UI element(?) stuck at the corner of the screen

Help
1

Hello, is been a while I am experiencing this weird UI element stuck at the top left corner of the screen.

I use Arch and am on latest 6.3.4-4 kwin/kde packages.

Operating System: Arch Linux
KDE Plasma Version: 6.3.4
KDE Frameworks Version: 6.12.0
Qt Version: 6.9.0
Kernel Version: 6.14.1-arch1-1 (64-bit)
Graphics Platform: X11
Processors: 12 × 11th Gen Intel® Core™ i5-11400 @ 2.60GHz
Memory: 31,2 GiB of RAM
Graphics Processor: NVIDIA GeForce RTX 3060
Product Name: Z590 Extreme

Screenshot_20250411_043418_01

You can see an example in the picture above. That thing will stay on top of anything else, but I cannot interact with it at all. Not even restarting/replacing plasmashell helps. The only way to fix is to logout of the session and log back in.
I never noticed what causes it to appear since it is in a quite far off portion of the screen so by the time I notice is too late, but it seems to happen while switching around activities/virtual desktops.

I have tried searching around with no avail since I wouldnt know where to fetch any log for this kind of error, and most of the “corner screen” threads that come up are related to the hot corners feature, which is disabled on my installation since day 1.

2

Did you modify your system? Changed default KDE settings, custom themes for example.

3

if you go into edit mode is there nothing there to select when you hover over it?

what have you turned on (if anything) in the screen edges settings?

4

yes I have klassy windows decorations and catppuccin color scheme, but otherwise I am on default breeze dark.

5

no even in edit mode is like that item does not exists there.

In screen edges I only have maximixe and tile activated.

6

Hi - does it remain if you disable Klassy?

And by chance, do you have anything placed on one of your desktops near or past the edges, which might be triggering it to be scrollable?

7

I tried resetting the whole theme options to default once it appears but it doesnt help. But I never tried running for an extended period of time with defaults at boot.

As for the second question. I dont have any application specifically pinned to top left but I do have librewolf taking the whole left side of the screen (including the corner ofc).
Last time it apparently bugged I actually launched a youtube video from within Librewolf which in turned opened freetube which caused kde to switch activity.

I will see if I can spam open things/switch desktops until I finally understand what triggers it.

8

You’re not crazy; I’ve heard the same report from others in the past. Unfortunately, so far literally nobody has been able to figure out what it is or where it comes from.

9

It happen once for me a couple of month ago. I just closed it and it never happened again.

10

But how did you close it?

11

I can’t recall. But I think I was in “Edit Mode”, then right click on the UI element which gave me a close option.

12

I got it today (well, I get it everyday) and nothing can be done in edit mode either. The UI element is not recognized by anything.

I can also mostly confirm that is related to focus switching of sort:. I was just in dolphin browsing folder, opened a video with smplayer, which moved the focus away from dolphin to the player, and the thing just appeared; or, more likely, part of dolphin ui “detached itself” sticking to the corner. This would explain why I experience it when opening new programs that trigger focus switching. Is almost as if something happens during the focus switching preventing some of the UI element from getting out-focused. Why it happens only to top left corner I have no idea.

13

Just on the chance that either one might affect this…does it happen if you use:

  • the Nouveau drivers, instead of the proprietary NVIDIA ones?
  • a Wayland session, instead of X11?
14

Does it appear on a newly created user?

15

I couldnt test new users or wayland since that would mean I pretty much cant work in the meanwhile.

But today I finally managed to trigger it at will.

So in the past few days I had reactivated the screen edges functionality, binding Present Windows to bottom left corner. Maybe it was luck maybe not but the problem did not appear in those days. Now, and I mean right now, 1 minute ago, I got annoyed again by the hot corners. So I want to settings, screen edges, togglet “no action” in the bottom left corner and as soon as I clicked apply the stuck element appeared top left.

Now, I dont know if this is proof the bug is related to screen edges. I have noticed some very quick refresh when I applied the setting, so perhaps that triggers some UI refresh that indirectly causes the bug to happen.

Anyway I made a video that should be quite interesting for the KDE devs.
I have recorded 2 angles, one using gpu screen recorder so recording from “within” the system, another angle from my phone, so recording from without. Notice the difference. While I play with the screen corner settings nothing happens in the within video, as if the system cannot see the popup. From the phone angle you can see how it appears to the user.

I have uploaded both videos on swisstr hope it’s ok.
[well cant include links so will try to figure out later how to share them]

so whatever happens when I change UI/corner settings is what causes the bug.

16

Hmm…are you able to check if triggering Present Windows causes it to appear, or change its appearance, even if it’s not set as a hot corner?

Or on the other hand, are you able to check if something else other than Present Windows can reproduce that same effect when applied to the bottom left corner?

17

so

  1. I can reproduce it 100% of the times now
  2. it doesnt matter what is set or unset in the hot corner, doesnt even matter which hot corner is set, the moment I change something (eg activating some function or setting no action) and press apply the bug happens.

Moreover

  1. try to take screenshot with spectacle when bug is visible
  2. the whole plasmashell freezes. PC is still usable but the UI is fully unreponsive. Spectacle doesnt even trigger area selection. I can alt tab to switch active window and use whatever application normally as long as it doesnt require clicking any UI element: I am typing this message while UI is frozen but I cant click on the “reply” button for example.
18

sorry for doubleposting cant edit prev. post

bug is not related to hot corners functionality themselves, because it can be triggered by any UI change/reload. I again logged out, logged back in fresh, changed window deco, clicked apply: bug. But bug looks slightly different, it doesnt have those outlined borders.

I dont know if these kinds of UI fresh leave any log traces to see what exactly happens.

I have tried wayland too and bug doesnt occur there. So it is X related. I wonder if it’s some random setting I set up year ago when nvidia drivers sucked that is now biting me in the back for whatever reason.

Dont think if these infos are enough to file a proper bug report.