Set Default Theme

[Jiří Janoušek]

Hello,

> How does Flatpak decide what theme to use if the currently installed theme is not available as a Flatpak?

Flatpak does not decide what theme to use, the toolkits do that. In
the case of GTK+ 3, the default/fallback theme is Adwaita.

>  Is it possible to force Flatpak to use a specific theme, even if it doesn't match the system theme?

In the case of GTK+ 3, you can set the `gtk-theme-name` property of
`GtkSettings` [1].

[1]: https://developer.gnome.org/gtk3/stable/GtkSettings.html#GtkSettings--gtk-theme-name

Best regards,

Jiří Janoušek