Bug 504596 - Part of desktop is black on secondary screen
Summary: Part of desktop is black on secondary screen
Status: RESOLVED WORKSFORME
Alias: None
Product: plasmashell
Classification: Plasma
Component: general (other bugs)
Version First Reported In: 6.3.5
Platform: Arch Linux Linux
: NOR normal
Target Milestone: 1.0
Assignee: Plasma Bugs List
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2025-05-21 05:06 UTC by gudvinr+kde
Modified: 2025-08-09 03:46 UTC (History)
4 users (show)

See Also:
Latest Commit:
Version Fixed In:
Sentry Crash Report:


Attachments
secondary screen (480.98 KB, image/png)
2025-05-21 05:06 UTC, gudvinr+kde
Details

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Description gudvinr+kde 2025-05-21 05:06:00 UTC
SUMMARY

After boot I've got bottom part of the screen black.

It's a secondary screen and it's rotated 90°. I think this is the culprit because wallpaper looks like it if were applied to horizontally oriented screen.
Maybe some kind of data race, where display code can be applied after shell initializes environment. And doesn't check later if it's changed.

STEPS TO REPRODUCE
1. Boot

OBSERVED RESULT

Screenshot in attachment.
Black half hides drag selection but cursor and windows go over it.

Wallpaper seem to be correct but cropped as if screen weren't rotated at all.

EXPECTED RESULT

Correctly oriented screen.

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.0
Kernel Version: 6.14.6-arch1-1 (64-bit)
Graphics Platform: X11
Graphics Processor 1: AMD Radeon RX Vega M GL Graphics
Graphics Processor 2: Mesa Intel® HD Graphics 630
Comment 1 gudvinr+kde 2025-05-21 05:06:46 UTC
Created attachment 181594 [details]
secondary screen
Comment 2 Filip 2025-05-21 07:02:59 UTC
Can you open Display & Monitor section in System Settings and check the orientation setting for your monitor? Switch it to vertical.

Is this your first boot or was it working before and got switched to horizontal?
Comment 3 Nate Graham 2025-05-21 13:41:43 UTC
Some questions:
1. Is *anything* shown on the secondary screen that's black? Part of the wallpaper from another screen, for example?
2. If you right-click on the black area, do you see a context menu?
3. If you drag a window over to the black area, does it remain visible and interactive?
4. Does any of this happen if you log into a Wayland session on the same machine? Or does it only happen in an X11 session?
Comment 4 gudvinr+kde 2025-05-21 14:53:49 UTC
(In reply to Filip from comment #2)
> Can you open Display & Monitor section in System Settings and check the
> orientation setting for your monitor? Switch it to vertical.

It is switched to vertical (and was before too).

(In reply to Filip from comment #2)
> Is this your first boot or was it working before and got switched to
> horizontal?

Not the first. It's working system that I use on a regular basis.

It's not switched to horizontal, it is vertical. But wallpaper and some other stuff (like box selection) thinks it's horizontal.


(In reply to Nate Graham from comment #3)
> Some questions:
> 1. Is *anything* shown on the secondary screen that's black? Part of the
> wallpaper from another screen, for example?
> 2. If you right-click on the black area, do you see a context menu?
> 3. If you drag a window over to the black area, does it remain visible and
> interactive?
> 4. Does any of this happen if you log into a Wayland session on the same
> machine? Or does it only happen in an X11 session?

1. Don't really understand the question. I see what's shown on screenshot. Top part shows wallpaper, bottom part is black.
2. No
3. Yes, it does
4. Can't say, don't use wayland as it has issues more severe than this one
Comment 5 Nate Graham 2025-05-21 16:02:25 UTC
On X11, if you restart plasmashell with `systemctl restart --user plasma-plasmashell.service`, does the issue disappear?

Can you try the Wayland session for debugging purposes, to see if the issue is there as well?
Comment 6 gudvinr+kde 2025-05-22 10:27:11 UTC
(In reply to Nate Graham from comment #5)
> On X11, if you restart plasmashell with `systemctl restart --user
> plasma-plasmashell.service`, does the issue disappear?

Sadly I already turned off PC at this point. After boot there's no issue so I think restarting plasmashell would've helped too.
However, this isn't first time I see this.

It looks like code responsible for configuring layouts and plasmashell code that uses layout information are not in sync with each other.
And in very rare occasions layout configuration (rotation in my case) happens after plasmashell configured desktop containment.
Comment 7 gudvinr+kde 2025-05-22 10:30:22 UTC
(In reply to Nate Graham from comment #5)
> Can you try the Wayland session for debugging purposes, to see if the issue
> is there as well?

