type, you should access members of each event by using
the XEvent union.






































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__
|
typedef union _XEvent {
     int type;		      /* must not be changed */
     XAnyEvent xany;
     XKeyEvent xkey;
     XButtonEvent xbutton;
     XMotionEvent xmotion;
     XCrossingEvent xcrossing;
     XFocusChangeEvent xfocus;
     XExposeEvent xexpose;
     XGraphicsExposeEvent xgraphicsexpose;
     XNoExposeEvent xnoexpose;
     XVisibilityEvent xvisibility;
     XCreateWindowEvent xcreatewindow;
     XDestroyWindowEvent xdestroywindow;
     XUnmapEvent xunmap;
     XMapEvent xmap;
     XMapRequestEvent xmaprequest;
     XReparentEvent xreparent;
     XConfigureEvent xconfigure;
     XGravityEvent xgravity;
     XResizeRequestEvent xresizerequest;
     XConfigureRequestEvent xconfigurerequest;
     XCirculateEvent xcirculate;
     XCirculateRequestEvent xcirculaterequest;
     XPropertyEvent xproperty;
     XSelectionClearEvent xselectionclear;
     XSelectionRequestEvent xselectionrequest;
     XSelectionEvent xselection;
     XColormapEvent xcolormap;
     XClientMessageEvent xclient;
     XMappingEvent xmapping;
     XErrorEvent xerror;
     XKeymapEvent xkeymap;
     long pad[24];
} XEvent;

|__

An XEvent structure's first entry always is the type member,
which is set to the event type.  The second member always is
the serial number of the protocol request that generated the
event.	The third member always is send_event, which is a
Bool that indicates if the event was sent by a different
client.  The fourth member always is a display, which is the
display that the event was read from.  Except for keymap
events, the fifth member always is a window, which has been
carefully selected to be useful to toolkit dispatchers.  To
avoid breaking toolkits, the order of these first five
entries is not to change.  Most events also contain a time
member, which is the time at which an event occurred.  In
addition, a pointer to the generic event must be cast before
it is used to access any other information in the structure.




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10.3.  Event Masks

Clients select event reporting of most events relative to a
window.  To do this, pass an event mask to an Xlib event-
handling function that takes an event_mask argument.  The
bits of the event mask are defined in <X11/X.h>.  Each bit
in the event mask maps to an event mask name, which
describes the event or events you want the X server to
return to a client application.

Unless the client has specifically asked for them, most
events are not reported to clients when they are generated.
Unless the client suppresses them by setting graphics-expo-
sures in the GC to False, GraphicsExpose and NoExpose are
reported by default as a result of XCopyPlane and XCopyArea.
SelectionClear, SelectionRequest, SelectionNotify, or
ClientMessage cannot be masked.  Selection-related events
are only sent to clients cooperating with selections (see
section 4.5).  When the keyboard or pointer mapping is
changed, MappingNotify is always sent to clients.

The following table lists the event mask constants you can
pass to the event_mask argument and the circumstances in
which you would want to specify the event mask:


-----------------------------------------------------------
Event Mask	       Circumstances
-----------------------------------------------------------
NoEventMask	       No events wanted
KeyPressMask	       Keyboard down events wanted
KeyReleaseMask	       Keyboard up events wanted
ButtonPressMask        Pointer button down events wanted
ButtonReleaseMask      Pointer button up events wanted
EnterWindowMask        Pointer window entry events wanted
LeaveWindowMask        Pointer window leave events wanted
PointerMotionMask      Pointer motion events wanted
PointerMotionHint-     Pointer motion hints wanted
Mask
Button1MotionMask      Pointer motion while button 1 down
Button2MotionMask      Pointer motion while button 2 down
Button3MotionMask      Pointer motion while button 3 down
Button4MotionMask      Pointer motion while button 4 down
Button5MotionMask      Pointer motion while button 5 down
ButtonMotionMask       Pointer motion while any button
		       down
KeymapStateMask        Keyboard state wanted at window
		       entry and focus in
ExposureMask	       Any exposure wanted
VisibilityChangeMask   Any change in visibility wanted
StructureNotifyMask    Any change in window structure
		       wanted
ResizeRedirectMask     Redirect resize of this window




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-----------------------------------------------------------
Event Mask	       Circumstances
-----------------------------------------------------------
SubstructureNotify-    Substructure notification wanted
Mask
SubstructureRedi-      Redirect structure requests on
rectMask	       children
FocusChangeMask        Any change in input focus wanted
PropertyChangeMask     Any change in property wanted
ColormapChangeMask     Any change in colormap wanted
OwnerGrabButtonMask    Automatic grabs should activate
		       with owner_events set to True
-----------------------------------------------------------



10.4.  Event Processing Overview

The event reported to a client application during event pro-
cessing depends on which event masks you provide as the
event-mask attribute for a window.  For some event masks,
there is a one-to-one correspondence between the event mask
constant and the event type constant.  For example, if you
pass the event mask ButtonPressMask, the X server sends back
only ButtonPress events.  Most events contain a time member,
which is the time at which an event occurred.

In other cases, one event mask constant can map to several
event type constants.  For example, if you pass the event
mask SubstructureNotifyMask, the X server can send back Cir-
culateNotify, ConfigureNotify, CreateNotify, DestroyNotify,
GravityNotify, MapNotify, ReparentNotify, or UnmapNotify
events.

In another case, two event masks can map to one event type.
For example, if you pass either PointerMotionMask or Button-
MotionMask, the X server sends back a MotionNotify event.

The following table lists the event mask, its associated
event type or types, and the structure name associated with
the event type.  Some of these structures actually are type-
defs to a generic structure that is shared between two event
types.	Note that N.A. appears in columns for which the
information is not applicable.


------------------------------------------------------------------------------------------
Event Mask		    Event Type	       Structure		Generic Structure
------------------------------------------------------------------------------------------
ButtonMotionMask	    MotionNotify       XPointerMovedEvent	XMotionEvent
Button1MotionMask
Button2MotionMask
Button3MotionMask




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------------------------------------------------------------------------------------------
Event Mask		    Event Type	       Structure		Generic Structure
------------------------------------------------------------------------------------------
Button4MotionMask
Button5MotionMask
ButtonPressMask 	    ButtonPress        XButtonPressedEvent	XButtonEvent
ButtonReleaseMask	    ButtonRelease      XButtonReleasedEvent	XButtonEvent
ColormapChangeMask	    ColormapNotify     XColormapEvent
EnterWindowMask 	    EnterNotify        XEnterWindowEvent	XCrossingEvent
LeaveWindowMask 	    LeaveNotify        XLeaveWindowEvent	XCrossingEvent
ExposureMask		    Expose	       XExposeEvent
GCGraphicsExposures in GC   GraphicsExpose     XGraphicsExposeEvent
			    NoExpose	       XNoExposeEvent
FocusChangeMask 	    FocusIn	       XFocusInEvent		XFocusChangeEvent
			    FocusOut	       XFocusOutEvent		XFocusChangeEvent
KeymapStateMask 	    KeymapNotify       XKeymapEvent
KeyPressMask		    KeyPress	       XKeyPressedEvent 	XKeyEvent
KeyReleaseMask		    KeyRelease	       XKeyReleasedEvent	XKeyEvent
OwnerGrabButtonMask	    N.A.	       N.A.
PointerMotionMask	    MotionNotify       XPointerMovedEvent	XMotionEvent
PointerMotionHintMask	    N.A.	       N.A.
PropertyChangeMask	    PropertyNotify     XPropertyEvent
ResizeRedirectMask	    ResizeRequest      XResizeRequestEvent
StructureNotifyMask	    CirculateNotify    XCirculateEvent
			    ConfigureNotify    XConfigureEvent
			    DestroyNotify      XDestroyWindowEvent
			    GravityNotify      XGravityEvent
			    MapNotify	       XMapEvent
			    ReparentNotify     XReparentEvent
			    UnmapNotify        XUnmapEvent
SubstructureNotifyMask	    CirculateNotify    XCirculateEvent
			    ConfigureNotify    XConfigureEvent
			    CreateNotify       XCreateWindowEvent
			    DestroyNotify      XDestroyWindowEvent
			    GravityNotify      XGravityEvent
			    MapNotify	       XMapEvent
			    ReparentNotify     XReparentEvent
			    UnmapNotify        XUnmapEvent
SubstructureRedirectMask    CirculateRequest   XCirculateRequestEvent
			    ConfigureRequest   XConfigureRequestEvent
			    MapRequest	       XMapRequestEvent
N.A.			    ClientMessage      XClientMessageEvent
N.A.			    MappingNotify      XMappingEvent
N.A.			    SelectionClear     XSelectionClearEvent
N.A.			    SelectionNotify    XSelectionEvent
N.A.			    SelectionRequest   XSelectionRequestEvent
VisibilityChangeMask	    VisibilityNotify   XVisibilityEvent
------------------------------------------------------------------------------------------


The sections that follow describe the processing that occurs
when you select the different event masks.  The sections are
organized according to these processing categories:




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o    Keyboard and pointer events

o    Window crossing events

o    Input focus events

o    Keymap state notification events

o    Exposure events

o    Window state notification events

o    Structure control events

o    Colormap state notification events

o    Client communication events

10.5.  Keyboard and Pointer Events

This section discusses:

o    Pointer button events

o    Keyboard and pointer events

10.5.1.  Pointer Button Events

The following describes the event processing that occurs
when a pointer button press is processed with the pointer in
some window w and when no active pointer grab is in
progress.

The X server searches the ancestors of w from the root down,
looking for a passive grab to activate.  If no matching pas-
sive grab on the button exists, the X server automatically
starts an active grab for the client receiving the event and
sets the last-pointer-grab time to the current server time.
The effect is essentially equivalent to an XGrabButton with
these client passed arguments:

------------------------------------------------------
Argument	  Value
------------------------------------------------------
w		  The event window
event_mask	  The client's selected pointer
		  events on the event window
pointer_mode	  GrabModeAsync
keyboard_mode	  GrabModeAsync
owner_events	  True, if the client has selected
		  OwnerGrabButtonMask on the event
		  window, otherwise False
confine_to	  None




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------------------------------------------------------
Argument	  Value
------------------------------------------------------
cursor		  None
------------------------------------------------------


The active grab is automatically terminated when the logical
state of the pointer has all buttons released.	Clients can
modify the active grab by calling XUngrabPointer and
XChangeActivePointerGrab.

10.5.2.  Keyboard and Pointer Events

This section discusses the processing that occurs for the
keyboard events KeyPress and KeyRelease and the pointer
events ButtonPress, ButtonRelease, and MotionNotify.  For
information about the keyboard event-handling utilities, see
chapter 11.

The X server reports KeyPress or KeyRelease events to
clients wanting information about keys that logically change
state.	Note that these events are generated for all keys,
even those mapped to modifier bits.  The X server reports
ButtonPress or ButtonRelease events to clients wanting
information about buttons that logically change state.

The X server reports MotionNotify events to clients wanting
information about when the pointer logically moves.  The X
server generates this event whenever the pointer is moved
and the pointer motion begins and ends in the window.  The
granularity of MotionNotify events is not guaranteed, but a
client that selects this event type is guaranteed to receive
at least one event when the pointer moves and then rests.

The generation of the logical changes lags the physical
changes if device event processing is frozen.

To receive KeyPress, KeyRelease, ButtonPress, and ButtonRe-
lease events, set KeyPressMask, KeyReleaseMask, ButtonPress-
Mask, and ButtonReleaseMask bits in the event-mask attribute
of the window.

To receive MotionNotify events, set one or more of the fol-
lowing event masks bits in the event-mask attribute of the
window.

o    Button1MotionMask - Button5MotionMask

     The client application receives MotionNotify events
     only when one or more of the specified buttons is
     pressed.





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o    ButtonMotionMask

     The client application receives MotionNotify events
     only when at least one button is pressed.

o    PointerMotionMask

     The client application receives MotionNotify events
     independent of the state of the pointer buttons.

o    PointerMotionHintMask

     If PointerMotionHintMask is selected in combination
     with one or more of the above masks, the X server is
     free to send only one MotionNotify event (with the
     is_hint member  of the XPointerMovedEvent structure set
     to NotifyHint) to the client for the event window,
     until either the key or button state changes, the
     pointer leaves the event window, or the client calls
     XQueryPointer or XGetMotionEvents.  The server still
     may send MotionNotify events without is_hint set to
     NotifyHint.

The source of the event is the viewable window that the
pointer is in.	The window used by the X server to report
these events depends on the window's position in the window
hierarchy and whether any intervening window prohibits the
generation of these events.  Starting with the source win-
dow, the X server searches up the window hierarchy until it
locates the first window specified by a client as having an
interest in these events.  If one of the intervening windows
has its do-not-propagate-mask set to prohibit generation of
the event type, the events of those types will be sup-
pressed.  Clients can modify the actual window used for
reporting by performing active grabs and, in the case of
keyboard events, by using the focus window.

The structures for these event types contain:



















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__
|
typedef struct {
     int type;		      /* ButtonPress or ButtonRelease */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window window;	      /* ``event'' window it is reported relative to */
     Window root;	      /* root window that the event occurred on */
     Window subwindow;	      /* child window */
     Time time; 	      /* milliseconds */
     int x, y;		      /* pointer x, y coordinates in event window */
     int x_root, y_root;      /* coordinates relative to root */
     unsigned int state;      /* key or button mask */
     unsigned int button;     /* detail */
     Bool same_screen;	      /* same screen flag */
} XButtonEvent;
typedef XButtonEvent XButtonPressedEvent;
typedef XButtonEvent XButtonReleasedEvent;



typedef struct {
     int type;		      /* KeyPress or KeyRelease */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window window;	      /* ``event'' window it is reported relative to */
     Window root;	      /* root window that the event occurred on */
     Window subwindow;	      /* child window */
     Time time; 	      /* milliseconds */
     int x, y;		      /* pointer x, y coordinates in event window */
     int x_root, y_root;      /* coordinates relative to root */
     unsigned int state;      /* key or button mask */
     unsigned int keycode;    /* detail */
     Bool same_screen;	      /* same screen flag */
} XKeyEvent;
typedef XKeyEvent XKeyPressedEvent;
typedef XKeyEvent XKeyReleasedEvent;



typedef struct {
     int type;		      /* MotionNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window window;	      /* ``event'' window reported relative to */
     Window root;	      /* root window that the event occurred on */
     Window subwindow;	      /* child window */
     Time time; 	      /* milliseconds */
     int x, y;		      /* pointer x, y coordinates in event window */
     int x_root, y_root;      /* coordinates relative to root */
     unsigned int state;      /* key or button mask */
     char is_hint;	      /* detail */



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     Bool same_screen;	      /* same screen flag */
} XMotionEvent;
typedef XMotionEvent XPointerMovedEvent;

|__

These structures have the following common members: window,
root, subwindow, time, x, y, x_root, y_root, state, and
same_screen.  The window member is set to the window on
which the event was generated and is referred to as the
event window.  As long as the conditions previously dis-
cussed are met, this is the window used by the X server to
report the event.  The root member is set to the source win-
dow's root window.  The x_root and y_root members are set to
the pointer's coordinates relative to the root window's ori-
gin at the time of the event.

The same_screen member is set to indicate whether the event
window is on the same screen as the root window and can be
either True or False.  If True, the event and root windows
are on the same screen.  If False, the event and root win-
dows are not on the same screen.

If the source window is an inferior of the event window, the
subwindow member of the structure is set to the child of the
event window that is the source window or the child of the
event window that is an ancestor of the source window.	Oth-
erwise, the X server sets the subwindow member to None.  The
time member is set to the time when the event was generated
and is expressed in milliseconds.

If the event window is on the same screen as the root win-
dow, the x and y members are set to the coordinates relative
to the event window's origin.  Otherwise, these members are
set to zero.

The state member is set to indicate the logical state of the
pointer buttons and modifier keys just prior to the event,
which is the bitwise inclusive OR of one or more of the but-
ton or modifier key masks: Button1Mask, Button2Mask, But-
ton3Mask, Button4Mask, Button5Mask, ShiftMask, LockMask,
ControlMask, Mod1Mask, Mod2Mask, Mod3Mask, Mod4Mask, and
Mod5Mask.

Each of these structures also has a member that indicates
the detail.  For the XKeyPressedEvent and XKeyReleasedEvent
structures, this member is called a keycode.  It is set to a
number that represents a physical key on the keyboard.	The
keycode is an arbitrary representation for any key on the
keyboard (see sections 12.7 and 16.1).

For the XButtonPressedEvent and XButtonReleasedEvent struc-
tures, this member is called button.  It represents the
pointer button that changed state and can be the Button1,



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Button2, Button3, Button4, or Button5 value.  For the
XPointerMovedEvent structure, this member is called is_hint.
It can be set to NotifyNormal or NotifyHint.

Some of the symbols mentioned in this section have fixed
values, as follows:

-----------------------------------------------------------
Symbol		       Value
-----------------------------------------------------------
Button1MotionMask      (1L<<8)
Button2MotionMask      (1L<<9)
Button3MotionMask      (1L<<10)
Button4MotionMask      (1L<<11)
Button5MotionMask      (1L<<12)
Button1Mask	       (1<<8)
Button2Mask	       (1<<9)
Button3Mask	       (1<<10)
Button4Mask	       (1<<11)
Button5Mask	       (1<<12)
ShiftMask	       (1<<0)
LockMask	       (1<<1)
ControlMask	       (1<<2)
Mod1Mask	       (1<<3)
Mod2Mask	       (1<<4)
Mod3Mask	       (1<<5)
Mod4Mask	       (1<<6)
Mod5Mask	       (1<<7)
Button1 	       1
Button2 	       2
Button3 	       3
Button4 	       4
Button5 	       5
-----------------------------------------------------------


10.6.  Window Entry/Exit Events

This section describes the processing that occurs for the
window crossing events EnterNotify and LeaveNotify.  If a
pointer motion or a window hierarchy change causes the
pointer to be in a different window than before, the X
server reports EnterNotify or LeaveNotify events to clients
who have selected for these events.  All EnterNotify and
LeaveNotify events caused by a hierarchy change are gener-
ated after any hierarchy event (UnmapNotify, MapNotify, Con-
figureNotify, GravityNotify, CirculateNotify) caused by that
change; however, the X protocol does not constrain the
ordering of EnterNotify and LeaveNotify events with respect
to FocusOut, VisibilityNotify, and Expose events.

This contrasts with MotionNotify events, which are also gen-
erated when the pointer moves but only when the pointer
motion begins and ends in a single window.  An EnterNotify



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or LeaveNotify event also can be generated when some client
application calls XGrabPointer and XUngrabPointer.

To receive EnterNotify or LeaveNotify events, set the Enter-
WindowMask or LeaveWindowMask bits of the event-mask
attribute of the window.

The structure for these event types contains:

__
|
typedef struct {
     int type;		      /* EnterNotify or LeaveNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window window;	      /* ``event'' window reported relative to */
     Window root;	      /* root window that the event occurred on */
     Window subwindow;	      /* child window */
     Time time; 	      /* milliseconds */
     int x, y;		      /* pointer x, y coordinates in event window */
     int x_root, y_root;      /* coordinates relative to root */
     int mode;		      /* NotifyNormal, NotifyGrab, NotifyUngrab */
     int detail;
			      /*
			      * NotifyAncestor, NotifyVirtual, NotifyInferior,
			      * NotifyNonlinear,NotifyNonlinearVirtual
			      */
     Bool same_screen;	      /* same screen flag */
     Bool focus;	      /* boolean focus */
     unsigned int state;      /* key or button mask */
} XCrossingEvent;
typedef XCrossingEvent XEnterWindowEvent;
typedef XCrossingEvent XLeaveWindowEvent;

|__

The window member is set to the window on which the Enter-
Notify or LeaveNotify event was generated and is referred to
as the event window.  This is the window used by the X
server to report the event, and is relative to the root win-
dow on which the event occurred.  The root member is set to
the root window of the screen on which the event occurred.

For a LeaveNotify event, if a child of the event window con-
tains the initial position of the pointer, the subwindow
component is set to that child.  Otherwise, the X server
sets the subwindow member to None.  For an EnterNotify
event, if a child of the event window contains the final
pointer position, the subwindow component is set to that
child or None.

The time member is set to the time when the event was gener-
ated and is expressed in milliseconds.	The x and y members



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are set to the coordinates of the pointer position in the
event window.  This position is always the pointer's final
position, not its initial position.  If the event window is
on the same screen as the root window, x and y are the
pointer coordinates relative to the event window's origin.
Otherwise, x and y are set to zero.  The x_root and y_root
members are set to the pointer's coordinates relative to the
root window's origin at the time of the event.

The same_screen member is set to indicate whether the event
window is on the same screen as the root window and can be
either True or False.  If True, the event and root windows
are on the same screen.  If False, the event and root win-
dows are not on the same screen.

The focus member is set to indicate whether the event window
is the focus window or an inferior of the focus window.  The
X server can set this member to either True or False.  If
True, the event window is the focus window or an inferior of
the focus window.  If False, the event window is not the
focus window or an inferior of the focus window.

The state member is set to indicate the state of the pointer
buttons and modifier keys just prior to the event.  The X
server can set this member to the bitwise inclusive OR of
one or more of the button or modifier key masks: But-
ton1Mask, Button2Mask, Button3Mask, Button4Mask, But-
ton5Mask, ShiftMask, LockMask, ControlMask, Mod1Mask,
Mod2Mask, Mod3Mask, Mod4Mask, Mod5Mask.

The mode member is set to indicate whether the events are
normal events, pseudo-motion events when a grab activates,
or pseudo-motion events when a grab deactivates.  The X
server can set this member to NotifyNormal, NotifyGrab, or
NotifyUngrab.

The detail member is set to indicate the notify detail and
can be NotifyAncestor, NotifyVirtual, NotifyInferior, Noti-
fyNonlinear, or NotifyNonlinearVirtual.

10.6.1.  Normal Entry/Exit Events

EnterNotify and LeaveNotify events are generated when the
pointer moves from one window to another window.  Normal
events are identified by XEnterWindowEvent or XLeaveWindow-
Event structures whose mode member is set to NotifyNormal.

o    When the pointer moves from window A to window B and A
     is an inferior of B, the X server does the following:

     -	  It generates a LeaveNotify event on window A, with
	  the detail member of the XLeaveWindowEvent struc-
	  ture set to NotifyAncestor.




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     -	  It generates a LeaveNotify event on each window
	  between window A and window B, exclusive, with the
	  detail member of each XLeaveWindowEvent structure
	  set to NotifyVirtual.

     -	  It generates an EnterNotify event on window B,
	  with the detail member of the XEnterWindowEvent
	  structure set to NotifyInferior.

o    When the pointer moves from window A to window B and B
     is an inferior of A, the X server does the following:

     -	  It generates a LeaveNotify event on window A, with
	  the detail member of the XLeaveWindowEvent struc-
	  ture set to NotifyInferior.

     -	  It generates an EnterNotify event on each window
	  between window A and window B, exclusive, with the
	  detail member of each XEnterWindowEvent structure
	  set to NotifyVirtual.

     -	  It generates an EnterNotify event on window B,
	  with the detail member of the XEnterWindowEvent
	  structure set to NotifyAncestor.

o    When the pointer moves from window A to window B and
     window C is their least common ancestor, the X server
     does the following:

     -	  It generates a LeaveNotify event on window A, with
	  the detail member of the XLeaveWindowEvent struc-
	  ture set to NotifyNonlinear.

     -	  It generates a LeaveNotify event on each window
	  between window A and window C, exclusive, with the
	  detail member of each XLeaveWindowEvent structure
	  set to NotifyNonlinearVirtual.

     -	  It generates an EnterNotify event on each window
	  between window C and window B, exclusive, with the
	  detail member of each XEnterWindowEvent structure
	  set to NotifyNonlinearVirtual.

     -	  It generates an EnterNotify event on window B,
	  with the detail member of the XEnterWindowEvent
	  structure set to NotifyNonlinear.

o    When the pointer moves from window A to window B on
     different screens, the X server does the following:

     -	  It generates a LeaveNotify event on window A, with
	  the detail member of the XLeaveWindowEvent struc-
	  ture set to NotifyNonlinear.




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     -	  If window A is not a root window, it generates a
	  LeaveNotify event on each window above window A up
	  to and including its root, with the detail member
	  of each XLeaveWindowEvent structure set to Noti-
	  fyNonlinearVirtual.

     -	  If window B is not a root window, it generates an
	  EnterNotify event on each window from window B's
	  root down to but not including window B, with the
	  detail member of each XEnterWindowEvent structure
	  set to NotifyNonlinearVirtual.

     -	  It generates an EnterNotify event on window B,
	  with the detail member of the XEnterWindowEvent
	  structure set to NotifyNonlinear.

10.6.2.  Grab and Ungrab Entry/Exit Events

Pseudo-motion mode EnterNotify and LeaveNotify events are
generated when a pointer grab activates or deactivates.
Events in which the pointer grab activates are identified by
XEnterWindowEvent or XLeaveWindowEvent structures whose mode
member is set to NotifyGrab.  Events in which the pointer
grab deactivates are identified by XEnterWindowEvent or
XLeaveWindowEvent structures whose mode member is set to
NotifyUngrab (see XGrabPointer).

o    When a pointer grab activates after any initial warp
     into a confine_to window and before generating any
     actual ButtonPress event that activates the grab, G is
     the grab_window for the grab, and P is the window the
     pointer is in, the X server does the following:

     -	  It generates EnterNotify and LeaveNotify events
	  (see section 10.6.1) with the mode members of the
	  XEnterWindowEvent and XLeaveWindowEvent structures
	  set to NotifyGrab.  These events are generated as
	  if the pointer were to suddenly warp from its cur-
	  rent position in P to some position in G.  How-
	  ever, the pointer does not warp, and the X server
	  uses the pointer position as both the initial and
	  final positions for the events.

o    When a pointer grab deactivates after generating any
     actual ButtonRelease event that deactivates the grab, G
     is the grab_window for the grab, and P is the window
     the pointer is in, the X server does the following:

     -	  It generates EnterNotify and LeaveNotify events
	  (see section 10.6.1) with the mode members of the
	  XEnterWindowEvent and XLeaveWindowEvent structures
	  set to NotifyUngrab.	These events are generated
	  as if the pointer were to suddenly warp from some
	  position in G to its current position in P.



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	  However, the pointer does not warp, and the X
	  server uses the current pointer position as both
	  the initial and final positions for the events.

10.7.  Input Focus Events

This section describes the processing that occurs for the
input focus events FocusIn and FocusOut.  The X server can
report FocusIn or FocusOut events to clients wanting infor-
mation about when the input focus changes.  The keyboard is
always attached to some window (typically, the root window
or a top-level window), which is called the focus window.
The focus window and the position of the pointer determine
the window that receives keyboard input.  Clients may need
to know when the input focus changes to control highlighting
of areas on the screen.

To receive FocusIn or FocusOut events, set the FocusChange-
Mask bit in the event-mask attribute of the window.

The structure for these event types contains:

__
|
typedef struct {
     int type;		      /* FocusIn or FocusOut */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window window;	      /* window of event */
     int mode;		      /* NotifyNormal, NotifyGrab, NotifyUngrab */
     int detail;
			      /*
			      * NotifyAncestor, NotifyVirtual, NotifyInferior,
			      * NotifyNonlinear,NotifyNonlinearVirtual, NotifyPointer,
			      * NotifyPointerRoot, NotifyDetailNone
			      */
} XFocusChangeEvent;
typedef XFocusChangeEvent XFocusInEvent;
typedef XFocusChangeEvent XFocusOutEvent;

|__

The window member is set to the window on which the FocusIn
or FocusOut event was generated.  This is the window used by
the X server to report the event.  The mode member is set to
indicate whether the focus events are normal focus events,
focus events while grabbed, focus events when a grab acti-
vates, or focus events when a grab deactivates.  The X
server can set the mode member to NotifyNormal, NotifyWhile-
Grabbed, NotifyGrab, or NotifyUngrab.

All FocusOut events caused by a window unmap are generated
after any UnmapNotify event; however, the X protocol does



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not constrain the ordering of FocusOut events with respect
to generated EnterNotify, LeaveNotify, VisibilityNotify, and
Expose events.

Depending on the event mode, the detail member is set to
indicate the notify detail and can be NotifyAncestor, Noti-
fyVirtual, NotifyInferior, NotifyNonlinear, NotifyNonlin-
earVirtual, NotifyPointer, NotifyPointerRoot, or NotifyDe-
tailNone.

10.7.1.  Normal Focus Events and Focus Events While Grabbed

Normal focus events are identified by XFocusInEvent or XFo-
cusOutEvent structures whose mode member is set to Noti-
fyNormal.  Focus events while grabbed are identified by XFo-
cusInEvent or XFocusOutEvent structures whose mode member is
set to NotifyWhileGrabbed.  The X server processes normal
focus and focus events while grabbed according to the fol-
lowing:

o    When the focus moves from window A to window B, A is an
     inferior of B, and the pointer is in window P, the X
     server does the following:

     -	  It generates a FocusOut event on window A, with
	  the detail member of the XFocusOutEvent structure
	  set to NotifyAncestor.

     -	  It generates a FocusOut event on each window
	  between window A and window B, exclusive, with the
	  detail member of each XFocusOutEvent structure set
	  to NotifyVirtual.

     -	  It generates a FocusIn event on window B, with the
	  detail member of the XFocusOutEvent structure set
	  to NotifyInferior.

     -	  If window P is an inferior of window B but window
	  P is not window A or an inferior or ancestor of
	  window A, it generates a FocusIn event on each
	  window below window B, down to and including win-
	  dow P, with the detail member of each XFocusIn-
	  Event structure set to NotifyPointer.

o    When the focus moves from window A to window B, B is an
     inferior of A, and the pointer is in window P, the X
     server does the following:

     -	  If window P is an inferior of window A but P is
	  not an inferior of window B or an ancestor of B,
	  it generates a FocusOut event on each window from
	  window P up to but not including window A, with
	  the detail member of each XFocusOutEvent structure
	  set to NotifyPointer.



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     -	  It generates a FocusOut event on window A, with
	  the detail member of the XFocusOutEvent structure
	  set to NotifyInferior.

     -	  It generates a FocusIn event on each window
	  between window A and window B, exclusive, with the
	  detail member of each XFocusInEvent structure set
	  to NotifyVirtual.

     -	  It generates a FocusIn event on window B, with the
	  detail member of the XFocusInEvent structure set
	  to NotifyAncestor.

o    When the focus moves from window A to window B, window
     C is their least common ancestor, and the pointer is in
     window P, the X server does the following:

     -	  If window P is an inferior of window A, it gener-
	  ates a FocusOut event on each window from window P
	  up to but not including window A, with the detail
	  member of the XFocusOutEvent structure set to
	  NotifyPointer.

     -	  It generates a FocusOut event on window A, with
	  the detail member of the XFocusOutEvent structure
	  set to NotifyNonlinear.

     -	  It generates a FocusOut event on each window
	  between window A and window C, exclusive, with the
	  detail member of each XFocusOutEvent structure set
	  to NotifyNonlinearVirtual.

     -	  It generates a FocusIn event on each window
	  between C and B, exclusive, with the detail member
	  of each XFocusInEvent structure set to NotifyNon-
	  linearVirtual.

     -	  It generates a FocusIn event on window B, with the
	  detail member of the XFocusInEvent structure set
	  to NotifyNonlinear.

     -	  If window P is an inferior of window B, it gener-
	  ates a FocusIn event on each window below window B
	  down to and including window P, with the detail
	  member of the XFocusInEvent structure set to Noti-
	  fyPointer.

o    When the focus moves from window A to window B on dif-
     ferent screens and the pointer is in window P, the X
     server does the following:

     -	  If window P is an inferior of window A, it gener-
	  ates a FocusOut event on each window from window P
	  up to but not including window A, with the detail



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	  member of each XFocusOutEvent structure set to
	  NotifyPointer.

     -	  It generates a FocusOut event on window A, with
	  the detail member of the XFocusOutEvent structure
	  set to NotifyNonlinear.

     -	  If window A is not a root window, it generates a
	  FocusOut event on each window above window A up to
	  and including its root, with the detail member of
	  each XFocusOutEvent structure set to NotifyNonlin-
	  earVirtual.

     -	  If window B is not a root window, it generates a
	  FocusIn event on each window from window B's root
	  down to but not including window B, with the
	  detail member of each XFocusInEvent structure set
	  to NotifyNonlinearVirtual.

     -	  It generates a FocusIn event on window B, with the
	  detail member of each XFocusInEvent structure set
	  to NotifyNonlinear.

     -	  If window P is an inferior of window B, it gener-
	  ates a FocusIn event on each window below window B
	  down to and including window P, with the detail
	  member of each XFocusInEvent structure set to
	  NotifyPointer.

o    When the focus moves from window A to PointerRoot
     (events sent to the window under the pointer) or None
     (discard), and the pointer is in window P, the X server
     does the following:

     -	  If window P is an inferior of window A, it gener-
	  ates a FocusOut event on each window from window P
	  up to but not including window A, with the detail
	  member of each XFocusOutEvent structure set to
	  NotifyPointer.

     -	  It generates a FocusOut event on window A, with
	  the detail member of the XFocusOutEvent structure
	  set to NotifyNonlinear.

     -	  If window A is not a root window, it generates a
	  FocusOut event on each window above window A up to
	  and including its root, with the detail member of
	  each XFocusOutEvent structure set to NotifyNonlin-
	  earVirtual.

     -	  It generates a FocusIn event on the root window of
	  all screens, with the detail member of each XFo-
	  cusInEvent structure set to NotifyPointerRoot (or
	  NotifyDetailNone).



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     -	  If the new focus is PointerRoot, it generates a
	  FocusIn event on each window from window P's root
	  down to and including window P, with the detail
	  member of each XFocusInEvent structure set to
	  NotifyPointer.

o    When the focus moves from PointerRoot (events sent to
     the window under the pointer) or None to window A, and
     the pointer is in window P, the X server does the fol-
     lowing:

     -	  If the old focus is PointerRoot, it generates a
	  FocusOut event on each window from window P up to
	  and including window P's root, with the detail
	  member of each XFocusOutEvent structure set to
	  NotifyPointer.

     -	  It generates a FocusOut event on all root windows,
	  with the detail member of each XFocusOutEvent
	  structure set to NotifyPointerRoot (or NotifyDe-
	  tailNone).

     -	  If window A is not a root window, it generates a
	  FocusIn event on each window from window A's root
	  down to but not including window A, with the
	  detail member of each XFocusInEvent structure set
	  to NotifyNonlinearVirtual.

     -	  It generates a FocusIn event on window A, with the
	  detail member of the XFocusInEvent structure set
	  to NotifyNonlinear.

     -	  If window P is an inferior of window A, it gener-
	  ates a FocusIn event on each window below window A
	  down to and including window P, with the detail
	  member of each XFocusInEvent structure set to
	  NotifyPointer.

o    When the focus moves from PointerRoot (events sent to
     the window under the pointer) to None (or vice versa),
     and the pointer is in window P, the X server does the
     following:

     -	  If the old focus is PointerRoot, it generates a
	  FocusOut event on each window from window P up to
	  and including window P's root, with the detail
	  member of each XFocusOutEvent structure set to
	  NotifyPointer.

     -	  It generates a FocusOut event on all root windows,
	  with the detail member of each XFocusOutEvent
	  structure set to either NotifyPointerRoot or Noti-
	  fyDetailNone.




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     -	  It generates a FocusIn event on all root windows,
	  with the detail member of each XFocusInEvent
	  structure set to NotifyDetailNone or NotifyPoint-
	  erRoot.

     -	  If the new focus is PointerRoot, it generates a
	  FocusIn event on each window from window P's root
	  down to and including window P, with the detail
	  member of each XFocusInEvent structure set to
	  NotifyPointer.

10.7.2.  Focus Events Generated by Grabs

Focus events in which the keyboard grab activates are iden-
tified by XFocusInEvent or XFocusOutEvent structures whose
mode member is set to NotifyGrab.  Focus events in which the
keyboard grab deactivates are identified by XFocusInEvent or
XFocusOutEvent structures whose mode member is set to Noti-
fyUngrab (see XGrabKeyboard).

o    When a keyboard grab activates before generating any
     actual KeyPress event that activates the grab, G is the
     grab_window, and F is the current focus, the X server
     does the following:

     -	  It generates FocusIn and FocusOut events, with the
	  mode members of the XFocusInEvent and XFocu-
	  sOutEvent structures set to NotifyGrab.  These
	  events are generated as if the focus were to
	  change from F to G.

o    When a keyboard grab deactivates after generating any
     actual KeyRelease event that deactivates the grab, G is
     the grab_window, and F is the current focus, the X
     server does the following:

     -	  It generates FocusIn and FocusOut events, with the
	  mode members of the XFocusInEvent and XFocu-
	  sOutEvent structures set to NotifyUngrab.  These
	  events are generated as if the focus were to
	  change from G to F.

10.8.  Key Map State Notification Events

The X server can report KeymapNotify events to clients that
want information about changes in their keyboard state.

To receive KeymapNotify events, set the KeymapStateMask bit
in the event-mask attribute of the window.  The X server
generates this event immediately after every EnterNotify and
FocusIn event.

The structure for this event type contains:




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__
|
/* generated on EnterWindow and FocusIn when KeymapState selected */
typedef struct {
     int type;		      /* KeymapNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window window;
     char key_vector[32];
} XKeymapEvent;

|__

The window member is not used but is present to aid some
toolkits.  The key_vector member is set to the bit vector of
the keyboard.  Each bit set to 1 indicates that the corre-
sponding key is currently pressed.  The vector is repre-
sented as 32 bytes.  Byte N (from 0) contains the bits for
keys 8N to 8N + 7 with the least significant bit in the byte
representing key 8N.

10.9.  Exposure Events

The X protocol does not guarantee to preserve the contents
of window regions when the windows are obscured or reconfig-
ured.  Some implementations may preserve the contents of
windows.  Other implementations are free to destroy the con-
tents of windows when exposed.	X expects client applica-
tions to assume the responsibility for restoring the con-
tents of an exposed window region.  (An exposed window
region describes a formerly obscured window whose region
becomes visible.)  Therefore, the X server sends Expose
events describing the window and the region of the window
that has been exposed.	A naive client application usually
redraws the entire window.  A more sophisticated client
application redraws only the exposed region.

10.9.1.  Expose Events

The X server can report Expose events to clients wanting
information about when the contents of window regions have
been lost.  The circumstances in which the X server gener-
ates Expose events are not as definite as those for other
events.  However, the X server never generates Expose events
on windows whose class you specified as InputOnly.  The X
server can generate Expose events when no valid contents are
available for regions of a window and either the regions are
visible, the regions are viewable and the server is (perhaps
newly) maintaining backing store on the window, or the win-
dow is not viewable but the server is (perhaps newly) honor-
ing the window's backing-store attribute of Always or When-
Mapped.  The regions decompose into an (arbitrary) set of
rectangles, and an Expose event is generated for each rect-
angle.	For any given window, the X server guarantees to



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report contiguously all of the regions exposed by some
action that causes Expose events, such as raising a window.

To receive Expose events, set the ExposureMask bit in the
event-mask attribute of the window.

The structure for this event type contains:

__
|
typedef struct {
     int type;		      /* Expose */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window window;
     int x, y;
     int width, height;
     int count; 	      /* if nonzero, at least this many more */
} XExposeEvent;

|__

The window member is set to the exposed (damaged) window.
The x and y members are set to the coordinates relative to
the window's origin and indicate the upper-left corner of
the rectangle.	The width and height members are set to the
size (extent) of the rectangle.  The count member is set to
the number of Expose events that are to follow.  If count is
zero, no more Expose events follow for this window.  How-
ever, if count is nonzero, at least that number of Expose
events (and possibly more) follow for this window.  Simple
applications that do not want to optimize redisplay by dis-
tinguishing between subareas of its window can just ignore
all Expose events with nonzero counts and perform full
redisplays on events with zero counts.

10.9.2.  GraphicsExpose and NoExpose Events

The X server can report GraphicsExpose events to clients
wanting information about when a destination region could
not be computed during certain graphics requests: XCopyArea
or XCopyPlane.	The X server generates this event whenever a
destination region could not be computed because of an
obscured or out-of-bounds source region.  In addition, the X
server guarantees to report contiguously all of the regions
exposed by some graphics request (for example, copying an
area of a drawable to a destination drawable).

The X server generates a NoExpose event whenever a graphics
request that might produce a GraphicsExpose event does not
produce any.  In other words, the client is really asking
for a GraphicsExpose event but instead receives a NoExpose
event.



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To receive GraphicsExpose or NoExpose events, you must first
set the graphics-exposure attribute of the graphics context
to True.  You also can set the graphics-expose attribute
when creating a graphics context using XCreateGC or by call-
ing XSetGraphicsExposures.

The structures for these event types contain:

__
|
typedef struct {
     int type;		      /* GraphicsExpose */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Drawable drawable;
     int x, y;
     int width, height;
     int count; 	      /* if nonzero, at least this many more */
     int major_code;	      /* core is CopyArea or CopyPlane */
     int minor_code;	      /* not defined in the core */
} XGraphicsExposeEvent;



typedef struct {
     int type;		      /* NoExpose */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Drawable drawable;
     int major_code;	      /* core is CopyArea or CopyPlane */
     int minor_code;	      /* not defined in the core */
} XNoExposeEvent;

|__

Both structures have these common members: drawable,
major_code, and minor_code.  The drawable member is set to
the drawable of the destination region on which the graphics
request was to be performed.  The major_code member is set
to the graphics request initiated by the client and can be
either X_CopyArea or X_CopyPlane.  If it is X_CopyArea, a
call to XCopyArea initiated the request.  If it is X_Copy-
Plane, a call to XCopyPlane initiated the request.  These
constants are defined in <X11/Xproto.h>.  The minor_code
member, like the major_code member, indicates which graphics
request was initiated by the client.  However, the
minor_code member is not defined by the core X protocol and
will be zero in these cases, although it may be used by an
extension.

The XGraphicsExposeEvent structure has these additional mem-
bers: x, y, width, height, and count.  The x and y members



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are set to the coordinates relative to the drawable's origin
and indicate the upper-left corner of the rectangle.  The
width and height members are set to the size (extent) of the
rectangle.  The count member is set to the number of Graph-
icsExpose events to follow.  If count is zero, no more
GraphicsExpose events follow for this window.  However, if
count is nonzero, at least that number of GraphicsExpose
events (and possibly more) are to follow for this window.

10.10.	Window State Change Events

The following sections discuss:

o    CirculateNotify events

o    ConfigureNotify events

o    CreateNotify events

o    DestroyNotify events

o    GravityNotify events

o    MapNotify events

o    MappingNotify events

o    ReparentNotify events

o    UnmapNotify events

o    VisibilityNotify events

10.10.1.  CirculateNotify Events

The X server can report CirculateNotify events to clients
wanting information about when a window changes its position
in the stack.  The X server generates this event type when-
ever a window is actually restacked as a result of a client
application calling XCirculateSubwindows, XCirculateSubwin-
dowsUp, or XCirculateSubwindowsDown.

To receive CirculateNotify events, set the StructureNotify-
Mask bit in the event-mask attribute of the window or the
SubstructureNotifyMask bit in the event-mask attribute of
the parent window (in which case, circulating any child gen-
erates an event).

The structure for this event type contains:








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__
|
typedef struct {
     int type;		      /* CirculateNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window event;
     Window window;
     int place; 	      /* PlaceOnTop, PlaceOnBottom */
} XCirculateEvent;

|__

The event member is set either to the restacked window or to
its parent, depending on whether StructureNotify or Sub-
structureNotify was selected.  The window member is set to
the window that was restacked.	The place member is set to
the window's position after the restack occurs and is either
PlaceOnTop or PlaceOnBottom.  If it is PlaceOnTop, the win-
dow is now on top of all siblings.  If it is PlaceOnBottom,
the window is now below all siblings.

10.10.2.  ConfigureNotify Events

The X server can report ConfigureNotify events to clients
wanting information about actual changes to a window's
state, such as size, position, border, and stacking order.
The X server generates this event type whenever one of the
following configure window requests made by a client appli-
cation actually completes:

o    A window's size, position, border, and/or stacking
     order is reconfigured by calling XConfigureWindow.

o    The window's position in the stacking order is changed
     by calling XLowerWindow, XRaiseWindow, or XRestackWin-
     dows.

o    A window is moved by calling XMoveWindow.

o    A window's size is changed by calling XResizeWindow.

o    A window's size and location is changed by calling
     XMoveResizeWindow.

o    A window is mapped and its position in the stacking
     order is changed by calling XMapRaised.

o    A window's border width is changed by calling XSetWin-
     dowBorderWidth.

To receive ConfigureNotify events, set the StructureNotify-
Mask bit in the event-mask attribute of the window or the
SubstructureNotifyMask bit in the event-mask attribute of



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the parent window (in which case, configuring any child gen-
erates an event).

The structure for this event type contains:

__
|
typedef struct {
     int type;		      /* ConfigureNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window event;
     Window window;
     int x, y;
     int width, height;
     int border_width;
     Window above;
     Bool override_redirect;
} XConfigureEvent;

|__

The event member is set either to the reconfigured window or
to its parent, depending on whether StructureNotify or Sub-
structureNotify was selected.  The window member is set to
the window whose size, position, border, and/or stacking
order was changed.

The x and y members are set to the coordinates relative to
the parent window's origin and indicate the position of the
upper-left outside corner of the window.  The width and
height members are set to the inside size of the window, not
including the border.  The border_width member is set to the
width of the window's border, in pixels.

The above member is set to the sibling window and is used
for stacking operations.  If the X server sets this member
to None, the window whose state was changed is on the bottom
of the stack with respect to sibling windows.  However, if
this member is set to a sibling window, the window whose
state was changed is placed on top of this sibling window.

The override_redirect member is set to the override-redirect
attribute of the window.  Window manager clients normally
should ignore this window if the override_redirect member is
True.

10.10.3.  CreateNotify Events

The X server can report CreateNotify events to clients want-
ing information about creation of windows.  The X server
generates this event whenever a client application creates a
window by calling XCreateWindow or XCreateSimpleWindow.



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To receive CreateNotify events, set the SubstructureNotify-
Mask bit in the event-mask attribute of the window.  Creat-
ing any children then generates an event.

The structure for the event type contains:

__
|
typedef struct {
     int type;		      /* CreateNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window parent;	      /* parent of the window */
     Window window;	      /* window id of window created */
     int x, y;		      /* window location */
     int width, height;       /* size of window */
     int border_width;	      /* border width */
     Bool override_redirect;  /* creation should be overridden */
} XCreateWindowEvent;

|__

The parent member is set to the created window's parent.
The window member specifies the created window.  The x and y
members are set to the created window's coordinates relative
to the parent window's origin and indicate the position of
the upper-left outside corner of the created window.  The
width and height members are set to the inside size of the
created window (not including the border) and are always
nonzero.  The border_width member is set to the width of the
created window's border, in pixels.  The override_redirect
member is set to the override-redirect attribute of the win-
dow.  Window manager clients normally should ignore this
window if the override_redirect member is True.

10.10.4.  DestroyNotify Events

The X server can report DestroyNotify events to clients
wanting information about which windows are destroyed.	The
X server generates this event whenever a client application
destroys a window by calling XDestroyWindow or XDestroySub-
windows.

The ordering of the DestroyNotify events is such that for
any given window, DestroyNotify is generated on all inferi-
ors of the window before being generated on the window
itself.  The X protocol does not constrain the ordering
among siblings and across subhierarchies.

To receive DestroyNotify events, set the StructureNotifyMask
bit in the event-mask attribute of the window or the Sub-
structureNotifyMask bit in the event-mask attribute of the
parent window (in which case, destroying any child generates



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an event).

The structure for this event type contains:

__
|
typedef struct {
     int type;		      /* DestroyNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window event;
     Window window;
} XDestroyWindowEvent;

|__

The event member is set either to the destroyed window or to
its parent, depending on whether StructureNotify or Sub-
structureNotify was selected.  The window member is set to
the window that is destroyed.

10.10.5.  GravityNotify Events

The X server can report GravityNotify events to clients
wanting information about when a window is moved because of
a change in the size of its parent.  The X server generates
this event whenever a client application actually moves a
child window as a result of resizing its parent by calling
XConfigureWindow, XMoveResizeWindow, or XResizeWindow.

To receive GravityNotify events, set the StructureNotifyMask
bit in the event-mask attribute of the window or the Sub-
structureNotifyMask bit in the event-mask attribute of the
parent window (in which case, any child that is moved
because its parent has been resized generates an event).

The structure for this event type contains:

__
|
typedef struct {
     int type;		      /* GravityNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window event;
     Window window;
     int x, y;
} XGravityEvent;

|__

The event member is set either to the window that was moved



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or to its parent, depending on whether StructureNotify or
SubstructureNotify was selected.  The window member is set
to the child window that was moved.  The x and y members are
set to the coordinates relative to the new parent window's
origin and indicate the position of the upper-left outside
corner of the window.

10.10.6.  MapNotify Events

The X server can report MapNotify events to clients wanting
information about which windows are mapped.  The X server
generates this event type whenever a client application
changes the window's state from unmapped to mapped by call-
ing XMapWindow, XMapRaised, XMapSubwindows, XReparentWindow,
or as a result of save-set processing.

To receive MapNotify events, set the StructureNotifyMask bit
in the event-mask attribute of the window or the Substruc-
tureNotifyMask bit in the event-mask attribute of the parent
window (in which case, mapping any child generates an
event).

The structure for this event type contains:

__
|
typedef struct {
     int type;		      /* MapNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window event;
     Window window;
     Bool override_redirect;  /* boolean, is override set... */
} XMapEvent;

|__

The event member is set either to the window that was mapped
or to its parent, depending on whether StructureNotify or
SubstructureNotify was selected.  The window member is set
to the window that was mapped.	The override_redirect member
is set to the override-redirect attribute of the window.
Window manager clients normally should ignore this window if
the override-redirect attribute is True, because these
events usually are generated from pop-ups, which override
structure control.

10.10.7.  MappingNotify Events

The X server reports MappingNotify events to all clients.
There is no mechanism to express disinterest in this event.
The X server generates this event type whenever a client
application successfully calls:



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o    XSetModifierMapping to indicate which KeyCodes are to
     be used as modifiers

o    XChangeKeyboardMapping to change the keyboard mapping

o    XSetPointerMapping to set the pointer mapping

The structure for this event type contains:

__
|
typedef struct {
     int type;		      /* MappingNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window window;	      /* unused */
     int request;	      /* one of MappingModifier, MappingKeyboard,
				 MappingPointer */
     int first_keycode;       /* first keycode */
     int count; 	      /* defines range of change w. first_keycode*/
} XMappingEvent;

|__

The request member is set to indicate the kind of mapping
change that occurred and can be MappingModifier, MappingKey-
board, or MappingPointer.  If it is MappingModifier, the
modifier mapping was changed.  If it is MappingKeyboard, the
keyboard mapping was changed.  If it is MappingPointer, the
pointer button mapping was changed.  The first_keycode and
count members are set only if the request member was set to
MappingKeyboard.  The number in first_keycode represents the
first number in the range of the altered mapping, and count
represents the number of keycodes altered.

To update the client application's knowledge of the key-
board, you should call XRefreshKeyboardMapping.

10.10.8.  ReparentNotify Events

The X server can report ReparentNotify events to clients
wanting information about changing a window's parent.  The X
server generates this event whenever a client application
calls XReparentWindow and the window is actually reparented.

To receive ReparentNotify events, set the StructureNotify-
Mask bit in the event-mask attribute of the window or the
SubstructureNotifyMask bit in the event-mask attribute of
either the old or the new parent window (in which case,
reparenting any child generates an event).

The structure for this event type contains:




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__
|
typedef struct {
     int type;		      /* ReparentNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window event;
     Window window;
     Window parent;
     int x, y;
     Bool override_redirect;
} XReparentEvent;

|__

The event member is set either to the reparented window or
to the old or the new parent, depending on whether Struc-
tureNotify or SubstructureNotify was selected.	The window
member is set to the window that was reparented.  The parent
member is set to the new parent window.  The x and y members
are set to the reparented window's coordinates relative to
the new parent window's origin and define the upper-left
outer corner of the reparented window.	The override_redi-
rect member is set to the override-redirect attribute of the
window specified by the window member.	Window manager
clients normally should ignore this window if the over-
ride_redirect member is True.

10.10.9.  UnmapNotify Events

The X server can report UnmapNotify events to clients want-
ing information about which windows are unmapped.  The X
server generates this event type whenever a client applica-
tion changes the window's state from mapped to unmapped.

To receive UnmapNotify events, set the StructureNotifyMask
bit in the event-mask attribute of the window or the Sub-
structureNotifyMask bit in the event-mask attribute of the
parent window (in which case, unmapping any child window
generates an event).

The structure for this event type contains:















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__
|
typedef struct {
     int type;		      /* UnmapNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window event;
     Window window;
     Bool from_configure;
} XUnmapEvent;

|__

The event member is set either to the unmapped window or to
its parent, depending on whether StructureNotify or Sub-
structureNotify was selected.  This is the window used by
the X server to report the event.  The window member is set
to the window that was unmapped.  The from_configure member
is set to True if the event was generated as a result of a
resizing of the window's parent when the window itself had a
win_gravity of UnmapGravity.

10.10.10.  VisibilityNotify Events

The X server can report VisibilityNotify events to clients
wanting any change in the visibility of the specified win-
dow.  A region of a window is visible if someone looking at
the screen can actually see it.  The X server generates this
event whenever the visibility changes state.  However, this
event is never generated for windows whose class is Inpu-
tOnly.

All VisibilityNotify events caused by a hierarchy change are
generated after any hierarchy event (UnmapNotify, MapNotify,
ConfigureNotify, GravityNotify, CirculateNotify) caused by
that change.  Any VisibilityNotify event on a given window
is generated before any Expose events on that window, but it
is not required that all VisibilityNotify events on all win-
dows be generated before all Expose events on all windows.
The X protocol does not constrain the ordering of Visibili-
tyNotify events with respect to FocusOut, EnterNotify, and
LeaveNotify events.

To receive VisibilityNotify events, set the Visibility-
ChangeMask bit in the event-mask attribute of the window.

The structure for this event type contains:










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__
|
typedef struct {
     int type;		      /* VisibilityNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window window;
     int state;
} XVisibilityEvent;

|__

The window member is set to the window whose visibility
state changes.	The state member is set to the state of the
window's visibility and can be VisibilityUnobscured, Visi-
bilityPartiallyObscured, or VisibilityFullyObscured.  The X
server ignores all of a window's subwindows when determining
the visibility state of the window and processes Visibili-
tyNotify events according to the following:

o    When the window changes state from partially obscured,
     fully obscured, or not viewable to viewable and com-
     pletely unobscured, the X server generates the event
     with the state member of the XVisibilityEvent structure
     set to VisibilityUnobscured.

o    When the window changes state from viewable and com-
     pletely unobscured or not viewable to viewable and par-
     tially obscured, the X server generates the event with
     the state member of the XVisibilityEvent structure set
     to VisibilityPartiallyObscured.

o    When the window changes state from viewable and com-
     pletely unobscured, viewable and partially obscured, or
     not viewable to viewable and fully obscured, the X
     server generates the event with the state member of the
     XVisibilityEvent structure set to VisibilityFullyOb-
     scured.

10.11.	Structure Control Events

This section discusses:

o    CirculateRequest events

o    ConfigureRequest events

o    MapRequest events

o    ResizeRequest events







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10.11.1.  CirculateRequest Events

The X server can report CirculateRequest events to clients
wanting information about when another client initiates a
circulate window request on a specified window.  The X
server generates this event type whenever a client initiates
a circulate window request on a window and a subwindow actu-
ally needs to be restacked.  The client initiates a circu-
late window request on the window by calling XCirculateSub-
windows, XCirculateSubwindowsUp, or XCirculateSubwindows-
Down.

To receive CirculateRequest events, set the Substructur-
eRedirectMask in the event-mask attribute of the window.
Then, in the future, the circulate window request for the
specified window is not executed, and thus, any subwindow's
position in the stack is not changed.  For example, suppose
a client application calls XCirculateSubwindowsUp to raise a
subwindow to the top of the stack.  If you had selected Sub-
structureRedirectMask on the window, the X server reports to
you a CirculateRequest event and does not raise the subwin-
dow to the top of the stack.

The structure for this event type contains:

__
|
typedef struct {
     int type;		      /* CirculateRequest */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window parent;
     Window window;
     int place; 	      /* PlaceOnTop, PlaceOnBottom */
} XCirculateRequestEvent;

|__

The parent member is set to the parent window.	The window
member is set to the subwindow to be restacked.  The place
member is set to what the new position in the stacking order
should be and is either PlaceOnTop or PlaceOnBottom.  If it
is PlaceOnTop, the subwindow should be on top of all sib-
lings.	If it is PlaceOnBottom, the subwindow should be
below all siblings.

10.11.2.  ConfigureRequest Events

The X server can report ConfigureRequest events to clients
wanting information about when a different client initiates
a configure window request on any child of a specified win-
dow.  The configure window request attempts to reconfigure a
window's size, position, border, and stacking order.  The X



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server generates this event whenever a different client ini-
tiates a configure window request on a window by calling
XConfigureWindow, XLowerWindow, XRaiseWindow, XMapRaised,
XMoveResizeWindow, XMoveWindow, XResizeWindow, XRestackWin-
dows, or XSetWindowBorderWidth.

To receive ConfigureRequest events, set the Substructur-
eRedirectMask bit in the event-mask attribute of the window.
ConfigureRequest events are generated when a ConfigureWindow
protocol request is issued on a child window by another
client.  For example, suppose a client application calls
XLowerWindow to lower a window.  If you had selected Sub-
structureRedirectMask on the parent window and if the over-
ride-redirect attribute of the window is set to False, the X
server reports a ConfigureRequest event to you and does not
lower the specified window.

The structure for this event type contains:

__
|
typedef struct {
     int type;		      /* ConfigureRequest */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window parent;
     Window window;
     int x, y;
     int width, height;
     int border_width;
     Window above;
     int detail;	      /* Above, Below, TopIf, BottomIf, Opposite */
     unsigned long value_mask;
} XConfigureRequestEvent;

|__

The parent member is set to the parent window.	The window
member is set to the window whose size, position, border
width, and/or stacking order is to be reconfigured.  The
value_mask member indicates which components were specified
in the ConfigureWindow protocol request.  The corresponding
values are reported as given in the request.  The remaining
values are filled in from the current geometry of the win-
dow, except in the case of above (sibling) and detail
(stack-mode), which are reported as None and Above, respec-
tively, if they are not given in the request.

10.11.3.  MapRequest Events

The X server can report MapRequest events to clients wanting
information about a different client's desire to map win-
dows.  A window is considered mapped when a map window



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request completes.  The X server generates this event when-
ever a different client initiates a map window request on an
unmapped window whose override_redirect member is set to
False.	Clients initiate map window requests by calling
XMapWindow, XMapRaised, or XMapSubwindows.

To receive MapRequest events, set the SubstructureRedirect-
Mask bit in the event-mask attribute of the window.  This
means another client's attempts to map a child window by
calling one of the map window request functions is inter-
cepted, and you are sent a MapRequest instead.	For example,
suppose a client application calls XMapWindow to map a win-
dow.  If you (usually a window manager) had selected Sub-
structureRedirectMask on the parent window and if the over-
ride-redirect attribute of the window is set to False, the X
server reports a MapRequest event to you and does not map
the specified window.  Thus, this event gives your window
manager client the ability to control the placement of sub-
windows.

The structure for this event type contains:

__
|
typedef struct {
     int type;		      /* MapRequest */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window parent;
     Window window;
} XMapRequestEvent;

|__

The parent member is set to the parent window.	The window
member is set to the window to be mapped.

10.11.4.  ResizeRequest Events

The X server can report ResizeRequest events to clients
wanting information about another client's attempts to
change the size of a window.  The X server generates this
event whenever some other client attempts to change the size
of the specified window by calling XConfigureWindow, XRe-
sizeWindow, or XMoveResizeWindow.

To receive ResizeRequest events, set the ResizeRedirect bit
in the event-mask attribute of the window.  Any attempts to
change the size by other clients are then redirected.

The structure for this event type contains:





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__
|
typedef struct {
     int type;		      /* ResizeRequest */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window window;
     int width, height;
} XResizeRequestEvent;

|__

The window member is set to the window whose size another
client attempted to change.  The width and height members
are set to the inside size of the window, excluding the bor-
der.

10.12.	Colormap State Change Events

The X server can report ColormapNotify events to clients
wanting information about when the colormap changes and when
a colormap is installed or uninstalled.  The X server gener-
ates this event type whenever a client application:

o    Changes the colormap member of the XSetWindowAttributes
     structure by calling XChangeWindowAttributes, XFreeCol-
     ormap, or XSetWindowColormap

o    Installs or uninstalls the colormap by calling XIn-
     stallColormap or XUninstallColormap

To receive ColormapNotify events, set the ColormapChangeMask
bit in the event-mask attribute of the window.

The structure for this event type contains:

__
|
typedef struct {
     int type;		      /* ColormapNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window window;
     Colormap colormap;       /* colormap or None */
     Bool new;
     int state; 	      /* ColormapInstalled, ColormapUninstalled */
} XColormapEvent;

|__

The window member is set to the window whose associated col-
ormap is changed, installed, or uninstalled.  For a colormap
that is changed, installed, or uninstalled, the colormap



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member is set to the colormap associated with the window.
For a colormap that is changed by a call to XFreeColormap,
the colormap member is set to None.  The new member is set
to indicate whether the colormap for the specified window
was changed or installed or uninstalled and can be True or
False.	If it is True, the colormap was changed.  If it is
False, the colormap was installed or uninstalled.  The state
member is always set to indicate whether the colormap is
installed or uninstalled and can be ColormapInstalled or
ColormapUninstalled.

10.13.	Client Communication Events

This section discusses:

o    ClientMessage events

o    PropertyNotify events

o    SelectionClear events

o    SelectionNotify events

o    SelectionRequest events

10.13.1.  ClientMessage Events

The X server generates ClientMessage events only when a
client calls the function XSendEvent.

The structure for this event type contains:

__
|
typedef struct {
     int type;		      /* ClientMessage */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window window;
     Atom message_type;
     int format;
     union {
	  char b[20];
	  short s[10];
	  long l[5];
	     } data;
} XClientMessageEvent;

|__

The message_type member is set to an atom that indicates how
the data should be interpreted by the receiving client.  The
format member is set to 8, 16, or 32 and specifies whether



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the data should be viewed as a list of bytes, shorts, or
longs.	The data member is a union that contains the members
b, s, and l.  The b, s, and l members represent data of
twenty 8-bit values, ten 16-bit values, and five 32-bit val-
ues.  Particular message types might not make use of all
these values.  The X server places no interpretation on the
values in the window, message_type, or data members.

10.13.2.  PropertyNotify Events

The X server can report PropertyNotify events to clients
wanting information about property changes for a specified
window.

To receive PropertyNotify events, set the PropertyChangeMask
bit in the event-mask attribute of the window.

The structure for this event type contains:

__
|
typedef struct {
     int type;		      /* PropertyNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window window;
     Atom atom;
     Time time;
     int state; 	      /* PropertyNewValue or PropertyDelete */
} XPropertyEvent;

|__

The window member is set to the window whose associated
property was changed.  The atom member is set to the prop-
erty's atom and indicates which property was changed or
desired.  The time member is set to the server time when the
property was changed.  The state member is set to indicate
whether the property was changed to a new value or deleted
and can be PropertyNewValue or PropertyDelete.	The state
member is set to PropertyNewValue when a property of the
window is changed using XChangeProperty or XRotateWindow-
Properties (even when adding zero-length data using XChange-
Property) and when replacing all or part of a property with
identical data using XChangeProperty or XRotateWindowProper-
ties.  The state member is set to PropertyDelete when a
property of the window is deleted using XDeleteProperty or,
if the delete argument is True, XGetWindowProperty.

10.13.3.  SelectionClear Events

The X server reports SelectionClear events to the client
losing ownership of a selection.  The X server generates



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this event type when another client asserts ownership of the
selection by calling XSetSelectionOwner.

The structure for this event type contains:

__
|
typedef struct {
     int type;		      /* SelectionClear */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window window;
     Atom selection;
     Time time;
} XSelectionClearEvent;

|__

The selection member is set to the selection atom.  The time
member is set to the last change time recorded for the
selection.  The window member is the window that was speci-
fied by the current owner (the owner losing the selection)
in its XSetSelectionOwner call.

10.13.4.  SelectionRequest Events

The X server reports SelectionRequest events to the owner of
a selection.  The X server generates this event whenever a
client requests a selection conversion by calling XConvertS-
election for the owned selection.

The structure for this event type contains:

__
|
typedef struct {
     int type;		      /* SelectionRequest */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window owner;
     Window requestor;
     Atom selection;
     Atom target;
     Atom property;
     Time time;
} XSelectionRequestEvent;

|__

The owner member is set to the window that was specified by
the current owner in its XSetSelectionOwner call.  The
requestor member is set to the window requesting the



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selection.  The selection member is set to the atom that
names the selection.  For example, PRIMARY is used to indi-
cate the primary selection.  The target member is set to the
atom that indicates the type the selection is desired in.
The property member can be a property name or None.  The
time member is set to the timestamp or CurrentTime value
from the ConvertSelection request.

The owner should convert the selection based on the speci-
fied target type and send a SelectionNotify event back to
the requestor.	A complete specification for using selec-
tions is given in the X Consortium standard Inter-Client
Communication Conventions Manual.

10.13.5.  SelectionNotify Events

This event is generated by the X server in response to a
ConvertSelection protocol request when there is no owner for
the selection.	When there is an owner, it should be gener-
ated by the owner of the selection by using XSendEvent.  The
owner of a selection should send this event to a requestor
when a selection has been converted and stored as a property
or when a selection conversion could not be performed (which
is indicated by setting the property member to None).

If None is specified as the property in the ConvertSelection
protocol request, the owner should choose a property name,
store the result as that property on the requestor window,
and then send a SelectionNotify giving that actual property
name.

The structure for this event type contains:

__
|
typedef struct {
     int type;		      /* SelectionNotify */
     unsigned long serial;    /* # of last request processed by server */
     Bool send_event;	      /* true if this came from a SendEvent request */
     Display *display;	      /* Display the event was read from */
     Window requestor;
     Atom selection;
     Atom target;
     Atom property;	      /* atom or None */
     Time time;
} XSelectionEvent;

|__

The requestor member is set to the window associated with
the requestor of the selection.  The selection member is set
to the atom that indicates the selection.  For example, PRI-
MARY is used for the primary selection.  The target member
is set to the atom that indicates the converted type.  For



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example, PIXMAP is used for a pixmap.  The property member
is set to the atom that indicates which property the result
was stored on.	If the conversion failed, the property mem-
ber is set to None.  The time member is set to the time the
conversion took place and can be a timestamp or CurrentTime.




















































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			 Chapter 11

		  Event Handling Functions



This chapter discusses the Xlib functions you can use to:

o    Select events

o    Handle the output buffer and the event queue

o    Select events from the event queue

o    Send and get events

o    Handle protocol errors

			      Note

	  Some toolkits use their own event-handling
	  functions and do not allow you to interchange
	  these event-handling functions with those in
	  Xlib.  For further information, see the docu-
	  mentation supplied with the toolkit.


Most applications simply are event loops: they wait for an
event, decide what to do with it, execute some amount of
code that results in changes to the display, and then wait
for the next event.

11.1.  Selecting Events

There are two ways to select the events you want reported to
your client application.  One way is to set the event_mask
member of the XSetWindowAttributes structure when you call
XCreateWindow and XChangeWindowAttributes.  Another way is
to use XSelectInput.
















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__
|
XSelectInput(display, w, event_mask)
      Display *display;
      Window w;
      long event_mask;


display   Specifies the connection to the X server.

w	  Specifies the window whose events you are inter-
	  ested in.

event_mask
	  Specifies the event mask.
|__

The XSelectInput function requests that the X server report
the events associated with the specified event mask.  Ini-
tially, X will not report any of these events.	Events are
reported relative to a window.	If a window is not inter-
ested in a device event, it usually propagates to the clos-
est ancestor that is interested, unless the do_not_propagate
mask prohibits it.

Setting the event-mask attribute of a window overrides any
previous call for the same window but not for other clients.
Multiple clients can select for the same events on the same
window with the following restrictions:

o    Multiple clients can select events on the same window
     because their event masks are disjoint.  When the X
     server generates an event, it reports it to all inter-
     ested clients.

o    Only one client at a time can select CirculateRequest,
     ConfigureRequest, or MapRequest events, which are asso-
     ciated with the event mask SubstructureRedirectMask.

o    Only one client at a time can select a ResizeRequest
     event, which is associated with the event mask Resiz-
     eRedirectMask.

o    Only one client at a time can select a ButtonPress
     event, which is associated with the event mask Button-
     PressMask.

The server reports the event to all interested clients.

XSelectInput can generate a BadWindow error.

11.2.  Handling the Output Buffer

The output buffer is an area used by Xlib to store requests.
The functions described in this section flush the output



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buffer if the function would block or not return an event.
That is, all requests residing in the output buffer that
have not yet been sent are transmitted to the X server.
These functions differ in the additional tasks they might
perform.


To flush the output buffer, use XFlush.
__
|
XFlush(display)
      Display *display;


display   Specifies the connection to the X server.
|__

The XFlush function flushes the output buffer.	Most client
applications need not use this function because the output
buffer is automatically flushed as needed by calls to XPend-
ing, XNextEvent, and XWindowEvent.  Events generated by the
server may be enqueued into the library's event queue.


To flush the output buffer and then wait until all requests
have been processed, use XSync.
__
|
XSync(display, discard)
      Display *display;
      Bool discard;


display   Specifies the connection to the X server.

discard   Specifies a Boolean value that indicates whether
	  XSync discards all events on the event queue.
|__

The XSync function flushes the output buffer and then waits
until all requests have been received and processed by the X
server.  Any errors generated must be handled by the error
handler.  For each protocol error received by Xlib, XSync
calls the client application's error handling routine (see
section 11.8.2).  Any events generated by the server are
enqueued into the library's event queue.

Finally, if you passed False, XSync does not discard the
events in the queue.  If you passed True, XSync discards all
events in the queue, including those events that were on the
queue before XSync was called.	Client applications seldom
need to call XSync.





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11.3.  Event Queue Management

Xlib maintains an event queue.	However, the operating sys-
tem also may be buffering data in its network connection
that is not yet read into the event queue.


To check the number of events in the event queue, use
XEventsQueued.
__
|
int XEventsQueued(display, mode)
     Display *display;
     int mode;


display   Specifies the connection to the X server.

mode	  Specifies the mode.  You can pass QueuedAlready,
	  QueuedAfterFlush, or QueuedAfterReading.
|__

If mode is QueuedAlready, XEventsQueued returns the number
of events already in the event queue (and never performs a
system call).  If mode is QueuedAfterFlush, XEventsQueued
returns the number of events already in the queue if the
number is nonzero.  If there are no events in the queue,
XEventsQueued flushes the output buffer, attempts to read
more events out of the application's connection, and returns
the number read.  If mode is QueuedAfterReading,
XEventsQueued returns the number of events already in the
queue if the number is nonzero.  If there are no events in
the queue, XEventsQueued attempts to read more events out of
the application's connection without flushing the output
buffer and returns the number read.

XEventsQueued always returns immediately without I/O if
there are events already in the queue.	XEventsQueued with
mode QueuedAfterFlush is identical in behavior to XPending.
XEventsQueued with mode QueuedAlready is identical to the
XQLength function.


To return the number of events that are pending, use XPend-
ing.












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__
|
int XPending(display)
      Display *display;


display   Specifies the connection to the X server.
|__

The XPending function returns the number of events that have
been received from the X server but have not been removed
from the event queue.  XPending is identical to
XEventsQueued with the mode QueuedAfterFlush specified.

11.4.  Manipulating the Event Queue

Xlib provides functions that let you manipulate the event
queue.	This section discusses how to:

o    Obtain events, in order, and remove them from the queue

o    Peek at events in the queue without removing them

o    Obtain events that match the event mask or the arbi-
     trary predicate procedures that you provide

11.4.1.  Returning the Next Event

To get the next event and remove it from the queue, use
XNextEvent.
__
|
XNextEvent(display, event_return)
      Display *display;
      XEvent *event_return;


display   Specifies the connection to the X server.

event_return
	  Returns the next event in the queue.
|__

The XNextEvent function copies the first event from the
event queue into the specified XEvent structure and then
removes it from the queue.  If the event queue is empty,
XNextEvent flushes the output buffer and blocks until an
event is received.


To peek at the event queue, use XPeekEvent.







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__
|
XPeekEvent(display, event_return)
      Display *display;
      XEvent *event_return;


display   Specifies the connection to the X server.

event_return
	  Returns a copy of the matched event's associated
	  structure.
|__

The XPeekEvent function returns the first event from the
event queue, but it does not remove the event from the
queue.	If the queue is empty, XPeekEvent flushes the output
buffer and blocks until an event is received.  It then
copies the event into the client-supplied XEvent structure
without removing it from the event queue.

11.4.2.  Selecting Events Using a Predicate Procedure

Each of the functions discussed in this section requires you
to pass a predicate procedure that determines if an event
matches what you want.	Your predicate procedure must decide
if the event is useful without calling any Xlib functions.
If the predicate directly or indirectly causes the state of
the event queue to change, the result is not defined.  If
Xlib has been initialized for threads, the predicate is
called with the display locked and the result of a call by
the predicate to any Xlib function that locks the display is
not defined unless the caller has first called XLockDisplay.

