Bug 408247

Summary:	[Dual monitor, powersave] taskbar showing windows from the wrong screen
Product:	[Plasma] plasmashell	Reporter:	Andreas Nordal <andreas_nordal_4>
Component:	generic-multiscreen	Assignee:	Aleix Pol <aleixpol>
Status:	RESOLVED DUPLICATE
Severity:	normal	CC:	alexander.stehlik, armando.ota, johannespfrang+kde, kdebugs, l.arvanitis, mbarnes536, michael, nate, plasma-bugs, rnp, sirronaldreginald
Priority:	NOR
Version:	5.15.4
Target Milestone:	1.0
Platform:	openSUSE
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description Andreas Nordal 2019-06-03 10:13:38 UTC

SUMMARY
When I come back to the computer after the screens have turned off, some times both task managers only show the windows of the left screen, or only the windows of the right screen, despite being configured to show the windows from their respective screens. Reproducibility: 1/10 (guesstimate).

STEPS TO REPRODUCE
1. Have 2 screens permanently connected.
2. Have 2 panels, one on each screen.
3. Configure each panel's task manager to only show windows from their own screens.
4. Turn both screens off, or enable screen power saving and wait for them to do it themselves.
5. Turn both screens on, or in the screen power saving case, wiggle the mouse or whatever for them to come on.

OBSERVED RESULT
Some times, both task managers only show windows from the left screen, and some times both only show windows from the right screen, and some times they show the windows from their own screens.

In this botched state, the phenomenon does not go away if I disable and re-enable the setting to only show windows from the same screen – looks like the affected task manager "thinks" it's on the other screen!

What works to resolve the botched state, is to turn both monitors off and on as simultaneously as possible. It often takes a couple of tries.

EXPECTED RESULT
Each task manager should show the windows from their own screen, as configured.

SOFTWARE/OS VERSIONS
OpenSuse Tumbleweed
KDE Frameworks 5.57.0
Qt 5.12.2
plasma5desktop-5.15.4-1.1

ADDITIONAL INFORMATION
1. This bug is at least as old as this computer (december 2015).
2. My screens are identical (Dell), both connected via Displayport to the same Intel IGP.
3. An even rarer phenomenon that also happens in the same scenario is that one screen doesn't turn on. In this case, I can wake the unwilling screen up by going into the Linux console (Ctrl+Alt+F1) and start Weston (`weston-launch`). Then, if I quickly go back to X (Alt+F7), the screens will flicker briefly, but remain on.

Comment 1 rnp 2020-02-07 13:48:31 UTC

The bug is alive and doing well. This is my system configuration:

Monitor 0:              3840x2160 @60Hz
Monitor 1:              2560x1440 @60Hz
Operating System:       Arch Linux 
KDE Plasma Version:     5.17.5
KDE Frameworks Version: 5.66.0
Qt Version:             5.14.1
Kernel Version:         5.4.15-arch1-1
OS Type:                64-bit
Processors:             8 × Intel® Core™ i7-6700 CPU @ 3.40GHz
Memory:                 47.0 GiB of RAM


In my case, the workaround is:

1. delete task manager from the panel in monitor 0
2. add new task manager to the panel in monitor 0
3. under behaviour section, configure the filters to:
  3.1. Show only tasks from the current screen
  3.2. Show only tasks from the current desktop

Comment 2 Scott 2020-05-12 22:38:25 UTC

I'm also experiencing this issue. Occurs when the monitors are switched on and off, and persists after a reboot.

SOFTWARE/OS VERSIONS
Operating System: Solus 4.1
KDE Plasma Version: 5.18.4
KDE Frameworks Version: 5.69.0
Qt Version: 5.13.2
Kernel Version: 5.6.4-152.current
OS Type: 64-bit
Processors: 12 × AMD Ryzen 5 3600 6-Core Processor
Memory: 23.5 GiB of RAM

Comment 3 sparhawk 2020-07-30 07:14:57 UTC

I only just came across this bug now. I've been running Plasma for years, but this is the first occurrence, perhaps after a Plasma upgrade yesterday to 5.19.4? I ran into this bug after a reboot. For me, it was enough to restart Plasma to fix it, i.e. `kbuildsycoca5; kquitapp5 plasmashell; plasmashell`

Operating System: Arch Linux
KDE Plasma Version: 5.19.4
KDE Frameworks Version: 5.72.0
Qt Version: 5.15.0
Kernel Version: 5.4.53-1-lts
OS Type: 64-bit
Processors: 8 × Intel® Core™ i7-7700 CPU @ 3.60GHz
Memory: 31.2 GiB of RAM
Graphics Processor: Mesa Intel® HD Graphics 630

Comment 4 Johannes Pfrang 2020-07-30 09:32:11 UTC

This might be a duplicate of bug 394532, which was fixed for Plasma 5.20, but unfortunately wasn't backported (yet?):

https://invent.kde.org/plasma/plasma-workspace/-/merge_requests/36

Comment 5 Armando Ota 2020-09-08 08:50:05 UTC

same problem here ... 
computer with 2 or 3 monitors. 
After wakeup ot lock screen all taskbars show only application windows from one screen 
my taskbar settings: 
Group : Do not group

Sort: manualy

On middle-click: new instance

Mouse wheel: Cycle through tasks
Show only 
[X] From current screen 
[X] From current desktop
[X] From current activity
[ ] That are minimized

Comment 6 michael 2021-03-10 08:14:37 UTC

Adding my system to the list

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04.5 LTS
Release:        18.04
Codename:       bionic

$ plasmashell --version
plasmashell 5.12.9

But I could observe the problem on opensuse tumbleweed, opensuse 15.2 and centos8.

@rnp's solution is the same that I apply (re-add and reconfigure taskmanager)

Comment 7 Nate Graham 2021-08-17 01:56:25 UTC


*** This bug has been marked as a duplicate of bug 356225 ***