Yes, it needs to be supported by the UI kit. That's why GTK needs to support this, not just Gnome. Gnome uses GTK4, which supports this. Mate uses GTK3, which does not.
KDE Plasma uses QT6, which also supports this.
KDE Plasma uses QT6, which also supports this.
> Gnome uses GTK4, which supports this. Mate uses GTK3, which does not.
Damn. I tend to build against an older GTK3 version, because GTK deprecated so much good stuff, but that means my programs won't work correctly for that. I need to look whether it's easy to backport this.