Both, but it's up to the application to choose what they want on whichever particular platform they're targeting by using gtk_window_set_decorated(). I have so

Both, but it's up to the application to choose what they want on whichever particular platform they're targeting by using gtk_window_set_decorated(). I have some blog posts from the effort to write the new backends which gives some additional details. https://blogs.gnome.org/chergert/2022/02/14/modernizing-gtks-macos-backend-again/ https://blogs.gnome.org/chergert/2022/02/14/modernizing-gtks... https://blogs.gnome.org/chergert/2020/12/15/gtk-4-got-a-new-macos-backend-now-with-opengl/ https://blogs.gnome.org/chergert/2020/12/15/gtk-4-got-a-new-... https://blogs.gnome.org/chergert/2021/02/24/gtk-4-ngl-renderer/ https://blogs.gnome.org/chergert/2021/02/24/gtk-4-ngl-render...