Draft: (need feedback) MacOS: draw native window controls within GTK titlebar
This is part of an effort to improve GTK integration within MacOS (see also: [macos] Use FullSizeContent for CSD (!5194 - closed)).
This is a draft PR. I'd like to get some initial thoughts on this approach before spending more time on this patch. This introduces a new type of button to the "gtk-decoration-layout" setting: "native".
There's a couple of notes (See "REVIEW NOTE") in that patch that I'd like to discuss.