asvisual.h(1)

libAfterImage/asvisual.h
 Defines abstraction layer on top of X Visuals, as well as several
 fundamental color datatypes.
 Structures:
        ColorPair
        ASScanline
        ASVisual
 Functions :
   ASScanline handling:
        prepare_scanline(), free_scanline()
   ASVisual initialization :
        query_screen_visual(), setup_truecolor_visual(),
        setup_pseudo_visual(), setup_as_colormap(),create_asvisual(),
        destroy_asvisual()
   ASVisual encoding/decoding :
        visual2visual_prop(), visual_prop2visual()
   ASVisual convenience functions :
        create_visual_window(), create_visual_pixmap(),
        create_visual_ximage()
 Other libAfterImage modules :
     asimage.h, import.h, blender.h, asfont.h
  Sasha Vasko <sashav at sprintmail dot com>

libAfterImage/alpha
 Alpha channel adds visibility parameter to color value.
 Alpha channel's value of 0xFF signifies complete visibility, while 0
 makes pixel completely transparent.
    #define ALPHA_TRANSPARENT       0x00
    #define ALPHA_SEMI_TRANSPARENT  0x7F
    #define ALPHA_SOLID             0xFF

libAfterImage/ARGB32
 ARGB32 is fundamental datatype that hold 32bit value corresponding to
 pixels color and transparency value (alpha channel) in ARGB
 colorspace. It is encoded as follows :
 Lowermost 8 bits - Blue channel
 bits 8 to 15     - Green channel
 bits 16 to 23    - Red channel
 bits 24 to 31    - Alpha channel
 ASTile.1
    typedef CARD32 ARGB32;
    #define ARGB32_White            0xFFFFFFFF
    #define ARGB32_Black            0xFF000000
    /* default background color is #FF000000 : */
    #define ARGB32_DEFAULT_BACK_COLOR   ARGB32_Black

    #define ARGB32_ALPHA_CHAN       3
    #define ARGB32_RED_CHAN         2
    #define ARGB32_GREEN_CHAN       1
    #define ARGB32_BLUE_CHAN        0
    #define ARGB32_CHANNELS         4

    #define MAKE_ARGB32(a,r,g,b)    (((a)<<24)|(((r)&0x00FF)<<16)| \
                                     (((g)&0x00FF)<<8)|((b)&0x00FF))
    #define MAKE_ARGB32_GREY(a,l)   (((a)<<24)|(((l)&0x00FF)<<16)| \
                                     (((l)&0x00FF)<<8)|((l)&0x00FF))
    #define ARGB32_ALPHA8(c)        (((c)>>24)&0x00FF)
    #define ARGB32_RED8(c)          (((c)>>16)&0x00FF)
    #define ARGB32_GREEN8(c)        (((c)>>8 )&0x00FF)
    #define ARGB32_BLUE8(c)         ( (c)     &0x00FF)
    #define ARGB32_CHAN8(c,i)       (((c)>>((i)<<3))&0x00FF)
    #define MAKE_ARGB32_CHAN8(v,i)  (((v)&0x0000FF)<<((i)<<3))
    #define MAKE_ARGB32_CHAN16(v,i) ((((v)&0x00FF00)>>8)<<((i)<<3))

libAfterImage/ColorPart
 Ids of the channels. These are basically synonyms to related ARGB32
 channel numbers
    typedef enum
    {
      IC_BLUE   = ARGB32_BLUE_CHAN ,
      IC_GREEN  = ARGB32_GREEN_CHAN,
      IC_RED    = ARGB32_RED_CHAN  ,
      IC_ALPHA  = ARGB32_ALPHA_CHAN,
      IC_NUM_CHANNELS = ARGB32_CHANNELS
    }
    ColorPart;

libAfterImage/ColorPair
  ColorPair

 Convenient structure to hold pair of colors.
    typedef struct ColorPair
    {
      ARGB32 fore;
      ARGB32 back;
    }ColorPair;

