-/* xscreensaver, Copyright (c) 1992 Jamie Zawinski <jwz@lucid.com>
+/* xscreensaver, Copyright (c) 1992 Jamie Zawinski <jwz@mcom.com>
*
* Permission to use, copy, modify, distribute, and sell this software and its
* documentation for any purpose is hereby granted without fee, provided that
#include <X11/Xlib.h>
#include <X11/Xos.h>
-extern void screenhack_usleep ();
+#if __STDC__
+# define P(x)x
+#else
+# define P(x)()
+#endif
+
+extern int get_visual_class P((Display *, Visual *));
+extern void screenhack_usleep P((int));
#define usleep screenhack_usleep
#define MAX_COLORS 4096
Colormap cmap, into_cmap;
{
int i;
- ncolors = CellsOfScreen (DefaultScreenOfDisplay (dpy));
+ Screen *screen = DefaultScreenOfDisplay (dpy);
+ Visual *visual = DefaultVisualOfScreen (screen);
+ Window window = RootWindowOfScreen (screen);
+ int vclass = get_visual_class (dpy, visual);
+
+ ncolors = CellsOfScreen (screen);
+
+ /* If this is a colormap on a mono visual, or one with insanely many
+ color cells, bug out. */
if (ncolors <= 2 || ncolors > MAX_COLORS)
return 0;
+ /* If this is a non-writable visual, bug out. */
+ if (vclass == StaticGray || vclass == StaticColor || vclass == TrueColor)
+ return 0;
+
if (! into_cmap)
- into_cmap = XCreateColormap (dpy, RootWindow (dpy, DefaultScreen (dpy)),
- DefaultVisual (dpy, DefaultScreen (dpy)),
- AllocAll);
+ into_cmap = XCreateColormap (dpy, window, visual, AllocAll);
if (! cmap)
cmap = DefaultColormap (dpy, DefaultScreen (dpy));
for (i = 0; i < ncolors; i++)