wish: Automatic GTK dark theme switching (using the Freedesktop standard)

that's mostly obsolete nowadays
=> as long as the user can use system default and force dark whenever he wants = nothing is obsolete
But I agree, I have implemented this into my website (not online yet), and as I also switch night/day between light/dark theme, having app following this is a plus, not really better, but I probably miss that 4 mouse click is too much effort for some people at present.

a few comments for me later on:
- freedesktop is a Linux specification
- seems only available for Gnome and Granite
- for example no /appearence set in /org/freedesktop/ in Cinnamon or Mate
- even with GTK4, it requires libadwaita
- on GTK3 for now we can only rely on gtk-application-prefer-dark-theme
- gtk-application-prefer-dark-theme is not initialized on Windows 10, not 11

so it may be possible to implement a more accessible menu entry with force-light/force-dark, but default seems complex to get, on Linux at first, but probably more on Windows, didn't look at Mac.

It would be so much easier if GTK3/4 directly expose a reliable cross platform prefer-dark/light/default as well.
You seem to have connection with the developers: if you can suggest, please do :)

I know that at least KDE also supports it, and Cinnamon now supports it since last month: https://9to5linux.com/cinnamon-5-8-desktop-released-with-gestures-dark-mode-styles-and-more

I don't know what the status is for Mate, but I'm not holding my breath there, they are not exactly known as being the most change/future-oriented DE out there ;)

For Homebank itself, I don't think you actually need to use libadwaita to do this on GTK4, and as far I can tell you don't even need GTK4 to begin with (though it's probably nicer and I suppose you're planning to migrate to it anyway). LibHandy is not needed for GTK3 either. For instance, Firefox, LibreOffice 7.6 and Evolution (which are all GTK3 applications, or hybrids of GTK3 and other stuff) all support this.

I think it is done with the recommendations in the "Other" section here: https://gitlab.gnome.org/GNOME/Initiatives/-/wikis/Dark-Style-Preference#other

I hope this helps!

I asked around, and you can definitely support it "manually" even with a purely GTK3 app (without libhandy) or purely GTK4 app (without libadwaita). It's just more work.

The libadwaita pref works "out of the box" (basically zero lines of code needed specifically for this), and also works on macOS and Windows; the libhandy approach requires a single line of code, but doesn't work on macOS and Windows.