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Xwayland: Implement linux_dmabuf v4 feedback support

Austin Shafer requested to merge ashafer/xserver:master into master

This change adds support for linux_dmabuf v4, which added per-surface dmabuf feedback. In the future this will allow scanout modifiers that a compositor advertises to be delivered to X11 apps.

Implementation overview

  • clients will use the DRI3SetDRMDeviceInUse event to give Xwayland a hint about what device they want specific modifiers for on a particular window.
  • Xwayland will record tranches advertised with linux_dmabuf_feedback by the compositor, both default feedback and for each xwl_window.
  • When the client calls GetSupportedModifiers, Xwayland will return the default feedback's modifiers in the screen modifiers return parameter, and the per-xwl_window feedback's modifiers in the window modifiers return parameter.
  • If Xwayland has received new feedback from the compositor, it will send the PresentCompleteModeSuboptimalCopy flag in PresentCompleteNotify to tell the client to re-query modifiers.

I've tried to implement it in small chunks to make it easier to review, hence why there is a commit that adds a skeleton of the wayland event handling and later commits add implementations. If this is a problem I can squash it before merging.

Related MRs

This series is dependent on the DRI3 changes listed above.


Tested with wlroots+sway and weston, both on Nvidia. Using this sway MR I tested that glxgears was notified through PresentCompleteNotify when per-surface feedback is updated while going fullscreen and could update it's modifiers.

Please let me know if there is anything I can do to improve this series, or if there are any potential problems I may not have anticipated.

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