Flathub provided package does not follow system theme

[RobusTetus]

Issue #376 was closed but not fixed. Feature was implemented back in #316 but does not work in flatpak.

[nekohayo]

It doesn't seem to work outside of flatpak either? I grabbed the package from Fedora 40 (even though I'm running it on Fedora 39) and there is no system / auto theme; the preferences dialog only lets you choose between light and dark, and doesn't switch between the two when the system's freedesktop dark mode activates/deactivates:

It seems Setzer is now using GTK4+libadwaita. In case this is useful, https://gitlab.gnome.org/GNOME/Initiatives/-/wikis/Dark-Style-Preference seems to be the reference about it, to monitor the system state etc.

[cvfosammmm]

I'm a bit afraid of making this dialog more complicated, but I think the following could work. Add an option (under options) "Choose separate light / dark color scheme (follow system theme)". Toggling that will replace the "Color Scheme" section with two sections of the same kind, one labeled "Light Color Scheme" and one "Dark Color Scheme". The first of these always has the same value as the default "Color Scheme" option.