Bug 447228

Summary: Mouse scrolling (at least in KDE applications scrollbar menus) does not work under x11 when moving mouse cursor at same time
Product: [Plasma] plasmashell Reporter: blood990
Component: generalAssignee: David Edmundson <kde>
Status: RESOLVED UPSTREAM    
Severity: normal CC: nate, plasma-bugs-null
Priority: NOR    
Version First Reported In: 5.23.4   
Target Milestone: 1.0   
Platform: Neon   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: Sample bug reproduction video on kubuntu 21.10

Description blood990 2021-12-19 12:55:01 UTC 
SUMMARY
***
When trying to scroll down or up while moving mouse within scrollable content - scrolling does not work under x11. Under wayland seems to work fine. Tested with KDE Neon 5.23, Kubuntu 21.10 and Opensuse Tumbleweed
***

STEPS TO REPRODUCE
1. Open system settings or folder with lots of files in dolphin etc. under x11 session
2. Dynamically move mouse cursor in whatever pattern - up/down, circles etc. and use mouse wheel at same time, staying within bounds of scrollable content
3. See mouse wheel not doing anything until cursor movement is stopped

OBSERVED RESULT
Content not scrolling while moving mouse

EXPECTED RESULT
Content scrolling in addition to cursor movement

SOFTWARE/OS VERSIONS
Operating System: KDE neon 5.23, Kubuntu 21.10, Opensuse Tumbleweed
KDE Plasma Version: 5.23.4, 5.22.5
KDE Frameworks Version: 5.89.0, 5.86
Qt Version: 5.15.3, 5.15.2

ADDITIONAL INFORMATION
Tested systems were vmware virtual machines under windows host. Bug does not depend on mouse polling rate (tested with multiple).
Comment 1 blood990 2021-12-19 12:56:40 UTC 
Created attachment 144678 [details]
Sample bug reproduction video on kubuntu 21.10
Comment 2 Nate Graham 2022-01-11 21:37:17 UTC 
Does it happen in GTK or GNOME apps too? Or Electron apps like Discord?
Comment 3 blood990 2022-01-24 19:12:04 UTC 
(In reply to Nate Graham from comment #2)
> Does it happen in GTK or GNOME apps too? Or Electron apps like Discord?

Happens in gnome-software application and Discord. Looks like in Discord the bug also happens on Wayland
Comment 4 Nate Graham 2022-01-25 16:15:04 UTC 
Sounds like an X11-specific bug. On Wayland, Discord is running through XWayland, so it's hitting the same bug.