OBSERVED BEHAVIOR The system tray disappeared (all of it) -- including, no way to open the application-start menu. A reboot did not fix it. Eventually I got it back by finding online advice (on my phone... couldn't open any apps, so, no browser on the computer) to ctrl-alt-F2 out, stop the display manager service, blast the cache and plasma config away and reboot. (https://forum.manjaro.org/t/applications-icon-missing-in-system-tray/109433/13) What was happening at that time: I was trying to mirror the display on a projector. The projector wasn't responding well to a higher display resolution, so I went down to 1024x768 (which I had used successfully on an older machine in the past). I didn't notice the tray was gone at first, but after closing a couple of app windows, the tray was gone, and the app-start menu was not responding to the Super key. EXPECTED BEHAVIOR HDMI connection + display resolution change should not bork the app menu and system tray. USER IMPACT: I was in a classroom with 50 students waiting for class to start, and unable to open any apps. In 12+ years of using Linux as my main operating system, this was my absolute worst experience. One suggestion: The app-start menu is critical. Without it, the only thing you can do is ctrl-alt-F2 to the console: no browser, no terminal, no system settings, not even logout / reboot. So it would be good to have some sort of failsafe -- even a prompt such as "KDE has detected a problem with cache and configuration files, clear and restart the desktop?" would be dramatically better than the "your system can't do anything and you had better hope you can find the answer on your phone" situation I was in. I left the bug as normal priority, but... app-start menu failures are catastrophic, rendering your computer into a brick. SOFTWARE/OS VERSIONS Linux/KDE Plasma: KDE Plasma Version: 5.24.7 KDE Frameworks Version: 5.92.0 Qt Version: 5.15.3 ADDITIONAL INFORMATION
Yikes, I'm so sorry this happened. Issues while trying to use a projector can be just the worst, and lead to extreme embarrassment. I've been there. It sucks. This is one of the reasons why multi-monitor handling was completely re-done in Plasma 5.27 to fix issues such as this one. Please update to 5.27 as soon as your distro offers it to you. It's an LTS, release so hopefully Kubuntu 22.04 will ship it as an update. Given how much the code governing these behaviors has changed in a year, there is unfortunately no practical way for us to debug the actual issue itself. And I'm afraid that with the release of the 5.27 LTS, the 5.24 LTS is no longer an LTS and hence no longer eligible for support or maintenance. If you need support for Plasma 5.24, please contact your distro, who bears the responsibility of providing support for older non-LTS releases. Best of luck with your projector setup after upgrading to Plasma 5.27 or later!
(In reply to Nate Graham from comment #1) > This is one of the reasons why multi-monitor handling was completely re-done > in Plasma 5.27 to fix issues such as this one. Please update to 5.27 as soon > as your distro offers it to you. It's an LTS, release so hopefully Kubuntu > 22.04 will ship it as an update. Sure, I understand. I'm on Ubuntu Studio (which I need for the audio setup). They're unlikely to upgrade Plasma directly... poking around now to try to find a ppa for it. Glad to hear this type of problem has received some attention.
Hm, it seems it's not possible in 22.04 (https://launchpad.net/~kubuntu-ppa/+archive/ubuntu/backports -- "This PPA will NOT currently receive Plasma 5.26 for Jammy 22.04, as this would break subsequent upgrades to Kinetic 22.10"). I'd have to upgrade my OS to 22.10... where I hesitate to do an OS upgrade during the semester. I'll think about it. In any case, this issue should be closed.
Brief update -- while understanding that any work on this issue has already gone into 5.27, I also need to report that the advice to "update to 5.27 as soon as your distro offers it" has proven to be untenable. I did try an upgrade to Ubuntu Studio 22.10 (with Plasma 5.27), as the bad behaviors were worsening. 22.10 completely broke the system. Screen updates, and mouse pointer updates, would occur only every 2-3 seconds. Launching Chrome produced a black screen and no way out, at which point I forced a shutdown and rebooted from the Ubuntu Studio 22.04 installer medium, and subsequently spent a "quality" afternoon reinstalling software. Now, this might be a result of bad interaction between the Ubuntu 22.10 kernel and the specific hardware -- maybe not directly Plasma's fault. But I did need to point out that "just upgrade" is not always feasible. Corruption of settings files reminds me of the early days of GTK Unity, btw.