https://bugs.kde.org/show_bug.cgi?id=520338
Bug ID: 520338
Summary: Plasma 6.7 beta UI font preferences not respected by
apps using the KDE Flatpak runtime - QFont error
Classification: I don't know
Product: kde
Version First unspecified
Reported In:
Platform: Flatpak
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Created attachment 192416
--> https://bugs.kde.org/attachment.cgi?id=192416&action=edit
Demo of the issue, using Kate Flatpak as an example.
DESCRIPTION
On Plasma 6.7 beta (on KDE Linux), Flatpak apps using the org.kde.Platform
runtime do not apply my Plasma font preferences in their UI.
Flatpak apps using other runtimes *do* respect my Plasma font preferences, so
this isn't a generalised Flatpak issue.
I see this issue on Plasma 6.7 beta on KDE Linux, but it doesn't happen on
Plasma 6.6.4 on Fedora. So it doesn't seem to be an issue purely with the
Flatpak runtime - it's somehow the interaction between Plasma 6.7 font settings
and the runtime.
STEPS TO REPRODUCE
1. In Plasma System Settings, configure a non-default font for "General",
"Small", "Toolbar", "Menu" and "Window title".
2. Launch a Flatpak app that uses the org.kde.platform.
OBSERVED RESULT
The UI fonts used in the app are not those that were configured in Plasma
System Settings.
EXPECTED RESULT
The app UI should use the fonts configured in Plasma System Settings.
SOFTWARE/OS VERSIONS
Operating System: KDE Linux 2026-05-18
KDE Plasma Version: 6.6.90
KDE Frameworks Version: 6.27.0
Qt Version: 6.11.1
ADDITIONAL INFORMATION
When I launch the affected Flatpak apps from the terminal, I see error messages
like this:
QFont::fromString: Invalid description
'Cantarell,10,-1,5,400,0,0,0,0,0,0,0,0,0,0,1,,0,0'
QFont::fromString: Invalid description
'Cantarell,10,-1,5,400,0,0,0,0,0,0,0,0,0,0,1,,0,0'
QFont::fromString: Invalid description
'Cantarell,10,-1,5,400,0,0,0,0,0,0,0,0,0,0,1,,0,0'
QFont::fromString: Invalid description
'Cantarell,9,-1,5,400,0,0,0,0,0,0,0,0,0,0,1,,0,0'
QFont::fromString: Invalid description
'Cantarell,8,-1,5,400,0,0,0,0,0,0,0,0,0,0,1,,0,0'
The behaviour is consistent among KDE and non-KDE apps that use the
org.kde.Platform runtime, and across different versions of the runtime. For
example, all of the following have the issue:
net.ankiweb.Anki (org.kde.Platform/x86_64/6.10)
org.videolan.VLC (org.kde.Platform/x86_64/5.15-25.08)
org.kde.kolourpaint (org.kde.Platform/x86_64/6.10)
org.kde.krename (org.kde.Platform/x86_64/5.15-25.08)
The behaviour is not seen for Flatpak apps that use non-KDE runtimes. Those
correctly use the fonts configured in Plasma Settings.
The behaviour is also not seen for non-Flatpak KDE apps (e.g. Dolphin).
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