+
+
+int
+get_bits_per_pixel(Display *dpy, int depth)
+{
+ unsigned i = 0;
+ int count, result;
+ XPixmapFormatValues *formats = XListPixmapFormats(dpy, &count);
+
+ /* XCreateImage calls _XGetBitsPerPixel to figure this out, but that function
+ is private to Xlib.
+
+ For some reason, _XGetBitsPerPixel tries a hard-coded list of depths if
+ it doesn't find a matching pixmap format, but I (Dave Odell) couldn't
+ find any justification for this in the X11 spec. And the XFree86 CVS
+ repository doesn't quite go back far enough to shed any light on what
+ the deal is with that.
+ http://cvsweb.xfree86.org/cvsweb/xc/lib/X11/ImUtil.c
+
+ The hard-coded list apparently was added between X11R5 and X11R6.
+ See <ftp://ftp.x.org/pub/>.
+ */
+
+ if (!formats) return 0;
+
+ for (;;)
+ {
+ if (i == (unsigned)count)
+ {
+ result = 0;
+ break;
+ }
+
+ if (formats[i].depth == depth)
+ {
+ result = formats[i].bits_per_pixel;
+ break;
+ }
+
+ ++i;
+ }
+
+ XFree (formats);
+ return result;
+}