It was only partially implemented and not useful for xrdesktop.

Check out the christoph/window-relative branch if you have use for it.

They are not useful

This eliminates transitive linking to the platform specific input libraries.

Example: Gnome shell is a wayland compositor and an X11 window manager. Previously it had to link both a wayland backend and an X11 backend.

Note: The client is responsible for the window being focused e.g. for character input!

TODO: xdotool

This will be useful for wayland when synthesizing input directly for a window.