libAfterImage/ASScanline
  ASScanline

 ASScanline is a structure to hold contents of the single scanline.
 ASScanline holds data for the single scanline, split into channels
 with 32 bits per pixel per channel. All the memory is allocated at
 once, and then split in between channels. There are three ways to
 access channel data :
 1) using blue, green, red, alpha pointers.
 2) using channels[] array of pointers - convenient in loops
 4) using xc3, xc2, xc1 pointers. These are different from red, green,
 blue in the way that xc3 will point to blue when BGR mode is specified
 at the time of creation, otherwise it will point to red channel.
 Likewise xc1 will point to red in BGR mode and blue otherwise.
 xc2 always points to green channel's data. This is convenient while
 writing XImages and when channels in source and destination has to be
 reversed, while reading images from files.
 Channel data is always aligned by 8 byte boundary allowing for
 utilization of MMX, floating point and other 64bit registers for
 transfer and processing.
 ASImage
    typedef struct ASScanline
    {
    #define SCL_DO_BLUE         (0x01<<ARGB32_BLUE_CHAN )
    #define SCL_DO_GREEN        (0x01<<ARGB32_GREEN_CHAN)
    #define SCL_DO_RED          (0x01<<ARGB32_RED_CHAN  )
    #define SCL_DO_ALPHA        (0x01<<ARGB32_ALPHA_CHAN)
    #define SCL_DO_COLOR        (SCL_DO_RED|SCL_DO_GREEN|SCL_DO_BLUE)
    #define SCL_DO_ALL          (SCL_DO_RED|SCL_DO_GREEN|SCL_DO_BLUE| \
                                 SCL_DO_ALPHA)
        CARD32         flags ;            /* combination of  the above values */
        CARD32        *buffer ;
        CARD32        *blue, *green, *red, *alpha ;
        CARD32        *channels[IC_NUM_CHANNELS];
        CARD32        *xc3, *xc2, *xc1;   /* since some servers require
                                           * BGR mode here we store what
                                           * goes into what color component
                                           * in XImage */
        ARGB32         back_color;
        unsigned int   width, shift;
        unsigned int   offset_x ;
    }ASScanline;

libAfterImage/asvisual/prepare_scanline()
 ASScanline *prepare_scanline ( unsigned int width,
                                unsigned int shift,
                                ASScanline *reusable_memory,
                                Bool BGR_mode);
 width           - width of the scanline.
 shift           - format of contained data. 0 means - 32bit unshifted
                   8 means - 24.8bit ( 8 bit left shifted ).
 reusable_memory - preallocated object.
 BGR_mode        - if True will cause xc3 to point to Blue and xc1 to
                   point to red.
 This function allocates memory ( if reusable_memory is NULL ) for
 the new ASScanline structure. Structures buffers gets allocated to
 hold scanline data of at least width pixel wide. Buffers are adjusted
 to start on 8 byte boundary.

libAfterImage/asvisual/free_scanline()
 void       free_scanline ( ASScanline *sl, Bool reusable );
 sl       - pointer to previously allocated ASScanline structure to be
            deallocated.
 reusable - if true then ASScanline object itself will not be
            deallocated.
 free_scanline() frees all the buffer memory allocated for ASScanline.
 If reusable is false then object itself in not freed. That is usable
 for declaring ASScanline on stack.

libAfterImage/ASVisual
  ASVisual

 ASVisual is abstraction layer on top of X Server Visual.
 This structure has been introduced in order to compensate for the
 fact that X may have so many different types of Visuals. It provides
 shortcuts to most Visual data, compensated for differences in Visuals.
 For PseudoColor visual it also contains preallocated set of colors.
 This colormap allows us to write XImages very fast and without
 exhausting available X colors. This colormap consist of 8, 64, or 4096
 colors and constitutes fraction of colors available in particular
 colordepth. This colors are allocated to be evenly spread around RGB
 spectrum. Thus when converting from internal presentation - all we
 need to do is to discard unused bits, and use rest of them bits as
 an index in our colormap. Opposite conversion is much trickier and we
 engage into nasty business of having hash table mapping pixel values
 into colors, or straight table doing same in lower colordepths.
 Idea is that we do all internal processing in 32bit colordepth, and
 ASVisual provides us with means to convert it to actual X display
 format. Respectively ASVisual has methods to write out XImage lines
 and read XImage lines.
 ASVisual creation is a tricky process. Basically first we have to go
 through the list of available Visuals and choose the best suitable.
 Then based on the type of this Visual we have to setup our data
 members and method hooks. Several functions provided for that :
  query_screen_visual()    - will lookup best suitable visual
  setup_truecolor_visual() - will setup hooks if visual is TrueColor
  setup_pseudo_visual()  - will setup hooks and data if Visual is
                             PseudoColor.
  setup_as_colormap()      - will preallocate colors for PseudoColor.
 Alternative to the above is :
  create_asvisual()        - it encapsulates all of the above
                             functionality, and returns completely set
                             up ASVisual object.
 Since Visual selected for ASVisual may differ from default
 ( we choose the best suitable ), all the window creation function
 must provide colormap and some other parameters, like border color
 for example. Thus we created some convenience functions.
 These should be used instead of standard Xlib calls :
  create_visual_window() - to create window
  create_visual_pixmap() - to create pixmap
  create_visual_ximage() - to create XImage
 ASVisual could be dealolocated and its resources freed with :
  destroy_asvisual()
 asview.c: ASView
    typedef struct ASVisual
    {
        Display      *dpy;
        XVisualInfo   visual_info;
        /* this things are calculated based on Visual : */
        unsigned long rshift, gshift, bshift;
        unsigned long rbits,  gbits,  bbits;
        unsigned long true_depth;   /* could be 15 when X reports 16 */
        Bool          BGR_mode;
        Bool          msb_first;
        /* we must have colormap so that we can safely create windows
         * with different visuals even if we are in TrueColor mode : */
        Colormap      colormap;
        Bool          own_colormap; /* tells us to free colormap when we
                                     * done */
        unsigned long black_pixel, white_pixel;
        /* for PseudoColor mode we need some more stuff : */
        enum {
            ACM_None = 0,
            ACM_3BPP,
            ACM_6BPP,
            ACM_12BPP,
        } as_colormap_type ;        /* there can only be 64 or 4096 entries
                                     * so far ( 6 or 12 bpp) */
        unsigned long *as_colormap; /* array of preallocated colors for
                                     * PseudoColor mode */
        union                       /* reverse color lookup tables : */
        {
            ARGB32              *xref;
            struct ASHashTable  *hash;
        }as_colormap_reverse ;

