asfont.html

Generated from asfont.h with ROBODoc v3.2.3 on Fri Jul 13 13:35:00 2001

## libAfterImage/asfont.h

DESCRIPTION

     Text drawing functionality.
     Text is drawn as an ASImage with only alpha channel. Since alpha
     channel is 8 bit widths that allows for 256 shades to be used in
     rendered glyphs. That in turn allows for smoothing and antialiasing
     of the drawn text. Such an approcah allows for easy manipulation of
     the drawn text, such as changing color, making it transparent,
     texturizing, rotation, etc.

     libAfterImage supports two types of fonts :
     Fonts that could be rendered using standard Xlib functionality, and
     fonts rendered by FreeType 2 library. That may include TrueType
     fonts. When fonts are obtained via Xlib special processing is
     performed in order to smooth its shape and leverage 256 shades
     palette available.

     Any font being used is has to be opened first. At that time its
     properties are analysed and glyphs are cached in clients memory.
     Special RLE compression method is used for font glyphs, significantly
     reducing memory utilization without any effect on performance.

     Font management and drawing functionality has been designed with
     internatiolization in mind, althou support for locales is not
     complete yet.

SEE ALSO

     Structures :
              ASFontManager
              ASFont
              ASGlyph
              ASGlyphRange

     Functions :
              create_font_manager(), destroy_font_manager(),
              open_freetype_font(), open_X11_font(), get_asfont(),
              destroy_font(), print_asfont(), print_asglyph(),
              draw_text()

     Other libAfterImage modules :
         asimage.h, asvisual.h, blender.h, import.h

AUTHOR

     Sasha Vasko <sashav at sprintmail dot com>

## libAfterImage/MAX_GLYPHS_PER_FONT

FUNCTION

     Max value of glyphs per font allowed. We need that so we can detect
     and avoid broken fonts somehow.

SOURCE

        #define MAX_GLYPHS_PER_FONT  2048

## libAfterImage/ASFontType

FUNCTION

     Supported types of fonts - Xlib or FreeType 2
     ASF_GuessWho will enable autodetection of the font type.
     It is attempted to be opened as FreeType font first, and if that
     fails - it will be opened as Xlib font.

SOURCE

        typedef enum
        {
            ASF_X11 = 0,
            ASF_Freetype,
            ASF_GuessWho
        }ASFontType;

## libAfterImage/CHAR_SIZE

FUNCTION

     Convinient macro so we can transparently determine the number of
     bytes that character spans. It assumes UTF-8 encoding when I18N is
     enabled.

SOURCE

        #ifdef I18N
        /* size of the UTF-8 encoded character is based on value of the first byte : */
        #define CHAR_SIZE(c)    (((c)&0x80)?(((c)&0x40)?(((c)&0x20)?(((c)&0x10)?5:4):3):2):1)
        #else
        #define CHAR_SIZE(c)    1
        #endif

## libAfterImage/ASGlyph

NAME

     ASGlyph

DESCRIPTION

     Stores glyph's image, as well as width, height and other
     characteristics of the glyph.

SOURCE

        typedef struct ASGlyph
        {
            CARD8          *pixmap ;        /* glyph's RLE encoded pixmap */
            unsigned short  width, height ; /* meaningfull width and height
                                             * of the glyphs pixmap */
            short  lead, step ;             /* distance pen position to glyph
                                             * beginning and to the next glyph */
            short  ascend, descend ;        /* distance of the top of the
                                             * glyph from the baseline */
        }ASGlyph;

## libAfterImage/ASGlyphRange

NAME

     ASGlyphRange

DESCRIPTION

     Organizes glyphs that belongs to the continuos range of char codes.
     ASGlyphRange structures could be tied together to cover entire
     codeset supported by the font.

SOURCE

        typedef struct ASGlyphRange
        {
            unsigned long   min_char, max_char; /* Code range.
                                                 * for some locales that would
                                                 * be sufficient to simply set
                                                 * range of characteres
                                                 * supported by font */
            ASGlyph *glyphs;                    /* array of glyphs belonging to
                                                 * that code range */
            struct ASGlyphRange *below, *above;
        }ASGlyphRange;

## libAfterImage/ASFont

NAME

     ASFont

DESCRIPTION

     Structure to contain all the font characteristics, as well as
     set of glyph images. Such structure has to be created/opened prior to
     being able to draw characters with any font.

