GL-renderer can produce straight alpha framebuffers on some platforms,
and headless-backend can request that using "output-straight-alpha"
config option.
In this patch we use that to add a sanity test for GL-renderer's
straight alpha implementation. Basically, it ensures that no matter if
renderer is producing straight or premult alpha framebuffers after
blending, the results should be the same when the background is opaque.
To extend the tests and exercise the DRM-backend implementation we'd
need more work on:
- VKMS, to emulate that it doesn't support alpha premultiplied fb's.
- Weston, adding support for using ConfigFS on the test suite.
Signed-off-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>
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