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# ASVisual

abstraction layer on top of X Visuals, focusing on color handling

libAfterImage/asvisual.h

- NAME

  asvisual

  - Defines abstraction layer on top of X Visuals, as well as several fundamental color datatypes.

- SEE ALSO

      Structures:
              ColorPair
              ASVisual

      Functions :
        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 :
               ascmap.h asfont.h asimage.h asvisual.h blender.h export.h
               import.h transform.h ximage.h

- AUTHOR

      Sasha Vasko <sasha at aftercode dot net>

libAfterImage/alpha

- FUNCTION

      Alpha channel adds visibility parameter to color value.
      Alpha channel's value of 0xFF signifies complete visibility, while 0
      makes pixel completely transparent.

- SOURCE

      #define ALPHA_TRANSPARENT       0x00
      #define ALPHA_SEMI_TRANSPARENT  0x7F
      #define ALPHA_SOLID             0xFF

libAfterImage/ARGB32

- NAME

  ARGB32

  - main color datatype

- FUNCTION

      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

- EXAMPLE

      ASTile.1

- SOURCE

      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)    ((( (CARD32)a)        <<24)| \
                                       ((((CARD32)r)&0x00FF)<<16)| \
                                       ((((CARD32)g)&0x00FF)<<8 )| \
                                       (( (CARD32)b)&0x00FF))

      #define MAKE_ARGB32_GREY8(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))

      #ifdef __GNUC__
      #define ARGB32_ALPHA16(c)       ({ CARD32 __c = ARGB32_ALPHA8(c); __c | (__c<<8);})
      #define ARGB32_RED16(c)         ({ CARD32 __c = ARGB32_RED8(c); __c | (__c<<8);})
      #define ARGB32_GREEN16(c)       ({ CARD32 __c = ARGB32_GREEN8(c); __c | (__c<<8);})
      #define ARGB32_BLUE16(c)        ({ CARD32 __c = ARGB32_BLUE8(c); __c | (__c<<8);})
      #define ARGB32_CHAN16(c,i)      ({ CARD32 __c = ARGB32_CHAN8(c,i); __c | (__c<<8);})
      #else
      #define ARGB32_ALPHA16(c)       ((((c)>>16)&0x00FF00)|(((c)>>24)&0x0000FF))
      #define ARGB32_RED16(c)         ((((c)>>8 )&0x00FF00)|(((c)>>16)&0x0000FF))
      #define ARGB32_GREEN16(c)       (( (c)     &0x00FF00)|(((c)>>8 )&0x0000FF))
      #define ARGB32_BLUE16(c)        ((((c)<<8) &0x00FF00)|(((c)    )&0x0000FF))
      #define ARGB32_CHAN16(c,i)      ((ARGB32_CHAN8(c,i)<<8)|ARGB32_CHAN8(c,i))
      #endif

      #define MAKE_ARGB32_CHAN16(v,i) ((((v)&0x00FF00)>>8)<<((i)<<3))

libAfterImage/ColorPart

- NAME

  IC_RED

  - red channel

  IC_GREEN

  - green channel

  IC_BLUE

  - blue channel

  IC_ALPHA

  - alpha channel

  IC_NUM_CHANNELS

  - number of supported channels

- FUNCTION

      Ids of the channels. These are basically synonyms to related ARGB32
      channel numbers

- SOURCE

      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

- NAME

  ColorPair

  - convenient structure to hold pair of colors.

- SOURCE

      typedef struct ColorPair
      {
        ARGB32 fore;
        ARGB32 back;
      }ColorPair;

libAfterImage/ARGB32_manhattan_distance()

- NAME

  ARGB32_manhattan_distance()

  - This function can be used to evaluate closeness of two colors.

- SYNOPSIS

      long ARGB32_manhattan_distance (long a, long b);

- INPUTS

  a,
    b - ARGB32 color values to calculate Manhattan distance in between

- RETURN VALUE

      returns calculated Manhattan distance.

libAfterImage/ASVisual

- NAME

  ASVisual

  - an abstraction layer on top of X Server Visual.

