Add gamescope-reshade Wayland interface

[wheaney]

Implemented per the suggestion by @Joshua-Ashton in #1082

[wheaney]

This wasn't working without the vblank check due to the logic on line 7891:

bShouldPaint = vblank && ( hasRepaint || hasRepaintNonBasePlane || bForceSyncFlip );

Note that this will ignore our bForceRepaint request (that gets passed via bForceSyncFlip) if vblank is false. But by the time this happens, our original force repaint request is lost because g_bForceRepaint.exchange(false) has already been called. So any time this line would get hit while vblank is false will result in the request getting lost. My update makes it so we don't reset the g_bForceRepaint request unless it will actually trigger a repaint.

[misyltoad]

Yeah, makes sense for force repaint to check for vblank.

[misyltoad]

Is there a client on this interface? I wonder if this is better served by gamescopectl and a gamescope::Command. That would make a client just work(tm).

[wheaney]

I've got a working client in this branch of my XR driver.

Can you expand on the gamescopectl and gamescope::Command suggestion?

Edit - just found this comment you made in our last conversion that led me down this path:

Steam uses the Gamescope Control protocol. Feel free to make a Gamescope Shader protocol or whatever.

[wheaney]

@Joshua-Ashton just waiting on more details.

[wheaney]

@Joshua-Ashton I'd love to get some more guidance or review feedback on this PR. I've got this integration working end-to-end locally with my own client, so it would be nice to wrap up or re-work if needed.

[misyltoad]

I thought more about it, and this is fine as-is really. It might be nice if you used the new stuff in src/WaylandServer to implement it though. It will probably end up a bit cleaner.

[wheaney]

@Joshua-Ashton Okay, thanks. Let me know what the next steps are for this.

[misyltoad]

I would like the Wayland server parts to use the new helpers there so we aren't adding more stuff for me to rewrite. Other than that it's fine.

[wheaney]

@Joshua-Ashton I think the latest commit covers what you've requested.

[wheaney]

@Joshua-Ashton Thanks for merging this! How often does the Preview channel get the latest gamescope updates? And what's the process and typical timeline for changes to migrate through the SteamOS channels? Is there documentation around that process?

[misyltoad]

It depends a lot, Main gets updated pretty regularly, and Beta whenever think we are ready to push on shipping Main.

Timelines are all over, and semi-made up.