_GTK_THEME_VARIANT xprop ignored on Fedora 38

[subpop]

It looks like the xprop _GTK_THEME_VARIANT is ignored by clients on Fedora 38. I've verified that the property _GTK_THEME_VARIANT is set to dark:

[link@localhost ~]$ xprop -name Spotify | grep GTK_THEME
_GTK_THEME_VARIANT(UTF8_STRING) = "dark"

But the window title bar is still light.

[TingPing]

To be clear, that means its ignored by the window manager and/or the window manager doesn't have a GTK3 theme with that variant.

This is somewhat investigated in #236

I'm not sure what this package can do about it.

[subpop]

I'm not clear where the issue exists. If the xprop is a hint to the window manager, is it mutter that's ignoring the hint and not setting the variant?

[TingPing]

It is handled in mutter.

[TingPing]

I think GNOME-Shell just no longer uses GTK3: https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2655