- DESCRIPTION

      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()

- EXAMPLE

      asview.c: ASView

- SOURCE

      typedef struct ASVisual
      {
          Display      *dpy;

          /* This envvar will be used to determine what X Visual
           * (in hex) to use. If unset then best possible will
           * be selected automagically : */
      #define ASVISUAL_ID_ENVVAR "AFTERIMAGE_VISUAL_ID"

          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,
                                          struct ASScanline *sl, int y,
                                          unsigned char *xim_data );
          void   (*scanline2ximage_func)( struct ASVisual *asv,
                                          XImage *xim,
                                          struct ASScanline *sl, int y,
                                          unsigned char *xim_data );

      #define ASGLX_Unavailable           0
      #define ASGLX_Available             (0x01<<0)
      #define ASGLX_DoubleBuffer          (0x01<<1)
      #define ASGLX_RGBA                  (0x01<<2)
      #define ASGLX_UseForImageTx         (0x01<<3)
          ASFlagType glx_support ;    /* one of the above flags */

          void *glx_scratch_gc_indirect ; /* (GLXContext) */
          void *glx_scratch_gc_direct ;   /* (GLXContext) */

          Window scratch_window;

      #ifndef X_DISPLAY_MISSING
      #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))
      #else
      #define ARGB2PIXEL(asv,argb,pixel)         \
          do{ break; }while(0)
      #define GET_SCANLINE(asv,xim,sl,y,xim_data) \
          do{ break; }while(0)
      #define PUT_SCANLINE(asv,xim,sl,y,xim_data) \
          do{ break; }while(0)
      #endif
      }ASVisual;

libAfterImage/query_screen_visual()

- NAME

  query_screen_visual_id()

  query_screen_visual()

- SYNOPSIS

      Bool query_screen_visual_id( ASVisual *asv, Display *dpy, int screen,
                                Window root, int default_depth,
                                   VisualID visual_id, Colormap cmap );
      Bool query_screen_visual( ASVisual *asv, Display *dpy, int screen,
                                Window root, int default_depth );

- INPUTS

  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.
  visual_id
    - optional ID of prefered Visual.
  cmap
    - optional colormap to be used.

- RETURN VALUE

      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.

- DESCRIPTION

      query_screen_visual_id() 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.
      query_screen_visual is identical to query_screen_visual_id with
      visual_id and cmap set to 0.
      Once X Visual has been identified, we create X colormap and allocate
      white and black pixels from it.

libAfterImage/setup_truecolor_visual()

- NAME

  setup_truecolor_visual()

- SYNOPSIS

      Bool setup_truecolor_visual( ASVisual *asv );

- INPUTS

  asv
    - preallocated ASVisual structure.

- RETURN VALUE

      True on success, False if visual is not TrueColor.

- DESCRIPTION

      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/setup_pseudo_visual()

- NAME

  setup_pseudo_visual()

- SYNOPSIS

      void setup_pseudo_visual( ASVisual *asv  );

- INPUTS

  asv
    - preallocated ASVisual structure.

- DESCRIPTION

      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/setup_as_colormap()

- NAME

  setup_as_colormap()

- SYNOPSIS

      void setup_as_colormap( ASVisual *asv );

- INPUTS

  asv
    - preallocated ASVisual structure.

- DESCRIPTION

      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/create_asvisual_for_id()

- NAME

  create_asvisual_for_id()

- SYNOPSIS

      ASVisual *create_asvisual_for_id( Display *dpy, int screen,
                                        int default_depth,
                                        VisualID visual_id, Colormap cmap,
                                        ASVisual *reusable_memory );

- INPUTS

  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.
  visual_id
    - ID of X visual to use.
  cmap
    - optional ID of the colormap to be used.
  reusable_memory
    - pointer to preallocated ASVisual structure.

- RETURN VALUE

      Pointer to ASVisual structure initialized with enough information
      to be able to deal with current X Visual.

- DESCRIPTION

      This function calls all the needed functions in order to setup new
      ASVisual structure for the specified screen and visual. 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.
      This particular function will not do any autodetection and will use
      Visual ID supplied. That is usefull when libAfterImage is used with
      an app that has its own approach to Visual handling, and since Visuals
      on all Windows, Pixmaps and colormaps must match, there is a need to
      synchronise visuals used by an app and libAfterImage.

libAfterImage/create_asvisual()

- NAME

  create_asvisual()

- SYNOPSIS

      ASVisual *create_asvisual( Display *dpy, int screen,
                                 int default_depth,
                                 ASVisual *reusable_memory );

- INPUTS

  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.

