OK, I'm going for weird bug of the year here =)
First, some background: I have global shortcuts set for maximizing and minimizing windows, configured in System Settings > Workspace > Shortcuts > Global Shortcuts. I have only one screen and only one panel, at the bottom.
Today the Device Notifier popup appeared after inserting a USB drive, at the time I went to minimize a window with my global shortcut. Apparently the Device Notifier stole the focus, because the "minimizing" happened to the DN popup, not to the currently active window.
Fair enough... but now, clicking on the Device Notifier, or any other, let's say, "plasma-native" icon in the systray that would show a popup (notifications and volume controller, in my case), no longer appear. Clicking them now shows a slight animation like focus is traveling from that icon to a point outside of the screen, somewhere at the far right/down corner, and no popup. Clicking the icon again reverses that "animation" and the "little light" comes back to the icon from that limbo-place xD
For comparison, I can trigger the same thing to the "calendar popup" that appears when clicking the Digital Clock plasmoid in the panel, but in this case, the calendar appears correctly after clicking the clock again, only this time, it appears with a "restore window from minimized state" animation, which looks weird, but it _is_ restored. It seems to be only an issue with the popups that come from the systray.
This happened to me in Plasma 5.8.6, but I've reproduced it on the first try on a Plasma 5.9.3 machine.
I realize this is a bug that very few people will ever trigger, but still ;)
Just for completeness: I just checked, and once this bug is triggered, the Battery and Brightness icon, the KDE Connect icon, and the Clipboard icon suffer the same fate, if they're in the systray.
Follow-up fun: Since I also have a global shorcut, I realized that triggering window maximization (and later, "window restore") also affects these popups (and in this case, the calendar too) in an ugly way. Nothing's lost in this case, at least xD
This on Plasma 5.10.4 now.
In the comment above, "Since I also have a global shorcut" was meant to end with "for maximizing windows" ;)
More additional info: If I trigger this bug and send the systray popups to "limbo", they're still accessible via Kwin's alt-tab list, appearing there as "Plasma".
Same happens on Debian Stretch system, with plasmashell 5.8.6
Related Debian bug report is at https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=876907
Confirmed on Arch Linux, plasma 5.12.2.
(In reply to JanKusanagi from comment #3)
> More additional info: If I trigger this bug and send the systray popups to
> "limbo", they're still accessible via Kwin's alt-tab list, appearing there
> as "Plasma".
Bugs below seem related:
*** This bug has been marked as a duplicate of bug 381242 ***
This bug still reproduces if patch from bug 381242 is applied over plasma-framework package from debian stretch.
I can reliably reproduce the bug by:
- have Telegram Desktop application started
- it has a systray icon, that by default becomes "hidden" i.e. shown only in systray's popup dialog
- have Telegram window opened on desktop different from current one
- click on Telegram's entry in system tray's popup dialog.
On click, desktop gets switched to where Telegram's window is. And after that, click on system tray no longer shows any dialogs up to when plasmashell is killed and restarted.
Although this may be caused by debian stretch having Qt 5.7 (which is less than 5.10)
Is it still affecting you? Latest stable Debian uses Qt 5.11, with this version is should be OK now.
Not on Debian buster