The predicate procedure and its associated arguments are:
__
|
Bool (*predicate)(display, event, arg)
     Display *display;
     XEvent *event;
     XPointer arg;


display   Specifies the connection to the X server.

event	  Specifies the XEvent structure.

arg	  Specifies the argument passed in from the
	  XIfEvent, XCheckIfEvent, or XPeekIfEvent function.
|__

The predicate procedure is called once for each event in the
queue until it finds a match.  After finding a match, the
predicate procedure must return True.  If it did not find a
match, it must return False.



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To check the event queue for a matching event and, if found,
remove the event from the queue, use XIfEvent.
__
|
XIfEvent(display, event_return, predicate, arg)
      Display *display;
      XEvent *event_return;
      Bool (*predicate)();
      XPointer arg;


display   Specifies the connection to the X server.

event_return
	  Returns the matched event's associated structure.

predicate Specifies the procedure that is to be called to
	  determine if the next event in the queue matches
	  what you want.

arg	  Specifies the user-supplied argument that will be
	  passed to the predicate procedure.
|__

The XIfEvent function completes only when the specified
predicate procedure returns True for an event, which indi-
cates an event in the queue matches.  XIfEvent flushes the
output buffer if it blocks waiting for additional events.
XIfEvent removes the matching event from the queue and
copies the structure into the client-supplied XEvent struc-
ture.


To check the event queue for a matching event without block-
ing, use XCheckIfEvent.






















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__
|
Bool XCheckIfEvent(display, event_return, predicate, arg)
      Display *display;
      XEvent *event_return;
      Bool (*predicate)();
      XPointer arg;


display   Specifies the connection to the X server.

event_return
	  Returns a copy of the matched event's associated
	  structure.

predicate Specifies the procedure that is to be called to
	  determine if the next event in the queue matches
	  what you want.

arg	  Specifies the user-supplied argument that will be
	  passed to the predicate procedure.
|__

When the predicate procedure finds a match, XCheckIfEvent
copies the matched event into the client-supplied XEvent
structure and returns True.  (This event is removed from the
queue.)  If the predicate procedure finds no match, XCheck-
IfEvent returns False, and the output buffer will have been
flushed.  All earlier events stored in the queue are not
discarded.


To check the event queue for a matching event without remov-
ing the event from the queue, use XPeekIfEvent.
























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__
|
XPeekIfEvent(display, event_return, predicate, arg)
      Display *display;
      XEvent *event_return;
      Bool (*predicate)();
      XPointer arg;


display   Specifies the connection to the X server.

event_return
	  Returns a copy of the matched event's associated
	  structure.

predicate Specifies the procedure that is to be called to
	  determine if the next event in the queue matches
	  what you want.

arg	  Specifies the user-supplied argument that will be
	  passed to the predicate procedure.
|__

The XPeekIfEvent function returns only when the specified
predicate procedure returns True for an event.	After the
predicate procedure finds a match, XPeekIfEvent copies the
matched event into the client-supplied XEvent structure
without removing the event from the queue.  XPeekIfEvent
flushes the output buffer if it blocks waiting for addi-
tional events.

11.4.3.  Selecting Events Using a Window or Event Mask

The functions discussed in this section let you select
events by window or event types, allowing you to process
events out of order.


To remove the next event that matches both a window and an
event mask, use XWindowEvent.


















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__
|
XWindowEvent(display, w, event_mask, event_return)
      Display *display;
      Window w;
      long event_mask;
      XEvent *event_return;


display   Specifies the connection to the X server.

w	  Specifies the window whose events you are inter-
	  ested in.

event_mask
	  Specifies the event mask.

event_return
	  Returns the matched event's associated structure.
|__

The XWindowEvent function searches the event queue for an
event that matches both the specified window and event mask.
When it finds a match, XWindowEvent removes that event from
the queue and copies it into the specified XEvent structure.
The other events stored in the queue are not discarded.  If
a matching event is not in the queue, XWindowEvent flushes
the output buffer and blocks until one is received.


To remove the next event that matches both a window and an
event mask (if any), use XCheckWindowEvent.  This function
is similar to XWindowEvent except that it never blocks and
it returns a Bool indicating if the event was returned.
























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__
|
Bool XCheckWindowEvent(display, w, event_mask, event_return)
      Display *display;
      Window w;
      long event_mask;
      XEvent *event_return;


display   Specifies the connection to the X server.

w	  Specifies the window whose events you are inter-
	  ested in.

event_mask
	  Specifies the event mask.

event_return
	  Returns the matched event's associated structure.
|__

The XCheckWindowEvent function searches the event queue and
then the events available on the server connection for the
first event that matches the specified window and event
mask.  If it finds a match, XCheckWindowEvent removes that
event, copies it into the specified XEvent structure, and
returns True.  The other events stored in the queue are not
discarded.  If the event you requested is not available,
XCheckWindowEvent returns False, and the output buffer will
have been flushed.


To remove the next event that matches an event mask, use
XMaskEvent.
__
|
XMaskEvent(display, event_mask, event_return)
      Display *display;
      long event_mask;
      XEvent *event_return;


display   Specifies the connection to the X server.

event_mask
	  Specifies the event mask.

event_return
	  Returns the matched event's associated structure.
|__

The XMaskEvent function searches the event queue for the
events associated with the specified mask.  When it finds a
match, XMaskEvent removes that event and copies it into the
specified XEvent structure.  The other events stored in the



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queue are not discarded.  If the event you requested is not
in the queue, XMaskEvent flushes the output buffer and
blocks until one is received.


To return and remove the next event that matches an event
mask (if any), use XCheckMaskEvent.  This function is simi-
lar to XMaskEvent except that it never blocks and it returns
a Bool indicating if the event was returned.
__
|
Bool XCheckMaskEvent(display, event_mask, event_return)
      Display *display;
      long event_mask;
      XEvent *event_return;


display   Specifies the connection to the X server.

event_mask
	  Specifies the event mask.

event_return
	  Returns the matched event's associated structure.
|__

The XCheckMaskEvent function searches the event queue and
then any events available on the server connection for the
first event that matches the specified mask.  If it finds a
match, XCheckMaskEvent removes that event, copies it into
the specified XEvent structure, and returns True.  The other
events stored in the queue are not discarded.  If the event
you requested is not available, XCheckMaskEvent returns
False, and the output buffer will have been flushed.


To return and remove the next event in the queue that
matches an event type, use XCheckTypedEvent.



















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__
|
Bool XCheckTypedEvent(display, event_type, event_return)
      Display *display;
      int event_type;
      XEvent *event_return;


display   Specifies the connection to the X server.

event_type
	  Specifies the event type to be compared.


event_return
	  Returns the matched event's associated structure.
|__

The XCheckTypedEvent function searches the event queue and
then any events available on the server connection for the
first event that matches the specified type.  If it finds a
match, XCheckTypedEvent removes that event, copies it into
the specified XEvent structure, and returns True.  The other
events in the queue are not discarded.	If the event is not
available, XCheckTypedEvent returns False, and the output
buffer will have been flushed.


To return and remove the next event in the queue that
matches an event type and a window, use XCheckTypedWindow-
Event.
__
|
Bool XCheckTypedWindowEvent(display, w, event_type, event_return)
      Display *display;
      Window w;
      int event_type;
      XEvent *event_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

event_type
	  Specifies the event type to be compared.


event_return
	  Returns the matched event's associated structure.
|__

The XCheckTypedWindowEvent function searches the event queue
and then any events available on the server connection for
the first event that matches the specified type and window.



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If it finds a match, XCheckTypedWindowEvent removes the
event from the queue, copies it into the specified XEvent
structure, and returns True.  The other events in the queue
are not discarded.  If the event is not available, XCheck-
TypedWindowEvent returns False, and the output buffer will
have been flushed.

11.5.  Putting an Event Back into the Queue

To push an event back into the event queue, use XPutBack-
Event.
__
|
XPutBackEvent(display, event)
      Display *display;
      XEvent *event;


display   Specifies the connection to the X server.

event	  Specifies the event.
|__

The XPutBackEvent function pushes an event back onto the
head of the display's event queue by copying the event into
the queue.  This can be useful if you read an event and then
decide that you would rather deal with it later.  There is
no limit to the number of times in succession that you can
call XPutBackEvent.

11.6.  Sending Events to Other Applications

To send an event to a specified window, use XSendEvent.
This function is often used in selection processing.  For
example, the owner of a selection should use XSendEvent to
send a SelectionNotify event to a requestor when a selection
has been converted and stored as a property.




















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__
|
Status XSendEvent(display, w, propagate, event_mask, event_send)
      Display *display;
      Window w;
      Bool propagate;
      long event_mask;
      XEvent *event_send;


display   Specifies the connection to the X server.

w	  Specifies the window the event is to be sent to,
	  or PointerWindow, or InputFocus.

propagate Specifies a Boolean value.

event_mask
	  Specifies the event mask.

event_send
	  Specifies the event that is to be sent.
|__

The XSendEvent function identifies the destination window,
determines which clients should receive the specified
events, and ignores any active grabs.  This function
requires you to pass an event mask.  For a discussion of the
valid event mask names, see section 10.3.  This function
uses the w argument to identify the destination window as
follows:

o    If w is PointerWindow, the destination window is the
     window that contains the pointer.

o    If w is InputFocus and if the focus window contains the
     pointer, the destination window is the window that con-
     tains the pointer; otherwise, the destination window is
     the focus window.

To determine which clients should receive the specified
events, XSendEvent uses the propagate argument as follows:

o    If event_mask is the empty set, the event is sent to
     the client that created the destination window.  If
     that client no longer exists, no event is sent.

o    If propagate is False, the event is sent to every
     client selecting on destination any of the event types
     in the event_mask argument.

o    If propagate is True and no clients have selected on
     destination any of the event types in event-mask, the
     destination is replaced with the closest ancestor of
     destination for which some client has selected a type



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     in event-mask and for which no intervening window has
     that type in its do-not-propagate-mask.  If no such
     window exists or if the window is an ancestor of the
     focus window and InputFocus was originally specified as
     the destination, the event is not sent to any clients.
     Otherwise, the event is reported to every client
     selecting on the final destination any of the types
     specified in event_mask.

The event in the XEvent structure must be one of the core
events or one of the events defined by an extension (or a
BadValue error results) so that the X server can correctly
byte-swap the contents as necessary.  The contents of the
event are otherwise unaltered and unchecked by the X server
except to force send_event to True in the forwarded event
and to set the serial number in the event correctly; there-
fore these fields and the display field are ignored by
XSendEvent.

XSendEvent returns zero if the conversion to wire protocol
format failed and returns nonzero otherwise.

XSendEvent can generate BadValue and BadWindow errors.

11.7.  Getting Pointer Motion History

Some X server implementations will maintain a more complete
history of pointer motion than is reported by event notifi-
cation.  The pointer position at each pointer hardware
interrupt may be stored in a buffer for later retrieval.
This buffer is called the motion history buffer.  For exam-
ple, a few applications, such as paint programs, want to
have a precise history of where the pointer traveled.  How-
ever, this historical information is highly excessive for
most applications.


To determine the approximate maximum number of elements in
the motion buffer, use XDisplayMotionBufferSize.
__
|
unsigned long XDisplayMotionBufferSize(display)
	Display *display;


display   Specifies the connection to the X server.
|__

The server may retain the recent history of the pointer
motion and do so to a finer granularity than is reported by
MotionNotify events.  The XGetMotionEvents function makes
this history available.





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To get the motion history for a specified window and time,
use XGetMotionEvents.
__
|
XTimeCoord *XGetMotionEvents(display, w, start, stop, nevents_return)
      Display *display;
      Window w;
      Time start, stop;
      int *nevents_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

start
stop	  Specify the time interval in which the events are
	  returned from the motion history buffer.  You can
	  pass a timestamp or CurrentTime.

nevents_return
	  Returns the number of events from the motion his-
	  tory buffer.
|__

The XGetMotionEvents function returns all events in the
motion history buffer that fall between the specified start
and stop times, inclusive, and that have coordinates that
lie within the specified window (including its borders) at
its present placement.	If the server does not support
motion history, if the start time is later than the stop
time, or if the start time is in the future, no events are
returned; XGetMotionEvents returns NULL.  If the stop time
is in the future, it is equivalent to specifying Current-
Time.  The return type for this function is a structure
defined as follows:

__
|
typedef struct {
     Time time;
     short x, y;
} XTimeCoord;

|__

The time member is set to the time, in milliseconds.  The x
and y members are set to the coordinates of the pointer and
are reported relative to the origin of the specified window.
To free the data returned from this call, use XFree.

XGetMotionEvents can generate a BadWindow error.





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11.8.  Handling Protocol Errors

Xlib provides functions that you can use to enable or dis-
able synchronization and to use the default error handlers.

11.8.1.  Enabling or Disabling Synchronization

When debugging X applications, it often is very convenient
to require Xlib to behave synchronously so that errors are
reported as they occur.  The following function lets you
disable or enable synchronous behavior.  Note that graphics
may occur 30 or more times more slowly when synchronization
is enabled.  On POSIX-conformant systems, there is also a
global variable _Xdebug that, if set to nonzero before
starting a program under a debugger, will force synchronous
library behavior.

After completing their work, all Xlib functions that gener-
ate protocol requests call what is known as an after func-
tion.  XSetAfterFunction sets which function is to be
called.
__
|
int (*XSetAfterFunction(display, procedure))()
      Display *display;
      int (*procedure)();


display   Specifies the connection to the X server.

procedure Specifies the procedure to be called.
|__

The specified procedure is called with only a display
pointer.  XSetAfterFunction returns the previous after func-
tion.

To enable or disable synchronization, use XSynchronize.
__
|
int (*XSynchronize(display, onoff))()
      Display *display;
      Bool onoff;


display   Specifies the connection to the X server.

onoff	  Specifies a Boolean value that indicates whether
	  to enable or disable synchronization.
|__

The XSynchronize function returns the previous after func-
tion.  If onoff is True, XSynchronize turns on synchronous
behavior.  If onoff is False, XSynchronize turns off



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synchronous behavior.

11.8.2.  Using the Default Error Handlers

There are two default error handlers in Xlib: one to handle
typically fatal conditions (for example, the connection to a
display server dying because a machine crashed) and one to
handle protocol errors from the X server.  These error han-
dlers can be changed to user-supplied routines if you prefer
your own error handling and can be changed as often as you
like.  If either function is passed a NULL pointer, it will
reinvoke the default handler.  The action of the default
handlers is to print an explanatory message and exit.


To set the error handler, use XSetErrorHandler.
__
|
int (*XSetErrorHandler(handler))()
      int (*handler)(Display *, XErrorEvent *)


handler   Specifies the program's supplied error handler.
|__

Xlib generally calls the program's supplied error handler
whenever an error is received.	It is not called on BadName
errors from OpenFont, LookupColor, or AllocNamedColor proto-
col requests or on BadFont errors from a QueryFont protocol
request.  These errors generally are reflected back to the
program through the procedural interface.  Because this con-
dition is not assumed to be fatal, it is acceptable for your
error handler to return; the returned value is ignored.
However, the error handler should not call any functions
(directly or indirectly) on the display that will generate
protocol requests or that will look for input events.  The
previous error handler is returned.

The XErrorEvent structure contains:


typedef struct {
     int type;
     Display *display;	 /* Display the event was read from */
     unsigned long serial;/* serial number of failed request */
     unsigned char error_code;/* error code of failed request */
     unsigned char request_code;/* Major op-code of failed request */
     unsigned char minor_code;/* Minor op-code of failed request */
     XID resourceid;	 /* resource id */
} XErrorEvent;


The serial member is the number of requests, starting from
one, sent over the network connection since it was opened.



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It is the number that was the value of NextRequest immedi-
ately before the failing call was made.  The request_code
member is a protocol request of the procedure that failed,
as defined in <X11/Xproto.h>.  The following error codes can
be returned by the functions described in this chapter:

-------------------------------------------------------------
Error Code			  Description
-------------------------------------------------------------
BadAccess	    A client attempts to grab a key/button
		    combination already grabbed by another
		    client.
		    A client attempts to free a colormap
		    entry that it had not already allocated
		    or to free an entry in a colormap that
		    was created with all entries writable.
		    A client attempts to store into a read-
		    only or unallocated colormap entry.
		    A client attempts to modify the access
		    control list from other than the local
		    (or otherwise authorized) host.
		    A client attempts to select an event
		    type that another client has already
		    selected.
BadAlloc	    The server fails to allocate the
		    requested resource.  Note that the
		    explicit listing of BadAlloc errors in
		    requests only covers allocation errors
		    at a very coarse level and is not
		    intended to (nor can it in practice hope
		    to) cover all cases of a server running
		    out of allocation space in the middle of
		    service.  The semantics when a server
		    runs out of allocation space are left
		    unspecified, but a server may generate a
		    BadAlloc error on any request for this
		    reason, and clients should be prepared
		    to receive such errors and handle or
		    discard them.
BadAtom 	    A value for an atom argument does not
		    name a defined atom.
BadColor	    A value for a colormap argument does not
		    name a defined colormap.
BadCursor	    A value for a cursor argument does not
		    name a defined cursor.
BadDrawable	    A value for a drawable argument does not
		    name a defined window or pixmap.
BadFont 	    A value for a font argument does not
		    name a defined font (or, in some cases,
		    GContext).
BadGC		    A value for a GContext argument does not
		    name a defined GContext.





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-------------------------------------------------------------
Error Code			  Description
-------------------------------------------------------------
BadIDChoice	    The value chosen for a resource identi-
		    fier either is not included in the range
		    assigned to the client or is already in
		    use.  Under normal circumstances, this
		    cannot occur and should be considered a
		    server or Xlib error.
BadImplementation   The server does not implement some
		    aspect of the request.  A server that
		    generates this error for a core request
		    is deficient.  As such, this error is
		    not listed for any of the requests, but
		    clients should be prepared to receive
		    such errors and handle or discard them.
BadLength	    The length of a request is shorter or
		    longer than that required to contain the
		    arguments.	This is an internal Xlib or
		    server error.
		    The length of a request exceeds the max-
		    imum length accepted by the server.
BadMatch	    In a graphics request, the root and
		    depth of the graphics context do not
		    match those of the drawable.
		    An InputOnly window is used as a draw-
		    able.
		    Some argument or pair of arguments has
		    the correct type and range, but it fails
		    to match in some other way required by
		    the request.
		    An InputOnly window lacks this
		    attribute.
BadName 	    A font or color of the specified name
		    does not exist.
BadPixmap	    A value for a pixmap argument does not
		    name a defined pixmap.
BadRequest	    The major or minor opcode does not spec-
		    ify a valid request.  This usually is an
		    Xlib or server error.
BadValue	    Some numeric value falls outside of the
		    range of values accepted by the request.
		    Unless a specific range is specified for
		    an argument, the full range defined by
		    the argument's type is accepted.  Any
		    argument defined as a set of alterna-
		    tives typically can generate this error
		    (due to the encoding).
BadWindow	    A value for a window argument does not
		    name a defined window.
-------------------------------------------------------------






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			    Note

     The BadAtom, BadColor, BadCursor, BadDrawable,
     BadFont, BadGC, BadPixmap, and BadWindow errors
     are also used when the argument type is extended
     by a set of fixed alternatives.



To obtain textual descriptions of the specified error code,
use XGetErrorText.
__
|
XGetErrorText(display, code, buffer_return, length)
      Display *display;
      int code;
      char *buffer_return;
      int length;


display   Specifies the connection to the X server.

code	  Specifies the error code for which you want to
	  obtain a description.

buffer_return
	  Returns the error description.

length	  Specifies the size of the buffer.
|__

The XGetErrorText function copies a null-terminated string
describing the specified error code into the specified
buffer.  The returned text is in the encoding of the current
locale.  It is recommended that you use this function to
obtain an error description because extensions to Xlib may
define their own error codes and error strings.


To obtain error messages from the error database, use
XGetErrorDatabaseText.
















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__
|
XGetErrorDatabaseText(display, name, message, default_string, buffer_return, length)
      Display *display;
      char *name, *message;
      char *default_string;
      char *buffer_return;
      int length;


display   Specifies the connection to the X server.

name	  Specifies the name of the application.

message   Specifies the type of the error message.

default_string
	  Specifies the default error message if none is
	  found in the database.

buffer_return
	  Returns the error description.

length	  Specifies the size of the buffer.
|__

The XGetErrorDatabaseText function returns a null-terminated
message (or the default message) from the error message
database.  Xlib uses this function internally to look up its
error messages.  The text in the default_string argument is
assumed to be in the encoding of the current locale, and the
text stored in the buffer_return argument is in the encoding
of the current locale.

The name argument should generally be the name of your
application.  The message argument should indicate which
type of error message you want.  If the name and message are
not in the Host Portable Character Encoding, the result is
implementation-dependent.  Xlib uses three predefined
``application names'' to report errors.  In these names,
uppercase and lowercase matter.

XProtoError
	  The protocol error number is used as a string for
	  the message argument.

XlibMessage
	  These are the message strings that are used inter-
	  nally by the library.

XRequest  For a core protocol request, the major request
	  protocol number is used for the message argument.
	  For an extension request, the extension name (as
	  given by InitExtension) followed by a period (.)
	  and the minor request protocol number is used for



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	  the message argument.  If no string is found in
	  the error database, the default_string is returned
	  to the buffer argument.


To report an error to the user when the requested display
does not exist, use XDisplayName.
__
|
char *XDisplayName(string)
      char *string;


string	  Specifies the character string.
|__

The XDisplayName function returns the name of the display
that XOpenDisplay would attempt to use.  If a NULL string is
specified, XDisplayName looks in the environment for the
display and returns the display name that XOpenDisplay would
attempt to use.  This makes it easier to report to the user
precisely which display the program attempted to open when
the initial connection attempt failed.


To handle fatal I/O errors, use XSetIOErrorHandler.
__
|
int (*XSetIOErrorHandler(handler))()
      int (*handler)(Display *);


handler   Specifies the program's supplied error handler.
|__

The XSetIOErrorHandler sets the fatal I/O error handler.
Xlib calls the program's supplied error handler if any sort
of system call error occurs (for example, the connection to
the server was lost).  This is assumed to be a fatal condi-
tion, and the called routine should not return.  If the I/O
error handler does return, the client process exits.

Note that the previous error handler is returned.














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			 Chapter 12

		   Input Device Functions



You can use the Xlib input device functions to:

o    Grab the pointer and individual buttons on the pointer

o    Grab the keyboard and individual keys on the keyboard

o    Resume event processing

o    Move the pointer

o    Set the input focus

o    Manipulate the keyboard and pointer settings

o    Manipulate the keyboard encoding

12.1.  Pointer Grabbing

Xlib provides functions that you can use to control input
from the pointer, which usually is a mouse.  Usually, as
soon as keyboard and mouse events occur, the X server deliv-
ers them to the appropriate client, which is determined by
the window and input focus.  The X server provides suffi-
cient control over event delivery to allow window managers
to support mouse ahead and various other styles of user
interface.  Many of these user interfaces depend on syn-
chronous delivery of events.  The delivery of  pointer and
keyboard events can be controlled independently.

When mouse buttons or keyboard keys are grabbed, events will
be sent to the grabbing client rather than the normal client
who would have received the event.  If the keyboard or
pointer is in asynchronous mode, further mouse and keyboard
events will continue to be processed.  If the keyboard or
pointer is in synchronous mode, no further events are pro-
cessed until the grabbing client allows them (see XAllow-
Events).  The keyboard or pointer is considered frozen dur-
ing this interval.  The event that triggered the grab can
also be replayed.

Note that the logical state of a device (as seen by client
applications) may lag the physical state if device event
processing is frozen.

There are two kinds of grabs: active and passive.  An active
grab occurs when a single client grabs the keyboard and/or



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pointer explicitly (see XGrabPointer and XGrabKeyboard).  A
passive grab occurs when clients grab a particular keyboard
key or pointer button in a window, and the grab will acti-
vate when the key or button is actually pressed.  Passive
grabs are convenient for implementing reliable pop-up menus.
For example, you can guarantee that the pop-up is mapped
before the up pointer button event occurs by grabbing a but-
ton requesting synchronous behavior.  The down event will
trigger the grab and freeze further processing of pointer
events until you have the chance to map the pop-up window.
You can then allow further event processing.  The up event
will then be correctly processed relative to the pop-up win-
dow.

For many operations, there are functions that take a time
argument.  The X server includes a timestamp in various
events.  One special time, called CurrentTime, represents
the current server time.  The X server maintains the time
when the input focus was last changed, when the keyboard was
last grabbed, when the pointer was last grabbed, or when a
selection was last changed.  Your application may be slow
reacting to an event.  You often need some way to specify
that your request should not occur if another application
has in the meanwhile taken control of the keyboard, pointer,
or selection.  By providing the timestamp from the event in
the request, you can arrange that the operation not take
effect if someone else has performed an operation in the
meanwhile.

A timestamp is a time value, expressed in milliseconds.  It
typically is the time since the last server reset.  Times-
tamp values wrap around (after about 49.7 days).  The
server, given its current time is represented by timestamp
T, always interprets timestamps from clients by treating
half of the timestamp space as being later in time than T.
One timestamp value, named CurrentTime, is never generated
by the server.	This value is reserved for use in requests
to represent the current server time.

For many functions in this section, you pass pointer event
mask bits.  The valid pointer event mask bits are: Button-
PressMask, ButtonReleaseMask, EnterWindowMask, LeaveWindow-
Mask, PointerMotionMask, PointerMotionHintMask, But-
ton1MotionMask, Button2MotionMask, Button3MotionMask, But-
ton4MotionMask, Button5MotionMask, ButtonMotionMask, and
KeyMapStateMask.  For other functions in this section, you
pass keymask bits.  The valid keymask bits are: ShiftMask,
LockMask, ControlMask, Mod1Mask, Mod2Mask, Mod3Mask,
Mod4Mask, and Mod5Mask.


To grab the pointer, use XGrabPointer.





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__
|
int XGrabPointer(display, grab_window, owner_events, event_mask, pointer_mode,
	       keyboard_mode, confine_to, cursor, time)
      Display *display;
      Window grab_window;
      Bool owner_events;
      unsigned int event_mask;
      int pointer_mode, keyboard_mode;
      Window confine_to;
      Cursor cursor;
      Time time;


display   Specifies the connection to the X server.

grab_window
	  Specifies the grab window.

owner_events
	  Specifies a Boolean value that indicates whether
	  the pointer events are to be reported as usual or
	  reported with respect to the grab window if
	  selected by the event mask.

event_mask
	  Specifies which pointer events are reported to the
	  client.  The mask is the bitwise inclusive OR of
	  the valid pointer event mask bits.

pointer_mode
	  Specifies further processing of pointer events.
	  You can pass GrabModeSync or GrabModeAsync.

keyboard_mode
	  Specifies further processing of keyboard events.
	  You can pass GrabModeSync or GrabModeAsync.

confine_to
	  Specifies the window to confine the pointer in or
	  None.

cursor	  Specifies the cursor that is to be displayed dur-
	  ing the grab or None.

time	  Specifies the time.  You can pass either a times-
	  tamp or CurrentTime.
|__

The XGrabPointer function actively grabs control of the
pointer and returns GrabSuccess if the grab was successful.
Further pointer events are reported only to the grabbing
client.  XGrabPointer overrides any active pointer grab by
this client.  If owner_events is False, all generated
pointer events are reported with respect to grab_window and



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are reported only if selected by event_mask.  If
owner_events is True and if a generated pointer event would
normally be reported to this client, it is reported as
usual.	Otherwise, the event is reported with respect to the
grab_window and is reported only if selected by event_mask.
For either value of owner_events, unreported events are dis-
carded.

If the pointer_mode is GrabModeAsync, pointer event process-
ing continues as usual.  If the pointer is currently frozen
by this client, the processing of events for the pointer is
resumed.  If the pointer_mode is GrabModeSync, the state of
the pointer, as seen by client applications, appears to
freeze, and the X server generates no further pointer events
until the grabbing client calls XAllowEvents or until the
pointer grab is released.  Actual pointer changes are not
lost while the pointer is frozen; they are simply queued in
the server for later processing.

If the keyboard_mode is GrabModeAsync, keyboard event pro-
cessing is unaffected by activation of the grab.  If the
keyboard_mode is GrabModeSync, the state of the keyboard, as
seen by client applications, appears to freeze, and the X
server generates no further keyboard events until the grab-
bing client calls XAllowEvents or until the pointer grab is
released.  Actual keyboard changes are not lost while the
pointer is frozen; they are simply queued in the server for
later processing.

If a cursor is specified, it is displayed regardless of what
window the pointer is in.  If None is specified, the normal
cursor for that window is displayed when the pointer is in
grab_window or one of its subwindows; otherwise, the cursor
for grab_window is displayed.

If a confine_to window is specified, the pointer is
restricted to stay contained in that window.  The confine_to
window need have no relationship to the grab_window.  If the
pointer is not initially in the confine_to window, it is
warped automatically to the closest edge just before the
grab activates and enter/leave events are generated as
usual.	If the confine_to window is subsequently reconfig-
ured, the pointer is warped automatically, as necessary, to
keep it contained in the window.

The time argument allows you to avoid certain circumstances
that come up if applications take a long time to respond or
if there are long network delays.  Consider a situation
where you have two applications, both of which normally grab
the pointer when clicked on.  If both applications specify
the timestamp from the event, the second application may
wake up faster and successfully grab the pointer before the
first application.  The first application then will get an
indication that the other application grabbed the pointer



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before its request was processed.

XGrabPointer generates EnterNotify and LeaveNotify events.

Either if grab_window or confine_to window is not viewable
or if the confine_to window lies completely outside the
boundaries of the root window, XGrabPointer fails and
returns GrabNotViewable.  If the pointer is actively grabbed
by some other client, it fails and returns AlreadyGrabbed.
If the pointer is frozen by an active grab of another
client, it fails and returns GrabFrozen.  If the specified
time is earlier than the last-pointer-grab time or later
than the current X server time, it fails and returns GrabIn-
validTime.  Otherwise, the last-pointer-grab time is set to
the specified time (CurrentTime is replaced by the current X
server time).

XGrabPointer can generate BadCursor, BadValue, and BadWindow
errors.


To ungrab the pointer, use XUngrabPointer.
__
|
XUngrabPointer(display, time)
      Display *display;
      Time time;


display   Specifies the connection to the X server.

time	  Specifies the time.  You can pass either a times-
	  tamp or CurrentTime.
|__

The XUngrabPointer function releases the pointer and any
queued events if this client has actively grabbed the
pointer from XGrabPointer, XGrabButton, or from a normal
button press.  XUngrabPointer does not release the pointer
if the specified time is earlier than the last-pointer-grab
time or is later than the current X server time.  It also
generates EnterNotify and LeaveNotify events.  The X server
performs an UngrabPointer request automatically if the event
window or confine_to window for an active pointer grab
becomes not viewable or if window reconfiguration causes the
confine_to window to lie completely outside the boundaries
of the root window.


To change an active pointer grab, use XChangeActivePointer-
Grab.






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__
|
XChangeActivePointerGrab(display, event_mask, cursor, time)
      Display *display;
      unsigned int event_mask;
      Cursor cursor;
      Time time;


display   Specifies the connection to the X server.

event_mask
	  Specifies which pointer events are reported to the
	  client.  The mask is the bitwise inclusive OR of
	  the valid pointer event mask bits.

cursor	  Specifies the cursor that is to be displayed or
	  None.

time	  Specifies the time.  You can pass either a times-
	  tamp or CurrentTime.
|__

The XChangeActivePointerGrab function changes the specified
dynamic parameters if the pointer is actively grabbed by the
client and if the specified time is no earlier than the
last-pointer-grab time and no later than the current X
server time.  This function has no effect on the passive
parameters of an XGrabButton.  The interpretation of
event_mask and cursor is the same as described in XGrab-
Pointer.

XChangeActivePointerGrab can generate BadCursor and BadValue
errors.


To grab a pointer button, use XGrabButton.





















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__
|
XGrabButton(display, button, modifiers, grab_window, owner_events, event_mask,
		pointer_mode, keyboard_mode, confine_to, cursor)
      Display *display;
      unsigned int button;
      unsigned int modifiers;
      Window grab_window;
      Bool owner_events;
      unsigned int event_mask;
      int pointer_mode, keyboard_mode;
      Window confine_to;
      Cursor cursor;


display   Specifies the connection to the X server.

button	  Specifies the pointer button that is to be grabbed
	  or AnyButton.

modifiers Specifies the set of keymasks or AnyModifier.  The
	  mask is the bitwise inclusive OR of the valid key-
	  mask bits.

grab_window
	  Specifies the grab window.

owner_events
	  Specifies a Boolean value that indicates whether
	  the pointer events are to be reported as usual or
	  reported with respect to the grab window if
	  selected by the event mask.

event_mask
	  Specifies which pointer events are reported to the
	  client.  The mask is the bitwise inclusive OR of
	  the valid pointer event mask bits.

pointer_mode
	  Specifies further processing of pointer events.
	  You can pass GrabModeSync or GrabModeAsync.

keyboard_mode
	  Specifies further processing of keyboard events.
	  You can pass GrabModeSync or GrabModeAsync.

confine_to
	  Specifies the window to confine the pointer in or
	  None.

cursor	  Specifies the cursor that is to be displayed or
	  None.
|__

The XGrabButton function establishes a passive grab.  In the



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future, the pointer is actively grabbed (as for XGrab-
Pointer), the last-pointer-grab time is set to the time at
which the button was pressed (as transmitted in the Button-
Press event), and the ButtonPress event is reported if all
of the following conditions are true:

o    The pointer is not grabbed, and the specified button is
     logically pressed when the specified modifier keys are
     logically down, and no other buttons or modifier keys
     are logically down.

o    The grab_window contains the pointer.

o    The confine_to window (if any) is viewable.

o    A passive grab on the same button/key combination does
     not exist on any ancestor of grab_window.

The interpretation of the remaining arguments is as for
XGrabPointer.  The active grab is terminated automatically
when the logical state of the pointer has all buttons
released (independent of the state of the logical modifier
keys).

Note that the logical state of a device (as seen by client
applications) may lag the physical state if device event
processing is frozen.

This request overrides all previous grabs by the same client
on the same button/key combinations on the same window.  A
modifiers of AnyModifier is equivalent to issuing the grab
request for all possible modifier combinations (including
the combination of no modifiers).  It is not required that
all modifiers specified have currently assigned KeyCodes.  A
button of AnyButton is equivalent to issuing the request for
all possible buttons.  Otherwise, it is not required that
the specified button currently be assigned to a physical
button.

If some other client has already issued an XGrabButton with
the same button/key combination on the same window, a BadAc-
cess error results.  When using AnyModifier or AnyButton,
the request fails completely, and a BadAccess error results
(no grabs are established) if there is a conflicting grab
for any combination.  XGrabButton has no effect on an active
grab.

XGrabButton can generate BadCursor, BadValue, and BadWindow
errors.


To ungrab a pointer button, use XUngrabButton.





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__
|
XUngrabButton(display, button, modifiers, grab_window)
      Display *display;
      unsigned int button;
      unsigned int modifiers;
      Window grab_window;


display   Specifies the connection to the X server.

button	  Specifies the pointer button that is to be
	  released or AnyButton.

modifiers Specifies the set of keymasks or AnyModifier.  The
	  mask is the bitwise inclusive OR of the valid key-
	  mask bits.

grab_window
	  Specifies the grab window.
|__

The XUngrabButton function releases the passive button/key
combination on the specified window if it was grabbed by
this client.  A modifiers of AnyModifier is equivalent to
issuing the ungrab request for all possible modifier combi-
nations, including the combination of no modifiers.  A but-
ton of AnyButton is equivalent to issuing the request for
all possible buttons.  XUngrabButton has no effect on an
active grab.

XUngrabButton can generate BadValue and BadWindow errors.

12.2.  Keyboard Grabbing

Xlib provides functions that you can use to grab or ungrab
the keyboard as well as allow events.

For many functions in this section, you pass keymask bits.
The valid keymask bits are: ShiftMask, LockMask, Control-
Mask, Mod1Mask, Mod2Mask, Mod3Mask, Mod4Mask, and Mod5Mask.


To grab the keyboard, use XGrabKeyboard.














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__
|
int XGrabKeyboard(display, grab_window, owner_events, pointer_mode, keyboard_mode, time)
      Display *display;
      Window grab_window;
      Bool owner_events;
      int pointer_mode, keyboard_mode;
      Time time;


display   Specifies the connection to the X server.

grab_window
	  Specifies the grab window.

owner_events
	  Specifies a Boolean value that indicates whether
	  the keyboard events are to be reported as usual.

pointer_mode
	  Specifies further processing of pointer events.
	  You can pass GrabModeSync or GrabModeAsync.

keyboard_mode
	  Specifies further processing of keyboard events.
	  You can pass GrabModeSync or GrabModeAsync.

time	  Specifies the time.  You can pass either a times-
	  tamp or CurrentTime.
|__

The XGrabKeyboard function actively grabs control of the
keyboard and generates FocusIn and FocusOut events.  Further
key events are reported only to the grabbing client.
XGrabKeyboard overrides any active keyboard grab by this
client.  If owner_events is False, all generated key events
are reported with respect to grab_window.  If owner_events
is True and if a generated key event would normally be
reported to this client, it is reported normally; otherwise,
the event is reported with respect to the grab_window.	Both
KeyPress and KeyRelease events are always reported, indepen-
dent of any event selection made by the client.

If the keyboard_mode argument is GrabModeAsync, keyboard
event processing continues as usual.  If the keyboard is
currently frozen by this client, then processing of keyboard
events is resumed.  If the keyboard_mode  argument is Grab-
ModeSync, the state of the keyboard (as seen by client
applications) appears to freeze, and the X server generates
no further keyboard events until the grabbing client issues
a releasing XAllowEvents call or until the keyboard grab is
released.  Actual keyboard changes are not lost while the
keyboard is frozen; they are simply queued in the server for
later processing.




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If pointer_mode is GrabModeAsync, pointer event processing
is unaffected by activation of the grab.  If pointer_mode is
GrabModeSync, the state of the pointer (as seen by client
applications) appears to freeze, and the X server generates
no further pointer events until the grabbing client issues a
releasing XAllowEvents call or until the keyboard grab is
released.  Actual pointer changes are not lost while the
pointer is frozen; they are simply queued in the server for
later processing.

If the keyboard is actively grabbed by some other client,
XGrabKeyboard fails and returns AlreadyGrabbed.  If
grab_window is not viewable, it fails and returns Grab-
NotViewable.  If the keyboard is frozen by an active grab of
another client, it fails and returns GrabFrozen.  If the
specified time is earlier than the last-keyboard-grab time
or later than the current X server time, it fails and
returns GrabInvalidTime.  Otherwise, the last-keyboard-grab
time is set to the specified time (CurrentTime is replaced
by the current X server time).

XGrabKeyboard can generate BadValue and BadWindow errors.


To ungrab the keyboard, use XUngrabKeyboard.
__
|
XUngrabKeyboard(display, time)
      Display *display;
      Time time;


display   Specifies the connection to the X server.

time	  Specifies the time.  You can pass either a times-
	  tamp or CurrentTime.
|__

The XUngrabKeyboard function releases the keyboard and any
queued events if this client has it actively grabbed from
either XGrabKeyboard or XGrabKey.  XUngrabKeyboard does not
release the keyboard and any queued events if the specified
time is earlier than the last-keyboard-grab time or is later
than the current X server time.  It also generates FocusIn
and FocusOut events.  The X server automatically performs an
UngrabKeyboard request if the event window for an active
keyboard grab becomes not viewable.


To passively grab a single key of the keyboard, use
XGrabKey.






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__
|
XGrabKey(display, keycode, modifiers, grab_window, owner_events, pointer_mode,
	     keyboard_mode)
      Display *display;
      int keycode;
      unsigned int modifiers;
      Window grab_window;
      Bool owner_events;
      int pointer_mode, keyboard_mode;


display   Specifies the connection to the X server.

keycode   Specifies the KeyCode or AnyKey.

modifiers Specifies the set of keymasks or AnyModifier.  The
	  mask is the bitwise inclusive OR of the valid key-
	  mask bits.

grab_window
	  Specifies the grab window.

owner_events
	  Specifies a Boolean value that indicates whether
	  the keyboard events are to be reported as usual.

pointer_mode
	  Specifies further processing of pointer events.
	  You can pass GrabModeSync or GrabModeAsync.

keyboard_mode
	  Specifies further processing of keyboard events.
	  You can pass GrabModeSync or GrabModeAsync.
|__

The XGrabKey function establishes a passive grab on the key-
board.	In the future, the keyboard is actively grabbed (as
for XGrabKeyboard), the last-keyboard-grab time is set to
the time at which the key was pressed (as transmitted in the
KeyPress event), and the KeyPress event is reported if all
of the following conditions are true:

o    The keyboard is not grabbed and the specified key
     (which can itself be a modifier key) is logically
     pressed when the specified modifier keys are logically
     down, and no other modifier keys are logically down.

o    Either the grab_window is an ancestor of (or is) the
     focus window, or the grab_window is a descendant of the
     focus window and contains the pointer.

o    A passive grab on the same key combination does not
     exist on any ancestor of grab_window.




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The interpretation of the remaining arguments is as for
XGrabKeyboard.	The active grab is terminated automatically
when the logical state of the keyboard has the specified key
released (independent of the logical state of the modifier
keys).

Note that the logical state of a device (as seen by client
applications) may lag the physical state if device event
processing is frozen.

A modifiers argument of AnyModifier is equivalent to issuing
the request for all possible modifier combinations (includ-
ing the combination of no modifiers).  It is not required
that all modifiers specified have currently assigned Key-
Codes.	A keycode argument of AnyKey is equivalent to issu-
ing the request for all possible KeyCodes.  Otherwise, the
specified keycode must be in the range specified by min_key-
code and max_keycode in the connection setup, or a BadValue
error results.

If some other client has issued a XGrabKey with the same key
combination on the same window, a BadAccess error results.
When using AnyModifier or AnyKey, the request fails com-
pletely, and a BadAccess error results (no grabs are estab-
lished) if there is a conflicting grab for any combination.

XGrabKey can generate BadAccess, BadValue, and BadWindow
errors.


To ungrab a key, use XUngrabKey.
__
|
XUngrabKey(display, keycode, modifiers, grab_window)
      Display *display;
      int keycode;
      unsigned int modifiers;
      Window grab_window;


display   Specifies the connection to the X server.

keycode   Specifies the KeyCode or AnyKey.

modifiers Specifies the set of keymasks or AnyModifier.  The
	  mask is the bitwise inclusive OR of the valid key-
	  mask bits.

grab_window
	  Specifies the grab window.
|__

The XUngrabKey function releases the key combination on the
specified window if it was grabbed by this client.  It has



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no effect on an active grab.  A modifiers of AnyModifier is
equivalent to issuing the request for all possible modifier
combinations (including the combination of no modifiers).  A
keycode argument of AnyKey is equivalent to issuing the
request for all possible key codes.

XUngrabKey can generate BadValue and BadWindow errors.

12.3.  Resuming Event Processing

The previous sections discussed grab mechanisms with which
processing of events by the server can be temporarily sus-
pended.  This section describes the mechanism for resuming
event processing.


To allow further events to be processed when the device has
been frozen, use XAllowEvents.
__
|
XAllowEvents(display, event_mode, time)
      Display *display;
      int event_mode;
      Time time;


display   Specifies the connection to the X server.

event_mode
	  Specifies the event mode.  You can pass Async-
	  Pointer, SyncPointer, AsyncKeyboard, SyncKeyboard,
	  ReplayPointer, ReplayKeyboard, AsyncBoth, or
	  SyncBoth.

time	  Specifies the time.  You can pass either a times-
	  tamp or CurrentTime.
|__

The XAllowEvents function releases some queued events if the
client has caused a device to freeze.  It has no effect if
the specified time is earlier than the last-grab time of the
most recent active grab for the client or if the specified
time is later than the current X server time.  Depending on
the event_mode argument, the following occurs:

AsyncPointer   If the pointer is frozen by the client,
	       pointer event processing continues as usual.
	       If the pointer is frozen twice by the client
	       on behalf of two separate grabs, AsyncPointer
	       thaws for both.	AsyncPointer has no effect
	       if the pointer is not frozen by the client,
	       but the pointer need not be grabbed by the
	       client.




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SyncPointer    If the pointer is frozen and actively grabbed
	       by the client, pointer event processing con-
	       tinues as usual until the next ButtonPress or
	       ButtonRelease event is reported to the
	       client.	At this time, the pointer again
	       appears to freeze.  However, if the reported
	       event causes the pointer grab to be released,
	       the pointer does not freeze.  SyncPointer has
	       no effect if the pointer is not frozen by the
	       client or if the pointer is not grabbed by
	       the client.
Replay-        If the pointer is actively grabbed by the
Pointer        client and is frozen as the result of an
	       event having been sent to the client (either
	       from the activation of an XGrabButton or from
	       a previous XAllowEvents with mode SyncPointer
	       but not from an XGrabPointer), the pointer
	       grab is released and that event is completely
	       reprocessed.  This time, however, the func-
	       tion ignores any passive grabs at or above
	       (toward the root of) the grab_window of the
	       grab just released.  The request has no
	       effect if the pointer is not grabbed by the
	       client or if the pointer is not frozen as the
	       result of an event.
AsyncKey-      If the keyboard is frozen by the client, key-
board	       board event processing continues as usual.
	       If the keyboard is frozen twice by the client
	       on behalf of two separate grabs, AsyncKey-
	       board thaws for both.  AsyncKeyboard has no
	       effect if the keyboard is not frozen by the
	       client, but the keyboard need not be grabbed
	       by the client.
SyncKeyboard   If the keyboard is frozen and actively
	       grabbed by the client, keyboard event pro-
	       cessing continues as usual until the next
	       KeyPress or KeyRelease event is reported to
	       the client.  At this time, the keyboard again
	       appears to freeze.  However, if the reported
	       event causes the keyboard grab to be
	       released, the keyboard does not freeze.
	       SyncKeyboard has no effect if the keyboard is
	       not frozen by the client or if the keyboard
	       is not grabbed by the client.













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ReplayKey-     If the keyboard is actively grabbed by the
board	       client and is frozen as the result of an
	       event having been sent to the client (either
	       from the activation of an XGrabKey or from a
	       previous XAllowEvents with mode SyncKeyboard
	       but not from an XGrabKeyboard), the keyboard
	       grab is released and that event is completely
	       reprocessed.  This time, however, the func-
	       tion ignores any passive grabs at or above
	       (toward the root of) the grab_window of the
	       grab just released.  The request has no
	       effect if the keyboard is not grabbed by the
	       client or if the keyboard is not frozen as
	       the result of an event.
SyncBoth       If both pointer and keyboard are frozen by
	       the client, event processing for both devices
	       continues as usual until the next Button-
	       Press, ButtonRelease, KeyPress, or KeyRelease
	       event is reported to the client for a grabbed
	       device (button event for the pointer, key
	       event for the keyboard), at which time the
	       devices again appear to freeze.	However, if
	       the reported event causes the grab to be
	       released, then the devices do not freeze (but
	       if the other device is still grabbed, then a
	       subsequent event for it will still cause both
	       devices to freeze).  SyncBoth has no effect
	       unless both pointer and keyboard are frozen
	       by the client.  If the pointer or keyboard is
	       frozen twice by the client on behalf of two
	       separate grabs, SyncBoth thaws for both (but
	       a subsequent freeze for SyncBoth will only
	       freeze each device once).
AsyncBoth      If the pointer and the keyboard are frozen by
	       the client, event processing for both devices
	       continues as usual.  If a device is frozen
	       twice by the client on behalf of two separate
	       grabs, AsyncBoth thaws for both.  AsyncBoth
	       has no effect unless both pointer and key-
	       board are frozen by the client.


AsyncPointer, SyncPointer, and ReplayPointer have no effect
on the processing of keyboard events.  AsyncKeyboard, SyncK-
eyboard, and ReplayKeyboard have no effect on the processing
of pointer events.  It is possible for both a pointer grab
and a keyboard grab (by the same or different clients) to be
active simultaneously.	If a device is frozen on behalf of
either grab, no event processing is performed for the
device.  It is possible for a single device to be frozen
because of both grabs.	In this case, the freeze must be
released on behalf of both grabs before events can again be
processed.  If a device is frozen twice by a single client,
then a single AllowEvents releases both.



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XAllowEvents can generate a BadValue error.

12.4.  Moving the Pointer

Although movement of the pointer normally should be left to
the control of the end user, sometimes it is necessary to
move the pointer to a new position under program control.


To move the pointer to an arbitrary point in a window, use
XWarpPointer.
__
|
XWarpPointer(display, src_w, dest_w, src_x, src_y, src_width, src_height, dest_x,
		dest_y)
	Display *display;
	Window src_w, dest_w;
	int src_x, src_y;
	unsigned int src_width, src_height;
	int dest_x, dest_y;


display   Specifies the connection to the X server.

src_w	  Specifies the source window or None.

dest_w	  Specifies the destination window or None.

src_x
src_y
src_width
src_height
	  Specify a rectangle in the source window.

dest_x
dest_y	  Specify the x and y coordinates within the desti-
	  nation window.
|__

If dest_w is None, XWarpPointer moves the pointer by the
offsets (dest_x, dest_y) relative to the current position of
the pointer.  If dest_w is a window, XWarpPointer moves the
pointer to the offsets (dest_x, dest_y) relative to the ori-
gin of dest_w.	However, if src_w is a window, the move only
takes place if the window src_w contains the pointer and if
the specified rectangle of src_w contains the pointer.

The src_x and src_y coordinates are relative to the origin
of src_w.  If src_height is zero, it is replaced with the
current height of src_w minus src_y.  If src_width is zero,
it is replaced with the current width of src_w minus src_x.

There is seldom any reason for calling this function.  The
pointer should normally be left to the user.  If you do use



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this function, however, it generates events just as if the
user had instantaneously moved the pointer from one position
to another.  Note that you cannot use XWarpPointer to move
the pointer outside the confine_to window of an active
pointer grab.  An attempt to do so will only move the
pointer as far as the closest edge of the confine_to window.

XWarpPointer can generate a BadWindow error.

12.5.  Controlling Input Focus

Xlib provides functions that you can use to set and get the
input focus.  The input focus is a shared resource, and
cooperation among clients is required for correct interac-
tion.  See the Inter-Client Communication Conventions Manual
for input focus policy.


To set the input focus, use XSetInputFocus.
__
|
XSetInputFocus(display, focus, revert_to, time)
      Display *display;
      Window focus;
      int revert_to;
      Time time;


display   Specifies the connection to the X server.

focus	  Specifies the window, PointerRoot, or None.

revert_to Specifies where the input focus reverts to if the
	  window becomes not viewable.	You can pass Revert-
	  ToParent, RevertToPointerRoot, or RevertToNone.

time	  Specifies the time.  You can pass either a times-
	  tamp or CurrentTime.
|__

The XSetInputFocus function changes the input focus and the
last-focus-change time.  It has no effect if the specified
time is earlier than the current last-focus-change time or
is later than the current X server time.  Otherwise, the
last-focus-change time is set to the specified time (Cur-
rentTime is replaced by the current X server time).  XSet-
InputFocus causes the X server to generate FocusIn and Focu-
sOut events.

Depending on the focus argument, the following occurs:

o    If focus is None, all keyboard events are discarded
     until a new focus window is set, and the revert_to
     argument is ignored.



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o    If focus is a window, it becomes the keyboard's focus
     window.  If a generated keyboard event would normally
     be reported to this window or one of its inferiors, the
     event is reported as usual.  Otherwise, the event is
     reported relative to the focus window.

o    If focus is PointerRoot, the focus window is dynami-
     cally taken to be the root window of whatever screen
     the pointer is on at each keyboard event.	In this
     case, the revert_to argument is ignored.

The specified focus window must be viewable at the time
XSetInputFocus is called, or a BadMatch error results.	If
the focus window later becomes not viewable, the X server
evaluates the revert_to argument to determine the new focus
window as follows:

o    If revert_to is RevertToParent, the focus reverts to
     the parent (or the closest viewable ancestor), and the
     new revert_to value is taken to be RevertToNone.

o    If revert_to is RevertToPointerRoot or RevertToNone,
     the focus reverts to PointerRoot or None, respectively.
     When the focus reverts, the X server generates FocusIn
     and FocusOut events, but the last-focus-change time is
     not affected.

XSetInputFocus can generate BadMatch, BadValue, and BadWin-
dow errors.


To obtain the current input focus, use XGetInputFocus.
__
|
XGetInputFocus(display, focus_return, revert_to_return)
      Display *display;
      Window *focus_return;
      int *revert_to_return;


display   Specifies the connection to the X server.

focus_return
	  Returns the focus window, PointerRoot, or None.

revert_to_return
	  Returns the current focus state (RevertToParent,
	  RevertToPointerRoot, or RevertToNone).
|__

The XGetInputFocus function returns the focus window and the
current focus state.





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12.6.  Manipulating the Keyboard and Pointer Settings

Xlib provides functions that you can use to change the key-
board control, obtain a list of the auto-repeat keys, turn
keyboard auto-repeat on or off, ring the bell, set or obtain
the pointer button or keyboard mapping, and obtain a bit
vector for the keyboard.

This section discusses the user-preference options of bell,
key click, pointer behavior, and so on.  The default values
for many of these options are server dependent.  Not all
implementations will actually be able to control all of
these parameters.

The XChangeKeyboardControl function changes control of a
keyboard and operates on a XKeyboardControl structure:
__
|
/* Mask bits for ChangeKeyboardControl */

#define   KBKeyClickPercent	      (1L<<0)
#define   KBBellPercent 	      (1L<<1)
#define   KBBellPitch		      (1L<<2)
#define   KBBellDuration	      (1L<<3)
#define   KBLed 		      (1L<<4)
#define   KBLedMode		      (1L<<5)
#define   KBKey 		      (1L<<6)
#define   KBAutoRepeatMode	      (1L<<7)


/* Values */

typedef struct {
     int key_click_percent;
     int bell_percent;
     int bell_pitch;
     int bell_duration;
     int led;
     int led_mode;	 /* LedModeOn, LedModeOff */
     int key;
     int auto_repeat_mode;/* AutoRepeatModeOff, AutoRepeatModeOn,
			    AutoRepeatModeDefault */
} XKeyboardControl;

|__

The key_click_percent member sets the volume for key clicks
between 0 (off) and 100 (loud) inclusive, if possible.	A
setting of -1 restores the default.  Other negative values
generate a BadValue error.

The bell_percent sets the base volume for the bell between 0
(off) and 100 (loud) inclusive, if possible.  A setting of
-1 restores the default.  Other negative values generate a



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BadValue error.  The bell_pitch member sets the pitch (spec-
ified in Hz) of the bell, if possible.	A setting of -1
restores the default.  Other negative values generate a Bad-
Value error.  The bell_duration member sets the duration of
the bell specified in milliseconds, if possible.  A setting
of -1 restores the default.  Other negative values generate
a BadValue error.

If both the led_mode and led members are specified, the
state of that LED is changed, if possible.  The led_mode
member can be set to LedModeOn or LedModeOff.  If only
led_mode is specified, the state of all LEDs are changed, if
possible.  At most 32 LEDs numbered from one are supported.
No standard interpretation of LEDs is defined.	If led is
specified without led_mode, a BadMatch error results.

If both the auto_repeat_mode and key members are specified,
the auto_repeat_mode of that key is changed (according to
AutoRepeatModeOn, AutoRepeatModeOff, or AutoRepeatModeDe-
fault), if possible.  If only auto_repeat_mode is specified,
the global auto_repeat_mode for the entire keyboard is
changed, if possible, and does not affect the per-key set-
tings.	If a key is specified without an auto_repeat_mode, a
BadMatch error results.  Each key has an individual mode of
whether or not it should auto-repeat and a default setting
for the mode.  In addition, there is a global mode of
whether auto-repeat should be enabled or not and a default
setting for that mode.	When global mode is AutoRepeatMod-
eOn, keys should obey their individual auto-repeat modes.
When global mode is AutoRepeatModeOff, no keys should auto-
repeat.  An auto-repeating key generates alternating Key-
Press and KeyRelease events.  When a key is used as a modi-
fier, it is desirable for the key not to auto-repeat,
regardless of its auto-repeat setting.

A bell generator connected with the console but not directly
on a keyboard is treated as if it were part of the keyboard.
The order in which controls are verified and altered is
server-dependent.  If an error is generated, a subset of the
controls may have been altered.

















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__
|
XChangeKeyboardControl(display, value_mask, values)
      Display *display;
      unsigned long value_mask;
      XKeyboardControl *values;


display   Specifies the connection to the X server.

value_mask
	  Specifies which controls to change.  This mask is
	  the bitwise inclusive OR of the valid control mask
	  bits.

values	  Specifies one value for each bit set to 1 in the
	  mask.
|__

The XChangeKeyboardControl function controls the keyboard
characteristics defined by the XKeyboardControl structure.
The value_mask argument specifies which values are to be
changed.

XChangeKeyboardControl can generate BadMatch and BadValue
errors.


To obtain the current control values for the keyboard, use
XGetKeyboardControl.
__
|
XGetKeyboardControl(display, values_return)
      Display *display;
      XKeyboardState *values_return;


display   Specifies the connection to the X server.

values_return
	  Returns the current keyboard controls in the spec-
	  ified XKeyboardState structure.
|__

The XGetKeyboardControl function returns the current control
values for the keyboard to the XKeyboardState structure.












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__
|
typedef struct {
     int key_click_percent;
     int bell_percent;
     unsigned int bell_pitch, bell_duration;
     unsigned long led_mask;
     int global_auto_repeat;
     char auto_repeats[32];
} XKeyboardState;

|__

For the LEDs, the least significant bit of led_mask corre-
sponds to LED one, and each bit set to 1 in led_mask indi-
cates an LED that is lit.  The global_auto_repeat member can
be set to AutoRepeatModeOn or AutoRepeatModeOff.  The
auto_repeats member is a bit vector.  Each bit set to 1
indicates that auto-repeat is enabled for the corresponding
key.  The vector is represented as 32 bytes.  Byte N (from
0) contains the bits for keys 8N to 8N + 7 with the least
significant bit in the byte representing key 8N.


To turn on keyboard auto-repeat, use XAutoRepeatOn.
__
|
XAutoRepeatOn(display)
      Display *display;


display   Specifies the connection to the X server.
|__

The XAutoRepeatOn function turns on auto-repeat for the key-
board on the specified display.


To turn off keyboard auto-repeat, use XAutoRepeatOff.
__
|
XAutoRepeatOff(display)
      Display *display;


display   Specifies the connection to the X server.
|__

The XAutoRepeatOff function turns off auto-repeat for the
keyboard on the specified display.


To ring the bell, use XBell.





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__
|
XBell(display, percent)
      Display *display;
      int percent;


display   Specifies the connection to the X server.

percent   Specifies the volume for the bell, which can range
	  from -100 to 100 inclusive.
|__

The XBell function rings the bell on the keyboard on the
specified display, if possible.  The specified volume is
relative to the base volume for the keyboard.  If the value
for the percent argument is not in the range -100 to 100
inclusive, a BadValue error results.  The volume at which
the bell rings when the percent argument is nonnegative is:

     base - [(base * percent) / 100] + percent

The volume at which the bell rings when the percent argument
is negative is:

     base + [(base * percent) / 100]

To change the base volume of the bell, use XChangeKeyboard-
Control.

XBell can generate a BadValue error.


To obtain a bit vector that describes the state of the key-
board, use XQueryKeymap.
__
|
XQueryKeymap(display, keys_return)
      Display *display;
      char keys_return[32];


display   Specifies the connection to the X server.

keys_return
	  Returns an array of bytes that identifies which
	  keys are pressed down.  Each bit represents one
	  key of the keyboard.
|__

The XQueryKeymap function returns a bit vector for the logi-
cal state of the keyboard, where each bit set to 1 indicates
that the corresponding key is currently pressed down.  The
vector is represented as 32 bytes.  Byte N (from 0) contains
the bits for keys 8N to 8N + 7 with the least significant



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bit in the byte representing key 8N.

Note that the logical state of a device (as seen by client
applications) may lag the physical state if device event
processing is frozen.


To set the mapping of the pointer buttons, use XSetPoint-
erMapping.
__
|
int XSetPointerMapping(display, map, nmap)
      Display *display;
      unsigned char map[];
      int nmap;


display   Specifies the connection to the X server.

map	  Specifies the mapping list.

nmap	  Specifies the number of items in the mapping list.
|__

The XSetPointerMapping function sets the mapping of the
pointer.  If it succeeds, the X server generates a Mapping-
Notify event, and XSetPointerMapping returns MappingSuccess.
Element map[i] defines the logical button number for the
physical button i+1.  The length of the list must be the
same as XGetPointerMapping would return, or a BadValue error
results.  A zero element disables a button, and elements are
not restricted in value by the number of physical buttons.
However, no two elements can have the same nonzero value, or
a BadValue error results.  If any of the buttons to be
altered are logically in the down state, XSetPointerMapping
returns MappingBusy, and the mapping is not changed.

XSetPointerMapping can generate a BadValue error.


To get the pointer mapping, use XGetPointerMapping.
















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__
|
int XGetPointerMapping(display, map_return, nmap)
      Display *display;
      unsigned char map_return[];
      int nmap;


display   Specifies the connection to the X server.

map_return
	  Returns the mapping list.

nmap	  Specifies the number of items in the mapping list.
|__

The XGetPointerMapping function returns the current mapping
of the pointer.  Pointer buttons are numbered starting from
one.  XGetPointerMapping returns the number of physical but-
tons actually on the pointer.  The nominal mapping for a
pointer is map[i]=i+1.	The nmap argument specifies the
length of the array where the pointer mapping is returned,
and only the first nmap elements are returned in map_return.


To control the pointer's interactive feel, use XChangePoint-
erControl.































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__
|
XChangePointerControl(display, do_accel, do_threshold, accel_numerator,
			accel_denominator, threshold)
      Display *display;
      Bool do_accel, do_threshold;
      int accel_numerator, accel_denominator;
      int threshold;


display   Specifies the connection to the X server.

do_accel  Specifies a Boolean value that controls whether
	  the values for the accel_numerator or accel_denom-
	  inator are used.

do_threshold
	  Specifies a Boolean value that controls whether
	  the value for the threshold is used.

accel_numerator
	  Specifies the numerator for the acceleration mul-
	  tiplier.

accel_denominator
	  Specifies the denominator for the acceleration
	  multiplier.

threshold Specifies the acceleration threshold.
|__

The XChangePointerControl function defines how the pointing
device moves.  The acceleration, expressed as a fraction, is
a multiplier for movement.  For example, specifying 3/1
means the pointer moves three times as fast as normal.	The
fraction may be rounded arbitrarily by the X server.  Accel-
eration only takes effect if the pointer moves more than
threshold pixels at once and only applies to the amount
beyond the value in the threshold argument.  Setting a value
to -1 restores the default.  The values of the do_accel and
do_threshold arguments must be True for the pointer values
to be set, or the parameters are unchanged.  Negative values
(other than -1) generate a BadValue error, as does a zero
value for the accel_denominator argument.

XChangePointerControl can generate a BadValue error.


To get the current pointer parameters, use XGetPointerCon-
trol.








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__
|
XGetPointerControl(display, accel_numerator_return, accel_denominator_return,
		       threshold_return)
      Display *display;
      int *accel_numerator_return, *accel_denominator_return;
      int *threshold_return;


display   Specifies the connection to the X server.

accel_numerator_return
	  Returns the numerator for the acceleration multi-
	  plier.

accel_denominator_return
	  Returns the denominator for the acceleration mul-
	  tiplier.

threshold_return
	  Returns the acceleration threshold.
|__

The XGetPointerControl function returns the pointer's cur-
rent acceleration multiplier and acceleration threshold.

12.7.  Manipulating the Keyboard Encoding

A KeyCode represents a physical (or logical) key.  KeyCodes
lie in the inclusive range [8,255].  A KeyCode value carries
no intrinsic information, although server implementors may
attempt to encode geometry (for example, matrix) information
in some fashion so that it can be interpreted in a server-
dependent fashion.  The mapping between keys and KeyCodes
cannot be changed.

A KeySym is an encoding of a symbol on the cap of a key.
The set of defined KeySyms includes the ISO Latin character
sets (1-4), Katakana, Arabic, Cyrillic, Greek, Technical,
Special, Publishing, APL, Hebrew, Thai, Korean and a miscel-
lany of keys found on keyboards (Return, Help, Tab, and so
on).  To the extent possible, these sets are derived from
international standards.  In areas where no standards exist,
some of these sets are derived from Digital Equipment Corpo-
ration standards.  The list of defined symbols can be found
in <X11/keysymdef.h>.  Unfortunately, some C preprocessors
have limits on the number of defined symbols.  If you must
use KeySyms not in the Latin 1-4, Greek, and miscellaneous
classes, you may have to define a symbol for those sets.
Most applications usually only include <X11/keysym.h>, which
defines symbols for ISO Latin 1-4, Greek, and miscellaneous.

A list of KeySyms is associated with each KeyCode.  The list
is intended to convey the set of symbols on the correspond-
ing key.  If the list (ignoring trailing NoSymbol entries)



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is a single KeySym ``K'', then the list is treated as if it
were the list ``K NoSymbol K NoSymbol''.  If the list
(ignoring trailing NoSymbol entries) is a pair of KeySyms
``K1 K2'', then the list is treated as if it were the list
``K1 K2 K1 K2''.  If the list (ignoring trailing NoSymbol
entries) is a triple of KeySyms ``K1 K2 K3'', then the list
is treated as if it were the list ``K1 K2 K3 NoSymbol''.
When an explicit ``void'' element is desired in the list,
the value VoidSymbol can be used.

The first four elements of the list are split into two
groups of KeySyms.  Group 1 contains the first and second
KeySyms; Group 2 contains the third and fourth KeySyms.
Within each group, if the second element of the group is
NoSymbol, then the group should be treated as if the second
element were the same as the first element, except when the
first element is an alphabetic KeySym ``K'' for which both
lowercase and uppercase forms are defined.  In that case,
the group should be treated as if the first element were the
lowercase form of ``K'' and the second element were the
uppercase form of ``K''.

The standard rules for obtaining a KeySym from a KeyPress
event make use of only the Group 1 and Group 2 KeySyms; no
interpretation of other KeySyms in the list is given.  Which
group to use is determined by the modifier state.  Switching
between groups is controlled by the KeySym named MODE
SWITCH, by attaching that KeySym to some KeyCode and attach-
ing that KeyCode to any one of the modifiers Mod1 through
Mod5.  This modifier is called the group modifier.  For any
KeyCode, Group 1 is used when the group modifier is off, and
Group 2 is used when the group modifier is on.

The Lock modifier is interpreted as CapsLock when the KeySym
named XK_Caps_Lock is attached to some KeyCode and that Key-
Code is attached to the Lock modifier.	The Lock modifier is
interpreted as ShiftLock when the KeySym named XK_Shift_Lock
is attached to some KeyCode and that KeyCode is attached to
the Lock modifier.  If the Lock modifier could be inter-
preted as both CapsLock and ShiftLock, the CapsLock inter-
pretation is used.

The operation of keypad keys is controlled by the KeySym
named XK_Num_Lock, by attaching that KeySym to some KeyCode
and attaching that KeyCode to any one of the modifiers Mod1
through Mod5.  This modifier is called the numlock modifier.
The standard KeySyms with the prefix ``XK_KP_'' in their
name are called keypad KeySyms; these are KeySyms with
numeric value in the hexadecimal range 0xFF80 to 0xFFBD
inclusive.  In addition, vendor-specific KeySyms in the hex-
adecimal range 0x11000000 to 0x1100FFFF are also keypad
KeySyms.





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Within a group, the choice of KeySym is determined by apply-
ing the first rule that is satisfied from the following
list:

o    The numlock modifier is on and the second KeySym is a
     keypad KeySym.  In this case, if the Shift modifier is
     on, or if the Lock modifier is on and is interpreted as
     ShiftLock, then the first KeySym is used, otherwise the
     second KeySym is used.

o    The Shift and Lock modifiers are both off.  In this
     case, the first KeySym is used.

o    The Shift modifier is off, and the Lock modifier is on
     and is interpreted as CapsLock.  In this case, the
     first KeySym is used, but if that KeySym is lowercase
     alphabetic, then the corresponding uppercase KeySym is
     used instead.

o    The Shift modifier is on, and the Lock modifier is on
     and is interpreted as CapsLock.  In this case, the sec-
     ond KeySym is used, but if that KeySym is lowercase
     alphabetic, then the corresponding uppercase KeySym is
     used instead.

o    The Shift modifier is on, or the Lock modifier is on
     and is interpreted as ShiftLock, or both.	In this
     case, the second KeySym is used.

No spatial geometry of the symbols on the key is defined by
their order in the KeySym list, although a geometry might be
defined on a server-specific basis.  The X server does not
use the mapping between KeyCodes and KeySyms.  Rather, it
merely stores it for reading and writing by clients.


To obtain the legal KeyCodes for a display, use XDisplayKey-
codes.



















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__
|
XDisplayKeycodes(display, min_keycodes_return, max_keycodes_return)
	Display *display;
	int *min_keycodes_return, *max_keycodes_return;


display   Specifies the connection to the X server.

min_keycodes_return
	  Returns the minimum number of KeyCodes.

max_keycodes_return
	  Returns the maximum number of KeyCodes.
|__

The XDisplayKeycodes function returns the min-keycodes and
max-keycodes supported by the specified display.  The mini-
mum number of KeyCodes returned is never less than 8, and
the maximum number of KeyCodes returned is never greater
than 255.  Not all KeyCodes in this range are required to
have corresponding keys.


To obtain the symbols for the specified KeyCodes, use
XGetKeyboardMapping.
__
|
KeySym *XGetKeyboardMapping(display, first_keycode, keycode_count,
			    keysyms_per_keycode_return)
      Display *display;
      KeyCode first_keycode;
      int keycode_count;
      int *keysyms_per_keycode_return;


display   Specifies the connection to the X server.

first_keycode
	  Specifies the first KeyCode that is to be
	  returned.

keycode_count
	  Specifies the number of KeyCodes that are to be
	  returned.

keysyms_per_keycode_return
	  Returns the number of KeySyms per KeyCode.
|__

The XGetKeyboardMapping function returns the symbols for the
specified number of KeyCodes starting with first_keycode.
The value specified in first_keycode must be greater than or
equal to min_keycode as returned by XDisplayKeycodes, or a
BadValue error results.  In addition, the following



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expression must be less than or equal to max_keycode as
returned by XDisplayKeycodes:


     first_keycode + keycode_count - 1


If this is not the case, a BadValue error results.  The num-
ber of elements in the KeySyms list is:


     keycode_count * keysyms_per_keycode_return


KeySym number N, counting from zero, for KeyCode K has the
following index in the list, counting from zero:

     (K - first_code) * keysyms_per_code_return + N


The X server arbitrarily chooses the keysyms_per_key-
code_return value to be large enough to report all requested
symbols.  A special KeySym value of NoSymbol is used to fill
in unused elements for individual KeyCodes.  To free the
storage returned by XGetKeyboardMapping, use XFree.

XGetKeyboardMapping can generate a BadValue error.


To change the keyboard mapping, use XChangeKeyboardMapping.



























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__
|
XChangeKeyboardMapping(display, first_keycode, keysyms_per_keycode, keysyms, num_codes)
      Display *display;
      int first_keycode;
      int keysyms_per_keycode;
      KeySym *keysyms;
      int num_codes;


display   Specifies the connection to the X server.

first_keycode
	  Specifies the first KeyCode that is to be changed.

keysyms_per_keycode
	  Specifies the number of KeySyms per KeyCode.

keysyms   Specifies an array of KeySyms.

num_codes Specifies the number of KeyCodes that are to be
	  changed.
|__

The XChangeKeyboardMapping function defines the symbols for
the specified number of KeyCodes starting with first_key-
code.  The symbols for KeyCodes outside this range remain
unchanged.  The number of elements in keysyms must be:


     num_codes * keysyms_per_keycode


The specified first_keycode must be greater than or equal to
min_keycode returned by XDisplayKeycodes, or a BadValue
error results.	In addition, the following expression must
be less than or equal to max_keycode as returned by XDis-
playKeycodes, or a BadValue error results:


     first_keycode + num_codes - 1


KeySym number N, counting from zero, for KeyCode K has the
following index in keysyms, counting from zero:


     (K - first_keycode) * keysyms_per_keycode + N


The specified keysyms_per_keycode can be chosen arbitrarily
by the client to be large enough to hold all desired sym-
bols.  A special KeySym value of NoSymbol should be used to
fill in unused elements for individual KeyCodes.  It is
legal for NoSymbol to appear in nontrailing positions of the



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effective list for a KeyCode.  XChangeKeyboardMapping gener-
ates a MappingNotify event.

There is no requirement that the X server interpret this
mapping.  It is merely stored for reading and writing by
clients.

XChangeKeyboardMapping can generate BadAlloc and BadValue
errors.

The next six functions make use of the XModifierKeymap data
structure, which contains:

__
|
typedef struct {
     int max_keypermod;  /* This server's max number of keys per modifier */
     KeyCode *modifiermap;/* An 8 by max_keypermod array of the modifiers */
} XModifierKeymap;

|__

To create an XModifierKeymap structure, use XNewModifiermap.
__
|
XModifierKeymap *XNewModifiermap(max_keys_per_mod)
	int max_keys_per_mod;


max_keys_per_mod
	  Specifies the number of KeyCode entries preallo-
	  cated to the modifiers in the map.
|__

The XNewModifiermap function returns a pointer to XModi-
fierKeymap structure for later use.


