Bug 462517

Summary: On Wayland, scrolling speed being scaled causes scroll-based UIs (e.g. switching virtual desktops, changing volume) to go at a different speed than was intended
Product: [Plasma] kwin Reporter: Alfred <home.isfar+kde>
Component: wayland-genericAssignee: KWin default assignee <kwin-bugs-null>
Status: RESOLVED DUPLICATE    
Severity: minor CC: bugseforuns, john, kde, nate, xaver.hugl
Priority: NOR Keywords: usability, wayland-only
Version First Reported In: 5.26.4   
Target Milestone: ---   
Platform: Fedora RPMs   
OS: Linux   
Latest Commit: Version Fixed In:
Sentry Crash Report:

Description Alfred 2022-12-01 19:37:01 UTC 
SUMMARY
Setting the mouse scroll speed in KDE Wayland to a lower speed changes the number of times I have to tick my scroll wheel to switch to a previous/next virtual desktop.

STEPS TO REPRODUCE
1. Log into KDE Wayland.
2. In System Settings set the mouse wheel scroll speed to the lowest or second lowest, or even third lowest option.
3. Try to move the scroll wheel on the desktop to switch to the previous/next virtual desktops.

OBSERVED RESULT
It can take 2-3 scroll ticks to move between vdesktops.

EXPECTED RESULT
It should take only one scroll tick, just like in Xorg (coincidentally, Xorg does not appear to have a scroll wheel speed option and therefore I cannot try to reproduce the issue with X).

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora 37
KDE Plasma Version: 5.26.3
KDE Frameworks Version: 5.100.0
Qt Version: 5.15.7

ADDITIONAL INFORMATION
I'm using a physical mouse, not a trackpad. I have three virtual desktops set up.
Comment 1 Nate Graham 2022-12-01 22:57:10 UTC 
Scrolling on the desktop, you mean?
Comment 2 Alfred 2022-12-02 00:09:02 UTC 
Yes. I meant try to scroll the mouse wheel (up/down) while the cursor is hovering the over the desktop. As far as I know by default this action should move the user to the next/previous virtual desktop.
Comment 3 Nate Graham 2022-12-02 18:33:45 UTC 
Ok, I can reproduce this.

I'm pretty sure that it happens because on Wayland, we're scaling all input events to approximate a scroll speed setting, which Libinput doesn't provide.

We would have to de-scale the scroll events in Plasma to ensure a consistent scroll speed for things that should stick to the logic of one mouse wheel "tick" equaling one change in the thing being scrolled
Comment 4 Patrick Silva 2023-12-30 21:21:21 UTC 
Scrolling speed also affects the zoom adjustment with ctrl+scrolling in Gwenview.

Gwenview 24.01.85
Operating System: Arch Linux 
KDE Plasma Version: 5.91.0
KDE Frameworks Version: 5.247.0
Qt Version: 6.7.0
Graphics Platform: Wayland
Comment 5 Zamundaaa 2024-06-11 23:41:33 UTC 

*** This bug has been marked as a duplicate of bug 470746 ***