Bug 510278

Summary:	Invalid Compose key combination causes permanent freeze until reboot or sleep
Product:	[Plasma] kwin	Reporter:	rlacroix
Component:	input	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	crash	CC:	duha.bugs, kdedev
Priority:	NOR
Version First Reported In:	6.4.5
Target Milestone:	---
Platform:	Fedora RPMs
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	an example of the compose key bug

Description rlacroix 2025-10-05 20:18:34 UTC

SUMMARY
Whenever an invalid compose key combo is hit (ex : `<COMPOSE>` then `p` then `'`) the system totally freezes. The only ways I have found for now to get out of it are hard rebooting (pressing the power button) or getting it to sleep by closing the laptop lid on a laptop. 

In the second case, when logging back, the login screen shows only 1/3 of a the time, else the frozen screen is shown again and I have to do the sleep hack again. When logged in the wifi had been disabled and takes quite a long time to reconnect (more than usual it seems) and at the location of the cursor was what seemed to be about 5 lines of the character wrongly typed (in my example a `p`).

STEPS TO REPRODUCE
1. Set a compose key
2. Hit an invalid combo

OBSERVED RESULT
The screen freezes

EXPECTED RESULT
An "error" sound should play according to the user's preferences. Nothing should be input and the screen should not freeze

SOFTWARE/OS VERSIONS
Operating System: Fedora Linux 42
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.18.0
Qt Version: 6.9.2
Kernel Version: 6.16.9-200.fc42.x86_64 (64-bit)
Graphics Platform: Wayland

ADDITIONAL INFO
Compose key : AltGr
Layout (both physical and used) : ANSI QWERTY
I configured the compose key at least 4 versions of Fedora ago

Comment 1 rlacroix 2025-10-05 20:23:10 UTC

Created attachment 185542 [details]
an example of the compose key bug

Comment 2 rlacroix 2025-10-05 20:25:01 UTC

Erratum : the wrong compose key combo was `x` + `'` as can be seen on the attachment. I could not replicate it in the context of the text fields like this one though.

Comment 3 TraceyC 2025-10-06 16:37:07 UTC

I'm not able to reproduce this on Plasma built from git-master, or with Fedora 42
In KWrite, I typed <COMPOSE> x '

The ' character appeared in KWrite and the system remained responsive. I was able to use the compose key normally before and after this.

Are you able to reproduce this with a new user? I'm wondering if another setting is interfering here.

Comment 4 rlacroix 2025-10-06 19:53:20 UTC

I did a bit more testing and for now all occurrences of this bug were on electron-based apps such as discord or obsidian (text areas in browsers do not cause it for instance).
I cannot create a new user for now but I will try to do so when I can.

Comment 5 TraceyC 2025-10-06 21:49:47 UTC

Thanks, that's useful. I'm not able to reproduce this with Obsidian Notes or Discord on git-master, nor can I reproduce with Obsidian on Fedora 42
Layout: English (US) with dead keys

What keyboard layout are you using?

Comment 6 rlacroix 2025-10-07 04:54:56 UTC

I updated all packages since the submission of the bug and cannot reproduce it anymore on the apps on which it was always there. This was perhaps linked to a specific version of a runtime used by Electron apps ? I now get the error sound I was used to before this bug arose.
I guess this could be marked as "fixed", until someone rediscovers it ?

Comment 7 TraceyC 2025-10-08 16:06:10 UTC

Thanks for the update. It does sound like it was probably linked to Electron. I'll close this for now, feel free to reopen it if this happens again.