Environment Variables
Mesa supports the following environment variables:
- MESA_DEBUG - if defined, error messages are printed to stderr
 - MESA_NO_DITHER - disable dithering, overriding glEnable(GL_DITHER)
 - MESA_RGB_VISUAL - specifies the X visual and depth for RGB mode (X only)
 - MESA_CI_VISUAL - specifies the X visual and depth for CI mode (X only)
 - MESA_BACK_BUFFER - specifies how to implement the back color buffer (X only)
 - MESA_PRIVATE_CMAP - force aux/tk libraries to use private colormaps (X only)
 - MESA_GAMMA - gamma correction coefficients (X only)
 - MESA_XSYNC - enable synchronous X behavior (for X debugging only)