[Mesa-dev] [PATCH] __DRIimage: Add formats with implied swizzling

[Eric Anholt]

Kristian Høgsberg <krh at bitplanet.net> writes:

> When we sample U and V from YUYV buffers, U and V ends up in G and A
> in the shader.  Instead of pushing this to the application, just swizzle
> U and V to R and G and set B to 0 and A to 1.

Those fields are controlled by EXT_texture_swizzle.  We probably
shouldn't mess with the defaults of GL state.

Other nastiness where we're hiding the actual format from the user for
GL's depth sampling has been done with a switch in
brw_populate_sampler_prog_key_data().  But if we're actually just doing
RGBA underneath, it seems like suggesting to people that they sample
RGBA and swizzle in their shaders would avoid code and be reasonable.
It's what GL resolved for the depth sampling, we just still support GL
2.0.
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