That's exactly what happened. This is the original intent for subsurfaces. A bunch of Wayland developers got together and wrote the spec a long time ago. The on

That's exactly what happened. This is the original intent for subsurfaces. A bunch of Wayland developers got together and wrote the spec a long time ago. The only thing happening now is Gtk making use of them transparently in the toolkit. Subsurfaces didn't have bug-free implementations for a while, so maybe some people avoided them. But I know some of us emulator programmers have been using them for output (especially because they can update asynchronously from the parent surface), and I think a couple media players do, too. It's not something that most applications really need.