<li>LIBGL_ALWAYS_INDIRECT - forces an indirect rendering context/connection.
<li>LIBGL_ALWAYS_SOFTWARE - if set, always use software rendering
<li>LIBGL_NO_DRAWARRAYS - if set do not use DrawArrays GLX protocol (for debugging)
+<li>LIBGL_SHOW_FPS - print framerate to stdout based on the number of glXSwapBuffers
+ calls per second.
</ul>
<h2>Gallium environment variables</h2>
<ul>
+<li>GALLIUM_HUD - draws various information on the screen, like framerate,
+ cpu load, driver statistics, performance counters, etc.
+ Set GALLIUM_HUD=help and run e.g. glxgears for more info.
<li>GALLIUM_LOG_FILE - specifies a file for logging all errors, warnings, etc.
rather than stderr.
<li>GALLIUM_PRINT_OPTIONS - if non-zero, print all the Gallium environment