To add a new entry to an XModifierKeymap structure, use XIn-
sertModifiermapEntry.

















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__
|
XModifierKeymap *XInsertModifiermapEntry(modmap, keycode_entry, modifier)
     XModifierKeymap *modmap;
     KeyCode keycode_entry;
     int modifier;


modmap	  Specifies the XModifierKeymap structure.

keycode_entry
	  Specifies the KeyCode.

modifier  Specifies the modifier.
|__

The XInsertModifiermapEntry function adds the specified Key-
Code to the set that controls the specified modifier and
returns the resulting XModifierKeymap structure (expanded as
needed).


To delete an entry from an XModifierKeymap structure, use
XDeleteModifiermapEntry.
__
|
XModifierKeymap *XDeleteModifiermapEntry(modmap, keycode_entry, modifier)
     XModifierKeymap *modmap;
     KeyCode keycode_entry;
     int modifier;


modmap	  Specifies the XModifierKeymap structure.

keycode_entry
	  Specifies the KeyCode.

modifier  Specifies the modifier.
|__

The XDeleteModifiermapEntry function deletes the specified
KeyCode from the set that controls the specified modifier
and returns a pointer to the resulting XModifierKeymap
structure.


To destroy an XModifierKeymap structure, use XFreeModi-
fiermap.










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__
|
XFreeModifiermap(modmap)
	XModifierKeymap *modmap;


modmap	  Specifies the XModifierKeymap structure.
|__

The XFreeModifiermap function frees the specified XModi-
fierKeymap structure.


To set the KeyCodes to be used as modifiers, use XSetModi-
fierMapping.
__
|
int XSetModifierMapping(display, modmap)
	Display *display;
	XModifierKeymap *modmap;


display   Specifies the connection to the X server.

modmap	  Specifies the XModifierKeymap structure.
|__

The XSetModifierMapping function specifies the KeyCodes of
the keys (if any) that are to be used as modifiers.  If it
succeeds, the X server generates a MappingNotify event, and
XSetModifierMapping returns MappingSuccess.  X permits at
most 8 modifier keys.  If more than 8 are specified in the
XModifierKeymap structure, a BadLength error results.

The modifiermap member of the XModifierKeymap structure con-
tains 8 sets of max_keypermod KeyCodes, one for each modi-
fier in the order Shift, Lock, Control, Mod1, Mod2, Mod3,
Mod4, and Mod5.  Only nonzero KeyCodes have meaning in each
set, and zero KeyCodes are ignored.  In addition, all of the
nonzero KeyCodes must be in the range specified by min_key-
code and max_keycode in the Display structure, or a BadValue
error results.

An X server can impose restrictions on how modifiers can be
changed, for example, if certain keys do not generate up
transitions in hardware, if auto-repeat cannot be disabled
on certain keys, or if multiple modifier keys are not sup-
ported.  If some such restriction is violated, the status
reply is MappingFailed, and none of the modifiers are
changed.  If the new KeyCodes specified for a modifier dif-
fer from those currently defined and any (current or new)
keys for that modifier are in the logically down state,
XSetModifierMapping returns MappingBusy, and none of the
modifiers is changed.




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XSetModifierMapping can generate BadAlloc and BadValue
errors.


To obtain the KeyCodes used as modifiers, use XGetModi-
fierMapping.
__
|
XModifierKeymap *XGetModifierMapping(display)
      Display *display;



display   Specifies the connection to the X server.
|__

The XGetModifierMapping function returns a pointer to a
newly created XModifierKeymap structure that contains the
keys being used as modifiers.  The structure should be freed
after use by calling XFreeModifiermap.	If only zero values
appear in the set for any modifier, that modifier is dis-
abled.



































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			 Chapter 13

	Locales and Internationalized Text Functions



An internationalized application is one that is adaptable to
the requirements of different native languages, local cus-
toms, and character string encodings.  The process of adapt-
ing the operation to a particular native language, local
custom, or string encoding is called localization.  A goal
of internationalization is to permit localization without
program source modifications or recompilation.

As one of the localization mechanisms, Xlib provides an X
Input Method (XIM) functional interface for international-
ized text input and an X Output Method (XOM) functional
interface for internationalized text output.

Internationalization in X is based on the concept of a
locale.  A locale defines the localized behavior of a pro-
gram at run time.  Locales affect Xlib in its:

o    Encoding and processing of input method text

o    Encoding of resource files and values

o    Encoding and imaging of text strings

o    Encoding and decoding for inter-client text communica-
     tion

Characters from various languages are represented in a com-
puter using an encoding.  Different languages have different
encodings, and there are even different encodings for the
same characters in the same language.

This chapter defines support for localized text imaging and
text input and describes the locale mechanism that controls
all locale-dependent Xlib functions.  Sets of functions are
provided for multibyte (char *) text as well as wide charac-
ter (wchar_t) text in the form supported by the host C lan-
guage environment.  The multibyte and wide character func-
tions are equivalent except for the form of the text argu-
ment.

The Xlib internationalization functions are not meant to
provide support for multilingual applications (mixing multi-
ple languages within a single piece of text), but they make
it possible to implement applications that work in limited
fashion with more than one language in independent contexts.




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The remainder of this chapter discusses:

o    X locale management

o    Locale and modifier dependencies

o    Variable argument lists

o    Output methods

o    Input methods

o    String constants

13.1.  X Locale Management

X supports one or more of the locales defined by the host
environment.  On implementations that conform to the ANSI C
library, the locale announcement method is setlocale.  This
function configures the locale operation of both the host C
library and Xlib.  The operation of Xlib is governed by the
LC_CTYPE category; this is called the current locale.  An
implementation is permitted to provide implementation-depen-
dent mechanisms for announcing the locale in addition to
setlocale.

On implementations that do not conform to the ANSI C
library, the locale announcement method is Xlib implementa-
tion-dependent.

The mechanism by which the semantic operation of Xlib is
defined for a specific locale is implementation-dependent.


X is not required to support all the locales supported by
the host.  To determine if the current locale is supported
by X, use XSupportsLocale.
__
|
Bool XSupportsLocale()

|__

The XSupportsLocale function returns True if Xlib functions
are capable of operating under the current locale.  If it
returns False, Xlib locale-dependent functions for which the
XLocaleNotSupported return status is defined will return
XLocaleNotSupported.  Other Xlib locale-dependent routines
will operate in the ``C'' locale.

The client is responsible for selecting its locale and X
modifiers.  Clients should provide a means for the user to
override the clients' locale selection at client invocation.
Most single-display X clients operate in a single locale for



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both X and the host processing environment.  They will con-
figure the locale by calling three functions: the host
locale configuration function, XSupportsLocale, and XSetLo-
caleModifiers.

The semantics of certain categories of X internationaliza-
tion capabilities can be configured by setting modifiers.
Modifiers are named by implementation-dependent and locale-
specific strings.  The only standard use for this capability
at present is selecting one of several styles of keyboard
input method.


To configure Xlib locale modifiers for the current locale,
use XSetLocaleModifiers.
__
|
char *XSetLocaleModifiers(modifier_list)
      char *modifier_list;


modifier_list
	  Specifies the modifiers.
|__

The XSetLocaleModifiers function sets the X modifiers for
the current locale setting.  The modifier_list argument is a
null-terminated string of the form ``{@category=value}'',
that is, having zero or more concatenated ``@cate-
gory=value'' entries, where category is a category name and
value is the (possibly empty) setting for that category.
The values are encoded in the current locale.  Category
names are restricted to the POSIX Portable Filename Charac-
ter Set.

The local host X locale modifiers announcer (on POSIX-com-
pliant systems, the XMODIFIERS environment variable) is
appended to the modifier_list to provide default values on
the local host.  If a given category appears more than once
in the list, the first setting in the list is used.  If a
given category is not included in the full modifier list,
the category is set to an implementation-dependent default
for the current locale.  An empty value for a category
explicitly specifies the implementation-dependent default.

If the function is successful, it returns a pointer to a
string.  The contents of the string are such that a subse-
quent call with that string (in the same locale) will
restore the modifiers to the same settings.  If modi-
fier_list is a NULL pointer, XSetLocaleModifiers also
returns a pointer to such a string, and the current locale
modifiers are not changed.





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If invalid values are given for one or more modifier cate-
gories supported by the locale, a NULL pointer is returned,
and none of the current modifiers are changed.

At program startup, the modifiers that are in effect are
unspecified until the first successful call to set them.
Whenever the locale is changed, the modifiers that are in
effect become unspecified until the next successful call to
set them.  Clients should always call XSetLocaleModifiers
with a non-NULL modifier_list after setting the locale
before they call any locale-dependent Xlib routine.

The only standard modifier category currently defined is
``im'', which identifies the desired input method.  The val-
ues for input method are not standardized.  A single locale
may use multiple input methods, switching input method under
user control.  The modifier may specify the initial input
method in effect or an ordered list of input methods.  Mul-
tiple input methods may be specified in a single im value
string in an implementation-dependent manner.

The returned modifiers string is owned by Xlib and should
not be modified or freed by the client.  It may be freed by
Xlib after the current locale or modifiers are changed.
Until freed, it will not be modified by Xlib.

The recommended procedure for clients initializing their
locale and modifiers is to obtain locale and modifier
announcers separately from one of the following prioritized
sources:

o    A command line option

o    A resource

o    The empty string ("")

The first of these that is defined should be used.  Note
that when a locale command line option or locale resource is
defined, the effect should be to set all categories to the
specified locale, overriding any category-specific settings
in the local host environment.

13.2.  Locale and Modifier Dependencies

The internationalized Xlib functions operate in the current
locale configured by the host environment and X locale modi-
fiers set by XSetLocaleModifiers or in the locale and modi-
fiers configured at the time some object supplied to the
function was created.  For each locale-dependent function,
the following table describes the locale (and modifiers)
dependency:





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--------------------------------------------------------------------------
Locale from    Affects the Function	      In
--------------------------------------------------------------------------
	       Locale Query/Configuration:
setlocale      XSupportsLocale		      Locale queried
	       XSetLocaleModifiers	      Locale modified

	       Resources:
setlocale      XrmGetFileDatabase	      Locale of XrmDatabase
	       XrmGetStringDatabase
XrmDatabase    XrmPutFileDatabase	      Locale of XrmDatabase
	       XrmLocaleOfDatabase

	       Setting Standard Properties:
setlocale      XmbSetWMProperties	      Encoding of sup-
					      plied/returned
					      text (some WM_ property
					      text in environment locale)
	       Xutf8SetWMProperties
setlocale      XmbTextPropertyToTextList      Encoding of sup-
					      plied/returned text
	       XwcTextPropertyToTextList
	       Xutf8TextPropertyToTextList
	       XmbTextListToTextProperty
	       XwcTextListToTextProperty
	       Xutf8TextListToTextProperty

	       Text Input:
setlocale      XOpenIM			      XIM input method selection
	       XRegisterIMInstantiateCall-    XIM selection
	       back
	       XUnregisterIMInstantiate-      XIM selection
	       Callback
XIM	       XCreateIC		      XIC input method configura-
					      tion
	       XLocaleOfIM, and so on	      Queried locale
XIC	       XmbLookupString		      Keyboard layout
	       XwcLookupString		      Encoding of returned text
	       Xutf8LookupString

	       Text Drawing:
setlocale      XOpenOM			      XOM output method selection
	       XCreateFontSet		      Charsets of fonts in
					      XFontSet
XOM	       XCreateOC		      XOC output method configu-
					      ration
	       XLocaleOfOM, and so on	      Queried locale
XFontSet       XmbDrawText,		      Locale of supplied text
	       XwcDrawText, and so on	      Locale of supplied text
	       Xutf8DrawText, and so on       Locale-dependent metrics
	       XExtentsOfFontSet, and so on   Locale-dependent metrics
	       XmbTextExtents,
	       XwcTextExtents,




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--------------------------------------------------------------------------
Locale from    Affects the Function	      In
--------------------------------------------------------------------------
	       Xutf8TextExtents, and so on

	       Xlib Errors:
setlocale      XGetErrorDatabaseText	      Locale of error message
	       XGetErrorText
--------------------------------------------------------------------------


Clients may assume that a locale-encoded text string
returned by an X function can be passed to a C library rou-
tine, or vice versa, if the locale is the same at the two
calls.

All text strings processed by internationalized Xlib func-
tions are assumed to begin in the initial state of the
encoding of the locale, if the encoding is state-dependent.

All Xlib functions behave as if they do not change the cur-
rent locale or X modifier setting.  (This means that if they
do change locale or call XSetLocaleModifiers with a non-NULL
argument, they must save and restore the current state on
entry and exit.)  Also, Xlib functions on implementations
that conform to the ANSI C library do not alter the global
state associated with the ANSI C functions mblen, mbtowc,
wctomb, and strtok.

13.3.  Variable Argument Lists

Various functions in this chapter have arguments that con-
form to the ANSI C variable argument list calling conven-
tion.  Each function denoted with an argument of the form
``...'' takes a variable-length list of name and value
pairs, where each name is a string and each value is of type
XPointer.  A name argument that is NULL identifies the end
of the list.

A variable-length argument list may contain a nested list.
If the name XNVaNestedList is specified in place of an argu-
ment name, then the following value is interpreted as an
XVaNestedList value that specifies a list of values logi-
cally inserted into the original list at the point of decla-
ration.  A NULL identifies the end of a nested list.


To allocate a nested variable argument list dynamically, use
XVaCreateNestedList.








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__
|
typedef void * XVaNestedList;

XVaNestedList XVaCreateNestedList(dummy, ...)
      int dummy;


dummy	  Specifies an unused argument (required by ANSI C).

...	  Specifies the variable length argument list.
|__

The XVaCreateNestedList function allocates memory and copies
its arguments into a single list pointer, which may be used
as a value for arguments requiring a list value.  Any
entries are copied as specified.  Data passed by reference
is not copied; the caller must ensure data remains valid for
the lifetime of the nested list.  The list should be freed
using XFree when it is no longer needed.

13.4.  Output Methods

This section provides discussions of the following X Output
Method (XOM) topics:

o    Output method overview

o    Output method functions

o    Output method values

o    Output context functions

o    Output context values

o    Creating and freeing a font set

o    Obtaining font set metrics

o    Drawing text using font sets

13.4.1.  Output Method Overview

Locale-dependent text may include one or more text compo-
nents, each of which may require different fonts and charac-
ter set encodings.  In some languages, each component might
have a different drawing direction, and some components
might contain context-dependent characters that change shape
based on relationships with neighboring characters.

When drawing such locale-dependent text, some locale-spe-
cific knowledge is required; for example, what fonts are
required to draw the text, how the text can be separated
into components, and which fonts are selected to draw each



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component.  Further, when bidirectional text must be drawn,
the internal representation order of the text must be
changed into the visual representation order to be drawn.

An X Output Method provides a functional interface so that
clients do not have to deal directly with such locale-depen-
dent details.  Output methods provide the following capabil-
ities:

o    Creating a set of fonts required to draw locale-depen-
     dent text.

o    Drawing locale-dependent text with a font set without
     the caller needing to be aware of locale dependencies.

o    Obtaining the escapement and extents in pixels of
     locale-dependent text.

o    Determining if bidirectional or context-dependent draw-
     ing is required in a specific locale with a specific
     font set.

Two different abstractions are used in the representation of
the output method for clients.

The abstraction used to communicate with an output method is
an opaque data structure represented by the XOM data type.
The abstraction for representing the state of a particular
output thread is called an output context.  The Xlib repre-
sentation of an output context is an XOC, which is compati-
ble with XFontSet in terms of its functional interface, but
is a broader, more generalized abstraction.

13.4.2.  Output Method Functions

To open an output method, use XOpenOM.





















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__
|
XOM XOpenOM(display, db, res_name, res_class)
      Display *display;
      XrmDatabase db;
      char *res_name;
      char *res_class;


display   Specifies the connection to the X server.

db	  Specifies a pointer to the resource database.

res_name  Specifies the full resource name of the applica-
	  tion.

res_class Specifies the full class name of the application.
|__

The XOpenOM function opens an output method matching the
current locale and modifiers specification.  The current
locale and modifiers are bound to the output method when
XOpenOM is called.  The locale associated with an output
method cannot be changed.

The specific output method to which this call will be routed
is identified on the basis of the current locale and modi-
fiers.	XOpenOM will identify a default output method corre-
sponding to the current locale.  That default can be modi-
fied using XSetLocaleModifiers to set the output method mod-
ifier.

The db argument is the resource database to be used by the
output method for looking up resources that are private to
the output method.  It is not intended that this database be
used to look up values that can be set as OC values in an
output context.  If db is NULL, no database is passed to the
output method.

The res_name and res_class arguments specify the resource
name and class of the application.  They are intended to be
used as prefixes by the output method when looking up
resources that are common to all output contexts that may be
created for this output method.  The characters used for
resource names and classes must be in the X Portable Charac-
ter Set.  The resources looked up are not fully specified if
res_name or res_class is NULL.

The res_name and res_class arguments are not assumed to
exist beyond the call to XOpenOM.  The specified resource
database is assumed to exist for the lifetime of the output
method.

XOpenOM returns NULL if no output method could be opened.




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To close an output method, use XCloseOM.
__
|
Status XCloseOM(om)
      XOM om;


om	  Specifies the output method.
|__

The XCloseOM function closes the specified output method.


To set output method attributes, use XSetOMValues.
__
|
char * XSetOMValues(om, ...)
      XOM om;


om	  Specifies the output method.

...	  Specifies the variable-length argument list to set
	  XOM values.
|__

The XSetOMValues function presents a variable argument list
programming interface for setting properties or features of
the specified output method.  This function returns NULL if
it succeeds; otherwise, it returns the name of the first
argument that could not be set.  Xlib does not attempt to
set arguments from the supplied list that follow the failed
argument; all arguments in the list preceding the failed
argument have been set correctly.

No standard arguments are currently defined by Xlib.


To query an output method, use XGetOMValues.
__
|
char * XGetOMValues(om, ...)
      XOM om;


om	  Specifies the output method.

...	  Specifies the variable-length argument list to get
	  XOM values.
|__

The XGetOMValues function presents a variable argument list
programming interface for querying properties or features of
the specified output method.  This function returns NULL if



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it succeeds; otherwise, it returns the name of the first
argument that could not be obtained.

To obtain the display associated with an output method, use
XDisplayOfOM.
__
|
Display * XDisplayOfOM(om)
     XOM om;


om	  Specifies the output method.
|__

The XDisplayOfOM function returns the display associated
with the specified output method.


To get the locale associated with an output method, use XLo-
caleOfOM.
__
|
char * XLocaleOfOM(om)
      XOM om;


om	  Specifies the output method.
|__

The XLocaleOfOM returns the locale associated with the spec-
ified output method.

13.4.3.  X Output Method Values

The following table describes how XOM values are interpreted
by an output method.  The first column lists the XOM values.
The second column indicates how each of the XOM values are
treated by a particular output style.


The following key applies to this table.

-------------------------------------------------------------
Key	     Explanation
-------------------------------------------------------------
G	     This value may be read using XGetOMValues.
-------------------------------------------------------------










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-----------------------------
XOM Value		 Key
-----------------------------
XNRequiredCharSet	  G
XNQueryOrientation	  G
XNDirectionalDepen-	  G
dentDrawing
XNContextualDrawing	  G
-----------------------------



13.4.3.1.  Required Char Set

The XNRequiredCharSet argument returns the list of charsets
that are required for loading the fonts needed for the
locale.  The value of the argument is a pointer to a struc-
ture of type XOMCharSetList.

The XOMCharSetList structure is defined as follows:
__
|

typedef struct {
     int charset_count;
     char **charset_list;
} XOMCharSetList;

|__

The charset_list member is a list of one or more null-termi-
nated charset names, and the charset_count member is the
number of charset names.

The required charset list is owned by Xlib and should not be
modified or freed by the client.  It will be freed by a call
to XCloseOM with the associated XOM.  Until freed, its con-
tents will not be modified by Xlib.


13.4.3.2.  Query Orientation

The XNQueryOrientation argument returns the global orienta-
tion of text when drawn.  Other than XOMOrientation_LTR_TTB,
the set of orientations supported is locale-dependent.	The
value of the argument is a pointer to a structure of type
XOMOrientation.  Clients are responsible for freeing the
XOMOrientation structure by using XFree; this also frees the
contents of the structure.








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__
|
typedef struct {
     int num_orientation;
     XOrientation *orientation;/* Input Text description */
} XOMOrientation;

typedef enum {
     XOMOrientation_LTR_TTB,
     XOMOrientation_RTL_TTB,
     XOMOrientation_TTB_LTR,
     XOMOrientation_TTB_RTL,
     XOMOrientation_Context
} XOrientation;

|__

The possible value for XOrientation may be:

o    XOMOrientation_LTR_TTB left-to-right, top-to-bottom
     global orientation

o    XOMOrientation_RTL_TTB right-to-left, top-to-bottom
     global orientation

o    XOMOrientation_TTB_LTR top-to-bottom, left-to-right
     global orientation

o    XOMOrientation_TTB_RTL top-to-bottom, right-to-left
     global orientation

o    XOMOrientation_Context contextual global orientation


13.4.3.3.  Directional Dependent Drawing

The XNDirectionalDependentDrawing argument indicates whether
the text rendering functions implement implicit handling of
directional text.  If this value is True, the output method
has knowledge of directional dependencies and reorders text
as necessary when rendering text.  If this value is False,
the output method does not implement any directional text
handling, and all character directions are assumed to be
left-to-right.

Regardless of the rendering order of characters, the origins
of all characters are on the primary draw direction side of
the drawing origin.

This OM value presents functionality identical to the XDi-
rectionalDependentDrawing function.







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13.4.3.4.  Context Dependent Drawing

The XNContextualDrawing argument indicates whether the text
rendering functions implement implicit context-dependent
drawing.  If this value is True, the output method has
knowledge of context dependencies and performs character
shape editing, combining glyphs to present a single charac-
ter as necessary.  The actual shape editing is dependent on
the locale implementation and the font set used.

This OM value presents functionality identical to the XCon-
textualDrawing function.

13.4.4.  Output Context Functions

An output context is an abstraction that contains both the
data required by an output method and the information
required to display that data.	There can be multiple output
contexts for one output method.  The programming interfaces
for creating, reading, or modifying an output context use a
variable argument list.  The name elements of the argument
lists are referred to as XOC values.  It is intended that
output methods be controlled by these XOC values.  As new
XOC values are created, they should be registered with the X
Consortium.  An XOC can be used anywhere an XFontSet can be
used, and vice versa; XFontSet is retained for compatibility
with previous releases.  The concepts of output methods and
output contexts include broader, more generalized abstrac-
tion than font set, supporting complex and more intelligent
text display, and dealing not only with multiple fonts but
also with context dependencies.  However, XFontSet is widely
used in several interfaces, so XOC is defined as an upward
compatible type of XFontSet.


To create an output context, use XCreateOC.
__
|
XOC XCreateOC(om, ...)
      XOM om;


om	  Specifies the output method.

...	  Specifies the variable-length argument list to set
	  XOC values.
|__

The XCreateOC function creates an output context within the
specified output method.

The base font names argument is mandatory at creation time,
and the output context will not be created unless it is pro-
vided.	All other output context values can be set later.



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XCreateOC returns NULL if no output context could be cre-
ated.  NULL can be returned for any of the following rea-
sons:

o    A required argument was not set.

o    A read-only argument was set.

o    An argument name is not recognized.

o    The output method encountered an output method imple-
     mentation-dependent error.

XCreateOC can generate a BadAtom error.


To destroy an output context, use XDestroyOC.
__
|
void XDestroyOC(oc)
      XOC oc;


oc	  Specifies the output context.
|__

The XDestroyOC function destroys the specified output con-
text.


To get the output method associated with an output context,
use XOMOfOC.
__
|
XOM XOMOfOC(oc)
      XOC oc;


oc	  Specifies the output context.
|__

The XOMOfOC function returns the output method associated
with the specified output context.


Xlib provides two functions for setting and reading output
context values, respectively, XSetOCValues and XGetOCValues.
Both functions have a variable-length argument list.  In
that argument list, any XOC value's name must be denoted
with a character string using the X Portable Character Set.


To set XOC values, use XSetOCValues.




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__
|
char * XSetOCValues(oc, ...)
      XOC oc;


oc	  Specifies the output context.

...	  Specifies the variable-length argument list to set
	  XOC values.
|__

The XSetOCValues function returns NULL if no error occurred;
otherwise, it returns the name of the first argument that
could not be set.  An argument might not be set for any of
the following reasons:

o    The argument is read-only.

o    The argument name is not recognized.

o    An implementation-dependent error occurs.

Each value to be set must be an appropriate datum, matching
the data type imposed by the semantics of the argument.

XSetOCValues can generate a BadAtom error.


To obtain XOC values, use XGetOCValues.
__
|
char * XGetOCValues(oc, ...)
      XOC oc;


oc	  Specifies the output context.

...	  Specifies the variable-length argument list to get
	  XOC values.
|__

The XGetOCValues function returns NULL if no error occurred;
otherwise, it returns the name of the first argument that
could not be obtained.	An argument might not be obtained
for any of the following reasons:

o    The argument name is not recognized.

o    An implementation-dependent error occurs.

Each argument value following a name must point to a loca-
tion where the value is to be stored.





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13.4.5.  Output Context Values

The following table describes how XOC values are interpreted
by an output method.  The first column lists the XOC values.
The second column indicates the alternative interfaces that
function identically and are provided for compatibility with
previous releases.  The third column indicates how each of
the XOC values is treated.

The following keys apply to this table.

-------------------------------------------------------------
Key	     Explanation
-------------------------------------------------------------
C	     This value must be set with XCreateOC.
D	     This value may be set using XCreateOC.  If it
	     is not set,
	     a default is provided.
G	     This value may be read using XGetOCValues.
S	     This value must be set using XSetOCValues.
-------------------------------------------------------------



-----------------------------------------------
XOC Value	 Alternative Interface	  Key
-----------------------------------------------
BaseFontName	    XCreateFontSet	  C-G
MissingCharSet	    XCreateFontSet	   G
DefaultString	    XCreateFontSet	   G
Orientation		   -		 D-S-G
ResourceName		   -		  S-G
ResourceClass		   -		  S-G
FontInfo	    XFontsOfFontSet	   G
OMAutomatic		   -		   G
-----------------------------------------------



13.4.5.1.  Base Font Name

The XNBaseFontName argument is a list of base font names
that Xlib uses to load the fonts needed for the locale.  The
base font names are a comma-separated list.  The string is
null-terminated and is assumed to be in the Host Portable
Character Encoding; otherwise, the result is implementation-
dependent.  White space immediately on either side of a sep-
arating comma is ignored.

Use of XLFD font names permits Xlib to obtain the fonts
needed for a variety of locales from a single locale-inde-
pendent base font name.  The single base font name should
name a family of fonts whose members are encoded in the var-
ious charsets needed by the locales of interest.



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An XLFD base font name can explicitly name a charset needed
for the locale.  This allows the user to specify an exact
font for use with a charset required by a locale, fully con-
trolling the font selection.

If a base font name is not an XLFD name, Xlib will attempt
to obtain an XLFD name from the font properties for the
font.  If Xlib is successful, the XGetOCValues function will
return this XLFD name instead of the client-supplied name.

This argument must be set at creation time and cannot be
changed.  If no fonts exist for any of the required
charsets, or if the locale definition in Xlib requires that
a font exist for a particular charset and a font is not
found for that charset, XCreateOC returns NULL.

When querying for the XNBaseFontName XOC value, XGetOCValues
returns a null-terminated string identifying the base font
names that Xlib used to load the fonts needed for the
locale.  This string is owned by Xlib and should not be mod-
ified or freed by the client.  The string will be freed by a
call to XDestroyOC with the associated XOC.  Until freed,
the string contents will not be modified by Xlib.

13.4.5.2.  Missing CharSet

The XNMissingCharSet argument returns the list of required
charsets that are missing from the font set.  The value of
the argument is a pointer to a structure of type XOM-
CharSetList.

If fonts exist for all of the charsets required by the cur-
rent locale, charset_list is set to NULL and charset_count
is set to zero.  If no fonts exist for one or more of the
required charsets, charset_list is set to a list of one or
more null-terminated charset names for which no fonts exist,
and charset_count is set to the number of missing charsets.
The charsets are from the list of the required charsets for
the encoding of the locale and do not include any charsets
to which Xlib may be able to remap a required charset.

The missing charset list is owned by Xlib and should not be
modified or freed by the client.  It will be freed by a call
to XDestroyOC with the associated XOC.	Until freed, its
contents will not be modified by Xlib.

13.4.5.3.  Default String

When a drawing or measuring function is called with an XOC
that has missing charsets, some characters in the locale
will not be drawable.  The XNDefaultString argument returns
a pointer to a string that represents the glyphs that are
drawn with this XOC when the charsets of the available fonts
do not include all glyphs required to draw a character.  The



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string does not necessarily consist of valid characters in
the current locale and is not necessarily drawn with the
fonts loaded for the font set, but the client can draw or
measure the default glyphs by including this string in a
string being drawn or measured with the XOC.

If the XNDefaultString argument returned the empty string
(""), no glyphs are drawn and the escapement is zero.  The
returned string is null-terminated.  It is owned by Xlib and
should not be modified or freed by the client.	It will be
freed by a call to XDestroyOC with the associated XOC.
Until freed, its contents will not be modified by Xlib.

13.4.5.4.  Orientation

The XNOrientation argument specifies the current orientation
of text when drawn.  The value of this argument is one of
the values returned by the XGetOMValues function with the
XNQueryOrientation argument specified in the XOrientation
list.  The value of the argument is of type XOrientation.
When XNOrientation is queried, the value specifies the cur-
rent orientation.  When XNOrientation is set, a value is
used to set the current orientation.

When XOMOrientation_Context is set, the text orientation of
the text is determined according to an implementation-
defined method (for example, ISO 6429 control sequences),
and the initial text orientation for locale-dependent Xlib
functions is assumed to be XOMOrientation_LTR_TTB.

The XNOrientation value does not change the prime drawing
direction for Xlib drawing functions.

13.4.5.5.  Resource Name and Class

The XNResourceName and XNResourceClass arguments are strings
that specify the full name and class used by the client to
obtain resources for the display of the output context.
These values should be used as prefixes for name and class
when looking up resources that may vary according to the
output context.  If these values are not set, the resources
will not be fully specified.

It is not intended that values that can be set as XOM values
be set as resources.

When querying for the XNResourceName or XNResourceClass XOC
value, XGetOCValues returns a null-terminated string.  This
string is owned by Xlib and should not be modified or freed
by the client.	The string will be freed by a call to XDe-
stroyOC with the associated XOC or when the associated value
is changed via XSetOCValues.  Until freed, the string con-
tents will not be modified by Xlib.




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13.4.5.6.  Font Info

The XNFontInfo argument specifies a list of one or more
XFontStruct structures and font names for the fonts used for
drawing by the given output context.  The value of the argu-
ment is a pointer to a structure of type XOMFontInfo.

__
|
typedef struct {
     int num_font;
     XFontStruct **font_struct_list;
     char **font_name_list;
} XOMFontInfo;

|__

A list of pointers to the XFontStruct structures is returned
to font_struct_list.  A list of pointers to null-terminated,
fully-specified font name strings in the locale of the out-
put context is returned to font_name_list.  The
font_name_list order corresponds to the font_struct_list
order.	The number of XFontStruct structures and font names
is returned to num_font.

Because it is not guaranteed that a given character will be
imaged using a single font glyph, there is no provision for
mapping a character or default string to the font proper-
ties, font ID, or direction hint for the font for the char-
acter.	The client may access the XFontStruct list to obtain
these values for all the fonts currently in use.

Xlib does not guarantee that fonts are loaded from the
server at the creation of an XOC.  Xlib may choose to cache
font data, loading it only as needed to draw text or compute
text dimensions.  Therefore, existence of the per_char met-
rics in the XFontStruct structures in the XFontStructSet is
undefined.  Also, note that all properties in the
XFontStruct structures are in the STRING encoding.

The client must not free the XOMFontInfo struct itself; it
will be freed when the XOC is closed.

13.4.5.7.  OM Automatic

The XNOMAutomatic argument returns whether the associated
output context was created by XCreateFontSet or not.
Because the XFreeFontSet function not only destroys the out-
put context but also closes the implicit output method asso-
ciated with it, XFreeFontSet should be used with any output
context created by XCreateFontSet.  However, it is possible
that a client does not know how the output context was cre-
ated.  Before a client destroys the output context, it can
query whether XNOMAutomatic is set to determine whether



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XFreeFontSet or XDestroyOC should be used to destroy the
output context.

13.4.6.  Creating and Freeing a Font Set

Xlib international text drawing is done using a set of one
or more fonts, as needed for the locale of the text.  Fonts
are loaded according to a list of base font names supplied
by the client and the charsets required by the locale.	The
XFontSet is an opaque type representing the state of a par-
ticular output thread and is equivalent to the type XOC.


The XCreateFontSet function is a convenience function for
creating an output context using only default values.  The
returned XFontSet has an implicitly created XOM.  This XOM
has an OM value XNOMAutomatic automatically set to True so
that the output context self indicates whether it was cre-
ated by XCreateOC or XCreateFontSet.
__
|
XFontSet XCreateFontSet(display, base_font_name_list, missing_charset_list_return,
	       missing_charset_count_return, def_string_return)
      Display *display;
      char *base_font_name_list;
      char ***missing_charset_list_return;
      int *missing_charset_count_return;
      char **def_string_return;


display   Specifies the connection to the X server.

base_font_name_list
	  Specifies the base font names.

missing_charset_list_return
	  Returns the missing charsets.

missing_charset_count_return
	  Returns the number of missing charsets.

def_string_return
	  Returns the string drawn for missing charsets.
|__

The XCreateFontSet function creates a font set for the spec-
ified display.	The font set is bound to the current locale
when XCreateFontSet is called.	The font set may be used in
subsequent calls to obtain font and character information
and to image text in the locale of the font set.

The base_font_name_list argument is a list of base font
names that Xlib uses to load the fonts needed for the
locale.  The base font names are a comma-separated list.



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The string is null-terminated and is assumed to be in the
Host Portable Character Encoding; otherwise, the result is
implementation-dependent.  White space immediately on either
side of a separating comma is ignored.

Use of XLFD font names permits Xlib to obtain the fonts
needed for a variety of locales from a single locale-inde-
pendent base font name.  The single base font name should
name a family of fonts whose members are encoded in the var-
ious charsets needed by the locales of interest.

An XLFD base font name can explicitly name a charset needed
for the locale.  This allows the user to specify an exact
font for use with a charset required by a locale, fully con-
trolling the font selection.

If a base font name is not an XLFD name, Xlib will attempt
to obtain an XLFD name from the font properties for the
font.  If this action is successful in obtaining an XLFD
name, the XBaseFontNameListOfFontSet function will return
this XLFD name instead of the client-supplied name.

Xlib uses the following algorithm to select the fonts that
will be used to display text with the XFontSet.

For each font charset required by the locale, the base font
name list is searched for the first appearance of one of the
following cases that names a set of fonts that exist at the
server:

o    The first XLFD-conforming base font name that specifies
     the required charset or a superset of the required
     charset in its CharSetRegistry and CharSetEncoding
     fields.  The implementation may use a base font name
     whose specified charset is a superset of the required
     charset, for example, an ISO8859-1 font for an ASCII
     charset.

o    The first set of one or more XLFD-conforming base font
     names that specify one or more charsets that can be
     remapped to support the required charset.	The Xlib
     implementation may recognize various mappings from a
     required charset to one or more other charsets and use
     the fonts for those charsets.  For example, JIS Roman
     is ASCII with tilde and backslash replaced by yen and
     overbar; Xlib may load an ISO8859-1 font to support
     this character set if a JIS Roman font is not avail-
     able.

o    The first XLFD-conforming font name or the first non-
     XLFD font name for which an XLFD font name can be
     obtained, combined with the required charset (replacing
     the CharSetRegistry and CharSetEncoding fields in the
     XLFD font name).  As in case 1, the implementation may



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     use a charset that is a superset of the required
     charset.

o    The first font name that can be mapped in some imple-
     mentation-dependent manner to one or more fonts that
     support imaging text in the charset.

For example, assume that a locale required the charsets:


ISO8859-1
JISX0208.1983
JISX0201.1976
GB2312-1980.0


The user could supply a base_font_name_list that explicitly
specifies the charsets, ensuring that specific fonts are
used if they exist.  For example:


"-JIS-Fixed-Medium-R-Normal--26-180-100-100-C-240-JISX0208.1983-0,\
-JIS-Fixed-Medium-R-Normal--26-180-100-100-C-120-JISX0201.1976-0,\
-GB-Fixed-Medium-R-Normal--26-180-100-100-C-240-GB2312-1980.0,\
-Adobe-Courier-Bold-R-Normal--25-180-75-75-M-150-ISO8859-1"


Alternatively, the user could supply a base_font_name_list
that omits the charsets, letting Xlib select font charsets
required for the locale.  For example:


"-JIS-Fixed-Medium-R-Normal--26-180-100-100-C-240,\
-JIS-Fixed-Medium-R-Normal--26-180-100-100-C-120,\
-GB-Fixed-Medium-R-Normal--26-180-100-100-C-240,\
-Adobe-Courier-Bold-R-Normal--25-180-100-100-M-150"


Alternatively, the user could simply supply a single base
font name that allows Xlib to select from all available
fonts that meet certain minimum XLFD property requirements.
For example:


"-*-*-*-R-Normal--*-180-100-100-*-*"


If XCreateFontSet is unable to create the font set, either
because there is insufficient memory or because the current
locale is not supported, XCreateFontSet returns NULL, miss-
ing_charset_list_return is set to NULL, and miss-
ing_charset_count_return is set to zero.  If fonts exist for
all of the charsets required by the current locale, XCreate-
FontSet returns a valid XFontSet,



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missing_charset_list_return is set to NULL, and miss-
ing_charset_count_return is set to zero.

If no font exists for one or more of the required charsets,
XCreateFontSet sets missing_charset_list_return to a list of
one or more null-terminated charset names for which no font
exists and sets missing_charset_count_return to the number
of missing fonts.  The charsets are from the list of the
required charsets for the encoding of the locale and do not
include any charsets to which Xlib may be able to remap a
required charset.

If no font exists for any of the required charsets or if the
locale definition in Xlib requires that a font exist for a
particular charset and a font is not found for that charset,
XCreateFontSet returns NULL.  Otherwise, XCreateFontSet
returns a valid XFontSet to font_set.

When an Xmb/wc/utf8 drawing or measuring function is called
with an XFontSet that has missing charsets, some characters
in the locale will not be drawable.  If def_string_return is
non-NULL, XCreateFontSet returns a pointer to a string that
represents the glyphs that are drawn with this XFontSet when
the charsets of the available fonts do not include all font
glyphs required to draw a codepoint.  The string does not
necessarily consist of valid characters in the current
locale and is not necessarily drawn with the fonts loaded
for the font set, but the client can draw and measure the
default glyphs by including this string in a string being
drawn or measured with the XFontSet.

If the string returned to def_string_return is the empty
string (""), no glyphs are drawn, and the escapement is
zero.  The returned string is null-terminated.	It is owned
by Xlib and should not be modified or freed by the client.
It will be freed by a call to XFreeFontSet with the associ-
ated XFontSet.	Until freed, its contents will not be modi-
fied by Xlib.

The client is responsible for constructing an error message
from the missing charset and default string information and
may choose to continue operation in the case that some fonts
did not exist.

The returned XFontSet and missing charset list should be
freed with XFreeFontSet and XFreeStringList, respectively.
The client-supplied base_font_name_list may be freed by the
client after calling XCreateFontSet.


To obtain a list of XFontStruct structures and full font
names given an XFontSet, use XFontsOfFontSet.





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__
|
int XFontsOfFontSet(font_set, font_struct_list_return, font_name_list_return)
       XFontSet font_set;
       XFontStruct ***font_struct_list_return;
       char ***font_name_list_return;


font_set  Specifies the font set.

font_struct_list_return
	  Returns the list of font structs.

font_name_list_return
	  Returns the list of font names.
|__

The XFontsOfFontSet function returns a list of one or more
XFontStructs and font names for the fonts used by the
Xmb/wc/utf8 layer for the given font set.  A list of point-
ers to the XFontStruct structures is returned to
font_struct_list_return.  A list of pointers to null-termi-
nated, fully specified font name strings in the locale of
the font set is returned to font_name_list_return.  The
font_name_list order corresponds to the font_struct_list
order.	The number of XFontStruct structures and font names
is returned as the value of the function.

Because it is not guaranteed that a given character will be
imaged using a single font glyph, there is no provision for
mapping a character or default string to the font proper-
ties, font ID, or direction hint for the font for the char-
acter.	The client may access the XFontStruct list to obtain
these values for all the fonts currently in use.

Xlib does not guarantee that fonts are loaded from the
server at the creation of an XFontSet.	Xlib may choose to
cache font data, loading it only as needed to draw text or
compute text dimensions.  Therefore, existence of the
per_char metrics in the XFontStruct structures in the
XFontStructSet is undefined.  Also, note that all properties
in the XFontStruct structures are in the STRING encoding.

The XFontStruct and font name lists are owned by Xlib and
should not be modified or freed by the client.	They will be
freed by a call to XFreeFontSet with the associated
XFontSet.  Until freed, their contents will not be modified
by Xlib.


To obtain the base font name list and the selected font name
list given an XFontSet, use XBaseFontNameListOfFontSet.






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__
|
char *XBaseFontNameListOfFontSet(font_set)
      XFontSet font_set;


font_set  Specifies the font set.
|__

The XBaseFontNameListOfFontSet function returns the original
base font name list supplied by the client when the XFontSet
was created.  A null-terminated string containing a list of
comma-separated font names is returned as the value of the
function.  White space may appear immediately on either side
of separating commas.

If XCreateFontSet obtained an XLFD name from the font prop-
erties for the font specified by a non-XLFD base name, the
XBaseFontNameListOfFontSet function will return the XLFD
name instead of the non-XLFD base name.

The base font name list is owned by Xlib and should not be
modified or freed by the client.  It will be freed by a call
to XFreeFontSet with the associated XFontSet.  Until freed,
its contents will not be modified by Xlib.


To obtain the locale name given an XFontSet, use XLocaleOf-
FontSet.
__
|
char *XLocaleOfFontSet(font_set)
      XFontSet font_set;


font_set  Specifies the font set.
|__

The XLocaleOfFontSet function returns the name of the locale
bound to the specified XFontSet, as a null-terminated
string.

The returned locale name string is owned by Xlib and should
not be modified or freed by the client.  It may be freed by
a call to XFreeFontSet with the associated XFontSet.  Until
freed, it will not be modified by Xlib.


The XFreeFontSet function is a convenience function for
freeing an output context.  XFreeFontSet also frees its
associated XOM if the output context was created by XCreate-
FontSet.






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__
|
void XFreeFontSet(display, font_set)
      Display *display;
      XFontSet font_set;


display   Specifies the connection to the X server.

font_set  Specifies the font set.
|__

The XFreeFontSet function frees the specified font set.  The
associated base font name list, font name list, XFontStruct
list, and XFontSetExtents, if any, are freed.

13.4.7.  Obtaining Font Set Metrics

Metrics for the internationalized text drawing functions are
defined in terms of a primary draw direction, which is the
default direction in which the character origin advances for
each succeeding character in the string.  The Xlib interface
is currently defined to support only a left-to-right primary
draw direction.  The drawing origin is the position passed
to the drawing function when the text is drawn.  The base-
line is a line drawn through the drawing origin parallel to
the primary draw direction.  Character ink is the pixels
painted in the foreground color and does not include inter-
line or intercharacter spacing or image text background pix-
els.

The drawing functions are allowed to implement implicit text
directionality control, reversing the order in which charac-
ters are rendered along the primary draw direction in
response to locale-specific lexical analysis of the string.

Regardless of the character rendering order, the origins of
all characters are on the primary draw direction side of the
drawing origin.  The screen location of a particular charac-
ter image may be determined with XmbTextPerCharExtents, Xwc-
TextPerCharExtents or Xutf8TextPerCharExtents.

The drawing functions are allowed to implement context-
dependent rendering, where the glyphs drawn for a string are
not simply a concatenation of the glyphs that represent each
individual character.  A string of two characters drawn with
XmbDrawString may render differently than if the two charac-
ters were drawn with separate calls to XmbDrawString.  If
the client appends or inserts a character in a previously
drawn string, the client may need to redraw some adjacent
characters to obtain proper rendering.


To find out about direction-dependent rendering, use XDirec-
tionalDependentDrawing.



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__
|
Bool XDirectionalDependentDrawing(font_set)
      XFontSet font_set;


font_set  Specifies the font set.
|__

The XDirectionalDependentDrawing function returns True if
the drawing functions implement implicit text directional-
ity; otherwise, it returns False.


To find out about context-dependent rendering, use XContex-
tualDrawing.
__
|
Bool XContextualDrawing(font_set)
      XFontSet font_set;


font_set  Specifies the font set.
|__

The XContextualDrawing function returns True if text drawn
with the font set might include context-dependent drawing;
otherwise, it returns False.


To find out about context-dependent or direction-dependent
rendering, use XContextDependentDrawing.
__
|
Bool XContextDependentDrawing(font_set)
      XFontSet font_set;


font_set  Specifies the font set.
|__

The XContextDependentDrawing function returns True if the
drawing functions implement implicit text directionality or
if text drawn with the font_set might include context-depen-
dent drawing; otherwise, it returns False.

The drawing functions do not interpret newline, tab, or
other control characters.  The behavior when nonprinting
characters other than space are drawn is implementation-
dependent.  It is the client's responsibility to interpret
control characters in a text stream.

The maximum character extents for the fonts that are used by
the text drawing layers can be accessed by the XFontSetEx-
tents structure:



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typedef struct {
     XRectangle max_ink_extent;/* over all drawable characters */
     XRectangle max_logical_extent;/* over all drawable characters */
} XFontSetExtents;


The XRectangle structures used to return font set metrics
are the usual Xlib screen-oriented rectangles with x, y giv-
ing the upper left corner, and width and height always posi-
tive.

The max_ink_extent member gives the maximum extent, over all
drawable characters, of the rectangles that bound the char-
acter glyph image drawn in the foreground color, relative to
a constant origin.  See XmbTextExtents, XwcTextExtents and
Xutf8TextExtents for detailed semantics.

The max_logical_extent member gives the maximum extent, over
all drawable characters, of the rectangles that specify min-
imum spacing to other graphical features, relative to a con-
stant origin.  Other graphical features drawn by the client,
for example, a border surrounding the text, should not
intersect this rectangle.  The max_logical_extent member
should be used to compute minimum interline spacing and the
minimum area that must be allowed in a text field to draw a
given number of arbitrary characters.

Due to context-dependent rendering, appending a given char-
acter to a string may change the string's extent by an
amount other than that character's individual extent.

The rectangles for a given character in a string can be
obtained from XmbPerCharExtents, XwcPerCharExtents or
Xutf8PerCharExtents.


To obtain the maximum extents structure given an XFontSet,
use XExtentsOfFontSet.
__
|
XFontSetExtents *XExtentsOfFontSet(font_set)
       XFontSet font_set;


font_set  Specifies the font set.
|__

The XExtentsOfFontSet function returns an XFontSetExtents
structure for the fonts used by the Xmb/wc/utf8 layer for
the given font set.

The XFontSetExtents structure is owned by Xlib and should
not be modified or freed by the client.  It will be freed by
a call to XFreeFontSet with the associated XFontSet.  Until



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freed, its contents will not be modified by Xlib.


To obtain the escapement in pixels of the specified text as
a value, use XmbTextEscapement, XwcTextEscapement or
Xutf8TextEscapement.
__
|
int XmbTextEscapement(font_set, string, num_bytes)
      XFontSet font_set;
      char *string;
      int num_bytes;


int XwcTextEscapement(font_set, string, num_wchars)
      XFontSet font_set;
      wchar_t *string;
      int num_wchars;


int Xutf8TextEscapement(font_set, string, num_bytes)
      XFontSet font_set;
      char *string;
      int num_bytes;


font_set  Specifies the font set.

string	  Specifies the character string.

num_bytes Specifies the number of bytes in the string argu-
	  ment.

num_wchars
	  Specifies the number of characters in the string
	  argument.
|__

The XmbTextEscapement, XwcTextEscapement and Xutf8Tex-
tEscapement functions return the escapement in pixels of the
specified string as a value, using the fonts loaded for the
specified font set.  The escapement is the distance in pix-
els in the primary draw direction from the drawing origin to
the origin of the next character to be drawn, assuming that
the rendering of the next character is not dependent on the
supplied string.

Regardless of the character rendering order, the escapement
is always positive.

The function Xutf8TextEscapement is an XFree86 extension
introduced in XFree86 4.0.2. Its presence is indicated by
the macro X_HAVE_UTF8_STRING.




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To obtain the overall_ink_return and overall_logical_return
arguments, the overall bounding box of the string's image,
and a logical bounding box, use XmbTextExtents, XwcTextEx-
tents or Xutf8TextExtents.
__
|
int XmbTextExtents(font_set, string, num_bytes, overall_ink_return, overall_logical_return)
      XFontSet font_set;
      char *string;
      int num_bytes;
      XRectangle *overall_ink_return;
      XRectangle *overall_logical_return;


int XwcTextExtents(font_set, string, num_wchars,
overall_ink_return, overall_logical_return)
      XFontSet font_set;
      wchar_t *string;
      int num_wchars;
      XRectangle *overall_ink_return;
      XRectangle *overall_logical_return;


int Xutf8TextExtents(font_set, string, num_bytes, overall_ink_return, overall_logical_return)
      XFontSet font_set;
      char *string;
      int num_bytes;
      XRectangle *overall_ink_return;
      XRectangle *overall_logical_return;


font_set  Specifies the font set.

string	  Specifies the character string.

num_bytes Specifies the number of bytes in the string argu-
	  ment.

num_wchars
	  Specifies the number of characters in the string
	  argument.

overall_ink_return
	  Returns the overall ink dimensions.

overall_logical_return
	  Returns the overall logical dimensions.
|__

The XmbTextExtents, XwcTextExtents and Xutf8TextExtents
functions set the components of the specified over-
all_ink_return and overall_logical_return arguments to the
overall bounding box of the string's image and a logical
bounding box for spacing purposes, respectively.  They



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return the value returned by XmbTextEscapement, XwcTex-
tEscapement or Xutf8TextEscapement.  These metrics are rela-
tive to the drawing origin of the string, using the fonts
loaded for the specified font set.

If the overall_ink_return argument is non-NULL, it is set to
the bounding box of the string's character ink.  The over-
all_ink_return for a nondescending, horizontally drawn Latin
character is conventionally entirely above the baseline;
that is, overall_ink_return.height <= -overall_ink_return.y.
The overall_ink_return for a nonkerned character is entirely
at, and to the right of, the origin; that is, over-
all_ink_return.x >= 0.	A character consisting of a single
pixel at the origin would set overall_ink_return fields y =
0, x = 0, width = 1, and height = 1.

If the overall_logical_return argument is non-NULL, it is
set to the bounding box that provides minimum spacing to
other graphical features for the string.  Other graphical
features, for example, a border surrounding the text, should
not intersect this rectangle.

When the XFontSet has missing charsets, metrics for each
unavailable character are taken from the default string
returned by XCreateFontSet so that the metrics represent the
text as it will actually be drawn.  The behavior for an
invalid codepoint is undefined.

To determine the effective drawing origin for a character in
a drawn string, the client should call XmbTextPerCharExtents
on the entire string, then on the character, and subtract
the x values of the returned rectangles for the character.
This is useful to redraw portions of a line of text or to
justify words, but for context-dependent rendering, the
client should not assume that it can redraw the character by
itself and get the same rendering.

The function Xutf8TextExtents is an XFree86 extension intro-
duced in XFree86 4.0.2. Its presence is indicated by the
macro X_HAVE_UTF8_STRING.


To obtain per-character information for a text string, use
XmbTextPerCharExtents, XwcTextPerCharExtents or
Xutf8TextPerCharExtents.












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__
|
Status XmbTextPerCharExtents(font_set, string, num_bytes, ink_array_return,
	   logical_array_return, array_size, num_chars_return, overall_ink_return, overall_logical_return)
      XFontSet font_set;
      char *string;
      int num_bytes;
      XRectangle *ink_array_return;
      XRectangle *logical_array_return;
      int array_size;
      int *num_chars_return;
      XRectangle *overall_ink_return;
      XRectangle *overall_logical_return;


Status XwcTextPerCharExtents(font_set, string, num_wchars, ink_array_return,
	  logical_array_return, array_size, num_chars_return, overall_ink_return, overall_ink_return)
      XFontSet font_set;
      wchar_t *string;
      int num_wchars;
      XRectangle *ink_array_return;
      XRectangle *logical_array_return;
      int array_size;
      int *num_chars_return;
      XRectangle *overall_ink_return;
      XRectangle *overall_logical_return;


Status Xutf8TextPerCharExtents(font_set, string, num_bytes, ink_array_return,
	   logical_array_return, array_size, num_chars_return, overall_ink_return, overall_logical_return)
      XFontSet font_set;
      char *string;
      int num_bytes;
      XRectangle *ink_array_return;
      XRectangle *logical_array_return;
      int array_size;
      int *num_chars_return;
      XRectangle *overall_ink_return;
      XRectangle *overall_logical_return;


font_set  Specifies the font set.

string	  Specifies the character string.

num_bytes Specifies the number of bytes in the string argu-
	  ment.

num_wchars
	  Specifies the number of characters in the string
	  argument.

ink_array_return
	  Returns the ink dimensions for each character.




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logical_array_return
	  Returns the logical dimensions for each character.

array_size
	  Specifies the size of ink_array_return and logi-
	  cal_array_return.  The caller must pass in arrays
	  of this size.

num_chars_return
	  Returns the number of characters in the string
	  argument.

overall_ink_return
	  Returns the overall ink extents of the entire
	  string.

overall_logical_return
	  Returns the overall logical extents of the entire
	  string.
|__

The XmbTextPerCharExtents, XwcTextPerCharExtents and
Xutf8TextPerCharExtents functions return the text dimensions
of each character of the specified text, using the fonts
loaded for the specified font set.  Each successive element
of ink_array_return and logical_array_return is set to the
successive character's drawn metrics, relative to the draw-
ing origin of the string and one rectangle for each charac-
ter in the supplied text string.  The number of elements of
ink_array_return and logical_array_return that have been set
is returned to num_chars_return.

Each element of ink_array_return is set to the bounding box
of the corresponding character's drawn foreground color.
Each element of logical_array_return is set to the bounding
box that provides minimum spacing to other graphical fea-
tures for the corresponding character.	Other graphical fea-
tures should not intersect any of the logical_array_return
rectangles.

Note that an XRectangle represents the effective drawing
dimensions of the character, regardless of the number of
font glyphs that are used to draw the character or the
direction in which the character is drawn.  If multiple
characters map to a single character glyph, the dimensions
of all the XRectangles of those characters are the same.

When the XFontSet has missing charsets, metrics for each
unavailable character are taken from the default string
returned by XCreateFontSet so that the metrics represent the
text as it will actually be drawn.  The behavior for an
invalid codepoint is undefined.





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If the array_size is too small for the number of characters
in the supplied text, the functions return zero and
num_chars_return is set to the number of rectangles
required.  Otherwise, the functions return a nonzero value.

If the overall_ink_return or overall_logical_return argument
is non-NULL, XmbTextPerCharExtents, XwcTextPerCharExtents
and Xutf8TextPerCharExtents return the maximum extent of the
string's metrics to overall_ink_return or overall_logi-
cal_return, as returned by XmbTextExtents, XwcTextExtents or
Xutf8TextExtents.

The function Xutf8TextPerCharExtents is an XFree86 extension
introduced in XFree86 4.0.2. Its presence is indicated by
the macro X_HAVE_UTF8_STRING.

13.4.8.  Drawing Text Using Font Sets

The functions defined in this section draw text at a speci-
fied location in a drawable.  They are similar to the func-
tions XDrawText, XDrawString, and XDrawImageString except
that they work with font sets instead of single fonts and
interpret the text based on the locale of the font set (for
functions whose name starts with Xmb or Xwc) or as UTF-8
encoded text (for functions whose name starts with Xutf8),
instead of treating the bytes of the string as direct font
indexes.  See section 8.6 for details of the use of Graphics
Contexts (GCs) and possible protocol errors.  If a BadFont
error is generated, characters prior to the offending char-
acter may have been drawn.

The text is drawn using the fonts loaded for the specified
font set; the font in the GC is ignored and may be modified
by the functions.  No validation that all fonts conform to
some width rule is performed.

The text functions XmbDrawText, XwcDrawText and Xutf8Draw-
Text use the following structures:



















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__
|
typedef struct {
     char *chars;	 /* pointer to string */
     int nchars;	 /* number of bytes */
     int delta; 	 /* pixel delta between strings */
     XFontSet font_set;  /* fonts, None means don't change */
} XmbTextItem;



typedef struct {
     wchar_t *chars;	 /* pointer to wide char string */
     int nchars;	 /* number of wide characters */
     int delta; 	 /* pixel delta between strings */
     XFontSet font_set;  /* fonts, None means don't change */
} XwcTextItem;

|__


To draw text using multiple font sets in a given drawable,
use XmbDrawText, XwcDrawText or Xutf8DrawText.



































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__
|
void XmbDrawText(display, d, gc, x, y, items, nitems)
      Display *display;
      Drawable d;
      GC gc;
      int x, y;
      XmbTextItem *items;
      int nitems;


void XwcDrawText(display, d, gc, x, y, items, nitems)
      Display *display;
      Drawable d;
      GC gc;
      int x, y;
      XwcTextItem *items;
      int nitems;


void Xutf8DrawText(display, d, gc, x, y, items, nitems)
      Display *display;
      Drawable d;
      GC gc;
      int x, y;
      XmbTextItem *items;
      int nitems;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

x
y	  Specify the x and y coordinates.

items	  Specifies an array of text items.

nitems	  Specifies the number of text items in the array.
|__

The XmbDrawText, XwcDrawText and Xutf8DrawText functions
allow complex spacing and font set shifts between text
strings.  Each text item is processed in turn, with the ori-
gin of a text element advanced in the primary draw direction
by the escapement of the previous text item.  A text item
delta specifies an additional escapement of the text item
drawing origin in the primary draw direction.  A font_set
member other than None in an item causes the font set to be
used for this and subsequent text items in the text_items
list.  Leading text items with a font_set member set to None
will not be drawn.




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XmbDrawText, XwcDrawText and Xutf8DrawText do not perform
any context-dependent rendering between text segments.
Clients may compute the drawing metrics by passing each text
segment to XmbTextExtents, XwcTextExtents, Xutf8TextExtents
or XmbTextPerCharExtents, XwcTextPerCharExtents.
Xutf8TextPerCharExtents.  When the XFontSet has missing
charsets, each unavailable character is drawn with the
default string returned by XCreateFontSet.  The behavior for
an invalid codepoint is undefined.

The function Xutf8DrawText is an XFree86 extension intro-
duced in XFree86 4.0.2. Its presence is indicated by the
macro X_HAVE_UTF8_STRING.


To draw text using a single font set in a given drawable,
use XmbDrawString, XwcDrawString or Xutf8DrawString.








































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__
|
void XmbDrawString(display, d, font_set, gc, x, y, string, num_bytes)
      Display *display;
      Drawable d;
      XFontSet font_set;
      GC gc;
      int x, y;
      char *string;
      int num_bytes;


void XwcDrawString(display, d, font_set, gc, x, y, string, num_wchars)
      Display *display;
      Drawable d;
      XFontSet font_set;
      GC gc;
      int x, y;
      wchar_t *string;
      int num_wchars;


void Xutf8DrawString(display, d, font_set, gc, x, y, string, num_bytes)
      Display *display;
      Drawable d;
      XFontSet font_set;
      GC gc;
      int x, y;
      char *string;
      int num_bytes;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

font_set  Specifies the font set.

gc	  Specifies the GC.

x
y	  Specify the x and y coordinates.

string	  Specifies the character string.

num_bytes Specifies the number of bytes in the string argu-
	  ment.

num_wchars
	  Specifies the number of characters in the string
	  argument.
|__

The XmbDrawString, XwcDrawString and Xutf8DrawString func-
tions draw the specified text with the foreground pixel.



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When the XFontSet has missing charsets, each unavailable
character is drawn with the default string returned by XCre-
ateFontSet.  The behavior for an invalid codepoint is unde-
fined.

The function Xutf8DrawString is an XFree86 extension intro-
duced in XFree86 4.0.2. Its presence is indicated by the
macro X_HAVE_UTF8_STRING.


To draw image text using a single font set in a given draw-
able, use XmbDrawImageString, XwcDrawImageString or
Xutf8DrawImageString.












































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__
|
void XmbDrawImageString(display, d, font_set, gc, x, y, string, num_bytes)
      Display *display;
      Drawable d;
      XFontSet font_set;
      GC gc;
      int x, y;
      char *string;
      int num_bytes;


void XwcDrawImageString(display, d, font_set, gc, x, y, string, num_wchars)
      Display *display;
      Drawable d;
      XFontSet font_set;
      GC gc;
      int x, y;
      wchar_t *string;
      int num_wchars;


void Xutf8DrawImageString(display, d, font_set, gc, x, y, string, num_bytes)
      Display *display;
      Drawable d;
      XFontSet font_set;
      GC gc;
      int x, y;
      char *string;
      int num_bytes;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

font_set  Specifies the font set.

gc	  Specifies the GC.

x
y	  Specify the x and y coordinates.

string	  Specifies the character string.

num_bytes Specifies the number of bytes in the string argu-
	  ment.

num_wchars
	  Specifies the number of characters in the string
	  argument.
|__

The XmbDrawImageString, XwcDrawImageString and Xutf8DrawIm-
ageString functions fill a destination rectangle with the



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background pixel defined in the GC and then paint the text
with the foreground pixel.  The filled rectangle is the
rectangle returned to overall_logical_return by XmbTextEx-
tents, XwcTextExtents or Xutf8TextExtents for the same text
and XFontSet.

When the XFontSet has missing charsets, each unavailable
character is drawn with the default string returned by XCre-
ateFontSet.  The behavior for an invalid codepoint is unde-
fined.

The function Xutf8TextExtents is an XFree86 extension intro-
duced in XFree86 4.0.2. Its presence is indicated by the
macro X_HAVE_UTF8_STRING.

13.5.  Input Methods

This section provides discussions of the following X Input
Method (XIM) topics:

o    Input method overview

o    Input method management

o    Input method functions

o    Input method values

o    Input context functions

o    Input context values

o    Input method callback semantics

o    Event filtering

o    Getting keyboard input

o    Input method conventions

13.5.1.  Input Method Overview

This section provides definitions for terms and concepts
used for internationalized text input and a brief overview
of the intended use of the mechanisms provided by Xlib.

A large number of languages in the world use alphabets con-
sisting of a small set of symbols (letters) to form words.
To enter text into a computer in an alphabetic language, a
user usually has a keyboard on which there exist key symbols
corresponding to the alphabet.	Sometimes, a few characters
of an alphabetic language are missing on the keyboard.	Many
computer users who speak a Latin-alphabet-based language
only have an English-based keyboard.  They need to hit a



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combination of keystrokes to enter a character that does not
exist directly on the keyboard.  A number of algorithms have
been developed for entering such characters.  These are
known as European input methods, compose input methods, or
dead-key input methods.

Japanese is an example of a language with a phonetic symbol
set, where each symbol represents a specific sound.  There
are two phonetic symbol sets in Japanese:  Katakana and
Hiragana.  In general, Katakana is used for words that are
of foreign origin, and Hiragana is used for writing native
Japanese words.  Collectively, the two systems are called
Kana.  Each set consists of 48 characters.

Korean also has a phonetic symbol set, called Hangul.  Each
of the 24 basic phonetic symbols (14 consonants and 10 vow-
els) represents a specific sound.  A syllable is composed of
two or three parts: the initial consonants, the vowels, and
the optional last consonants.  With Hangul, syllables can be
treated as the basic units on which text processing is done.
For example, a delete operation may work on a phonetic sym-
bol or a syllable.  Korean code sets include several thou-
sands of these syllables.  A user types the phonetic symbols
that make up the syllables of the words to be entered.	The
display may change as each phonetic symbol is entered.	For
example, when the second phonetic symbol of a syllable is
entered, the first phonetic symbol may change its shape and
size.  Likewise, when the third phonetic symbol is entered,
the first two phonetic symbols may change their shape and
size.

Not all languages rely solely on alphabetic or phonetic sys-
tems.  Some languages, including Japanese and Korean, employ
an ideographic writing system.	In an ideographic system,
rather than taking a small set of symbols and combining them
in different ways to create words, each word consists of one
unique symbol (or, occasionally, several symbols).  The num-
ber of symbols can be very large: approximately 50,000 have
been identified in Hanzi, the Chinese ideographic system.

Two major aspects of ideographic systems impact their use
with computers.  First, the standard computer character sets
in Japan, China, and Korea include roughly 8,000 characters,
while sets in Taiwan have between 15,000 and 30,000 charac-
ters.  This makes it necessary to use more than one byte to
represent a character.	Second, it obviously is impractical
to have a keyboard that includes all of a given language's
ideographic symbols.  Therefore, a mechanism is required for
entering characters so that a keyboard with a reasonable
number of keys can be used.  Those input methods are usually
based on phonetics, but there also exist methods based on
the graphical properties of characters.





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In Japan, both Kana and the ideographic system Kanji are
used.  In Korea, Hangul and sometimes the ideographic system
Hanja are used.  Now consider entering ideographs in Japan,
Korea, China, and Taiwan.

In Japan, either Kana or English characters are typed and
then a region is selected (sometimes automatically) for con-
version to Kanji.  Several Kanji characters may have the
same phonetic representation.  If that is the case with the
string entered, a menu of characters is presented and the
user must choose the appropriate one.  If no choice is nec-
essary or a preference has been established, the input
method does the substitution directly.	When Latin charac-
ters are converted to Kana or Kanji, it is called a romaji
conversion.

In Korea, it is usually acceptable to keep Korean text in
Hangul form, but some people may choose to write Hanja-orig-
inated words in Hanja rather than in Hangul.  To change
Hangul to Hanja, the user selects a region for conversion
and then follows the same basic method as that described for
Japanese.

Probably because there are well-accepted phonetic writing
systems for Japanese and Korean, computer input methods in
these countries for entering ideographs are fairly standard.
Keyboard keys have both English characters and phonetic sym-
bols engraved on them, and the user can switch between the
two sets.

The situation is different for Chinese.  While there is a
phonetic system called Pinyin promoted by authorities, there
is no consensus for entering Chinese text.  Some vendors use
a phonetic decomposition (Pinyin or another), others use
ideographic decomposition of Chinese words, with various
implementations and keyboard layouts.  There are about 16
known methods, none of which is a clear standard.

Also, there are actually two ideographic sets used: Tradi-
tional Chinese (the original written Chinese) and Simplified
Chinese.  Several years ago, the People's Republic of China
launched a campaign to simplify some ideographic characters
and eliminate redundancies altogether.	Under the plan,
characters would be streamlined every five years.  Charac-
ters have been revised several times now, resulting in the
smaller, simpler set that makes up Simplified Chinese.

13.5.1.1.  Input Method Architecture

As shown in the previous section, there are many different
input methods in use today, each varying with language, cul-
ture, and history.  A common feature of many input methods
is that the user may type multiple keystrokes to compose a
single character (or set of characters).  The process of



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composing characters from keystrokes is called preediting.
It may require complex algorithms and large dictionaries
involving substantial computer resources.

Input methods may require one or more areas in which to show
the feedback of the actual keystrokes, to propose disam-
biguation to the user, to list dictionaries, and so on.  The
input method areas of concern are as follows:

o    The status area is a logical extension of the LEDs that
     exist on the physical keyboard.  It is a window that is
     intended to present the internal state of the input
     method that is critical to the user.  The status area
     may consist of text data and bitmaps or some combina-
     tion.

o    The preedit area displays the intermediate text for
     those languages that are composing prior to the client
     handling the data.

o    The auxiliary area is used for pop-up menus and cus-
     tomizing dialogs that may be required for an input
     method.  There may be multiple auxiliary areas for an
     input method.  Auxiliary areas are managed by the input
     method independent of the client.	Auxiliary areas are
     assumed to be separate dialogs, which are maintained by
     the input method.

There are various user interaction styles used for preedit-
ing.  The ones supported by Xlib are as follows:

o    For on-the-spot input methods, preediting data will be
     displayed directly in the application window.  Applica-
     tion data is moved to allow preedit data to appear at
     the point of insertion.

o    Over-the-spot preediting means that the data is dis-
     played in a preedit window that is placed over the
     point of insertion.

o    Off-the-spot preediting means that the preedit window
     is inside the application window but not at the point
     of insertion.  Often, this type of window is placed at
     the bottom of the application window.

o    Root-window preediting refers to input methods that use
     a preedit window that is the child of RootWindow.

It would require a lot of computing resources if portable
applications had to include input methods for all the lan-
guages in the world.  To avoid this, a goal of the Xlib
design is to allow an application to communicate with an
input method placed in a separate process.  Such a process
is called an input server.  The server to which the



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application should connect is dependent on the environment
when the application is started up, that is, the user lan-
guage and the actual encoding to be used for it.  The input
method connection is said to be locale-dependent.  It is
also user-dependent.  For a given language, the user can
choose, to some extent, the user interface style of input
method (if choice is possible among several).

Using an input server implies communication overhead, but
applications can be migrated without relinking.  Input meth-
ods can be implemented either as a stub communicating to an
input server or as a local library.

An input method may be based on a front-end or a back-end
architecture.  In a front-end architecture, there are two
separate connections to the X server: keystrokes go directly
from the X server to the input method on one connection and
other events to the regular client connection.	The input
method is then acting as a filter and sends composed strings
to the client.	A front-end architecture requires synchro-
nization between the two connections to avoid lost key
events or locking issues.

In a back-end architecture, a single X server connection is
used.  A dispatching mechanism must decide on this channel
to delegate appropriate keystrokes to the input method.  For
instance, it may retain a Help keystroke for its own pur-
pose.  In the case where the input method is a separate pro-
cess (that is, a server), there must be a special communica-
tion protocol between the back-end client and the input
server.

A front-end architecture introduces synchronization issues
and a filtering mechanism for noncharacter keystrokes (Func-
tion keys, Help, and so on).  A back-end architecture some-
times implies more communication overhead and more process
switching.  If all three processes (X server, input server,
client) are running on a single workstation, there are two
process switches for each keystroke in a back-end architec-
ture, but there is only one in a front-end architecture.

The abstraction used by a client to communicate with an
input method is an opaque data structure represented by the
XIM data type.	This data structure is returned by the
XOpenIM function, which opens an input method on a given
display.  Subsequent operations on this data structure
encapsulate all communication between client and input
method.  There is no need for an X client to use any net-
working library or natural language package to use an input
method.

A single input server may be used for one or more languages,
supporting one or more encoding schemes.  But the strings
returned from an input method will always be encoded in the



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(single) locale associated with the XIM object.

13.5.1.2.  Input Contexts

Xlib provides the ability to manage a multi-threaded state
for text input.  A client may be using multiple windows,
each window with multiple text entry areas, and the user
possibly switching among them at any time.  The abstraction
for representing the state of a particular input thread is
called an input context.  The Xlib representation of an
input context is an XIC.

An input context is the abstraction retaining the state,
properties, and semantics of communication between a client
and an input method.  An input context is a combination of
an input method, a locale specifying the encoding of the
character strings to be returned, a client window, internal
state information, and various layout or appearance charac-
teristics.  The input context concept somewhat matches for
input the graphics context abstraction defined for graphics
output.

One input context belongs to exactly one input method.	Dif-
ferent input contexts may be associated with the same input
method, possibly with the same client window.  An XIC is
created with the XCreateIC function, providing an XIM argu-
ment and affiliating the input context to the input method
for its lifetime.  When an input method is closed with XClo-
seIM, all of its affiliated input contexts should not be
used any more (and should preferably be destroyed before
closing the input method).

Considering the example of a client window with multiple
text entry areas, the application programmer could, for
example, choose to implement as follows:

o    As many input contexts are created as text entry areas,
     and the client will get the input accumulated on each
     context each time it looks up in that context.

o    A single context is created for a top-level window in
     the application.  If such a window contains several
     text entry areas, each time the user moves to another
     text entry area, the client has to indicate changes in
     the context.

A range of choices can be made by application designers to
use either a single or multiple input contexts, according to
the needs of their application.

13.5.1.3.  Getting Keyboard Input

To obtain characters from an input method, a client must
call the function XmbLookupString, XwcLookupString or



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Xutf8LookupString with an input context created from that
input method.  Both a locale and display are bound to an
input method when it is opened, and an input context inher-
its this locale and display.  Any strings returned by
XmbLookupString or XwcLookupString will be encoded in that
locale. Strings returned by Xutf8LookupString are encoded in
UTF-8.

13.5.1.4.  Focus Management

For each text entry area in which the XmbLookupString,
XwcLookupString or Xutf8LookupString functions are used,
there will be an associated input context.

When the application focus moves to a text entry area, the
application must set the input context focus to the input
context associated with that area.  The input context focus
is set by calling XSetICFocus with the appropriate input
context.

Also, when the application focus moves out of a text entry
area, the application should unset the focus for the associ-
ated input context by calling XUnsetICFocus.  As an opti-
mization, if XSetICFocus is called successively on two dif-
ferent input contexts, setting the focus on the second will
automatically unset the focus on the first.

