[ttarr]

I should've been more clear, Firefox is just an example, my problem is the mouse pointer being affected by heavy load of any kind on the GPU/UI thread.

As coldblues said, it's probably Mutter not having an independent thread for the mouse pointer, X11's pointer handling is independent from Mutter/KWin it seems.

See the demo here to know exactly what I'm talking about: https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1241

[quotemstr]

> the mouse pointer being affected by heavy load of any kind on the GPU/UI thread.

It's because of stuff like this that we should treat UIs more like real time systems. There's really no good reason at all that a modern machine can't render every frame perfectly every time regardless of system load --- it's due to inadequate attention paid to isolating real-time-ish paths like mouse cursor movement, composition, input event dispatch, and so on from app-induced loads that we get weird responsiveness issues. X actually did a better job in this particular respect than your typical Wayland compositor --- it used interrupt driven mouse cursor rendering, for example.

[sph]

Weird, I'm not seeing it, not even with a GPU heavy game being rendered in a window.

[wander_homer]

I can easily reproduce the stuttering cursor on GNOME Wayland on all of my systems by doing this:

* move the mouse cursor evenly in a straight motion

* while moving press `Super+a` to open the application list

During the animation, i.e. when GNOME Shell is busy, the mouse cursor noticeably stutters for a moment. On my faster systems it's less apparent but still visible, except when I set the CPU governor to `performance`.

[Daunk]

I recently tried the new Ubuntu 22.04 LTS and the mouse stuttering was unbearable while running games via Wine. I had to switch back to Xorg to get rid of it.

[sph]

Smooth mouse input, especially when using high-DPI mice, is something that's been fixed in GNOME 42 due to release soon.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1915

[jancsika]

From that link:

> Nothing has been done here to avoid potential wayland event queue overflows, as IIUC this is being worked on separately. Although I should probably also mention that this hasn't been seen in the wild during this work.

[ttarr]

Interesting!

What's your monitor like? Sometimes I suspect it's because of my 4K monitor (with 1.5x scaling), that's a lot of pixels to shuffle, especially if the rendering code/pipeline is not optimised[0].

Testing my setup with a 1080p/75hz monitor[1], it's crazy fast and responsive, but mouse acceleration curve (and scroll), not speed, is still weird.

[0]See Ubuntu pushing for triple buffering for example, and other optimisation work on the past.

[1]Apparently that causes huge speedup, as it affects frame scheduling, according to one GUADEC talk by a Mutter dev.

[1_player]

I'm on 4K at 2x scaling.