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>How do I use color allocation?</A
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>One of the nice things about GDK is that it's based on
top of Xlib; this is also a problem, especially in the area of
color management. If you want to use color in your program
(drawing a rectangle or such, your code should look something
like this:</P
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>{
GdkColor *color;
int width, height;
GtkWidget *widget;
GdkGC *gc;
...
/* first, create a GC to draw on */
gc = gdk_gc_new(widget->window);
/* find proper dimensions for rectangle */
gdk_window_get_size(widget->window, &width, &height);
/* the color we want to use */
color = (GdkColor *)malloc(sizeof(GdkColor));
/* red, green, and blue are passed values, indicating the RGB triple
* of the color we want to draw. Note that the values of the RGB components
* within the GdkColor are taken from 0 to 65535, not 0 to 255.
*/
color->red = red * (65535/255);
color->green = green * (65535/255);
color->blue = blue * (65535/255);
/* the pixel value indicates the index in the colormap of the color.
* it is simply a combination of the RGB values we set earlier
*/
color->pixel = (gulong)(red*65536 + green*256 + blue);
/* However, the pixel valule is only truly valid on 24-bit (TrueColor)
* displays. Therefore, this call is required so that GDK and X can
* give us the closest color available in the colormap
*/
gdk_color_alloc(gtk_widget_get_colormap(widget), color);
/* set the foreground to our color */
gdk_gc_set_foreground(gc, color);
/* draw the rectangle */
gdk_draw_rectangle(widget->window, gc, 1, 0, 0, width, height);
...
}</PRE
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