Why isn't Xwayland just a Wayland client?

[Daniel Stone]

Hi Joseph,

On 6 September 2017 at 11:56, Joseph Burt <caseorum at gmail.com> wrote:
> I'm thinking this might be a job for a bit of translation shim within
> Xwayland. Everything an X client needs either has a Wayland equivalent
> (through an X server and a little translating XWM shim) or, where
> forbidden by Wayland, can be stubbed out with a few white lies e.g.
> "There are no other clients," "Your relative position is global."
>
> I'm thinking of taking a whack at this. Are there any dragons in the
> Xserver I should be aware of?

I really wouldn't recommend doing this.

No-one wanted to write yet another X11 window manager; what's there is
there by necessity so as not to break existing clients. For instance,
pop-up menus rely heavily on the global co-ordinate system remaining
intact.

The window management side is surprisingly complex and fiddly; it's
also something that the compositor has to be in charge of, so it can
implement its policy. Removing the WM from the compositor just means
that we need protocol from Xwayland to the compositor, proxying window
management to allow the compositor to make those decisions. Rather
than building that out, we decided to just reuse what was there.

Cheers,
Daniel