Bug 510245

Summary: Fullscreen can choose the wrong screen to maximize on when player hasn't been moved yet
Product: [Applications] Haruna Reporter: Simon Ra <wildcardc>
Component: genericAssignee: george fb <georgefb899>
Status: REPORTED ---    
Severity: normal    
Priority: NOR    
Version First Reported In: 1.5.0   
Target Milestone: ---   
Platform: Arch Linux   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description Simon Ra 2025-10-04 21:49:59 UTC 
SUMMARY
When closing the player on screen 1, then opening it on screen 2, Full screen will jump to screen 1 until the player is moved.

STEPS TO REPRODUCE
1. Open and move Haruna to screen 1.
2. Close Haruna.
3. Open Haruna on screen 2. (I do this via opening a video in Dolphin on screen 2)
4. Do no move the player window.
5. Full screen the player via F or double clicking.

OBSERVED RESULT
Haruna is full screen on screen 1.

EXPECTED RESULT
Haruna is full screen on screen 2.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Linux hostname 6.16.10-arch1-1 #1 SMP PREEMPT_DYNAMIC Thu, 02 Oct 2025 19:26:36 +0000 x86_64 GNU/Linux
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.18.0
Qt Version: 6.9.2

ADDITIONAL INFORMATION
After exiting full screen once, the player behaves as expected.
Comment 1 Simon Ra 2025-10-07 22:10:35 UTC 
I neglected to mention that this is under kwin/wayland.

I also have this bizzare finding:
I can fix this issue by lowering the "width" and "height" properties of ApplicationWindow in Main.qml. This may affect your abillity to reproduce the issue.

the default of 1000x600: breaks
1000:1000: breaks
800:800: works
500x300: works

So, my best guess is that somewhere deep in Qt/QML there is a branch for how close the non-fullscreen buffer is to the one required for fullscreen, and then some kind of divergence between the code paths causes the bug. However, I have not managed to make a minimal QML reproduction in order to turn this into a QT bug report, so there may be other factors.

This could mean that these values are also specific to your monitor resolution(s). I'm using two 1080p Displays here.