<li>MESA_EXTENSION_OVERRIDE - can be used to enable/disable extensions.
A value such as "GL_EXT_foo -GL_EXT_bar" will enable the GL_EXT_foo extension
and disable the GL_EXT_bar extension.
+<li>MESA_GLSL - <a href="shading.html#envvars">shading language options</a>
</ul>
<p>
<p>
The <b>MESA_GLSL</b> environment variable can be set to a comma-separated
-list of keywords to control some aspects of the GLSL compiler:
+list of keywords to control some aspects of the GLSL compiler and shader
+execution. These are generally used for debugging.
</p>
<ul>
<li>dump - print GLSL shader code to stdout at link time
<li>nopt - disable compiler optimizations
<li>opt - force compiler optimizations
<li>uniform - print message to stdout when glUniform is called
+<li>nopvert - force vertex shaders to be a simple shader that just transforms
+ the vertex position with ftransform() and passes through the color and
+ texcoord[0] attributes.
+<li>nopfrag - force fragment shader to be a simple shader that passes
+ through the color attribute.
</ul>
<p>
Example: export MESA_GLSL=dump,nopt