        /* different useful callbacks : */
        CARD32 (*color2pixel_func)    ( struct ASVisual *asv,
                                        CARD32 encoded_color,
                                        unsigned long *pixel);
        void   (*pixel2color_func)    ( struct ASVisual *asv,
                                        unsigned long pixel,
                                        CARD32 *red, CARD32 *green,
                                        CARD32 *blue);
        void   (*ximage2scanline_func)( struct ASVisual *asv, XImage *xim,
                                        ASScanline *sl, int y,
                                        unsigned char *xim_data );
        void   (*scanline2ximage_func)( struct ASVisual *asv, XImage *xim,
                                        ASScanline *sl, int y,
                                        unsigned char *xim_data );
    #define ARGB2PIXEL(asv,argb,pixel)         \
        (asv)->color2pixel_func((asv),(argb),(pixel))
    #define GET_SCANLINE(asv,xim,sl,y,xim_data) \
        (asv)->ximage2scanline_func((asv),(xim),(sl),(y),(xim_data))
    #define PUT_SCANLINE(asv,xim,sl,y,xim_data) \
        (asv)->scanline2ximage_func((asv),(xim),(sl),(y),(xim_data))

    }ASVisual;

libAfterImage/asvisual/query_screen_visual()
 Bool query_screen_visual( ASVisual *asv, Display *dpy, int screen,
                           Window root, int default_depth );
 asv        - preallocated ASVisual structure.
 dpy        - valid pointer to opened X display.
 screen     - screen number on which to query visuals.
 root       - root window on that screen.
 default_depth- default colordepth of the screen.
 True on success, False on failure
 ASVisual structure pointed by asv will have the following data
 members set on success :
 dpy, visual_info, colormap, own_colormap, black_pixel, white_pixel.
 query_screen_visual() will go though prioritized list of possible
 Visuals and attempt to match those to what is available on the
 specified screen. If all items from list fail, then it goes about
 querying default visual.
 Once X Visual has been identified, we create X colormap and allocate
 white and black pixels from it.

libAfterImage/asvisual/setup_truecolor_visual()
 Bool setup_truecolor_visual( ASVisual *asv );
 asv        - preallocated ASVisual structure.
 True on success, False if visual is not TrueColor.
 setup_truecolor_visual() checks if Visual is indeed TrueColor and if
 so it goes about querying color masks, deducing real XImage
 colordepth, and whether we work in BGR mode. It then goes about
 setting up correct hooks to X IO functions.

libAfterImage/asvisual/setup_pseudo_visual()
 void setup_pseudo_visual( ASVisual *asv  );
 asv        - preallocated ASVisual structure.
 setup_pseudo_visual() assumes that Visual is PseudoColor. It then
 tries to decide as to how many colors preallocate, and goes about
 setting up correct X IO hooks and possibly initialization of reverse
 colormap in case ASVisual already has colormap preallocated.

libAfterImage/asvisual/setup_as_colormap()
 void setup_as_colormap( ASVisual *asv );
 asv        - preallocated ASVisual structure.
 That has to be called in order to pre-allocate sufficient number of
 colors. It uses colormap size identification supplied in ASVisual
 structure. If colors where preallocated successfully - it will also
 create reverse lookup colormap.

