Summary:
The Qt Wayland support for subsurfaces is broken in many ways, producing
graphical glitches and crashes:
https://bugreports.qt.io/browse/QTBUG-54888 for instance.
Using a QQuickWidget instead of a QQuickView avoids those issues, with
the additional benefit of a nicer API.
Test Plan:
Opened the KCM with kcmshell and systemsettings, no subsurfaces used
anymore.
Reviewers: #plasma, graesslin, davidedmundson
Reviewed By: #plasma, graesslin, davidedmundson
Subscribers: kwin, plasma-devel, #kwin
Tags: #kwin
Differential Revision: https://phabricator.kde.org/D11066
68a2ec5d63