Bug 388759

This is plasmashell bug.
"kquitapp plasmashell; plasmashell" fixes the issue.

Also, this can only be triggered when switching to external display required resolution switching. Bug is not reproducible without resolution switching involved, also not reproducible when you just change resolution of laptop's display, without external display connected.
Also reproducible without kwin compositing enabled.

I can confirm this issue.

HP ProBook 6560b
Intel i915
KDE Neon 5.11
Linux komputer 4.10.0-26-generic #30~16.04.1-Ubuntu SMP Tue Jun 27 09:40:14 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

I can confirm this issue.

Acer S7
Intel i7-4500
KDE Neon 5.11
Linux Computer 4.4.0-104-generic

I can confirm. Manually running xrandr to modify the screen configuration will trigger this behaviour.

I originally reported this behaviour July 2017 as Bug 382618. Back then, I did not link it to a screen reconfiguration, but meanwhile I identified this as the trigger.

I'm routinely killing plasmashell to get behaviour back to normal...

(In reply to Gunter Ohrner from comment #4)
> I can confirm. Manually running xrandr to modify the screen configuration
> will trigger this behaviour.

Linux Zweiblum 4.13.0-17-generic #20~16.04.1-Ubuntu SMP Mon Nov 6 14:18:00 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

i7-3540M
00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)

$ dpkg -l | egrep 'kwin|plasma' | cut -c1-75
ii  kdeconnect-plasma                                           1.2-0neon+1
ii  kdeplasma-addons-data                                       4:5.11.4-0n
ii  kwin                                                        4:5.11.4-0n
ii  kwin-addons                                                 4:5.11.4-0n
ii  kwin-common:amd64                                           4:5.11.4-0n
ii  kwin-data                                                   4:5.11.4-0n
ii  kwin-style-breeze                                           4:5.11.4-0n
ii  kwin-x11                                                    4:5.11.4-0n
ii  libkdeclarative5                                            4:4.14.16-0
ii  libkf5plasma-dev                                            5.41.0-0neo
ii  libkf5plasma5:amd64                                         5.41.0-0neo
ii  libkf5plasmaquick5:amd64                                    5.41.0-0neo
ii  libkf5windowsystem-dev                                      5.41.0-0neo
ii  libkwin4-effect-builtins1:amd64                             4:5.11.4-0n
ii  libkwineffects11:amd64                                      4:5.11.4-0n
ii  libkwinglutils11:amd64                                      4:5.11.4-0n
ii  libkwinglutils6                                             4:5.4.3-0ub
ii  libkwinxrenderutils11:amd64                                 4:5.11.4-0n
ii  libkwinxrenderutils6                                        4:5.4.3-0ub
ii  libplasma-geolocation-interface5                            4:5.11.4-0n
ii  libplasma3                                                  4:4.14.16-0
ii  libsmokeplasma3                                             4:4.14.2-0u
ii  muon-discover                                               4:5.11.4-0n
ii  muon-notifier                                               4:5.11.4-0n
ii  muon-updater                                                4:5.11.4-0n
ii  plasma-dataengines-addons                                   4:5.11.4-0n
ii  plasma-desktop                                              4:5.11.4-0n
ii  plasma-desktop-data                                         4:5.11.4-0n
ii  plasma-discover                                             5.11.4-0neo
ii  plasma-discover-common                                      5.11.4-0neo
ii  plasma-discover-private                                     5.11.4-0neo
ii  plasma-discover-updater                                     5.11.4-0neo
ii  plasma-framework                                            5.41.0-0neo
ii  plasma-integration                                          5.11.4-0neo
ii  plasma-look-and-feel-org-kde-breezedark-desktop             4:5.11.4-0n
ii  plasma-nm                                                   4:5.11.4-0n
ii  plasma-pa                                                   4:5.11.4-0n
ii  plasma-runners-addons                                       4:5.11.4-0n
ii  plasma-scriptengine-javascript                              4:15.12.3-0
ii  plasma-scriptengine-superkaramba                            4:15.08.3-0
ii  plasma-vault                                                5.11.4-0neo
ii  plasma-wallpapers-addons                                    4:5.11.4-0n
ii  plasma-widget-message-indicator                             0.5.8-3    
ii  plasma-widgets-addons                                       4:5.11.4-0n
ii  plasma-workspace                                            4:5.11.4-0n
ii  qml-module-org-kde-kwindowsystem:amd64                      5.41.0-0neo

Created attachment 109785 [details]
plasma restart script

(In reply to Gunter Ohrner from comment #4)
> I'm routinely killing plasmashell to get behaviour back to normal...

Here's a temporary hack. Save this as "plasmarestart.sh", chmod +x plasmarestart.sh, and add to KDE's autorun.

I think, that this is the behavior I see and for which I reported a bug previously. It had been moved to https://bugs.kde.org/show_bug.cgi?id=378010 . I did not know about the constant screen repaints then, but activating "Show Paint" shows that this is the case. Restarting plsasmashell does remove the phenomenon instantaneously, but does not fix the bug.
As a work around, I am using the script below. This will take care of automatically restarting plasmashell, but note that it causes that you will see the taskbar rebuild each time you change displays or unlock the screen.

#!/bin/bash

dbus-monitor --session "type='signal',interface='org.freedesktop.ScreenSaver'" |
  while read x; do
    case "$x" in 
      *"boolean true"*) echo "lock";;
      *"boolean false"*) kquitapp5 plasmashell; sleep 2; kstart5 plasmashell;;  
    esac
  done &

dbus-monitor --session "type='signal',interface='org.kde.kscreen.Backend',path='/backend',member='configChanged'" |
    kquitapp5 plasmashell; sleep 2; kstart5 plasmashell;

Sorry valdikss@gmail.com . I did not see your last post. That script seems to amount to the same.

Can everyone please mention their Qt versions when commenting. 

There have been multiple potentially relevant commits between Qt5.9 and 5.10. 

Realistically I don't have time to look at Qt issues < 5.10 as they might already be fixed.

(In reply to David Edmundson from comment #9)

Qt5 5.9.2-1.fc27 on Fedora
Qt5 5.9.3-0neon+16.04+xenial+build22 on Neon gitstable

The issue is probably in Qt, not Plasma. Manjaro 17.1.1 with Qt 5.10 is not affected.

It would be helpful if anyone can point to exact patch which fixes this issue, so distro maintainers can apply it on top of current Qt version.

Likely candidate are:
6990ae6c1bad32952e371fa72bee65a7af11c313
9538cd7fbe43b1479f23a37bc8f19012981257a6
93df3e3a3118080dcd6d9416d1622b88d99c4b8d

(In reply to David Edmundson from comment #13)
> Likely candidate are:
> 6990ae6c1bad32952e371fa72bee65a7af11c313
> 9538cd7fbe43b1479f23a37bc8f19012981257a6
> 93df3e3a3118080dcd6d9416d1622b88d99c4b8d

The last two were already included in 5.9.2, but the first one is exactly what you need. It fixes the issue.

I filled a bug to Fedora bugtracker: https://bugzilla.redhat.com/show_bug.cgi?id=1536606
Please do the same for your distro if you're affected.

KDE Neon: https://bugs.kde.org/show_bug.cgi?id=389218