(In reply to Diego Viola from comment #65)
> Just to make it a bit more clear:
> 
> If I set that environment variable while I'm already on X:
> 
> export MESA_EXTENSION_OVERRIDE="-GL_NV_texture_barrier"
> 
> It has no effect on Xephyr (from current git master), i.e. xterm still shows
> the bug.

xterm still shows the bug in Xephyr from git if that environment was set later
(while X was running).

Works fine with both (Xephyr git and X) if the environment variable was set
before startx.

Please let me know if you have more questions.