[Mesa-dev] Print error message when switching to indirect rendering

[Carl Worth]

I recently had a problem with a dri driver failing to load, (it turned
out to be a case of the driver being built for 64-bit, but running a
32-bit application).

At the time, mesa switched over to indirect rendering without me
realizing it at all. This left me quite confused. Finally, a kind
friend pointed me to LIBGL_DEBUG=verbose and I was able to diagnose
the problem.

I think mesa could have been that friend first. Here's a patch series
to introduce a new CriticalErrorMessageF macro which will print a
message even if LIBGL_DEBUG is unset, (but, like ErrorMessageF, will
still silence the message if LIBGL_DEBUG is set to quiet).

Then, the error messages regarding switching to indirect and
software-direct rendering are moved from ErrorMessageF to
CriticalErrorMessageF.

I think this makes mesa a bit kinder when things go wrong, without
spewing excessive noise in common cases. Any diagreement? Are their
other obvious candidates for CriticalErrorMessageF?

-Carl