[Piglit] [PATCH] New testsuite for ARB_color_buffer_float (v2)

[Luca Barbieri]

This in an updated version of the test I posted, now split into 8 tests
sharing a common header file.

It now features testing of multiple render targets and fog.

Test output logs and results on GeForce 8xxx, GTX 2xx or ideally GTX 4xx
with the proprietary drivers would be really welcome.

The files are put in "spec/arb_color_buffer_float" with the idea of
starting a convention of writing testsuites for each new extension
to be implemented in Mesa, putting it in "spec/<extension_name>".

The tests now fail on any bugs in the default mode.
If "-xfail" is passed, then known bugs on ATI and nVidia will be ignored,
and all tests will then succeed.

The driver bugs don't seem due (solely) to hardware limitations, but may
be due to software fallbacks being improperly implemented.

There are two areas where the specification seems unclear, as far as I
understand it.

I'm not sure what the process to ask for clarification is, and suggestions
would be welcome here.

This first issue is whether, when fragment clamping is set to FIXED_ONLY
and the FBO has some fixed-point and some floating-point buffers attached,
gl_FragData[n] is never clamped, or is clamped only for the fixed point
buffers.

Note that while blending on fixed-point clamps the color anyway, alpha
test and polygon smoothing happen before blending, and should be affected
by whether gl_FragData[n] is clamped or not.