kwin-lowlatency
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tildearrow
Multiple monitors with different refresh rates
I am very excited about this project. Upstream kwin does bad job when it deals with multiple monitors of different refresh rates. They get locked down to lowest available refresh rate. Do you plan to solve this and allow each monitor run at it's own refresh rate? I found that Option "TearFree" "true" option somewhat remedies the situation but it is not perfect. There still is some stuttering, albeit almost inperceivable.
In a future it may be possible to do this, but the problem is that I feel this will require a major rewrite of the rendering/sync code to be able to handle multiple monitors. Furthermore, if I recall correctly most graphics cards only support synchronizing to a single monitor (which is why e.g. NVIDIA has an environment variable called __GL_SYNC_DISPLAY_DEVICE to set this monitor). It is likely I am wrong, however.
But I will be considering this for an upcoming version.
Sounds like this would get real ugly. What if i have 144hz and 60hz monitor, would it be any simpler to run one of them at 120hz and another on 60hz and have them in sync while 60hz monitor would skip every other frame?
It wouldn't be that simpler. Even if your other display runs at half the framerate there still are minor random timing differences that may cause lots of stuttering for the 60Hz display in some cases.
Right now I will be pretty busy but I am going to take a look at how I can solve this when it's night for me.
Found an additional bug with multiple refreshrate monitors!
Left - 144hz
Right - 75hz
Using MaxFPS=144 & RefreshRate=144 in ~/.config/kwinrc (as some apps such as Firefox were still locked to 75(?)hz without it.)
With kwin-lowlatency (AUR 5.15.5-1): https://streamable.com/tqelw
With normal kwin (kwin-5.15.4-1): https://streamable.com/2ynsa
Fullscreening Discord (from the AUR) seems to lock both monitors down to 75hz only when using kwin-lowlatency
So I just began testing KWin-lowlatency under a multi-monitor setup and just found another bug: if unredirection is on, and an application is full-screen in a monitor, the compositor severely slows down for the other monitors.
Additional note, @tildearrow, is that Discord itself seems to always run at 60(?)fps. I'm not sure if that is part of the bug you and I are experiencing or not (and I doubt the Discord framelock outside of fullscreen is a bug with your implementation).
So I just began testing KWin-lowlatency under a multi-monitor setup and just found another bug: if unredirection is on, and an application is full-screen in a monitor, the compositor severely slows down for the other monitors.
I just noticed the same issue with my setup and came across this issue. I am using three monitors, all run on 60 Hz. If one of them has a full screen app running, the others seem to lock to 15 fps.
Is there a more specific issue I can refer to in case more info is needed?
Additional note, @tildearrow, is that Discord itself seems to always run at 60(?)fps. I'm not sure if that is part of the bug you and I are experiencing or not (and I doubt the Discord framelock outside of fullscreen is a bug with your implementation).
This is actually an issue on Chromium. Chromium is locked to 60fps on multi-monitor setups, somehow, and Discord uses Electron, which uses Chromium.
