QtWayland.Compositor: respect mouse constraints

I really like the way QtWayland.Compositors approach.

I think it is the future of the Linux Desktop.

It seems there are only two major functionalities missing:

1) Middle click-paste aka primary selection which I read on the LXQT mailing list that 

     this feature is already in the pipeline for Qt 5.14

2)  Games need to be able to grab the mouse pointer.
 

plfiorini commented 13 days ago
Probably due to missing pointer_constraints_unstable_v1 and relative_pointer_unstable_v1protocol implementations in the compositor. 

 https://github.com/lirios/qml-xwayland/issues/4

It wouid be nice if this can make it into Qt at some point as well.

3) Remote/Screenshoot/Screencast 

     Not sure if Qt is the right place to implement this though.