Partial fix for issue #6427 - GPU screenshot support on D3D11

[miguedevel]

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Description

This is a partial fix for issue #6427 . I say partial because only D3D11 screenshot support is implemented.
Also, this method produces incorrect result if using HDR so it will produce nothing instead.
I tested this on Windows 11 and Windows 10 one with NVIDIA GPU and another with AMD GPU.
Does this affect Xbox One or UWP???

Related Issues

Issue #6427
Issue #14432 (not tested)

Related Pull Requests

[Any other PRs from related repositories that might be needed for this pull request to work]

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[LibretroAdmin]

The D3D11 driver is also used by UWP/Xbox if that's what you mean.

Also it would be nice if we could figure out a way to get it working with HDR too. This could be a good first step towards that though.

[hizzlekizzle]

IIRC, Vulkan screenshots don't work with HDR, either.

[miguedevel]

Vulkan does support HDR screenshots and according to the code /* Hdr readback is implemented through format conversion on the GPU */ /shrug
EDIT: With that, I mean it creates a proper non HDR screenshot.

I tried a naive way of just bit-shifting from 10 bits to 8 but it produces a very dim/contrast-less image.

[LibretroAdmin]

I'll merge this for now.

I do hope though you'll take the initiative of researching a solution for HDR since it's pretty important in the long run and increasingly more and more ppl will run RetroArch with it enabled.