When rendering 60fps on a 60Hz display every frame takes approximately 16ms to render. Then you have to add TV latency that’a probably around 20ms unless you have a very nice OLED TV. Wireless controller latency is around 8ms I think? Then your imperfect human brain adds even more latency especially when you’re tired after work. That 3ms is not perceivable. Make that 5ms even. Nobody would be able to tell a difference in a blind test.
gamescope is a custom wayland compositor that Valve built for gaming...
In steam big picture mode there is no xwayland or anything, just gamescope.
What you are reading from the readme notes that it calls into xwayland only when gamescope (wayland compositor) is nested within another compositor (say kwin or mutter).
gamescope itself is wayland only, and when run on SteamOS is has no xwayland latency...
What you're saying doesn't make any sense. Gamescope is essentially a XWayland-only compositor (with some basic xdg-shell support that's disabled by default). All games on SteamOS go through XWayland.
It doesn't yet mean that it suffers from the latency measured in the article, as the problem could very well be in something else, such as how KWin integrates with XWayland or how GPU drivers interact with it (especially that Nvidia drivers have a history of making XWayland suffer).
gamescope absolutely can have Xwayland child panes & this is currently the default on SteamOS running games with Proton, unless PROTON_ENABLE_WAYLAND=1 is set in the game options.
>Avoid XWayland. It added 3.13 ms of latency, more than all other effects combined.