Bug 477431

Summary:	Slightly jumpy scrolling when scrolling through sidebar by slowly dragging the scroll handle
Product:	[Applications] systemsettings	Reporter:	Jan Rathmann <jan.rathmann>
Component:	sidebarview	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	REOPENED ---
Severity:	minor	CC:	agurenko, bizyaev, bokic1023, dimitri.code, nate, notmart, qydwhotmail
Priority:	NOR	Keywords:	qt6
Version First Reported In:	5.27.80
Target Milestone:	---
Platform:	Neon
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:	6.0
Sentry Crash Report:
Attachments:	Video of the glitches The scroll glitch in setting pages Scroll bar changing size Video of jumpy/buggy scrolling

Description Jan Rathmann 2023-11-23 18:13:10 UTC

STEPS TO REPRODUCE
1. Open Systemsettings.
2. Grab the scrollbar of the category list with your mouse (keep left button pressed).
3. Move slowly up or down.

OBSERVED RESULT
The category items "jump" up and down a tiny bit while scrolling, which looks a bit glitchy.

EXPECTED RESULT
No glitches during scrolling.

SOFTWARE/OS VERSIONS
KDE Plasma Version: 5.81
KDE Frameworks Version: 5.245
Qt Version: 6.6.0

ADDITIONAL INFORMATION
Best visible when running on real HW, but I see it also in a VM.
Tested under Neon Unstable and openSuse Krypton live image.

Comment 1 Jan Rathmann 2023-11-23 18:13:39 UTC

Seems independent of running Wayland or X11.

Comment 2 Nate Graham 2023-11-26 19:25:00 UTC

Cannot reproduce on bare metal and Wayland. Can you attach a screen recording that shows the issue?

Comment 3 Jan Rathmann 2023-11-27 11:17:41 UTC

Created attachment 163536 [details]
Video of the glitches

Ok, added a screencast showing the glitches.

I forgot to mention, this is something new in Plasma 6 (the animation looks fine in Plasma 5).

Comment 4 Nate Graham 2023-11-29 18:11:01 UTC

Ah, can reproduce now after seeing how slow you're dragging the scrollbar.

I wonder if this is an issue with the new smooth scrolling code in WheelHandler. Will investigate.

Comment 5 Fushan Wen 2024-01-06 14:06:58 UTC

This is likely related to the new separator style.

Comment 6 Nate Graham 2024-01-18 00:10:30 UTC

Cannot reproduce anymore with either 200% or 225% scale. Some patches went in to better pixel-align things, so I suspect they fixed it!

Comment 7 Jan Rathmann 2024-01-18 07:53:46 UTC

(In reply to Nate Graham from comment #6)
> Cannot reproduce anymore with either 200% or 225% scale. Some patches went
> in to better pixel-align things, so I suspect they fixed it!

Strange, can still reproduce it – in a VM (Neon Unstable) and on bare HW (self-build Plasma 6.0).
Changing scale to 200% doesn't make a difference for me (my default is 100%).
Using a different mouse doesn't change anything either.

Comment 8 Dimitri 2025-01-04 15:40:49 UTC

Created attachment 177107 [details]
The scroll glitch in setting pages

The bug is not restricted to the side view, it is also present in scrolling of some setting pages, like the one with all the animations.
I am also thinking that the bug is related to the section separator, and probably because the bar doesn't take it into account correctly.

SystemSettings : 6.2.4
Operating System: KDE neon 6.2
KDE Plasma Version: 6.2.4
KDE Frameworks Version: 6.9.0
Qt Version: 6.8.1
Kernel Version: 6.8.0-51-generic (64-bit)
Graphics Platform: Wayland

Comment 9 Dimitri 2025-01-04 15:51:31 UTC

Created attachment 177108 [details]
Scroll bar changing size

The bug has a reverse version : when you scroll without using the scrollbar, the scrollbar changes size many times during scrolling.
I am sure it is a second manifestation of the same bug.

Comment 10 bokic1023 2025-10-27 02:19:52 UTC

Created attachment 186213 [details]
Video of jumpy/buggy scrolling

The bug is present on up to date EndeavourOS and up to date KDE Linux (Plasma 6.5.0/6.5.80 and System Settings 6.5.0/6.5.80).
The recording is done on EndeavourOS with 150% scaling, but I also have a laptop with KDE Linux on 100% scaling.