AppImages do not automatically adapt to system font changes on KDE

[TheTechnician27]

Summary

On KDE Wayland, AppImage applications do not automatically adapt to system font changes. Instead, you need to restart the application first. For example, if I change from 'Noto Sarif 10-point' to 'Monospace 14-point', neither the font nor the size changes; I have to first close out of the AppImage then reopen, at which point the text will have changed.

I originally found this testing PCSX2, but I confirmed it in the Kdenlive AppImage. Neither Flatpaks nor applications installed using pacman appear to have this problem. I cannot yet speak either for X11 or for other DEs such as GNOME.

Steps to Reproduce

1. Open an AppImage application in KDE.
2. While the application is open, go to "Texts & Fonts" and change the font style and/or size under 'General'.

Observed Result

• The font will not change in the AppImage application.
• However, it will update automatically in your non-AppImage applications.
• If you close out of and reopen the AppImage application, the font is now updated accordingly.

Expected Result

AppImage applications should update fonts automatically like Flatpaks and Arch packages.

Configuration

• Linux kernel: 6.12.45-1-lts
• Distribution: EndeavourOS
• KDE Plasma Version: 6.4.4
• KDE Frameworks Version: 6.17.0
• Qt Version: 6.9.2
• Graphics Platform: Wayland
• CPU: AMD Ryzen 5800X
• GPU: Nvidia GeForce GTX 1070

(largely copy–pasted from a KDE bug report I filed here)

[Samueru-sama]

Do you have the issue with this AppImage?