[Piglit] [PATCH 1/3] fbo-blending-formats: Enable testing for channels with 0 bits of data.

[Carl Worth]

Marek Olšák <maraeo at gmail.com> writes:
> The series is: Reviewed-by: Marek Olšák <maraeo at gmail.com>

Thanks for the review, Marek.

> I hope other tests are not broken by this change in the util code.

That's a good point. I do expect my commits to cause some test results
to change from PASS to FAIL, (since the whole point of this exercise was
to improve the tests to catch some bugs I know exist in Mesa). But I
need to be careful I'm not introducing any new bugs in tests.

The original bug I was trying to exercise is the "DST_ALPHA bug" in i965
as fixed in my recent commit 258453716f001eab1288d9976521 to mesa.

After I changed the tests I also noticed some failures due to a "float
ReadPixels bug". This is where glReadPixels give values other than 1.0
for the alpha channel when reading from a floating-point format without
an alpha channel. I haven't chased down the cause of this bug in mesa
yet, but I did open a new bug report for it here:

	glReadPixels doesn't smash alpha to 1.0 with RGB float formats
	https://bugs.freedesktop.org/show_bug.cgi?id=59442

From doing a run over quick.tests (on i965 SNB) now I see the following
8 new test failures after my patches:

ARB_texture_rg/fbo-blending-formats
ARB_texture_rg/fbo-blending-formats-float

  These two look like they have failures only with DST_ALPHA. These are
  apparently not fixed with my recent commit to mesa master. This could
  require some additional fixing to the expected values in the tests
  like I did in patch 3/3.

ARB_texture_float/fbo-blending-formats
ARB_texture_float/fbo-colormask-formats
EXT_framebuffer_object/fbo-blending-formats
EXT_texture_snorm/fbo-blending-formats

  These four all look like the "float ReadPixels bug", (with a little
  DST_ALPHA-specific bugginess thrown in as well). So if I can clear up
  the DST_ALPHA stuff, these are expected failures.

EXT_texture_snorm/fbo-colormask-formats

  This one looks strictly like the "float ReadPixels" bug. So that's an
  expected failure.

EXT_texture_snorm/fbo-alphatest-formats

  For this one, I'm not familiar with the test yet, and the output from
  the failure doesn't look like anything I recognize:

	Using test set: GL_EXT_texture_snorm
	  FAIL when testing window result, 1: 0.2 < 0.25.
	  FAIL when testing window result, 3: 0.6 > 0.55.
	  FAIL when testing window result, 4: 0.9 > 0.1.
	...

  So I'll need to investigate that further before I know whether it's an
  expected failure due to a mesa bug or a bug I introduced to the test.

I'll look into all of the above a bit more closely and wait to push the
piglit changes until all of the introduced failures are known to
correspond to known bugs.

-Carl
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