Add option to use KWIN_USE_INTEL_SWAP_EVENT and patch it

[xalt7x]

Last year during discussion of Roman Glig's compositing overhaul users noticed that environment variable KWIN_USE_INTEL_SWAP_EVENT dramatically improved latency. But this option also brings problems when you or some application disable compositor. Roman fixed it with commit Reset buffer swap state on stop which was also reverted. I tried it only with regular KWin but KWin-lowlatency may also benefit from it.

[tildearrow]

This could be a good candidate for a VBlank detection method. Thank you for the suggestion.

[xalt7x]

@tildearrow So I'm still applying patches to kwin-lowlatency for this option

Patch to enable it just as binary tweak.. "Reset buffer swap state on stop" was adjusted to kwin-lowlatency and I'm not sure if it's correct. Could you please review and merge it so users can safely use KWIN_USE_INTEL_SWAP_EVENT environment variable? Thanks!

Both patches (for 5.18) attached bellow: glx_intel_swap_eventforkwin-lowlatency.tar.gz

[An4cl3t0]

@tildearrow So I'm still applying patches to kwin-lowlatency for this option

Patch to enable it just as binary tweak.. "Reset buffer swap state on stop" was adjusted to kwin-lowlatency and I'm not sure if it's correct. Could you please review and merge it so users can safely use KWIN_USE_INTEL_SWAP_EVENT environment variable? Thanks!

Both patches (for 5.18) attached bellow: glx_intel_swap_eventforkwin-lowlatency.tar.gz

In standard KWin it freezes for me when I use MPV to play a file with KWIN_USE_INTEL_SWAP_EVENT, is the patch correcting that?

[tildearrow]

Closing as 5.22+ implements it (apparently).