DISPLAY
to get the default host, display, and screen number.
xscreensaver-gl-visual6
Figure out which x visual to use for gl programs
Usage
xscreensaver-gl-visual [--display
host:display.screen]
Overview
This program prints the ID of the visual that should be used for proper operation of OpenGL programs. This program only exists so that the xscreensaver(1) daemon does not need to link against the OpenGL library.