Bug 378350

Application: plasmashell 5.9.3

Qt Version: 5.7.1
Frameworks Version: 5.28.0
Operating System: Linux 4.8.0-41-generic x86_64
Tried Ubuntu 16.10 and KDE Neon Developer Edition (Stable branches)

Steps to reproduce (I will describe my typical use case):

1. Given system with two displays (e.g. one laptop and one external, or two external displays).
2. (Not sure if it's necessary) Set number of virtual desktops to >=2
3. The main display by default has a panel with Task Manager widget on the bottom. Right click on task manager -> Settings -> Check "Show only tasks from current screen", "Show only tasks from current desktop" and "Show only tasks from current activity".
4. Add an empty panel to the other display, add the Task Manager widget to it, check the same "Show only tasks from current screen", "Show only tasks from current desktop" and "Show only tasks from current activity" options in its  settings.

Now we have on each display own Task Manager widget which displays only windows for current display and virtual desktop. That's what I want, everything's great.

But if I unplug external display or plug-in a new one, then Task Manager widget shows no windows until I uncheck "Show only tasks from current screen" option. But in that case it shows windows from all the screens, and that's not what I need.

The only workaround is to restart plasmashell (killall plasmashell, kstart plasmashell), which is tedious and not always works as expected.