Bug 469909 - Broken scaling in Qt6 apps when display scale is set to <100%
Summary: Broken scaling in Qt6 apps when display scale is set to <100%
Status: RESOLVED UPSTREAM
Alias: None
Product: kwin
Classification: Plasma
Component: wayland-generic (other bugs)
Version First Reported In: 5.27.5
Platform: Arch Linux Linux
: NOR normal
Target Milestone: ---
Assignee: KWin default assignee
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2023-05-17 19:39 UTC by Kit
Modified: 2023-05-18 10:45 UTC (History)
1 user (show)

See Also:
Latest Commit:
Version Fixed/Implemented In:
Sentry Crash Report:

Attachments
Comparison between Strawberry (Qt6 app) and Picard (Qt5 app) (18.25 KB, image/webp)
2023-05-17 19:39 UTC, Kit 		Details
qBittorrent (7.63 KB, image/webp)
2023-05-17 19:40 UTC, Kit 		Details
Audacious (7.23 KB, image/webp)
2023-05-17 19:40 UTC, Kit 		Details
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Description Kit 2023-05-17 19:39:53 UTC 
Created attachment 159043 [details]
Comparison between Strawberry (Qt6 app) and Picard (Qt5 app)

SUMMARY
In the Plasma Wayland session, setting the display scale factor to less than 100% causes several issues with Qt6 apps, making them unusable: incorrect scale of UI elements, flickering, items disappearing, among others. Scaling factors above 100% show no such issues - apps are functioning normally.
I've tried Strawberry Music Player, Audacious, qBittorrent and qt6ct - all of them exhibit similar problems. Qt5 apps are unaffected (see attachments).

STEPS TO REPRODUCE
1. Set display scale factor to any value below 100%
2. Launch a Qt6 app

OBSERVED RESULT
App launches normally; icon, text, interface scale is abnormal; several UI elements non-interactable; UI elements flickering and disappearing.

EXPECTED RESULT
A normally-functioning app.

SOFTWARE/OS VERSIONS
Linux Kernel: 6.3.2-arch1-1
KDE Plasma Version: 5.27.5
KDE Frameworks Version: 5.108.0 
Qt Version: 5.15.9

ADDITIONAL INFORMATION
Comment 1 Kit 2023-05-17 19:40:19 UTC 
Created attachment 159044 [details]
qBittorrent
Comment 2 Kit 2023-05-17 19:40:32 UTC 
Created attachment 159045 [details]
Audacious
Comment 3 David Edmundson 2023-05-18 10:45:55 UTC 
I submitted a patch to Qt.