libAfterImage/asvisual/create_asvisual()
 ASVisual *create_asvisual( Display *dpy, int screen,
                            int default_depth,
                            ASVisual *reusable_memory );
 dpy        - valid pointer to opened X display.
 screen     - screen number on which to query visuals.
 root       - root window on that screen.
 default_depth- default colordepth of the screen.
 reusable_memory - pointer to preallocated ASVisual structure.
 Pointer to ASVisual structure initialized with enough information
 to be able to deal with current X Visual.
 This function calls all the needed functions in order to setup new
 ASVisual structure for the specified screen. If reusable_memory is
 not null - it will not allocate new ASVisual structure, but instead
 will use supplied one. Useful for allocating ASVisual on stack.

libAfterImage/asvisual/destroy_asvisual()
 void destroy_asvisual( ASVisual *asv, Bool reusable );
 asv      - valid ASVisual structure.
 reusable - if True it will cause function to not free object
            itself.
 Cleanup function. Frees all the memory and deallocates all the
 resources. If reusable is False it will also free the object, pointed
 to by asv.
 asview.c: ASView.2

libAfterImage/asvisual/visual2visual_prop()
 Bool visual2visual_prop( ASVisual *asv, size_t *size,
                          unsigned long *version, unsigned long **data );
 asv        - valid ASVisual structure.
 size         - size of the encoded memory block.
 version      - version of the encoding
 data         - actual encoded memory block
 True on success, False on failure
 This function will encode ASVisual structure into memory block of
 32 bit values, suitable for storing in X property.

libAfterImage/asvisual/visual_prop2visual()
 Bool visual_prop2visual( ASVisual *asv, Display *dpy, int screen,
                          size_t size,
                          unsigned long version, unsigned long *data );
 asv       - valid ASVisual structure.
 dpy       - valid pointer to open X display.
 screen    - screen number.
 size      - encoded memory block's size.
 version   - version of encoding.
 data      - actual encoded memory block.
 True on success, False on failure
 visual_prop2visual() will read ASVisual data from the memory block
 encoded by visual2visual_prop(). It could be used to read data from
 X property and convert it into usable information - such as colormap,
 visual info, etc.
 Note: setup_truecolor_visual() or setup_pseudo_visual() has to be
 invoked in order to complete ASVisual setup.

libAfterImage/asvisual/create_visual_window()
 Window  create_visual_window( ASVisual *asv, Window parent,
                               int x, int y,
                               unsigned int width, unsigned int height,
                               unsigned int border_width,
                               unsigned int class,
                               unsigned long mask,
                               XSetWindowAttributes *attributes );
 asv           - pointer to the valid ASVisual structure.
 parent        - Window ID of the parent the window.
 x, y          - initial position of the new window.
 width, height - initial size of the new window.
 border_width  - initial border width of the new window.
 class         - Window class  - InputOnly or InputOutput.
 mask          - defines what attributes are set.
 attributes    - different window attributes.
 ID of the newly created window on success. None on failure.
 create_visual_window() will do sanity checks on passed parameters,
 it will then add mandatory attributes if needed, and attempt to
 create window for the specified ASVisual.

libAfterImage/asvisual/create_visual_pixmap()
 Pixmap  create_visual_pixmap( ASVisual *asv, Window root,
                               unsigned int width, unsigned int height,
                               unsigned int depth );
 asv            - pointer to the valid ASVisual structure.
 root           - Window ID of the root window of destination screen
 width, height  - size of the pixmap to create.
 depth          - depth of the pixmap to create. If 0 asv->true_depth
                  will be used.
 ID of the newly created pixmap on success. None on failure.
 create_visual_pixmap() will perform sanity checks on passed
 parameters, and attempt to create pixmap for the specified ASVisual,
 root and depth.

libAfterImage/asvisual/create_visual_ximage()
 XImage* create_visual_ximage( ASVisual *asv,
                               unsigned int width, unsigned int height,
                               unsigned int depth );
 asv            - pointer to the valid ASVisual structure.
 width, height  - size of the XImage to create.
 depth          - depth of the XImage to create. If 0 asv->true_depth
                  will be used.
 pointer to newly created XImage on success. NULL on failure.
 create_visual_ximage() will perform sanity checks on passed
 parameters, and it will attempt to create XImage of sufficient size,
 and specified colordepth. It will also setup hooks for XImage
 deallocation to be handled by custom function.