KDE Plasma 5.22 Will Support Direct Scan-Out For Full-Screen Games / Apps

[oiaohm]

correct me if i'm wrong, but with x11 can you at least disable composition before you launch a game? with wayland i don't think you have that option. i know with xfce i just keep it disabled. i play a lot of games and with amdgpu, i actually don't notice as much screen tearing like i use to when i had nvidia.

This is only start of story.

Yeah, but disabling the compositor is more of a hack than a proper solution.

Yes this is more than true worse its not in fact a solution at all.
https://www.phoronix.com/scan.php?pa...-Desktop-Lease

Something to be aware of is above drm lease. This requires you applications to talk direct libdrm as in not be a X11 application. Virtual Reality is insanely latency sensitive turns out X11 server with compositor disabled is still introducing at least a frame of latency.

Using DMA BUF as the open source gpu drivers provide allows zero copy actions between the application, compositor and gpu. Please note the X11 protocol for writing X11 compositor is not designed to use zero copy operations and the bare metal X11 server and protocol is not designed for zero copy operations. Why when the X11 protocol was designed zero copy operations could not be done safely. DMA BUF has meta stuff important to passing buffers around safely.

Funny thing is that despite all of the criticism Xorg receives, I still have better vsync with it + Mesa than on Windows with proprietary driver. It's nice that Wayland offers advantages, but multi-monitor users are a minority and when you run the game on all displays without tilt, vsync still works as expected (including VRR when all displays support it). So let's not always trample down Xorg when it doesn't deserve it, there are still enough cases remaining where this is justified.

Proton fullscreen hack btw. automatically resumes KWin's compositing when alt + tabbing out of a game and you can use it in wine-tkg as well. Thus I don't miss unredirect too much.

This is missing the problem. Wayland compositor design fixes something when you can get decent drivers as in able to use zero copy operations by DMA BUF between applicaiton, compositor and gpu so provides advantages for those on single monitors doing something latency sensitive if Wayland compositor is written well in theory.

Xorg X11 server for bare metal is unlikely to receive any more major releases because no company/entity is willing to fund this development going forwards. The idea that you can justify X11 usage on bare metal going forwards is not exactly true. What we have is legacy cases using X11 on bare metal they have to be though as deprecated solutions unless someone comes forwards to fund X11 server development on bare metal because the security of those solutions is only going to get worse thinking X11 was not great to start off with.

[Grim85]

We still have kwin-lowlatency

Kwin has been refactored in 5.21, it now has a low latency mode, and the fps limit has been ditched. You shouldn't need kwin-lowlatency anymore.

[andreduartesp]

Yeah, but disabling the compositor is more of a hack than a proper solution.
It's like a water heater without a cold option: to get cold water, move the pipe out and don't pass it through the heater instead of just using the cold passthrough directly from the heater.

I do not want to lose animations/eye candy when going back to the desktop.

But you don't lose it, when the window who asked for disabling composite loose focus, the compositing is enabled by Kwin. You don't even notice the composite was disabled in the first place.

[tildearrow]

But you don't lose it, when the window who asked for disabling composite loose focus, the compositing is enabled by Kwin.

Not always. SDL2 apps are a big example.
Whenever I start up an SDL2 app the compositor disables by default, regardless of whether the app is full-screen or not.

You don't even notice the composite was disabled in the first place.

Sorry but I do notice. When I unfocus I see a few frames of an uncomposited desktop because it takes a while to be enabled again.
With unredirection (compositing suspend instead of disable) this does not happen.