If it is indeed some sort of data race (because after reboot everything is fine), the fact that issue isn't present at the moment doesn't tell anything useful.

I'll try to change session when I see this again but what'd happen is likely just the fact of changing session (either to wayland or back to x11) would fix issue on its own.
Comment 8 Nate Graham 2025-05-22 15:31:07 UTC
I asked because I strongly suspect it never happens on Wayland, because the Wayland and X11 sessions handle mixed-DPI multi-monitor setups very differently. Mostly, on Wayland they're handled well and on X11 they're handled badly. :)
Comment 9 gudvinr+kde 2025-05-23 05:42:45 UTC
(In reply to Nate Graham from comment #8)
> I asked because I strongly suspect it never happens on Wayland, because the
> Wayland and X11 sessions handle mixed-DPI multi-monitor setups very
> differently. Mostly, on Wayland they're handled well and on X11 they're
> handled badly. :)

I understand that. But since it happens only from time to time, makes this kind of test inconclusive.

For what it worth, I use same DPI on X11 (not sure if it's even possible to change scale per monitor on X11 though). Layout changes include scale (125%) and secondary screen rotation.
Comment 10 Bug Janitor Service 2025-06-07 03:47:55 UTC
🐛🧹 ⚠️ This bug has been in NEEDSINFO status with no change for at least 15 days. Please provide the requested information, then set the bug status to REPORTED. If there is no change for at least 30 days, it will be automatically closed as RESOLVED WORKSFORME.

For more information about our bug triaging procedures, please read https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging.

Thank you for helping us make KDE software even better for everyone!
Comment 11 gudvinr+kde 2025-06-10 11:09:00 UTC
Haven't had this issue yet, so can't really check it on both sessions.
Comment 12 gudvinr+kde 2025-06-13 14:09:05 UTC
(In reply to Nate Graham from comment #5)
> Can you try the Wayland session for debugging purposes, to see if the issue is there as well?

Caught this bug again today and tried to login into wayland session right after that.

Screen is okay as expected but there's huge BUT:
When I re-login into X11 back, it's all good again too.

So from my side it's impossible to say whether or not it's X11 only because it is random and lasts until plasma restart.

> On X11, if you restart plasmashell with `systemctl restart --user plasma-plasmashell.service`, does the issue disappear?

Haven't tried this one yet.
Comment 13 John Kizer 2025-06-22 17:28:49 UTC
Do you use multiple Activities on your device, by chance? The end result of this issue sounds like the result of https://bugs.kde.org/show_bug.cgi?id=495762 , so I figured it was worth a check if there was a connection.

Thanks!
Comment 14 gudvinr+kde 2025-06-23 10:41:44 UTC
(In reply to John Kizer from comment #13)
> Do you use multiple Activities on your device, by chance?

I do
Comment 15 John Kizer 2025-06-24 23:55:06 UTC
Thanks - when this issue occurs, does it occur on all Activities, or is the default Activity OK? Trying to figure out if this is actually the same underlying issue as https://bugs.kde.org/show_bug.cgi?id=495762 :-)
Comment 16 gudvinr+kde 2025-06-25 05:59:40 UTC
(In reply to John Kizer from comment #15)
> when this issue occurs, does it occur on all Activities, or is the default Activity OK?

Not OK, every activity is broken the same way until re-login.
Comment 17 Bug Janitor Service 2025-07-10 03:48:03 UTC
🐛🧹 ⚠️ This bug has been in NEEDSINFO status with no change for at least 15 days. Please provide the requested information, then set the bug status to REPORTED. If there is no change for at least 30 days, it will be automatically closed as RESOLVED WORKSFORME.

For more information about our bug triaging procedures, please read https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging.

Thank you for helping us make KDE software even better for everyone!
Comment 18 gudvinr+kde 2025-07-10 06:17:21 UTC
Can't really add anything new to what's already here.
Comment 19 Bug Janitor Service 2025-07-25 03:46:45 UTC
🐛🧹 ⚠️ This bug has been in NEEDSINFO status with no change for at least 15 days. Please provide the requested information, then set the bug status to REPORTED. If there is no change for at least 30 days, it will be automatically closed as RESOLVED WORKSFORME.

For more information about our bug triaging procedures, please read https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging.

Thank you for helping us make KDE software even better for everyone!
Comment 20 Bug Janitor Service 2025-08-09 03:46:51 UTC
🐛🧹 This bug has been in NEEDSINFO status with no change for at least 30 days. Closing as RESOLVED WORKSFORME.