Bug 511835

Summary:	Glitched state of tablet cursor location input
Product:	[Applications] systemsettings	Reporter:	sythys <sythys>
Component:	kcm_tablet	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	normal	CC:	aleixpol, josh, nicolas.fella, sythys
Priority:	NOR
Version First Reported In:	6.3.6
Target Milestone:	---
Platform:	NixOS
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description sythys 2025-11-08 16:40:21 UTC

Hello,
Thank you for looking into this.

SUMMARY
I can reproduce a glitched state for my tablet hid device that essentially makes further cursor inputs impossible. It seems like it freezes, but the tablet is actually still working with all features except for cursor location.

I'm not sure where this bug is originating from, as it didn't throw any error messages, and I don't know how to isolate it further.
I can give you some hints on why I think the actual problem is a glitched state.

1. When I reconnect the tablet, and it receives a new USB bus ID the glitched state is cleared, but when I do a power cycle using usbreset or usbctl -a cycle the Issue is still there as the device ID didn't change.
2. When producing the glitch, all other device interactions work normal, only pen interactions are seemingly gone.

STEPS TO REPRODUCE
src: I used the Wacom Intuos Draw, but it might work with any tablet.
1. Set the mapped area to a very small region. I have it set to 26%x22%
2. Flick the pen over the area to accelerate the cursor towards the edge of the screen. It might take a few tries.

OBSERVED RESULT
The Tablet pen is unresponsive until the hid device is reinitialized with a new USB bus/device port (not actual other physical USB port)

EXPECTED RESULT
The Cursor location should stay absolute to tablet coordinates. When cursor location or other metric overflows or enters some other kind of glitched state, the pen should be reinitialized.

SOFTWARE/OS VERSIONS
Operating System: NixOS 25.05
KDE Plasma Version: 6.3.6
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.3
Kernel Version: 6.12.56 (64-bit)
Graphics Platform: Wayland
Processors: 16 × Intel® Core™ i9-9900K CPU @ 3.60GHz
Memory: 62.7 GiB of RAM
Graphics Processor: NVIDIA GeForce RTX 2080 Ti

ADDITIONAL INFORMATION
I guess my workaround is to not drop the pen on my tablet when I want to type something. I can give more detailed instructions if needed, but I think this should suffice.
The whole ordeal gives me a strong feeling the issue lies within kwin input handling.
I did a lot of testing and fiddling around. If you have any questions, You might remind me of Information I accidentally omitted here.

Comment 1 sythys 2025-11-08 17:03:39 UTC

I'm wrong about the kwin input handling, the issue is gone when using OpenTabletDriver instead.

Comment 2 Nicolas Fella 2025-11-09 16:09:23 UTC

This doesn't really sound like a KWin issue, more a driver problem.

You use "sudo libinput debug-events" to see the events as KWin receives them. If that looks broken then it's not a KWin issue

Comment 3 Joshua Goins 2025-11-27 23:16:34 UTC

Setting this to NEEDSINFO until that's confirmed. It would also be good to know which libinput version you used.

Comment 4 sythys 2025-12-01 19:15:11 UTC

Since OpenTabletDriver works fine, and is officially supported by Wacom, and it is non-proprietary, I'm fine with this being marked as "won't fix", as I didn't put the effort in drilling deeper into the issue. Especially as my tablet settings were very edge case, and normal people will not use a tablet like I do.

I'll mark it as RESOLVED / WORKSFORME, as I don't know a better category.
Thank you.

The lib input version I use is 1.27.1
It's also definitely a driver problem.