Bug 485724

Summary:	When using a mouse with a high resolution scroll wheel, KWin only registers every 8th scroll action
Product:	[Plasma] kwin	Reporter:	kdebugs
Component:	input	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	CONFIRMED ---
Severity:	normal	CC:	cwo.kde, duha.bugs, kde, kdedev, nate
Priority:	NOR
Version First Reported In:	5.19.0
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description kdebugs 2024-04-18 09:56:59 UTC

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SUMMARY
When I use my Logitech MX Anywhere 3 mouse over bluetooth, I have to turn the wheel 8 clicks for it to perform any scrolling action. Sometimes it starts working in one or both directions after the initial 8 scroll actions, but it is not persistent. `btmon` sees every scroll action, but only every 8th is performed. 

Mouse `Scrolling speed` setting only impacts how much every 8th notch scrolls.

Here is what `btom` output looks like (one action in each direction, which were not registered in KDE):

> ACL Data RX: Handle 76 flags 0x02 dlen 14                                                           #2 [hci0] 2.300707
     ATT: Handle Value Notification (0x1b) len 9
        Handle: 0x002a
          Data: 0000000000ff00
> ACL Data RX: Handle 76 flags 0x02 dlen 14                                                           #3 [hci0] 3.373249
      ATT: Handle Value Notification (0x1b) len 9
        Handle: 0x002a
          Data: 00000000000100

The exact same mouse works properly on other linux machine running sway, a macbook running macos and an android device.

STEPS TO REPRODUCE
1. Use MX Anywhere 3 mouse over bluetooth
2. Scroll by 1 to 7 notches

OBSERVED RESULT
Nothing happens

EXPECTED RESULT
1 to 7 scroll actions happen

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
6.6.3-414.asahi.fc39.aarch64+16k
KDE Plasma Version: 5.27.11
KDE Frameworks Version: 5.115.0
Qt Version: 5.15.12
Graphics Platform: Wayland

ADDITIONAL INFORMATION
I'm using it on MacBook Pro 2021 running asahi linux.

My reddit post (contains someone experiencing a similar bug on a VM): https://www.reddit.com/r/kde/comments/1c64qgk/mouse_scrolling_skips_steps/
Someone having the same problem 3 years ago: https://www.reddit.com/r/kde/comments/i9qui7/mouse_wheel_randomly_reverts_to_exceedingly_slow/g6fdia4/

Comment 1 Nate Graham 2025-05-21 16:27:50 UTC

Thanks for the bug report, and I'm sorry we weren't able to get to it yet. A lot has changed since this issue was reported; can I ask you to check if it's still happening with Plasma 6.3.5 or later?

If you can still reproduce it, can you mention whether you've changed the scroll speed? If so, does resetting to the default scroll speed fix the issue?

Thanks a lot!

Comment 2 cwo 2025-06-01 17:29:21 UTC

FIW, I have the same issue on some (non-bluetooth) wireless logitech mice. I think it's a libinput issue with hi-res scroll wheels; I can fix it by turning the mouse off and on, or by using one of the libinput polling monitor tools (I'd have to look up which one it was, but it requires sudo rights and the usb id, so power-cycling the mouse is more convenient). When it's in the buggy state, the kwin bug console only gets every fourth click, and I think evtest had the same result). So I suspect upstream issue.

Comment 3 TraceyC 2025-06-02 16:42:52 UTC

Setting to confirmed since cwo is seeing the bug currently

FWIW I've not seen this issue with a wireless G502 Lightspeed or wireless M510, both Logitech

Comment 4 cwo 2025-06-02 17:48:19 UTC

Mine is a M705 (two actually, one new the other a decade or so old). I didn't see it on a M325, but I'm not sure if that one has a hi-res scroll wheel.

Comment 5 Nate Graham 2025-06-03 18:50:47 UTC

Have either of you changed the default scroll speed?

Comment 6 cwo 2025-06-03 19:07:28 UTC

(In reply to Nate Graham from comment #5)
> Have either of you changed the default scroll speed?

I don't think I have, let me check... No, fifth tick everywhere and I think that's the default.

It happens very intermittently - sometimes it doesn't seem to happen at all, then I wake it up from suspend, and scrolling is slow. Sometimes more often, usually days without it happening. On two different computers, but with the same model of mouse, both Fedora, one stock Plasma the other usually master.