[Piglit] [PATCH] add GL_ARB_sample_locations

Mon May 7 16:19:11 UTC 2018

I have already tested it with NVIDIA's driver. It fails because
gl_SamplePosition does not reflect the programmed sample locations due to a
bug in the driver.

It also fails because and 16x and 32x MSAA tests fail. I could not find
anything wrong with the test itself, so I assumed it was a bug in the driver
or because of some detail in how the MSAA modes are implemented.