[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:
> On Wed, Jan 16, 2013 at 12:07 AM, Carl Worth <cworth at cworth.org> wrote:

>> 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.

These DST_ALPHA failures did point to a problem in one of my patches
(3/3). I had broken the test to start expecting non-zero color values
for channels with no bits, (such as the blue channel in an RG
format). I've fixed this with a new v.2 of patch 3/3.

I also sent a v.2 of patch 2/3 that extends its fix, (so that DST_ALPHA
is tested for windows as well as fbos).

>> 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:
...
> The first FAIL report says that the input pixel value was 0.2, the
> function was GL_LESS, and the alpha ref. value was 0.25, and the
> driver/hardware did the opposite (discarded the pixel).

Thanks for the explanation. This is the last remaining failure to block
the patch series in my view. (With v.2 of patch 3/3 all other failures
look like real bugs where alpha is not being correctly smashed to 1.0).

For this test, the only failures introduced by my patch are with
alpha-only formats, (GL_ALPHA16_SNORM, GL_ALPHA8_SNORM, and
GL_ALPHA_SNORM), and then only when testing on a window.

From my reading of the test, it's not actually doing valid testing for
the case of an alpha-only format, (since it's trying to use an RGB pixel
probe to distinguish between pass and failure).

Though I don't know why it still passes in the fbo case.

Before my patch, these failing cases were basically not being executed
at all, (since the tolerance was set to a value that effectively
disabled the test).

Eric, do you have a suggestion for how to fix this?

-Carl

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