Bug 499266

Summary:	Taskbar disappears after idle/display outputs change
Product:	[Plasma] plasmashell	Reporter:	jakub
Component:	Panel	Assignee:	Plasma Bugs List <plasma-bugs>
Status:	RESOLVED DUPLICATE
Severity:	normal	CC:	Gvgeo, haakon+kdebugs, nate, niccolo.venerandi
Priority:	NOR
Version First Reported In:	6.2.5
Target Milestone:	1.0
Platform:	NixOS
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description jakub 2025-01-29 08:21:42 UTC

SUMMARY
Plasma taskbar disappears after turning the display back on.

STEPS TO REPRODUCE
1. Use an HDMI display
2. Set the taskbar panel Visbility to auto hide (not sure if it's relevant)
3. Enable Turn off screen in Power Management, but disable Suspending
4. Go idle for a while until the screen turns off
5. Turn off the display physically if it doesn't do so on its own (mine does after 15min of no signal being received)
6. Wait a little while for good measure
7. Turn the screen on, then wake the computer up

OBSERVED RESULT
Half the time, Plasma taskbar doesn't show up anymore, the start menu works when pressing Super but the only way to bring plasma widgets back is `systemctl --user restart plasma-plasmashell`.

EXPECTED RESULT
Plasma widgets should be there as normal

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: NixOS 25.05
KDE Plasma Version: 6.2.5
KDE Frameworks Version: 6.9.0
Qt Version: 6.8.1
Nvidia: 565.77

ADDITIONAL INFORMATION
I'm guessing this is caused by the HDMI display not reporting its resolution anymore when it powers down for real. It's an LG G2 TV.
KWin does have other issues with my HDMI displays, like it sometimes won't remember what refresh rate I'd chosen and defaults to 60. I don't have any displayport displays to test at the moment.

Comment 1 Nate Graham 2025-01-29 19:11:52 UTC

Are there any other negative effects, such as the desktop background turning black?

Is this happening on X11, Wayland, or both?

Comment 2 jakub 2025-01-29 20:20:04 UTC

This is on wayland, I haven't tested X11 (yet). Background remains the same as before, doesn't turn black.

Comment 3 jakub 2025-02-11 12:11:18 UTC

I've tested X11 for a bit and did not experience this. Will update if I do manage to reproduce it there.

Comment 4 gvgeo 2025-02-14 15:52:13 UTC

Same problem here
Wayland only
AMD gpu
DisplayPort QHD 165hz Monitor
Also tested combinations with hdmi HD TV. While it was connected there were no issues; even as the solo display output, disconnecting did not cause the problem.

Crashes occur only when the single monitor is disconnected, either by
idle timeout, or
removing cable or
turning it off completely (by default goes to standby and reports info).

Operating System: Garuda Linux (Arch)
KDE Plasma Version: 6.3.0
KDE Frameworks Version: 6.10.0
Qt Version: 6.8.2
Kernel Version: 6.13.2-zen1-1-zen (64-bit)

Related plasmashell output when the taskbar crashes:
Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)
qt.qpa.wayland: There are no outputs - creating placeholder screen
kde.plasmashell: requesting unexisting screen available rect -1
kde.plasmashell: requesting unexisting screen available rect -1
kde.plasmashell: requesting unexisting screen available rect -1
kde.plasmashell: requesting unexisting screen available rect -1
kf.plasma.quick: Exposed with no visual parent. Window positioning broken.
kf.plasma.quick: Exposed with no visual parent. Window positioning broken.
org.kde.applets.brightness: D-Bus action "KeyboardBrightnessControl" is not available at service "org.kde.Solid.PowerManagement"
org.kde.applets.brightness: D-Bus action "KeyboardBrightnessControl" is not available at service "org.kde.Solid.PowerManagement"

Comment 5 Haakon Nilsen 2025-02-15 07:38:28 UTC

It looks like several of the comments on #497204 (including mine) describe this same problem.

I'm definitely seeing the same thing on Plasma 6.3, also with HDMI, although with an Intel GPU.

Comment 6 gvgeo 2025-02-21 14:56:59 UTC

(In reply to Haakon Nilsen from comment #5)
> It looks like several of the comments on #497204 (including mine) describe
> this same problem.
> 
> I'm definitely seeing the same thing on Plasma 6.3, also with HDMI, although
> with an Intel GPU.

Indeed #497204 is very similar and probably same cause. 

I did check again. And although X11 does not appear to crash the panel(maybe it does, but recovers it too fast) when turning off the display,  soon turns on again as it does in wayland.
And has the same 2 errors in log without crashing:
kde.plasmashell: requesting unexisting screen available rect -1
kf.plasma.quick: Exposed with no visual parent. Window positioning broken.

Marking as duplicate, for now. If more differentiated info comes up, can reopen.

*** This bug has been marked as a duplicate of bug 497204 ***