Re: GdkColor and GdkGC question

[Havoc Pennington <hp redhat com>]

Andrei Zmievski <andrei ispi net> writes:
> 
> When I do gdk_gc_get_values() to retrieve the GC values, the
> 'foreground' value which is a GdkColor, for example, only has pixel
> member set properly - red, green, and blue are not. What is the proper
> way to obtain RGB values for a certain pixel value?
> 

>From GTK 2, can cut-and-paste into GTK 1.2 as far as I see, but have
to include gdk/gdkx.h.

void
gdk_colormap_query_color (GdkColormap *colormap,
                          gulong       pixel,
                          GdkColor    *result)
{
  XColor xcolor;
  GdkVisual *visual;

  g_return_if_fail (GDK_IS_COLORMAP (colormap));
  
  visual = gdk_colormap_get_visual (colormap);

  switch (visual->type) {
  case GDK_VISUAL_DIRECT_COLOR:
  case GDK_VISUAL_TRUE_COLOR:
    result->red = 65535. * (double)((pixel & visual->red_mask) >>
  visual->red_shift) / ((1 << visual->red_prec) - 1);
    result->green = 65535. * (double)((pixel & visual->green_mask) >>
  visual->green_shift) / ((1 << visual->green_prec) - 1);
    result->blue = 65535. * (double)((pixel & visual->blue_mask) >>
  visual->blue_shift) / ((1 << visual->blue_prec) - 1);
    break;
  case GDK_VISUAL_STATIC_GRAY:
  case GDK_VISUAL_GRAYSCALE:
    result->red = result->green = result->blue = 65535. *
  (double)pixel/((1<<visual->depth) - 1);
    break;
  case GDK_VISUAL_STATIC_COLOR:
    xcolor.pixel = pixel;
    XQueryColor (GDK_DISPLAY (), GDK_COLORMAP_XCOLORMAP (colormap),
  &xcolor);
    result->red = xcolor.red;
    result->green = xcolor.green;
    result->blue =  xcolor.blue;
    break;
  case GDK_VISUAL_PSEUDO_COLOR:
    result->red = colormap->colors[pixel].red;
    result->green = colormap->colors[pixel].green;
    result->blue = colormap->colors[pixel].blue;
    break;
  default:
    g_assert_not_reached ();
    break;
  }
}