To set and unset the input context focus correctly, it is
necessary to track application-level focus changes.  Such
focus changes do not necessarily correspond to X server
focus changes.

If a single input context is being used to do input for mul-
tiple text entry areas, it will also be necessary to set the
focus window of the input context whenever the focus window
changes (see section 13.5.6.3).

13.5.1.5.  Geometry Management

In most input method architectures (on-the-spot being the
notable exception), the input method will perform the dis-
play of its own data.  To provide better visual locality, it
is often desirable to have the input method areas embedded
within a client.  To do this, the client may need to allo-
cate space for an input method.  Xlib provides support that
allows the size and position of input method areas to be
provided by a client.  The input method areas that are sup-
ported for geometry management are the status area and the
preedit area.

The fundamental concept on which geometry management for
input method windows is based is the proper division of
responsibilities between the client (or toolkit) and the
input method.  The division of responsibilities is as



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follows:

o    The client is responsible for the geometry of the input
     method window.

o    The input method is responsible for the contents of the
     input method window.

An input method is able to suggest a size to the client, but
it cannot suggest a placement.	Also the input method can
only suggest a size.  It does not determine the size, and it
must accept the size it is given.

Before a client provides geometry management for an input
method, it must determine if geometry management is needed.
The input method indicates the need for geometry management
by setting XIMPreeditArea or XIMStatusArea in its XIMStyles
value returned by XGetIMValues.  When a client has decided
that it will provide geometry management for an input
method, it indicates that decision by setting the XNInput-
Style value in the XIC.

After a client has established with the input method that it
will do geometry management, the client must negotiate the
geometry with the input method.  The geometry is negotiated
by the following steps:

o    The client suggests an area to the input method by set-
     ting the XNAreaNeeded value for that area.  If the
     client has no constraints for the input method, it
     either will not suggest an area or will set the width
     and height to zero.  Otherwise, it will set one of the
     values.

o    The client will get the XIC value XNAreaNeeded.  The
     input method will return its suggested size in this
     value.  The input method should pay attention to any
     constraints suggested by the client.

o    The client sets the XIC value XNArea to inform the
     input method of the geometry of its window.  The client
     should try to honor the geometry requested by the input
     method.  The input method must accept this geometry.

Clients doing geometry management must be aware that setting
other XIC values may affect the geometry desired by an input
method.  For example, XNFontSet and XNLineSpacing may change
the geometry desired by the input method.

The table of XIC values (see section 13.5.6) indicates the
values that can cause the desired geometry to change when
they are set.  It is the responsibility of the client to
renegotiate the geometry of the input method window when it
is needed.



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In addition, a geometry management callback is provided by
which an input method can initiate a geometry change.

13.5.1.6.  Event Filtering

A filtering mechanism is provided to allow input methods to
capture X events transparently to clients.  It is expected
that toolkits (or clients) using XmbLookupString, XwcLookup-
String or Xutf8LookupString will call this filter at some
point in the event processing mechanism to make sure that
events needed by an input method can be filtered by that
input method.

If there were no filter, a client could receive and discard
events that are necessary for the proper functioning of an
input method.  The following provides a few examples of such
events:

o    Expose events on preedit window in local mode.

o    Events may be used by an input method to communicate
     with an input server.  Such input server protocol-
     related events have to be intercepted if one does not
     want to disturb client code.

o    Key events can be sent to a filter before they are
     bound to translations such as those the X Toolkit
     Intrinsics library provides.

Clients are expected to get the XIC value XNFilterEvents and
augment the event mask for the client window with that event
mask.  This mask may be zero.

13.5.1.7.  Callbacks

When an on-the-spot input method is implemented, only the
client can insert or delete preedit data in place and possi-
bly scroll existing text.  This means that the echo of the
keystrokes has to be achieved by the client itself, tightly
coupled with the input method logic.

When the user enters a keystroke, the client calls
XmbLookupString, XwcLookupString or Xutf8LookupString.	At
this point, in the on-the-spot case, the echo of the
keystroke in the preedit has not yet been done.  Before
returning to the client logic that handles the input charac-
ters, the look-up function must call the echoing logic to
insert the new keystroke.  If the keystrokes entered so far
make up a character, the keystrokes entered need to be
deleted, and the composed character will be returned.
Hence, what happens is that, while being called by client
code, the input method logic has to call back to the client
before it returns.  The client code, that is, a callback
procedure, is called from the input method logic.



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There are a number of cases where the input method logic has
to call back the client.  Each of those cases is associated
with a well-defined callback action.  It is possible for the
client to specify, for each input context, what callback is
to be called for each action.

There are also callbacks provided for feedback of status
information and a callback to initiate a geometry request
for an input method.

13.5.1.8.  Visible Position Feedback Masks

In the on-the-spot input style, there is a problem when
attempting to draw preedit strings that are longer than the
available space.  Once the display area is exceeded, it is
not clear how best to display the preedit string.  The visi-
ble position feedback masks of XIMText help resolve this
problem by allowing the input method to specify hints that
indicate the essential portions of the preedit string.	For
example, such hints can help developers implement scrolling
of a long preedit string within a short preedit display
area.

13.5.1.9.  Preedit String Management

As highlighted before, the input method architecture pro-
vides preediting, which supports a type of preprocessor
input composition.  In this case, composition consists of
interpreting a sequence of key events and returning a com-
mitted string via XmbLookupString, XwcLookupString or
Xutf8LookupString.  This provides the basics for input meth-
ods.

In addition to preediting based on key events, a general
framework is provided to give a client that desires it more
advanced preediting based on the text within the client.
This framework is called string conversion and is provided
using XIC values.  The fundamental concept of string conver-
sion is to allow the input method to manipulate the client's
text independent of any user preediting operation.

The need for string conversion is based on language needs
and input method capabilities.	The following are some exam-
ples of string conversion:

o    Transliteration conversion provides language-specific
     conversions within the input method.  In the case of
     Korean input, users wish to convert a Hangul string
     into a Hanja string while in preediting, after preedit-
     ing, or in other situations (for example, on a selected
     string).  The conversion is triggered when the user
     presses a Hangul-to-Hanja key sequence (which may be
     input method specific).  Sometimes the user may want to
     invoke the conversion after finishing preediting or on



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     a user-selected string.  Thus, the string to be con-
     verted is in an application buffer, not in the preedit
     area of the input method.	The string conversion ser-
     vices allow the client to request this transliteration
     conversion from the input method.	There are many other
     transliteration conversions defined for various lan-
     guages, for example, Kana-to-Kanji conversion in
     Japanese.

     The key to remember is that transliteration conversions
     are triggered at the request of the user and returned
     to the client immediately without affecting the preedit
     area of the input method.

o    Reconversion of a previously committed string or a
     selected string is supported by many input methods as a
     convenience to the user.  For example, a user tends to
     mistype the commit key while preediting.  In that case,
     some input methods provide a special key sequence to
     request a ``reconvert'' operation on the committed
     string, similiar to the undo facility provided by most
     text editors.  Another example is where the user is
     proofreading a document that has some misconversions
     from preediting and wants to correct the misconverted
     text.  Such reconversion is again triggered by the user
     invoking some special action, but reconversions should
     not affect the state of the preedit area.

o    Context-sensitive conversion is required for some lan-
     guages and input methods that need to retrieve text
     that surrounds the current spot location (cursor posi-
     tion) of the client's buffer.  Such text is needed when
     the preediting operation depends on some surrounding
     characters (usually preceding the spot location).	For
     example, in Thai language input, certain character
     sequences may be invalid and the input method may want
     to check whether characters constitute a valid word.
     Input methods that do such context-dependent checking
     need to retrieve the characters surrounding the current
     cursor position to obtain complete words.

     Unlike other conversions, this conversion is not
     explicitly requested by the user.	Input methods that
     provide such context-sensitive conversion continuously
     need to request context from the client, and any change
     in the context of the spot location may affect such
     conversions.  The client's context would be needed if
     the user moves the cursor and starts editing again.

     For this reason, an input method supporting this type
     of conversion should take notice of when the client
     calls XmbResetIC, XwcResetIC or Xutf8ResetIC, which is
     usually an indication of a context change.




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Context-sensitive conversions just need a copy of the
client's text, while other conversions replace the client's
text with new text to achieve the reconversion or translit-
eration.   Yet in all cases the result of a conversion,
either immediately or via preediting, is returned by the
XmbLookupString, XwcLookupString and Xutf8LookupString func-
tions.

String conversion support is dependent on the availability
of the XNStringConversion or XNStringConversionCallback XIC
values.  Because the input method may not support string
conversions, clients have to query the availability of
string conversion operations by checking the supported XIC
values list by calling XGetIMValues with the XNQueryICVal-
uesList IM value.

The difference between these two values is whether the con-
version is invoked by the client or the input method.  The
XNStringConversion XIC value is used by clients to request a
string conversion from the input method.  The client is
responsible for determining which events are used to trigger
the string conversion and whether the string to be converted
should be copied or deleted.  The type of conversion is
determined by the input method; the client can only pass the
string to be converted.  The client is guaranteed that no
XNStringConversionCallback will be issued when this value is
set; thus, the client need only set one of these values.

The XNStringConversionCallback XIC value is used by the
client to notify the input method that it will accept
requests from the input method for string conversion.  If
this value is set, it is the input method's responsibility
to determine which events are used to trigger the string
conversion.  When such events occur, the input method issues
a call to the client-supplied procedure to retrieve the
string to be converted.  The client's callback procedure is
notified whether to copy or delete the string and is pro-
vided with hints as to the amount of text needed.  The XIM-
StringConversionCallbackStruct specifies which text should
be passed back to the input method.

Finally, the input method may call the client's XNStringCon-
versionCallback procedure multiple times if the string
returned from the callback is not sufficient to perform a
successful conversion.	 The arguments to the client's pro-
cedure allow the input method to define a position (in char-
acter units) relative to the client's cursor position and
the size of the text needed.  By varying the position and
size of the desired text in subsequent callbacks, the input
method can retrieve additional text.







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13.5.2.  Input Method Management

The interface to input methods might appear to be simply
creating an input method (XOpenIM) and freeing an input
method (XCloseIM).  However, input methods may require com-
plex communication with input method servers (IM servers),
for example:

o    If the X server, IM server, and X clients are started
     asynchronously, some clients may attempt to connect to
     the IM server before it is fully operational, and fail.
     Therefore, some mechanism is needed to allow clients to
     detect when an IM server has started.

It is up to clients to decide what should be done when an IM
server is not available (for example, wait, or use some
other IM server).


o    Some input methods may allow the underlying IM server
     to be switched.  Such customization may be desired
     without restarting the entire client.

To support management of input methods in these cases, the
following functions are provided:

XRegisterIMInstantiate-    This function allows clients to
Callback		   register a callback procedure to
			   be called when Xlib detects that
			   an IM server is up and available.
XOpenIM 		   A client calls this function as a
			   result of the callback procedure
			   being called.
XSetIMValue, XSetICValue   These functions use the XIM and
			   XIC values, XNDestroyCallback, to
			   allow a client to register a
			   callback procedure to be called
			   when Xlib detects that an IM
			   server that was associated with
			   an opened input method is no
			   longer available.
			   In addition, this function can be
			   used to switch IM servers for
			   those input methods that support
			   such functionality.	The IM value
			   for switching IM servers is
			   implementation-dependent; see the
			   description below about switching
			   IM servers.
XUnregisterIMInstanti-	   This function removes a callback
ateCallback		   procedure registered by the
			   client.





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Input methods that support switching of IM servers may
exhibit some side-effects:

o    The input method will ensure that any new IM server
     supports any of the input styles being used by input
     contexts already associated with the input method.
     However, the list of supported input styles may be dif-
     ferent.


o    Geometry management requests on previously created
     input contexts may be initiated by the new IM server.


13.5.2.1.  Hot Keys

Some clients need to guarantee which keys can be used to
escape from the input method, regardless of the input method
state; for example, the client-specific Help key or the keys
to move the input focus.  The HotKey mechanism allows
clients to specify a set of keys for this purpose.  However,
the input method might not allow clients to specify hot
keys.  Therefore, clients have to query support of hot keys
by checking the supported XIC values list by calling XGetIM-
Values with the XNQueryICValuesList IM value.  When the hot
keys specified conflict with the key bindings of the input
method, hot keys take precedence over the key bindings of
the input method.


13.5.2.2.  Preedit State Operation

An input method may have several internal states, depending
on its implementation and the locale.  However, one state
that is independent of locale and implementation is whether
the input method is currently performing a preediting opera-
tion.  Xlib provides the ability for an application to man-
age the preedit state programmatically.  Two methods are
provided for retrieving the preedit state of an input con-
text.  One method is to query the state by calling XGetIC-
Values with the XNPreeditState XIC value.  Another method is
to receive notification whenever the preedit state is
changed.  To receive such notification, an application needs
to register a callback by calling XSetICValues with the
XNPreeditStateNotifyCallback XIC value.  In order to change
the preedit state programmatically, an application needs to
call XSetICValues with XNPreeditState.

Availability of the preedit state is input method dependent.
The input method may not provide the ability to set the
state or to retrieve the state programmatically.  Therefore,
clients have to query availability of preedit state opera-
tions by checking the supported XIC values list by calling
XGetIMValues with the XNQueryICValuesList IM value.



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13.5.3.  Input Method Functions

To open a connection, use XOpenIM.
__
|
XIM XOpenIM(display, db, res_name, res_class)
      Display *display;
      XrmDatabase db;
      char *res_name;
      char *res_class;


display   Specifies the connection to the X server.

db	  Specifies a pointer to the resource database.

res_name  Specifies the full resource name of the applica-
	  tion.

res_class Specifies the full class name of the application.
|__

The XOpenIM function opens an input method, matching the
current locale and modifiers specification.  Current locale
and modifiers are bound to the input method at opening time.
The locale associated with an input method cannot be changed
dynamically.  This implies that the strings returned by
XmbLookupString or XwcLookupString, for any input context
affiliated with a given input method, will be encoded in the
locale current at the time the input method is opened.

The specific input method to which this call will be routed
is identified on the basis of the current locale.  XOpenIM
will identify a default input method corresponding to the
current locale.  That default can be modified using XSetLo-
caleModifiers for the input method modifier.

The db argument is the resource database to be used by the
input method for looking up resources that are private to
the input method.  It is not intended that this database be
used to look up values that can be set as IC values in an
input context.	If db is NULL, no database is passed to the
input method.

The res_name and res_class arguments specify the resource
name and class of the application.  They are intended to be
used as prefixes by the input method when looking up
resources that are common to all input contexts that may be
created for this input method.	The characters used for
resource names and classes must be in the X Portable Charac-
ter Set.  The resources looked up are not fully specified if
res_name or res_class is NULL.





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The res_name and res_class arguments are not assumed to
exist beyond the call to XOpenIM.  The specified resource
database is assumed to exist for the lifetime of the input
method.

XOpenIM returns NULL if no input method could be opened.


To close a connection, use XCloseIM.
__
|
Status XCloseIM(im)
      XIM im;


im	  Specifies the input method.
|__

The XCloseIM function closes the specified input method.


To set input method attributes, use XSetIMValues.
__
|
char * XSetIMValues(im, ...)
      XIM im;


im	  Specifies the input method.

...	  Specifies the variable-length argument list to set
	  XIM values.
|__

The XSetIMValues function presents a variable argument list
programming interface for setting attributes of the speci-
fied input method.  It returns NULL if it succeeds; other-
wise, it returns the name of the first argument that could
not be set.  Xlib does not attempt to set arguments from the
supplied list that follow the failed argument; all arguments
in the list preceding the failed argument have been set cor-
rectly.


To query an input method, use XGetIMValues.












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__
|
char * XGetIMValues(im, ...)
      XIM im;


im	  Specifies the input method.

...	  Specifies the variable length argument list to get
	  XIM values.
|__

The XGetIMValues function presents a variable argument list
programming interface for querying properties or features of
the specified input method.  This function returns NULL if
it succeeds; otherwise, it returns the name of the first
argument that could not be obtained.

Each XIM value argument (following a name) must point to a
location where the XIM value is to be stored.  That is, if
the XIM value is of type T, the argument must be of type T*.
If T itself is a pointer type, then XGetIMValues allocates
memory to store the actual data, and the client is responsi-
ble for freeing this data by calling XFree with the returned
pointer.


To obtain the display associated with an input method, use
XDisplayOfIM.
__
|
Display * XDisplayOfIM(im)
     XIM im;


im	  Specifies the input method.
|__

The XDisplayOfIM function returns the display associated
with the specified input method.


To get the locale associated with an input method, use XLo-
caleOfIM.
__
|
char * XLocaleOfIM(im)
      XIM im;


im	  Specifies the input method.
|__

The XLocaleOfIM function returns the locale associated with
the specified input method.



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To register an input method instantiate callback, use XReg-
isterIMInstantiateCallback.
__
|
Bool XRegisterIMInstantiateCallback(display, db, res_name, res_class, callback, client_data)
      Display *display;
      XrmDatabase db;
      char *res_name;
      char *res_class;
      XIMProc  callback;
      XPointer *client_data;


display   Specifies the connection to the X server.

db	  Specifies a pointer to the resource database.

res_name  Specifies the full resource name of the applica-
	  tion.

res_class Specifies the full class name of the application.

callback  Specifies a pointer to the input method instanti-
	  ate callback.

client_data
	  Specifies the additional client data.
|__

The XRegisterIMInstantiateCallback function registers a
callback to be invoked whenever a new input method becomes
available for the specified display that matches the current
locale and modifiers.

The function returns True
 if it succeeds; otherwise, it returns False.

The generic prototype is as follows:



















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__
|
void IMInstantiateCallback(display, client_data, call_data)
      Display *display;
      XPointer client_data;
      XPointer call_data;


display   Specifies the connection to the X server.

client_data
	  Specifies the additional client data.

call_data Not used for this callback and always passed as
	  NULL.
|__

To unregister an input method instantiation callback, use
XUnregisterIMInstantiateCallback.
__
|
Bool XUnregisterIMInstantiateCallback(display, db, res_name, res_class, callback, client_data)
      Display *display;
      XrmDatabase db;
      char *res_name;
      char *res_class;
      XIMProc  callback;
      XPointer *client_data;


display   Specifies the connection to the X server.

db	  Specifies a pointer to the resource database.

res_name  Specifies the full resource name of the applica-
	  tion.

res_class Specifies the full class name of the application.

callback  Specifies a pointer to the input method instanti-
	  ate callback.

client_data
	  Specifies the additional client data.
|__

The XUnregisterIMInstantiateCallback function removes an
input method instantiation callback previously registered.
The function returns True if it succeeds; otherwise, it
returns False.

13.5.4.  Input Method Values

The following table describes how XIM values are interpreted
by an input method.  The first column lists the XIM values.



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The second column indicates how each of the XIM values are
treated by that input style.


The following keys apply to this table.

-------------------------------------------------------------
Key	     Explanation
-------------------------------------------------------------
D	     This value may be set using XSetIMValues.	If
	     it is not set,
	     a default is provided.
S	     This value may be set using XSetIMValues.
G	     This value may be read using XGetIMValues.
-------------------------------------------------------------



-------------------------------
XIM Value		  Key
-------------------------------
XNQueryInputStyle	   G
XNResourceName		 D-S-G
XNResourceClass 	 D-S-G
XNDestroyCallback	 D-S-G
XNQueryIMValuesList	   G
XNQueryICValuesList	   G
XNVisiblePosition	   G
XNR6PreeditCallbackBe-	 D-S-G
havior
-------------------------------


XNR6PreeditCallbackBehavior is obsolete and its use is not
recommended (see section 13.5.4.6).


13.5.4.1.  Query Input Style

A client should always query the input method to determine
which input styles are supported.  The client should then
find an input style it is capable of supporting.

If the client cannot find an input style that it can sup-
port, it should negotiate with the user the continuation of
the program (exit, choose another input method, and so on).

The argument value must be a pointer to a location where the
returned value will be stored.	The returned value is a
pointer to a structure of type XIMStyles.  Clients are
responsible for freeing the XIMStyles structure.  To do so,
use XFree.





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The XIMStyles structure is defined as follows:

__
|
typedef unsigned long XIMStyle;


#define   XIMPreeditArea	 0x0001L
#define   XIMPreeditCallbacks	 0x0002L
#define   XIMPreeditPosition	 0x0004L
#define   XIMPreeditNothing	 0x0008L
#define   XIMPreeditNone	 0x0010L

#define   XIMStatusArea 	 0x0100L
#define   XIMStatusCallbacks	 0x0200L
#define   XIMStatusNothing	 0x0400L
#define   XIMStatusNone 	 0x0800L


typedef struct {
     unsigned short count_styles;
     XIMStyle * supported_styles;
} XIMStyles;

|__

An XIMStyles structure contains the number of input styles
supported in its count_styles field.  This is also the size
of the supported_styles array.

The supported styles is a list of bitmask combinations,
which indicate the combination of styles for each of the
areas supported.  These areas are described later.  Each
element in the list should select one of the bitmask values
for each area.	The list describes the complete set of com-
binations supported.  Only these combinations are supported
by the input method.

The preedit category defines what type of support is pro-
vided by the input method for preedit information.

XIMPreeditArea	  If chosen, the input method would require
		  the client to provide some area values for
		  it to do its preediting.  Refer to XIC
		  values XNArea and XNAreaNeeded.
XIMPreeditPosi-   If chosen, the input method would require
tion		  the client to provide positional values.
		  Refer to XIC values XNSpotLocation and
		  XNFocusWindow.








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XIMPreeditCall-   If chosen, the input method would require
backs		  the client to define the set of preedit
		  callbacks.  Refer to XIC values XNPreedit-
		  StartCallback, XNPreeditDoneCallback,
		  XNPreeditDrawCallback, and XNPreeditCaret-
		  Callback.
XIMPreeditNoth-   If chosen, the input method can function
ing		  without any preedit values.
XIMPreeditNone	  The input method does not provide any
		  preedit feedback.  Any preedit value is
		  ignored.  This style is mutually exclusive
		  with the other preedit styles.


The status category defines what type of support is provided
by the input method for status information.

XIMStatusArea	  The input method requires the client to
		  provide some area values for it to do its
		  status feedback.  See XNArea and XNArea-
		  Needed.
XIMStatusCall-	  The input method requires the client to
backs		  define the set of status callbacks, XNSta-
		  tusStartCallback, XNStatusDoneCallback,
		  and XNStatusDrawCallback.
XIMStatusNoth-	  The input method can function without any
ing		  status values.
XIMStatusNone	  The input method does not provide any sta-
		  tus feedback.  If chosen, any status value
		  is ignored.  This style is mutually exclu-
		  sive with the other status styles.


13.5.4.2.  Resource Name and Class

The XNResourceName and XNResourceClass arguments are strings
that specify the full name and class used by the input
method.  These values should be used as prefixes for the
name and class when looking up resources that may vary
according to the input method.	If these values are not set,
the resources will not be fully specified.

It is not intended that values that can be set as XIM values
be set as resources.


13.5.4.3.  Destroy Callback

The XNDestroyCallback argument is a pointer to a structure
of type XIMCallback.  XNDestroyCallback is triggered when an
input method stops its service for any reason.	After the
callback is invoked, the input method is closed and the
associated input context(s) are destroyed by Xlib.  There-
fore, the client should not call XCloseIM or XDestroyIC.



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The generic prototype of this callback function is as fol-
lows:
__
|
void DestroyCallback(im, client_data, call_data)
      XIM im;
      XPointer client_data;
      XPointer call_data;


im	  Specifies the input method.

client_data
	  Specifies the additional client data.

call_data Not used for this callback and always passed as
	  NULL.
|__

A DestroyCallback is always called with a NULL call_data
argument.


13.5.4.4.  Query IM/IC Values List

XNQueryIMValuesList and XNQueryICValuesList are used to
query about XIM and XIC values supported by the input
method.

The argument value must be a pointer to a location where the
returned value will be stored.	The returned value is a
pointer to a structure of type XIMValuesList.  Clients are
responsible for freeing the XIMValuesList structure.  To do
so, use XFree.

The XIMValuesList structure is defined as follows:
__
|
typedef struct {
     unsigned short count_values;
     char **supported_values;
} XIMValuesList;

|__


13.5.4.5.  Visible Position

The XNVisiblePosition argument indicates whether the visible
position masks of XIMFeedback in XIMText are available.

The argument value must be a pointer to a location where the
returned value will be stored.	The returned value is of
type Bool.  If the returned value is True, the input method



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uses the visible position masks of XIMFeedback in XIMText;
otherwise, the input method does not use the masks.

Because this XIM value is optional, a client should call
XGetIMValues with argument XNQueryIMValues before using this
argument.  If the XNVisiblePosition does not exist in the IM
values list returned from XNQueryIMValues, the visible posi-
tion masks of XIMFeedback in XIMText are not used to indi-
cate the visible position.


13.5.4.6.  Preedit Callback Behavior

The XNR6PreeditCallbackBehavior argument originally included
in the X11R6 specification has been deprecated.

The XNR6PreeditCallbackBehavior argument indicates whether
the behavior of preedit callbacks regarding XIMPreeditDraw-
CallbackStruct values follows Release 5 or Release 6 seman-
tics.

The value is of type Bool.  When querying for XNR6Preedit-
CallbackBehavior, if the returned value is True, the input
method uses the Release 6 behavior; otherwise, it uses the
Release 5 behavior.  The default value is False.  In order
to use Release 6 semantics, the value of XNR6PreeditCall-
backBehavior must be set to True.

Because this XIM value is optional, a client should call
XGetIMValues with argument XNQueryIMValues before using this
argument.  If the XNR6PreeditCallbackBehavior does not exist
in the IM values list returned from XNQueryIMValues, the
PreeditCallback behavior is Release 5 semantics.


13.5.5.  Input Context Functions

An input context is an abstraction that is used to contain
both the data required (if any) by an input method and the
information required to display that data.  There may be
multiple input contexts for one input method.  The program-
ming interfaces for creating, reading, or modifying an input
context use a variable argument list.  The name elements of
the argument lists are referred to as XIC values.  It is
intended that input methods be controlled by these XIC
-----------
   During formulation of the X11R6 specification,
the behavior of the R6 PreeditDrawCallbacks was
going to differ significantly from that of the R5
callbacks.  Late changes to the specification con-
verged the R5 and R6 behaviors, eliminating the
need for XNR6PreeditCallbackBehavior.  Unfortu-
nately, this argument was not removed from the R6
specification before it was published.



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values.  As new XIC values are created, they should be reg-
istered with the X Consortium.


To create an input context, use XCreateIC.
__
|
XIC XCreateIC(im, ...)
      XIM im;


im	  Specifies the input method.

...	  Specifies the variable length argument list to set
	  XIC values.
|__

The XCreateIC function creates a context within the speci-
fied input method.

Some of the arguments are mandatory at creation time, and
the input context will not be created if those arguments are
not provided.  The mandatory arguments are the input style
and the set of text callbacks (if the input style selected
requires callbacks).  All other input context values can be
set later.

XCreateIC returns a NULL value if no input context could be
created.  A NULL value could be returned for any of the fol-
lowing reasons:

o    A required argument was not set.

o    A read-only argument was set (for example, XNFil-
     terEvents).

o    The argument name is not recognized.

o    The input method encountered an input method implemen-
     tation-dependent error.

XCreateIC can generate BadAtom, BadColor, BadPixmap, and
BadWindow errors.


To destroy an input context, use XDestroyIC.











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__
|
void XDestroyIC(ic)
      XIC ic;


ic	  Specifies the input context.
|__

XDestroyIC destroys the specified input context.


To communicate to and synchronize with input method for any
changes in keyboard focus from the client side, use XSetIC-
Focus and XUnsetICFocus.
__
|
void XSetICFocus(ic)
      XIC ic;


ic	  Specifies the input context.
|__

The XSetICFocus function allows a client to notify an input
method that the focus window attached to the specified input
context has received keyboard focus.  The input method
should take action to provide appropriate feedback.  Com-
plete feedback specification is a matter of user interface
policy.

Calling XSetICFocus does not affect the focus window value.


__
|
void XUnsetICFocus(ic)
      XIC ic;


ic	  Specifies the input context.
|__

The XUnsetICFocus function allows a client to notify an
input method that the specified input context has lost the
keyboard focus and that no more input is expected on the
focus window attached to that input context.  The input
method should take action to provide appropriate feedback.
Complete feedback specification is a matter of user inter-
face policy.

Calling XUnsetICFocus does not affect the focus window
value; the client may still receive events from the input
method that are directed to the focus window.




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To reset the state of an input context to its initial state,
use XmbResetIC, XwcResetIC or Xutf8ResetIC.
__
|
char * XmbResetIC(ic)
      XIC ic;


wchar_t * XwcResetIC(ic)
      XIC ic;


char * Xutf8ResetIC(ic)
      XIC ic;


ic	  Specifies the input context.
|__

When XNResetState is set to XIMInitialState, XmbResetIC,
XwcResetIC and Xutf8ResetIC reset an input context to its
initial state; when XNResetState is set to XIMPreserveState,
the current input context state is preserved.  In both
cases, any input pending on that context is deleted.  The
input method is required to clear the preedit area, if any,
and update the status accordingly.  Calling XmbResetIC,
XwcResetIC or Xutf8ResetIC does not change the focus.

The return value of XmbResetIC is its current preedit string
as a multibyte string.	The return value of XwcResetIC is
its current preedit string as a wide character string.	The
return value of Xutf8ResetIC is its current preedit string
as an UTF-8 string.  If there is any preedit text drawn or
visible to the user, then these procedures must return a
non-NULL string.  If there is no visible preedit text, then
it is input method implementation-dependent whether these
procedures return a non-NULL string or NULL.

The client should free the returned string by calling XFree.

The function Xutf8ResetIC is an XFree86 extension introduced
in XFree86 4.0.2. Its presence is indicated by the macro
X_HAVE_UTF8_STRING.


To get the input method associated with an input context,
use XIMOfIC.










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__
|
XIM XIMOfIC(ic)
      XIC ic;


ic	  Specifies the input context.
|__

The XIMOfIC function returns the input method associated
with the specified input context.


Xlib provides two functions for setting and reading XIC val-
ues, respectively, XSetICValues and XGetICValues.  Both
functions have a variable-length argument list.  In that
argument list, any XIC value's name must be denoted with a
character string using the X Portable Character Set.


To set XIC values, use XSetICValues.
__
|
char * XSetICValues(ic, ...)
      XIC ic;


ic	  Specifies the input context.

...	  Specifies the variable length argument list to set
	  XIC values.
|__

The XSetICValues function returns NULL if no error occurred;
otherwise, it returns the name of the first argument that
could not be set.  An argument might not be set for any of
the following reasons:

o    The argument is read-only (for example, XNFil-
     terEvents).

o    The argument name is not recognized.

o    An implementation-dependent error occurs.

Each value to be set must be an appropriate datum, matching
the data type imposed by the semantics of the argument.

XSetICValues can generate BadAtom, BadColor, BadCursor, Bad-
Pixmap, and BadWindow errors.


To obtain XIC values, use XGetICValues.





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__
|
char * XGetICValues(ic, ...)
      XIC ic;


ic	  Specifies the input context.

...	  Specifies the variable length argument list to get
	  XIC values.
|__

The XGetICValues function returns NULL if no error occurred;
otherwise, it returns the name of the first argument that
could not be obtained.	An argument could not be obtained
for any of the following reasons:

o    The argument name is not recognized.

o    The input method encountered an implementation-depen-
     dent error.

Each IC attribute value argument (following a name) must
point to a location where the IC value is to be stored.
That is, if the IC value is of type T, the argument must be
of type T*.  If T itself is a pointer type, then XGetICVal-
ues allocates memory to store the actual data, and the
client is responsible for freeing this data by calling XFree
with the returned pointer.  The exception to this rule is
for an IC value of type XVaNestedList (for preedit and sta-
tus attributes).  In this case,  the argument must also be
of type XVaNestedList.	Then, the rule of changing type T to
T* and freeing the allocated data applies to each element of
the nested list.

13.5.6.  Input Context Values

The following tables describe how XIC values are interpreted
by an input method depending on the input style chosen by
the user.

The first column lists the XIC values.	The second column
indicates which values are involved in affecting, negotiat-
ing, and setting the geometry of the input method windows.
The subentries under the third column indicate the different
input styles that are supported.  Each of these columns
indicates how each of the XIC values are treated by that
input style.

The following keys apply to these tables.








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-------------------------------------------------------------
Key	     Explanation
-------------------------------------------------------------
C	     This value must be set with XCreateIC.
D	     This value may be set using XCreateIC.  If it
	     is not set, a default is provided.
G	     This value may be read using XGetICValues.
GN	     This value may cause geometry negotiation when
	     its value is set by means of XCreateIC or XSet-
	     ICValues.
GR	     This value will be the response of the input
	     method when any GN value is changed.
GS	     This value will cause the geometry of the input
	     method window to be set.
O	     This value must be set once and only once.  It
	     need not be set at create time.
S	     This value may be set with XSetICValues.
Ignored      This value is ignored by the input method for
	     the given input style.
-------------------------------------------------------------



-----------------------------------------------------------------------------------------------
								Input Style
XIC Value			 Geometry    Preedit	Preedit    Preedit   Preedit   Preedit
				Management   Callback	Position    Area     Nothing	None
-----------------------------------------------------------------------------------------------
Input Style				       C-G	  C-G	     C-G       C-G	 C-G
Client Window				       O-G	  O-G	     O-G       O-G     Ignored
Focus Window			    GN	      D-S-G	 D-S-G	    D-S-G     D-S-G    Ignored
Resource Name				     Ignored	 D-S-G	    D-S-G     D-S-G    Ignored
Resource Class				     Ignored	 D-S-G	    D-S-G     D-S-G    Ignored
Geometry Callback			     Ignored	Ignored     D-S-G    Ignored   Ignored
Filter Events					G	   G	      G 	G      Ignored
Destroy Callback			      D-S-G	 D-S-G	    D-S-G     D-S-G	D-S-G
String Conversion Callback		       S-G	  S-G	     S-G       S-G	 S-G
String Conversion			      D-S-G	 D-S-G	    D-S-G     D-S-G	D-S-G
Reset State				      D-S-G	 D-S-G	    D-S-G     D-S-G    Ignored
HotKey					       S-G	  S-G	     S-G       S-G     Ignored
HotKeyState				      D-S-G	 D-S-G	    D-S-G     D-S-G    Ignored
Preedit
Area				    GS	     Ignored	 D-S-G	    D-S-G    Ignored   Ignored
Area Needed			  GN-GR      Ignored	Ignored      S-G     Ignored   Ignored
Spot Location				     Ignored	 D-S-G	   Ignored   Ignored   Ignored
Colormap				     Ignored	 D-S-G	    D-S-G     D-S-G    Ignored
Foreground				     Ignored	 D-S-G	    D-S-G     D-S-G    Ignored
Background				     Ignored	 D-S-G	    D-S-G     D-S-G    Ignored
Background Pixmap			     Ignored	 D-S-G	    D-S-G     D-S-G    Ignored
Font Set			    GN	     Ignored	 D-S-G	    D-S-G     D-S-G    Ignored
Line Spacing			    GN	     Ignored	 D-S-G	    D-S-G     D-S-G    Ignored
Cursor					     Ignored	 D-S-G	    D-S-G     D-S-G    Ignored
Preedit State				      D-S-G	 D-S-G	    D-S-G     D-S-G    Ignored




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-----------------------------------------------------------------------------------------------
								Input Style
XIC Value			 Geometry    Preedit	Preedit    Preedit   Preedit   Preedit
				Management   Callback	Position    Area     Nothing	None
-----------------------------------------------------------------------------------------------
Preedit State Notify Callback		       S-G	  S-G	     S-G       S-G     Ignored
Preedit Callbacks			      C-S-G	Ignored    Ignored   Ignored   Ignored
-----------------------------------------------------------------------------------------------



------------------------------------------------------------------------
					      Input Style
XIC Value	     Geometry	  Status    Status    Status	Status
		    Management	 Callback    Area     Nothing	 None
------------------------------------------------------------------------
Input Style			   C-G	      C-G	C-G	  C-G
Client Window			   O-G	      O-G	O-G	Ignored
Focus Window		GN	  D-S-G      D-S-G     D-S-G	Ignored
Resource Name			 Ignored     D-S-G     D-S-G	Ignored
Resource Class			 Ignored     D-S-G     D-S-G	Ignored
Geometry Callback		 Ignored     D-S-G    Ignored	Ignored
Filter Events			    G	       G	 G	   G
Status
Area			GS	 Ignored     D-S-G    Ignored	Ignored
Area Needed	      GN-GR	 Ignored      S-G     Ignored	Ignored
Colormap			 Ignored     D-S-G     D-S-G	Ignored
Foreground			 Ignored     D-S-G     D-S-G	Ignored
Background			 Ignored     D-S-G     D-S-G	Ignored
Background Pixmap		 Ignored     D-S-G     D-S-G	Ignored
Font Set		GN	 Ignored     D-S-G     D-S-G	Ignored
Line Spacing		GN	 Ignored     D-S-G     D-S-G	Ignored
Cursor				 Ignored     D-S-G     D-S-G	Ignored
Status Callbacks		  C-S-G     Ignored   Ignored	Ignored
------------------------------------------------------------------------


13.5.6.1.  Input Style

The XNInputStyle argument specifies the input style to be
used.  The value of this argument must be one of the values
returned by the XGetIMValues function with the XNQueryInput-
Style argument specified in the supported_styles list.

Note that this argument must be set at creation time and
cannot be changed.

13.5.6.2.  Client Window

The XNClientWindow argument specifies to the input method
the client window in which the input method can display data
or create subwindows.  Geometry values for input method
areas are given with respect to the client window.  Dynamic
change of client window is not supported.  This argument may



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be set only once and should be set before any input is done
using this input context.  If it is not set, the input
method may not operate correctly.

If an attempt is made to set this value a second time with
XSetICValues, the string XNClientWindow will be returned by
XSetICValues, and the client window will not be changed.

If the client window is not a valid window ID on the display
attached to the input method, a BadWindow error can be gen-
erated when this value is used by the input method.

13.5.6.3.  Focus Window

The XNFocusWindow argument specifies the focus window.	The
primary purpose of the XNFocusWindow is to identify the win-
dow that will receive the key event when input is composed.
In addition, the input method may possibly affect the focus
window as follows:

o    Select events on it

o    Send events to it

o    Modify its properties

o    Grab the keyboard within that window

The associated value must be of type Window.  If the focus
window is not a valid window ID on the display attached to
the input method, a BadWindow error can be generated when
this value is used by the input method.

When this XIC value is left unspecified, the input method
will use the client window as the default focus window.

13.5.6.4.  Resource Name and Class

The XNResourceName and XNResourceClass arguments are strings
that specify the full name and class used by the client to
obtain resources for the client window.  These values should
be used as prefixes for name and class when looking up
resources that may vary according to the input context.  If
these values are not set, the resources will not be fully
specified.

It is not intended that values that can be set as XIC values
be set as resources.

13.5.6.5.  Geometry Callback

The XNGeometryCallback argument is a structure of type XIM-
Callback (see section 13.5.6.13.12).




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The XNGeometryCallback argument specifies the geometry call-
back that a client can set.  This callback is not required
for correct operation of either an input method or a client.
It can be set for a client whose user interface policy per-
mits an input method to request the dynamic change of that
input method's window.	An input method that does dynamic
change will need to filter any events that it uses to initi-
ate the change.

13.5.6.6.  Filter Events

The XNFilterEvents argument returns the event mask that an
input method needs to have selected for.  The client is
expected to augment its own event mask for the client window
with this one.

This argument is read-only, is set by the input method at
create time, and is never changed.

The type of this argument is unsigned long.  Setting this
value will cause an error.

13.5.6.7.  Destroy Callback

The XNDestroyCallback argument is a pointer to a structure
of type XIMCallback (see section 13.5.6.13.12).  This call-
back is triggered when the input method stops its service
for any reason; for example, when a connection to an IM
server is broken.  After the destroy callback is called, the
input context is destroyed and the input method is closed.
Therefore, the client should not call XDestroyIC and XClo-
seIM.


13.5.6.8.  String Conversion Callback

The XNStringConversionCallback argument is a structure of
type XIMCallback (see section 13.5.6.13.12).

The XNStringConversionCallback argument specifies a string
conversion callback.  This callback is not required for cor-
rect operation of either the input method or the client.  It
can be set by a client to support string conversions that
may be requested by the input method.  An input method that
does string conversions will filter any events that it uses
to initiate the conversion.

Because this XIC value is optional, a client should call
XGetIMValues with argument XNQueryICValuesList before using
this argument.







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13.5.6.9.  String Conversion

The XNStringConversion argument is a structure of type XIM-
StringConversionText.

The XNStringConversion argument specifies the string to be
converted by an input method.  This argument is not required
for correct operation of either the input method or the
client.

String conversion facilitates the manipulation of text inde-
pendent of preediting.	It is essential for some input meth-
ods and clients to manipulate text by performing context-
sensitive conversion, reconversion, or transliteration con-
version on it.

Because this XIC value is optional, a client should call
XGetIMValues with argument XNQueryICValuesList before using
this argument.

The XIMStringConversionText structure is defined as follows:

__
|

typedef struct _XIMStringConversionText {
     unsigned short length;
     XIMStringConversionFeedback *feedback;
     Bool encoding_is_wchar;
     union {
	  char *mbs;
	  wchar_t *wcs;
     } string;
} XIMStringConversionText;

typedef unsigned long XIMStringConversionFeedback;

|__

The feedback member is reserved for future use.  The text to
be converted is defined by the string and length members.
The length is indicated in characters.	To prevent the
library from freeing memory pointed to by an uninitialized
pointer, the client should set the feedback element to NULL.


13.5.6.10.  Reset State

The XNResetState argument specifies the state the input con-
text will return to after calling XmbResetIC, XwcResetIC or
Xutf8ResetIC.

The XIC state may be set to its initial state, as specified
by the XNPreeditState value when XCreateIC was called, or it



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may be set to preserve the current state.

The valid masks for XIMResetState are as follows:

__
|

typedef unsigned long XIMResetState;


#define   XIMInitialState	 (1L)
#define   XIMPreserveState	 (1L<<1)

|__

If XIMInitialState is set, then XmbResetIC, XwcResetIC and
Xutf8ResetIC will return to the initial XNPreeditState state
of the XIC.

If XIMPreserveState is set, then XmbResetIC, XwcResetIC and
Xutf8ResetIC will preserve the current state of the XIC.

If XNResetState is left unspecified, the default is XIMIni-
tialState.

XIMResetState values other than those specified above will
default to XIMInitialState.

Because this XIC value is optional, a client should call
XGetIMValues with argument XNQueryICValuesList before using
this argument.


13.5.6.11.  Hot Keys

The XNHotKey argument specifies the hot key list to the XIC.
The hot key list is a pointer to the structure of type
XIMHotKeyTriggers, which specifies the key events that must
be received without any interruption of the input method.
For the hot key list set with this argument to be utilized,
the client must also set XNHotKeyState to XIMHotKeyStateON.

Because this XIC value is optional, a client should call
XGetIMValues with argument XNQueryICValuesList before using
this functionality.

The value of the argument is a pointer to a structure of
type XIMHotKeyTriggers.

If an event for a key in the hot key list is found, then the
process will receive the event and it will be processed
inside the client.





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__
|
typedef struct {
     KeySym keysym;
     unsigned int modifier;
     unsigned int modifier_mask;
} XIMHotKeyTrigger;

typedef struct {
     int num_hot_key;
     XIMHotKeyTrigger *key;
} XIMHotKeyTriggers;

|__


The combination of modifier and modifier_mask are used to
represent one of three states for each modifier: either the
modifier must be on, or the modifier must be off, or the
modifier is a ``don't care'' - it may be on or off.  When a
modifier_mask bit is set to 0, the state of the associated
modifier is ignored when evaluating whether the key is hot
or not.

-----------------------------------------------------------
Modifier Bit   Mask Bit     Meaning
-----------------------------------------------------------
0	       1	    The modifier must be off.
1	       1	    The modifier must be on.
n/a	       0	    Do not care if the modifier is
			    on or off.
-----------------------------------------------------------


13.5.6.12.  Hot Key State

The XNHotKeyState argument specifies the hot key state of
the input method.  This is usually used to switch the input
method between hot key operation and normal input process-
ing.

The value of the argument is a pointer to a structure of
type XIMHotKeyState .

__
|
typedef unsigned long XIMHotKeyState;


#define   XIMHotKeyStateON		   (0x0001L)
#define   XIMHotKeyStateOFF		   (0x0002L)

|__





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If not specified, the default is XIMHotKeyStateOFF.


13.5.6.13.  Preedit and Status Attributes

The XNPreeditAttributes and XNStatusAttributes arguments
specify to an input method the attributes to be used for the
preedit and status areas, if any.  Those attributes are
passed to XSetICValues or XGetICValues as a nested variable-
length list.  The names to be used in these lists are
described in the following sections.

13.5.6.13.1.  Area

The value of the XNArea argument must be a pointer to a
structure of type XRectangle. The interpretation of the
XNArea argument is dependent on the input method style that
has been set.

If the input method style is XIMPreeditPosition, XNArea
specifies the clipping region within which preediting will
take place.  If the focus window has been set, the coordi-
nates are assumed to be relative to the focus window.  Oth-
erwise, the coordinates are assumed to be relative to the
client window.	If neither has been set, the results are
undefined.

If XNArea is not specified, is set to NULL, or is invalid,
the input method will default the clipping region to the
geometry of the XNFocusWindow.	If the area specified is
NULL or invalid, the results are undefined.

If the input style is XIMPreeditArea or XIMStatusArea,
XNArea specifies the geometry provided by the client to the
input method.  The input method may use this area to display
its data, either preedit or status depending on the area
designated.  The input method may create a window as a child
of the client window with dimensions that fit the XNArea.
The coordinates are relative to the client window.  If the
client window has not been set yet, the input method should
save these values and apply them when the client window is
set.  If XNArea is not specified, is set to NULL, or is
invalid, the results are undefined.

13.5.6.13.2.  Area Needed

When set, the XNAreaNeeded argument specifies the geometry
suggested by the client for this area (preedit or status).
The value associated with the argument must be a pointer to
a structure of type XRectangle.  Note that the x, y values
are not used and that nonzero values for width or height are
the constraints that the client wishes the input method to
respect.




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When read, the XNAreaNeeded argument specifies the preferred
geometry desired by the input method for the area.

This argument is only valid if the input style is XIMPreed-
itArea or XIMStatusArea.  It is used for geometry negotia-
tion between the client and the input method and has no
other effect on the input method (see section 13.5.1.5).

13.5.6.13.3.  Spot Location

The XNSpotLocation argument specifies to the input method
the coordinates of the spot to be used by an input method
executing with XNInputStyle set to XIMPreeditPosition.	When
specified to any input method other than XIMPreeditPosition,
this XIC value is ignored.

The x coordinate specifies the position where the next char-
acter would be inserted.  The y coordinate is the position
of the baseline used by the current text line in the focus
window.  The x and y coordinates are relative to the focus
window, if it has been set; otherwise, they are relative to
the client window.  If neither the focus window nor the
client window has been set, the results are undefined.

The value of the argument is a pointer to a structure of
type XPoint.

13.5.6.13.4.  Colormap

Two different arguments can be used to indicate what col-
ormap the input method should use to allocate colors, a col-
ormap ID, or a standard colormap name.

The XNColormap argument is used to specify a colormap ID.
The argument value is of type Colormap.  An invalid argument
may generate a BadColor error when it is used by the input
method.

The XNStdColormap argument is used to indicate the name of
the standard colormap in which the input method should allo-
cate colors.  The argument value is an Atom that should be a
valid atom for calling XGetRGBColormaps.  An invalid argu-
ment may generate a BadAtom error when it is used by the
input method.

If the colormap is left unspecified, the client window col-
ormap becomes the default.

13.5.6.13.5.  Foreground and Background

The XNForeground and XNBackground arguments specify the
foreground and background pixel, respectively.	The argument
value is of type unsigned long.  It must be a valid pixel in
the input method colormap.



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If these values are left unspecified, the default is deter-
mined by the input method.

13.5.6.13.6.  Background Pixmap

The XNBackgroundPixmap argument specifies a background
pixmap to be used as the background of the window.  The
value must be of type Pixmap.  An invalid argument may gen-
erate a BadPixmap error when it is used by the input method.

If this value is left unspecified, the default is determined
by the input method.

13.5.6.13.7.  Font Set

The XNFontSet argument specifies to the input method what
font set is to be used.  The argument value is of type
XFontSet.

If this value is left unspecified, the default is determined
by the input method.

13.5.6.13.8.  Line Spacing

The XNLineSpace argument specifies to the input method what
line spacing is to be used in the preedit window if more
than one line is to be used.  This argument is of type int.

If this value is left unspecified, the default is determined
by the input method.

13.5.6.13.9.  Cursor

The XNCursor argument specifies to the input method what
cursor is to be used in the specified window.  This argument
is of type Cursor.

An invalid argument may generate a BadCursor error when it
is used by the input method.  If this value is left unspeci-
fied, the default is determined by the input method.

13.5.6.13.10.  Preedit State

The XNPreeditState argument specifies the state of input
preediting for the input method.  Input preediting can be on
or off.

The valid mask names for XNPreeditState are as follows:









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__
|

typedef unsigned long XIMPreeditState;


#define   XIMPreeditUnknown	 0L
#define   XIMPreeditEnable	 1L
#define   XIMPreeditDisable	 (1L<<1)

|__

If a value of XIMPreeditEnable is set, then input preediting
is turned on by the input method.

If a value of XIMPreeditDisable is set, then input preedit-
ing is turned off by the input method.

If XNPreeditState is left unspecified, then the state will
be implementation-dependent.

When XNResetState is set to XIMInitialState, the XNPreedit-
State value specified at the creation time will be reflected
as the initial state for XmbResetIC, XwcResetIC and
Xutf8ResetIC.

Because this XIC value is optional, a client should call
XGetIMValues with argument XNQueryICValuesList before using
this argument.

13.5.6.13.11.  Preedit State Notify Callback

The preedit state notify callback is triggered by the input
method when the preediting state has changed.  The value of
the XNPreeditStateNotifyCallback argument is a pointer to a
structure of type XIMCallback.	The generic prototype is as
follows:
__
|
void PreeditStateNotifyCallback(ic, client_data, call_data)
      XIC ic;
      XPointer client_data;
      XIMPreeditStateNotifyCallbackStruct *call_data;


ic	  Specifies the input context.

client_data
	  Specifies the additional client data.

call_data Specifies the current preedit state.
|__

The XIMPreeditStateNotifyCallbackStruct structure is defined
as follows:



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__
|
typedef struct _XIMPreeditStateNotifyCallbackStruct {
     XIMPreeditState state;
} XIMPreeditStateNotifyCallbackStruct;

|__


Because this XIC value is optional, a client should call
XGetIMValues with argument XNQueryICValuesList before using
this argument.

13.5.6.13.12.  Preedit and Status Callbacks

A client that wants to support the input style XIMPreedit-
Callbacks must provide a set of preedit callbacks to the
input method.  The set of preedit callbacks is as follows:

XNPreeditStart-     This is called when the input method
Callback	    starts preedit.
XNPreedit-	    This is called when the input method
DoneCallback	    stops preedit.
XNPreeditDraw-	    This is called when a number of preedit
Callback	    keystrokes should be echoed.
XNPreeditCaret-     This is called to move the text inser-
Callback	    tion point within the preedit string.


A client that wants to support the input style XIMStatus-
Callbacks must provide a set of status callbacks to the
input method.  The set of status callbacks is as follows:

XNStatusStart-	    This is called when the input method
Callback	    initializes the status area.
XNStatusDoneCall-   This is called when the input method no
back		    longer needs the status area.
XNStatusDrawCall-   This is called when updating of the sta-
back		    tus area is required.


The value of any status or preedit argument is a pointer to
a structure of type XIMCallback.















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__
|

typedef void (*XIMProc)();

typedef struct {
     XPointer client_data;
     XIMProc callback;
} XIMCallback;

|__

Each callback has some particular semantics and will carry
the data that expresses the environment necessary to the
client into a specific data structure.	This paragraph only
describes the arguments to be used to set the callback.

Setting any of these values while doing preedit may cause
unexpected results.

13.5.7.  Input Method Callback Semantics

XIM callbacks are procedures defined by clients or text
drawing packages that are to be called from the input method
when selected events occur.  Most clients will use a text
editing package or a toolkit and, hence, will not need to
define such callbacks.	This section defines the callback
semantics, when they are triggered, and what their arguments
are.  This information is mostly useful for X toolkit imple-
mentors.

Callbacks are mostly provided so that clients (or text edit-
ing packages) can implement on-the-spot preediting in their
own window.  In that case, the input method needs to commu-
nicate and synchronize with the client.  The input method
needs to communicate changes in the preedit window when it
is under control of the client.  Those callbacks allow the
client to initialize the preedit area, display a new preedit
string, move the text insertion point during preedit, termi-
nate preedit, or update the status area.

All callback procedures follow the generic prototype:
















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__
|
void CallbackPrototype(ic, client_data, call_data)
      XIC ic;
      XPointer client_data;
      SomeType call_data;


ic	  Specifies the input context.

client_data
	  Specifies the additional client data.

call_data Specifies data specific to the callback.
|__

The call_data argument is a structure that expresses the
arguments needed to achieve the semantics; that is, it is a
specific data structure appropriate to the callback.  In
cases where no data is needed in the callback, this
call_data argument is NULL.  The client_data argument is a
closure that has been initially specified by the client when
specifying the callback and passed back.  It may serve, for
example, to inherit application context in the callback.

The following paragraphs describe the programming semantics
and specific data structure associated with the different
reasons.

13.5.7.1.  Geometry Callback

The geometry callback is triggered by the input method to
indicate that it wants the client to negotiate geometry.
The generic prototype is as follows:
__
|
void GeometryCallback(ic, client_data, call_data)
      XIC ic;
      XPointer client_data;
      XPointer call_data;


ic	  Specifies the input context.

client_data
	  Specifies the additional client data.

call_data Not used for this callback and always passed as
	  NULL.
|__

The callback is called with a NULL call_data argument.






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13.5.7.2.  Destroy Callback

The destroy callback is triggered by the input method when
it stops service for any reason.  After the callback is
invoked, the input context will be freed by Xlib.  The
generic prototype is as follows:
__
|
void DestroyCallback(ic, client_data, call_data)
      XIC ic;
      XPointer client_data;
      XPointer call_data;


ic	  Specifies the input context.

client_data
	  Specifies the additional client data.

call_data Not used for this callback and always passed as
	  NULL.
|__

The callback is called with a NULL call_data argument.

13.5.7.3.  String Conversion Callback

The string conversion callback is triggered by the input
method to request the client to return the string to be con-
verted.  The returned string may be either a multibyte or
wide character string, with an encoding matching the locale
bound to the input context.  The callback prototype is as
follows:
__
|
void StringConversionCallback(ic, client_data, call_data)
      XIC ic;
      XPointer client_data;
      XIMStringConversionCallbackStruct *call_data;


ic	  Specifies the input method.

client_data
	  Specifies the additional client data.

call_data Specifies the amount of the string to be con-
	  verted.
|__

The callback is passed an XIMStringConversionCallbackStruct
structure in the call_data argument.  The text member is an
XIMStringConversionText structure (see section 13.5.6.9) to
be filled in by the client and describes the text to be sent



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to the input method.  The data pointed to by the string and
feedback elements of the XIMStringConversionText structure
will be freed using XFree by the input method after the
callback returns.  So the client should not point to inter-
nal buffers that are critical to the client.  Similarly,
because the feedback element is currently reserved for
future use, the client should set feedback to NULL to pre-
vent the library from freeing memory at some random location
due to an uninitialized pointer.

The XIMStringConversionCallbackStruct structure is defined
as follows:

__
|

typedef struct _XIMStringConversionCallbackStruct {
     XIMStringConversionPosition position;
     XIMCaretDirection direction;
     short factor;
     XIMStringConversionOperation operation;
     XIMStringConversionText *text;
} XIMStringConversionCallbackStruct;

typedef short XIMStringConversionPosition;

typedef unsigned short XIMStringConversionOperation;




#define   XIMStringConversionSubstitu-	   (0x0001)
	  tion
#define   XIMStringConversionRetrieval	   (0x0002)

|__

XIMStringConversionPosition specifies the starting position
of the string to be returned in the XIMStringConversionText
structure.  The value identifies a position, in units of
characters, relative to the client's cursor position in the
client's buffer.

The ending position of the text buffer is determined by the
direction and factor members.  Specifically, it is the char-
acter position relative to the starting point as defined by
the XIMCaretDirection.	The factor member of XIMStringCon-
versionCallbackStruct specifies the number of XIMCaretDirec-
tion positions to be applied.  For example, if the direction
specifies XIMLineEnd and factor is 1, then all characters
from the starting position to the end of the current display
line are returned.  If the direction specifies XIMForward-
Char or XIMBackwardChar, then the factor specifies a rela-
tive position, indicated in characters, from the starting



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position.

XIMStringConversionOperation specifies whether the string to
be converted should be deleted (substitution) or copied
(retrieval) from the client's buffer.  When the XIMString-
ConversionOperation is XIMStringConversionSubstitution, the
client must delete the string to be converted from its own
buffer.  When the XIMStringConversionOperation is XIMString-
ConversionRetrieval, the client must not delete the string
to be converted from its buffer.  The substitute operation
is typically used for reconversion and transliteration con-
version, while the retrieval operation is typically used for
context-sensitive conversion.

13.5.7.4.  Preedit State Callbacks

When the input method turns preediting on or off, a Preedit-
StartCallback or PreeditDoneCallback callback is triggered
to let the toolkit do the setup or the cleanup for the
preedit region.
__
|
int PreeditStartCallback(ic, client_data, call_data)
      XIC ic;
      XPointer client_data;
      XPointer call_data;


ic	  Specifies the input context.

client_data
	  Specifies the additional client data.

call_data Not used for this callback and always passed as
	  NULL.
|__

When preedit starts on the specified input context, the
callback is called with a NULL call_data argument.  Preedit-
StartCallback will return the maximum size of the preedit
string.  A positive number indicates the maximum number of
bytes allowed in the preedit string, and a value of -1 indi-
cates there is no limit.














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__
|
void PreeditDoneCallback(ic, client_data, call_data)
      XIC ic;
      XPointer client_data;
      XPointer call_data;


ic	  Specifies the input context.

client_data
	  Specifies the additional client data.

call_data Not used for this callback and always passed as
	  NULL.
|__

When preedit stops on the specified input context, the call-
back is called with a NULL call_data argument.	The client
can release the data allocated by PreeditStartCallback.

PreeditStartCallback should initialize appropriate data
needed for displaying preedit information and for handling
further PreeditDrawCallback calls.  Once PreeditStartCall-
back is called, it will not be called again before Preedit-
DoneCallback has been called.

13.5.7.5.  Preedit Draw Callback

This callback is triggered to draw and insert, delete or
replace, preedit text in the preedit region.  The preedit
text may include unconverted input text such as Japanese
Kana, converted text such as Japanese Kanji characters, or
characters of both kinds.  That string is either a multibyte
or wide character string, whose encoding matches the locale
bound to the input context.  The callback prototype is as
follows:
__
|
void PreeditDrawCallback(ic, client_data, call_data)
      XIC ic;
      XPointer client_data;
      XIMPreeditDrawCallbackStruct *call_data;


ic	  Specifies the input context.

client_data
	  Specifies the additional client data.

call_data Specifies the preedit drawing information.
|__

The callback is passed an XIMPreeditDrawCallbackStruct
structure in the call_data argument.  The text member of



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this structure contains the text to be drawn.  After the
string has been drawn, the caret should be moved to the
specified location.

The XIMPreeditDrawCallbackStruct structure is defined as
follows:

__
|
typedef struct _XIMPreeditDrawCallbackStruct {
     int caret; 	 /* Cursor offset within preedit string */
     int chg_first;	 /* Starting change position */
     int chg_length;	 /* Length of the change in character count */
     XIMText *text;
} XIMPreeditDrawCallbackStruct;

|__

The client must keep updating a buffer of the preedit text
and the callback arguments referring to indexes in that
buffer.  The call_data fields have specific meanings accord-
ing to the operation, as follows:

o    To indicate text deletion, the call_data member speci-
     fies a NULL text field.  The text to be deleted is then
     the current text in the buffer from position chg_first
     (starting at zero) on a character length of chg_length.

o    When text is non-NULL, it indicates insertion or
     replacement of text in the buffer.

     The chg_length member identifies the number of charac-
     ters in the current preedit buffer that are affected by
     this call.  A positive chg_length indicates that
     chg_length number of characters, starting at chg_first,
     must be deleted or must be replaced by text, whose
     length is specified in the XIMText structure.

     A chg_length value of zero indicates that text must be
     inserted right at the position specified by chg_first.
     A value of zero for chg_first specifies the first char-
     acter in the buffer.

     chg_length and chg_first combine to identify the modi-
     fication required to the preedit buffer; beginning at
     chg_first, replace chg_length number of characters with
     the text in the supplied XIMText structure. For exam-
     ple, suppose the preedit buffer contains the string
     "ABCDE".








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	  Text:      A B C D E
		    ^ ^ ^ ^ ^ ^
	  CharPos:  0 1 2 3 4 5


     The CharPos in the diagram shows the location of the
     character position relative to the character.

     If the value of chg_first is 1 and the value of
     chg_length is 3, this says to replace 3 characters
     beginning at character position 1 with the string in
     the XIMText structure.  Hence, BCD would be replaced by
     the value in the structure.

     Though chg_length and chg_first are both signed inte-
     gers they will never have a negative value.

o    The caret member identifies the character position
     before which the cursor should be placed - after modi-
     fication to the preedit buffer has been completed.  For
     example, if caret is zero, the cursor is at the begin-
     ning of the buffer.  If the caret is one, the cursor is
     between the first and second character.

__
|
     typedef struct _XIMText {
	  unsigned short length;
	  XIMFeedback * feedback;
	  Bool encoding_is_wchar;
	  union {
	       char * multi_byte;
	       wchar_t * wide_char;
	  } string;
     } XIMText;

|__

The text string passed is actually a structure specifying as
follows:

o    The length member is the text length in characters.

o    The encoding_is_wchar member is a value that indicates
     if the text string is encoded in wide character or
     multibyte format.	The text string may be passed either
     as multibyte or as wide character; the input method
     controls in which form data is passed.  The client's
     callback routine must be able to handle data passed in
     either form.

o    The string member is the text string.





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o    The feedback member indicates rendering type for each
     character in the string member.  If string is NULL
     (indicating that only highlighting of the existing
     preedit buffer should be updated), feedback points to
     length highlight elements that should be applied to the
     existing preedit buffer, beginning at chg_first.

The feedback member expresses the types of rendering feed-
back the callback should apply when drawing text.  Rendering
of the text to be drawn is specified either in generic ways
(for example, primary, secondary) or in specific ways
(reverse, underline).  When generic indications are given,
the client is free to choose the rendering style.  It is
necessary, however, that primary and secondary be mapped to
two distinct rendering styles.

If an input method wants to control display of the preedit
string, an input method can indicate the visibility hints
using feedbacks in a specific way.  The XIMVisibleToForward,
XIMVisibleToBackward, and XIMVisibleCenter masks are exclu-
sively used for these visibility hints.  The XIMVisibleTo-
Forward mask indicates that the preedit text is preferably
displayed in the primary draw direction from the caret posi-
tion in the preedit area forward.  The XIMVisibleToBackward
mask indicates that the preedit text is preferably displayed
from the caret position in the preedit area backward, rela-
tive to the primary draw direction.  The XIMVisibleCenter
mask indicates that the preedit text is preferably displayed
with the caret position in the preedit area centered.

The insertion point of the preedit string could exist out-
side of the visible area when visibility hints are used.
Only one of the masks is valid for the entire preedit
string, and only one character can hold one of these feed-
backs for a given input context at one time.  This feedback
may be OR'ed together with another highlight (such as XIMRe-
verse).  Only the most recently set feedback is valid, and
any previous feedback is automatically canceled.  This is a
hint to the client, and the client is free to choose how to
display the preedit string.

The feedback member also specifies how rendering of the text
argument should be performed.  If the feedback is NULL, the
callback should apply the same feedback as is used for the
surrounding characters in the preedit buffer; if chg_first
is at a highlight boundary, the client can choose which of
the two highlights to use.  If feedback is not NULL, feed-
back specifies an array defining the rendering for each
character of the string, and the length of the array is thus
length.

If an input method wants to indicate that it is only updat-
ing the feedback of the preedit text without changing the
content of it, the XIMText structure will contain a NULL



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value for the string field, the number of characters
affected (relative to chg_first) will be in the length
field, and the feedback field will point to an array of XIM-
Feedback.

Each element in the feedback array is a bitmask represented
by a value of type XIMFeedback.  The valid mask names are as
follows:

__
|

typedef unsigned long XIMFeedback;


#define   XIMReverse		 1L
#define   XIMUnderline		 (1L<<1)
#define   XIMHighlight		 (1L<<2)
#define   XIMPrimary		 (1L<<5)
#define   XIMSecondary		 (1L<<6)
#define   XIMTertiary		 (1L<<7)
#define   XIMVisibleToForward	 (1L<<8)
#define   XIMVisibleToBackward	 (1L<<9)
#define   XIMVisibleCenter	 (1L<<10)

|__


Characters drawn with the XIMReverse highlight should be
drawn by swapping the foreground and background colors used
to draw normal, unhighlighted characters.  Characters drawn
with the XIMUnderline highlight should be underlined.  Char-
acters drawn with the XIMHighlight, XIMPrimary, XIMSec-
ondary, and XIMTertiary highlights should be drawn in some
unique manner that must be different from XIMReverse and
XIMUnderline.

13.5.7.6.  Preedit Caret Callback

An input method may have its own navigation keys to allow
the user to move the text insertion point in the preedit
area (for example, to move backward or forward).  Conse-
quently, input method needs to indicate to the client that
it should move the text insertion point.  It then calls the
PreeditCaretCallback.
-----------
   The values for XIMPrimary, XIMSecondary, and
XIMTertiary were incorrectly defined in the R5
specification.	The X Consortium's X11R5 implemen-
tation correctly implemented the values for these
highlights.  The value of these highlights has
been corrected in this specification to agree with
the values in the Consortium's X11R5 and X11R6
implementations.



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__
|
void PreeditCaretCallback(ic, client_data, call_data)
      XIC ic;
      XPointer client_data;
      XIMPreeditCaretCallbackStruct *call_data;


ic	  Specifies the input context.

client_data
	  Specifies the additional client data.

call_data Specifies the preedit caret information.
|__

The input method will trigger PreeditCaretCallback to move
the text insertion point during preedit.  The call_data
argument contains a pointer to an XIMPreeditCaretCallback-
Struct structure, which indicates where the caret should be
moved.	The callback must move the insertion point to its
new location and return, in field position, the new offset
value from the initial position.

The XIMPreeditCaretCallbackStruct structure is defined as
follows:

__
|
typedef struct _XIMPreeditCaretCallbackStruct {
     int position;	 /* Caret offset within preedit string */
     XIMCaretDirection direction;/* Caret moves direction */
     XIMCaretStyle style;/* Feedback of the caret */
} XIMPreeditCaretCallbackStruct;

|__

The XIMCaretStyle structure is defined as follows:

__
|
typedef enum {
     XIMIsInvisible,	 /* Disable caret feedback */
     XIMIsPrimary,	 /* UI defined caret feedback */
     XIMIsSecondary,	 /* UI defined caret feedback */
} XIMCaretStyle;

|__

The XIMCaretDirection structure is defined as follows:








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__
|
typedef enum {
     XIMForwardChar, XIMBackwardChar,
     XIMForwardWord, XIMBackwardWord,
     XIMCaretUp, XIMCaretDown,
     XIMNextLine, XIMPreviousLine,
     XIMLineStart, XIMLineEnd,
     XIMAbsolutePosition,
     XIMDontChange,
 } XIMCaretDirection;

|__

These values are defined as follows:

XIMForwardChar	  Move the caret forward one character posi-
		  tion.
XIMBackwardChar   Move the caret backward one character
		  position.
XIMForwardWord	  Move the caret forward one word.
XIMBackwardWord   Move the caret backward one word.
XIMCaretUp	  Move the caret up one line keeping the
		  current horizontal offset.
XIMCaretDown	  Move the caret down one line keeping the
		  current horizontal offset.
XIMPreviousLine   Move the caret to the beginning of the
		  previous line.
XIMNextLine	  Move the caret to the beginning of the
		  next line.
XIMLineStart	  Move the caret to the beginning of the
		  current display line that contains the
		  caret.
XIMLineEnd	  Move the caret to the end of the current
		  display line that contains the caret.
XIMAbsolutePo-	  The callback must move to the location
sition		  specified by the position field of the
		  callback data, indicated in characters,
		  starting from the beginning of the preedit
		  text.  Hence, a value of zero means move
		  back to the beginning of the preedit text.
XIMDontChange	  The caret position does not change.


13.5.7.7.  Status Callbacks

An input method may communicate changes in the status of an
input context (for example, created, destroyed, or focus
changes) with three status callbacks:  StatusStartCallback,
StatusDoneCallback, and StatusDrawCallback.


When the input context is created or gains focus, the input
method calls the StatusStartCallback callback.




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__
|
void StatusStartCallback(ic, client_data, call_data)
      XIC ic;
      XPointer client_data;
      XPointer call_data;


ic	  Specifies the input context.

client_data
	  Specifies the additional client data.

call_data Not used for this callback and always passed as
	  NULL.
|__

The callback should initialize appropriate data for display-
ing status and for responding to StatusDrawCallback calls.
Once StatusStartCallback is called, it will not be called
again before StatusDoneCallback has been called.


When an input context is destroyed or when it loses focus,
the input method calls StatusDoneCallback.
__
|
void StatusDoneCallback(ic, client_data, call_data)
      XIC ic;
      XPointer client_data;
      XPointer call_data;


ic	  Specifies the input context.

client_data
	  Specifies the additional client data.

call_data Not used for this callback and always passed as
	  NULL.
|__

The callback may release any data allocated on StatusStart.


When an input context status has to be updated, the input
method calls StatusDrawCallback.











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__
|
void StatusDrawCallback(ic, client_data, call_data)
      XIC ic;
      XPointer client_data;
      XIMStatusDrawCallbackStruct *call_data;


ic	  Specifies the input context.

client_data
	  Specifies the additional client data.

call_data Specifies the status drawing information.
|__

The callback should update the status area by either drawing
a string or imaging a bitmap in the status area.

The XIMStatusDataType and XIMStatusDrawCallbackStruct struc-
tures are defined as follows:

__
|
typedef enum {
     XIMTextType,
     XIMBitmapType,
} XIMStatusDataType;

typedef struct _XIMStatusDrawCallbackStruct {
     XIMStatusDataType type;
     union {
	  XIMText *text;
	  Pixmap  bitmap;
     } data;
} XIMStatusDrawCallbackStruct;

|__


The feedback styles XIMVisibleToForward, XIMVisibleToBack-
ward, and XIMVisibleToCenter are not relevant and will not
appear in the XIMFeedback element of the XIMText structure.


13.5.8.  Event Filtering

Xlib provides the ability for an input method to register a
filter internal to Xlib.  This filter is called by a client
(or toolkit) by calling XFilterEvent after calling XNex-
tEvent.  Any client that uses the XIM interface should call
XFilterEvent to allow input methods to process their events
without knowledge of the client's dispatching mechanism.  A
client's user interface policy may determine the priority of
event filters with respect to other event-handling



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mechanisms (for example, modal grabs).

Clients may not know how many filters there are, if any, and
what they do.  They may only know if an event has been fil-
tered on return of XFilterEvent.  Clients should discard
filtered events.


To filter an event, use XFilterEvent.
__
|
Bool XFilterEvent(event, w)
      XEvent *event;
      Window w;


event	  Specifies the event to filter.

w	  Specifies the window for which the filter is to be
	  applied.
|__

If the window argument is None, XFilterEvent applies the
filter to the window specified in the XEvent structure.  The
window argument is provided so that layers above Xlib that
do event redirection can indicate to which window an event
has been redirected.

If XFilterEvent returns True, then some input method has
filtered the event, and the client should discard the event.
If XFilterEvent returns False, then the client should con-
tinue processing the event.

If a grab has occurred in the client and XFilterEvent
returns True, the client should ungrab the keyboard.

13.5.9.  Getting Keyboard Input

To get composed input from an input method, use XmbLookup-
String, XwcLookupString or Xutf8LookupString.

















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__
|
int XmbLookupString(ic, event, buffer_return, bytes_buffer, keysym_return, status_return)
      XIC ic;
      XKeyPressedEvent *event;
      char *buffer_return;
      int bytes_buffer;
      KeySym *keysym_return;
      Status *status_return;


int XwcLookupString(ic, event, buffer_return, bytes_buffer, keysym_return, status_return)
      XIC ic;
      XKeyPressedEvent *event;
      wchar_t *buffer_return;
      int wchars_buffer;
      KeySym *keysym_return;
      Status *status_return;


int Xutf8LookupString(ic, event, buffer_return, bytes_buffer, keysym_return, status_return)
      XIC ic;
      XKeyPressedEvent *event;
      char *buffer_return;
      int bytes_buffer;
      KeySym *keysym_return;
      Status *status_return;


ic	  Specifies the input context.

event	  Specifies the key event to be used.

buffer_return
	  Returns a multibyte string or wide character
	  string (if any) from the input method.

bytes_buffer
wchars_buffer
	  Specifies space available in the return buffer.

keysym_return
	  Returns the KeySym computed from the event if this
	  argument is not NULL.

status_return
	  Returns a value indicating what kind of data is
	  returned.
|__

The XmbLookupString, XwcLookupString and Xutf8LookupString
functions return the string from the input method specified
in the buffer_return argument.	If no string is returned,
the buffer_return argument is unchanged.




