This is GdkRgb.
Brief notes on using GdkRgb:
- You must call gdk_rgb_init before using any GdkRgb functionality. Inside widgets, it's entirely reasonable to place the call in the class_init method.
- GdkRgb tries to use the system default visual and colormap, but doesn't always succeed. Thus, you have to be prepared to install the visual and colormap generated by GdkRgb. The following code sequence (before any widgets are created) should work in most applications:
gdk_rgb_init ();
gtk_widget_set_default_colormap (gdk_rgb_get_cmap ()); gtk_widget_set_default_visual (gdk_rgb_get_visual ());
You can also push the colormap and visual, but that requires extra care.
3. You can set the threshold for installing colormaps with gdk_rgb_set_min_colors (). The default is 5x5x5 (125). If a colorcube of this size or larger can be allocated in the default colormap, then that's done. Otherwise, GdkRgb creates its own private colormap. Setting it to 0 means that it always tries to use the default colormap, and setting it to 256 means that it always creates a private one. Note, however, that setting it to 0 doesn't let you get away with ignoring the colormap and visual - a colormap is always created in grayscale and direct color modes, and the visual is changed in cases where a "better" visual than the default is available.
4. That done, the API is extremely simple. gdk_rgb_gc_set_foreground sets the foreground color based on a simple 24-bit RGB color code. gdk_draw_rgb_image draws a 24 bit RGB image into the drawable. The arguments should be straightforward except for dither - GDK_RGB_DITHER_NONE disables dithering, _MAX enables dithering if supports (i.e. in most modes other than 24bpp ones), and _NORMAL selects a default (usually on at 8bpp and off at 16bpp).
5. I've provided a few other functions that may improve performance for image types other than 24bpp packed rgb. Of these, the gray one on static gray visuals is the only one that gives a really large performance jump.
6. Take a look at testrgb for notes on how to configure. Briefly:
+ include gdkrgb.c, gdkrgb.h, and gdkrgbstub.c in your source tree.
+ include gdkrgb.c and gdkrgb.h as EXTRA_DIST in the Makefile.am.
+ include gdkrgbstub.c in the program_SOURCES in the Makefile.am.
+ do an AC_C_BIGENDIAN test in configure.in.
+ include this code in all files that use gdk_rgb functions:
#ifndef GTK_HAVE_FEATURES_1_1_0
#include "gdkrgb.h"
#endif
Raph Levien