Earlier quoted context omitted.
>> I'm not optimistic about Wayland, since early on they decided not to use an extension language, and that's not something you can have a change of heart about later, and then just nail onto the side. I don't see a need for an extension language for a compositor. A miminum of DE features will be implemented in Wayland compositors and everything else will be other programs - write them in what you like. Or am I wrong…
The extension language is most useful for the window manager, which should be running in the same address space as where the events are being generated and processed.
Maybe that's a Wayland problem though, with the way it combines the windows manager with everything else into one process.