Bug 511711 - Qt flatpak apps require being restarted to fully switch from light to dark, making them inconsistent when using the automatic theme switcher
Summary: Qt flatpak apps require being restarted to fully switch from light to dark, m...
Status: CONFIRMED
Alias: None
Product: plasmashell
Classification: Plasma
Component: Day/night schedule (other bugs)
Version First Reported In: 6.5.1
Platform: Flatpak Linux
: NOR minor
Target Milestone: 1.0
Assignee: Plasma Bugs List
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2025-11-06 12:59 UTC by SaulFG
Modified: 2025-12-01 20:13 UTC (History)
2 users (show)

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


Attachments
Screenshot of the problem (597.13 KB, image/png)
2025-11-06 12:59 UTC, SaulFG
Details

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Description SaulFG 2025-11-06 12:59:17 UTC
Created attachment 186541 [details]
Screenshot of the problem

SUMMARY
Having activated the new auto dark mode feature in Plasma 6.5, when the sun sets my theme supposedly switches to dark mode. I say ‘supposedly’ because any flatpak apps which are open at the moment the change occurs need a restart to make the change effective.

For reference, the attached picture has an instance of Konsole installed as a system package (right) and an instance of Konsole as a flatpak (left). As you can see, having changed the theme from dark to light, only the titlebar of the flatpak konsole has changed colors, while the app itself is still in dark mode, and will remain so until I close and reopen the window.

This happens with pretty much all Qt apps installed from flatpak, such as Okular, Gwenview, Kile, etc. Those same apps installed as rpms change themes perfectly.

This makes the new theme switcher feature unusable in flatpak-reliant systems (e.g. Kinoite, Bazzite, etc)

STEPS TO REPRODUCE
1. Open a Qt app installed from flatpak
2. Switch to dark theme
3. Observe that the app does not change to dark theme until restarted

OBSERVED RESULT
Apps do not properly switch from dark to light theme

EXPECTED RESULT
Apps should switch themes

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora Kinoite
KDE Plasma Version: 6.5.1
KDE Frameworks Version: 6.19.0
Qt Version: 6.10.0

ADDITIONAL INFORMATION
None.
Comment 1 TraceyC 2025-11-25 21:51:03 UTC
I'm not able to reproduce this with Qalculate (from flatpak) on Plasma built from git-master or 6.5.3. I only see a (slightly different0 problem with Konsole (native package)

I also cannot reproduce with Qalculate when I manually switch from Breeze Light to Dark or vice versa from System Settings->Quick Settings, all windows change theme correctly (Qt and non-Qt, flatpak and native). Konsole still does not change theme.

Steps to reproduce:

1. Set system theme to Automatic (Breeze)
2. Open a Qt flatpak app like Qalculate, Konsole (native), 
3. Use System Settings->Quick Settings to change the theme to Automatic (Breeze)
4. In Day-Night Cycle set the sunset time to a minute in the future

When the sunset time triggered, all apps except Konsole changed to their dark themes
They also changed completely to their correct theme right after I manually changed the global theme to Breeze Dark or Light as expected
This also isn't a problem for non-Qt flatpak apps. Obsidian Notes changed when I changed the global theme as well.

It looks like improvements have been made since 6.5.1 but there are different issues.
Those with more knowledge of this feature will have to take a closer look
Comment 2 SaulFG 2025-12-01 20:13:16 UTC
I was surprised by the lack of replicability, so since I had some time I run some experiments with different distros in my spare computer. I have managed to replicate the issue exactly as described in fresh installations of Fedora 43, Arch and Tumbleweed.

Could this mean that in the system where this problem could not be replicated some non-default setting or flatpak permission is present that fixes the issue?