Bug 505032

Summary: With the task switcher held open, some scrolling inputs can be passed through to the window that was active before Alt+Tabbing began
Product: [Plasma] kwin Reporter: LaserMoai <lasermoai>
Component: tabboxAssignee: KWin default assignee <kwin-bugs-null>
Status: CONFIRMED ---    
Severity: minor CC: cwo.kde, john.kizer
Priority: NOR    
Version First Reported In: 6.3.5   
Target Milestone: ---   
Platform: Arch Linux   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: Settings
Bug recording

Description LaserMoai 2025-05-30 19:52:17 UTC
SUMMARY
Scroll wheel input affects the current window by scrolling the contents in some applications like Chromium and the system monitor. This behavior is pretty weird and distracting.

STEPS TO REPRODUCE
1. Open a Chromium window.
2. Alt+Tab and scroll the wheel while the cursor is over it.

OBSERVED RESULT
You'll see the contents scrolling.

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.0
Comment 1 cwo 2025-06-02 20:50:52 UTC
I can't reproduce this with system monitor.

Can you show your Task Switcher settings (in System Monitor, screen shot is ok)? Is the system monitor you're talking about Plasma's system monitor or another one?  Can you take a screen recording of the effect when it happens?
Comment 2 LaserMoai 2025-06-03 08:16:59 UTC
Created attachment 181990 [details]
Settings

OK. It's Plasma's system monitor, it just moves horizontally.
Comment 3 LaserMoai 2025-06-03 08:18:35 UTC
Created attachment 181991 [details]
Bug recording
Comment 4 cwo 2025-06-05 09:35:03 UTC
Hm, with some settings I can get horizontal scrolling to work while alt-tab is active.

It seems I can also get it with vertical scrolling, but in way fewer circumstances (and that was with a trackpoint, where some scrolling events may be horizontal).

Can you try (a) turning off "Show selected window" and/or choosing a different switcher (like compact or large icons) to see if it also happens with those? That would help us narrow down the circumstances.
Comment 5 LaserMoai 2025-06-05 23:46:41 UTC
It doesn't reproduce with the large icons switcher.
Comment 6 LaserMoai 2025-06-05 23:48:18 UTC
Ah, nvm, it reproduces with other settings.
Comment 7 John Kizer 2025-06-18 04:46:45 UTC
Hi - are there other settings that you found could reproduce this issue? I've been able to find one set of circumstances:

1. Have a window active that can accept horizontal scrolling
2. Press Alt+Tab, hold Alt
3. Provide horizontal scrolling input - in my case, my mouse's scroll wheel can be pressed to the side to scroll horizontally
4. As seen in the thumbnail, the originally active window will receive the horizontal scroll input

Thanks!

Operating System: Fedora Linux 42
KDE Plasma Version: 6.4.80
KDE Frameworks Version: 6.16.0
Qt Version: 6.9.1
Kernel Version: 6.14.11-300.fc42.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 7800X3D 8-Core Processor
Memory: 32 GiB of RAM (30.4 GiB usable)
Graphics Processor 1: NVIDIA GeForce RTX 4070 SUPER
Graphics Processor 2: AMD Radeon Graphics
Comment 8 John Kizer 2025-06-18 04:47:41 UTC
Sorry for the double-email, typo!
Comment 9 LaserMoai 2025-06-18 15:44:08 UTC
It reproduces with all settings for me afaik. It can also pass vertical scrolling in Chromium.

I'm using xorg.