🚀 go-pugleaf

My program loads 24-bit textures and displays them with Mesa on XWindows
with a Voodoo2 card.  I'm using double-buffering and depth buffering in RGBA
mode (not color index).  For some reason, I am losing a lot of my colors.
For example, if I have a texture with 8 similar shades of gray, many will
appear as exactly the same color.  Only 2 or 3 shades will be rendered for
all 8.  Since my program involves subtle contrast variations, this is a huge
problem.  I thought I would be running in a true color mode since X is set
to 24 or 32 bit color depth, but apparently this isn't the case.  Why does
this happen?  How can I fix it?

Posted below is some of the code, such as the colormap initialization, that
may cause the problem.

Thanks for any help, and please mail responses to rascal@tseinc.com ,
Benjamin Burack





int configuration[] = {GLX_DOUBLEBUFFER, GLX_RGBA, GLX_DEPTH_SIZE, 16,
None};

void main(int argc, char **argv)
{
    XVisualInfo    *vi;
    XSetWindowAttributes swa;
    XWMHints       *wmHints;
    Atom            wmDeleteWindow;
    GLXContext      cx;

<snip>


    /*** find an appropriate visual and a colormap for it ***/
    /* find an OpenGL-capable RGB visual with depth buffer */
    if (!bDoubleBuffer) goto SingleBufferOverride;
    vi = glXChooseVisual(pDisplay, DefaultScreen(pDisplay), configuration);
    if (vi == NULL) {
      SingleBufferOverride:
        vi = glXChooseVisual(pDisplay, DefaultScreen(pDisplay),
&configuration[1]);
        if (vi == NULL)
            fatal_error("no appropriate RGB visual with depth buffer");
        bDoubleBuffer = GL_FALSE;
    }
    cmap = getColormap(vi);

<snip>

    /*** create an OpenGL rendering context  ***/
    cx = glXCreateContext(pDisplay, vi, /* no sharing of display lists */
NULL,
                           /* direct rendering if possible */ GL_TRUE);
    if (cx == NULL) fatal_error("could not create rendering context");

<snip>

}

Colormap getColormap(XVisualInfo* vi)
{
  Status           status;
  XStandardColormap* standardCmaps;
  Colormap         cmap;
  int              i, numCmaps;

  status = XmuLookupStandardColormap(pDisplay, vi->screen, vi->visualid,
vi->depth, XA_RGB_DEFAULT_MAP, FALSE, TRUE);

  if (status == 1) {
    status = XGetRGBColormaps(pDisplay, RootWindow(pDisplay, vi->screen),
         &standardCmaps, &numCmaps, XA_RGB_DEFAULT_MAP);
    if (status == 1)
      for (i = 0; i < numCmaps; i++)
 if (standardCmaps[i].visualid == vi->visualid) {
   cmap = standardCmaps[i].colormap;
   XFree(standardCmaps);
   return cmap;
 }
  }
  cmap = XCreateColormap(pDisplay, RootWindow(pDisplay, vi->screen),
    vi->visual, AllocNone);
  return cmap;
}