SUMMARY The windows use the complete screen but are not maximized. STEPS TO REPRODUCE 1. Add "Placement=Maximizing" in [Windows] section of kwinrc. 2. Reboot. 3. Open "native" app. 4. Open Flatpak app. OBSERVED RESULT The "native" app is maximized, the Flatpak app uses the complete screen but is not maximized. In combination with "BorderlessMaximizedWindows=true", this is more obvious because the Flatpak app still shows a border. EXPECTED RESULT "Native" and Flatpak apps behave the same. SOFTWARE/OS VERSIONS KDE Plasma Version: 5.27.4 KDE Frameworks Version: 5.105.0 Qt Version: 5.15.9 ADDITIONAL INFORMATION Tested on Plasma Mobile. I only noticed it because the panels stayed transparent with the Flatpak app.
I suspect this is strongly related to Bug 469959, and fixing one may even fix the other.
This is on Wayland, right?
Yes.
Just tried on X11 in Plasma 6, and it worked as expected for the Flatpak of Welcome Center that I had lying around, which I know does not do any window geometry saving/restoring. What app are you testing with? Does it happen on X11 too, or only Wayland?
Tested again: it doesn't depend on Flatpak. I initially thought that some apps (e.g. native Dolphin and Gwenview) were maximized correctly. However, that wasn't really the case. They had only saved their previous maximized state and opened maximized because of that. After resizing them, they show the same behavior as all other apps. I didn't realize this initially because I couldn't resize the apps on Plasma Mobile. After switching back and forth between Plasma (Wayland), Plasma (X11) and Plasma Mobile (Wayland), I cannot reproduce the behavior anymore. I have no explanation what might have changed.
Aha, I know what this is: Bug 437089. It can either be fixed in every app to save its window state as "Maximized" rather than just saving its geometry, or it can be fixed in KWin to do the same thing on Wayland that it does on X11, which is to assume that when an app saves a window size that's identical to the screen geometry, this means "Maximized" and just automatically apply the Maximized state. *** This bug has been marked as a duplicate of bug 437089 ***
Unfortunately I mis-triaged this bug report, and sadly these are all app-specific issues. The problem is that some apps, when they maximize themselves, they also inappropriately save the new size they have in their maximized state. As a result, when you quit and re-launch such apps, one of the following things happens: - The window open in a non-maximized state with a window size equal to what it *would* have when maximized - The window opens in a maximized state, but when you de-maximize it, it doesn't change its size at all See Bug 478442 for an example affecting System Monitor. So I'm afraid we need a bug report for each individual KDE app that's affected. And for non-KDE apps that are affected, they'll need their own bug reports too.