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The KeySym into which the KeyCode from the event was mapped
is returned in the keysym_return argument if it is non-NULL
and the status_return argument indicates that a KeySym was
returned.  If both a string and a KeySym are returned, the
KeySym value does not necessarily correspond to the string
returned.

XmbLookupString and Xutf8LookupString return the length of
the string in bytes, and XwcLookupString returns the length
of the string in characters.  Both XmbLookupString and
XwcLookupString return text in the encoding of the locale
bound to the input method of the specified input context,
and Xutf8LookupString returns text in UTF-8 encoding.

Each string returned by XmbLookupString and XwcLookupString
begins in the initial state of the encoding of the locale
(if the encoding of the locale is state-dependent).

			    Note

     To ensure proper input processing, it is essential
     that the client pass only KeyPress events to
     XmbLookupString, XwcLookupString and Xutf8Lookup-
     String.  Their behavior when a client passes a
     KeyRelease event is undefined.


Clients should check the status_return argument before using
the other returned values.  These three functions each
return a value to status_return that indicates what has been
returned in the other arguments.  The possible values
returned are:

XBufferOverflow   The input string to be returned is too
		  large for the supplied buffer_return.  The
		  required size (for XmbLookupString,
		  Xutf8LookupString in bytes; for XwcLookup-
		  String in characters) is returned as the
		  value of the function, and the contents of
		  buffer_return and keysym_return are not
		  modified.  The client should recall the
		  function with the same event and a buffer
		  of adequate size to obtain the string.
XLookupNone	  No consistent input has been composed so
		  far.	The contents of buffer_return and
		  keysym_return are not modified, and the
		  function returns zero.
XLookupChars	  Some input characters have been composed.
		  They are placed in the buffer_return argu-
		  ment, using the encoding described above,
		  and the string length is returned as the
		  value of the function.  The content of the
		  keysym_return argument is not modified.




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XLookupKeySym	  A KeySym has been returned instead of a
		  string and is returned in keysym_return.
		  The content of the buffer_return argument
		  is not modified, and the function returns
		  zero.
XLookupBoth	  Both a KeySym and a string are returned;
		  XLookupChars and XLookupKeySym occur simul-
		  taneously.


It does not make any difference if the input context passed
as an argument to XmbLookupString, XwcLookupString and
Xutf8LookupString is the one currently in possession of the
focus or not.  Input may have been composed within an input
context before it lost the focus, and that input may be
returned on subsequent calls to XmbLookupString, XwcLookup-
String or Xutf8LookupString even though it does not have any
more keyboard focus.

The function Xutf8LookupString is an XFree86 extension
introduced in XFree86 4.0.2. Its presence is indicated by
the macro X_HAVE_UTF8_STRING.

13.5.10.  Input Method Conventions

The input method architecture is transparent to the client.
However, clients should respect a number of conventions in
order to work properly.  Clients must also be aware of pos-
sible effects of synchronization between input method and
library in the case of a remote input server.

13.5.10.1.  Client Conventions

A well-behaved client (or toolkit) should first query the
input method style.  If the client cannot satisfy the
requirements of the supported styles (in terms of geometry
management or callbacks), it should negotiate with the user
continuation of the program or raise an exception or error
of some sort.

13.5.10.2.  Synchronization Conventions

A KeyPress event with a KeyCode of zero is used exclusively
as a signal that an input method has composed input that can
be returned by XmbLookupString, XwcLookupString or
Xutf8LookupString.  No other use is made of a KeyPress event
with KeyCode of zero.

Such an event may be generated by either a front-end or a
back-end input method in an implementation-dependent manner.
Some possible ways to generate this event include:

o    A synthetic event sent by an input method server




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o    An artificial event created by a input method filter
     and pushed onto a client's event queue

o    A KeyPress event whose KeyCode value is modified by an
     input method filter

When callback support is specified by the client, input
methods will not take action unless they explicitly called
back the client and obtained no response (the callback is
not specified or returned invalid data).

13.6.  String Constants

The following symbols for string constants are defined in
<X11/Xlib.h>.  Although they are shown here with particular
macro definitions, they may be implemented as macros, as
global symbols, or as a mixture of the two.  The string
pointer value itself is not significant; clients must not
assume that inequality of two values implies inequality of
the actual string data.

#define   XNVaNestedList		"XNVaNestedList"
#define   XNSeparatorofNestedList	"separatorofNestedList"
#define   XNQueryInputStyle		"queryInputStyle"
#define   XNClientWindow		"clientWindow"
#define   XNInputStyle			"inputStyle"
#define   XNFocusWindow 		"focusWindow"
#define   XNResourceName		"resourceName"
#define   XNResourceClass		"resourceClass"
#define   XNGeometryCallback		"geometryCallback"
#define   XNDestroyCallback		"destroyCallback"
#define   XNFilterEvents		"filterEvents"
#define   XNPreeditStartCallback	"preeditStartCallback"
#define   XNPreeditDoneCallback 	"preeditDoneCallback"
#define   XNPreeditDrawCallback 	"preeditDrawCallback"
#define   XNPreeditCaretCallback	"preeditCaretCallback"
#define   XNPreeditStateNotifyCall-	"preeditStateNotifyCall-
	  back				back"
#define   XNPreeditAttributes		"preeditAttributes"

#define   XNStatusStartCallback 	"statusStartCallback"
#define   XNStatusDoneCallback		"statusDoneCallback"
#define   XNStatusDrawCallback		"statusDrawCallback"
#define   XNStatusAttributes		"statusAttributes"
#define   XNArea			"area"
#define   XNAreaNeeded			"areaNeeded"
#define   XNSpotLocation		"spotLocation"
#define   XNColormap			"colorMap"
#define   XNStdColormap 		"stdColorMap"
#define   XNForeground			"foreground"
#define   XNBackground			"background"
#define   XNBackgroundPixmap		"backgroundPixmap"
#define   XNFontSet			"fontSet"




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#define   XNLineSpace			"lineSpace"
#define   XNCursor			"cursor"

#define   XNQueryIMValuesList		"queryIMValuesList"
#define   XNQueryICValuesList		"queryICValuesList"
#define   XNStringConversionCallback	"stringConversionCall-
					back"
#define   XNStringConversion		"stringConversion"
#define   XNResetState			"resetState"
#define   XNHotKey			"hotkey"
#define   XNHotKeyState 		"hotkeyState"
#define   XNPreeditState		"preeditState"
#define   XNVisiblePosition		"visiblePosition"
#define   XNR6PreeditCallbackBehavior	"r6PreeditCallback"

#define   XNRequiredCharSet		"requiredCharSet"
#define   XNQueryOrientation		"queryOrientation"
#define   XNDirectionalDependentDraw-	"directionalDependent-
	  ing				Drawing"
#define   XNContextualDrawing		"contextualDrawing"
#define   XNBaseFontName		"baseFontName"
#define   XNMissingCharSet		"missingCharSet"
#define   XNDefaultString		"defaultString"
#define   XNOrientation 		"orientation"
#define   XNFontInfo			"fontInfo"
#define   XNOMAutomatic 		"omAutomatic"































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			 Chapter 14

	    Inter-Client Communication Functions



The Inter-Client Communication Conventions Manual, hereafter
referred to as the ICCCM, details the X Consortium approved
conventions that govern inter-client communications.  These
conventions ensure peer-to-peer client cooperation in the
use of selections, cut buffers, and shared resources as well
as client cooperation with window and session managers.  For
further information, see the Inter-Client Communication Con-
ventions Manual.

Xlib provides a number of standard properties and program-
ming interfaces that are ICCCM compliant.  The predefined
atoms for some of these properties are defined in the
<X11/Xatom.h> header file, where to avoid name conflicts
with user symbols their #define name has an XA_ prefix.  For
further information about atoms and properties, see section
4.3.

Xlib's selection and cut buffer mechanisms provide the pri-
mary programming interfaces by which peer client applica-
tions communicate with each other (see sections 4.5 and
16.6).	The functions discussed in this chapter provide the
primary programming interfaces by which client applications
communicate with their window and session managers as well
as share standard colormaps.

The standard properties that are of special interest for
communicating with window and session managers are:

-----------------------------------------------------------------------
Name		       Type	       Format	Description
-----------------------------------------------------------------------
WM_CLASS	       STRING		 8	Set by application
						programs to allow win-
						dow and session man-
						agers to obtain the
						application's
						resources from the
						resource database.
WM_CLIENT_MACHINE      TEXT			The string name of the
						machine on which the
						client application is
						running.







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-----------------------------------------------------------------------
Name		       Type	       Format	Description
-----------------------------------------------------------------------
WM_COLORMAP_WINDOWS    WINDOW		 32	The list of window IDs
						that may need a dif-
						ferent colormap from
						that of their top-
						level window.
WM_COMMAND	       TEXT			The command and argu-
						ments, null-separated,
						used to invoke the
						application.
WM_HINTS	       WM_HINTS 	 32	Additional hints set
						by the client for use
						by the window manager.
						The C type of this
						property is XWMHints.
WM_ICON_NAME	       TEXT			The name to be used in
						an icon.
WM_ICON_SIZE	       WM_ICON_SIZE	 32	The window manager may
						set this property on
						the root window to
						specify the icon sizes
						it supports.  The C
						type of this property
						is XIconSize.
WM_NAME 	       TEXT			The name of the appli-
						cation.
WM_NORMAL_HINTS        WM_SIZE_HINTS	 32	Size hints for a win-
						dow in its normal
						state.	The C type of
						this property is
						XSizeHints.
WM_PROTOCOLS	       ATOM		 32	List of atoms that
						identify the communi-
						cations protocols
						between the client and
						window manager in
						which the client is
						willing to partici-
						pate.
WM_STATE	       WM_STATE 	 32	Intended for communi-
						cation between window
						and session managers
						only.
WM_TRANSIENT_FOR       WINDOW		 32	Set by application
						programs to indicate
						to the window manager
						that a transient top-
						level window, such as
						a dialog box.
-----------------------------------------------------------------------





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The remainder of this chapter discusses:

o    Client to window manager communication

o    Client to session manager communication

o    Standard colormaps

14.1.  Client to Window Manager Communication

This section discusses how to:

o    Manipulate top-level windows

o    Convert string lists

o    Set and read text properties

o    Set and read the WM_NAME property

o    Set and read the WM_ICON_NAME property

o    Set and read the WM_HINTS property

o    Set and read the WM_NORMAL_HINTS property

o    Set and read the WM_CLASS property

o    Set and read the WM_TRANSIENT_FOR property

o    Set and read the WM_PROTOCOLS property

o    Set and read the WM_COLORMAP_WINDOWS property

o    Set and read the WM_ICON_SIZE property

o    Use window manager convenience functions

14.1.1.  Manipulating Top-Level Windows

Xlib provides functions that you can use to change the visi-
bility or size of top-level windows (that is, those that
were created as children of the root window).  Note that the
subwindows that you create are ignored by window managers.
Therefore, you should use the basic window functions
described in chapter 3 to manipulate your application's sub-
windows.

To request that a top-level window be iconified, use XIconi-
fyWindow.







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__
|
Status XIconifyWindow(display, w, screen_number)
      Display *display;
      Window w;
      int screen_number;


display   Specifies the connection to the X server.

w	  Specifies the window.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

The XIconifyWindow function sends a WM_CHANGE_STATE
ClientMessage event with a format of 32 and a first data
element of IconicState (as described in section 4.1.4 of the
Inter-Client Communication Conventions Manual) and a window
of w to the root window of the specified screen with an
event mask set to SubstructureNotifyMask| SubstructureRedi-
rectMask.  Window managers may elect to receive this message
and if the window is in its normal state, may treat it as a
request to change the window's state from normal to iconic.
If the WM_CHANGE_STATE property cannot be interned, XIconi-
fyWindow does not send a message and returns a zero status.
It returns a nonzero status if the client message is sent
successfully; otherwise, it returns a zero status.


To request that a top-level window be withdrawn, use XWith-
drawWindow.
__
|
Status XWithdrawWindow(display, w, screen_number)
      Display *display;
      Window w;
      int screen_number;


display   Specifies the connection to the X server.

w	  Specifies the window.

screen_number
	  Specifies the appropriate screen number on the
	  host server.
|__

The XWithdrawWindow function unmaps the specified window and
sends a synthetic UnmapNotify event to the root window of
the specified screen.  Window managers may elect to receive
this message and may treat it as a request to change the



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window's state to withdrawn.  When a window is in the with-
drawn state, neither its normal nor its iconic representa-
tions is visible.  It returns a nonzero status if the Unmap-
Notify event is successfully sent; otherwise, it returns a
zero status.

XWithdrawWindow can generate a BadWindow error.


To request that a top-level window be reconfigured, use XRe-
configureWMWindow.
__
|
Status XReconfigureWMWindow(display, w, screen_number, value_mask, values)
      Display *display;
      Window w;
      int screen_number;
      unsigned int value_mask;
      XWindowChanges *values;


display   Specifies the connection to the X server.

w	  Specifies the window.

screen_number
	  Specifies the appropriate screen number on the
	  host server.

value_mask
	  Specifies which values are to be set using infor-
	  mation in the values structure.  This mask is the
	  bitwise inclusive OR of the valid configure window
	  values bits.

values	  Specifies the XWindowChanges structure.
|__

The XReconfigureWMWindow function issues a ConfigureWindow
request on the specified top-level window.  If the stacking
mode is changed and the request fails with a BadMatch error,
the error is trapped by Xlib and a synthetic Configur-
eRequestEvent containing the same configuration parameters
is sent to the root of the specified window.  Window man-
agers may elect to receive this event and treat it as a
request to reconfigure the indicated window.  It returns a
nonzero status if the request or event is successfully sent;
otherwise, it returns a zero status.

XReconfigureWMWindow can generate BadValue and BadWindow
errors.






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14.1.2.  Converting String Lists

Many of the text properties allow a variety of types and
formats.  Because the data stored in these properties are
not simple null-terminated strings, an XTextProperty struc-
ture is used to describe the encoding, type, and length of
the text as well as its value.	The XTextProperty structure
contains:
__
|
typedef struct {
     unsigned char *value;/* property data */
     Atom encoding;	 /* type of property */
     int format;	 /* 8, 16, or 32 */
     unsigned long nitems;/* number of items in value */
} XTextProperty;

|__

Xlib provides functions to convert localized text to or from
encodings that support the inter-client communication con-
ventions for text.  In addition, functions are provided for
converting between lists of pointers to character strings
and text properties in the STRING encoding.

The functions for localized text return a signed integer
error status that encodes Success as zero, specific error
conditions as negative numbers, and partial conversion as a
count of unconvertible characters.

__
|
#define   XNoMemory		 -1
#define   XLocaleNotSupported	 -2
#define   XConverterNotFound	 -3


typedef enum {
     XStringStyle,	 /* STRING */
     XCompoundTextStyle, /* COMPOUND_TEXT */
     XTextStyle,	 /* text in owner's encoding (current locale) */
     XStdICCTextStyle,	 /* STRING, else COMPOUND_TEXT */
     XUTF8StringStyle	 /* UTF8_STRING */
} XICCEncodingStyle;

|__

The value XUTF8StringStyle is an XFree86 extension intro-
duced in XFree86 4.0.2. Its presence is indicated by the
macro X_HAVE_UTF8_STRING.


To convert a list of text strings to an XTextProperty struc-
ture, use XmbTextListToTextProperty,



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XwcTextListToTextProperty or Xutf8TextListToTextProperty.
__
|
int XmbTextListToTextProperty(display, list, count, style, text_prop_return)
      Display *display;
      char **list;
      int count;
      XICCEncodingStyle style;
      XTextProperty *text_prop_return;


int XwcTextListToTextProperty(display, list, count, style, text_prop_return)
      Display *display;
      wchar_t **list;
      int count;
      XICCEncodingStyle style;
      XTextProperty *text_prop_return;


int Xutf8TextListToTextProperty(display, list, count, style, text_prop_return)
      Display *display;
      char **list;
      int count;
      XICCEncodingStyle style;
      XTextProperty *text_prop_return;


display   Specifies the connection to the X server.

list	  Specifies a list of null-terminated character
	  strings.

count	  Specifies the number of strings specified.

style	  Specifies the manner in which the property is
	  encoded.

text_prop_return
	  Returns the XTextProperty structure.
|__

The XmbTextListToTextProperty, XwcTextListToTextProperty and
Xutf8TextListToTextProperty functions set the specified
XTextProperty value to a set of null-separated elements rep-
resenting the concatenation of the specified list of null-
terminated text strings. The input text strings must be
given in the current locale encoding (for XmbTextListTo-
TextProperty and XwcTextListToTextProperty), or in UTF-8
encoding (for Xutf8TextListToTextProperty).

The functions set the encoding field of text_prop_return to
an Atom for the specified display naming the encoding deter-
mined by the specified style and convert the specified text
list to this encoding for storage in the text_prop_return



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value field.  If the style XStringStyle or XCompound-
TextStyle is specified, this encoding is ``STRING'' or
``COMPOUND_TEXT'', respectively.  If the style
XUTF8StringStyle is specified, this encoding is
``UTF8_STRING''. (This is an XFree86 extension introduced in
XFree86 4.0.2. Its presence is indicated by the macro
X_HAVE_UTF8_STRING.)  If the style XTextStyle is specified,
this encoding is the encoding of the current locale.  If the
style XStdICCTextStyle is specified, this encoding is
``STRING'' if the text is fully convertible to STRING, else
``COMPOUND_TEXT''.  A final terminating null byte is stored
at the end of the value field of text_prop_return but is not
included in the nitems member.

If insufficient memory is available for the new value
string, the functions return XNoMemory.  If the current
locale is not supported, the functions return XLocaleNotSup-
ported.  In both of these error cases, the functions do not
set text_prop_return.

To determine if the functions are guaranteed not to return
XLocaleNotSupported, use XSupportsLocale.

If the supplied text is not fully convertible to the speci-
fied encoding, the functions return the number of unconvert-
ible characters.  Each unconvertible character is converted
to an implementation-defined and encoding-specific default
string.  Otherwise, the functions return Success.  Note that
full convertibility to all styles except XStringStyle is
guaranteed.

To free the storage for the value field, use XFree.

The function Xutf8TextListToTextProperty is an XFree86
extension introduced in XFree86 4.0.2. Its presence is indi-
cated by the macro X_HAVE_UTF8_STRING.


To obtain a list of text strings from an XTextProperty
structure, use XmbTextPropertyToTextList, XwcTextPropertyTo-
TextList or Xutf8TextPropertyToTextList.
















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__
|
int XmbTextPropertyToTextList(display, text_prop, list_return, count_return)
      Display *display;
      XTextProperty *text_prop;
      char ***list_return;
      int *count_return;


int XwcTextPropertyToTextList(display, text_prop, list_return, count_return)
      Display *display;
      XTextProperty *text_prop;
      wchar_t ***list_return;
      int *count_return;


int Xutf8TextPropertyToTextList(display, text_prop, list_return, count_return)
      Display *display;
      XTextProperty *text_prop;
      char ***list_return;
      int *count_return;


display   Specifies the connection to the X server.

text_prop Specifies the XTextProperty structure to be used.

list_return
	  Returns a list of null-terminated character
	  strings.

count_return
	  Returns the number of strings.
|__

The XmbTextPropertyToTextList, XwcTextPropertyToTextList and
Xutf8TextPropertyToTextList functions return a list of text
strings representing the null-separated elements of the
specified XTextProperty structure. The returned strings are
encoded using the current locale encoding (for XmbTextProp-
ertyToTextList and XwcTextPropertyToTextList) or in UTF-8
(for Xutf8TextPropertyToTextList).  The data in text_prop
must be format 8.

Multiple elements of the property (for example, the strings
in a disjoint text selection) are separated by a null byte.
The contents of the property are not required to be null-
terminated; any terminating null should not be included in
text_prop.nitems.

If insufficient memory is available for the list and its
elements, XmbTextPropertyToTextList, XwcTextPropertyTo-
TextList and Xutf8TextPropertyToTextList return XNoMemory.
If the current locale is not supported, the functions return
XLocaleNotSupported.  Otherwise, if the encoding field of



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text_prop is not convertible to the encoding of the current
locale, the functions return XConverterNotFound.  For sup-
ported locales, existence of a converter from COMPOUND_TEXT,
STRING, UTF8_STRING or the encoding of the current locale is
guaranteed if XSupportsLocale returns True for the current
locale (but the actual text may contain unconvertible char-
acters).  Conversion of other encodings is implementation-
dependent.  In all of these error cases, the functions do
not set any return values.

Otherwise, XmbTextPropertyToTextList, XwcTextPropertyTo-
TextList and Xutf8TextPropertyToTextList return the list of
null-terminated text strings to list_return and the number
of text strings to count_return.

If the value field of text_prop is not fully convertible to
the encoding of the current locale, the functions return the
number of unconvertible characters.  Each unconvertible
character is converted to a string in the current locale
that is specific to the current locale.  To obtain the value
of this string, use XDefaultString.  Otherwise, XmbTextProp-
ertyToTextList, XwcTextPropertyToTextList and Xutf8TextProp-
ertyToTextList return Success.

To free the storage for the list and its contents returned
by XmbTextPropertyToTextList or Xutf8TextPropertyToTextList,
use XFreeStringList.  To free the storage for the list and
its contents returned by XwcTextPropertyToTextList, use
XwcFreeStringList.

The function Xutf8TextPropertyToTextList is an XFree86
extension introduced in XFree86 4.0.2. Its presence is indi-
cated by the macro X_HAVE_UTF8_STRING.


To free the in-memory data associated with the specified
wide character string list, use XwcFreeStringList.
__
|
void XwcFreeStringList(list)
      wchar_t **list;


list	  Specifies the list of strings to be freed.
|__

The XwcFreeStringList function frees memory allocated by
XwcTextPropertyToTextList.


To obtain the default string for text conversion in the cur-
rent locale, use XDefaultString.





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__
|
char *XDefaultString()

|__

The XDefaultString function returns the default string used
by Xlib for text conversion (for example, in XmbTextProper-
tyToTextList).	The default string is the string in the cur-
rent locale that is output when an unconvertible character
is found during text conversion.  If the string returned by
XDefaultString is the empty string (""), no character is
output in the converted text.  XDefaultString does not
return NULL.

The string returned by XDefaultString is independent of the
default string for text drawing; see XCreateFontSet to
obtain the default string for an XFontSet.

The behavior when an invalid codepoint is supplied to any
Xlib function is undefined.

The returned string is null-terminated.  It is owned by Xlib
and should not be modified or freed by the client.  It may
be freed after the current locale is changed.  Until freed,
it will not be modified by Xlib.


To set the specified list of strings in the STRING encoding
to a XTextProperty structure, use XStringListToTextProperty.
__
|
Status XStringListToTextProperty(list, count, text_prop_return)
      char **list;
      int count;
      XTextProperty *text_prop_return;


list	  Specifies a list of null-terminated character
	  strings.

count	  Specifies the number of strings.

text_prop_return
	  Returns the XTextProperty structure.
|__

The XStringListToTextProperty function sets the specified
XTextProperty to be of type STRING (format 8) with a value
representing the concatenation of the specified list of
null-separated character strings.  An extra null byte (which
is not included in the nitems member) is stored at the end
of the value field of text_prop_return.  The strings are
assumed (without verification) to be in the STRING encoding.
If insufficient memory is available for the new value



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string, XStringListToTextProperty does not set any fields in
the XTextProperty structure and returns a zero status.	Oth-
erwise, it returns a nonzero status.  To free the storage
for the value field, use XFree.


To obtain a list of strings from a specified XTextProperty
structure in the STRING encoding, use XTextProperty-
ToStringList.
__
|
Status XTextPropertyToStringList(text_prop, list_return, count_return)
       XTextProperty *text_prop;
       char ***list_return;
       int *count_return;


text_prop Specifies the XTextProperty structure to be used.

list_return
	  Returns a list of null-terminated character
	  strings.

count_return
	  Returns the number of strings.
|__

The XTextPropertyToStringList function returns a list of
strings representing the null-separated elements of the
specified XTextProperty structure.  The data in text_prop
must be of type STRING and format 8.  Multiple elements of
the property (for example, the strings in a disjoint text
selection) are separated by NULL (encoding 0).	The contents
of the property are not null-terminated.  If insufficient
memory is available for the list and its elements,
XTextPropertyToStringList sets no return values and returns
a zero status.	Otherwise, it returns a nonzero status.  To
free the storage for the list and its contents, use
XFreeStringList.


To free the in-memory data associated with the specified
string list, use XFreeStringList.
__
|
void XFreeStringList(list)
      char **list;


list	  Specifies the list of strings to be freed.
|__

The XFreeStringList function releases memory allocated by
XmbTextPropertyToTextList, Xutf8TextPropertyToTextList and



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XTextPropertyToStringList and the missing charset list allo-
cated by XCreateFontSet.

14.1.3.  Setting and Reading Text Properties

Xlib provides two functions that you can use to set and read
the text properties for a given window.  You can use these
functions to set and read those properties of type TEXT
(WM_NAME, WM_ICON_NAME, WM_COMMAND, and WM_CLIENT_MACHINE).
In addition, Xlib provides separate convenience functions
that you can use to set each of these properties.  For fur-
ther information about these convenience functions, see sec-
tions 14.1.4, 14.1.5, 14.2.1, and 14.2.2, respectively.


To set one of a window's text properties, use XSetTextProp-
erty.
__
|
void XSetTextProperty(display, w, text_prop, property)
      Display *display;
      Window w;
      XTextProperty *text_prop;
      Atom property;


display   Specifies the connection to the X server.

w	  Specifies the window.

text_prop Specifies the XTextProperty structure to be used.

property  Specifies the property name.
|__

The XSetTextProperty function replaces the existing speci-
fied property for the named window with the data, type, for-
mat, and number of items determined by the value field, the
encoding field, the format field, and the nitems field,
respectively, of the specified XTextProperty structure.  If
the property does not already exist, XSetTextProperty sets
it for the specified window.

XSetTextProperty can generate BadAlloc, BadAtom, BadValue,
and BadWindow errors.


To read one of a window's text properties, use XGetTextProp-
erty.








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__
|
Status XGetTextProperty(display, w, text_prop_return, property)
       Display *display;
       Window w;
       XTextProperty *text_prop_return;
       Atom property;


display   Specifies the connection to the X server.

w	  Specifies the window.

text_prop_return
	  Returns the XTextProperty structure.

property  Specifies the property name.
|__

The XGetTextProperty function reads the specified property
from the window and stores the data in the returned
XTextProperty structure.  It stores the data in the value
field, the type of the data in the encoding field, the for-
mat of the data in the format field, and the number of items
of data in the nitems field.  An extra byte containing null
(which is not included in the nitems member) is stored at
the end of the value field of text_prop_return.  The partic-
ular interpretation of the property's encoding and data as
text is left to the calling application.  If the specified
property does not exist on the window, XGetTextProperty sets
the value field to NULL, the encoding field to None, the
format field to zero, and the nitems field to zero.

If it was able to read and store the data in the XTextProp-
erty structure, XGetTextProperty returns a nonzero status;
otherwise, it returns a zero status.

XGetTextProperty can generate BadAtom and BadWindow errors.

14.1.4.  Setting and Reading the WM_NAME Property

Xlib provides convenience functions that you can use to set
and read the WM_NAME property for a given window.


To set a window's WM_NAME property with the supplied conve-
nience function, use XSetWMName.











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__
|
void XSetWMName(display, w, text_prop)
      Display *display;
      Window w;
      XTextProperty *text_prop;


display   Specifies the connection to the X server.

w	  Specifies the window.

text_prop Specifies the XTextProperty structure to be used.
|__

The XSetWMName convenience function calls XSetTextProperty
to set the WM_NAME property.


To read a window's WM_NAME property with the supplied conve-
nience function, use XGetWMName.
__
|
Status XGetWMName(display, w, text_prop_return)
      Display *display;
      Window w;
      XTextProperty *text_prop_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

text_prop_return
	  Returns the XTextProperty structure.
|__

The XGetWMName convenience function calls XGetTextProperty
to obtain the WM_NAME property.  It returns a nonzero status
on success; otherwise, it returns a zero status.

The following two functions have been superseded by XSetWM-
Name and XGetWMName, respectively.  You can use these addi-
tional convenience functions for window names that are
encoded as STRING properties.


To assign a name to a window, use XStoreName.










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__
|
XStoreName(display, w, window_name)
      Display *display;
      Window w;
      char *window_name;


display   Specifies the connection to the X server.

w	  Specifies the window.

window_name
	  Specifies the window name, which should be a null-
	  terminated string.
|__

The XStoreName function assigns the name passed to win-
dow_name to the specified window.  A window manager can dis-
play the window name in some prominent place, such as the
title bar, to allow users to identify windows easily.  Some
window managers may display a window's name in the window's
icon, although they are encouraged to use the window's icon
name if one is provided by the application.  If the string
is not in the Host Portable Character Encoding, the result
is implementation-dependent.

XStoreName can generate BadAlloc and BadWindow errors.


To get the name of a window, use XFetchName.
__
|
Status XFetchName(display, w, window_name_return)
      Display *display;
      Window w;
      char **window_name_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

window_name_return
	  Returns the window name, which is a null-termi-
	  nated string.
|__

The XFetchName function returns the name of the specified
window.  If it succeeds, it returns a nonzero status; other-
wise, no name has been set for the window, and it returns
zero.  If the WM_NAME property has not been set for this
window, XFetchName sets window_name_return to NULL.  If the
data returned by the server is in the Latin Portable Charac-
ter Encoding, then the returned string is in the Host



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Portable Character Encoding.  Otherwise, the result is
implementation-dependent.  When finished with it, a client
must free the window name string using XFree.

XFetchName can generate a BadWindow error.

14.1.5.  Setting and Reading the WM_ICON_NAME Property

Xlib provides convenience functions that you can use to set
and read the WM_ICON_NAME property for a given window.


To set a window's WM_ICON_NAME property, use XSetWMIconName.
__
|
void XSetWMIconName(display, w, text_prop)
      Display *display;
      Window w;
      XTextProperty *text_prop;


display   Specifies the connection to the X server.

w	  Specifies the window.

text_prop Specifies the XTextProperty structure to be used.
|__

The XSetWMIconName convenience function calls XSetTextProp-
erty to set the WM_ICON_NAME property.


To read a window's WM_ICON_NAME property, use XGetWMIcon-
Name.
__
|
Status XGetWMIconName(display, w, text_prop_return)
      Display *display;
      Window w;
      XTextProperty *text_prop_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

text_prop_return
	  Returns the XTextProperty structure.
|__

The XGetWMIconName convenience function calls XGetTextProp-
erty to obtain the WM_ICON_NAME property.  It returns a
nonzero status on success; otherwise, it returns a zero sta-
tus.



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The next two functions have been superseded by XSetWMIcon-
Name and XGetWMIconName, respectively.	You can use these
additional convenience functions for window names that are
encoded as STRING properties.



To set the name to be displayed in a window's icon, use
XSetIconName.
__
|
XSetIconName(display, w, icon_name)
      Display *display;
      Window w;
      char *icon_name;


display   Specifies the connection to the X server.

w	  Specifies the window.

icon_name Specifies the icon name, which should be a null-
	  terminated string.
|__

If the string is not in the Host Portable Character Encod-
ing, the result is implementation-dependent.  XSetIconName
can generate BadAlloc and BadWindow errors.


To get the name a window wants displayed in its icon, use
XGetIconName.
__
|
Status XGetIconName(display, w, icon_name_return)
      Display *display;
      Window w;
      char **icon_name_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

icon_name_return
	  Returns the window's icon name, which is a null-
	  terminated string.
|__

The XGetIconName function returns the name to be displayed
in the specified window's icon.  If it succeeds, it returns
a nonzero status; otherwise, if no icon name has been set
for the window, it returns zero.  If you never assigned a
name to the window, XGetIconName sets icon_name_return to



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NULL.  If the data returned by the server is in the Latin
Portable Character Encoding, then the returned string is in
the Host Portable Character Encoding.  Otherwise, the result
is implementation-dependent.  When finished with it, a
client must free the icon name string using XFree.

XGetIconName can generate a BadWindow error.

14.1.6.  Setting and Reading the WM_HINTS Property

Xlib provides functions that you can use to set and read the
WM_HINTS property for a given window.  These functions use
the flags and the XWMHints structure, as defined in the
<X11/Xutil.h> header file.


To allocate an XWMHints structure, use XAllocWMHints.
__
|
XWMHints *XAllocWMHints()

|__

The XAllocWMHints function allocates and returns a pointer
to an XWMHints structure.  Note that all fields in the
XWMHints structure are initially set to zero.  If insuffi-
cient memory is available, XAllocWMHints returns NULL.	To
free the memory allocated to this structure, use XFree.

The XWMHints structure contains:



























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__
|    /* Window manager hints mask bits */

#define   InputHint		      (1L << 0)
#define   StateHint		      (1L << 1)
#define   IconPixmapHint	      (1L << 2)
#define   IconWindowHint	      (1L << 3)
#define   IconPositionHint	      (1L << 4)
#define   IconMaskHint		      (1L << 5)
#define   WindowGroupHint	      (1L << 6)
#define   UrgencyHint		      (1L << 8)
#define   AllHints		      (InputHint|State-
				      Hint|IconPixmapHint|
				      IconWindowHint|IconPosi-
				      tionHint|
				      IconMaskHint|Window-
				      GroupHint)


/* Values */

typedef struct {
     long flags;	 /* marks which fields in this structure are defined */
     Bool input;	 /* does this application rely on the window manager to
			 get keyboard input? */
     int initial_state;  /* see below */
     Pixmap icon_pixmap; /* pixmap to be used as icon */
     Window icon_window; /* window to be used as icon */
     int icon_x, icon_y; /* initial position of icon */
     Pixmap icon_mask;	 /* pixmap to be used as mask for icon_pixmap */
     XID window_group;	 /* id of related window group */
     /* this structure may be extended in the future */
} XWMHints;

|__

The input member is used to communicate to the window man-
ager the input focus model used by the application.  Appli-
cations that expect input but never explicitly set focus to
any of their subwindows (that is, use the push model of
focus management), such as X Version 10 style applications
that use real-estate driven focus, should set this member to
True.  Similarly, applications that set input focus to their
subwindows only when it is given to their top-level window
by a window manager should also set this member to True.
Applications that manage their own input focus by explicitly
setting focus to one of their subwindows whenever they want
keyboard input (that is, use the pull model of focus manage-
ment) should set this member to False.	Applications that
never expect any keyboard input also should set this member
to False.

Pull model window managers should make it possible for push
model applications to get input by setting input focus to
the top-level windows of applications whose input member is



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True.  Push model window managers should make sure that pull
model applications do not break them by resetting input
focus to PointerRoot when it is appropriate (for example,
whenever an application whose input member is False sets
input focus to one of its subwindows).

The definitions for the initial_state flag are:

#define   WithdrawnState	 0
#define   NormalState		 1    /* most applications start
				      this way */
#define   IconicState		 3    /* application wants to
				      start as an icon */

The icon_mask specifies which pixels of the icon_pixmap
should be used as the icon.  This allows for nonrectangular
icons.	Both icon_pixmap and icon_mask must be bitmaps.  The
icon_window lets an application provide a window for use as
an icon for window managers that support such use.  The win-
dow_group lets you specify that this window belongs to a
group of other windows.  For example, if a single applica-
tion manipulates multiple top-level windows, this allows you
to provide enough information that a window manager can
iconify all of the windows rather than just the one window.

The UrgencyHint flag, if set in the flags field, indicates
that the client deems the window contents to be urgent,
requiring the timely response of the user.  The window man-
ager will make some effort to draw the user's attention to
this window while this flag is set.  The client must provide
some means by which the user can cause the urgency flag to
be cleared (either mitigating the condition that made the
window urgent or merely shutting off the alarm) or the win-
dow to be withdrawn.


To set a window's WM_HINTS property, use XSetWMHints.
__
|
XSetWMHints(display, w, wmhints)
      Display *display;
      Window w;
      XWMHints *wmhints;



display   Specifies the connection to the X server.

w	  Specifies the window.

wmhints   Specifies the XWMHints structure to be used.
|__

The XSetWMHints function sets the window manager hints that



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include icon information and location, the initial state of
the window, and whether the application relies on the window
manager to get keyboard input.

XSetWMHints can generate BadAlloc and BadWindow errors.


To read a window's WM_HINTS property, use XGetWMHints.
__
|
XWMHints *XGetWMHints(display, w)
      Display *display;
      Window w;


display   Specifies the connection to the X server.

w	  Specifies the window.
|__

The XGetWMHints function reads the window manager hints and
returns NULL if no WM_HINTS property was set on the window
or returns a pointer to an XWMHints structure if it suc-
ceeds.	When finished with the data, free the space used for
it by calling XFree.

XGetWMHints can generate a BadWindow error.

14.1.7.  Setting and Reading the WM_NORMAL_HINTS Property

Xlib provides functions that you can use to set or read the
WM_NORMAL_HINTS property for a given window.  The functions
use the flags and the XSizeHints structure, as defined in
the <X11/Xutil.h> header file.

The size of the XSizeHints structure may grow in future
releases, as new components are added to support new ICCCM
features.  Passing statically allocated instances of this
structure into Xlib may result in memory corruption when
running against a future release of the library.  As such,
it is recommended that only dynamically allocated instances
of the structure be used.


To allocate an XSizeHints structure, use XAllocSizeHints.
__
|
XSizeHints *XAllocSizeHints()

|__

The XAllocSizeHints function allocates and returns a pointer
to an XSizeHints structure.  Note that all fields in the
XSizeHints structure are initially set to zero.  If



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insufficient memory is available, XAllocSizeHints returns
NULL.  To free the memory allocated to this structure, use
XFree.

The XSizeHints structure contains:

__
|    /* Size hints mask bits */

#define   USPosition	(1L << 0)	   /* user specified x, y */
#define   USSize	(1L << 1)	   /* user specified width, height
					   */
#define   PPosition	(1L << 2)	   /* program specified position
					   */
#define   PSize 	(1L << 3)	   /* program specified size */
#define   PMinSize	(1L << 4)	   /* program specified minimum
					   size */
#define   PMaxSize	(1L << 5)	   /* program specified maximum
					   size */
#define   PResizeInc	(1L << 6)	   /* program specified resize
					   increments */
#define   PAspect	(1L << 7)	   /* program specified min and
					   max aspect ratios */
#define   PBaseSize	(1L << 8)
#define   PWinGravity	(1L << 9)
#define   PAllHints	(PPosi-
			tion|PSize|
			PMinSize|PMax-
			Size|
			PRe-
			sizeInc|PAspect)


/* Values */

typedef struct {
     long flags;	 /* marks which fields in this structure are defined */
     int x, y;		 /* Obsolete */
     int width, height;  /* Obsolete */
     int min_width, min_height;
     int max_width, max_height;
     int width_inc, height_inc;
     struct {
	    int x;	 /* numerator */
	    int y;	 /* denominator */
     } min_aspect, max_aspect;
     int base_width, base_height;
     int win_gravity;
     /* this structure may be extended in the future */
} XSizeHints;

|__

The x, y, width, and height members are now obsolete and are



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left solely for compatibility reasons.	The min_width and
min_height members specify the minimum window size that
still allows the application to be useful.  The max_width
and max_height members specify the maximum window size.  The
width_inc and height_inc members define an arithmetic pro-
gression of sizes (minimum to maximum) into which the window
prefers to be resized.	The min_aspect and max_aspect mem-
bers are expressed as ratios of x and y, and they allow an
application to specify the range of aspect ratios it
prefers.  The base_width and base_height members define the
desired size of the window.  The window manager will inter-
pret the position of the window and its border width to
position the point of the outer rectangle of the overall
window specified by the win_gravity member.  The outer rect-
angle of the window includes any borders or decorations sup-
plied by the window manager.  In other words, if the window
manager decides to place the window where the client asked,
the position on the parent window's border named by the
win_gravity will be placed where the client window would
have been placed in the absence of a window manager.

Note that use of the PAllHints macro is highly discouraged.


To set a window's WM_NORMAL_HINTS property, use XSetWMNor-
malHints.
__
|
void XSetWMNormalHints(display, w, hints)
      Display *display;
      Window w;
      XSizeHints *hints;


display   Specifies the connection to the X server.

w	  Specifies the window.

hints	  Specifies the size hints for the window in its
	  normal state.
|__

The XSetWMNormalHints function replaces the size hints for
the WM_NORMAL_HINTS property on the specified window.  If
the property does not already exist, XSetWMNormalHints sets
the size hints for the WM_NORMAL_HINTS property on the spec-
ified window.  The property is stored with a type of
WM_SIZE_HINTS and a format of 32.

XSetWMNormalHints can generate BadAlloc and BadWindow
errors.






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To read a window's WM_NORMAL_HINTS property, use XGetWMNor-
malHints.
__
|
Status XGetWMNormalHints(display, w, hints_return, supplied_return)
      Display *display;
      Window w;
      XSizeHints *hints_return;
      long *supplied_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

hints_return
	  Returns the size hints for the window in its
	  normal state.

supplied_return
	  Returns the hints that were supplied by the user.
|__

The XGetWMNormalHints function returns the size hints stored
in the WM_NORMAL_HINTS property on the specified window.  If
the property is of type WM_SIZE_HINTS, is of format 32, and
is long enough to contain either an old (pre-ICCCM) or new
size hints structure, XGetWMNormalHints sets the various
fields of the XSizeHints structure, sets the supplied_return
argument to the list of fields that were supplied by the
user (whether or not they contained defined values), and
returns a nonzero status.  Otherwise, it returns a zero sta-
tus.

If XGetWMNormalHints returns successfully and a pre-ICCCM
size hints property is read, the supplied_return argument
will contain the following bits:


     (USPosition|USSize|PPosition|PSize|PMinSize|
      PMaxSize|PResizeInc|PAspect)


If the property is large enough to contain the base size and
window gravity fields as well, the supplied_return argument
will also contain the following bits:


     PBaseSize|PWinGravity


XGetWMNormalHints can generate a BadWindow error.





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To set a window's WM_SIZE_HINTS property, use XSetWMSize-
Hints.
__
|
void XSetWMSizeHints(display, w, hints, property)
      Display *display;
      Window w;
      XSizeHints *hints;
      Atom property;


display   Specifies the connection to the X server.

w	  Specifies the window.

hints	  Specifies the XSizeHints structure to be used.

property  Specifies the property name.
|__

The XSetWMSizeHints function replaces the size hints for the
specified property on the named window.  If the specified
property does not already exist, XSetWMSizeHints sets the
size hints for the specified property on the named window.
The property is stored with a type of WM_SIZE_HINTS and a
format of 32.  To set a window's normal size hints, you can
use the XSetWMNormalHints function.

XSetWMSizeHints can generate BadAlloc, BadAtom, and BadWin-
dow errors.


To read a window's WM_SIZE_HINTS property, use XGetWMSize-
Hints.























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__
|
Status XGetWMSizeHints(display, w, hints_return, supplied_return, property)
      Display *display;
      Window w;
      XSizeHints *hints_return;
      long *supplied_return;
      Atom property;


display   Specifies the connection to the X server.

w	  Specifies the window.

hints_return
	  Returns the XSizeHints structure.

supplied_return
	  Returns the hints that were supplied by the user.

property  Specifies the property name.
|__

The XGetWMSizeHints function returns the size hints stored
in the specified property on the named window.	If the prop-
erty is of type WM_SIZE_HINTS, is of format 32, and is long
enough to contain either an old (pre-ICCCM) or new size
hints structure, XGetWMSizeHints sets the various fields of
the XSizeHints structure, sets the supplied_return argument
to the list of fields that were supplied by the user
(whether or not they contained defined values), and returns
a nonzero status.  Otherwise, it returns a zero status.  To
get a window's normal size hints, you can use the XGetWMNor-
malHints function.

If XGetWMSizeHints returns successfully and a pre-ICCCM size
hints property is read, the supplied_return argument will
contain the following bits:


     (USPosition|USSize|PPosition|PSize|PMinSize|
      PMaxSize|PResizeInc|PAspect)


If the property is large enough to contain the base size and
window gravity fields as well, the supplied_return argument
will also contain the following bits:


     PBaseSize|PWinGravity


XGetWMSizeHints can generate BadAtom and BadWindow errors.





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14.1.8.  Setting and Reading the WM_CLASS Property

Xlib provides functions that you can use to set and get the
WM_CLASS property for a given window.  These functions use
the XClassHint structure, which is defined in the
<X11/Xutil.h> header file.


To allocate an XClassHint structure, use XAllocClassHint.
__
|
XClassHint *XAllocClassHint()

|__

The XAllocClassHint function allocates and returns a pointer
to an XClassHint structure.  Note that the pointer fields in
the XClassHint structure are initially set to NULL.  If
insufficient memory is available, XAllocClassHint returns
NULL.  To free the memory allocated to this structure, use
XFree.

The XClassHint contains:

__
|
typedef struct {
     char *res_name;
     char *res_class;
} XClassHint;

|__

The res_name member contains the application name, and the
res_class member contains the application class.  Note that
the name set in this property may differ from the name set
as WM_NAME.  That is, WM_NAME specifies what should be dis-
played in the title bar and, therefore, can contain temporal
information (for example, the name of a file currently in an
editor's buffer).  On the other hand, the name specified as
part of WM_CLASS is the formal name of the application that
should be used when retrieving the application's resources
from the resource database.


To set a window's WM_CLASS property, use XSetClassHint.











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__
|
XSetClassHint(display, w, class_hints)
      Display *display;
      Window w;
      XClassHint *class_hints;


display   Specifies the connection to the X server.

w	  Specifies the window.

class_hints
	  Specifies the XClassHint structure that is to be
	  used.
|__

The XSetClassHint function sets the class hint for the spec-
ified window.  If the strings are not in the Host Portable
Character Encoding, the result is implementation-dependent.

XSetClassHint can generate BadAlloc and BadWindow errors.


To read a window's WM_CLASS property, use XGetClassHint.
__
|
Status XGetClassHint(display, w, class_hints_return)
      Display *display;
      Window w;
      XClassHint *class_hints_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

class_hints_return
	  Returns the XClassHint structure.
|__

The XGetClassHint function returns the class hint of the
specified window to the members of the supplied structure.
If the data returned by the server is in the Latin Portable
Character Encoding, then the returned strings are in the
Host Portable Character Encoding.  Otherwise, the result is
implementation-dependent.  It returns a nonzero status on
success; otherwise, it returns a zero status.  To free
res_name and res_class when finished with the strings, use
XFree on each individually.

XGetClassHint can generate a BadWindow error.






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14.1.9.  Setting and Reading the WM_TRANSIENT_FOR Property

Xlib provides functions that you can use to set and read the
WM_TRANSIENT_FOR property for a given window.


To set a window's WM_TRANSIENT_FOR property, use XSetTran-
sientForHint.
__
|
XSetTransientForHint(display, w, prop_window)
      Display *display;
      Window w;
      Window prop_window;


display   Specifies the connection to the X server.

w	  Specifies the window.

prop_window
	  Specifies the window that the WM_TRANSIENT_FOR
	  property is to be set to.
|__

The XSetTransientForHint function sets the WM_TRANSIENT_FOR
property of the specified window to the specified prop_win-
dow.

XSetTransientForHint can generate BadAlloc and BadWindow
errors.


To read a window's WM_TRANSIENT_FOR property, use XGetTran-
sientForHint.
__
|
Status XGetTransientForHint(display, w, prop_window_return)
      Display *display;
      Window w;
      Window *prop_window_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

prop_window_return
	  Returns the WM_TRANSIENT_FOR property of the spec-
	  ified window.
|__

The XGetTransientForHint function returns the WM_TRAN-
SIENT_FOR property for the specified window.  It returns a



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nonzero status on success; otherwise, it returns a zero sta-
tus.

XGetTransientForHint can generate a BadWindow error.

14.1.10.  Setting and Reading the WM_PROTOCOLS Property

Xlib provides functions that you can use to set and read the
WM_PROTOCOLS property for a given window.


To set a window's WM_PROTOCOLS property, use XSetWMProto-
cols.
__
|
Status XSetWMProtocols(display, w, protocols, count)
      Display *display;
      Window w;
      Atom *protocols;
      int count;


display   Specifies the connection to the X server.

w	  Specifies the window.

protocols Specifies the list of protocols.

count	  Specifies the number of protocols in the list.
|__

The XSetWMProtocols function replaces the WM_PROTOCOLS prop-
erty on the specified window with the list of atoms speci-
fied by the protocols argument.  If the property does not
already exist, XSetWMProtocols sets the WM_PROTOCOLS prop-
erty on the specified window to the list of atoms specified
by the protocols argument.  The property is stored with a
type of ATOM and a format of 32.  If it cannot intern the
WM_PROTOCOLS atom, XSetWMProtocols returns a zero status.
Otherwise, it returns a nonzero status.

XSetWMProtocols can generate BadAlloc and BadWindow errors.


To read a window's WM_PROTOCOLS property, use XGetWMProto-
cols.











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__
|
Status XGetWMProtocols(display, w, protocols_return, count_return)
      Display *display;
      Window w;
      Atom **protocols_return;
      int *count_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

protocols_return
	  Returns the list of protocols.

count_return
	  Returns the number of protocols in the list.
|__

The XGetWMProtocols function returns the list of atoms
stored in the WM_PROTOCOLS property on the specified window.
These atoms describe window manager protocols in which the
owner of this window is willing to participate.  If the
property exists, is of type ATOM, is of format 32, and the
atom WM_PROTOCOLS can be interned, XGetWMProtocols sets the
protocols_return argument to a list of atoms, sets the
count_return argument to the number of elements in the list,
and returns a nonzero status.  Otherwise, it sets neither of
the return arguments and returns a zero status.  To release
the list of atoms, use XFree.

XGetWMProtocols can generate a BadWindow error.

14.1.11.  Setting and Reading the WM_COLORMAP_WINDOWS Prop-
erty

Xlib provides functions that you can use to set and read the
WM_COLORMAP_WINDOWS property for a given window.


To set a window's WM_COLORMAP_WINDOWS property, use XSetWM-
ColormapWindows.















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__
|
Status XSetWMColormapWindows(display, w, colormap_windows, count)
      Display *display;
      Window w;
      Window *colormap_windows;
      int count;


display   Specifies the connection to the X server.

w	  Specifies the window.

colormap_windows
	  Specifies the list of windows.

count	  Specifies the number of windows in the list.
|__

The XSetWMColormapWindows function replaces the WM_COL-
ORMAP_WINDOWS property on the specified window with the list
of windows specified by the colormap_windows argument.	If
the property does not already exist, XSetWMColormapWindows
sets the WM_COLORMAP_WINDOWS property on the specified win-
dow to the list of windows specified by the colormap_windows
argument.  The property is stored with a type of WINDOW and
a format of 32.  If it cannot intern the WM_COLORMAP_WINDOWS
atom, XSetWMColormapWindows returns a zero status.  Other-
wise, it returns a nonzero status.

XSetWMColormapWindows can generate BadAlloc and BadWindow
errors.


To read a window's WM_COLORMAP_WINDOWS property, use XGetWM-
ColormapWindows.






















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__
|
Status XGetWMColormapWindows(display, w, colormap_windows_return, count_return)
      Display *display;
      Window w;
      Window **colormap_windows_return;
      int *count_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

colormap_windows_return
	  Returns the list of windows.

count_return
	  Returns the number of windows in the list.
|__

The XGetWMColormapWindows function returns the list of win-
dow identifiers stored in the WM_COLORMAP_WINDOWS property
on the specified window.  These identifiers indicate the
colormaps that the window manager may need to install for
this window.  If the property exists, is of type WINDOW, is
of format 32, and the atom WM_COLORMAP_WINDOWS can be
interned, XGetWMColormapWindows sets the windows_return
argument to a list of window identifiers, sets the
count_return argument to the number of elements in the list,
and returns a nonzero status.  Otherwise, it sets neither of
the return arguments and returns a zero status.  To release
the list of window identifiers, use XFree.

XGetWMColormapWindows can generate a BadWindow error.

14.1.12.  Setting and Reading the WM_ICON_SIZE Property

Xlib provides functions that you can use to set and read the
WM_ICON_SIZE property for a given window.  These functions
use the XIconSize structure, which is defined in the
<X11/Xutil.h> header file.


To allocate an XIconSize structure, use XAllocIconSize.
__
|
XIconSize *XAllocIconSize()

|__

The XAllocIconSize function allocates and returns a pointer
to an XIconSize structure.  Note that all fields in the
XIconSize structure are initially set to zero.	If insuffi-
cient memory is available, XAllocIconSize returns NULL.  To
free the memory allocated to this structure, use XFree.



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The XIconSize structure contains:

__
|
typedef struct {
     int min_width, min_height;
     int max_width, max_height;
     int width_inc, height_inc;
} XIconSize;

|__

The width_inc and height_inc members define an arithmetic
progression of sizes (minimum to maximum) that represent the
supported icon sizes.


To set a window's WM_ICON_SIZE property, use XSetIconSizes.
__
|
XSetIconSizes(display, w, size_list, count)
      Display *display;
      Window w;
      XIconSize *size_list;
      int count;


display   Specifies the connection to the X server.

w	  Specifies the window.

size_list Specifies the size list.

count	  Specifies the number of items in the size list.
|__

The XSetIconSizes function is used only by window managers
to set the supported icon sizes.

XSetIconSizes can generate BadAlloc and BadWindow errors.


To read a window's WM_ICON_SIZE property, use XGetIconSizes.














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__
|
Status XGetIconSizes(display, w, size_list_return, count_return)
      Display *display;
      Window w;
      XIconSize **size_list_return;
      int *count_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

size_list_return
	  Returns the size list.

count_return
	  Returns the number of items in the size list.
|__

The XGetIconSizes function returns zero if a window manager
has not set icon sizes; otherwise, it returns nonzero.
XGetIconSizes should be called by an application that wants
to find out what icon sizes would be most appreciated by the
window manager under which the application is running.	The
application should then use XSetWMHints to supply the window
manager with an icon pixmap or window in one of the sup-
ported sizes.  To free the data allocated in
size_list_return, use XFree.

XGetIconSizes can generate a BadWindow error.

14.1.13.  Using Window Manager Convenience Functions

The XmbSetWMProperties and Xutf8SetWMProperties functions
store the standard set of window manager properties, with
text properties in standard encodings for internationalized
text communication.  The standard window manager properties
for a given window are WM_NAME, WM_ICON_NAME, WM_HINTS,
WM_NORMAL_HINTS, WM_CLASS, WM_COMMAND, WM_CLIENT_MACHINE,
and WM_LOCALE_NAME.

















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__
|
void XmbSetWMProperties(display, w, window_name, icon_name, argv, argc,
		      normal_hints, wm_hints, class_hints)
      Display *display;
      Window w;
      char *window_name;
      char *icon_name;
      char *argv[];
      int argc;
      XSizeHints *normal_hints;
      XWMHints *wm_hints;
      XClassHint *class_hints;


void Xutf8SetWMProperties(display, w, window_name, icon_name, argv, argc,
		      normal_hints, wm_hints, class_hints)
      Display *display;
      Window w;
      char *window_name;
      char *icon_name;
      char *argv[];
      int argc;
      XSizeHints *normal_hints;
      XWMHints *wm_hints;
      XClassHint *class_hints;


display   Specifies the connection to the X server.

w	  Specifies the window.

window_name
	  Specifies the window name, which should be a null-
	  terminated string.

icon_name Specifies the icon name, which should be a null-
	  terminated string.

argv	  Specifies the application's argument list.

argc	  Specifies the number of arguments.

hints	  Specifies the size hints for the window in its
	  normal state.

wm_hints  Specifies the XWMHints structure to be used.

class_hints
	  Specifies the XClassHint structure to be used.
|__

The XmbSetWMProperties and Xutf8SetWMProperties convenience
functions provide a simple programming interface for setting
those essential window properties that are used for



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communicating with other clients (particularly window and
session managers).

If the window_name argument is non-NULL, they set the
WM_NAME property.  If the icon_name argument is non-NULL,
they set the WM_ICON_NAME property.  The window_name and
icon_name arguments are null-terminated strings, for Xmb-
SetWMProperties in the encoding of the current locale, for
Xutf8SetWMProperties in UTF-8 encoding.  If the arguments
can be fully converted to the STRING encoding, the proper-
ties are created with type ``STRING''; otherwise, the argu-
ments are converted to Compound Text, and the properties are
created with type ``COMPOUND_TEXT''.

If the normal_hints argument is non-NULL, XmbSetWMProperties
and Xutf8SetWMProperties call XSetWMNormalHints, which sets
the WM_NORMAL_HINTS property (see section 14.1.7).  If the
wm_hints argument is non-NULL, XmbSetWMProperties and
Xutf8SetWMProperties call XSetWMHints, which sets the
WM_HINTS property (see section 14.1.6).

If the argv argument is non-NULL, XmbSetWMProperties and
Xutf8SetWMProperties set the WM_COMMAND property from argv
and argc.  An argc of zero indicates a zero-length command.

The hostname of the machine is stored using XSetWMClientMa-
chine (see section 14.2.2).

If the class_hints argument is non-NULL, XmbSetWMProperties
and Xutf8SetWMProperties set the WM_CLASS property.  If the
res_name member in the XClassHint structure is set to the
NULL pointer and the RESOURCE_NAME environment variable is
set, the value of the environment variable is substituted
for res_name.  If the res_name member is NULL, the environ-
ment variable is not set, and argv and argv[0] are set, then
the value of argv[0], stripped of any directory prefixes, is
substituted for res_name.

It is assumed that the supplied class_hints.res_name and
argv, the RESOURCE_NAME environment variable, and the host-
name of the machine are in the encoding of the current
locale.  The corresponding WM_CLASS, WM_COMMAND, and
WM_CLIENT_MACHINE properties are typed according to the
local host locale announcer.  No encoding conversion is per-
formed for these strings prior to storage in the properties.

For clients that need to process the property text in a
locale, XmbSetWMProperties and Xutf8SetWMProperties set the
WM_LOCALE_NAME property to be the name of the current
locale.  The name is assumed to be in the Host Portable
Character Encoding and is converted to STRING for storage in
the property.





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XmbSetWMProperties and Xutf8SetWMProperties can generate
BadAlloc and BadWindow errors.

The function Xutf8SetWMProperties is an XFree86 extension
introduced in XFree86 4.0.2. Its presence is indicated by
the macro X_HAVE_UTF8_STRING.


To set a window's standard window manager properties with
strings in client-specified encodings, use XSetWMProperties.
The standard window manager properties for a given window
are WM_NAME, WM_ICON_NAME, WM_HINTS, WM_NORMAL_HINTS,
WM_CLASS, WM_COMMAND, and WM_CLIENT_MACHINE.
__
|
void XSetWMProperties(display, w, window_name, icon_name, argv, argc, normal_hints, wm_hints, class_hints)
      Display *display;
      Window w;
      XTextProperty *window_name;
      XTextProperty *icon_name;
      char **argv;
      int argc;
      XSizeHints *normal_hints;
      XWMHints *wm_hints;
      XClassHint *class_hints;


display   Specifies the connection to the X server.

w	  Specifies the window.

window_name
	  Specifies the window name, which should be a null-
	  terminated string.

icon_name Specifies the icon name, which should be a null-
	  terminated string.

argv	  Specifies the application's argument list.

argc	  Specifies the number of arguments.

normal_hints
	  Specifies the size hints for the window in its
	  normal state.

wm_hints  Specifies the XWMHints structure to be used.

class_hints
	  Specifies the XClassHint structure to be used.
|__

The XSetWMProperties convenience function provides a single
programming interface for setting those essential window



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properties that are used for communicating with other
clients (particularly window and session managers).

If the window_name argument is non-NULL, XSetWMProperties
calls XSetWMName, which, in turn, sets the WM_NAME property
(see section 14.1.4).  If the icon_name argument is non-
NULL, XSetWMProperties calls XSetWMIconName, which sets the
WM_ICON_NAME property (see section 14.1.5).  If the argv
argument is non-NULL, XSetWMProperties calls XSetCommand,
which sets the WM_COMMAND property (see section 14.2.1).
Note that an argc of zero is allowed to indicate a zero-
length command.  Note also that the hostname of this machine
is stored using XSetWMClientMachine (see section 14.2.2).

If the normal_hints argument is non-NULL, XSetWMProperties
calls XSetWMNormalHints, which sets the WM_NORMAL_HINTS
property (see section 14.1.7).	If the wm_hints argument is
non-NULL, XSetWMProperties calls XSetWMHints, which sets the
WM_HINTS property (see section 14.1.6).

If the class_hints argument is non-NULL, XSetWMProperties
calls XSetClassHint, which sets the WM_CLASS property (see
section 14.1.8).  If the res_name member in the XClassHint
structure is set to the NULL pointer and the RESOURCE_NAME
environment variable is set, then the value of the environ-
ment variable is substituted for res_name.  If the res_name
member is NULL, the environment variable is not set, and
argv and argv[0] are set, then the value of argv[0],
stripped of any directory prefixes, is substituted for
res_name.

XSetWMProperties can generate BadAlloc and BadWindow errors.

14.2.  Client to Session Manager Communication

This section discusses how to:

o    Set and read the WM_COMMAND property

o    Set and read the WM_CLIENT_MACHINE property

14.2.1.  Setting and Reading the WM_COMMAND Property

Xlib provides functions that you can use to set and read the
WM_COMMAND property for a given window.


To set a window's WM_COMMAND property, use XSetCommand.









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__
|
XSetCommand(display, w, argv, argc)
      Display *display;
      Window w;
      char **argv;
      int argc;


display   Specifies the connection to the X server.

w	  Specifies the window.

argv	  Specifies the application's argument list.

argc	  Specifies the number of arguments.
|__

The XSetCommand function sets the command and arguments used
to invoke the application.  (Typically, argv is the argv
array of your main program.)  If the strings are not in the
Host Portable Character Encoding, the result is implementa-
tion-dependent.

XSetCommand can generate BadAlloc and BadWindow errors.


To read a window's WM_COMMAND property, use XGetCommand.
__
|
Status XGetCommand(display, w, argv_return, argc_return)
      Display *display;
      Window w;
      char ***argv_return;
      int *argc_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

argv_return
	  Returns the application's argument list.

argc_return
	  Returns the number of arguments returned.
|__

The XGetCommand function reads the WM_COMMAND property from
the specified window and returns a string list.  If the
WM_COMMAND property exists, it is of type STRING and format
8.  If sufficient memory can be allocated to contain the
string list, XGetCommand fills in the argv_return and
argc_return arguments and returns a nonzero status.  Other-
wise, it returns a zero status.  If the data returned by the



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server is in the Latin Portable Character Encoding, then the
returned strings are in the Host Portable Character Encod-
ing.  Otherwise, the result is implementation-dependent.  To
free the memory allocated to the string list, use
XFreeStringList.

14.2.2.  Setting and Reading the WM_CLIENT_MACHINE Property

Xlib provides functions that you can use to set and read the
WM_CLIENT_MACHINE property for a given window.


To set a window's WM_CLIENT_MACHINE property, use XSetWM-
ClientMachine.
__
|
void XSetWMClientMachine(display, w, text_prop)
      Display *display;
      Window w;
      XTextProperty *text_prop;


display   Specifies the connection to the X server.

w	  Specifies the window.

text_prop Specifies the XTextProperty structure to be used.
|__

The XSetWMClientMachine convenience function calls XSet-
TextProperty to set the WM_CLIENT_MACHINE property.


To read a window's WM_CLIENT_MACHINE property, use XGetWM-
ClientMachine.
__
|
Status XGetWMClientMachine(display, w, text_prop_return)
      Display *display;
      Window w;
      XTextProperty *text_prop_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

text_prop_return
	  Returns the XTextProperty structure.
|__

The XGetWMClientMachine convenience function performs an
XGetTextProperty on the WM_CLIENT_MACHINE property.  It
returns a nonzero status on success; otherwise, it returns a



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zero status.

14.3.  Standard Colormaps

Applications with color palettes, smooth-shaded drawings, or
digitized images demand large numbers of colors.  In addi-
tion, these applications often require an efficient mapping
from color triples to pixel values that display the appro-
priate colors.

As an example, consider a three-dimensional display program
that wants to draw a smoothly shaded sphere.  At each pixel
in the image of the sphere, the program computes the inten-
sity and color of light reflected back to the viewer.  The
result of each computation is a triple of red, green, and
blue (RGB) coefficients in the range 0.0 to 1.0.  To draw
the sphere, the program needs a colormap that provides a
large range of uniformly distributed colors.  The colormap
should be arranged so that the program can convert its RGB
triples into pixel values very quickly, because drawing the
entire sphere requires many such conversions.

On many current workstations, the display is limited to 256
or fewer colors.  Applications must allocate colors care-
fully, not only to make sure they cover the entire range
they need but also to make use of as many of the available
colors as possible.  On a typical X display, many applica-
tions are active at once.  Most workstations have only one
hardware look-up table for colors, so only one application
colormap can be installed at a given time.  The application
using the installed colormap is displayed correctly, and the
other applications go technicolor and are displayed with
false colors.

As another example, consider a user who is running an image
processing program to display earth-resources data.  The
image processing program needs a colormap set up with 8
reds, 8 greens, and 4 blues, for a total of 256 colors.
Because some colors are already in use in the default col-
ormap, the image processing program allocates and installs a
new colormap.

The user decides to alter some of the colors in the image by
invoking a color palette program to mix and choose colors.
The color palette program also needs a colormap with eight
reds, eight greens, and four blues, so just like the image
processing program, it must allocate and install a new col-
ormap.

Because only one colormap can be installed at a time, the
color palette may be displayed incorrectly whenever the
image processing program is active.  Conversely, whenever
the palette program is active, the image may be displayed
incorrectly.  The user can never match or compare colors in



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the palette and image.	Contention for colormap resources
can be reduced if applications with similar color needs
share colormaps.

The image processing program and the color palette program
could share the same colormap if there existed a convention
that described how the colormap was set up.  Whenever either
program was active, both would be displayed correctly.

The standard colormap properties define a set of commonly
used colormaps.  Applications that share these colormaps and
conventions display true colors more often and provide a
better interface to the user.

Standard colormaps allow applications to share commonly used
color resources.  This allows many applications to be dis-
played in true colors simultaneously, even when each appli-
cation needs an entirely filled colormap.

Several standard colormaps are described in this section.
Usually, a window manager creates these colormaps.  Applica-
tions should use the standard colormaps if they already
exist.


To allocate an XStandardColormap structure, use XAllocStan-
dardColormap.
__
|
XStandardColormap *XAllocStandardColormap()

|__

The XAllocStandardColormap function allocates and returns a
pointer to an XStandardColormap structure.  Note that all
fields in the XStandardColormap structure are initially set
to zero.  If insufficient memory is available, XAllocStan-
dardColormap returns NULL.  To free the memory allocated to
this structure, use XFree.

The XStandardColormap structure contains:
















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__
|    /* Hints */

#define   ReleaseByFreeingCol-	 ( (XID)
	  ormap 		 1L)

/* Values */

typedef struct {
     Colormap colormap;
     unsigned long red_max;
     unsigned long red_mult;
     unsigned long green_max;
     unsigned long green_mult;
     unsigned long blue_max;
     unsigned long blue_mult;
     unsigned long base_pixel;
     VisualID visualid;
     XID killid;
} XStandardColormap;

|__

The colormap member is the colormap created by the XCreate-
Colormap function.  The red_max, green_max, and blue_max
members give the maximum red, green, and blue values,
respectively.  Each color coefficient ranges from zero to
its max, inclusive.  For example, a common colormap alloca-
tion is 3/3/2 (3 planes for red, 3 planes for green, and 2
planes for blue).  This colormap would have red_max = 7,
green_max = 7, and blue_max = 3.  An alternate allocation
that uses only 216 colors is red_max = 5, green_max = 5, and
blue_max = 5.

The red_mult, green_mult, and blue_mult members give the
scale factors used to compose a full pixel value.  (See the
discussion of the base_pixel members for further informa-
tion.)	For a 3/3/2 allocation, red_mult might be 32,
green_mult might be 4, and blue_mult might be 1.  For a
6-colors-each allocation, red_mult might be 36, green_mult
might be 6, and blue_mult might be 1.

The base_pixel member gives the base pixel value used to
compose a full pixel value.  Usually, the base_pixel is
obtained from a call to the XAllocColorPlanes function.
Given integer red, green, and blue coefficients in their
appropriate ranges, one then can compute a corresponding
pixel value by using the following expression:


     (r * red_mult + g * green_mult + b * blue_mult + base_pixel) & 0xFFFFFFFF


For GrayScale colormaps, only the colormap, red_max,
red_mult, and base_pixel members are defined.  The other



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members are ignored.  To compute a GrayScale pixel value,
use the following expression:


     (gray * red_mult + base_pixel) & 0xFFFFFFFF


Negative multipliers can be represented by converting the
2's complement representation of the multiplier into an
unsigned long and storing the result in the appropriate
_mult field.  The step of masking by 0xFFFFFFFF effectively
converts the resulting positive multiplier into a negative
one.  The masking step will take place automatically on many
machine architectures, depending on the size of the integer
type used to do the computation.

The visualid member gives the ID number of the visual from
which the colormap was created.  The killid member gives a
resource ID that indicates whether the cells held by this
standard colormap are to be released by freeing the colormap
ID or by calling the XKillClient function on the indicated
resource.  (Note that this method is necessary for allocat-
ing out of an existing colormap.)

The properties containing the XStandardColormap information
have the type RGB_COLOR_MAP.

The remainder of this section discusses standard colormap
properties and atoms as well as how to manipulate standard
colormaps.

14.3.1.  Standard Colormap Properties and Atoms

Several standard colormaps are available.  Each standard
colormap is defined by a property, and each such property is
identified by an atom.	The following list names the atoms
and describes the colormap associated with each one.  The
<X11/Xatom.h> header file contains the definitions for each
of the following atoms, which are prefixed with XA_.

RGB_DEFAULT_MAP
     This atom names a property.  The value of the property
     is an array of XStandardColormap structures.  Each
     entry in the array describes an RGB subset of the
     default color map for the Visual specified by
     visual_id.

     Some applications only need a few RGB colors and may be
     able to allocate them from the system default colormap.
     This is the ideal situation because the fewer colormaps
     that are active in the system the more applications are
     displayed with correct colors at all times.





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     A typical allocation for the RGB_DEFAULT_MAP on 8-plane
     displays is 6 reds, 6 greens, and 6 blues.  This gives
     216 uniformly distributed colors (6 intensities of 36
     different hues) and still leaves 40 elements of a
     256-element colormap available for special-purpose col-
     ors for text, borders, and so on.

RGB_BEST_MAP
     This atom names a property.  The value of the property
     is an XStandardColormap.

     The property defines the best RGB colormap available on
     the screen.  (Of course, this is a subjective evalua-
     tion.)  Many image processing and three-dimensional
     applications need to use all available colormap cells
     and to distribute as many perceptually distinct colors
     as possible over those cells.  This implies that there
     may be more green values available than red, as well as
     more green or red than blue.

     For an 8-plane PseudoColor visual, RGB_BEST_MAP is
     likely to be a 3/3/2 allocation.  For a 24-plane
     DirectColor visual, RGB_BEST_MAP is normally an 8/8/8
     allocation.

RGB_RED_MAP
RGB_GREEN_MAP
RGB_BLUE_MAP
     These atoms name properties.  The value of each prop-
     erty is an XStandardColormap.

     The properties define all-red, all-green, and all-blue
     colormaps, respectively.  These maps are used by appli-
     cations that want to make color-separated images.	For
     example, a user might generate a full-color image on an
     8-plane display both by rendering an image three times
     (once with high color resolution in red, once with
     green, and once with blue) and by multiply exposing a
     single frame in a camera.

RGB_GRAY_MAP
     This atom names a property.  The value of the property
     is an XStandardColormap.

     The property describes the best GrayScale colormap
     available on the screen.  As previously mentioned, only
     the colormap, red_max, red_mult, and base_pixel members
     of the XStandardColormap structure are used for
     GrayScale colormaps.

14.3.2.  Setting and Obtaining Standard Colormaps

Xlib provides functions that you can use to set and obtain
an XStandardColormap structure.



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To set an XStandardColormap structure, use XSetRGBColormaps.
__
|
void XSetRGBColormaps(display, w, std_colormap, count, property)
      Display *display;
      Window w;
      XStandardColormap *std_colormap;
      int count;
      Atom property;


display   Specifies the connection to the X server.

w	  Specifies the window.

std_colormap
	  Specifies the XStandardColormap structure to be
	  used.

count	  Specifies the number of colormaps.

property  Specifies the property name.
|__

The XSetRGBColormaps function replaces the RGB colormap def-
inition in the specified property on the named window.	If
the property does not already exist, XSetRGBColormaps sets
the RGB colormap definition in the specified property on the
named window.  The property is stored with a type of
RGB_COLOR_MAP and a format of 32.  Note that it is the
caller's responsibility to honor the ICCCM restriction that
only RGB_DEFAULT_MAP contain more than one definition.

