[Dri-devel] Detecting software fallbacks

[Ove K. <ov...@tr...>]

(Resent because of suspicions that sourceforge is dropping mail from my
other account)

>From recent discussion on the list, it is my understanding that some DRI
drivers that implement (or will implement) EXT_texture_env_combine will
have numerous software fallbacks. Is it possible to add a way for
applications to detect when a texture environment will cause a software
fallback? Direct3D has a mechanism called "ValidateDevice" for this
purpose; you set up an environment and call ValidateDevice to see if the
hardware can do it without fallbacks.

Currently the only way I see to know such cases with DRI would be to use
glGetString with GL_VENDOR and GL_RENDERER and have a table of hardware
capabilities in every application that really need to know this, which
is not very flexible and is hard to update when DRI gets new drivers and
old drivers get new features. And I hear some Linux games already have
to do this.

Seems to me that a driver query would be a much better solution. Would
it be feasible to implement such a mechanism?

(Of course, there are other things that could cause a fallback (e.g.
stippling), but that's a smaller problem.)