SOURCE

        typedef struct ASFont
        {
            unsigned long   magic ;

            struct ASFontManager *fontman;  /* our owner */
            char                 *name;

            ASFontType      type ;
            ASGlyphRange   *codemap;        /* linked list of glyphsets, each
                                             * representing continuos range of
                                             * available codes */
            ASGlyph         default_glyph;  /* valid glyph to be drawn when
                                             * code is not valid */

            unsigned int    max_height,     /* maximiu height of the character
                                             * glyph */
                            max_ascend,     /* maximum distance from the baseline
                                             * to the top of the character glyph */
                            space_size;     /* fixed width value to be used when
                                             * rendering spaces and tabs */
        #define LEFT_TO_RIGHT    1
        #define RIGHT_TO_LEFT   -1
            int             pen_move_dir ;  /* direction of the text flow */
        #ifdef HAVE_FREETYPE
            FT_Face         ft_face;        /* free type font handle */
        #else
            CARD32         *pad;
        #endif

        }ASFont;

## libAfterImage/ASFontManager

NAME

     ASFontManager

DESCRIPTION

     Global data identifying connection to external libraries, as well as
     fonts location paths.
     This structure has to be created/initialized prior to any font being
     loaded.
     It also holds list of fonts that are currently open, allowing for
     easy access to fonts.
     When ASFontManagaer object is destroyd it automagically closes all
     the open fonts.

SOURCE

        typedef struct ASFontManager
        {
            Display    *dpy;
            char       *font_path ;

            ASHashTable *fonts_hash ;

            size_t       unicode_used;
            CARD32      *local_unicode;                /* list of unicodes from current locale
                                                        * - we use it to limit number of glyphs
                                                        * we load */
            Bool        ft_ok ;
        #ifdef HAVE_FREETYPE
            FT_Library  ft_library;                    /* free type library handle */
        #else
            void       *pad ;
        #endif
        }ASFontManager;

## libAfterImage/ASText3DType

FUNCTION

     Available types of 3D text to be drawn.

SOURCE

        typedef enum ASText3DType{
            AST_Plain =0,                              /* regular 2D text */
            AST_Embossed,
            AST_Sunken,
            AST_ShadeAbove,
            AST_ShadeBelow,
            AST_EmbossedThick,
            AST_SunkenThick,
            AST_3DTypes
        }ASText3DType;

## libAfterImage/asfont/create_font_manager()

SYNOPSIS

     ASFontManager *create_font_manager( Display *dpy,
                                         const char *font_path,
                                         ASFontManager *reusable_memory );

INPUTS

     dpy             - pointer to valid and opened Display.
     font_path       - string, representing colon separated list of
                       directories to search for FreeType fonts.
     reusable_memory - optional preallocated memory for the ASFontMagaer
                       object

RETURN VALUE

     Pointer to Initialized ASFontManager object on success.
     NULL otherwise.

DESCRIPTION

     create_font_manager() will create new ASFontManager structure if
     needed. It wioll then store copy of font_path and supplied pointer to
     Display in it. At that time Hash table of loaded fonts is initialized,
     and if needed FreeType library is initialized as well.
     ASFontManager object returned by this functions has to be open at all
     times untill text drawing is no longer needed.

## libAfterImage/asfont/destroy_font_manager()

SYNOPSIS

     void destroy_font_manager( ASFontManager *fontman,
                                Bool reusable );

INPUTS

     fontman  - pointer to valid ASFontManager object to be deallocated.
     reusable - If True, then memory holding object itself will not be
                freed - only resources will be deallocated. That is
                usefull for structures created on stack.

DESCRIPTION

     destroy_font_manager() closes all the fonts open with this
     ASFontManager. It will also close connection to FreeType library, and
     deallocate all cached data. If reusable is False - then memory used
     for object itself will not be freed.

## libAfterImage/asfont/open_freetype_font()

SYNOPSIS

     ASFont *open_freetype_font( ASFontManager *fontman,
                                 const char *font_string,
                                 int face_no,
                                 int size, Bool verbose);

INPUTS

     fontman     - pointer to previously created ASFontManager. Needed for
                   connection to FreeType library, as well as path to
                   search fonts in.
     font_string - filename of the file containing font's data.
     face_no     - number of face within the font file
     size        - font size in points. Applicable only to scalable fonts,
                   such as TrueType.
     verbose     - if True, extensive error messages will be printed if
                   problems encountered.