The XSetRGBColormaps function usually is only used by window
or session managers.  To create a standard colormap, follow
this procedure:

1.   Open a new connection to the same server.

2.   Grab the server.

3.   See if the property is on the property list of the root
     window for the screen.

4.   If the desired property is not present:

     o	  Create a colormap (unless you are using the
	  default colormap of the screen).

     o	  Determine the color characteristics of the visual.

     o	  Allocate cells in the colormap (or create it with
	  AllocAll).




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     o	  Call XStoreColors to store appropriate color val-
	  ues in the colormap.

     o	  Fill in the descriptive members in the XStandard-
	  Colormap structure.

     o	  Attach the property to the root window.

     o	  Use XSetCloseDownMode to make the resource perma-
	  nent.

5.   Ungrab the server.

XSetRGBColormaps can generate BadAlloc, BadAtom, and BadWin-
dow errors.


To obtain the XStandardColormap structure associated with
the specified property, use XGetRGBColormaps.
__
|
Status XGetRGBColormaps(display, w, std_colormap_return, count_return, property)
      Display *display;
      Window w;
      XStandardColormap **std_colormap_return;
      int *count_return;
      Atom property;


display   Specifies the connection to the X server.

w	  Specifies the window.

std_colormap_return
	  Returns the XStandardColormap structure.

count_return
	  Returns the number of colormaps.

property  Specifies the property name.
|__

The XGetRGBColormaps function returns the RGB colormap defi-
nitions stored in the specified property on the named win-
dow.  If the property exists, is of type RGB_COLOR_MAP, is
of format 32, and is long enough to contain a colormap defi-
nition, XGetRGBColormaps allocates and fills in space for
the returned colormaps and returns a nonzero status.  If the
visualid is not present, XGetRGBColormaps assumes the
default visual for the screen on which the window is
located; if the killid is not present, None is assumed,
which indicates that the resources cannot be released.	Oth-
erwise, none of the fields are set, and XGetRGBColormaps
returns a zero status.	Note that it is the caller's



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responsibility to honor the ICCCM restriction that only
RGB_DEFAULT_MAP contain more than one definition.

XGetRGBColormaps can generate BadAtom and BadWindow errors.





















































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			 Chapter 15

		 Resource Manager Functions



A program often needs a variety of options in the X environ-
ment (for example, fonts, colors, icons, and cursors).
Specifying all of these options on the command line is awk-
ward because users may want to customize many aspects of the
program and need a convenient way to establish these cus-
tomizations as the default settings.  The resource manager
is provided for this purpose.  Resource specifications are
usually stored in human-readable files and in server proper-
ties.

The resource manager is a database manager with a twist.  In
most database systems, you perform a query using an impre-
cise specification, and you get back a set of records.	The
resource manager, however, allows you to specify a large set
of values with an imprecise specification, to query the
database with a precise specification, and to get back only
a single value.  This should be used by applications that
need to know what the user prefers for colors, fonts, and
other resources.  It is this use as a database for dealing
with X resources that inspired the name ``Resource Man-
ager,'' although the resource manager can be and is used in
other ways.

For example, a user of your application may want to specify
that all windows should have a blue background but that all
mail-reading windows should have a red background.  With
well-engineered and coordinated applications, a user can
define this information using only two lines of specifica-
tions.

As an example of how the resource manager works, consider a
mail-reading application called xmh.  Assume that it is
designed so that it uses a complex window hierarchy all the
way down to individual command buttons, which may be actual
small subwindows in some toolkits.  These are often called
objects or widgets.  In such toolkit systems, each user
interface object can be composed of other objects and can be
assigned a name and a class.  Fully qualified names or
classes can have arbitrary numbers of component names, but a
fully qualified name always has the same number of component
names as a fully qualified class.  This generally reflects
the structure of the application as composed of these
objects, starting with the application itself.

For example, the xmh mail program has a name ``xmh'' and is
one of a class of ``Mail'' programs.  By convention, the



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first character of class components is capitalized, and the
first letter of name components is in lowercase.  Each name
and class finally has an attribute (for example, ``fore-
ground'' or ``font'').	If each window is properly assigned
a name and class, it is easy for the user to specify
attributes of any portion of the application.

At the top level, the application might consist of a paned
window (that is, a window divided into several sections)
named ``toc''.	One pane of the paned window is a button box
window named ``buttons'' and is filled with command buttons.
One of these command buttons is used to incorporate new mail
and has the name ``incorporate''.  This window has a fully
qualified name, ``xmh.toc.buttons.incorporate'', and a fully
qualified class, ``Xmh.Paned.Box.Command''.  Its fully qual-
ified name is the name of its parent, ``xmh.toc.buttons'',
followed by its name, ``incorporate''.	Its class is the
class of its parent, ``Xmh.Paned.Box'', followed by its par-
ticular class, ``Command''.  The fully qualified name of a
resource is the attribute's name appended to the object's
fully qualified name, and the fully qualified class is its
class appended to the object's class.

The incorporate button might need the following resources:
Title string, Font, Foreground color for its inactive state,
Background color for its inactive state, Foreground color
for its active state, and Background color for its active
state.	Each resource is considered to be an attribute of
the button and, as such, has a name and a class.  For exam-
ple, the foreground color for the button in its active state
might be named ``activeForeground'', and its class might be
``Foreground''.

When an application looks up a resource (for example, a
color), it passes the complete name and complete class of
the resource to a look-up routine.  The resource manager
compares this complete specification against the incomplete
specifications of entries in the resource database, finds
the best match, and returns the corresponding value for that
entry.

The definitions for the resource manager are contained in
<X11/Xresource.h>.

15.1.  Resource File Syntax

The syntax of a resource file is a sequence of resource
lines terminated by newline characters or the end of the
file.  The syntax of an individual resource line is:


ResourceLine   = Comment | IncludeFile | ResourceSpec | <empty line>
Comment        = "!" {<any character except null or newline>}
IncludeFile    = "#" WhiteSpace "include" WhiteSpace FileName WhiteSpace



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FileName       = <valid filename for operating system>
ResourceSpec   = WhiteSpace ResourceName WhiteSpace ":" WhiteSpace Value
ResourceName   = [Binding] {Component Binding} ComponentName
Binding        = "." | "*"
WhiteSpace     = {<space> | <horizontal tab>}
Component      = "?" | ComponentName
ComponentName  = NameChar {NameChar}
NameChar       = "a"-"z" | "A"-"Z" | "0"-"9" | "_" | "-"
Value	       = {<any character except null or unescaped newline>}


Elements separated by vertical bar (|) are alternatives.
Curly braces ({...}) indicate zero or more repetitions of
the enclosed elements.	Square brackets ([...]) indicate
that the enclosed element is optional.	Quotes ("...") are
used around literal characters.

IncludeFile lines are interpreted by replacing the line with
the contents of the specified file.  The word ``include''
must be in lowercase.  The file name is interpreted relative
to the directory of the file in which the line occurs (for
example, if the file name contains no directory or contains
a relative directory specification).

If a ResourceName contains a contiguous sequence of two or
more Binding characters, the sequence will be replaced with
a single ``.'' character if the sequence contains only ``.''
characters; otherwise, the sequence will be replaced with a
single ``*'' character.

A resource database never contains more than one entry for a
given ResourceName.  If a resource file contains multiple
lines with the same ResourceName, the last line in the file
is used.

Any white space characters before or after the name or colon
in a ResourceSpec are ignored.	To allow a Value to begin
with white space, the two-character sequence ``\space''
(backslash followed by space) is recognized and replaced by
a space character, and the two-character sequence ``\tab''
(backslash followed by horizontal tab) is recognized and
replaced by a horizontal tab character.  To allow a Value to
contain embedded newline characters, the two-character
sequence ``\n'' is recognized and replaced by a newline
character.  To allow a Value to be broken across multiple
lines in a text file, the two-character sequence ``\new-
line'' (backslash followed by newline) is recognized and
removed from the value.  To allow a Value to contain arbi-
trary character codes, the four-character sequence ``\nnn'',
where each n is a digit character in the range of
``0''-``7'', is recognized and replaced with a single byte
that contains the octal value specified by the sequence.
Finally, the two-character sequence ``\\'' is recognized and
replaced with a single backslash.



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As an example of these sequences, the following resource
line contains a value consisting of four characters: a back-
slash, a null, a ``z'', and a newline:

     magic.values: \\\000\
     z\n


15.2.  Resource Manager Matching Rules

The algorithm for determining which resource database entry
matches a given query is the heart of the resource manager.
All queries must fully specify the name and class of the
desired resource (use of the characters ``*'' and ``?'' is
not permitted).  The library supports up to 100 components
in a full name or class.  Resources are stored in the
database with only partially specified names and classes,
using pattern matching constructs.  An asterisk (*) is a
loose binding and is used to represent any number of inter-
vening components, including none.  A period (.) is a tight
binding and is used to separate immediately adjacent compo-
nents.	A question mark (?) is used to match any single com-
ponent name or class.  A database entry cannot end in a
loose binding; the final component (which cannot be the
character ``?'') must be specified.  The lookup algorithm
searches the database for the entry that most closely
matches (is most specific for) the full name and class being
queried.  When more than one database entry matches the full
name and class, precedence rules are used to select just
one.

The full name and class are scanned from left to right (from
highest level in the hierarchy to lowest), one component at
a time.  At each level, the corresponding component and/or
binding of each matching entry is determined, and these
matching components and bindings are compared according to
precedence rules.  Each of the rules is applied at each
level before moving to the next level, until a rule selects
a single entry over all others.  The rules, in order of
precedence, are:

1.   An entry that contains a matching component (whether
     name, class, or the character ``?'')  takes precedence
     over entries that elide the level (that is, entries
     that match the level in a loose binding).

2.   An entry with a matching name takes precedence over
     both entries with a matching class and entries that
     match using the character ``?''.  An entry with a
     matching class takes precedence over entries that match
     using the character ``?''.

3.   An entry preceded by a tight binding takes precedence
     over entries preceded by a loose binding.



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To illustrate these rules, consider the following resource
database entries:

     xmh*Paned*activeForeground:	red(entry A)
     *incorporate.Foreground: blue	(entry B)
     xmh.toc*Command*activeForeground:	green(entry C)
     xmh.toc*?.Foreground:    white	(entry D)
     xmh.toc*Command.activeForeground:	black(entry E)


Consider a query for the resource:


     xmh.toc.messagefunctions.incorporate.activeForeground(name)
     Xmh.Paned.Box.Command.Foreground	(class)


At the first level (xmh, Xmh), rule 1 eliminates entry B.
At the second level (toc, Paned), rule 2 eliminates entry A.
At the third level (messagefunctions, Box), no entries are
eliminated.  At the fourth level (incorporate, Command),
rule 2 eliminates entry D.  At the fifth level (activeFore-
ground, Foreground), rule 3 eliminates entry C.

15.3.  Quarks

Most uses of the resource manager involve defining names,
classes, and representation types as string constants.	How-
ever, always referring to strings in the resource manager
can be slow, because it is so heavily used in some toolkits.
To solve this problem, a shorthand for a string is used in
place of the string in many of the resource manager func-
tions.	Simple comparisons can be performed rather than
string comparisons.  The shorthand name for a string is
called a quark and is the type XrmQuark.  On some occasions,
you may want to allocate a quark that has no string equiva-
lent.

A quark is to a string what an atom is to a string in the
server, but its use is entirely local to your application.


To allocate a new quark, use XrmUniqueQuark.
__
|
XrmQuark XrmUniqueQuark()

|__

The XrmUniqueQuark function allocates a quark that is guar-
anteed not to represent any string that is known to the
resource manager.





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Each name, class, and representation type is typedef'd as an
XrmQuark.

__
|
typedef int XrmQuark, *XrmQuarkList;
typedef XrmQuark XrmName;
typedef XrmQuark XrmClass;
typedef XrmQuark XrmRepresentation;
#define NULLQUARK ((XrmQuark) 0)

|__

Lists are represented as null-terminated arrays of quarks.
The size of the array must be large enough for the number of
components used.

__
|
typedef XrmQuarkList XrmNameList;
typedef XrmQuarkList XrmClassList;

|__


To convert a string to a quark, use XrmStringToQuark or Xrm-
PermStringToQuark.
__
|
#define XrmStringToName(string) XrmStringToQuark(string)
#define XrmStringToClass(string) XrmStringToQuark(string)
#define XrmStringToRepresentation(string) XrmStringToQuark(string)

XrmQuark XrmStringToQuark(string)
     char *string;

XrmQuark XrmPermStringToQuark(string)
     char *string;


string	  Specifies the string for which a quark is to be
	  allocated.
|__

These functions can be used to convert from string to quark
representation.  If the string is not in the Host Portable
Character Encoding, the conversion is implementation-depen-
dent.  The string argument to XrmStringToQuark need not be
permanently allocated storage.	XrmPermStringToQuark is just
like XrmStringToQuark, except that Xlib is permitted to
assume the string argument is permanently allocated, and,
hence, that it can be used as the value to be returned by
XrmQuarkToString.




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For any given quark, if XrmStringToQuark returns a non-NULL
value, all future calls will return the same value (identi-
cal address).


To convert a quark to a string, use XrmQuarkToString.
__
|
#define XrmNameToString(name) XrmQuarkToString(name)
#define XrmClassToString(class) XrmQuarkToString(class)
#define XrmRepresentationToString(type) XrmQuarkToString(type)

char *XrmQuarkToString(quark)
     XrmQuark quark;


quark	  Specifies the quark for which the equivalent
	  string is desired.
|__

These functions can be used to convert from quark represen-
tation to string.  The string pointed to by the return value
must not be modified or freed.	The returned string is byte-
for-byte equal to the original string passed to one of the
string-to-quark routines.  If no string exists for that
quark, XrmQuarkToString returns NULL.  For any given quark,
if XrmQuarkToString returns a non-NULL value, all future
calls will return the same value (identical address).


To convert a string with one or more components to a quark
list, use XrmStringToQuarkList.
__
|
#define XrmStringToNameList(str, name)	XrmStringToQuarkList((str), (name))
#define XrmStringToClassList(str, class) XrmStringToQuarkList((str), (class))

void XrmStringToQuarkList(string, quarks_return)
     char *string;
     XrmQuarkList quarks_return;


string	  Specifies the string for which a quark list is to
	  be allocated.

quarks_return
	  Returns the list of quarks.  The caller must allo-
	  cate sufficient space for the quarks list before
	  calling XrmStringToQuarkList.
|__

The XrmStringToQuarkList function converts the null-termi-
nated string (generally a fully qualified name) to a list of
quarks.  Note that the string must be in the valid



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ResourceName format (see section 15.1).  If the string is
not in the Host Portable Character Encoding, the conversion
is implementation-dependent.

A binding list is a list of type XrmBindingList and indi-
cates if components of name or class lists are bound tightly
or loosely (that is, if wildcarding of intermediate compo-
nents is specified).


typedef enum {XrmBindTightly, XrmBindLoosely} XrmBinding, *XrmBindingList;


XrmBindTightly indicates that a period separates the compo-
nents, and XrmBindLoosely indicates that an asterisk sepa-
rates the components.


To convert a string with one or more components to a binding
list and a quark list, use XrmStringToBindingQuarkList.
__
|
XrmStringToBindingQuarkList(string, bindings_return, quarks_return)
     char *string;
     XrmBindingList bindings_return;
     XrmQuarkList quarks_return;


string	  Specifies the string for which a quark list is to
	  be allocated.

bindings_return
	  Returns the binding list.  The caller must allo-
	  cate sufficient space for the binding list before
	  calling XrmStringToBindingQuarkList.

quarks_return
	  Returns the list of quarks.  The caller must allo-
	  cate sufficient space for the quarks list before
	  calling XrmStringToBindingQuarkList.
|__

Component names in the list are separated by a period or an
asterisk character.  The string must be in the format of a
valid ResourceName (see section 15.1).	If the string does
not start with a period or an asterisk, a tight binding is
assumed.  For example, the string ``*a.b*c'' becomes:


quarks:        a      bc
bindings:      loose  tightloose






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15.4.  Creating and Storing Databases

A resource database is an opaque type, XrmDatabase.  Each
database value is stored in an XrmValue structure.  This
structure consists of a size, an address, and a representa-
tion type.  The size is specified in bytes.  The representa-
tion type is a way for you to store data tagged by some
application-defined type (for example, the strings ``font''
or ``color'').	It has nothing to do with the C data type or
with its class.  The XrmValue structure is defined as:

__
|
typedef struct {
     unsigned int size;
     XPointer addr;
} XrmValue, *XrmValuePtr;

|__


To initialize the resource manager, use XrmInitialize.
__
|
void XrmInitialize();

|__

To retrieve a database from disk, use XrmGetFileDatabase.
__
|
XrmDatabase XrmGetFileDatabase(filename)
     char *filename;


filename  Specifies the resource database file name.
|__

The XrmGetFileDatabase function opens the specified file,
creates a new resource database, and loads it with the spec-
ifications read in from the specified file.  The specified
file should contain a sequence of entries in valid Resource-
Line format (see section 15.1); the database that results
from reading a file with incorrect syntax is implementation-
dependent.  The file is parsed in the current locale, and
the database is created in the current locale.	If it cannot
open the specified file, XrmGetFileDatabase returns NULL.


To store a copy of a database to disk, use XrmPutFile-
Database.






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__
|
void XrmPutFileDatabase(database, stored_db)
     XrmDatabase database;
     char *stored_db;


database  Specifies the database that is to be used.

stored_db Specifies the file name for the stored database.
|__

The XrmPutFileDatabase function stores a copy of the speci-
fied database in the specified file.  Text is written to the
file as a sequence of entries in valid ResourceLine format
(see section 15.1).  The file is written in the locale of
the database.  Entries containing resource names that are
not in the Host Portable Character Encoding or containing
values that are not in the encoding of the database locale,
are written in an implementation-dependent manner.  The
order in which entries are written is implementation-depen-
dent.  Entries with representation types other than
``String'' are ignored.


To obtain a pointer to the screen-independent resources of a
display, use XResourceManagerString.
__
|
char *XResourceManagerString(display)
      Display *display;


display   Specifies the connection to the X server.
|__

The XResourceManagerString function returns the
RESOURCE_MANAGER property from the server's root window of
screen zero, which was returned when the connection was
opened using XOpenDisplay.  The property is converted from
type STRING to the current locale.  The conversion is iden-
tical to that produced by XmbTextPropertyToTextList for a
single element STRING property.  The returned string is
owned by Xlib and should not be freed by the client.  The
property value must be in a format that is acceptable to
XrmGetStringDatabase.  If no property exists, NULL is
returned.


To obtain a pointer to the screen-specific resources of a
screen, use XScreenResourceString.







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__
|
char *XScreenResourceString(screen)
      Screen *screen;


screen	  Specifies the screen.
|__

The XScreenResourceString function returns the
SCREEN_RESOURCES property from the root window of the speci-
fied screen.  The property is converted from type STRING to
the current locale.  The conversion is identical to that
produced by XmbTextPropertyToTextList for a single element
STRING property.  The property value must be in a format
that is acceptable to XrmGetStringDatabase.  If no property
exists, NULL is returned.  The caller is responsible for
freeing the returned string by using XFree.


To create a database from a string, use XrmGetString-
Database.
__
|
XrmDatabase XrmGetStringDatabase(data)
     char *data;


data	  Specifies the database contents using a string.
|__

The XrmGetStringDatabase function creates a new database and
stores the resources specified in the specified null-termi-
nated string.  XrmGetStringDatabase is similar to XrmGet-
FileDatabase except that it reads the information out of a
string instead of out of a file.  The string should contain
a sequence of entries in valid ResourceLine format (see sec-
tion 15.1) terminated by a null character; the database that
results from using a string with incorrect syntax is imple-
mentation-dependent.  The string is parsed in the current
locale, and the database is created in the current locale.


To obtain the locale name of a database, use XrmLocaleOf-
Database.
__
|
char *XrmLocaleOfDatabase(database)
      XrmDatabase database;


database  Specifies the resource database.
|__

The XrmLocaleOfDatabase function returns the name of the



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locale bound to the specified database, as a null-terminated
string.  The returned locale name string is owned by Xlib
and should not be modified or freed by the client.  Xlib is
not permitted to free the string until the database is
destroyed.  Until the string is freed, it will not be modi-
fied by Xlib.


To destroy a resource database and free its allocated mem-
ory, use XrmDestroyDatabase.
__
|
void XrmDestroyDatabase(database)
      XrmDatabase database;


database  Specifies the resource database.
|__

If database is NULL, XrmDestroyDatabase returns immediately.


To associate a resource database with a display, use XrmSet-
Database.
__
|
void XrmSetDatabase(display, database)
      Display *display;
      XrmDatabase database;


display   Specifies the connection to the X server.

database  Specifies the resource database.
|__

The XrmSetDatabase function associates the specified
resource database (or NULL) with the specified display.  The
database previously associated with the display (if any) is
not destroyed.	A client or toolkit may find this function
convenient for retaining a database once it is constructed.


To get the resource database associated with a display, use
XrmGetDatabase.












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__
|
XrmDatabase XrmGetDatabase(display)
      Display *display;


display   Specifies the connection to the X server.
|__

The XrmGetDatabase function returns the database associated
with the specified display.  It returns NULL if a database
has not yet been set.

15.5.  Merging Resource Databases

To merge the contents of a resource file into a database,
use XrmCombineFileDatabase.
__
|
Status XrmCombineFileDatabase(filename, target_db, override)
      char *filename;
      XrmDatabase *target_db;
      Bool override;


filename  Specifies the resource database file name.

target_db Specifies the resource database into which the
	  source database is to be merged.

override  Specifies whether source entries override target
	  ones.
|__

The XrmCombineFileDatabase function merges the contents of a
resource file into a database.	If the same specifier is
used for an entry in both the file and the database, the
entry in the file will replace the entry in the database if
override is True; otherwise, the entry in the file is dis-
carded.  The file is parsed in the current locale.  If the
file cannot be read, a zero status is returned; otherwise, a
nonzero status is returned.  If target_db contains NULL,
XrmCombineFileDatabase creates and returns a new database to
it.  Otherwise, the database pointed to by target_db is not
destroyed by the merge.  The database entries are merged
without changing values or types, regardless of the locale
of the database.  The locale of the target database is not
modified.


To merge the contents of one database into another database,
use XrmCombineDatabase.






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__
|
void XrmCombineDatabase(source_db, target_db, override)
      XrmDatabase source_db, *target_db;
      Bool override;


source_db Specifies the resource database that is to be
	  merged into the target database.

target_db Specifies the resource database into which the
	  source database is to be merged.

override  Specifies whether source entries override target
	  ones.
|__

The XrmCombineDatabase function merges the contents of one
database into another.	If the same specifier is used for an
entry in both databases, the entry in the source_db will
replace the entry in the target_db if override is True; oth-
erwise, the entry in source_db is discarded.  If target_db
contains NULL, XrmCombineDatabase simply stores source_db in
it.  Otherwise, source_db is destroyed by the merge, but the
database pointed to by target_db is not destroyed.  The
database entries are merged without changing values or
types, regardless of the locales of the databases.  The
locale of the target database is not modified.


To merge the contents of one database into another database
with override semantics, use XrmMergeDatabases.
__
|
void XrmMergeDatabases(source_db, target_db)
      XrmDatabase source_db, *target_db;


source_db Specifies the resource database that is to be
	  merged into the target database.

target_db Specifies the resource database into which the
	  source database is to be merged.
|__

Calling the XrmMergeDatabases function is equivalent to
calling the XrmCombineDatabase function with an override
argument of True.

15.6.  Looking Up Resources

To retrieve a resource from a resource database, use XrmGe-
tResource, XrmQGetResource, or XrmQGetSearchResource.





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__
|
Bool XrmGetResource(database, str_name, str_class, str_type_return, value_return)
     XrmDatabase database;
     char *str_name;
     char *str_class;
     char **str_type_return;
     XrmValue *value_return;


database  Specifies the database that is to be used.

str_name  Specifies the fully qualified name of the value
	  being retrieved (as a string).

str_class Specifies the fully qualified class of the value
	  being retrieved (as a string).

str_type_return
	  Returns the representation type of the destination
	  (as a string).

value_return
	  Returns the value in the database.
|__

































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__
|
Bool XrmQGetResource(database, quark_name, quark_class, quark_type_return, value_return)
     XrmDatabase database;
     XrmNameList quark_name;
     XrmClassList quark_class;
     XrmRepresentation *quark_type_return;
     XrmValue *value_return;


database  Specifies the database that is to be used.

quark_name
	  Specifies the fully qualified name of the value
	  being retrieved (as a quark).

quark_class
	  Specifies the fully qualified class of the value
	  being retrieved (as a quark).

quark_type_return
	  Returns the representation type of the destination
	  (as a quark).

value_return
	  Returns the value in the database.
|__

The XrmGetResource and XrmQGetResource functions retrieve a
resource from the specified database.  Both take a fully
qualified name/class pair, a destination resource represen-
tation, and the address of a value (size/address pair).  The
value and returned type point into database memory; there-
fore, you must not modify the data.

The database only frees or overwrites entries on XrmPutRe-
source, XrmQPutResource, or XrmMergeDatabases.	A client
that is not storing new values into the database or is not
merging the database should be safe using the address passed
back at any time until it exits.  If a resource was found,
both XrmGetResource and XrmQGetResource return True; other-
wise, they return False.


Most applications and toolkits do not make random probes
into a resource database to fetch resources.  The X toolkit
access pattern for a resource database is quite stylized.  A
series of from 1 to 20 probes is made with only the last
name/class differing in each probe.  The XrmGetResource
function is at worst a 2n algorithm, where n is the length
of the name/class list.  This can be improved upon by the
application programmer by prefetching a list of database
levels that might match the first part of a name/class list.





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To obtain a list of database levels, use XrmQGetSearchList.
__
|
typedef XrmHashTable *XrmSearchList;

Bool XrmQGetSearchList(database, names, classes, list_return, list_length)
     XrmDatabase database;
     XrmNameList names;
     XrmClassList classes;
     XrmSearchList list_return;
     int list_length;


database  Specifies the database that is to be used.

names	  Specifies a list of resource names.

classes   Specifies a list of resource classes.

list_return
	  Returns a search list for further use.  The caller
	  must allocate sufficient space for the list before
	  calling XrmQGetSearchList.

list_length
	  Specifies the number of entries (not the byte
	  size) allocated for list_return.
|__

The XrmQGetSearchList function takes a list of names and
classes and returns a list of database levels where a match
might occur.  The returned list is in best-to-worst order
and uses the same algorithm as XrmGetResource for determin-
ing precedence.  If list_return was large enough for the
search list, XrmQGetSearchList returns True; otherwise, it
returns False.

The size of the search list that the caller must allocate is
dependent upon the number of levels and wildcards in the
resource specifiers that are stored in the database.  The
worst case length is 3n, where n is the number of name or
class components in names or classes.

When using XrmQGetSearchList followed by multiple probes for
resources with a common name and class prefix, only the com-
mon prefix should be specified in the name and class list to
XrmQGetSearchList.


To search resource database levels for a given resource, use
XrmQGetSearchResource.






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__
|
Bool XrmQGetSearchResource(list, name, class, type_return, value_return)
     XrmSearchList list;
     XrmName name;
     XrmClass class;
     XrmRepresentation *type_return;
     XrmValue *value_return;


list	  Specifies the search list returned by XrmQGet-
	  SearchList.

name	  Specifies the resource name.

class	  Specifies the resource class.

type_return
	  Returns data representation type.

value_return
	  Returns the value in the database.
|__

The XrmQGetSearchResource function searches the specified
database levels for the resource that is fully identified by
the specified name and class.  The search stops with the
first match.  XrmQGetSearchResource returns True if the
resource was found; otherwise, it returns False.

A call to XrmQGetSearchList with a name and class list con-
taining all but the last component of a resource name fol-
lowed by a call to XrmQGetSearchResource with the last com-
ponent name and class returns the same database entry as
XrmGetResource and XrmQGetResource with the fully qualified
name and class.

15.7.  Storing into a Resource Database

To store resources into the database, use XrmPutResource or
XrmQPutResource.  Both functions take a partial resource
specification, a representation type, and a value.  This
value is copied into the specified database.















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__
|
void XrmPutResource(database, specifier, type, value)
     XrmDatabase *database;
     char *specifier;
     char *type;
     XrmValue *value;


database  Specifies the resource database.

specifier Specifies a complete or partial specification of
	  the resource.

type	  Specifies the type of the resource.

value	  Specifies the value of the resource, which is
	  specified as a string.
|__

If database contains NULL, XrmPutResource creates a new
database and returns a pointer to it.  XrmPutResource is a
convenience function that calls XrmStringToBindingQuarkList
followed by:


     XrmQPutResource(database, bindings, quarks, XrmStringToQuark(type), value)

If the specifier and type are not in the Host Portable Char-
acter Encoding, the result is implementation-dependent.  The
value is stored in the database without modification.



























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__
|
void XrmQPutResource(database, bindings, quarks, type, value)
     XrmDatabase *database;
     XrmBindingList bindings;
     XrmQuarkList quarks;
     XrmRepresentation type;
     XrmValue *value;


database  Specifies the resource database.

bindings  Specifies a list of bindings.

quarks	  Specifies the complete or partial name or the
	  class list of the resource.

type	  Specifies the type of the resource.

value	  Specifies the value of the resource, which is
	  specified as a string.
|__

If database contains NULL, XrmQPutResource creates a new
database and returns a pointer to it.  If a resource entry
with the identical bindings and quarks already exists in the
database, the previous type and value are replaced by the
new specified type and value.  The value is stored in the
database without modification.


To add a resource that is specified as a string, use XrmPut-
StringResource.
__
|
void XrmPutStringResource(database, specifier, value)
     XrmDatabase *database;
     char *specifier;
     char *value;


database  Specifies the resource database.

specifier Specifies a complete or partial specification of
	  the resource.

value	  Specifies the value of the resource, which is
	  specified as a string.
|__

If database contains NULL, XrmPutStringResource creates a
new database and returns a pointer to it.  XrmPutStringRe-
source adds a resource with the specified value to the spec-
ified database.  XrmPutStringResource is a convenience func-
tion that first calls XrmStringToBindingQuarkList on the



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specifier and then calls XrmQPutResource, using a ``String''
representation type.  If the specifier is not in the Host
Portable Character Encoding, the result is implementation-
dependent.  The value is stored in the database without mod-
ification.


To add a string resource using quarks as a specification,
use XrmQPutStringResource.
__
|
void XrmQPutStringResource(database, bindings, quarks, value)
     XrmDatabase *database;
     XrmBindingList bindings;
     XrmQuarkList quarks;
     char *value;


database  Specifies the resource database.

bindings  Specifies a list of bindings.

quarks	  Specifies the complete or partial name or the
	  class list of the resource.

value	  Specifies the value of the resource, which is
	  specified as a string.
|__

If database contains NULL, XrmQPutStringResource creates a
new database and returns a pointer to it.  XrmQPutStringRe-
source is a convenience routine that constructs an XrmValue
for the value string (by calling strlen to compute the size)
and then calls XrmQPutResource, using a ``String'' represen-
tation type.  The value is stored in the database without
modification.


To add a single resource entry that is specified as a string
that contains both a name and a value, use XrmPutLineRe-
source.
















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__
|
void XrmPutLineResource(database, line)
     XrmDatabase *database;
     char *line;


database  Specifies the resource database.

line	  Specifies the resource name and value pair as a
	  single string.
|__

If database contains NULL, XrmPutLineResource creates a new
database and returns a pointer to it.  XrmPutLineResource
adds a single resource entry to the specified database.  The
line should be in valid ResourceLine format (see section
15.1) terminated by a newline or null character; the
database that results from using a string with incorrect
syntax is implementation-dependent.  The string is parsed in
the locale of the database.  If the ResourceName is not in
the Host Portable Character Encoding, the result is imple-
mentation-dependent.  Note that comment lines are not
stored.

15.8.  Enumerating Database Entries

To enumerate the entries of a database, use XrmEnumerate-
Database.





























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__
|
#define   XrmEnumAllLevels	 0
#define   XrmEnumOneLevel	 1


Bool XrmEnumerateDatabase(database, name_prefix, class_prefix, mode, proc, arg)
      XrmDatabase database;
      XrmNameList name_prefix;
      XrmClassList class_prefix;
      int mode;
      Bool (*proc)();
      XPointer arg;


database  Specifies the resource database.

name_prefix
	  Specifies the resource name prefix.

class_prefix
	  Specifies the resource class prefix.

mode	  Specifies the number of levels to enumerate.

proc	  Specifies the procedure that is to be called for
	  each matching entry.

arg	  Specifies the user-supplied argument that will be
	  passed to the procedure.
|__

The XrmEnumerateDatabase function calls the specified proce-
dure for each resource in the database that would match some
completion of the given name/class resource prefix.  The
order in which resources are found is implementation-depen-
dent.  If mode is XrmEnumOneLevel, a resource must match the
given name/class prefix with just a single name and class
appended.  If mode is XrmEnumAllLevels, the resource must
match the given name/class prefix with one or more names and
classes appended.  If the procedure returns True, the enu-
meration terminates and the function returns True.  If the
procedure always returns False, all matching resources are
enumerated and the function returns False.

The procedure is called with the following arguments:


(*proc)(database, bindings, quarks, type, value, arg)
     XrmDatabase *database;
     XrmBindingList bindings;
     XrmQuarkList quarks;
     XrmRepresentation *type;
     XrmValue *value;
     XPointer arg;



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The bindings and quarks lists are terminated by NULLQUARK.
Note that pointers to the database and type are passed, but
these values should not be modified.

The procedure must not modify the database.  If Xlib has
been initialized for threads, the procedure is called with
the database locked and the result of a call by the proce-
dure to any Xlib function using the same database is not
defined.

15.9.  Parsing Command Line Options

The XrmParseCommand function can be used to parse the com-
mand line arguments to a program and modify a resource
database with selected entries from the command line.

__
|
typedef enum {
     XrmoptionNoArg,	 /* Value is specified in XrmOptionDescRec.value */
     XrmoptionIsArg,	 /* Value is the option string itself */
     XrmoptionStickyArg, /* Value is characters immediately following option */
     XrmoptionSepArg,	 /* Value is next argument in argv */
     XrmoptionResArg,	 /* Resource and value in next argument in argv */
     XrmoptionSkipArg,	 /* Ignore this option and the next argument in argv */
     XrmoptionSkipLine,  /* Ignore this option and the rest of argv */
     XrmoptionSkipNArgs  /* Ignore this option and the next
			    XrmOptionDescRec.value arguments in argv */
} XrmOptionKind;

|__

Note that XrmoptionSkipArg is equivalent to XrmoptionSkip-
NArgs with the XrmOptionDescRec.value field containing the
value one.  Note also that the value zero for XrmoptionSkip-
NArgs indicates that only the option itself is to be
skipped.

__
|
typedef struct {
     char *option;	 /* Option specification string in argv    */
     char *specifier;	 /* Binding and resource name (sans application name)	 */
     XrmOptionKind argKind;/* Which style of option it is    */
     XPointer value;	 /* Value to provide if XrmoptionNoArg or
			    XrmoptionSkipNArgs	 */
} XrmOptionDescRec, *XrmOptionDescList;

|__


To load a resource database from a C command line, use Xrm-
ParseCommand.




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__
|
void XrmParseCommand(database, table, table_count, name, argc_in_out, argv_in_out)
      XrmDatabase *database;
      XrmOptionDescList table;
      int table_count;
      char *name;
      int *argc_in_out;
      char **argv_in_out;


database  Specifies the resource database.

table	  Specifies the table of command line arguments to
	  be parsed.

table_count
	  Specifies the number of entries in the table.

name	  Specifies the application name.

argc_in_out
	  Specifies the number of arguments and returns the
	  number of remaining arguments.

argv_in_out
	  Specifies the command line arguments and returns
	  the remaining arguments.
|__

The XrmParseCommand function parses an (argc, argv) pair
according to the specified option table, loads recognized
options into the specified database with type ``String,''
and modifies the (argc, argv) pair to remove all recognized
options.  If database contains NULL, XrmParseCommand creates
a new database and returns a pointer to it.  Otherwise,
entries are added to the database specified.  If a database
is created, it is created in the current locale.

The specified table is used to parse the command line.	Rec-
ognized options in the table are removed from argv, and
entries are added to the specified resource database in the
order they occur in argv.  The table entries contain infor-
mation on the option string, the option name, the style of
option, and a value to provide if the option kind is Xrmop-
tionNoArg.  The option names are compared byte-for-byte to
arguments in argv, independent of any locale.  The resource
values given in the table are stored in the resource
database without modification.	All resource database
entries are created using a ``String'' representation type.
The argc argument specifies the number of arguments in argv
and is set on return to the remaining number of arguments
that were not parsed.  The name argument should be the name
of your application for use in building the database entry.
The name argument is prefixed to the resourceName in the



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option table before storing a database entry.  The name
argument is treated as a single component, even if it has
embedded periods.  No separating (binding) character is
inserted, so the table must contain either a period (.) or
an asterisk (*) as the first character in each resourceName
entry.	To specify a more completely qualified resource
name, the resourceName entry can contain multiple compo-
nents.	If the name argument and the resourceNames are not
in the Host Portable Character Encoding, the result is
implementation-dependent.

The following provides a sample option table:


static XrmOptionDescRec opTable[] = {
{"-background", 		"*background", XrmoptionSepArg,(XPointer) NULL},
{"-bd",     "*borderColor",	XrmoptionSepArg,(XPointer) NULL},
{"-bg",     "*background",	XrmoptionSepArg,(XPointer) NULL},
{"-borderwidth",		"*TopLevelShell.borderWidth",XrmoptionSepArg,(XPointer) NULL},
{"-bordercolor",		"*borderColor",XrmoptionSepArg,(XPointer) NULL},
{"-bw",     "*TopLevelShell.borderWidth",      XrmoptionSepArg,(XPointer) NULL},
{"-display",			".display",    XrmoptionSepArg,(XPointer) NULL},
{"-fg",     "*foreground",	XrmoptionSepArg,(XPointer) NULL},
{"-fn",     "*font",		XrmoptionSepArg,(XPointer) NULL},
{"-font",   "*font",		XrmoptionSepArg,(XPointer) NULL},
{"-foreground", 		"*foreground", XrmoptionSepArg,(XPointer) NULL},
{"-geometry",			".TopLevelShell.geometry",XrmoptionSepArg,(XPointer) NULL},
{"-iconic", ".TopLevelShell.iconic",	       XrmoptionNoArg,(XPointer) "on"},
{"-name",   ".name",		XrmoptionSepArg,(XPointer) NULL},
{"-reverse",			"*reverseVideo",XrmoptionNoArg,(XPointer) "on"},
{"-rv",     "*reverseVideo",	XrmoptionNoArg,(XPointer) "on"},
{"-synchronous",		"*synchronous",XrmoptionNoArg,(XPointer) "on"},
{"-title",  ".TopLevelShell.title",	       XrmoptionSepArg,(XPointer) NULL},
{"-xrm",    NULL,		XrmoptionResArg,(XPointer) NULL},
};


In this table, if the -background (or -bg) option is used to
set background colors, the stored resource specifier matches
all resources of attribute background.	If the -borderwidth
option is used, the stored resource specifier applies only
to border width attributes of class TopLevelShell (that is,
outer-most windows, including pop-up windows).	If the
-title option is used to set a window name, only the topmost
application windows receive the resource.

When parsing the command line, any unique unambiguous abbre-
viation for an option name in the table is considered a
match for the option.  Note that uppercase and lowercase
matter.







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			 Chapter 16

	       Application Utility Functions



Once you have initialized the X system, you can use the Xlib
utility functions to:

o    Use keyboard utility functions

o    Use Latin-1 keyboard event functions

o    Allocate permanent storage

o    Parse the window geometry

o    Manipulate regions

o    Use cut buffers

o    Determine the appropriate visual type

o    Manipulate images

o    Manipulate bitmaps

o    Use the context manager

As a group, the functions discussed in this chapter provide
the functionality that is frequently needed and that spans
toolkits.  Many of these functions do not generate actual
protocol requests to the server.

16.1.  Using Keyboard Utility Functions

This section discusses mapping between KeyCodes and KeySyms,
classifying KeySyms, and mapping between KeySyms and string
names.	The first three functions in this section operate on
a cached copy of the server keyboard mapping.  The first
four KeySyms for each KeyCode are modified according to the
rules given in section 12.7.  To obtain the untransformed
KeySyms defined for a key, use the functions described in
section 12.7.


To obtain a KeySym for the KeyCode of an event, use XLookup-
Keysym.







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__
|
KeySym XLookupKeysym(key_event, index)
      XKeyEvent *key_event;
      int index;


key_event Specifies the KeyPress or KeyRelease event.

index	  Specifies the index into the KeySyms list for the
	  event's KeyCode.
|__

The XLookupKeysym function uses a given keyboard event and
the index you specified to return the KeySym from the list
that corresponds to the KeyCode member in the XKeyPressedE-
vent or XKeyReleasedEvent structure.  If no KeySym is
defined for the KeyCode of the event, XLookupKeysym returns
NoSymbol.


To obtain a KeySym for a specific KeyCode, use XKey-
codeToKeysym.
__
|
KeySym XKeycodeToKeysym(display, keycode, index)
      Display *display;
      KeyCode keycode;
      int index;


display   Specifies the connection to the X server.

keycode   Specifies the KeyCode.

index	  Specifies the element of KeyCode vector.
|__

The XKeycodeToKeysym function uses internal Xlib tables and
returns the KeySym defined for the specified KeyCode and the
element of the KeyCode vector.	If no symbol is defined,
XKeycodeToKeysym returns NoSymbol.


To obtain a KeyCode for a key having a specific KeySym, use
XKeysymToKeycode.












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__
|
KeyCode XKeysymToKeycode(display, keysym)
      Display *display;
      KeySym keysym;


display   Specifies the connection to the X server.

keysym	  Specifies the KeySym that is to be searched for.
|__

If the specified KeySym is not defined for any KeyCode,
XKeysymToKeycode returns zero.


The mapping between KeyCodes and KeySyms is cached internal
to Xlib.  When this information is changed at the server, an
Xlib function must be called to refresh the cache.  To
refresh the stored modifier and keymap information, use XRe-
freshKeyboardMapping.
__
|
XRefreshKeyboardMapping(event_map)
      XMappingEvent *event_map;


event_map Specifies the mapping event that is to be used.
|__

The XRefreshKeyboardMapping function refreshes the stored
modifier and keymap information.  You usually call this
function when a MappingNotify event with a request member of
MappingKeyboard or MappingModifier occurs.  The result is to
update Xlib's knowledge of the keyboard.


To obtain the uppercase and lowercase forms of a KeySym, use
XConvertCase.



















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__
|
void XConvertCase(keysym, lower_return, upper_return)
      KeySym keysym;
      KeySym *lower_return;
      KeySym *upper_return;


keysym	  Specifies the KeySym that is to be converted.

lower_return
	  Returns the lowercase form of keysym, or keysym.

upper_return
	  Returns the uppercase form of keysym, or keysym.
|__

The XConvertCase function returns the uppercase and lower-
case forms of the specified Keysym, if the KeySym is subject
to case conversion; otherwise, the specified KeySym is
returned to both lower_return and upper_return.  Support for
conversion of other than Latin and Cyrillic KeySyms is
implementation-dependent.


KeySyms have string names as well as numeric codes.  To con-
vert the name of the KeySym to the KeySym code, use XString-
ToKeysym.
__
|
KeySym XStringToKeysym(string)
      char *string;


string	  Specifies the name of the KeySym that is to be
	  converted.
|__

Standard KeySym names are obtained from <X11/keysymdef.h> by
removing the XK_ prefix from each name.  KeySyms that are
not part of the Xlib standard also may be obtained with this
function.  The set of KeySyms that are available in this
manner and the mechanisms by which Xlib obtains them is
implementation-dependent.

If the KeySym name is not in the Host Portable Character
Encoding, the result is implementation-dependent.  If the
specified string does not match a valid KeySym, XString-
ToKeysym returns NoSymbol.


To convert a KeySym code to the name of the KeySym, use
XKeysymToString.





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__
|
char *XKeysymToString(keysym)
      KeySym keysym;


keysym	  Specifies the KeySym that is to be converted.
|__

The returned string is in a static area and must not be mod-
ified.	The returned string is in the Host Portable Charac-
ter Encoding.  If the specified KeySym is not defined,
XKeysymToString returns a NULL.

16.1.1.  KeySym Classification Macros

You may want to test if a KeySym is, for example, on the
keypad or on one of the function keys.	You can use KeySym
macros to perform the following tests.


__
|
IsCursorKey(keysym)


keysym	  Specifies the KeySym that is to be tested.
|__

Returns True if the specified KeySym is a cursor key.


__
|
IsFunctionKey(keysym)


keysym	  Specifies the KeySym that is to be tested.
|__

Returns True if the specified KeySym is a function key.


__
|
IsKeypadKey(keysym)


keysym	  Specifies the KeySym that is to be tested.
|__

Returns True if the specified KeySym is a standard keypad
key.





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__
|
IsPrivateKeypadKey(keysym)


keysym	  Specifies the KeySym that is to be tested.
|__

Returns True if the specified KeySym is a vendor-private
keypad key.


__
|
IsMiscFunctionKey(keysym)


keysym	  Specifies the KeySym that is to be tested.
|__

Returns True if the specified KeySym is a miscellaneous
function key.


__
|
IsModifierKey(keysym)


keysym	  Specifies the KeySym that is to be tested.
|__

Returns True if the specified KeySym is a modifier key.


__
|
IsPFKey(keysym)


keysym	  Specifies the KeySym that is to be tested.
|__

Returns True if the specified KeySym is a PF key.

16.2.  Using Latin-1 Keyboard Event Functions

Chapter 13 describes internationalized text input facili-
ties, but sometimes it is expedient to write an application
that only deals with Latin-1 characters and ASCII controls,
so Xlib provides a simple function for that purpose.
XLookupString handles the standard modifier semantics
described in section 12.7.  This function does not use any
of the input method facilities described in chapter 13 and
does not depend on the current locale.



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To map a key event to an ISO Latin-1 string, use XLookup-
String.
__
|
int XLookupString(event_struct, buffer_return, bytes_buffer, keysym_return, status_in_out)
      XKeyEvent *event_struct;
      char *buffer_return;
      int bytes_buffer;
      KeySym *keysym_return;
      XComposeStatus *status_in_out;


event_struct
	  Specifies the key event structure to be used.  You
	  can pass XKeyPressedEvent or XKeyReleasedEvent.

buffer_return
	  Returns the translated characters.

bytes_buffer
	  Specifies the length of the buffer.  No more than
	  bytes_buffer of translation are returned.

keysym_return
	  Returns the KeySym computed from the event if this
	  argument is not NULL.

status_in_out
	  Specifies or returns the XComposeStatus structure
	  or NULL.
|__

The XLookupString function translates a key event to a
KeySym and a string.  The KeySym is obtained by using the
standard interpretation of the Shift, Lock, group, and num-
lock modifiers as defined in the X Protocol specification.
If the KeySym has been rebound (see XRebindKeysym), the
bound string will be stored in the buffer.  Otherwise, the
KeySym is mapped, if possible, to an ISO Latin-1 character
or (if the Control modifier is on) to an ASCII control char-
acter, and that character is stored in the buffer.  XLookup-
String returns the number of characters that are stored in
the buffer.

If present (non-NULL), the XComposeStatus structure records
the state, which is private to Xlib, that needs preservation
across calls to XLookupString to implement compose process-
ing.  The creation of XComposeStatus structures is implemen-
tation-dependent; a portable program must pass NULL for this
argument.

XLookupString depends on the cached keyboard information
mentioned in the previous section, so it is necessary to use
XRefreshKeyboardMapping to keep this information up-to-date.



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To rebind the meaning of a KeySym for XLookupString, use
XRebindKeysym.
__
|
XRebindKeysym(display, keysym, list, mod_count, string, num_bytes)
      Display *display;
      KeySym keysym;
      KeySym list[];
      int mod_count;
      unsigned char *string;
      int num_bytes;


display   Specifies the connection to the X server.

keysym	  Specifies the KeySym that is to be rebound.

list	  Specifies the KeySyms to be used as modifiers.

mod_count Specifies the number of modifiers in the modifier
	  list.

string	  Specifies the string that is copied and will be
	  returned by XLookupString.

num_bytes Specifies the number of bytes in the string argu-
	  ment.
|__

The XRebindKeysym function can be used to rebind the meaning
of a KeySym for the client.  It does not redefine any key in
the X server but merely provides an easy way for long
strings to be attached to keys.  XLookupString returns this
string when the appropriate set of modifier keys are pressed
and when the KeySym would have been used for the transla-
tion.  No text conversions are performed; the client is
responsible for supplying appropriately encoded strings.
Note that you can rebind a KeySym that may not exist.

16.3.  Allocating Permanent Storage

To allocate some memory you will never give back, use
Xpermalloc.
__
|
char *Xpermalloc(size)
     unsigned int size;

|__

The Xpermalloc function allocates storage that can never be
freed for the life of the program.  The memory is allocated
with alignment for the C type double.  This function may
provide some performance and space savings over the standard



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operating system memory allocator.

16.4.  Parsing the Window Geometry

To parse standard window geometry strings, use XParseGeome-
try.

__
|
int XParseGeometry(parsestring, x_return, y_return, width_return, height_return)
      char *parsestring;
      int *x_return, *y_return;
      unsigned int *width_return, *height_return;


parsestring
	  Specifies the string you want to parse.

x_return
y_return  Return the x and y offsets.

width_return
height_return
	  Return the width and height determined.
|__

By convention, X applications use a standard string to indi-
cate window size and placement.  XParseGeometry makes it
easier to conform to this standard because it allows you to
parse the standard window geometry.  Specifically, this
function lets you parse strings of the form:


     [=][<width>{xX}<height>][{+-}<xoffset>{+-}<yoffset>]


The fields map into the arguments associated with this func-
tion.  (Items enclosed in <> are integers, items in [] are
optional, and items enclosed in {} indicate ``choose one
of.''  Note that the brackets should not appear in the
actual string.)  If the string is not in the Host Portable
Character Encoding, the result is implementation-dependent.

The XParseGeometry function returns a bitmask that indicates
which of the four values (width, height, xoffset, and yoff-
set) were actually found in the string and whether the x and
y values are negative.	By convention, -0 is not equal to
+0, because the user needs to be able to say ``position the
window relative to the right or bottom edge.''	For each
value found, the corresponding argument is updated.  For
each value not found, the argument is left unchanged.  The
bits are represented by XValue, YValue, WidthValue, Height-
Value, XNegative, or YNegative and are defined in
<X11/Xutil.h>.	They will be set whenever one of the values



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is defined or one of the signs is set.

If the function returns either the XValue or YValue flag,
you should place the window at the requested position.


To construct a window's geometry information, use XWMGeome-
try.
__
|
int XWMGeometry(display, screen, user_geom, def_geom, bwidth, hints, x_return, y_return,
		width_return, height_return, gravity_return)
      Display *display;
      int screen;
      char *user_geom;
      char *def_geom;
      unsigned int bwidth;
      XSizeHints *hints;
      int *x_return, *y_return;
      int *width_return;
      int *height_return;
      int *gravity_return;


display   Specifies the connection to the X server.

screen	  Specifies the screen.

user_geom Specifies the user-specified geometry or NULL.

def_geom  Specifies the application's default geometry or
	  NULL.

bwidth	  Specifies the border width.

hints	  Specifies the size hints for the window in its
	  normal state.

x_return
y_return  Return the x and y offsets.

width_return
height_return
	  Return the width and height determined.

gravity_return
	  Returns the window gravity.
|__

The XWMGeometry function combines any geometry information
(given in the format used by XParseGeometry) specified by
the user and by the calling program with size hints (usually
the ones to be stored in WM_NORMAL_HINTS) and returns the
position, size, and gravity (NorthWestGravity,



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NorthEastGravity, SouthEastGravity, or SouthWestGravity)
that describe the window.  If the base size is not set in
the XSizeHints structure, the minimum size is used if set.
Otherwise, a base size of zero is assumed.  If no minimum
size is set in the hints structure, the base size is used.
A mask (in the form returned by XParseGeometry) that
describes which values came from the user specification and
whether or not the position coordinates are relative to the
right and bottom edges is returned.  Note that these coordi-
nates will have already been accounted for in the x_return
and y_return values.

Note that invalid geometry specifications can cause a width
or height of zero to be returned.  The caller may pass the
address of the hints win_gravity field as gravity_return to
update the hints directly.

16.5.  Manipulating Regions

Regions are arbitrary sets of pixel locations.	Xlib pro-
vides functions for manipulating regions.  The opaque type
Region is defined in <X11/Xutil.h>.  Xlib provides functions
that you can use to manipulate regions.  This section dis-
cusses how to:

o    Create, copy, or destroy regions

o    Move or shrink regions

o    Compute with regions

o    Determine if regions are empty or equal

o    Locate a point or rectangle in a region

16.5.1.  Creating, Copying, or Destroying Regions

To create a new empty region, use XCreateRegion.
__
|
Region XCreateRegion()

|__


To generate a region from a polygon, use XPolygonRegion.











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__
|
Region XPolygonRegion(points, n, fill_rule)
      XPoint points[];
      int n;
      int fill_rule;


points	  Specifies an array of points.

n	  Specifies the number of points in the polygon.

fill_rule Specifies the fill-rule you want to set for the
	  specified GC.  You can pass EvenOddRule or Windin-
	  gRule.
|__

The XPolygonRegion function returns a region for the polygon
defined by the points array.  For an explanation of
fill_rule, see XCreateGC.


To set the clip-mask of a GC to a region, use XSetRegion.
__
|
XSetRegion(display, gc, r)
      Display *display;
      GC gc;
      Region r;


display   Specifies the connection to the X server.

gc	  Specifies the GC.

r	  Specifies the region.
|__

The XSetRegion function sets the clip-mask in the GC to the
specified region.  The region is specified relative to the
drawable's origin.  The resulting GC clip origin is imple-
mentation-dependent.  Once it is set in the GC, the region
can be destroyed.


To deallocate the storage associated with a specified
region, use XDestroyRegion.











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__
|
XDestroyRegion(r)
      Region r;


r	  Specifies the region.
|__


16.5.2.  Moving or Shrinking Regions

To move a region by a specified amount, use XOffsetRegion.
__
|
XOffsetRegion(r, dx, dy)
      Region r;
      int dx, dy;


r	  Specifies the region.

dx
dy	  Specify the x and y coordinates, which define the
	  amount you want to move the specified region.
|__


To reduce a region by a specified amount, use XShrinkRegion.
__
|
XShrinkRegion(r, dx, dy)
      Region r;
      int dx, dy;


r	  Specifies the region.

dx
dy	  Specify the x and y coordinates, which define the
	  amount you want to shrink the specified region.
|__

Positive values shrink the size of the region, and negative
values expand the region.

16.5.3.  Computing with Regions


To generate the smallest rectangle enclosing a region, use
XClipBox.







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__
|
XClipBox(r, rect_return)
      Region r;
      XRectangle *rect_return;


r	  Specifies the region.

rect_return
	  Returns the smallest enclosing rectangle.
|__

The XClipBox function returns the smallest rectangle enclos-
ing the specified region.


To compute the intersection of two regions, use XIntersec-
tRegion.
__
|
XIntersectRegion(sra, srb, dr_return)
      Region sra, srb, dr_return;


sra
srb	  Specify the two regions with which you want to
	  perform the computation.

dr_return Returns the result of the computation.
|__


To compute the union of two regions, use XUnionRegion.
__
|
XUnionRegion(sra, srb, dr_return)
      Region sra, srb, dr_return;


sra
srb	  Specify the two regions with which you want to
	  perform the computation.

dr_return Returns the result of the computation.
|__


To create a union of a source region and a rectangle, use
XUnionRectWithRegion.








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__
|
XUnionRectWithRegion(rectangle, src_region, dest_region_return)
     XRectangle *rectangle;
     Region src_region;
     Region dest_region_return;


rectangle Specifies the rectangle.

src_region
	  Specifies the source region to be used.

dest_region_return
	  Returns the destination region.
|__

The XUnionRectWithRegion function updates the destination
region from a union of the specified rectangle and the spec-
ified source region.


To subtract two regions, use XSubtractRegion.
__
|
XSubtractRegion(sra, srb, dr_return)
      Region sra, srb, dr_return;


sra
srb	  Specify the two regions with which you want to
	  perform the computation.

dr_return Returns the result of the computation.
|__

The XSubtractRegion function subtracts srb from sra and
stores the results in dr_return.


To calculate the difference between the union and intersec-
tion of two regions, use XXorRegion.
















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__
|
XXorRegion(sra, srb, dr_return)
      Region sra, srb, dr_return;


sra
srb	  Specify the two regions with which you want to
	  perform the computation.

dr_return Returns the result of the computation.
|__


16.5.4.  Determining if Regions Are Empty or Equal

To determine if the specified region is empty, use XEmptyRe-
gion.
__
|
Bool XEmptyRegion(r)
      Region r;


r	  Specifies the region.
|__

The XEmptyRegion function returns True if the region is
empty.


To determine if two regions have the same offset, size, and
shape, use XEqualRegion.
__
|
Bool XEqualRegion(r1, r2)
      Region r1, r2;


r1
r2	  Specify the two regions.
|__

The XEqualRegion function returns True if the two regions
have the same offset, size, and shape.

16.5.5.  Locating a Point or a Rectangle in a Region

To determine if a specified point resides in a specified
region, use XPointInRegion.








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__
|
Bool XPointInRegion(r, x, y)
      Region r;
      int x, y;


r	  Specifies the region.

x
y	  Specify the x and y coordinates, which define the
	  point.
|__

The XPointInRegion function returns True if the point (x, y)
is contained in the region r.


To determine if a specified rectangle is inside a region,
use XRectInRegion.
__
|
int XRectInRegion(r, x, y, width, height)
      Region r;
      int x, y;
      unsigned int width, height;


r	  Specifies the region.

x
y	  Specify the x and y coordinates, which define the
	  coordinates of the upper-left corner of the rect-
	  angle.

width
height	  Specify the width and height, which define the
	  rectangle.
|__

The XRectInRegion function returns RectangleIn if the rect-
angle is entirely in the specified region, RectangleOut if
the rectangle is entirely out of the specified region, and
RectanglePart if the rectangle is partially in the specified
region.

16.6.  Using Cut Buffers

Xlib provides functions to manipulate cut buffers, a very
simple form of cut-and-paste inter-client communication.
Selections are a much more powerful and useful mechanism for
interchanging data between clients (see section 4.5) and
generally should be used instead of cut buffers.





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Cut buffers are implemented as properties on the first root
window of the display.	The buffers can only contain text,
in the STRING encoding.  The text encoding is not changed by
Xlib when fetching or storing.	Eight buffers are provided
and can be accessed as a ring or as explicit buffers (num-
bered 0 through 7).


To store data in cut buffer 0, use XStoreBytes.
__
|
XStoreBytes(display, bytes, nbytes)
      Display *display;
      char *bytes;
      int nbytes;


display   Specifies the connection to the X server.

bytes	  Specifies the bytes, which are not necessarily
	  ASCII or null-terminated.

nbytes	  Specifies the number of bytes to be stored.
|__

The data can have embedded null characters and need not be
null-terminated.  The cut buffer's contents can be retrieved
later by any client calling XFetchBytes.

XStoreBytes can generate a BadAlloc error.


To store data in a specified cut buffer, use XStoreBuffer.
__
|
XStoreBuffer(display, bytes, nbytes, buffer)
      Display *display;
      char *bytes;
      int nbytes;
      int buffer;


display   Specifies the connection to the X server.

bytes	  Specifies the bytes, which are not necessarily
	  ASCII or null-terminated.

nbytes	  Specifies the number of bytes to be stored.

buffer	  Specifies the buffer in which you want to store
	  the bytes.
|__

If an invalid buffer is specified, the call has no effect.



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The data can have embedded null characters and need not be
null-terminated.

XStoreBuffer can generate a BadAlloc error.


To return data from cut buffer 0, use XFetchBytes.
__
|
char *XFetchBytes(display, nbytes_return)
      Display *display;
      int *nbytes_return;


display   Specifies the connection to the X server.

nbytes_return
	  Returns the number of bytes in the buffer.
|__

The XFetchBytes function returns the number of bytes in the
nbytes_return argument, if the buffer contains data.  Other-
wise, the function returns NULL and sets nbytes to 0.  The
appropriate amount of storage is allocated and the pointer
returned.  The client must free this storage when finished
with it by calling XFree.


To return data from a specified cut buffer, use XFetch-
Buffer.
__
|
char *XFetchBuffer(display, nbytes_return, buffer)
      Display *display;
      int *nbytes_return;
      int buffer;


display   Specifies the connection to the X server.

nbytes_return
	  Returns the number of bytes in the buffer.

buffer	  Specifies the buffer from which you want the
	  stored data returned.
|__

The XFetchBuffer function returns zero to the nbytes_return
argument if there is no data in the buffer or if an invalid
buffer is specified.


To rotate the cut buffers, use XRotateBuffers.




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__
|
XRotateBuffers(display, rotate)
      Display *display;
      int rotate;


display   Specifies the connection to the X server.

rotate	  Specifies how much to rotate the cut buffers.
|__

The XRotateBuffers function rotates the cut buffers, such
that buffer 0 becomes buffer n, buffer 1 becomes n + 1 mod
8, and so on.  This cut buffer numbering is global to the
display.  Note that XRotateBuffers generates BadMatch errors
if any of the eight buffers have not been created.

16.7.  Determining the Appropriate Visual Type

A single display can support multiple screens.	Each screen
can have several different visual types supported at differ-
ent depths.  You can use the functions described in this
section to determine which visual to use for your applica-
tion.

The functions in this section use the visual information
masks and the XVisualInfo structure, which is defined in
<X11/Xutil.h> and contains:





























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__
|
/* Visual information mask bits */

#define   VisualNoMask		      0x0
#define   VisualIDMask		      0x1
#define   VisualScreenMask	      0x2
#define   VisualDepthMask	      0x4
#define   VisualClassMask	      0x8
#define   VisualRedMaskMask	      0x10
#define   VisualGreenMaskMask	      0x20
#define   VisualBlueMaskMask	      0x40
#define   VisualColormapSizeMask      0x80
#define   VisualBitsPerRGBMask	      0x100
#define   VisualAllMask 	      0x1FF


/* Values */

typedef struct {
     Visual *visual;
     VisualID visualid;
     int screen;
     unsigned int depth;
     int class;
     unsigned long red_mask;
     unsigned long green_mask;
     unsigned long blue_mask;
     int colormap_size;
     int bits_per_rgb;
} XVisualInfo;

|__

To obtain a list of visual information structures that match
a specified template, use XGetVisualInfo.






















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__
|
XVisualInfo *XGetVisualInfo(display, vinfo_mask, vinfo_template, nitems_return)
      Display *display;
      long vinfo_mask;
      XVisualInfo *vinfo_template;
      int *nitems_return;


display   Specifies the connection to the X server.

vinfo_mask
	  Specifies the visual mask value.

vinfo_template
	  Specifies the visual attributes that are to be
	  used in matching the visual structures.

nitems_return
	  Returns the number of matching visual structures.
|__

The XGetVisualInfo function returns a list of visual struc-
tures that have attributes equal to the attributes specified
by vinfo_template.  If no visual structures match the tem-
plate using the specified vinfo_mask, XGetVisualInfo returns
a NULL.  To free the data returned by this function, use
XFree.


To obtain the visual information that matches the specified
depth and class of the screen, use XMatchVisualInfo.
__
|
Status XMatchVisualInfo(display, screen, depth, class, vinfo_return)
      Display *display;
      int screen;
      int depth;
      int class;
      XVisualInfo *vinfo_return;


display   Specifies the connection to the X server.

screen	  Specifies the screen.

depth	  Specifies the depth of the screen.

class	  Specifies the class of the screen.

vinfo_return
	  Returns the matched visual information.
|__

The XMatchVisualInfo function returns the visual information



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for a visual that matches the specified depth and class for
a screen.  Because multiple visuals that match the specified
depth and class can exist, the exact visual chosen is unde-
fined.	If a visual is found, XMatchVisualInfo returns
nonzero and the information on the visual to vinfo_return.
Otherwise, when a visual is not found, XMatchVisualInfo
returns zero.

16.8.  Manipulating Images

Xlib provides several functions that perform basic opera-
tions on images.  All operations on images are defined using
an XImage structure, as defined in <X11/Xlib.h>.  Because
the number of different types of image formats can be very
large, this hides details of image storage properly from
applications.

This section describes the functions for generic operations
on images.  Manufacturers can provide very fast implementa-
tions of these for the formats frequently encountered on
their hardware.  These functions are neither sufficient nor
desirable to use for general image processing.	Rather, they
are here to provide minimal functions on screen format
images.  The basic operations for getting and putting images
are XGetImage and XPutImage.

Note that no functions have been defined, as yet, to read
and write images to and from disk files.

The XImage structure describes an image as it exists in the
client's memory.  The user can request that some of the mem-
bers such as height, width, and xoffset be changed when the
image is sent to the server.  Note that bytes_per_line in
concert with offset can be used to extract a subset of the
image.	Other members (for example, byte order, bitmap_unit,
and so forth) are characteristics of both the image and the
server.  If these members differ between the image and the
server, XPutImage makes the appropriate conversions.  The
first byte of the first line of plane n must be located at
the address (data + (n * height * bytes_per_line)).  For a
description of the XImage structure, see section 8.7.


To allocate an XImage structure and initialize it with image
format values from a display, use XCreateImage.












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__
|
XImage *XCreateImage(display, visual, depth, format, offset, data, width, height, bitmap_pad,
			bytes_per_line)
      Display *display;
      Visual *visual;
      unsigned int depth;
      int format;
      int offset;
      char *data;
      unsigned int width;
      unsigned int height;
      int bitmap_pad;
      int bytes_per_line;


display   Specifies the connection to the X server.

visual	  Specifies the Visual structure.

depth	  Specifies the depth of the image.

format	  Specifies the format for the image.  You can pass
	  XYBitmap, XYPixmap, or ZPixmap.

offset	  Specifies the number of pixels to ignore at the
	  beginning of the scanline.

data	  Specifies the image data.

width	  Specifies the width of the image, in pixels.

height	  Specifies the height of the image, in pixels.

bitmap_pad
	  Specifies the quantum of a scanline (8, 16, or
	  32).	In other words, the start of one scanline is
	  separated in client memory from the start of the
	  next scanline by an integer multiple of this many
	  bits.

bytes_per_line
	  Specifies the number of bytes in the client image
	  between the start of one scanline and the start of
	  the next.
|__

The XCreateImage function allocates the memory needed for an
XImage structure for the specified display but does not
allocate space for the image itself.  Rather, it initializes
the structure byte-order, bit-order, and bitmap-unit values
from the display and returns a pointer to the XImage struc-
ture.  The red, green, and blue mask values are defined for
Z format images only and are derived from the Visual struc-
ture passed in.  Other values also are passed in.  The



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offset permits the rapid displaying of the image without
requiring each scanline to be shifted into position.  If you
pass a zero value in bytes_per_line, Xlib assumes that the
scanlines are contiguous in memory and calculates the value
of bytes_per_line itself.

Note that when the image is created using XCreateImage, XGe-
tImage, or XSubImage, the destroy procedure that the XDe-
stroyImage function calls frees both the image structure and
the data pointed to by the image structure.

The basic functions used to get a pixel, set a pixel, create
a subimage, and add a constant value to an image are defined
in the image object.  The functions in this section are
really macro invocations of the functions in the image
object and are defined in <X11/Xutil.h>.


To obtain a pixel value in an image, use XGetPixel.
__
|
unsigned long XGetPixel(ximage, x, y)
      XImage *ximage;
      int x;
      int y;


ximage	  Specifies the image.

x
y	  Specify the x and y coordinates.
|__

The XGetPixel function returns the specified pixel from the
named image.  The pixel value is returned in normalized for-
mat (that is, the least significant byte of the long is the
least significant byte of the pixel).  The image must con-
tain the x and y coordinates.


To set a pixel value in an image, use XPutPixel.
















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__
|
XPutPixel(ximage, x, y, pixel)
      XImage *ximage;
      int x;
      int y;
      unsigned long pixel;


ximage	  Specifies the image.

x
y	  Specify the x and y coordinates.

pixel	  Specifies the new pixel value.
|__

The XPutPixel function overwrites the pixel in the named
image with the specified pixel value.  The input pixel value
must be in normalized format (that is, the least significant
byte of the long is the least significant byte of the
pixel).  The image must contain the x and y coordinates.


To create a subimage, use XSubImage.
__
|
XImage *XSubImage(ximage, x, y, subimage_width, subimage_height)
      XImage *ximage;
      int x;
      int y;
      unsigned int subimage_width;
      unsigned int subimage_height;


ximage	  Specifies the image.

x
y	  Specify the x and y coordinates.

subimage_width
	  Specifies the width of the new subimage, in pix-
	  els.

subimage_height
	  Specifies the height of the new subimage, in pix-
	  els.
|__

The XSubImage function creates a new image that is a subsec-
tion of an existing one.  It allocates the memory necessary
for the new XImage structure and returns a pointer to the
new image.  The data is copied from the source image, and
the image must contain the rectangle defined by x, y, subim-
age_width, and subimage_height.



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To increment each pixel in an image by a constant value, use
XAddPixel.
__
|
XAddPixel(ximage, value)
      XImage *ximage;
      long value;


ximage	  Specifies the image.

value	  Specifies the constant value that is to be added.
|__

The XAddPixel function adds a constant value to every pixel
in an image.  It is useful when you have a base pixel value
from allocating color resources and need to manipulate the
image to that form.


To deallocate the memory allocated in a previous call to
XCreateImage, use XDestroyImage.
__
|
XDestroyImage(ximage)
	XImage *ximage;


ximage	  Specifies the image.
|__

The XDestroyImage function deallocates the memory associated
with the XImage structure.

Note that when the image is created using XCreateImage, XGe-
tImage, or XSubImage, the destroy procedure that this macro
calls frees both the image structure and the data pointed to
by the image structure.

16.9.  Manipulating Bitmaps

Xlib provides functions that you can use to read a bitmap
from a file, save a bitmap to a file, or create a bitmap.
This section describes those functions that transfer bitmaps
to and from the client's file system, thus allowing their
reuse in a later connection (for example, from an entirely
different client or to a different display or server).

The X version 11 bitmap file format is:








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__
|
#define name_width width
#define name_height height
#define name_x_hot x
#define name_y_hot y
static unsigned char name_bits[] = { 0xNN,... }

|__

The lines for the variables ending with _x_hot and _y_hot
suffixes are optional because they are present only if a
hotspot has been defined for this bitmap.  The lines for the
other variables are required.  The word ``unsigned'' is
optional; that is, the type of the _bits array can be
``char'' or ``unsigned char''.	The _bits array must be
large enough to contain the size bitmap.  The bitmap unit is
8.


To read a bitmap from a file and store it in a pixmap, use
XReadBitmapFile.
__
|
int XReadBitmapFile(display, d, filename, width_return, height_return, bitmap_return, x_hot_return,
		       y_hot_return)
      Display *display;
      Drawable d;
      char *filename;
      unsigned int *width_return, *height_return;
      Pixmap *bitmap_return;
      int *x_hot_return, *y_hot_return;


display   Specifies the connection to the X server.

d	  Specifies the drawable that indicates the screen.

filename  Specifies the file name to use.  The format of the
	  file name is operating-system dependent.

width_return
height_return
	  Return the width and height values of the read in
	  bitmap file.

bitmap_return
	  Returns the bitmap that is created.

x_hot_return
y_hot_return
	  Return the hotspot coordinates.
|__

The XReadBitmapFile function reads in a file containing a



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bitmap.  The file is parsed in the encoding of the current
locale.  The ability to read other than the standard format
is implementation-dependent.  If the file cannot be opened,
XReadBitmapFile returns BitmapOpenFailed.  If the file can
be opened but does not contain valid bitmap data, it returns
BitmapFileInvalid.  If insufficient working storage is allo-
cated, it returns BitmapNoMemory.  If the file is readable
and valid, it returns BitmapSuccess.

XReadBitmapFile returns the bitmap's height and width, as
read from the file, to width_return and height_return.	It
then creates a pixmap of the appropriate size, reads the
bitmap data from the file into the pixmap, and assigns the
pixmap to the caller's variable bitmap.  The caller must
free the bitmap using XFreePixmap when finished.  If
name_x_hot and name_y_hot exist, XReadBitmapFile returns
them to x_hot_return and y_hot_return; otherwise, it returns
-1,-1.

XReadBitmapFile can generate BadAlloc, BadDrawable, and
BadGC errors.


To read a bitmap from a file and return it as data, use
XReadBitmapFileData.
__
|
int XReadBitmapFileData(filename, width_return, height_return, data_return, x_hot_return, y_hot_return)
      char *filename;
      unsigned int *width_return, *height_return;
      unsigned char *data_return;
      int *x_hot_return, *y_hot_return;


filename  Specifies the file name to use.  The format of the
	  file name is operating-system dependent.

width_return
height_return
	  Return the width and height values of the read in
	  bitmap file.

data_return
	  Returns the bitmap data.

x_hot_return
y_hot_return
	  Return the hotspot coordinates.
|__

The XReadBitmapFileData function reads in a file containing
a bitmap, in the same manner as XReadBitmapFile, but returns
the data directly rather than creating a pixmap in the
server.  The bitmap data is returned in data_return; the



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client must free this storage when finished with it by call-
ing XFree.  The status and other return values are the same
as for XReadBitmapFile.


