Comment 27 for bug 1704870

(In reply to Pierre Ossman from comment #23)
> It sounded like one of your (two) grab extensions was specifically for O-R
> windows?

That's correct.

> Fullscreen via EWMH should be able to make do using the other
> proposed Wayland extension.

Maybe you should take this discussion on the thread upstream where this would be more appropriate than in a downstream bugzilla.

On Wayland, an X11 application running on Xwayland uses the "regular" X11 window manager which implements EWMH, it does not need any specific Wayland protocol for that, it just uses the good ol' X11 protocols.

See https://wayland.freedesktop.org/xserver.html

For example, on GNOME, mutter plays the role of Wayland compositor and X11 window manager, and mutter/gnome-shell itself relies heavily on X11/Xwayland even when running as a Wayland compositor. An X11 client wishing to map its X11 window fullscreen using EWMH does not need an O-R, it just sents the relevant WM hint on the window and the X11 window manager will map that window fullscreen if applicable.

The protocol for Xwayland I sent upstream is for O-R windows, those are not focused by X11 window managers (basically they are mostly ignored by X11 window managers, by definition, even if that's not true with compositor managers which need to draw them), so that an X11 client issuing a grab on its X11 window will never get the keyboard focus when running on Xwayland because Wayland does not have any grab mechanism to match the X11 grabbing protocol.