Bug 494245

Summary:	Mouse speed feels much faster when screen is scaled on wayland
Product:	[Plasma] kwin	Reporter:	Weng Xuetian <wengxt>
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED INTENTIONAL
Severity:	normal	CC:	xaver.hugl
Priority:	NOR
Version First Reported In:	6.1.5
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Weng Xuetian 2024-10-07 15:10:57 UTC

SUMMARY
The mouse speed on kwin when scale is enabled doesn't match the speed on other systems.
For example, if I uses 1920x1080 system, when I set the scale, the mouse (physical one, not touchpad) feels moves much faster. And it is significantly faster comparing to other OS (e.g. windows) or X11 on the same machine.

I have to use the mouse hardware dpi button to adjust back and force when switching the system to get the same speed feeling. On other OS or X11, no matter how the scale is changed, I don't feel the mouse speed is changed at the same time.

STEPS TO REPRODUCE
1. Set scale to >100 (e.g. 125)
2. Move mouse

OBSERVED RESULT
Mouse is significantly move faster on scaled screen

EXPECTED RESULT
Mouse moves the same speed before the scale is enabled.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
KDE Plasma Version: 6.1.5
KDE Frameworks Version: 6.6.0
Qt Version: 6.7.2

ADDITIONAL INFORMATION

Comment 1 Zamundaaa 2024-10-07 15:49:26 UTC

This is intentional, mouse speed is relative to the size of content and not to the resolution of the screen. If you want to make the cursor slower, you can use the mouse settings to reduce its speed.