RETURN VALUE

     pointer to Opened ASFont structure, containing all the glyphs of the
     font, as well as other relevant info. On failure returns NULL.

DESCRIPTION

     open_freetype_font() will attempt to find font file in any of the
     directories specified in ASFontManager's font_path. If it fails to do
     so - then it will check if filename has alldigit extentions. It will
     then try to interpret that extention as a face number, and try and
     find the file with extention stripped off.
     If file was found function will atempt to read it using FreeType
     library. If requested face is not available in the font - face 0 will
     be used.
     On success all the font's glyphs will be rendered and cached, and
     needed font geometry info collected.
     When FreeType Library is not available that function does nothing.

## libAfterImage/asfont/open_X11_font()

SYNOPSIS

     ASFont *open_X11_font( ASFontManager *fontman,
                            const char *font_string);

INPUTS

     fontman     - pointer to previously created ASFontManager. Needed for
                   connection X Server.
     font_string - name of the font as recognized by Xlib.

RETURN VALUE

     pointer to Opened ASFont structure, containing all the glyphs of the
     font, as well as other relevant info. On failure returns NULL.

DESCRIPTION

     open_X11_font() attempts to load and query font using Xlib calls.
     On success it goes thgroughthe codemap of the font and renders all
     the glyphs available. Glyphs then gets transfered to the client's
     memory and encoded using RLE compression. At this time smoothing
     filters are applied on glyph pixmaps, if its size exceeds threshold.

TODO

     implement proper XFontSet support, when used with I18N enabled.

## libAfterImage/asfont/get_asfont()

SYNOPSIS

     ASFont *get_asfont( ASFontManager *fontman,
                         const char *font_string,
                         int face_no, int size,
                         ASFontType type );

INPUTS

     fontman     - pointer to previously created ASFontManager. Needed for
                   connection to FreeType library, path to search fonts
                   in, and X Server connection.
     font_string - font name or filename of the file containing font's data.
     face_no     - number of face within the font file
     size        - font size in points. Applicable only to scalable fonts,
                   such as TrueType.
     type        - specifies the type of the font, or GuessWho for
                   autodetection.

RETURN VALUE

     pointer to Opened ASFont structure, containing all the glyphs of the
     font, as well as other relevant info. On failure returns NULL.

DESCRIPTION

     This function provides unified interface to font loading. It performs
     search in ASFontManager's list to see if this specific font has been
     loaded already, and if so - returns pointer to relevant structure.
     Otherwise it tryes to load font as FreeType font first, and then
     Xlib font, unless exact font type is specifyed.

## libAfterImage/asfont/destroy_font()

SYNOPSIS

     void destroy_font( ASFont *font );

INPUTS

     font - pointer to the valid ASFont structure containing loaded font.

DESCRIPTION

     This function will close the font, remove it from ASFontManager's
     list, destroy all the glyphs and generally free everything else used
     by ASFont.

## libAfterImage/asfont/print_asfont()

SYNOPSIS

     void    print_asfont( FILE* stream,
                           ASFont* font);

INPUTS

     stream - output file pointer
     font   - pointer to ASFont structure to print.

DESCRIPTION

     prints all the geometry information about font.

## libAfterImage/asfont/print_asglyph()

SYNOPSIS

     void   print_asglyph( FILE* stream,
                             ASFont* font, unsigned long c);

INPUTS

     stream - output file pointer
     font   - pointer to ASFont structure to print.
     c      - character code to print glyph for

DESCRIPTION

     prints out contents of the cached glyph for specifyed character code.

## libAfterImage/asfont/draw_text()

SYNOPSIS

     ASImage *draw_text( const char *text,
                         ASFont *font, ASText3DType type,
                         int compression );
     Bool get_text_size( const char *text,
                         ASFont *font, ASText3DType type,
                         unsigned int *width, unsigned int *height );

INPUTS

     text       - actuall text to render
     font       - pointer to ASFont to render text with
     type         - one of the few available types of 3D text.
     compression  - compression level to attempt on resulting ASImage.
     width        - pointer to value to be set to text width.
     height       - pointer to value to be set to text height.

RETURN VALUE

     Pointer to new ASImage containing rendered text on success.
     NULL on failure.

DESCRIPTION

     draw_text() creates new ASImage of the size big enough to contain
     entire text. It then renders the text using supplied font as an alpha
     channel of ASImage.
     get_text_size() can be used to determine the size of the text about
     to be drawn, so that appropriate drawable can be prepared.