[OS X/Wayland] using WIds created by a different process to create KMessageBox'es and other widgets/windows

[René J. V. Bertin]

Kai Uwe Broulik wrote:

> ‎> On OS X (and MS Windows?),
> 
> And Wayland, so it affects Linux, too.

Yes, I learned that while composing my message (cf. the subject).

FWIW, I just provided an initial/WIP implementation of a KWindowSystem plugin 
for OS X: https://git.reviewboard.kde.org/r/126291/

R.