I noticed Xprint has a couple of new tools, xdpr and xpr.  I decided to test
them, testing OpenGL support at the same time by using glxgears. My procedure is
this:
1) run glxgears
2) capture the window image with "xwd -name glxgears > xwd.out"
3) check the xwd image is good with "xwud -in xwd.out" (yes, it's fine)
4) print to postscript files with "xpr xwd.out > xwd.ps"
5) check postscript image is good with "gv xwd.ps" (no, it's a blank box)

The postscript file produced by xpr is a black box in the top right-hand corner
of a white page.  The dimensions of the box look about right, compared against
the size of the glxgears window, but the box is blank (black), instead of
showing the three coloured gears on a black background (as seen with xwud).

Likewise "xdpr -name glxgears" prints a black box on a sheet of paper.

This is running Xprint 0.1.0alpha1, against an XFree86 4.3.0 Xserver.