To write out a bitmap from a pixmap to a file, use
XWriteBitmapFile.
__
|
int XWriteBitmapFile(display, filename, bitmap, width, height, x_hot, y_hot)
      Display *display;
      char *filename;
      Pixmap bitmap;
      unsigned int width, height;
      int x_hot, y_hot;


display   Specifies the connection to the X server.

filename  Specifies the file name to use.  The format of the
	  file name is operating-system dependent.

bitmap	  Specifies the bitmap.

width
height	  Specify the width and height.

x_hot
y_hot	  Specify where to place the hotspot coordinates (or
	  -1,-1 if none are present) in the file.
|__

The XWriteBitmapFile function writes a bitmap out to a file
in the X Version 11 format.  The name used in the output
file is derived from the file name by deleting the directory
prefix.  The file is written in the encoding of the current
locale.  If the file cannot be opened for writing, it
returns BitmapOpenFailed.  If insufficient memory is allo-
cated, XWriteBitmapFile returns BitmapNoMemory; otherwise,
on no error, it returns BitmapSuccess.	If x_hot and y_hot
are not -1, -1, XWriteBitmapFile writes them out as the
hotspot coordinates for the bitmap.

XWriteBitmapFile can generate BadDrawable and BadMatch
errors.


To create a pixmap and then store bitmap-format data into
it, use XCreatePixmapFromBitmapData.








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__
|
Pixmap XCreatePixmapFromBitmapData(display, d, data, width, height, fg, bg, depth)
     Display *display;
     Drawable d;
     char *data;
     unsigned int width, height;
     unsigned long fg, bg;
     unsigned int depth;


display   Specifies the connection to the X server.

d	  Specifies the drawable that indicates the screen.

data	  Specifies the data in bitmap format.

width
height	  Specify the width and height.

fg
bg	  Specify the foreground and background pixel values
	  to use.

depth	  Specifies the depth of the pixmap.
|__

The XCreatePixmapFromBitmapData function creates a pixmap of
the given depth and then does a bitmap-format XPutImage of
the data into it.  The depth must be supported by the screen
of the specified drawable, or a BadMatch error results.

XCreatePixmapFromBitmapData can generate BadAlloc, BadDraw-
able, BadGC, and BadValue errors.


To include a bitmap written out by XWriteBitmapFile in a
program directly, as opposed to reading it in every time at
run time, use XCreateBitmapFromData.



















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__
|
Pixmap XCreateBitmapFromData(display, d, data, width, height)
      Display *display;
      Drawable d;
      char *data;
      unsigned int width, height;


display   Specifies the connection to the X server.

d	  Specifies the drawable that indicates the screen.

data	  Specifies the location of the bitmap data.

width
height	  Specify the width and height.
|__

The XCreateBitmapFromData function allows you to include in
your C program (using #include) a bitmap file that was writ-
ten out by XWriteBitmapFile (X version 11 format only) with-
out reading in the bitmap file.  The following example cre-
ates a gray bitmap:


#include "gray.bitmap"
Pixmap bitmap;
bitmap = XCreateBitmapFromData(display, window, gray_bits, gray_width, gray_height);


If insufficient working storage was allocated, XCre-
ateBitmapFromData returns None.  It is your responsibility
to free the bitmap using XFreePixmap when finished.

XCreateBitmapFromData can generate BadAlloc and BadGC
errors.

16.10.	Using the Context Manager

The context manager provides a way of associating data with
an X resource ID (mostly typically a window) in your pro-
gram.  Note that this is local to your program; the data is
not stored in the server on a property list.  Any amount of
data in any number of pieces can be associated with a
resource ID, and each piece of data has a type associated
with it.  The context manager requires knowledge of the
resource ID and type to store or retrieve data.

Essentially, the context manager can be viewed as a two-
dimensional, sparse array:  one dimension is subscripted by
the X resource ID and the other by a context type field.
Each entry in the array contains a pointer to the data.
Xlib provides context management functions with which you
can save data values, get data values, delete entries, and



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create a unique context type.  The symbols used are in
<X11/Xutil.h>.


To save a data value that corresponds to a resource ID and
context type, use XSaveContext.
__
|
int XSaveContext(display, rid, context, data)
      Display *display;
      XID rid;
      XContext context;
      XPointer data;


display   Specifies the connection to the X server.

rid	  Specifies the resource ID with which the data is
	  associated.

context   Specifies the context type to which the data
	  belongs.

data	  Specifies the data to be associated with the win-
	  dow and type.
|__

If an entry with the specified resource ID and type already
exists, XSaveContext overrides it with the specified con-
text.  The XSaveContext function returns a nonzero error
code if an error has occurred and zero otherwise.  Possible
errors are XCNOMEM (out of memory).


To get the data associated with a resource ID and type, use
XFindContext.





















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__
|
int XFindContext(display, rid, context, data_return)
      Display *display;
      XID rid;
      XContext context;
      XPointer *data_return;


display   Specifies the connection to the X server.

rid	  Specifies the resource ID with which the data is
	  associated.

context   Specifies the context type to which the data
	  belongs.

data_return
	  Returns the data.
|__

Because it is a return value, the data is a pointer.  The
XFindContext function returns a nonzero error code if an
error has occurred and zero otherwise.	Possible errors are
XCNOENT (context-not-found).


To delete an entry for a given resource ID and type, use
XDeleteContext.
__
|
int XDeleteContext(display, rid, context)
      Display *display;
      XID rid;
      XContext context;


display   Specifies the connection to the X server.

rid	  Specifies the resource ID with which the data is
	  associated.

context   Specifies the context type to which the data
	  belongs.
|__

The XDeleteContext function deletes the entry for the given
resource ID and type from the data structure.  This function
returns the same error codes that XFindContext returns if
called with the same arguments.  XDeleteContext does not
free the data whose address was saved.


To create a unique context type that may be used in subse-
quent calls to XSaveContext and XFindContext, use



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XUniqueContext.
__
|
XContext XUniqueContext()

|__



















































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			 Appendix A

	    Xlib Functions and Protocol Requests



This appendix provides two tables that relate to Xlib func-
tions and the X protocol.  The following table lists each
Xlib function (in alphabetical order) and the corresponding
protocol request that it generates.


-------------------------------------------------------
Xlib Function		     Protocol Request
-------------------------------------------------------
XActivateScreenSaver	     ForceScreenSaver
XAddHost		     ChangeHosts
XAddHosts		     ChangeHosts
XAddToSaveSet		     ChangeSaveSet
XAllocColor		     AllocColor
XAllocColorCells	     AllocColorCells
XAllocColorPlanes	     AllocColorPlanes
XAllocNamedColor	     AllocNamedColor
XAllowEvents		     AllowEvents
XAutoRepeatOff		     ChangeKeyboardControl
XAutoRepeatOn		     ChangeKeyboardControl
XBell			     Bell
XChangeActivePointerGrab     ChangeActivePointerGrab
XChangeGC		     ChangeGC
XChangeKeyboardControl	     ChangeKeyboardControl
XChangeKeyboardMapping	     ChangeKeyboardMapping
XChangePointerControl	     ChangePointerControl
XChangeProperty 	     ChangeProperty
XChangeSaveSet		     ChangeSaveSet
XChangeWindowAttributes      ChangeWindowAttributes
XCirculateSubwindows	     CirculateWindow
XCirculateSubwindowsDown     CirculateWindow
XCirculateSubwindowsUp	     CirculateWindow
XClearArea		     ClearArea
XClearWindow		     ClearArea
XConfigureWindow	     ConfigureWindow
XConvertSelection	     ConvertSelection
XCopyArea		     CopyArea
XCopyColormapAndFree	     CopyColormapAndFree
XCopyGC 		     CopyGC
XCopyPlane		     CopyPlane
XCreateBitmapFromData	     CreateGC
			     CreatePixmap
			     FreeGC
			     PutImage
XCreateColormap 	     CreateColormap




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-------------------------------------------------------
Xlib Function		     Protocol Request
-------------------------------------------------------
XCreateFontCursor	     CreateGlyphCursor
XCreateGC		     CreateGC
XCreateGlyphCursor	     CreateGlyphCursor
XCreatePixmap		     CreatePixmap
XCreatePixmapCursor	     CreateCursor
XCreatePixmapFromData	     CreateGC
			     CreatePixmap
			     FreeGC
			     PutImage
XCreateSimpleWindow	     CreateWindow
XCreateWindow		     CreateWindow
XDefineCursor		     ChangeWindowAttributes
XDeleteProperty 	     DeleteProperty
XDestroySubwindows	     DestroySubwindows
XDestroyWindow		     DestroyWindow
XDisableAccessControl	     SetAccessControl
XDrawArc		     PolyArc
XDrawArcs		     PolyArc
XDrawImageString	     ImageText8
XDrawImageString16	     ImageText16
XDrawLine		     PolySegment
XDrawLines		     PolyLine
XDrawPoint		     PolyPoint
XDrawPoints		     PolyPoint
XDrawRectangle		     PolyRectangle
XDrawRectangles 	     PolyRectangle
XDrawSegments		     PolySegment
XDrawString		     PolyText8
XDrawString16		     PolyText16
XDrawText		     PolyText8
XDrawText16		     PolyText16
XEnableAccessControl	     SetAccessControl
XFetchBytes		     GetProperty
XFetchName		     GetProperty
XFillArc		     PolyFillArc
XFillArcs		     PolyFillArc
XFillPolygon		     FillPoly
XFillRectangle		     PolyFillRectangle
XFillRectangles 	     PolyFillRectangle
XForceScreenSaver	     ForceScreenSaver
XFreeColormap		     FreeColormap
XFreeColors		     FreeColors
XFreeCursor		     FreeCursor
XFreeFont		     CloseFont
XFreeGC 		     FreeGC
XFreePixmap		     FreePixmap
XGetAtomName		     GetAtomName
XGetClassHint		     GetProperty
XGetFontPath		     GetFontPath
XGetGeometry		     GetGeometry




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-------------------------------------------------------
Xlib Function		     Protocol Request
-------------------------------------------------------
XGetIconName		     GetProperty
XGetIconSizes		     GetProperty
XGetImage		     GetImage
XGetInputFocus		     GetInputFocus
XGetKeyboardControl	     GetKeyboardControl
XGetKeyboardMapping	     GetKeyboardMapping
XGetModifierMapping	     GetModifierMapping
XGetMotionEvents	     GetMotionEvents
XGetNormalHints 	     GetProperty
XGetPointerControl	     GetPointerControl
XGetPointerMapping	     GetPointerMapping
XGetRGBColormaps	     GetProperty
XGetScreenSaver 	     GetScreenSaver
XGetSelectionOwner	     GetSelectionOwner
XGetSizeHints		     GetProperty
XGetTextProperty	     GetProperty
XGetTransientForHint	     GetProperty
XGetWMClientMachine	     GetProperty
XGetWMColormapWindows	     GetProperty
			     InternAtom
XGetWMHints		     GetProperty
XGetWMIconName		     GetProperty
XGetWMName		     GetProperty
XGetWMNormalHints	     GetProperty
XGetWMProtocols 	     GetProperty
			     InternAtom
XGetWMSizeHints 	     GetProperty
XGetWindowAttributes	     GetWindowAttributes
			     GetGeometry
XGetWindowProperty	     GetProperty
XGetZoomHints		     GetProperty
XGrabButton		     GrabButton
XGrabKey		     GrabKey
XGrabKeyboard		     GrabKeyboard
XGrabPointer		     GrabPointer
XGrabServer		     GrabServer
XIconifyWindow		     InternAtom
			     SendEvent
XInitExtension		     QueryExtension
XInstallColormap	     InstallColormap
XInternAtom		     InternAtom
XKillClient		     KillClient
XListExtensions 	     ListExtensions
XListFonts		     ListFonts
XListFontsWithInfo	     ListFontsWithInfo
XListHosts		     ListHosts
XListInstalledColormaps      ListInstalledColormaps
XListProperties 	     ListProperties
XLoadFont		     OpenFont
XLoadQueryFont		     OpenFont




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-------------------------------------------------------
Xlib Function		     Protocol Request
-------------------------------------------------------
			     QueryFont
XLookupColor		     LookupColor
XLowerWindow		     ConfigureWindow
XMapRaised		     ConfigureWindow
			     MapWindow
XMapSubwindows		     MapSubwindows
XMapWindow		     MapWindow
XMoveResizeWindow	     ConfigureWindow
XMoveWindow		     ConfigureWindow
XNoOp			     NoOperation
XOpenDisplay		     CreateGC
XParseColor		     LookupColor
XPutImage		     PutImage
XQueryBestCursor	     QueryBestSize
XQueryBestSize		     QueryBestSize
XQueryBestStipple	     QueryBestSize
XQueryBestTile		     QueryBestSize
XQueryColor		     QueryColors
XQueryColors		     QueryColors
XQueryExtension 	     QueryExtension
XQueryFont		     QueryFont
XQueryKeymap		     QueryKeymap
XQueryPointer		     QueryPointer
XQueryTextExtents	     QueryTextExtents
XQueryTextExtents16	     QueryTextExtents
XQueryTree		     QueryTree
XRaiseWindow		     ConfigureWindow
XReadBitmapFile 	     CreateGC
			     CreatePixmap
			     FreeGC
			     PutImage
XRecolorCursor		     RecolorCursor
XReconfigureWMWindow	     ConfigureWindow
			     SendEvent
XRemoveFromSaveSet	     ChangeSaveSet
XRemoveHost		     ChangeHosts
XRemoveHosts		     ChangeHosts
XReparentWindow 	     ReparentWindow
XResetScreenSaver	     ForceScreenSaver
XResizeWindow		     ConfigureWindow
XRestackWindows 	     ConfigureWindow
XRotateBuffers		     RotateProperties
XRotateWindowProperties      RotateProperties
XSelectInput		     ChangeWindowAttributes
XSendEvent		     SendEvent
XSetAccessControl	     SetAccessControl
XSetArcMode		     ChangeGC
XSetBackground		     ChangeGC
XSetClassHint		     ChangeProperty
XSetClipMask		     ChangeGC




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-------------------------------------------------------
Xlib Function		     Protocol Request
-------------------------------------------------------
XSetClipOrigin		     ChangeGC
XSetClipRectangles	     SetClipRectangles
XSetCloseDownMode	     SetCloseDownMode
XSetCommand		     ChangeProperty
XSetDashes		     SetDashes
XSetFillRule		     ChangeGC
XSetFillStyle		     ChangeGC
XSetFont		     ChangeGC
XSetFontPath		     SetFontPath
XSetForeground		     ChangeGC
XSetFunction		     ChangeGC
XSetGraphicsExposures	     ChangeGC
XSetIconName		     ChangeProperty
XSetIconSizes		     ChangeProperty
XSetInputFocus		     SetInputFocus
XSetLineAttributes	     ChangeGC
XSetModifierMapping	     SetModifierMapping
XSetNormalHints 	     ChangeProperty
XSetPlaneMask		     ChangeGC
XSetPointerMapping	     SetPointerMapping
XSetRGBColormaps	     ChangeProperty
XSetScreenSaver 	     SetScreenSaver
XSetSelectionOwner	     SetSelectionOwner
XSetSizeHints		     ChangeProperty
XSetStandardProperties	     ChangeProperty
XSetState		     ChangeGC
XSetStipple		     ChangeGC
XSetSubwindowMode	     ChangeGC
XSetTextProperty	     ChangeProperty
XSetTile		     ChangeGC
XSetTransientForHint	     ChangeProperty
XSetTSOrigin		     ChangeGC
XSetWMClientMachine	     ChangeProperty
XSetWMColormapWindows	     ChangeProperty
			     InternAtom
XSetWMHints		     ChangeProperty
XSetWMIconName		     ChangeProperty
XSetWMName		     ChangeProperty
XSetWMNormalHints	     ChangeProperty
XSetWMProperties	     ChangeProperty
XSetWMProtocols 	     ChangeProperty
			     InternAtom
XSetWMSizeHints 	     ChangeProperty
XSetWindowBackground	     ChangeWindowAttributes
XSetWindowBackgroundPixmap   ChangeWindowAttributes
XSetWindowBorder	     ChangeWindowAttributes
XSetWindowBorderPixmap	     ChangeWindowAttributes
XSetWindowBorderWidth	     ConfigureWindow
XSetWindowColormap	     ChangeWindowAttributes
XSetZoomHints		     ChangeProperty




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-------------------------------------------------------
Xlib Function		     Protocol Request
-------------------------------------------------------
XStoreBuffer		     ChangeProperty
XStoreBytes		     ChangeProperty
XStoreColor		     StoreColors
XStoreColors		     StoreColors
XStoreName		     ChangeProperty
XStoreNamedColor	     StoreNamedColor
XSync			     GetInputFocus
XSynchronize		     GetInputFocus
XTranslateCoordinates	     TranslateCoordinates
XUndefineCursor 	     ChangeWindowAttributes
XUngrabButton		     UngrabButton
XUngrabKey		     UngrabKey
XUngrabKeyboard 	     UngrabKeyboard
XUngrabPointer		     UngrabPointer
XUngrabServer		     UngrabServer
XUninstallColormap	     UninstallColormap
XUnloadFont		     CloseFont
XUnmapSubwindows	     UnmapSubwindows
XUnmapWindow		     UnmapWindow
XWarpPointer		     WarpPointer
XWithdrawWindow 	     SendEvent
			     UnmapWindow
































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The following table lists each X protocol request (in alpha-
betical order) and the Xlib functions that reference it.

-------------------------------------------------------
Protocol Request	    Xlib Function
-------------------------------------------------------
AllocColor		    XAllocColor
AllocColorCells 	    XAllocColorCells
AllocColorPlanes	    XAllocColorPlanes
AllocNamedColor 	    XAllocNamedColor
AllowEvents		    XAllowEvents
Bell			    XBell
ChangeActivePointerGrab     XChangeActivePointerGrab
ChangeGC		    XChangeGC
			    XSetArcMode
			    XSetBackground
			    XSetClipMask
			    XSetClipOrigin
			    XSetFillRule
			    XSetFillStyle
			    XSetFont
			    XSetForeground
			    XSetFunction
			    XSetGraphicsExposures
			    XSetLineAttributes
			    XSetPlaneMask
			    XSetState
			    XSetStipple
			    XSetSubwindowMode
			    XSetTile
			    XSetTSOrigin
ChangeHosts		    XAddHost
			    XAddHosts
			    XRemoveHost
			    XRemoveHosts
ChangeKeyboardControl	    XAutoRepeatOff
			    XAutoRepeatOn
			    XChangeKeyboardControl
ChangeKeyboardMapping	    XChangeKeyboardMapping
ChangePointerControl	    XChangePointerControl
ChangeProperty		    XChangeProperty
			    XSetClassHint
			    XSetCommand
			    XSetIconName
			    XSetIconSizes
			    XSetNormalHints
			    XSetRGBColormaps
			    XSetSizeHints
			    XSetStandardProperties
			    XSetTextProperty
			    XSetTransientForHint
			    XSetWMClientMachine
			    XSetWMColormapWindows




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-------------------------------------------------------
Protocol Request	    Xlib Function
-------------------------------------------------------
			    XSetWMHints
			    XSetWMIconName
			    XSetWMName
			    XSetWMNormalHints
			    XSetWMProperties
			    XSetWMProtocols
			    XSetWMSizeHints
			    XSetZoomHints
			    XStoreBuffer
			    XStoreBytes
			    XStoreName
ChangeSaveSet		    XAddToSaveSet
			    XChangeSaveSet
			    XRemoveFromSaveSet
ChangeWindowAttributes	    XChangeWindowAttributes
			    XDefineCursor
			    XSelectInput
			    XSetWindowBackground
			    XSetWindowBackgroundPixmap
			    XSetWindowBorder
			    XSetWindowBorderPixmap
			    XSetWindowColormap
			    XUndefineCursor
CirculateWindow 	    XCirculateSubwindowsDown
			    XCirculateSubwindowsUp
			    XCirculateSubwindows
ClearArea		    XClearArea
			    XClearWindow
CloseFont		    XFreeFont
			    XUnloadFont
ConfigureWindow 	    XConfigureWindow
			    XLowerWindow
			    XMapRaised
			    XMoveResizeWindow
			    XMoveWindow
			    XRaiseWindow
			    XReconfigureWMWindow
			    XResizeWindow
			    XRestackWindows
			    XSetWindowBorderWidth
ConvertSelection	    XConvertSelection
CopyArea		    XCopyArea
CopyColormapAndFree	    XCopyColormapAndFree
CopyGC			    XCopyGC
CopyPlane		    XCopyPlane
CreateColormap		    XCreateColormap
CreateCursor		    XCreatePixmapCursor
CreateGC		    XCreateGC
			    XCreateBitmapFromData
			    XCreatePixmapFromData




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-------------------------------------------------------
Protocol Request	    Xlib Function
-------------------------------------------------------
			    XOpenDisplay
			    XReadBitmapFile
CreateGlyphCursor	    XCreateFontCursor
			    XCreateGlyphCursor
CreatePixmap		    XCreatePixmap
			    XCreateBitmapFromData
			    XCreatePixmapFromData
			    XReadBitmapFile
CreateWindow		    XCreateSimpleWindow
			    XCreateWindow
DeleteProperty		    XDeleteProperty
DestroySubwindows	    XDestroySubwindows
DestroyWindow		    XDestroyWindow
FillPoly		    XFillPolygon
ForceScreenSaver	    XActivateScreenSaver
			    XForceScreenSaver
			    XResetScreenSaver
FreeColormap		    XFreeColormap
FreeColors		    XFreeColors
FreeCursor		    XFreeCursor
FreeGC			    XFreeGC
			    XCreateBitmapFromData
			    XCreatePixmapFromData
			    XReadBitmapFile
FreePixmap		    XFreePixmap
GetAtomName		    XGetAtomName
GetFontPath		    XGetFontPath
GetGeometry		    XGetGeometry
			    XGetWindowAttributes
GetImage		    XGetImage
GetInputFocus		    XGetInputFocus
			    XSync
			    XSynchronize
GetKeyboardControl	    XGetKeyboardControl
GetKeyboardMapping	    XGetKeyboardMapping
GetModifierMapping	    XGetModifierMapping
GetMotionEvents 	    XGetMotionEvents
GetPointerControl	    XGetPointerControl
GetPointerMapping	    XGetPointerMapping
GetProperty		    XFetchBytes
			    XFetchName
			    XGetClassHint
			    XGetIconName
			    XGetIconSizes
			    XGetNormalHints
			    XGetRGBColormaps
			    XGetSizeHints
			    XGetTextProperty
			    XGetTransientForHint
			    XGetWMClientMachine




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-------------------------------------------------------
Protocol Request	    Xlib Function
-------------------------------------------------------
			    XGetWMColormapWindows
			    XGetWMHints
			    XGetWMIconName
			    XGetWMName
			    XGetWMNormalHints
			    XGetWMProtocols
			    XGetWMSizeHints
			    XGetWindowProperty
			    XGetZoomHints
GetSelectionOwner	    XGetSelectionOwner
GetWindowAttributes	    XGetWindowAttributes
GrabButton		    XGrabButton
GrabKey 		    XGrabKey
GrabKeyboard		    XGrabKeyboard
GrabPointer		    XGrabPointer
GrabServer		    XGrabServer
ImageText8		    XDrawImageString
ImageText16		    XDrawImageString16
InstallColormap 	    XInstallColormap
InternAtom		    XGetWMColormapWindows
			    XGetWMProtocols
			    XIconifyWindow
			    XInternAtom
			    XSetWMColormapWindows
			    XSetWMProtocols
KillClient		    XKillClient
ListExtensions		    XListExtensions
ListFonts		    XListFonts
ListFontsWithInfo	    XListFontsWithInfo
ListHosts		    XListHosts
ListInstalledColormaps	    XListInstalledColormaps
ListProperties		    XListProperties
LookupColor		    XLookupColor
			    XParseColor
MapSubwindows		    XMapSubwindows
MapWindow		    XMapRaised
			    XMapWindow
NoOperation		    XNoOp
OpenFont		    XLoadFont
			    XLoadQueryFont
PolyArc 		    XDrawArc
			    XDrawArcs
PolyFillArc		    XFillArc
			    XFillArcs
PolyFillRectangle	    XFillRectangle
			    XFillRectangles
PolyLine		    XDrawLines
PolyPoint		    XDrawPoint
			    XDrawPoints
PolyRectangle		    XDrawRectangle




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-------------------------------------------------------
Protocol Request	    Xlib Function
-------------------------------------------------------
			    XDrawRectangles
PolySegment		    XDrawLine
			    XDrawSegments
PolyText8		    XDrawString
			    XDrawText
PolyText16		    XDrawString16
			    XDrawText16
PutImage		    XPutImage
			    XCreateBitmapFromData
			    XCreatePixmapFromData
			    XReadBitmapFile
QueryBestSize		    XQueryBestCursor
			    XQueryBestSize
			    XQueryBestStipple
			    XQueryBestTile
QueryColors		    XQueryColor
			    XQueryColors
QueryExtension		    XInitExtension
			    XQueryExtension
QueryFont		    XLoadQueryFont
			    XQueryFont
QueryKeymap		    XQueryKeymap
QueryPointer		    XQueryPointer
QueryTextExtents	    XQueryTextExtents
			    XQueryTextExtents16
QueryTree		    XQueryTree
RecolorCursor		    XRecolorCursor
ReparentWindow		    XReparentWindow
RotateProperties	    XRotateBuffers
			    XRotateWindowProperties
SendEvent		    XIconifyWindow
			    XReconfigureWMWindow
			    XSendEvent
			    XWithdrawWindow
SetAccessControl	    XDisableAccessControl
			    XEnableAccessControl
			    XSetAccessControl
SetClipRectangles	    XSetClipRectangles
SetCloseDownMode	    XSetCloseDownMode
SetDashes		    XSetDashes
SetFontPath		    XSetFontPath
SetInputFocus		    XSetInputFocus
SetModifierMapping	    XSetModifierMapping
SetPointerMapping	    XSetPointerMapping
SetScreenSaver		    XGetScreenSaver
			    XSetScreenSaver
SetSelectionOwner	    XSetSelectionOwner
StoreColors		    XStoreColor
			    XStoreColors
StoreNamedColor 	    XStoreNamedColor




			     616





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-------------------------------------------------------
Protocol Request	    Xlib Function
-------------------------------------------------------
TranslateCoordinates	    XTranslateCoordinates
UngrabButton		    XUngrabButton
UngrabKey		    XUngrabKey
UngrabKeyboard		    XUngrabKeyboard
UngrabPointer		    XUngrabPointer
UngrabServer		    XUngrabServer
UninstallColormap	    XUninstallColormap
UnmapSubwindows 	    XUnmapSubWindows
UnmapWindow		    XUnmapWindow
			    XWithdrawWindow
WarpPointer		    XWarpPointer











































			     617





Xlib - C Library			    X11, Release 6.4




			 Appendix B

		       X Font Cursors



The following are the available cursors that can be used
with XCreateFontCursor.


#define XC_X_cursor 0	      #define XC_ll_angle 76
#define XC_arrow 2	      #define XC_lr_angle 78
#define XC_based_arrow_down 4 #define XC_man 80
#define XC_based_arrow_up 6   #define XC_middlebutton 82
#define XC_boat 8	      #define XC_mouse 84
#define XC_bogosity 10	      #define XC_pencil 86
#define XC_bottom_left_corner 12#define XC_pirate 88
#define XC_bottom_right_corner 14#define XC_plus 90
#define XC_bottom_side 16     #define XC_question_arrow 92
#define XC_bottom_tee 18      #define XC_right_ptr 94
#define XC_box_spiral 20      #define XC_right_side 96
#define XC_center_ptr 22      #define XC_right_tee 98
#define XC_circle 24	      #define XC_rightbutton 100
#define XC_clock 26	      #define XC_rtl_logo 102
#define XC_coffee_mug 28      #define XC_sailboat 104
#define XC_cross 30	      #define XC_sb_down_arrow 106
#define XC_cross_reverse 32   #define XC_sb_h_double_arrow 108
#define XC_crosshair 34       #define XC_sb_left_arrow 110
#define XC_diamond_cross 36   #define XC_sb_right_arrow 112
#define XC_dot 38	      #define XC_sb_up_arrow 114
#define XC_dot_box_mask 40    #define XC_sb_v_double_arrow 116
#define XC_double_arrow 42    #define XC_shuttle 118
#define XC_draft_large 44     #define XC_sizing 120
#define XC_draft_small 46     #define XC_spider 122
#define XC_draped_box 48      #define XC_spraycan 124
#define XC_exchange 50	      #define XC_star 126
#define XC_fleur 52	      #define XC_target 128
#define XC_gobbler 54	      #define XC_tcross 130
#define XC_gumby 56	      #define XC_top_left_arrow 132
#define XC_hand1 58	      #define XC_top_left_corner 134
#define XC_hand2 60	      #define XC_top_right_corner 136
#define XC_heart 62	      #define XC_top_side 138
#define XC_icon 64	      #define XC_top_tee 140
#define XC_iron_cross 66      #define XC_trek 142
#define XC_left_ptr 68	      #define XC_ul_angle 144
#define XC_left_side 70       #define XC_umbrella 146
#define XC_left_tee 72	      #define XC_ur_angle 148
#define XC_leftbutton 74      #define XC_watch 150
			      #define XC_xterm 152






			     618





Xlib - C Library			    X11, Release 6.4




			 Appendix C

			 Extensions



Because X can evolve by extensions to the core protocol, it
is important that extensions not be perceived as second-
class citizens.  At some point, your favorite extensions may
be adopted as additional parts of the X Standard.

Therefore, there should be little to distinguish the use of
an extension from that of the core protocol.  To avoid hav-
ing to initialize extensions explicitly in application pro-
grams, it is also important that extensions perform lazy
evaluations, automatically initializing themselves when
called for the first time.

This appendix describes techniques for writing extensions to
Xlib that will run at essentially the same performance as
the core protocol requests.

			    Note

     It is expected that a given extension to X con-
     sists of multiple requests.  Defining 10 new fea-
     tures as 10 separate extensions is a bad practice.
     Rather, they should be packaged into a single
     extension and should use minor opcodes to distin-
     guish the requests.


The symbols and macros used for writing stubs to Xlib are
listed in <X11/Xlibint.h>.

Basic Protocol Support Routines

The basic protocol requests for extensions are XQueryExten-
sion and XListExtensions.
















			     619





Xlib - C Library			    X11, Release 6.4

__
|
Bool XQueryExtension(display, name, major_opcode_return, first_event_return, first_error_return)
      Display *display;
      char *name;
      int *major_opcode_return;
      int *first_event_return;
      int *first_error_return;


display   Specifies the connection to the X server.

name	  Specifies the extension name.

major_opcode_return
	  Returns the major opcode.

first_event_return
	  Returns the first event code, if any.

first_error_return
	  Returns the first error code, if any.
|__

The XQueryExtension function determines if the named exten-
sion is present.  If the extension is not present, XQueryEx-
tension returns False; otherwise, it returns True.  If the
extension is present, XQueryExtension returns the major
opcode for the extension to major_opcode_return; otherwise,
it returns zero.  Any minor opcode and the request formats
are specific to the extension.	If the extension involves
additional event types, XQueryExtension returns the base
event type code to first_event_return; otherwise, it returns
zero.  The format of the events is specific to the exten-
sion.  If the extension involves additional error codes,
XQueryExtension returns the base error code to
first_error_return; otherwise, it returns zero.  The format
of additional data in the errors is specific to the exten-
sion.

If the extension name is not in the Host Portable Character
Encoding the result is implementation-dependent.  Uppercase
and lowercase matter; the strings ``thing'', ``Thing'', and
``thinG'' are all considered different names.














			     620





Xlib - C Library			    X11, Release 6.4

__
|
char **XListExtensions(display, nextensions_return)
      Display *display;
      int *nextensions_return;


display   Specifies the connection to the X server.

nextensions_return
	  Returns the number of extensions listed.
|__

The XListExtensions function returns a list of all exten-
sions supported by the server.	If the data returned by the
server is in the Latin Portable Character Encoding, then the
returned strings are in the Host Portable Character Encod-
ing.  Otherwise, the result is implementation-dependent.
__
|
XFreeExtensionList(list)
      char **list;


list	  Specifies the list of extension names.
|__

The XFreeExtensionList function frees the memory allocated
by XListExtensions.

Hooking into Xlib

These functions allow you to hook into the library.  They
are not normally used by application programmers but are
used by people who need to extend the core X protocol and
the X library interface.  The functions, which generate pro-
tocol requests for X, are typically called stubs.

In extensions, stubs first should check to see if they have
initialized themselves on a connection.  If they have not,
they then should call XInitExtension to attempt to initial-
ize themselves on the connection.

If the extension needs to be informed of GC/font allocation
or deallocation or if the extension defines new event types,
the functions described here allow the extension to be
called when these events occur.

The XExtCodes structure returns the information from XIni-
tExtension and is defined in <X11/Xlib.h>:








			     621





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__
|
typedef struct _XExtCodes {   /* public to extension, cannot be changed */
     int extension;	      /* extension number */
     int major_opcode;	      /* major op-code assigned by server */
     int first_event;	      /* first event number for the extension */
     int first_error;	      /* first error number for the extension */
} XExtCodes;

|__

__
|
XExtCodes *XInitExtension(display, name)
      Display *display;
      char *name;


display   Specifies the connection to the X server.

name	  Specifies the extension name.
|__

The XInitExtension function determines if the named exten-
sion exists.  Then, it allocates storage for maintaining the
information about the extension on the connection, chains
this onto the extension list for the connection, and returns
the information the stub implementor will need to access the
extension.  If the extension does not exist, XInitExtension
returns NULL.

If the extension name is not in the Host Portable Character
Encoding, the result is implementation-dependent.  Uppercase
and lowercase matter; the strings ``thing'', ``Thing'', and
``thinG'' are all considered different names.

The extension number in the XExtCodes structure is needed in
the other calls that follow.  This extension number is
unique only to a single connection.

__
|
XExtCodes *XAddExtension(display)
	Display *display;


display   Specifies the connection to the X server.
|__

For local Xlib extensions, the XAddExtension function allo-
cates the XExtCodes structure, bumps the extension number
count, and chains the extension onto the extension list.
(This permits extensions to Xlib without requiring server
extensions.)




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Hooks into the Library

These functions allow you to define procedures that are to
be called when various circumstances occur.  The procedures
include the creation of a new GC for a connection, the copy-
ing of a GC, the freeing of a GC, the creating and freeing
of fonts, the conversion of events defined by extensions to
and from wire format, and the handling of errors.

All of these functions return the previous procedure defined
for this extension.
__
|
int (*XESetCloseDisplay(display, extension, proc))()
      Display *display;
      int extension;
      int (*proc)();


display   Specifies the connection to the X server.

extension Specifies the extension number.

proc	  Specifies the procedure to call when the display
	  is closed.
|__

The XESetCloseDisplay function defines a procedure to be
called whenever XCloseDisplay is called.  It returns any
previously defined procedure, usually NULL.

When XCloseDisplay is called, your procedure is called with
these arguments:

__
|
(*proc)(display, codes)
     Display *display;
     XExtCodes *codes;

|__
















			     623





Xlib - C Library			    X11, Release 6.4

__
|
int (*XESetCreateGC(display, extension, proc))()
      Display *display;
      int extension;
      int (*proc)();


display   Specifies the connection to the X server.

extension Specifies the extension number.

proc	  Specifies the procedure to call when a GC is
	  closed.
|__

The XESetCreateGC function defines a procedure to be called
whenever a new GC is created.  It returns any previously
defined procedure, usually NULL.

When a GC is created, your procedure is called with these
arguments:

__
|
(*proc)(display, gc, codes)
     Display *display;
     GC gc;
     XExtCodes *codes;

|__

__
|
int (*XESetCopyGC(display, extension, proc))()
      Display *display;
      int extension;
      int (*proc)();


display   Specifies the connection to the X server.

extension Specifies the extension number.

proc	  Specifies the procedure to call when GC components
	  are copied.
|__

The XESetCopyGC function defines a procedure to be called
whenever a GC is copied.  It returns any previously defined
procedure, usually NULL.

When a GC is copied, your procedure is called with these
arguments:




			     624





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__
|
(*proc)(display, gc, codes)
     Display *display;
     GC gc;
     XExtCodes *codes;

|__

__
|
int (*XESetFreeGC(display, extension, proc))()
      Display *display;
      int extension;
      int (*proc)();


display   Specifies the connection to the X server.

extension Specifies the extension number.

proc	  Specifies the procedure to call when a GC is
	  freed.
|__

The XESetFreeGC function defines a procedure to be called
whenever a GC is freed.  It returns any previously defined
procedure, usually NULL.

When a GC is freed, your procedure is called with these
arguments:

__
|
(*proc)(display, gc, codes)
     Display *display;
     GC gc;
     XExtCodes *codes;

|__


















			     625





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__
|
int (*XESetCreateFont(display, extension, proc))()
      Display *display;
      int extension;
      int (*proc)();


display   Specifies the connection to the X server.

extension Specifies the extension number.

proc	  Specifies the procedure to call when a font is
	  created.
|__

The XESetCreateFont function defines a procedure to be
called whenever XLoadQueryFont and XQueryFont are called.
It returns any previously defined procedure, usually NULL.

When XLoadQueryFont or XQueryFont is called, your procedure
is called with these arguments:

__
|
(*proc)(display, fs, codes)
     Display *display;
     XFontStruct *fs;
     XExtCodes *codes;

|__

__
|
int (*XESetFreeFont(display, extension, proc))()
      Display *display;
      int extension;
      int (*proc)();


display   Specifies the connection to the X server.

extension Specifies the extension number.

proc	  Specifies the procedure to call when a font is
	  freed.
|__

The XESetFreeFont function defines a procedure to be called
whenever XFreeFont is called.  It returns any previously
defined procedure, usually NULL.

When XFreeFont is called, your procedure is called with
these arguments:




			     626





Xlib - C Library			    X11, Release 6.4

__
|
(*proc)(display, fs, codes)
     Display *display;
     XFontStruct *fs;
     XExtCodes *codes;

|__

The XESetWireToEvent and XESetEventToWire functions allow
you to define new events to the library.  An XEvent struc-
ture always has a type code (type int) as the first compo-
nent.  This uniquely identifies what kind of event it is.
The second component is always the serial number (type
unsigned long) of the last request processed by the server.
The third component is always a Boolean (type Bool) indicat-
ing whether the event came from a SendEvent protocol
request.  The fourth component is always a pointer to the
display the event was read from.  The fifth component is
always a resource ID of one kind or another, usually a win-
dow, carefully selected to be useful to toolkit dispatchers.
The fifth component should always exist, even if the event
does not have a natural destination; if there is no value
from the protocol to put in this component, initialize it to
zero.

			    Note

     There is an implementation limit such that your
     host event structure size cannot be bigger than
     the size of the XEvent union of structures.  There
     also is no way to guarantee that more than 24 ele-
     ments or 96 characters in the structure will be
     fully portable between machines.

__
|
int (*XESetWireToEvent(display, event_number, proc))()
      Display *display;
      int event_number;
      Status (*proc)();


display   Specifies the connection to the X server.

event_number
	  Specifies the event code.

proc	  Specifies the procedure to call when converting an
	  event.
|__

The XESetWireToEvent function defines a procedure to be
called when an event needs to be converted from wire format
(xEvent) to host format (XEvent).  The event number defines



			     627





Xlib - C Library			    X11, Release 6.4


which protocol event number to install a conversion proce-
dure for.  XESetWireToEvent returns any previously defined
procedure.

			    Note

     You can replace a core event conversion function
     with one of your own, although this is not encour-
     aged.  It would, however, allow you to intercept a
     core event and modify it before being placed in
     the queue or otherwise examined.

When Xlib needs to convert an event from wire format to host
format, your procedure is called with these arguments:

__
|
Status (*proc)(display, re, event)
     Display *display;
     XEvent *re;
     xEvent *event;

|__

Your procedure must return status to indicate if the conver-
sion succeeded.  The re argument is a pointer to where the
host format event should be stored, and the event argument
is the 32-byte wire event structure.  In the XEvent struc-
ture you are creating, you must fill in the five required
members of the event structure.  You should fill in the type
member with the type specified for the xEvent structure.
You should copy all other members from the xEvent structure
(wire format) to the XEvent structure (host format).  Your
conversion procedure should return True if the event should
be placed in the queue or False if it should not be placed
in the queue.

To initialize the serial number component of the event, call
_XSetLastRequestRead with the event and use the return
value.

__
|
unsigned long _XSetLastRequestRead(display, rep)
      Display *display;
      xGenericReply *rep;


display   Specifies the connection to the X server.

rep	  Specifies the wire event structure.
|__

The _XSetLastRequestRead function computes and returns a



			     628





Xlib - C Library			    X11, Release 6.4


complete serial number from the partial serial number in the
event.


__
|
Status (*XESetEventToWire(display, event_number, proc))()
      Display *display;
      int event_number;
      int (*proc)();


display   Specifies the connection to the X server.

event_number
	  Specifies the event code.

proc	  Specifies the procedure to call when converting an
	  event.
|__

The XESetEventToWire function defines a procedure to be
called when an event needs to be converted from host format
(XEvent) to wire format (xEvent) form.	The event number
defines which protocol event number to install a conversion
procedure for.	XESetEventToWire returns any previously
defined procedure.  It returns zero if the conversion fails
or nonzero otherwise.

			    Note

     You can replace a core event conversion function
     with one of your own, although this is not encour-
     aged.  It would, however, allow you to intercept a
     core event and modify it before being sent to
     another client.

When Xlib needs to convert an event from host format to wire
format, your procedure is called with these arguments:

__
|
(*proc)(display, re, event)
     Display *display;
     XEvent *re;
     xEvent *event;

|__

The re argument is a pointer to the host format event, and
the event argument is a pointer to where the 32-byte wire
event structure should be stored.  You should fill in the
type with the type from the XEvent structure.  All other
members then should be copied from the host format to the



			     629





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xEvent structure.
__
|
Bool (*XESetWireToError(display, error_number, proc)()
      Display *display;
      int error_number;
      Bool (*proc)();


display   Specifies the connection to the X server.

error_number
	  Specifies the error code.

proc	  Specifies the procedure to call when an error is
	  received.
|__

The XESetWireToError function defines a procedure to be
called when an extension error needs to be converted from
wire format to host format.  The error number defines which
protocol error code to install the conversion procedure for.
XESetWireToError returns any previously defined procedure.

Use this function for extension errors that contain addi-
tional error values beyond those in a core X error, when
multiple wire errors must be combined into a single Xlib
error, or when it is necessary to intercept an X error
before it is otherwise examined.

When Xlib needs to convert an error from wire format to host
format, the procedure is called with these arguments:

__
|
Bool (*proc)(display, he, we)
     Display *display;
     XErrorEvent *he;
     xError *we;

|__

The he argument is a pointer to where the host format error
should be stored.  The structure pointed at by he is guaran-
teed to be as large as an XEvent structure and so can be
cast to a type larger than an XErrorEvent to store addi-
tional values.	If the error is to be completely ignored by
Xlib (for example, several protocol error structures will be
combined into one Xlib error), then the function should
return False; otherwise, it should return True.







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__
|
int (*XESetError(display, extension, proc))()
      Display *display;
      int extension;
      int (*proc)();


display   Specifies the connection to the X server.

extension Specifies the extension number.

proc	  Specifies the procedure to call when an error is
	  received.
|__

Inside Xlib, there are times that you may want to suppress
the calling of the external error handling when an error
occurs.  This allows status to be returned on a call at the
cost of the call being synchronous (though most such func-
tions are query operations, in any case, and are typically
programmed to be synchronous).

When Xlib detects a protocol error in _XReply, it calls your
procedure with these arguments:

__
|
int (*proc)(display, err, codes, ret_code)
     Display *display;
     xError *err;
     XExtCodes *codes;
     int *ret_code;

|__

The err argument is a pointer to the 32-byte wire format
error.	The codes argument is a pointer to the extension
codes structure.  The ret_code argument is the return code
you may want _XReply returned to.

If your procedure returns a zero value, the error is not
suppressed, and the client's error handler is called.  (For
further information, see section 11.8.2.)  If your procedure
returns nonzero, the error is suppressed, and _XReply
returns the value of ret_code.












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__
|
char  *(*XESetErrorString(display, extension, proc))()
      Display *display;
      int extension;
      char *(*proc)();


display   Specifies the connection to the X server.

extension Specifies the extension number.

proc	  Specifies the procedure to call to obtain an error
	  string.
|__

The XGetErrorText function returns a string to the user for
an error.  XESetErrorString allows you to define a procedure
to be called that should return a pointer to the error mes-
sage.  The following is an example.

__
|
(*proc)(display, code, codes, buffer, nbytes)
     Display *display;
     int code;
     XExtCodes *codes;
     char *buffer;
     int nbytes;

|__

Your procedure is called with the error code for every error
detected.  You should copy nbytes of a null-terminated
string containing the error message into buffer.
__
|
void (*XESetPrintErrorValues(display, extension, proc))()
      Display *display;
      int extension;
      void (*proc)();


display   Specifies the connection to the X server.

extension Specifies the extension number.

proc	  Specifies the procedure to call when an error is
	  printed.
|__

The XESetPrintErrorValues function defines a procedure to be
called when an extension error is printed, to print the
error values.  Use this function for extension errors that
contain additional error values beyond those in a core X



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error.	It returns any previously defined procedure.

When Xlib needs to print an error, the procedure is called
with these arguments:

__
|
void (*proc)(display, ev, fp)
     Display *display;
     XErrorEvent *ev;
     void *fp;

|__

The structure pointed at by ev is guaranteed to be as large
as an XEvent structure and so can be cast to a type larger
than an XErrorEvent to obtain additional values set by using
XESetWireToError.  The underlying type of the fp argument is
system dependent; on a POSIX-compliant system, fp should be
cast to type FILE*.
__
|
int (*XESetFlushGC(display, extension, proc))()
      Display *display;
      int extension;
      int *(*proc)();


display   Specifies the connection to the X server.

extension Specifies the extension number.

proc	  Specifies the procedure to call when a GC is
	  flushed.
|__

The procedure set by the XESetFlushGC function has the same
interface as the procedure set by the XESetCopyGC function,
but is called when a GC cache needs to be updated in the
server.

















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__
|
int (*XESetBeforeFlush(display, extension, proc))()
      Display *display;
      int extension;
      int *(*proc)();


display   Specifies the connection to the X server.

extension Specifies the extension number.

proc	  Specifies the procedure to call when a buffer is
	  flushed.
|__

The XESetBeforeFlush function defines a procedure to be
called when data is about to be sent to the server.  When
data is about to be sent, your procedure is called one or
more times with these arguments:

__
|
void (*proc)(display, codes, data, len)
     Display *display;
     XExtCodes *codes;
     char *data;
     long len;

|__

The data argument specifies a portion of the outgoing data
buffer, and its length in bytes is specified by the len
argument.  Your procedure must not alter the contents of the
data and must not do additional protocol requests to the
same display.

Hooks onto Xlib Data Structures

Various Xlib data structures have provisions for extension
procedures to chain extension supplied data onto a list.
These structures are GC, Visual, Screen, ScreenFormat, Dis-
play, and XFontStruct.	Because the list pointer is always
the first member in the structure, a single set of proce-
dures can be used to manipulate the data on these lists.

The following structure is used in the functions in this
section and is defined in <X11/Xlib.h>:










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__
|
typedef struct _XExtData {
     int number;	      /* number returned by XInitExtension */
     struct _XExtData *next;  /* next item on list of data for structure */
     int (*free_private)();   /* if defined,  called to free private */
     XPointer private_data;   /* data private to this extension. */
} XExtData;

|__

When any of the data structures listed above are freed, the
list is walked, and the structure's free procedure (if any)
is called.  If free is NULL, then the library frees both the
data pointed to by the private_data member and the structure
itself.

__
|
union {Display *display;
     GC gc;
     Visual *visual;
     Screen *screen;
     ScreenFormat *pixmap_format;
     XFontStruct *font } XEDataObject;

|__

__
|
XExtData **XEHeadOfExtensionList(object)
     XEDataObject object;


object	  Specifies the object.
|__

The XEHeadOfExtensionList function returns a pointer to the
list of extension structures attached to the specified
object.  In concert with XAddToExtensionList, XEHeadOfExten-
sionList allows an extension to attach arbitrary data to any
of the structures of types contained in XEDataObject.
















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__
|
XAddToExtensionList(structure, ext_data)
      XExtData **structure;
      XExtData *ext_data;


structure Specifies the extension list.

ext_data  Specifies the extension data structure to add.
|__

The structure argument is a pointer to one of the data
structures enumerated above.  You must initialize
ext_data->number with the extension number before calling
this function.
__
|
XExtData *XFindOnExtensionList(structure, number)
      struct _XExtData **structure;
      int number;


structure Specifies the extension list.

number	  Specifies the extension number from XInitExten-
	  sion.
|__

The XFindOnExtensionList function returns the first exten-
sion data structure for the extension numbered number.	It
is expected that an extension will add at most one extension
data structure to any single data structure's extension data
list.  There is no way to find additional structures.

The XAllocID macro, which allocates and returns a resource
ID, is defined in <X11/Xlib.h>.
__
|
XAllocID(display)
     Display *display;


display   Specifies the connection to the X server.
|__

This macro is a call through the Display structure to an
internal resource ID allocator.  It returns a resource ID
that you can use when creating new resources.

The XAllocIDs macro allocates and returns an array of
resource ID.






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__
|
XAllocIDs(display, ids_return, count)
     Display *display;
     XID *ids_return;
     int count;


display   Specifies the connection to the X server.

ids_return
	  Returns the resource IDs.

rep	  Specifies the number of resource IDs requested.
|__

This macro is a call through the Display structure to an
internal resource ID allocator.  It returns resource IDs to
the array supplied by the caller.  To correctly handle auto-
matic reuse of resource IDs, you must call XAllocIDs when
requesting multiple resource IDs.  This call might generate
protocol requests.

GC Caching

GCs are cached by the library to allow merging of indepen-
dent change requests to the same GC into single protocol
requests.  This is typically called a write-back cache.  Any
extension procedure whose behavior depends on the contents
of a GC must flush the GC cache to make sure the server has
up-to-date contents in its GC.

The FlushGC macro checks the dirty bits in the library's GC
structure and calls _XFlushGCCache if any elements have
changed.  The FlushGC macro is defined as follows:
__
|
FlushGC(display, gc)
      Display *display;
      GC gc;


display   Specifies the connection to the X server.

gc	  Specifies the GC.
|__

Note that if you extend the GC to add additional resource ID
components, you should ensure that the library stub sends
the change request immediately.  This is because a client
can free a resource immediately after using it, so if you
only stored the value in the cache without forcing a proto-
col request, the resource might be destroyed before being
set into the GC.  You can use the _XFlushGCCache procedure
to force the cache to be flushed.  The _XFlushGCCache



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procedure is defined as follows:
__
|
_XFlushGCCache(display, gc)
      Display *display;
      GC gc;


display   Specifies the connection to the X server.

gc	  Specifies the GC.
|__


Graphics Batching

If you extend X to add more poly graphics primitives, you
may be able to take advantage of facilities in the library
to allow back-to-back single calls to be transformed into
poly requests.	This may dramatically improve performance of
programs that are not written using poly requests.  A
pointer to an xReq, called last_req in the display struc-
ture, is the last request being processed.  By checking that
the last request type, drawable, gc, and other options are
the same as the new one and that there is enough space left
in the buffer, you may be able to just extend the previous
graphics request by extending the length field of the
request and appending the data to the buffer.  This can
improve performance by five times or more in naive programs.
For example, here is the source for the XDrawPoint stub.
(Writing extension stubs is discussed in the next section.)


























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 __
|
     #include <X11/Xlibint.h>

     /* precompute the maximum size of batching request allowed */

     static int size = sizeof(xPolyPointReq) + EPERBATCH * sizeof(xPoint);

     XDrawPoint(dpy, d, gc, x, y)
	 register Display *dpy;
	 Drawable d;
	 GC gc;
	 int x, y; /* INT16 */
     {
	 xPoint *point;
	 LockDisplay(dpy);
	 FlushGC(dpy, gc);
	 {
	 register xPolyPointReq *req = (xPolyPointReq *) dpy->last_req;
	 /* if same as previous request, with same drawable, batch requests */
	 if (
	       (req->reqType == X_PolyPoint)
	    && (req->drawable == d)
	    && (req->gc == gc->gid)
	    && (req->coordMode == CoordModeOrigin)
	    && ((dpy->bufptr + sizeof (xPoint)) <= dpy->bufmax)
	    && (((char *)dpy->bufptr - (char *)req) < size) ) {
	      point = (xPoint *) dpy->bufptr;
	      req->length += sizeof (xPoint) >> 2;
	      dpy->bufptr += sizeof (xPoint);
	      }

	 else {
	     GetReqExtra(PolyPoint, 4, req); /* 1 point = 4 bytes */
	     req->drawable = d;
	     req->gc = gc->gid;
	     req->coordMode = CoordModeOrigin;
	     point = (xPoint *) (req + 1);
	     }
	 point->x = x;
	 point->y = y;
	 }
	 UnlockDisplay(dpy);
	 SyncHandle();
     }
|__

To keep clients from generating very long requests that may
monopolize the server, there is a symbol defined in
<X11/Xlibint.h> of EPERBATCH on the number of requests
batched.  Most of the performance benefit occurs in the
first few merged requests.  Note that FlushGC is called
before picking up the value of last_req, because it may mod-
ify this field.




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Writing Extension Stubs

All X requests always contain the length of the request,
expressed as a 16-bit quantity of 32 bits.  This means that
a single request can be no more than 256K bytes in length.
Some servers may not support single requests of such a
length.  The value of dpy->max_request_size contains the
maximum length as defined by the server implementation.  For
further information, see ``X Window System Protocol.''

Requests, Replies, and Xproto.h

The <X11/Xproto.h> file contains three sets of definitions
that are of interest to the stub implementor: request names,
request structures, and reply structures.

You need to generate a file equivalent to <X11/Xproto.h> for
your extension and need to include it in your stub proce-
dure.  Each stub procedure also must include <X11/Xlib-
int.h>.

The identifiers are deliberately chosen in such a way that,
if the request is called X_DoSomething, then its request
structure is xDoSomethingReq, and its reply is xDoSomethin-
gReply.  The GetReq family of macros, defined in <X11/Xlib-
int.h>, takes advantage of this naming scheme.

For each X request, there is a definition in <X11/Xproto.h>
that looks similar to this:


     #define X_DoSomething   42

In your extension header file, this will be a minor opcode,
instead of a major opcode.

Request Format

Every request contains an 8-bit major opcode and a 16-bit
length field expressed in units of 4 bytes.  Every request
consists of 4 bytes of header (containing the major opcode,
the length field, and a data byte) followed by zero or more
additional bytes of data.  The length field defines the
total length of the request, including the header.  The
length field in a request must equal the minimum length
required to contain the request.  If the specified length is
smaller or larger than the required length, the server
should generate a BadLength error.  Unused bytes in a
request are not required to be zero.  Extensions should be
designed in such a way that long protocol requests can be
split up into smaller requests, if it is possible to exceed
the maximum request size of the server.  The protocol guar-
antees the maximum request size to be no smaller than 4096
units (16384 bytes).



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Major opcodes 128 through 255 are reserved for extensions.
Extensions are intended to contain multiple requests, so
extension requests typically have an additional minor opcode
encoded in the second data byte in the request header, but
the placement and interpretation of this minor opcode as
well as all other fields in extension requests are not
defined by the core protocol.  Every request is implicitly
assigned a sequence number (starting with one) used in
replies, errors, and events.

To help but not cure portability problems to certain
machines, the B16 and B32 macros have been defined so that
they can become bitfield specifications on some machines.
For example, on a Cray, these should be used for all 16-bit
and 32-bit quantities, as discussed below.

Most protocol requests have a corresponding structure type-
def in <X11/Xproto.h>, which looks like:

__
|
typedef struct _DoSomethingReq {
     CARD8 reqType;	      /* X_DoSomething */
     CARD8 someDatum;	      /* used differently in different requests */
     CARD16 length B16;       /* total # of bytes in request, divided by 4 */
     ...
     /* request-specific data */
     ...
} xDoSomethingReq;

|__

If a core protocol request has a single 32-bit argument, you
need not declare a request structure in your extension
header file.  Instead, such requests use the xResourceReq
structure in <X11/Xproto.h>.  This structure is used for any
request whose single argument is a Window, Pixmap, Drawable,
GContext, Font, Cursor, Colormap, Atom, or VisualID.

__
|
typedef struct _ResourceReq {
     CARD8 reqType;	      /* the request type, e.g. X_DoSomething */
     BYTE pad;		      /* not used */
     CARD16 length B16;       /* 2 (= total # of bytes in request, divided by 4) */
     CARD32 id B32;	      /* the Window, Drawable, Font, GContext, etc. */
} xResourceReq;

|__

If convenient, you can do something similar in your exten-
sion header file.





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In both of these structures, the reqType field identifies
the type of the request (for example, X_MapWindow or X_Cre-
atePixmap).  The length field tells how long the request is
in units of 4-byte longwords.  This length includes both the
request structure itself and any variable-length data, such
as strings or lists, that follow the request structure.
Request structures come in different sizes, but all requests
are padded to be multiples of four bytes long.

A few protocol requests take no arguments at all.  Instead,
they use the xReq structure in <X11/Xproto.h>, which con-
tains only a reqType and a length (and a pad byte).

If the protocol request requires a reply, then
<X11/Xproto.h> also contains a reply structure typedef:

__
|
typedef struct _DoSomethingReply {
     BYTE type; 	      /* always X_Reply */
     BYTE someDatum;	      /* used differently in different requests */
     CARD16 sequenceNumber B16;/* # of requests sent so far */
     CARD32 length B32;       /* # of additional bytes, divided by 4 */
     ...
     /* request-specific data */
     ...
} xDoSomethingReply;

|__

Most of these reply structures are 32 bytes long.  If there
are not that many reply values, then they contain a suffi-
cient number of pad fields to bring them up to 32 bytes.
The length field is the total number of bytes in the request
minus 32, divided by 4.  This length will be nonzero only
if:

o    The reply structure is followed by variable-length
     data, such as a list or string.

o    The reply structure is longer than 32 bytes.

Only GetWindowAttributes, QueryFont, QueryKeymap, and
GetKeyboardControl have reply structures longer than 32
bytes in the core protocol.

A few protocol requests return replies that contain no data.
<X11/Xproto.h> does not define reply structures for these.
Instead, they use the xGenericReply structure, which con-
tains only a type, length, and sequence number (and suffi-
cient padding to make it 32 bytes long).






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Starting to Write a Stub Procedure

An Xlib stub procedure should start like this:


     #include "<X11/Xlibint.h>

     XDoSomething (arguments, ... )
     /* argument declarations */
     {

     register XDoSomethingReq *req;
     ...

If the protocol request has a reply, then the variable dec-
larations should include the reply structure for the
request.  The following is an example:


     xDoSomethingReply rep;


Locking Data Structures

To lock the display structure for systems that want to sup-
port multithreaded access to a single display connection,
each stub will need to lock its critical section.  Gener-
ally, this section is the point from just before the appro-
priate GetReq call until all arguments to the call have been
stored into the buffer.  The precise instructions needed for
this locking depend upon the machine architecture.  Two
calls, which are generally implemented as macros, have been
provided.
__
|
LockDisplay(display)
      Display *display;



UnlockDisplay(display)
      Display *display;


display   Specifies the connection to the X server.
|__


Sending the Protocol Request and Arguments

After the variable declarations, a stub procedure should
call one of four macros defined in <X11/Xlibint.h>: GetReq,
GetReqExtra, GetResReq, or GetEmptyReq.  All of these macros
take, as their first argument, the name of the protocol



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request as declared in <X11/Xproto.h> except with X_
removed.  Each one declares a Display structure pointer,
called dpy, and a pointer to a request structure, called
req, which is of the appropriate type.	The macro then
appends the request structure to the output buffer, fills in
its type and length field, and sets req to point to it.

If the protocol request has no arguments (for instance,
X_GrabServer), then use GetEmptyReq.


     GetEmptyReq (DoSomething, req);

If the protocol request has a single 32-bit argument (such
as a Pixmap, Window, Drawable, Atom, and so on), then use
GetResReq.  The second argument to the macro is the 32-bit
object.  X_MapWindow is a good example.


     GetResReq (DoSomething, rid, req);

The rid argument is the Pixmap, Window, or other resource
ID.

If the protocol request takes any other argument list, then
call GetReq.  After the GetReq, you need to set all the
other fields in the request structure, usually from argu-
ments to the stub procedure.


     GetReq (DoSomething, req);
     /* fill in arguments here */
     req->arg1 = arg1;
     req->arg2 = arg2;
     ...

A few stub procedures (such as XCreateGC and XCreatePixmap)
return a resource ID to the caller but pass a resource ID as
an argument to the protocol request.  Such procedures use
the macro XAllocID to allocate a resource ID from the range
of IDs that were assigned to this client when it opened the
connection.


     rid = req->rid = XAllocID();
     ...
     return (rid);

Finally, some stub procedures transmit a fixed amount of
variable-length data after the request.  Typically, these
procedures (such as XMoveWindow and XSetBackground) are spe-
cial cases of more general functions like XMoveResizeWindow
and XChangeGC.	These procedures use GetReqExtra, which is
the same as GetReq except that it takes an additional



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argument (the number of extra bytes to allocate in the out-
put buffer after the request structure).  This number should
always be a multiple of four.

Variable Length Arguments

Some protocol requests take additional variable-length data
that follow the xDoSomethingReq structure.  The format of
this data varies from request to request.  Some requests
require a sequence of 8-bit bytes, others a sequence of
16-bit or 32-bit entities, and still others a sequence of
structures.

It is necessary to add the length of any variable-length
data to the length field of the request structure.  That
length field is in units of 32-bit longwords.  If the data
is a string or other sequence of 8-bit bytes, then you must
round the length up and shift it before adding:


     req->length += (nbytes+3)>>2;

To transmit variable-length data, use the Data macros.	If
the data fits into the output buffer, then this macro copies
it to the buffer.  If it does not fit, however, the Data
macro calls _XSend, which transmits first the contents of
the buffer and then your data.	The Data macros take three
arguments: the display, a pointer to the beginning of the
data, and the number of bytes to be sent.
__
|
Data(display, (char *) data, nbytes);

Data16(display, (short *) data, nbytes);

Data32(display, (long *) data, nbytes);

|__

Data, Data16, and Data32 are macros that may use their last
argument more than once, so that argument should be a vari-
able rather than an expression such as
``nitems*sizeof(item)''.  You should do that kind of compu-
tation in a separate statement before calling them.  Use the
appropriate macro when sending byte, short, or long data.

If the protocol request requires a reply, then call the pro-
cedure _XSend instead of the Data macro.  _XSend takes the
same arguments, but because it sends your data immediately
instead of copying it into the output buffer (which would
later be flushed anyway by the following call on _XReply),
it is faster.





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Replies

If the protocol request has a reply, then call _XReply after
you have finished dealing with all the fixed-length and
variable-length arguments.  _XReply flushes the output
buffer and waits for an xReply packet to arrive.  If any
events arrive in the meantime, _XReply places them in the
queue for later use.
__
|
Status _XReply(display, rep, extra, discard)
      Display *display;
      xReply *rep;
      int extra;
      Bool discard;


display   Specifies the connection to the X server.

rep	  Specifies the reply structure.

extra	  Specifies the number of 32-bit words expected
	  after the replay.

discard   Specifies if any data beyond that specified in the
	  extra argument should be discarded.
|__

The _XReply function waits for a reply packet and copies its
contents into the specified rep.  _XReply handles error and
event packets that occur before the reply is received.
_XReply takes four arguments:

o    A Display * structure

o    A pointer to a reply structure (which must be cast to
     an xReply *)

o    The number of additional 32-bit words (beyond
     sizeof(xReply) = 32 bytes) in the reply structure

o    A Boolean that indicates whether _XReply is to discard
     any additional bytes beyond those it was told to read

Because most reply structures are 32 bytes long, the third
argument is usually 0.	The only core protocol exceptions
are the replies to GetWindowAttributes, QueryFont,
QueryKeymap, and GetKeyboardControl, which have longer
replies.

The last argument should be False if the reply structure is
followed by additional variable-length data (such as a list
or string).  It should be True if there is not any variable-
length data.



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			    Note

     This last argument is provided for upward-compati-
     bility reasons to allow a client to communicate
     properly with a hypothetical later version of the
     server that sends more data than the client
     expected.	For example, some later version of
     GetWindowAttributes might use a larger, but com-
     patible, xGetWindowAttributesReply that contains
     additional attribute data at the end.

_XReply returns True if it received a reply successfully or
False if it received any sort of error.

For a request with a reply that is not followed by variable-
length data, you write something like:


     _XReply(display, (xReply *)&rep, 0, True);
     *ret1 = rep.ret1;
     *ret2 = rep.ret2;
     *ret3 = rep.ret3;
     ...
     UnlockDisplay(dpy);
     SyncHandle();
     return (rep.ret4);
     }

If there is variable-length data after the reply, change the
True to False, and use the appropriate _XRead function to
read the variable-length data.

__
|
_XRead(display, data_return, nbytes)
       Display *display;
       char *data_return;
       long nbytes;


display   Specifies the connection to the X server.

data_return
	  Specifies the buffer.

nbytes	  Specifies the number of bytes required.
|__

The _XRead function reads the specified number of bytes into
data_return.







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__
|
_XRead16(display, data_return, nbytes)
       Display *display;
       short *data_return;
       long nbytes;


display   Specifies the connection to the X server.

data_return
	  Specifies the buffer.

nbytes	  Specifies the number of bytes required.
|__

The _XRead16 function reads the specified number of bytes,
unpacking them as 16-bit quantities, into the specified
array as shorts.

__
|
_XRead32(display, data_return, nbytes)
       Display *display;
       long *data_return;
       long nbytes;


display   Specifies the connection to the X server.

data_return
	  Specifies the buffer.

nbytes	  Specifies the number of bytes required.
|__

The _XRead32 function reads the specified number of bytes,
unpacking them as 32-bit quantities, into the specified
array as longs.



















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__
|
_XRead16Pad(display, data_return, nbytes)
       Display *display;
       short *data_return;
       long nbytes;


display   Specifies the connection to the X server.

data_return
	  Specifies the buffer.

nbytes	  Specifies the number of bytes required.
|__

The _XRead16Pad function reads the specified number of
bytes, unpacking them as 16-bit quantities, into the speci-
fied array as shorts.  If the number of bytes is not a mul-
tiple of four, _XRead16Pad reads and discards up to two
additional pad bytes.

__
|
_XReadPad(display, data_return, nbytes)
       Display *display;
       char *data_return;
       long nbytes;


display   Specifies the connection to the X server.

data_return
	  Specifies the buffer.

nbytes	  Specifies the number of bytes required.
|__

The _XReadPad function reads the specified number of bytes
into data_return.  If the number of bytes is not a multiple
of four, _XReadPad reads and discards up to three additional
pad bytes.

Each protocol request is a little different.  For further
information, see the Xlib sources for examples.

Synchronous Calling

Each procedure should have a call, just before returning to
the user, to a macro called SyncHandle.  If synchronous mode
is enabled (see XSynchronize), the request is sent immedi-
ately.	The library, however, waits until any error the pro-
cedure could generate at the server has been handled.





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Allocating and Deallocating Memory

To support the possible reentry of these procedures, you
must observe several conventions when allocating and deallo-
cating memory, most often done when returning data to the
user from the window system of a size the caller could not
know in advance (for example, a list of fonts or a list of
extensions).  The standard C library functions on many sys-
tems are not protected against signals or other multi-
threaded uses.	The following analogies to standard I/O
library functions have been defined:

Xmalloc()   Replaces malloc()
XFree()     Replaces free()
Xcalloc()   Replaces calloc()


These should be used in place of any calls you would make to
the normal C library functions.

If you need a single scratch buffer inside a critical sec-
tion (for example, to pack and unpack data to and from the
wire protocol), the general memory allocators may be too
expensive to use (particularly in output functions, which
are performance critical).  The following function returns a
scratch buffer for use within a critical section:
__
|
char *_XAllocScratch(display, nbytes)
      Display *display;
      unsigned long nbytes;


display   Specifies the connection to the X server.

nbytes	  Specifies the number of bytes required.
|__

This storage must only be used inside of a critical section
of your stub.  The returned pointer cannot be assumed valid
after any call that might permit another thread to execute
inside Xlib.  For example, the pointer cannot be assumed
valid after any use of the GetReq or Data families of
macros, after any use of _XReply, or after any use of the
_XSend or _XRead families of functions.


The following function returns a scratch buffer for use
across critical sections:








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__
|
char *_XAllocTemp(display, nbytes)
      Display *display;
      unsigned long nbytes;


display   Specifies the connection to the X server.

nbytes	  Specifies the number of bytes required.
|__

This storage can be used across calls that might permit
another thread to execute inside Xlib.	The storage must be
explicitly returned to Xlib.  The following function returns
the storage:
__
|
void _XFreeTemp(display, buf, nbytes)
      Display *display;
      char *buf;
      unsigned long nbytes;


display   Specifies the connection to the X server.

buf	  Specifies the buffer to return.

nbytes	  Specifies the size of the buffer.
|__

You must pass back the same pointer and size that were
returned by _XAllocTemp.

Portability Considerations

Many machine architectures, including many of the more
recent RISC architectures, do not correctly access data at
unaligned locations; their compilers pad out structures to
preserve this characteristic.  Many other machines capable
of unaligned references pad inside of structures as well to
preserve alignment, because accessing aligned data is usu-
ally much faster.  Because the library and the server use
structures to access data at arbitrary points in a byte
stream, all data in request and reply packets must be natu-
rally aligned; that is, 16-bit data starts on 16-bit bound-
aries in the request and 32-bit data on 32-bit boundaries.
All requests must be a multiple of 32 bits in length to pre-
serve the natural alignment in the data stream.  You must
pad structures out to 32-bit boundaries.  Pad information
does not have to be zeroed unless you want to preserve such
fields for future use in your protocol requests.  Floating
point varies radically between machines and should be
avoided completely if at all possible.




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This code may run on machines with 16-bit ints.  So, if any
integer argument, variable, or return value either can take
only nonnegative values or is declared as a CARD16 in the
protocol, be sure to declare it as unsigned int and not as
int.  (This, of course, does not apply to Booleans or enu-
merations.)

Similarly, if any integer argument or return value is
declared CARD32 in the protocol, declare it as an unsigned
long and not as int or long.  This also goes for any inter-
nal variables that may take on values larger than the maxi-
mum 16-bit unsigned int.

The library currently assumes that a char is 8 bits, a short
is 16 bits, an int is 16 or 32 bits, and a long is 32 bits.
The PackData macro is a half-hearted attempt to deal with
the possibility of 32 bit shorts.  However, much more work
is needed to make this work properly.

Deriving the Correct Extension Opcode

The remaining problem a writer of an extension stub proce-
dure faces that the core protocol does not face is to map
from the call to the proper major and minor opcodes.  While
there are a number of strategies, the simplest and fastest
is outlined below.

1.   Declare an array of pointers, _NFILE long (this is nor-
     mally found in <stdio.h> and is the number of file
     descriptors supported on the system) of type XExtCodes.
     Make sure these are all initialized to NULL.

2.   When your stub is entered, your initialization test is
     just to use the display pointer passed in to access the
     file descriptor and an index into the array.  If the
     entry is NULL, then this is the first time you are
     entering the procedure for this display.  Call your
     initialization procedure and pass to it the display
     pointer.

3.   Once in your initialization procedure, call XInitExten-
     sion; if it succeeds, store the pointer returned into
     this array.  Make sure to establish a close display
     handler to allow you to zero the entry.  Do whatever
     other initialization your extension requires.  (For
     example, install event handlers and so on.)  Your ini-
     tialization procedure would normally return a pointer
     to the XExtCodes structure for this extension, which is
     what would normally be found in your array of pointers.

4.   After returning from your initialization procedure, the
     stub can now continue normally, because it has its
     major opcode safely in its hand in the XExtCodes struc-
     ture.



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			   Appendix D

		     Compatibility Functions




The X Version 11 and X Version 10 functions discussed in
this appendix are obsolete, have been superseded by newer X
Version 11 functions, and are maintained for compatibility
reasons only.

X Version 11 Compatibility Functions

You can use the X Version 11 compatibility functions to:

o    Set standard properties

o    Set and get window sizing hints

o    Set and get an XStandardColormap structure

o    Parse window geometry

o    Get X environment defaults

Setting Standard Properties

To specify a minimum set of properties describing the sim-
plest application, use XSetStandardProperties.	This func-
tion has been superseded by XSetWMProperties and sets all or
portions of the WM_NAME, WM_ICON_NAME, WM_HINTS, WM_COMMAND,
and WM_NORMAL_HINTS properties.






















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__
|
XSetStandardProperties(display, w, window_name, icon_name, icon_pixmap, argv, argc, hints)
      Display *display;
      Window w;
      char *window_name;
      char *icon_name;
      Pixmap icon_pixmap;
      char **argv;
      int argc;
      XSizeHints *hints;


display   Specifies the connection to the X server.

w	  Specifies the window.

window_name
	  Specifies the window name, which should be a null-
	  terminated string.

icon_name Specifies the icon name, which should be a null-
	  terminated string.

icon_pixmap
	  Specifies the bitmap that is to be used for the
	  icon or None.

argv	  Specifies the application's argument list.

argc	  Specifies the number of arguments.

hints	  Specifies a pointer to the size hints for the win-
	  dow in its normal state.
|__

The XSetStandardProperties function provides a means by
which simple applications set the most essential properties
with a single call.  XSetStandardProperties should be used
to give a window manager some information about your pro-
gram's preferences.  It should not be used by applications
that need to communicate more information than is possible
with XSetStandardProperties.  (Typically, argv is the argv
array of your main program.)  If the strings are not in the
Host Portable Character Encoding, the result is implementa-
tion-dependent.

