Bug 440705

Summary:	(Wayland) Mouse getting stuck between monitors when left monitor is scaled by certain scale factors
Product:	[Plasma] KScreen	Reporter:	Berengal <sjurberengal+kde>
Component:	common	Assignee:	kscreen-bugs-null <kscreen-bugs-null>
Status:	RESOLVED FIXED
Severity:	normal	CC:	nate, xaver.hugl
Priority:	NOR
Version First Reported In:	5.22.4
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Berengal 2021-08-07 18:48:19 UTC

SUMMARY
I have two monitors, one 24" 1080p and one 27" 1440p, with the 1080p monitor being on the left side and the 1440p being in front of me. I use kwin's individual monitor scaling on Wayland so the physical size of windows line up. With scaling of the left (1080p) monitor at 100% I can freely move the mouse between the two screens without it getting stuck on the dividing line, but if I change its scaling to 85% the mouse gets stuck on the dividing line unless I move it at high speed. In the monitor layout they are both snapped right next to each other with no gap between.

I tried other scale factors from 75% to 115% and found the mouse only getting stuck on 80%, 85% and 110% scaling.

STEPS TO REPRODUCE
1. Connect a 1080p monitor and a 1440p monitor
2. In System Settings -> Display and Monitor -> Display Configuration: put the 1080p monitor to the left of the 1440p monitor, with the edges lined up perfectly (snapped together)
3. Change the scaling of the left monitor
4. Move the mouse between the two monitors at different speeds

OBSERVED RESULT
With the left monitor at 100% scale the mouse cursor moves from one screen to the other regardless of the speed it's moved at. At 85% scale the cursor gets stuck at the edge of the screen when it's moved slowly.

EXPECTED RESULT
The mouse should move smoothly between monitors regardless of scaling and mouse speed.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma:
(available in About System)
KDE Plasma Version: 5.22.4
KDE Frameworks Version: 5.84.0
Qt Version: 5.15.2
Graphics platform: Wayland

ADDITIONAL INFORMATION

Comment 1 Zamundaaa 2021-08-26 18:44:01 UTC

Can you provide the output of "kscreen-doctor -o" with the screen scaled?

Comment 2 Berengal 2021-08-27 11:23:52 UTC

(In reply to Zamundaaa from comment #1)
> Can you provide the output of "kscreen-doctor -o" with the screen scaled?

▶ kscreen-doctor -o
kscreen.kwayland: Loading Wayland backend.
Output: 1 AUS VG27AQL1A/L5LMQS180289 enabled connected  Unknown Modes: 0:2560x1440@60! 1:2560x1440@144* 10:1920x1080@60 11:1920x1080@50 12:1600x1200@60 13:1680x1050@60 14:1280x1024@75 15:1280x1024@60 16:1440x900@60 17:1280x800@60 18:1152x864@75 19:1280x720@60 2:2560x1440@120 20:1280x720@60 21:1280x720@50 22:1440x576@50 23:1440x576@50 24:1024x768@75 25:1024x768@70 26:1024x768@60 27:1440x480@60 28:1440x480@60 29:1440x480@60 3:2560x1440@100 30:1440x480@60 31:832x624@75 32:800x600@75 33:800x600@72 34:800x600@60 35:800x600@56 36:720x576@50 37:720x576@50 38:640x480@75 39:640x480@73 4:1920x1200@60 40:640x480@67 41:640x480@60 42:640x480@60 43:720x400@70 5:1920x1080@120 6:1920x1080@120 7:1920x1080@100 8:1920x1080@60 9:1920x1080@60 Geometry: 2259,0 2560x1440 Scale: 1 Rotation: 1 Overscan: 0 Vrr: Automatic 
Output: 2 AOC G2460PG/#ASP3TWZ0iUL enabled connected primary Unknown Modes: 0:1920x1080@60*! 1:1920x1080@144 10:1280x720@60 11:1024x768@60 12:800x600@60 13:640x480@60 14:640x480@60 2:1920x1080@120 3:1920x1080@100 4:1920x1080@85 5:1920x1080@60 6:1680x1050@60 7:1280x1024@60 8:1440x900@60 9:1280x800@60 Geometry: 0,85 2255x1268 Scale: 0.851563 Rotation: 1 Overscan: 0 Vrr: incapable primary

Comment 3 Zamundaaa 2021-08-27 11:56:19 UTC

Okay, so the displays are not aligned correctly. The snapping is somehow not maintained by KScreen

Comment 4 Berengal 2022-02-10 03:36:50 UTC

I just installed Plasma 5.24 and this problem is now gone.