I use MEGA (also known as MEGAsync, mega.nz) cloud synchronization. The app is set to autostart. On Wayland session the app will always notify about it not being able to find a system tray and that it will not function properly. The program keeps running (/usr/bin/megasync process is alive) but the tray icon is missing. Spawning MEGAsync from krunner opens the app's window but it's aligned all the way to the left whereas it should be opened nearby the tray. My tray is located on the right. The panel is on top edge of the screen. When the process is killed manually, the app can be started with the icon in the tray. It's functional - clicking spawns the app's windows (again on the left, though). Nearly all dialogs given by the application cannot be read and there's nothing I can do with them. It may be related to the screen being HiDPI (3200x1800 with 2x scaling). The dialogs are tiny and nearly no text is visible. I cannot take any actions. This includes: - opening the app's windows selecting Syncs->Add sync->Dialog cannot be seen, - opening a file share link (example from my cloud https://mega.nz/#!ZgQgHDZL!OeKVISti6vfcvBh85Z0rOj1jwi1fP0AZ9Jhx548T9Fc) and using Download with MEGAsync -> dialog is nowhere near being operational, - settings menu Under X - none of those issues happen.
Is the app using native Wayland or Xwayland?
Error message had an X icon, so I presume it's running XWayland. Today I updated XWayland to 1.19 - same issues. Although without scaling on I can see more inside the windows.
Update with Plasma 5.10.1. I stopped using the MEGA sync app on startup, but for the sake of this issue I wanted to test what is happening now. Probably due to changes in scaling and forcing DPI for fonts, I can now see the entire error dialog: http://imgur.com/a/R1hTu. And besides that - nothing changed. I need to kill the app process and start it again in order for it to appear in the tray and be accessible for any interaction.
Confirming this bug in: Distribution: Netrunner Rolling KDE Plasma Version: 5.10.4 KDE Frameworks Version: 5.36.0 Qt Version: 5.9.1 Kernel Version: 4.9.43-1-MANJARO OS Type: 64-bit xorg-server-xwayland 1.19.3-3 wayland 1.14.0-1 wayland-protocols 1.10-1 Also i noticed that MEGAsync's settings window doesn't have KWin decoration and MEGAsync's settings window is displaying not with MEGAsync logo but with default Wayland icon in task manager.
So the fact that it shows Qt window decorations says a lot. The application seems to ship it's own Qt and due to that our integration doesn't work. This could also explain why it doesn't find the systray. If system Qt would be used, the app would work fine. My suggestion is to force the application to use xcb, then it should also find the systray.
If it bundles its own Qt, there's not much we can do. Once they upgrade they'll get a Qt with built in SNI support.
We also don't force QT_QPA_PLATFORM anymore, so older Qt will use XCB by default anyway.