XSetStandardProperties can generate BadAlloc and BadWindow
errors.

Setting and Getting Window Sizing Hints

Xlib provides functions that you can use to set or get win-
dow sizing hints.  The functions discussed in this section
use the flags and the XSizeHints structure, as defined in



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the <X11/Xutil.h> header file and use the WM_NORMAL_HINTS
property.


To set the size hints for a given window in its normal
state, use XSetNormalHints.  This function has been super-
seded by XSetWMNormalHints.
__
|
XSetNormalHints(display, w, hints)
      Display *display;
      Window w;
      XSizeHints *hints;


display   Specifies the connection to the X server.

w	  Specifies the window.

hints	  Specifies a pointer to the size hints for the win-
	  dow in its normal state.
|__

The XSetNormalHints function sets the size hints structure
for the specified window.  Applications use XSetNormalHints
to inform the window manager of the size or position desir-
able for that window.  In addition, an application that
wants to move or resize itself should call XSetNormalHints
and specify its new desired location and size as well as
making direct Xlib calls to move or resize.  This is because
window managers may ignore redirected configure requests,
but they pay attention to property changes.

To set size hints, an application not only must assign val-
ues to the appropriate members in the hints structure but
also must set the flags member of the structure to indicate
which information is present and where it came from.  A call
to XSetNormalHints is meaningless, unless the flags member
is set to indicate which members of the structure have been
assigned values.

XSetNormalHints can generate BadAlloc and BadWindow errors.


To return the size hints for a window in its normal state,
use XGetNormalHints.  This function has been superseded by
XGetWMNormalHints.










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__
|
Status XGetNormalHints(display, w, hints_return)
      Display *display;
      Window w;
      XSizeHints *hints_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

hints_return
	  Returns the size hints for the window in its
	  normal state.
|__

The XGetNormalHints function returns the size hints for a
window in its normal state.  It returns a nonzero status if
it succeeds or zero if the application specified no normal
size hints for this window.

XGetNormalHints can generate a BadWindow error.


The next two functions set and read the WM_ZOOM_HINTS prop-
erty.

To set the zoom hints for a window, use XSetZoomHints.	This
function is no longer supported by the Inter-Client Communi-
cation Conventions Manual.
__
|
XSetZoomHints(display, w, zhints)
      Display *display;
      Window w;
      XSizeHints *zhints;


display   Specifies the connection to the X server.

w	  Specifies the window.

zhints	  Specifies a pointer to the zoom hints.
|__

Many window managers think of windows in one of three
states: iconic, normal, or zoomed.  The XSetZoomHints func-
tion provides the window manager with information for the
window in the zoomed state.

XSetZoomHints can generate BadAlloc and BadWindow errors.


To read the zoom hints for a window, use XGetZoomHints.



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This function is no longer supported by the Inter-Client
Communication Conventions Manual.
__
|
Status XGetZoomHints(display, w, zhints_return)
      Display *display;
      Window w;
      XSizeHints *zhints_return;


display   Specifies the connection to the X server.

w	  Specifies the window.

zhints_return
	  Returns the zoom hints.
|__

The XGetZoomHints function returns the size hints for a win-
dow in its zoomed state.  It returns a nonzero status if it
succeeds or zero if the application specified no zoom size
hints for this window.

XGetZoomHints can generate a BadWindow error.


To set the value of any property of type WM_SIZE_HINTS, use
XSetSizeHints.	This function has been superseded by XSetWM-
SizeHints.
__
|
XSetSizeHints(display, w, hints, property)
      Display *display;
      Window w;
      XSizeHints *hints;
      Atom property;


display   Specifies the connection to the X server.

w	  Specifies the window.

hints	  Specifies a pointer to the size hints.

property  Specifies the property name.
|__

The XSetSizeHints function sets the XSizeHints structure for
the named property and the specified window.  This is used
by XSetNormalHints and XSetZoomHints and can be used to set
the value of any property of type WM_SIZE_HINTS.  Thus, it
may be useful if other properties of that type get defined.





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XSetSizeHints can generate BadAlloc, BadAtom, and BadWindow
errors.


To read the value of any property of type WM_SIZE_HINTS, use
XGetSizeHints.	This function has been superseded by XGetWM-
SizeHints.
__
|
Status XGetSizeHints(display, w, hints_return, property)
      Display *display;
      Window w;
      XSizeHints *hints_return;
      Atom property;


display   Specifies the connection to the X server.

w	  Specifies the window.

hints_return
	  Returns the size hints.

property  Specifies the property name.
|__

The XGetSizeHints function returns the XSizeHints structure
for the named property and the specified window.  This is
used by XGetNormalHints and XGetZoomHints.  It also can be
used to retrieve the value of any property of type
WM_SIZE_HINTS.	Thus, it may be useful if other properties
of that type get defined.  XGetSizeHints returns a nonzero
status if a size hint was defined or zero otherwise.

XGetSizeHints can generate BadAtom and BadWindow errors.

Getting and Setting an XStandardColormap Structure

To get the XStandardColormap structure associated with one
of the described atoms, use XGetStandardColormap.  This
function has been superseded by XGetRGBColormap.
















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__
|
Status XGetStandardColormap(display, w, colormap_return, property)
      Display *display;
      Window w;
      XStandardColormap *colormap_return;
      Atom property;	      /* RGB_BEST_MAP, etc. */


display   Specifies the connection to the X server.

w	  Specifies the window.

colormap_return
	  Returns the colormap associated with the specified
	  atom.

property  Specifies the property name.
|__

The XGetStandardColormap function returns the colormap defi-
nition associated with the atom supplied as the property
argument.  XGetStandardColormap returns a nonzero status if
successful and zero otherwise.	For example, to fetch the
standard GrayScale colormap for a display, you use XGetStan-
dardColormap with the following syntax:

__
|
XGetStandardColormap(dpy, DefaultRootWindow(dpy), &cmap, XA_RGB_GRAY_MAP);

|__

See section 14.3 for the semantics of standard colormaps.

XGetStandardColormap can generate BadAtom and BadWindow
errors.


To set a standard colormap, use XSetStandardColormap.  This
function has been superseded by XSetRGBColormap.

















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__
|
XSetStandardColormap(display, w, colormap, property)
      Display *display;
      Window w;
      XStandardColormap *colormap;
      Atom property;	      /* RGB_BEST_MAP, etc. */


display   Specifies the connection to the X server.

w	  Specifies the window.

colormap  Specifies the colormap.

property  Specifies the property name.
|__

The XSetStandardColormap function usually is only used by
window or session managers.

XSetStandardColormap can generate BadAlloc, BadAtom, Bad-
Drawable, and BadWindow errors.

Parsing Window Geometry

To parse window geometry given a user-specified position and
a default position, use XGeometry.  This function has been
superseded by XWMGeometry.





























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__
|
int XGeometry(display, screen, position, default_position, bwidth, fwidth, fheight, xadder,
		  yadder, x_return, y_return, width_return, height_return)
      Display *display;
      int screen;
      char *position, *default_position;
      unsigned int bwidth;
      unsigned int fwidth, fheight;
      int xadder, yadder;
      int *x_return, *y_return;
      int *width_return, *height_return;


display   Specifies the connection to the X server.

screen	  Specifies the screen.

position
default_position
	  Specify the geometry specifications.

bwidth	  Specifies the border width.

fheight
fwidth	  Specify the font height and width in pixels
	  (increment size).

xadder
yadder	  Specify additional interior padding needed in the
	  window.

x_return
y_return  Return the x and y offsets.

width_return
height_return
	  Return the width and height determined.
|__

You pass in the border width (bwidth), size of the incre-
ments fwidth and fheight (typically font width and height),
and any additional interior space (xadder and yadder) to
make it easy to compute the resulting size.  The XGeometry
function returns the position the window should be placed
given a position and a default position.  XGeometry deter-
mines the placement of a window using a geometry specifica-
tion as specified by XParseGeometry and the additional
information about the window.  Given a fully qualified
default geometry specification and an incomplete geometry
specification, XParseGeometry returns a bitmask value as
defined above in the XParseGeometry call, by using the posi-
tion argument.





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The returned width and height will be the width and height
specified by default_position as overridden by any user-
specified position.  They are not affected by fwidth,
fheight, xadder, or yadder.  The x and y coordinates are
computed by using the border width, the screen width and
height, padding as specified by xadder and yadder, and the
fheight and fwidth times the width and height from the geom-
etry specifications.

Getting the X Environment Defaults

The XGetDefault function provides a primitive interface to
the resource manager facilities discussed in chapter 15.  It
is only useful in very simple applications.


__
|
char *XGetDefault(display, program, option)
      Display *display;
      char *program;
      char *option;


display   Specifies the connection to the X server.

program   Specifies the program name for the Xlib defaults
	  (usually argv[0] of the main program).

option	  Specifies the option name.
|__

The XGetDefault function returns the value of the resource
prog.option, where prog is the program argument with the
directory prefix removed and option must be a single compo-
nent.  Note that multilevel resources cannot be used with
XGetDefault.  The class "Program.Name" is always used for
the resource lookup.  If the specified option name does not
exist for this program, XGetDefault returns NULL.  The
strings returned by XGetDefault are owned by Xlib and should
not be modified or freed by the client.

If a database has been set with XrmSetDatabase, that
database is used for the lookup.  Otherwise, a database is
created and is set in the display (as if by calling XrmSet-
Database).  The database is created in the current locale.
To create a database, XGetDefault uses resources from the
RESOURCE_MANAGER property on the root window of screen zero.
If no such property exists, a resource file in the user's
home directory is used.  On a POSIX-conformant system, this
file is $HOME/.Xdefaults.  After loading these defaults,
XGetDefault merges additional defaults specified by the XEN-
VIRONMENT environment variable.  If XENVIRONMENT is defined,
it contains a full path name for the additional resource



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file.  If XENVIRONMENT is not defined, XGetDefault looks for
$HOME/.Xdefaults-name, where name specifies the name of the
machine on which the application is running.

X Version 10 Compatibility Functions

You can use the X Version 10 compatibility functions to:

o    Draw and fill polygons and curves

o    Associate user data with a value

Drawing and Filling Polygons and Curves

Xlib provides functions that you can use to draw or fill
arbitrary polygons or curves.  These functions are provided
mainly for compatibility with X Version 10 and have no
server support.  That is, they call other Xlib functions,
not the server directly.  Thus, if you just have straight
lines to draw, using XDrawLines or XDrawSegments is much
faster.

The functions discussed here provide all the functionality
of the X Version 10 functions XDraw, XDrawFilled, XDrawPat-
terned, XDrawDashed, and XDrawTiled.  They are as compatible
as possible given X Version 11's new line-drawing functions.
One thing to note, however, is that VertexDrawLastPoint is
no longer supported.  Also, the error status returned is the
opposite of what it was under X Version 10 (this is the X
Version 11 standard error status).  XAppendVertex and
XClearVertexFlag from X Version 10 also are not supported.

Just how the graphics context you use is set up actually
determines whether you get dashes or not, and so on.  Lines
are properly joined if they connect and include the closing
of a closed figure  (see XDrawLines).  The functions dis-
cussed here fail (return zero) only if they run out of mem-
ory or are passed a Vertex list that has a Vertex with Ver-
texStartClosed set that is not followed by a Vertex with
VertexEndClosed set.


To achieve the effects of the X Version 10 XDraw, XDraw-
Dashed, and XDrawPatterned, use XDraw.













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__
|
#include <X11/X10.h>

Status XDraw(display, d, gc, vlist, vcount)
     Display *display;
     Drawable d;
     GC gc;
     Vertex *vlist;
     int vcount;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

vlist	  Specifies a pointer to the list of vertices that
	  indicate what to draw.

vcount	  Specifies how many vertices are in vlist.
|__

The XDraw function draws an arbitrary polygon or curve.  The
figure drawn is defined by the specified list of vertices
(vlist).  The points are connected by lines as specified in
the flags in the vertex structure.

Each Vertex, as defined in <X11/X10.h>, is a structure with
the following members:

__
|
typedef struct _Vertex {
     short x,y;
     unsigned short flags;
} Vertex;

|__

The x and y members are the coordinates of the vertex that
are relative to either the upper left inside corner of the
drawable (if VertexRelative is zero) or the previous vertex
(if VertexRelative is one).

The flags, as defined in <X11/X10.h>, are as follows:











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__
|
VertexRelative	  0x0001   /* else abso-
			   lute */
VertexDontDraw	  0x0002   /* else draw */
VertexCurved	  0x0004   /* else
			   straight */
VertexStart-	  0x0008   /* else not */
Closed
VertexEndClosed   0x0010   /* else not */

|__


o    If VertexRelative is not set, the coordinates are abso-
     lute (that is, relative to the drawable's origin).  The
     first vertex must be an absolute vertex.

o    If VertexDontDraw is one, no line or curve is drawn
     from the previous vertex to this one.  This is analo-
     gous to picking up the pen and moving to another place
     before drawing another line.

o    If VertexCurved is one, a spline algorithm is used to
     draw a smooth curve from the previous vertex through
     this one to the next vertex.  Otherwise, a straight
     line is drawn from the previous vertex to this one.  It
     makes sense to set VertexCurved to one only if a previ-
     ous and next vertex are both defined (either explicitly
     in the array or through the definition of a closed
     curve).

o    It is permissible for VertexDontDraw bits and Vertex-
     Curved bits both to be one.  This is useful if you want
     to define the previous point for the smooth curve but
     do not want an actual curve drawing to start until this
     point.

o    If VertexStartClosed is one, then this point marks the
     beginning of a closed curve.  This vertex must be fol-
     lowed later in the array by another vertex whose effec-
     tive coordinates are identical and that has a Vertex-
     EndClosed bit of one.  The points in between form a
     cycle to determine predecessor and successor vertices
     for the spline algorithm.

This function uses these GC components: function, plane-
mask, line-width, line-style, cap-style, join-style, fill-
style, subwindow-mode, clip-x-origin, clip-y-origin, and
clip-mask.  It also uses these GC mode-dependent components:
foreground, background, tile, stipple, tile-stipple-x-ori-
gin, tile-stipple-y-origin, dash-offset, and dash-list.


To achieve the effects of the X Version 10 XDrawTiled and



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XDrawFilled, use XDrawFilled.
__
|
#include <X11/X10.h>

Status XDrawFilled(display, d, gc, vlist, vcount)
     Display *display;
     Drawable d;
     GC gc;
     Vertex *vlist;
     int vcount;


display   Specifies the connection to the X server.

d	  Specifies the drawable.

gc	  Specifies the GC.

vlist	  Specifies a pointer to the list of vertices that
	  indicate what to draw.

vcount	  Specifies how many vertices are in vlist.
|__

The XDrawFilled function draws arbitrary polygons or curves
and then fills them.

This function uses these GC components: function, plane-
mask, line-width, line-style, cap-style, join-style, fill-
style, subwindow-mode, clip-x-origin, clip-y-origin, and
clip-mask.  It also uses these GC mode-dependent components:
foreground, background, tile, stipple, tile-stipple-x-ori-
gin, tile-stipple-y-origin, dash-offset, dash-list, fill-
style, and fill-rule.

Associating User Data with a Value

These functions have been superseded by the context manage-
ment functions (see section 16.10).  It is often necessary
to associate arbitrary information with resource IDs.  Xlib
provides the XAssocTable functions that you can use to make
such an association.  Application programs often need to be
able to easily refer to their own data structures when an
event arrives.	The XAssocTable system provides users of the
X library with a method for associating their own data
structures with X resources (Pixmaps, Fonts, Windows, and so
on).

An XAssocTable can be used to type X resources.  For exam-
ple, the user may want to have three or four types of win-
dows, each with different properties.  This can be accom-
plished by associating each X window ID with a pointer to a
window property data structure	defined  by  the user.	A



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generic type has been defined in the X library for resource
IDs.  It is called an XID.

There are a few  guidelines  that  should be observed when
using an XAssocTable:

o    All  XIDs	are  relative  to  the	specified display.

o    Because  of  the  hashing	scheme	used  by  the  asso-
     ciation mechanism, the following rules for determining
     the size of a XAssocTable should be followed.  Associa-
     tions will be  made  and  looked  up  more efficiently
     if  the  table  size  (number  of	buckets in the hash-
     ing system) is a power of two and if there are not more
     than 8 XIDs  per bucket.


To return a pointer to a new XAssocTable, use XCreateAs-
socTable.
__
|
XAssocTable *XCreateAssocTable(size)
      int size;


size	  Specifies the number of buckets in the hash system
	  of XAssocTable.
|__

The size argument specifies the number of buckets in the
hash system of XAssocTable.  For  reasons  of  efficiency
the number of buckets should be a power of two.  Some size
suggestions  might  be:  use  32 buckets  per  100  objects,
and a reasonable maximum number of objects per buckets is 8.
If  an	error  allocating  memory  for	the XAssocTable
occurs, a NULL pointer is returned.


To create an entry in a given XAssocTable, use XMakeAssoc.


















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__
|
XMakeAssoc(display, table, x_id, data)
      Display *display;
      XAssocTable *table;
      XID x_id;
      char *data;


display   Specifies the connection to the X server.

table	  Specifies the assoc table.

x_id	  Specifies the X resource ID.

data	  Specifies the data to be associated with the X
	  resource ID.
|__

The XMakeAssoc function inserts data into an XAssocTable
keyed on an XID.  Data is inserted into the table only once.
Redundant inserts are ignored.	The queue in each associa-
tion bucket is sorted from the lowest XID to the highest
XID.


To obtain data from a given XAssocTable, use XLookUpAssoc.
__
|
char *XLookUpAssoc(display, table, x_id)
      Display *display;
      XAssocTable *table;
      XID x_id;


display   Specifies the connection to the X server.

table	  Specifies the assoc table.

x_id	  Specifies the X resource ID.
|__

The XLookUpAssoc function retrieves the data stored in an
XAssocTable by its XID.  If  an appropriately  matching XID
can be found in the table, XLookUpAssoc returns the data
associated with it.  If the x_id cannot be found in the
table, it returns NULL.


To delete an entry from a given XAssocTable, use XDeleteAs-
soc.







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__
|
XDeleteAssoc(display, table, x_id)
      Display *display;
      XAssocTable *table;
      XID x_id;


display   Specifies the connection to the X server.

table	  Specifies the assoc table.

x_id	  Specifies the X resource ID.
|__

The XDeleteAssoc function deletes an association in an XAs-
socTable keyed on its XID.  Redundant deletes (and deletes
of nonexistent XIDs) are ignored.  Deleting associations in
no way impairs the performance of an XAssocTable.


To free the memory associated with a given XAssocTable, use
XDestroyAssocTable.
__
|
XDestroyAssocTable(table)
      XAssocTable *table;


table	  Specifies the assoc table.
|__



























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			  Glossary



Access control list

     X maintains a list of hosts from which client programs
     can be run.  By default, only programs on the local
     host and hosts specified in an initial list read by the
     server can use the display.  This access control list
     can be changed by clients on the local host.  Some
     server implementations can also implement other autho-
     rization mechanisms in addition to or in place of this
     mechanism.  The action of this mechanism can be condi-
     tional based on the authorization protocol name and
     data received by the server at connection setup.

Active grab

     A grab is active when the pointer or keyboard is actu-
     ally owned by the single grabbing client.

Ancestors

     If W is an inferior of A, then A is an ancestor of W.

Atom

     An atom is a unique ID corresponding to a string name.
     Atoms are used to identify properties, types, and
     selections.

Background

     An InputOutput window can have a background, which is
     defined as a pixmap.  When regions of the window have
     their contents lost or invalidated, the server automat-
     ically tiles those regions with the background.

Backing store

     When a server maintains the contents of a window, the
     pixels saved off-screen are known as a backing store.












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Base font name

     A font name used to select a family of fonts whose mem-
     bers may be encoded in various charsets.  The CharSe-
     tRegistry and CharSetEncoding fields of an XLFD name
     identify the charset of the font.	A base font name may
     be a full XLFD name, with all fourteen '-' delimiters,
     or an abbreviated XLFD name containing only the first
     12 fields of an XLFD name, up to but not including
     CharSetRegistry, with or without the thirteenth '-', or
     a non-XLFD name.  Any XLFD fields may contain wild
     cards.

     When creating an XFontSet, Xlib accepts from the client
     a list of one or more base font names which select one
     or more font families.  They are combined with charset
     names obtained from the encoding of the locale to load
     the fonts required to render text.

Bit gravity

     When a window is resized, the contents of the window
     are not necessarily discarded.  It is possible to
     request that the server relocate the previous contents
     to some region of the window (though no guarantees are
     made).  This attraction of window contents for some
     location of a window is known as bit gravity.

Bit plane

     When a pixmap or window is thought of as a stack of
     bitmaps, each bitmap is called a bit plane or plane.

Bitmap

     A bitmap is a pixmap of depth one.

Border

     An InputOutput window can have a border of equal thick-
     ness on all four sides of the window.  The contents of
     the border are defined by a pixmap, and the server
     automatically maintains the contents of the border.
     Exposure events are never generated for border regions.

Button grabbing

     Buttons on the pointer can be passively grabbed by a
     client.  When the button is pressed, the pointer is
     then actively grabbed by the client.







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Byte order

     For image (pixmap/bitmap) data, the server defines the
     byte order, and clients with different native byte
     ordering must swap bytes as necessary.  For all other
     parts of the protocol, the client defines the byte
     order, and the server swaps bytes as necessary.

Character

     A member of a set of elements used for the organiza-
     tion, control, or representation of text (ISO2022, as
     adapted by XPG3).	Note that in ISO2022 terms, a char-
     acter is not bound to a coded value until it is identi-
     fied as part of a coded character set.

Character glyph

     The abstract graphical symbol for a character.  Charac-
     ter glyphs may or may not map one-to-one to font
     glyphs, and may be context-dependent, varying with the
     adjacent characters.  Multiple characters may map to a
     single character glyph.

Character set

     A collection of characters.

Charset

     An encoding with a uniform, state-independent mapping
     from characters to codepoints.  A coded character set.

     For display in X, there can be a direct mapping from a
     charset to one font, if the width of all characters in
     the charset is either one or two bytes.  A text string
     encoded in an encoding such as Shift-JIS cannot be
     passed directly to the X server, because the text imag-
     ing requests accept only single-width charsets (either
     8 or 16 bits).  Charsets which meet these restrictions
     can serve as ``font charsets''.  Font charsets strictly
     speaking map font indices to font glyphs, not charac-
     ters to character glyphs.

     Note that a single font charset is sometimes used as
     the encoding of a locale, for example, ISO8859-1.

Children

     The children of a window are its first-level subwin-
     dows.






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Class

     Windows can be of different classes or types.  See the
     entries for InputOnly and InputOutput windows for fur-
     ther information about valid window types.

Client

     An application program connects to the window system
     server by some interprocess communication (IPC) path,
     such as a TCP connection or a shared memory buffer.
     This program is referred to as a client of the window
     system server.  More precisely, the client is the IPC
     path itself.  A program with multiple paths open to the
     server is viewed as multiple clients by the protocol.
     Resource lifetimes are controlled by connection life-
     times, not by program lifetimes.

Clipping region

     In a graphics context, a bitmap or list of rectangles
     can be specified to restrict output to a particular
     region of the window.  The image defined by the bitmap
     or rectangles is called a clipping region.

Coded character

     A character bound to a codepoint.

Coded character set

     A set of unambiguous rules that establishes a character
     set and the one-to-one relationship between each char-
     acter of the set and its bit representation.  (ISO2022,
     as adapted by XPG3) A definition of a one-to-one map-
     ping of a set of characters to a set of codepoints.

Codepoint

     The coded representation of a single character in a
     coded character set.

Colormap

     A colormap consists of a set of entries defining color
     values.  The colormap associated with a window is used
     to display the contents of the window; each pixel value
     indexes the colormap to produce an RGB value that
     drives the guns of a monitor.  Depending on hardware
     limitations, one or more colormaps can be installed at
     one time so that windows associated with those maps
     display with true colors.





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Connection

     The IPC path between the server and client program is
     known as a connection.  A client program typically (but
     not necessarily) has one connection to the server over
     which requests and events are sent.

Containment

     A window contains the pointer if the window is viewable
     and the hotspot of the cursor is within a visible
     region of the window or a visible region of one of its
     inferiors.  The border of the window is included as
     part of the window for containment.  The pointer is in
     a window if the window contains the pointer but no
     inferior contains the pointer.

Coordinate system

     The coordinate system has X horizontal and Y vertical,
     with the origin [0, 0] at the upper left.	Coordinates
     are integral and coincide with pixel centers.  Each
     window and pixmap has its own coordinate system.  For a
     window, the origin is inside the border at the inside
     upper-left corner.

Cursor

     A cursor is the visible shape of the pointer on a
     screen.  It consists of a hotspot, a source bitmap, a
     shape bitmap, and a pair of colors.  The cursor defined
     for a window controls the visible appearance when the
     pointer is in that window.

Depth

     The depth of a window or pixmap is the number of bits
     per pixel it has.	The depth of a graphics context is
     the depth of the drawables it can be used in conjunc-
     tion with graphics output.

Device

     Keyboards, mice, tablets, track-balls, button boxes,
     and so on are all collectively known as input devices.
     Pointers can have one or more buttons (the most common
     number is three).	The core protocol only deals with
     two devices: the keyboard and the pointer.









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DirectColor

     DirectColor is a class of colormap in which a pixel
     value is decomposed into three separate subfields for
     indexing.	The first subfield indexes an array to pro-
     duce red intensity values.  The second subfield indexes
     a second array to produce blue intensity values.  The
     third subfield indexes a third array to produce green
     intensity values.	The RGB (red, green, and blue) val-
     ues in the colormap entry can be changed dynamically.

Display

     A server, together with its screens and input devices,
     is called a display.  The Xlib Display structure con-
     tains all information about the particular display and
     its screens as well as the state that Xlib needs to
     communicate with the display over a particular connec-
     tion.

Drawable

     Both windows and pixmaps can be used as sources and
     destinations in graphics operations.  These windows and
     pixmaps are collectively known as drawables.  However,
     an InputOnly window cannot be used as a source or des-
     tination in a graphics operation.

Encoding

     A set of unambiguous rules that establishes a character
     set and a relationship between the characters and their
     representations.  The character set does not have to be
     fixed to a finite pre-defined set of characters.  The
     representations do not have to be of uniform length.
     Examples are an ISO2022 graphic set, a state-indepen-
     dent or state-dependent combination of graphic sets,
     possibly including control sets, the X Compound Text
     encoding, and the UTF-8 ISO10646/Unicode encoding.

     In X, encodings are identified by a string which
     appears as: the CharSetRegistry and CharSetEncoding
     components of an XLFD name; the name of a charset of
     the locale for which a font could not be found; or an
     atom which identifies the encoding of a text property
     or which names an encoding for a text selection target
     type.  Encoding names should be composed of characters
     from the X Portable Character Set.









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Escapement

     The escapement of a string is the distance in pixels in
     the primary draw direction from the drawing origin to
     the origin of the next character (that is, the one fol-
     lowing the given string) to be drawn.

Event

     Clients are informed of information asynchronously by
     means of events.  These events can be either asyn-
     chronously generated from devices or generated as side
     effects of client requests.  Events are grouped into
     types.  The server never sends an event to a client
     unless the client has specifically asked to be informed
     of that type of event.  However, clients can force
     events to be sent to other clients.  Events are typi-
     cally reported relative to a window.

Event mask

     Events are requested relative to a window.  The set of
     event types a client requests relative to a window is
     described by using an event mask.

Event propagation

     Device-related events propagate from the source window
     to ancestor windows until some client has expressed
     interest in handling that type of event or until the
     event is discarded explicitly.

Event source

     The deepest viewable window that the pointer is in is
     called the source of a device-related event.

Event synchronization

     There are certain race conditions possible when demul-
     tiplexing device events to clients (in particular,
     deciding where pointer and keyboard events should be
     sent when in the middle of window management opera-
     tions).  The event synchronization mechanism allows
     synchronous processing of device events.

Exposure event

     Servers do not guarantee to preserve the contents of
     windows when windows are obscured or reconfigured.
     Exposure events are sent to clients to inform them when
     contents of regions of windows have been lost.





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Extension

     Named extensions to the core protocol can be defined to
     extend the system.  Extensions to output requests,
     resources, and event types are all possible and
     expected.

Font

     A font is an array of glyphs (typically characters).
     The protocol does no translation or interpretation of
     character sets.  The client simply indicates values
     used to index the glyph array.  A font contains addi-
     tional metric information to determine interglyph and
     interline spacing.

Font glyph

     The abstract graphical symbol for an index into a font.

Frozen events

     Clients can freeze event processing during keyboard and
     pointer grabs.

GC

     GC is an abbreviation for graphics context.  See Graph-
     ics context.

Glyph

     An identified abstract graphical symbol independent of
     any actual image.	(ISO/IEC/DIS 9541-1) An abstract
     visual representation of a graphic character, not bound
     to a codepoint.

Glyph image

     An image of a glyph, as obtained from a glyph represen-
     tation displayed on a presentation surface.
     (ISO/IEC/DIS 9541-1)

Grab

     Keyboard keys, the keyboard, pointer buttons, the
     pointer, and the server can be grabbed for exclusive
     use by a client.  In general, these facilities are not
     intended to be used by normal applications but are
     intended for various input and window managers to
     implement various styles of user interfaces.






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Graphics context

     Various information for graphics output is stored in a
     graphics context (GC), such as foreground pixel, back-
     ground pixel, line width, clipping region, and so on.
     A graphics context can only be used with drawables that
     have the same root and the same depth as the graphics
     context.

Gravity

     The contents of windows and windows themselves have a
     gravity, which determines how the contents move when a
     window is resized.  See Bit gravity and Window gravity.

GrayScale

     GrayScale can be viewed as a degenerate case of Pseudo-
     Color, in which the red, green, and blue values in any
     given colormap entry are equal and thus, produce shades
     of gray.  The gray values can be changed dynamically.

Host Portable Character Encoding

     The encoding of the X Portable Character Set on the
     host.  The encoding itself is not defined by this stan-
     dard, but the encoding must be the same in all locales
     supported by Xlib on the host.  If a string is said to
     be in the Host Portable Character Encoding, then it
     only contains characters from the X Portable Character
     Set, in the host encoding.

Hotspot

     A cursor has an associated hotspot, which defines the
     point in the cursor corresponding to the coordinates
     reported for the pointer.

Identifier

     An identifier is a unique value associated with a
     resource that clients use to name that resource.  The
     identifier can be used over any connection to name the
     resource.

Inferiors

     The inferiors of a window are all of the subwindows
     nested below it: the children, the children's children,
     and so on.







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Input focus

     The input focus is usually a window defining the scope
     for processing of keyboard input.	If a generated key-
     board event usually would be reported to this window or
     one of its inferiors, the event is reported as usual.
     Otherwise, the event is reported with respect to the
     focus window.  The input focus also can be set such
     that all keyboard events are discarded and such that
     the focus window is dynamically taken to be the root
     window of whatever screen the pointer is on at each
     keyboard event.

Input manager

     Control over keyboard input is typically provided by an
     input manager client, which usually is part of a window
     manager.

InputOnly window

     An InputOnly window is a window that cannot be used for
     graphics requests.  InputOnly windows are invisible and
     are used to control such things as cursors, input event
     generation, and grabbing.	InputOnly windows cannot
     have InputOutput windows as inferiors.

InputOutput window

     An InputOutput window is the normal kind of window that
     is used for both input and output.  InputOutput windows
     can have both InputOutput and InputOnly windows as
     inferiors.

Internationalization

     The process of making software adaptable to the
     requirements of different native languages, local cus-
     toms, and character string encodings.  Making a com-
     puter program adaptable to different locales without
     program source modifications or recompilation.

ISO2022

     ISO standard for code extension techniques for 7-bit
     and 8-bit coded character sets.

Key grabbing

     Keys on the keyboard can be passively grabbed by a
     client.  When the key is pressed, the keyboard is then
     actively grabbed by the client.





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Keyboard grabbing

     A client can actively grab control of the keyboard, and
     key events will be sent to that client rather than the
     client the events would normally have been sent to.

Keysym

     An encoding of a symbol on a keycap on a keyboard.

Latin-1

     The coded character set defined by the ISO8859-1 stan-
     dard.

Latin Portable Character Encoding

     The encoding of the X Portable Character Set using the
     Latin-1 codepoints plus ASCII control characters.	If a
     string is said to be in the Latin Portable Character
     Encoding, then it only contains characters from the X
     Portable Character Set, not all of Latin-1.

Locale

     The international environment of a computer program
     defining the ``localized'' behavior of that program at
     run-time.	This information can be established from one
     or more sets of localization data.  ANSI C defines
     locale-specific processing by C system library calls.
     See ANSI C and the X/Open Portability Guide specifica-
     tions for more details.  In this specification, on
     implementations that conform to the ANSI C library, the
     ``current locale'' is the current setting of the
     LC_CTYPE setlocale category.  Associated with each
     locale is a text encoding.  When text is processed in
     the context of a locale, the text must be in the encod-
     ing of the locale.  The current locale affects Xlib in
     its:

     o	  Encoding and processing of input method text

     o	  Encoding of resource files and values

     o	  Encoding and imaging of text strings

     o	  Encoding and decoding for inter-client text commu-
	  nication









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Locale name

     The identifier used to select the desired locale for
     the host C library and X library functions.  On ANSI C
     library compliant systems, the locale argument to the
     setlocale function.

Localization

     The process of establishing information within a com-
     puter system specific to the operation of particular
     native languages, local customs and coded character
     sets.  (XPG3)

Mapped

     A window is said to be mapped if a map call has been
     performed on it.  Unmapped windows and their inferiors
     are never viewable or visible.

Modifier keys

     Shift, Control, Meta, Super, Hyper, Alt, Compose,
     Apple, CapsLock, ShiftLock, and similar keys are called
     modifier keys.

Monochrome

     Monochrome is a special case of StaticGray in which
     there are only two colormap entries.

Multibyte

     A character whose codepoint is stored in more than one
     byte; any encoding which can contain multibyte charac-
     ters; text in a multibyte encoding.  The ``char *''
     null-terminated string datatype in ANSI C.  Note that
     references in this document to multibyte strings imply
     only that the strings may contain multibyte characters.

Obscure

     A window is obscured if some other window obscures it.
     A window can be partially obscured and so still have
     visible regions.  Window A obscures window B if both
     are viewable InputOutput windows, if A is higher in the
     global stacking order, and if the rectangle defined by
     the outside edges of A intersects the rectangle defined
     by the outside edges of B.  Note the distinction
     between obscures and occludes.  Also note that window
     borders are included in the calculation.






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Occlude

     A window is occluded if some other window occludes it.
     Window A occludes window B if both are mapped, if A is
     higher in the global stacking order, and if the rectan-
     gle defined by the outside edges of A intersects the
     rectangle defined by the outside edges of B.  Note the
     distinction between occludes and obscures.  Also note
     that window borders are included in the calculation and
     that InputOnly windows never obscure other windows but
     can occlude other windows.

Padding

     Some padding bytes are inserted in the data stream to
     maintain alignment of the protocol requests on natural
     boundaries.  This increases ease of portability to some
     machine architectures.

Parent window

     If C is a child of P, then P is the parent of C.

Passive grab

     Grabbing a key or button is a passive grab.  The grab
     activates when the key or button is actually pressed.

Pixel value

     A pixel is an N-bit value, where N is the number of bit
     planes used in a particular window or pixmap (that is,
     is the depth of the window or pixmap).  A pixel in a
     window indexes a colormap to derive an actual color to
     be displayed.

Pixmap

     A pixmap is a three-dimensional array of bits.  A
     pixmap is normally thought of as a two-dimensional
     array of pixels, where each pixel can be a value from 0
     to 2N-1, and where N is the depth (z axis) of the
     pixmap.  A pixmap can also be thought of as a stack of
     N bitmaps.  A pixmap can only be used on the screen
     that it was created in.

Plane

     When a pixmap or window is thought of as a stack of
     bitmaps, each bitmap is called a plane or bit plane.







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Plane mask

     Graphics operations can be restricted to only affect a
     subset of bit planes of a destination.  A plane mask is
     a bit mask describing which planes are to be modified.
     The plane mask is stored in a graphics context.

Pointer

     The pointer is the pointing device currently attached
     to the cursor and tracked on the screens.

Pointer grabbing

     A client can actively grab control of the pointer.
     Then button and motion events will be sent to that
     client rather than the client the events would normally
     have been sent to.

Pointing device

     A pointing device is typically a mouse, tablet, or some
     other device with effective dimensional motion.  The
     core protocol defines only one visible cursor, which
     tracks whatever pointing device is attached as the
     pointer.

POSIX

     Portable Operating System Interface, ISO/IEC 9945-1
     (IEEE Std 1003.1).

POSIX Portable Filename Character Set

     The set of 65 characters which can be used in naming
     files on a POSIX-compliant host that are correctly pro-
     cessed in all locales.  The set is:


     a..z A..Z 0..9 ._-


Property

     Windows can have associated properties that consist of
     a name, a type, a data format, and some data.  The pro-
     tocol places no interpretation on properties.  They are
     intended as a general-purpose naming mechanism for
     clients.  For example, clients might use properties to
     share information such as resize hints, program names,
     and icon formats with a window manager.






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Property list

     The property list of a window is the list of properties
     that have been defined for the window.

PseudoColor

     PseudoColor is a class of colormap in which a pixel
     value indexes the colormap entry to produce an indepen-
     dent RGB value; that is, the colormap is viewed as an
     array of triples (RGB values).  The RGB values can be
     changed dynamically.

Rectangle

     A rectangle specified by [x,y,w,h] has an infinitely
     thin outline path with corners at [x,y], [x+w,y],
     [x+w,y+h], and [x, y+h].  When a rectangle is filled,
     the lower-right edges are not drawn.  For example, if
     w=h=0, nothing would be drawn.  For w=h=1, a single
     pixel would be drawn.

Redirecting control

     Window managers (or client programs) may enforce window
     layout policy in various ways.  When a client attempts
     to change the size or position of a window, the opera-
     tion may be redirected to a specified client rather
     than the operation actually being performed.

Reply

     Information requested by a client program using the X
     protocol is sent back to the client with a reply.	Both
     events and replies are multiplexed on the same connec-
     tion.  Most requests do not generate replies, but some
     requests generate multiple replies.

Request

     A command to the server is called a request.  It is a
     single block of data sent over a connection.

Resource

     Windows, pixmaps, cursors, fonts, graphics contexts,
     and colormaps are known as resources.  They all have
     unique identifiers associated with them for naming pur-
     poses.  The lifetime of a resource usually is bounded
     by the lifetime of the connection over which the
     resource was created.






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RGB values

     RGB values are the red, green, and blue intensity val-
     ues that are used to define a color.  These values are
     always represented as 16-bit, unsigned numbers, with 0
     the minimum intensity and 65535 the maximum intensity.
     The X server scales these values to match the display
     hardware.

Root

     The root of a pixmap or graphics context is the same as
     the root of whatever drawable was used when the pixmap
     or GC was created.  The root of a window is the root
     window under which the window was created.

Root window

     Each screen has a root window covering it.  The root
     window cannot be reconfigured or unmapped, but other-
     wise it acts as a full-fledged window.  A root window
     has no parent.

Save set

     The save set of a client is a list of other clients'
     windows that, if they are inferiors of one of the
     client's windows at connection close, should not be
     destroyed and that should be remapped if currently
     unmapped.	Save sets are typically used by window man-
     agers to avoid lost windows if the manager should ter-
     minate abnormally.

Scanline

     A scanline is a list of pixel or bit values viewed as a
     horizontal row (all values having the same y coordi-
     nate) of an image, with the values ordered by increas-
     ing the x coordinate.

Scanline order

     An image represented in scanline order contains scan-
     lines ordered by increasing the y coordinate.

Screen

     A server can provide several independent screens, which
     typically have physically independent monitors.  This
     would be the expected configuration when there is only
     a single keyboard and pointer shared among the screens.
     A Screen structure contains the information about that
     screen and is linked to the Display structure.




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Selection

     A selection can be thought of as an indirect property
     with dynamic type.  That is, rather than having the
     property stored in the X server, it is maintained by
     some client (the owner).  A selection is global and is
     thought of as belonging to the user and being main-
     tained by clients, rather than being private to a par-
     ticular window subhierarchy or a particular set of
     clients.  When a client asks for the contents of a
     selection, it specifies a selection target type, which
     can be used to control the transmitted representation
     of the contents.  For example, if the selection is
     ``the last thing the user clicked on,'' and that is
     currently an image, then the target type might specify
     whether the contents of the image should be sent in XY
     format or Z format.

     The target type can also be used to control the class
     of contents transmitted; for example, asking for the
     ``looks'' (fonts, line spacing, indentation, and so
     forth) of a paragraph selection, rather than the text
     of the paragraph.	The target type can also be used for
     other purposes.  The protocol does not constrain the
     semantics.

Server

     The server, which is also referred to as the X server,
     provides the basic windowing mechanism.  It handles IPC
     connections from clients, multiplexes graphics requests
     onto the screens, and demultiplexes input back to the
     appropriate clients.

Server grabbing

     The server can be grabbed by a single client for exclu-
     sive use.	This prevents processing of any requests
     from other client connections until the grab is com-
     pleted.  This is typically only a transient state for
     such things as rubber-banding, pop-up menus, or execut-
     ing requests indivisibly.

Shift sequence

     ISO2022 defines control characters and escape sequences
     which temporarily (single shift) or permanently (lock-
     ing shift) cause a different character set to be in
     effect (``invoking'' a character set).








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Sibling

     Children of the same parent window are known as sibling
     windows.

Stacking order

     Sibling windows, similar to sheets of paper on a desk,
     can stack on top of each other.  Windows above both
     obscure and occlude lower windows.  The relationship
     between sibling windows is known as the stacking order.

State-dependent encoding

     An encoding in which an invocation of a charset can
     apply to multiple characters in sequence.	A state-
     dependent encoding begins in an ``initial state'' and
     enters other ``shift states'' when specific ``shift
     sequences'' are encountered in the byte sequence.	In
     ISO2022 terms, this means use of locking shifts, not
     single shifts.

State-independent encoding

     Any encoding in which the invocations of the charsets
     are fixed, or span only a single character.  In ISO2022
     terms, this means use of at most single shifts, not
     locking shifts.

StaticColor

     StaticColor can be viewed as a degenerate case of Pseu-
     doColor in which the RGB values are predefined and
     read-only.

StaticGray

     StaticGray can be viewed as a degenerate case of
     GrayScale in which the gray values are predefined and
     read-only.  The values are typically linear or near-
     linear increasing ramps.

Status

     Many Xlib functions return a success status.  If the
     function does not succeed, however, its arguments are
     not disturbed.

Stipple

     A stipple pattern is a bitmap that is used to tile a
     region to serve as an additional clip mask for a fill
     operation with the foreground color.




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STRING encoding

     Latin-1, plus tab and newline.

String Equivalence

     Two ISO Latin-1 STRING8 values are considered equal if
     they are the same length and if corresponding bytes are
     either equal or are equivalent as follows:  decimal
     values 65 to 90 inclusive (characters ``A'' to ``Z'')
     are pairwise equivalent to decimal values 97 to 122
     inclusive (characters ``a'' to ``z''), decimal values
     192 to 214 inclusive (characters ``A grave'' to ``O
     diaeresis'') are pairwise equivalent to decimal values
     224 to 246 inclusive (characters ``a grave'' to ``o
     diaeresis''), and decimal values 216 to 222 inclusive
     (characters ``O oblique'' to ``THORN'') are pairwise
     equivalent to decimal values 246 to 254 inclusive
     (characters ``o oblique'' to ``thorn'').

Tile

     A pixmap can be replicated in two dimensions to tile a
     region.  The pixmap itself is also known as a tile.

Timestamp

     A timestamp is a time value expressed in milliseconds.
     It is typically the time since the last server reset.
     Timestamp values wrap around (after about 49.7 days).
     The server, given its current time is represented by
     timestamp T, always interprets timestamps from clients
     by treating half of the timestamp space as being ear-
     lier in time than T and half of the timestamp space as
     being later in time than T.  One timestamp value, rep-
     resented by the constant CurrentTime, is never gener-
     ated by the server.  This value is reserved for use in
     requests to represent the current server time.

TrueColor

     TrueColor can be viewed as a degenerate case of Direct-
     Color in which the subfields in the pixel value
     directly encode the corresponding RGB values.  That is,
     the colormap has predefined read-only RGB values.	The
     values are typically linear or near-linear increasing
     ramps.










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Type

     A type is an arbitrary atom used to identify the inter-
     pretation of property data.  Types are completely unin-
     terpreted by the server.  They are solely for the bene-
     fit of clients.  X predefines type atoms for many fre-
     quently used types, and clients also can define new
     types.

Viewable

     A window is viewable if it and all of its ancestors are
     mapped.  This does not imply that any portion of the
     window is actually visible.  Graphics requests can be
     performed on a window when it is not viewable, but out-
     put will not be retained unless the server is maintain-
     ing backing store.

Visible

     A region of a window is visible if someone looking at
     the screen can actually see it; that is, the window is
     viewable and the region is not occluded by any other
     window.

Whitespace

     Any spacing character.  On implementations that conform
     to the ANSI C library, whitespace is any character for
     which isspace returns true.

Window gravity

     When windows are resized, subwindows may be reposi-
     tioned automatically relative to some position in the
     window.  This attraction of a subwindow to some part of
     its parent is known as window gravity.

Window manager

     Manipulation of windows on the screen and much of the
     user interface (policy) is typically provided by a win-
     dow manager client.














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X Portable Character Set

     A basic set of 97 characters which are assumed to exist
     in all locales supported by Xlib.	This set contains
     the following characters:


a..z A..Z 0..9 !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~ <space>,
<tab>, and <newline>


     This is the left/lower half (also called the G0 set) of
     the graphic character set of ISO8859-1 plus <space>,
     <tab>, and <newline>.  It is also the set of graphic
     characters in 7-bit ASCII plus the same three control
     characters.  The actual encoding of these characters on
     the host is system dependent; see the Host Portable
     Character Encoding.

XLFD

     The X Logical Font Description Conventions that define
     a standard syntax for structured font names.

XY format

     The data for a pixmap is said to be in XY format if it
     is organized as a set of bitmaps representing individ-
     ual bit planes with the planes appearing from most-sig-
     nificant to least-significant bit order.

Z format

     The data for a pixmap is said to be in Z format if it
     is organized as a set of pixel values in scanline
     order.

References

ANSI Programming Language - C: ANSI X3.159-1989, December
14, 1989.

Draft Proposed Multibyte Extension of ANSI C, Draft 1.1,
November 30, 1989, SC22/C WG/SWG IPSJ/ITSCJ Japan.

ISO2022: Information processing - ISO 7-bit and 8-bit coded
character sets - Code extension techniques.

ISO8859-1: Information processing - 8-bit single-byte coded
graphic character sets - Part 1: Latin alphabet No. 1.

POSIX: Information Technology - Portable Operating System
Interface (POSIX) - Part 1: System Application Program
Interface (API) [C Language], ISO/IEC 9945-1.



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Text of ISO/IEC/DIS 9541-1, Information Processing - Font
Information Interchange - Part 1:  Architecture.

X/Open Portability Guide, Issue 3, December 1988 (XPG3),
X/Open Company, Ltd, Prentice-Hall, Inc. 1989. ISBN
0-13-685835-8.	(See especially Volume 3:  XSI Supplementary
Definitions.)


















































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		     Table of Contents


Table of Contents  . . . . . . . . . . . . . . . . . . .  ii
Acknowledgments  . . . . . . . . . . . . . . . . . . . . iii
Chapter 1: Introduction to Xlib  . . . . . . . . . . . .   1
1.1. Overview of the X Window System . . . . . . . . . .   2
1.2. Errors  . . . . . . . . . . . . . . . . . . . . . .   4
1.3. Standard Header Files . . . . . . . . . . . . . . .   4
1.4. Generic Values and Types  . . . . . . . . . . . . .   6
1.5. Naming and Argument Conventions within Xlib . . . .   7
1.6. Programming Considerations  . . . . . . . . . . . .   8
1.7. Character Sets and Encodings  . . . . . . . . . . .   8
1.8. Formatting Conventions  . . . . . . . . . . . . . .   9
Chapter 2: Display Functions . . . . . . . . . . . . . .  11
2.1. Opening the Display . . . . . . . . . . . . . . . .  11
2.2. Obtaining Information about the Display, Image
Formats, or Screens  . . . . . . . . . . . . . . . . . .  13
2.2.1. Display Macros  . . . . . . . . . . . . . . . . .  13
2.2.2. Image Format Functions and Macros . . . . . . . .  23
2.2.3. Screen Information Macros . . . . . . . . . . . .  27
2.3. Generating a NoOperation Protocol Request . . . . .  33
2.4. Freeing Client-Created Data . . . . . . . . . . . .  34
2.5. Closing the Display . . . . . . . . . . . . . . . .  34
2.6. Using X Server Connection Close Operations  . . . .  35
2.7. Using Xlib with Threads . . . . . . . . . . . . . .  37
2.8. Using Internal Connections  . . . . . . . . . . . .  38
Chapter 3: Window Functions  . . . . . . . . . . . . . .  42
3.1. Visual Types  . . . . . . . . . . . . . . . . . . .  42
3.2. Window Attributes . . . . . . . . . . . . . . . . .  44
3.2.1. Background Attribute  . . . . . . . . . . . . . .  48
3.2.2. Border Attribute  . . . . . . . . . . . . . . . .  49
3.2.3. Gravity Attributes  . . . . . . . . . . . . . . .  50
3.2.4. Backing Store Attribute . . . . . . . . . . . . .  51
3.2.5. Save Under Flag . . . . . . . . . . . . . . . . .  52
3.2.6. Backing Planes and Backing Pixel Attributes
 . . . . . . . . . . . . . . . . . . . . . . . . . . . .  52
3.2.7. Event Mask and Do Not Propagate Mask
Attributes . . . . . . . . . . . . . . . . . . . . . . .  53
3.2.8. Override Redirect Flag  . . . . . . . . . . . . .  53
3.2.9. Colormap Attribute  . . . . . . . . . . . . . . .  53
3.2.10. Cursor Attribute . . . . . . . . . . . . . . . .  54
3.3. Creating Windows  . . . . . . . . . . . . . . . . .  54
3.4. Destroying Windows  . . . . . . . . . . . . . . . .  59
3.5. Mapping Windows . . . . . . . . . . . . . . . . . .  60
3.6. Unmapping Windows . . . . . . . . . . . . . . . . .  62
3.7. Configuring Windows . . . . . . . . . . . . . . . .  63
3.8. Changing Window Stacking Order  . . . . . . . . . .  70
3.9. Changing Window Attributes  . . . . . . . . . . . .  74
Chapter 4: Window Information Functions  . . . . . . . .  81
4.1. Obtaining Window Information  . . . . . . . . . . .  81
4.2. Translating Screen Coordinates  . . . . . . . . . .  87
4.3. Properties and Atoms  . . . . . . . . . . . . . . .  89












4.4. Obtaining and Changing Window Properties  . . . . .  94
4.5. Selections  . . . . . . . . . . . . . . . . . . . . 101
Chapter 5: Pixmap and Cursor Functions . . . . . . . . . 105
5.1. Creating and Freeing Pixmaps  . . . . . . . . . . . 105
5.2. Creating, Recoloring, and Freeing Cursors . . . . . 106
Chapter 6: Color Management Functions  . . . . . . . . . 112
6.1. Color Structures  . . . . . . . . . . . . . . . . . 113
6.2. Color Strings . . . . . . . . . . . . . . . . . . . 117
6.2.1. RGB Device String Specification . . . . . . . . . 118
6.2.2. RGB Intensity String Specification  . . . . . . . 119
6.2.3. Device-Independent String Specifications  . . . . 119
6.3. Color Conversion Contexts and Gamut Mapping . . . . 120
6.4. Creating, Copying, and Destroying Colormaps . . . . 121
6.5. Mapping Color Names to Values . . . . . . . . . . . 123
6.6. Allocating and Freeing Color Cells  . . . . . . . . 127
6.7. Modifying and Querying Colormap Cells . . . . . . . 135
6.8. Color Conversion Context Functions  . . . . . . . . 142
6.8.1. Getting and Setting the Color Conversion Con-
text of a Colormap . . . . . . . . . . . . . . . . . . . 143
6.8.2. Obtaining the Default Color Conversion Con-
text . . . . . . . . . . . . . . . . . . . . . . . . . . 144
6.8.3. Color Conversion Context Macros . . . . . . . . . 144
6.8.4. Modifying Attributes of a Color Conversion
Context  . . . . . . . . . . . . . . . . . . . . . . . . 146
6.8.5. Creating and Freeing a Color Conversion Con-
text . . . . . . . . . . . . . . . . . . . . . . . . . . 148
6.9. Converting between Color Spaces . . . . . . . . . . 150
6.10. Callback Functions . . . . . . . . . . . . . . . . 151
6.10.1. Prototype Gamut Compression Procedure  . . . . . 152
6.10.2. Supplied Gamut Compression Procedures  . . . . . 154
6.10.3. Prototype White Point Adjustment Procedure
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
6.10.4. Supplied White Point Adjustment Procedures
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
6.11. Gamut Querying Functions . . . . . . . . . . . . . 159
6.11.1. Red, Green, and Blue Queries . . . . . . . . . . 160
6.11.2. CIELab Queries . . . . . . . . . . . . . . . . . 163
6.11.3. CIELuv Queries . . . . . . . . . . . . . . . . . 167
6.11.4. TekHVC Queries . . . . . . . . . . . . . . . . . 171
6.12. Color Management Extensions  . . . . . . . . . . . 176
6.12.1. Color Spaces . . . . . . . . . . . . . . . . . . 177
6.12.2. Adding Device-Independent Color Spaces . . . . . 177
6.12.3. Querying Color Space Format and Prefix . . . . . 178
6.12.4. Creating Additional Color Spaces . . . . . . . . 178
6.12.5. Parse String Callback  . . . . . . . . . . . . . 180
6.12.6. Color Specification Conversion Callback  . . . . 180
6.12.7. Function Sets  . . . . . . . . . . . . . . . . . 183
6.12.8. Adding Function Sets . . . . . . . . . . . . . . 183
6.12.9. Creating Additional Function Sets  . . . . . . . 184
Chapter 7: Graphics Context Functions  . . . . . . . . . 187
7.1. Manipulating Graphics Context/State . . . . . . . . 187
7.2. Using Graphics Context Convenience Routines . . . . 201
7.2.1. Setting the Foreground, Background, Function,
or Plane Mask  . . . . . . . . . . . . . . . . . . . . . 201












7.2.2. Setting the Line Attributes and Dashes  . . . . . 204
7.2.3. Setting the Fill Style and Fill Rule  . . . . . . 207
7.2.4. Setting the Fill Tile and Stipple . . . . . . . . 207
7.2.5. Setting the Current Font  . . . . . . . . . . . . 212
7.2.6. Setting the Clip Region . . . . . . . . . . . . . 212
7.2.7. Setting the Arc Mode, Subwindow Mode, and
Graphics Exposure  . . . . . . . . . . . . . . . . . . . 215
Chapter 8: Graphics Functions  . . . . . . . . . . . . . 217
8.1. Clearing Areas  . . . . . . . . . . . . . . . . . . 217
8.2. Copying Areas . . . . . . . . . . . . . . . . . . . 219
8.3. Drawing Points, Lines, Rectangles, and Arcs . . . . 222
8.3.1. Drawing Single and Multiple Points  . . . . . . . 223
8.3.2. Drawing Single and Multiple Lines . . . . . . . . 225
8.3.3. Drawing Single and Multiple Rectangles  . . . . . 227
8.3.4. Drawing Single and Multiple Arcs  . . . . . . . . 229
8.4. Filling Areas . . . . . . . . . . . . . . . . . . . 232
8.4.1. Filling Single and Multiple Rectangles  . . . . . 233
8.4.2. Filling a Single Polygon  . . . . . . . . . . . . 234
8.4.3. Filling Single and Multiple Arcs  . . . . . . . . 236
8.5. Font Metrics  . . . . . . . . . . . . . . . . . . . 237
8.5.1. Loading and Freeing Fonts . . . . . . . . . . . . 242
8.5.2. Obtaining and Freeing Font Names and Informa-
tion . . . . . . . . . . . . . . . . . . . . . . . . . . 246
8.5.3. Computing Character String Sizes  . . . . . . . . 248
8.5.4. Computing Logical Extents . . . . . . . . . . . . 249
8.5.5. Querying Character String Sizes . . . . . . . . . 252
8.6. Drawing Text  . . . . . . . . . . . . . . . . . . . 254
8.6.1. Drawing Complex Text  . . . . . . . . . . . . . . 255
8.6.2. Drawing Text Characters . . . . . . . . . . . . . 257
8.6.3. Drawing Image Text Characters . . . . . . . . . . 258
8.7. Transferring Images between Client and Server
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
Chapter 9: Window and Session Manager Functions  . . . . 269
9.1. Changing the Parent of a Window . . . . . . . . . . 269
9.2. Controlling the Lifetime of a Window  . . . . . . . 271
9.3. Managing Installed Colormaps  . . . . . . . . . . . 272
9.4. Setting and Retrieving the Font Search Path . . . . 275
9.5. Grabbing the Server . . . . . . . . . . . . . . . . 276
9.6. Killing Clients . . . . . . . . . . . . . . . . . . 277
9.7. Controlling the Screen Saver  . . . . . . . . . . . 278
9.8. Controlling Host Access . . . . . . . . . . . . . . 281
9.8.1. Adding, Getting, or Removing Hosts  . . . . . . . 281
9.8.2. Changing, Enabling, or Disabling Access Con-
trol . . . . . . . . . . . . . . . . . . . . . . . . . . 284
Chapter 10: Events . . . . . . . . . . . . . . . . . . . 287
10.1. Event Types  . . . . . . . . . . . . . . . . . . . 287
10.2. Event Structures . . . . . . . . . . . . . . . . . 288
10.3. Event Masks  . . . . . . . . . . . . . . . . . . . 291
10.4. Event Processing Overview  . . . . . . . . . . . . 292
10.5. Keyboard and Pointer Events  . . . . . . . . . . . 294
10.5.1. Pointer Button Events  . . . . . . . . . . . . . 294
10.5.2. Keyboard and Pointer Events  . . . . . . . . . . 295
10.6. Window Entry/Exit Events . . . . . . . . . . . . . 299
10.6.1. Normal Entry/Exit Events . . . . . . . . . . . . 301












10.6.2. Grab and Ungrab Entry/Exit Events  . . . . . . . 303
10.7. Input Focus Events . . . . . . . . . . . . . . . . 304
10.7.1. Normal Focus Events and Focus Events While
Grabbed  . . . . . . . . . . . . . . . . . . . . . . . . 305
10.7.2. Focus Events Generated by Grabs  . . . . . . . . 309
10.8. Key Map State Notification Events  . . . . . . . . 309
10.9. Exposure Events  . . . . . . . . . . . . . . . . . 310
10.9.1. Expose Events  . . . . . . . . . . . . . . . . . 310
10.9.2. GraphicsExpose and NoExpose Events . . . . . . . 311
10.10. Window State Change Events  . . . . . . . . . . . 313
10.10.1. CirculateNotify Events  . . . . . . . . . . . . 313
10.10.2. ConfigureNotify Events  . . . . . . . . . . . . 314
10.10.3. CreateNotify Events . . . . . . . . . . . . . . 315
10.10.4. DestroyNotify Events  . . . . . . . . . . . . . 316
10.10.5. GravityNotify Events  . . . . . . . . . . . . . 317
10.10.6. MapNotify Events  . . . . . . . . . . . . . . . 318
10.10.7. MappingNotify Events  . . . . . . . . . . . . . 318
10.10.8. ReparentNotify Events . . . . . . . . . . . . . 319
10.10.9. UnmapNotify Events  . . . . . . . . . . . . . . 320
10.10.10. VisibilityNotify Events  . . . . . . . . . . . 321
10.11. Structure Control Events  . . . . . . . . . . . . 322
10.11.1. CirculateRequest Events . . . . . . . . . . . . 323
10.11.2. ConfigureRequest Events . . . . . . . . . . . . 323
10.11.3. MapRequest Events . . . . . . . . . . . . . . . 324
10.11.4. ResizeRequest Events  . . . . . . . . . . . . . 325
10.12. Colormap State Change Events  . . . . . . . . . . 326
10.13. Client Communication Events . . . . . . . . . . . 327
10.13.1. ClientMessage Events  . . . . . . . . . . . . . 327
10.13.2. PropertyNotify Events . . . . . . . . . . . . . 328
10.13.3. SelectionClear Events . . . . . . . . . . . . . 328
10.13.4. SelectionRequest Events . . . . . . . . . . . . 329
10.13.5. SelectionNotify Events  . . . . . . . . . . . . 330
Chapter 11: Event Handling Functions . . . . . . . . . . 332
11.1. Selecting Events . . . . . . . . . . . . . . . . . 332
11.2. Handling the Output Buffer . . . . . . . . . . . . 333
11.3. Event Queue Management . . . . . . . . . . . . . . 335
11.4. Manipulating the Event Queue . . . . . . . . . . . 336
11.4.1. Returning the Next Event . . . . . . . . . . . . 336
11.4.2. Selecting Events Using a Predicate Procedure
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
11.4.3. Selecting Events Using a Window or Event
Mask . . . . . . . . . . . . . . . . . . . . . . . . . . 340
11.5. Putting an Event Back into the Queue . . . . . . . 345
11.6. Sending Events to Other Applications . . . . . . . 345
11.7. Getting Pointer Motion History . . . . . . . . . . 347
11.8. Handling Protocol Errors . . . . . . . . . . . . . 349
11.8.1. Enabling or Disabling Synchronization  . . . . . 349
11.8.2. Using the Default Error Handlers . . . . . . . . 350
Chapter 12: Input Device Functions . . . . . . . . . . . 356
12.1. Pointer Grabbing . . . . . . . . . . . . . . . . . 356
12.2. Keyboard Grabbing  . . . . . . . . . . . . . . . . 364
12.3. Resuming Event Processing  . . . . . . . . . . . . 369
12.4. Moving the Pointer . . . . . . . . . . . . . . . . 372
12.5. Controlling Input Focus  . . . . . . . . . . . . . 373












12.6. Manipulating the Keyboard and Pointer Settings
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375
12.7. Manipulating the Keyboard Encoding . . . . . . . . 383
Chapter 13: Locales and Internationalized Text Func-
tions  . . . . . . . . . . . . . . . . . . . . . . . . . 393
13.1. X Locale Management  . . . . . . . . . . . . . . . 394
13.2. Locale and Modifier Dependencies . . . . . . . . . 396
13.3. Variable Argument Lists  . . . . . . . . . . . . . 398
13.4. Output Methods . . . . . . . . . . . . . . . . . . 399
13.4.1. Output Method Overview . . . . . . . . . . . . . 399
13.4.2. Output Method Functions  . . . . . . . . . . . . 400
13.4.3. X Output Method Values . . . . . . . . . . . . . 403
13.4.3.1. Required Char Set  . . . . . . . . . . . . . . 404
N Query Orientation  . . . . . . . . . . . . . . . . . . 404
13.4.3.3. Directional Dependent Drawing  . . . . . . . . 405
13.4.3.4. Context Dependent Drawing  . . . . . . . . . . 406
13.4.4. Output Context Functions . . . . . . . . . . . . 406
13.4.5. Output Context Values  . . . . . . . . . . . . . 409
13.4.5.1. Base Font Name . . . . . . . . . . . . . . . . 409
13.4.5.2. Missing CharSet  . . . . . . . . . . . . . . . 410
13.4.5.3. Default String . . . . . . . . . . . . . . . . 410
13.4.5.4. Orientation  . . . . . . . . . . . . . . . . . 411
13.4.5.5. Resource Name and Class  . . . . . . . . . . . 411
13.4.5.6. Font Info  . . . . . . . . . . . . . . . . . . 412
13.4.5.7. OM Automatic . . . . . . . . . . . . . . . . . 412
13.4.6. Creating and Freeing a Font Set  . . . . . . . . 413
13.4.7. Obtaining Font Set Metrics . . . . . . . . . . . 419
13.4.8. Drawing Text Using Font Sets . . . . . . . . . . 427
13.5. Input Methods  . . . . . . . . . . . . . . . . . . 434
13.5.1. Input Method Overview  . . . . . . . . . . . . . 434
13.5.1.1. Input Method Architecture  . . . . . . . . . . 436
13.5.1.2. Input Contexts . . . . . . . . . . . . . . . . 439
13.5.1.3. Getting Keyboard Input . . . . . . . . . . . . 439
13.5.1.4. Focus Management . . . . . . . . . . . . . . . 440
13.5.1.5. Geometry Management  . . . . . . . . . . . . . 440
13.5.1.6. Event Filtering  . . . . . . . . . . . . . . . 442
13.5.1.7. Callbacks  . . . . . . . . . . . . . . . . . . 442
13.5.1.8. Visible Position Feedback Masks  . . . . . . . 443
13.5.1.9. Preedit String Management  . . . . . . . . . . 443
13.5.2. Input Method Management  . . . . . . . . . . . . 446
13.5.2.1. Hot Keys . . . . . . . . . . . . . . . . . . . 447
13.5.2.2. Preedit State Operation  . . . . . . . . . . . 447
13.5.3. Input Method Functions . . . . . . . . . . . . . 448
13.5.4. Input Method Values  . . . . . . . . . . . . . . 452
13.5.4.1. Query Input Style  . . . . . . . . . . . . . . 453
13.5.4.2. Resource Name and Class  . . . . . . . . . . . 455
13.5.4.3. Destroy Callback . . . . . . . . . . . . . . . 455
13.5.4.4. Query IM/IC Values List  . . . . . . . . . . . 456
13.5.4.5. Visible Position . . . . . . . . . . . . . . . 456
13.5.4.6. Preedit Callback Behavior  . . . . . . . . . . 457
13.5.5. Input Context Functions  . . . . . . . . . . . . 457
13.5.6. Input Context Values . . . . . . . . . . . . . . 462
13.5.6.1. Input Style  . . . . . . . . . . . . . . . . . 464
13.5.6.2. Client Window  . . . . . . . . . . . . . . . . 464












13.5.6.3. Focus Window . . . . . . . . . . . . . . . . . 465
13.5.6.4. Resource Name and Class  . . . . . . . . . . . 465
13.5.6.5. Geometry Callback  . . . . . . . . . . . . . . 465
13.5.6.6. Filter Events  . . . . . . . . . . . . . . . . 466
13.5.6.7. Destroy Callback . . . . . . . . . . . . . . . 466
13.5.6.8. String Conversion Callback . . . . . . . . . . 466
13.5.6.9. String Conversion  . . . . . . . . . . . . . . 467
13.5.6.10. Reset State . . . . . . . . . . . . . . . . . 467
13.5.6.11. Hot Keys  . . . . . . . . . . . . . . . . . . 468
13.5.6.12. Hot Key State . . . . . . . . . . . . . . . . 469
13.5.6.13. Preedit and Status Attributes . . . . . . . . 470
13.5.6.13.1. Area  . . . . . . . . . . . . . . . . . . . 470
13.5.6.13.2. Area Needed . . . . . . . . . . . . . . . . 470
13.5.6.13.3. Spot Location . . . . . . . . . . . . . . . 471
13.5.6.13.4. Colormap  . . . . . . . . . . . . . . . . . 471
13.5.6.13.5. Foreground and Background . . . . . . . . . 471
13.5.6.13.6. Background Pixmap . . . . . . . . . . . . . 472
13.5.6.13.7. Font Set  . . . . . . . . . . . . . . . . . 472
13.5.6.13.8. Line Spacing  . . . . . . . . . . . . . . . 472
13.5.6.13.9. Cursor  . . . . . . . . . . . . . . . . . . 472
13.5.6.13.10. Preedit State  . . . . . . . . . . . . . . 472
13.5.6.13.11. Preedit State Notify Callback  . . . . . . 473
13.5.6.13.12. Preedit and Status Callbacks . . . . . . . 474
13.5.7. Input Method Callback Semantics  . . . . . . . . 475
13.5.7.1. Geometry Callback  . . . . . . . . . . . . . . 476
13.5.7.2. Destroy Callback . . . . . . . . . . . . . . . 477
13.5.7.3. String Conversion Callback . . . . . . . . . . 477
13.5.7.4. Preedit State Callbacks  . . . . . . . . . . . 479
13.5.7.5. Preedit Draw Callback  . . . . . . . . . . . . 480
13.5.7.6. Preedit Caret Callback . . . . . . . . . . . . 484
13.5.7.7. Status Callbacks . . . . . . . . . . . . . . . 486
13.5.8. Event Filtering  . . . . . . . . . . . . . . . . 488
13.5.9. Getting Keyboard Input . . . . . . . . . . . . . 489
13.5.10. Input Method Conventions  . . . . . . . . . . . 492
13.5.10.1. Client Conventions  . . . . . . . . . . . . . 492
13.5.10.2. Synchronization Conventions . . . . . . . . . 492
13.6. String Constants . . . . . . . . . . . . . . . . . 493
Chapter 14: Inter-Client Communication Functions . . . . 495
14.1. Client to Window Manager Communication . . . . . . 497
14.1.1. Manipulating Top-Level Windows . . . . . . . . . 497
14.1.2. Converting String Lists  . . . . . . . . . . . . 500
14.1.3. Setting and Reading Text Properties  . . . . . . 507
14.1.4. Setting and Reading the WM_NAME Property . . . . 508
14.1.5. Setting and Reading the WM_ICON_NAME Prop-
erty . . . . . . . . . . . . . . . . . . . . . . . . . . 511
14.1.6. Setting and Reading the WM_HINTS Property
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513
14.1.7. Setting and Reading the WM_NORMAL_HINTS
Property . . . . . . . . . . . . . . . . . . . . . . . . 516
14.1.8. Setting and Reading the WM_CLASS Property
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 522
14.1.9. Setting and Reading the WM_TRANSIENT_FOR
Property . . . . . . . . . . . . . . . . . . . . . . . . 524
14.1.10. Setting and Reading the WM_PROTOCOLS Prop-












erty . . . . . . . . . . . . . . . . . . . . . . . . . . 525
14.1.11. Setting and Reading the WM_COLORMAP_WINDOWS
Property . . . . . . . . . . . . . . . . . . . . . . . . 526
14.1.12. Setting and Reading the WM_ICON_SIZE Prop-
erty . . . . . . . . . . . . . . . . . . . . . . . . . . 528
14.1.13. Using Window Manager Convenience Functions
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 530
14.2. Client to Session Manager Communication  . . . . . 534
14.2.1. Setting and Reading the WM_COMMAND Property
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 534
14.2.2. Setting and Reading the WM_CLIENT_MACHINE
Property . . . . . . . . . . . . . . . . . . . . . . . . 536
14.3. Standard Colormaps . . . . . . . . . . . . . . . . 537
14.3.1. Standard Colormap Properties and Atoms . . . . . 540
14.3.2. Setting and Obtaining Standard Colormaps . . . . 541
Chapter 15: Resource Manager Functions . . . . . . . . . 545
15.1. Resource File Syntax . . . . . . . . . . . . . . . 546
15.2. Resource Manager Matching Rules  . . . . . . . . . 548
15.3. Quarks . . . . . . . . . . . . . . . . . . . . . . 549
15.4. Creating and Storing Databases . . . . . . . . . . 553
15.5. Merging Resource Databases . . . . . . . . . . . . 557
15.6. Looking Up Resources . . . . . . . . . . . . . . . 558
15.7. Storing into a Resource Database . . . . . . . . . 562
15.8. Enumerating Database Entries . . . . . . . . . . . 566
15.9. Parsing Command Line Options . . . . . . . . . . . 568
Chapter 16: Application Utility Functions  . . . . . . . 571
16.1. Using Keyboard Utility Functions . . . . . . . . . 571
16.1.1. KeySym Classification Macros . . . . . . . . . . 575
16.2. Using Latin-1 Keyboard Event Functions . . . . . . 576
16.3. Allocating Permanent Storage . . . . . . . . . . . 578
16.4. Parsing the Window Geometry  . . . . . . . . . . . 579
16.5. Manipulating Regions . . . . . . . . . . . . . . . 581
16.5.1. Creating, Copying, or Destroying Regions . . . . 581
16.5.2. Moving or Shrinking Regions  . . . . . . . . . . 583
16.5.3. Computing with Regions . . . . . . . . . . . . . 583
16.5.4. Determining if Regions Are Empty or Equal
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 586
16.5.5. Locating a Point or a Rectangle in a Region
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 586
16.6. Using Cut Buffers  . . . . . . . . . . . . . . . . 587
16.7. Determining the Appropriate Visual Type  . . . . . 590
16.8. Manipulating Images  . . . . . . . . . . . . . . . 593
16.9. Manipulating Bitmaps . . . . . . . . . . . . . . . 597
16.10. Using the Context Manager . . . . . . . . . . . . 602
Appendix A: Xlib Functions and Protocol Requests . . . . 606
Appendix B:  X Font Cursors  . . . . . . . . . . . . . . 618
Appendix C: Extensions . . . . . . . . . . . . . . . . . 619
Appendix D: Compatibility Functions  . . . . . . . . . . 653
Glossary . . . . . . . . . . . . . . . . . . . . . . . . 670
Index  . . . . . . . . . . . . . . . . . . . . . . . . . 693