- RETURN VALUE

      Pointer to ASVisual structure initialized with enough information
      to be able to deal with current X Visual.

- DESCRIPTION

      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.
      It is different from create_asvisualfor_id() in that it will attempt
      to autodetect best possible visual for the screen. For example on some
      SUN Solaris X servers there will be both 8bpp pseudocolor and 24bpp
      truecolor, and default will be 8bpp. In this scenario libAfterImage
      will detect and use 24bpp true color visual, thus producing much better
      results.

libAfterImage/destroy_asvisual()

- NAME

  destroy_asvisual()

- SYNOPSIS

      void destroy_asvisual( ASVisual *asv, Bool reusable );

- INPUTS

  asv
    - valid ASVisual structure.
  reusable
    - if True it will cause function to not free object itself.

- DESCRIPTION

      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.

- EXAMPLE

      asview.c: ASView.2

libAfterImage/visual2visual_prop()

- NAME

  visual2visual_prop()

- SYNOPSIS

      Bool visual2visual_prop( ASVisual *asv, size_t *size,
                               unsigned long *version, unsigned long **data );

- INPUTS

  asv
    - valid ASVisual structure.

- RETURN VALUE

      size         - size of the encoded memory block.
      version      - version of the encoding
      data         - actual encoded memory block
      True on success, False on failure

- DESCRIPTION

      This function will encode ASVisual structure into memory block of
      32 bit values, suitable for storing in X property.

libAfterImage/visual_prop2visual()

- NAME

  visual_prop2visual()

- SYNOPSIS

      Bool visual_prop2visual( ASVisual *asv, Display *dpy, int screen,
                               size_t size,
                               unsigned long version, unsigned long *data );

- INPUTS

  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.

- RETURN VALUE

      True on success, False on failure

- DESCRIPTION

      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/create_visual_window()

- NAME

  create_visual_window()

- SYNOPSIS

      Window  create_visual_window( ASVisual *asv, Window parent,
                                    int x, int y,
                                    unsigned int width, unsigned int height,
                                    unsigned int border_width,
                                    unsigned int wclass,
                                    unsigned long mask,
                                    XSetWindowAttributes *attributes );

- INPUTS

  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.
  wclass
    - Window class - InputOnly or InputOutput.
  mask
    - defines what attributes are set.
  attributes
    - different window attributes.

- RETURN VALUE

      ID of the newly created window on success. None on failure.

- DESCRIPTION

      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/create_visual_gc()

- NAME

  create_visual_gc()

- SYNOPSIS

      GC      create_visual_gc( ASVisual *asv, Window root,
                                unsigned long mask, XGCValues *gcvalues );

- INPUTS

  asv
    - pointer to the valid ASVisual structure.
  root
    - Window ID of the root window of destination screen
  mask,
    gcvalues - values for creation of new GC - see XCreateGC() for details.

- RETURN VALUE

      New GC created for regular window on success. NULL on failure.

- DESCRIPTION

      create_visual_gc() will create temporary window for the ASVisual
      specific depth and Visual and it will then create GC for such window.
      Obtained GC should be good to be used for manipulation of windows and
      Pixmaps created for the same ASVisual.

libAfterImage/create_visual_pixmap()

- NAME

  create_visual_pixmap()

- SYNOPSIS

      Pixmap  create_visual_pixmap( ASVisual *asv, Window root,
                                    unsigned int width, unsigned int height,
                                    unsigned int depth );

- INPUTS

  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.

- RETURN VALUE

      ID of the newly created pixmap on success. None on failure.

- DESCRIPTION

      create_visual_pixmap() will perform sanity checks on passed
      parameters, and attempt to create pixmap for the specified ASVisual,
      root and depth.

libAfterImage/create_visual_ximage()

- NAME

  create_visual_ximage()

- SYNOPSIS

      XImage* create_visual_ximage( ASVisual *asv,
                                    unsigned int width, unsigned int height,
                                    unsigned int depth );

- INPUTS

  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.

- RETURN VALUE

      pointer to newly created XImage on success. NULL on failure.

- DESCRIPTION

      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.

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