Bug 513879

Summary:	Invert Scroll Direction changes not applied immediately
Product:	[Plasma] kwin	Reporter:	Innomen <Brandon.Sergent>
Component:	input	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	CONFIRMED ---
Severity:	normal	CC:	duha.bugs, kde, kdedev, nate, nicolas.fella
Priority:	HI
Version First Reported In:	6.5.4
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Innomen 2025-12-27 15:45:07 UTC

KWin's file monitoring system fails to detect changes to ~/.config/kcminputrc for mouse input device settings on Wayland. The System Settings GUI checkbox for "Invert scroll direction" updates the config file but KWin never applies the changes.

**Steps to Reproduce:**
1. Launch Plasma on Wayland
2. Open System Settings → Input Devices → Mouse
3. Toggle "Invert scroll direction" checkbox
4. Test mouse scroll wheel

**Actual Result:**
Scroll direction does not change. The setting is written to kcminputrc but KWin ignores it. Persists across qdbus reconfigure, plasmashell restarts, logout/login, and reboots.

**Expected Result:**
Scroll direction should change immediately when checkbox is toggled.

**Workaround That Reveals Bug:**
Terminal 1: tail -f ~/.config/kcminputrc
Terminal 2: systemsettings kcm_mouse
Now toggle the checkbox → IT WORKS

**Analysis:**
KWin's inotify watch on kcminputrc is not functioning. When tail -f creates an external inotify watch on the same file, KWin's watch suddenly starts working. This suggests the file monitor initialization is broken or has a race condition specific to Wayland.

**System:**
Garuda Linux, Kernel 6.18.2-zen2
KDE Plasma 6.5.4, KWin Wayland
Mouse: HS6209 2.4G Wireless Receiver (affects all mice)

Triggered after restarting PipeWire/Wireplumber services.

Comment 1 Nicolas Fella 2025-12-27 16:14:00 UTC

Please do not use AI to submit bugreports.

The analysis is completely wrong and made up, there is no inotify watch on kcminputrc at all.

Comment 2 Innomen 2025-12-27 16:50:22 UTC

Thanks for the feedback. To clarify: I'm a user who discovered this workaround accidentally while troubleshooting, and used AI to help format the bug report clearly.
The technical analysis may be incorrect about the mechanism, but the reproducible behavior is real:

Toggling "Invert scroll direction" in System Settings does nothing
Running tail -f ~/.config/kcminputrc in a terminal, THEN toggling the checkbox → it works
This workaround has been tested and confirmed working across reboots

I don't know why this works - I'm not a KWin developer. But the workaround is 100% reproducible on my system. If the inotify analysis is wrong, that's fine - I'm reporting the behavior, not claiming to understand KWin's internals.
Reproduction steps (verified):

System: Garuda Linux, KDE Plasma 6.5.4, Wayland
Without tail: Settings checkbox does nothing, scroll stays inverted
With tail running: Settings checkbox works immediately

If there's a better explanation for why this workaround functions, I'd genuinely like to understand it. The goal is fixing the issue, not defending my theory.

P.S. AI helped me write this reply, and be glad of it. You wouldn't like my original draft. You want human bug reports? Make the process less toxic and mechanical. And maybe don't scold people trying to help exclusively for the sake of it?

Comment 3 David Edmundson 2025-12-28 11:50:40 UTC

RE: AI, the key point is writing less is better. 
Just "the invert scroll direction checkbox doesn't take effect immediately".

Comment 4 David Edmundson 2025-12-28 11:51:07 UTC

I can reproduce.