Roman Gilg authored Jan 02, 2020 and David Edmundson committed Feb 28, 2020

Summary:
First we need to set a transformation, then update the backend. In DRM the
cursor gets updated and needs the new transformed size.

Longterm we need a pending state if we want to apply configuration changes
atomically or deny them.

Test Plan: Compiles.

Reviewers: #kwin, zzag

Reviewed By: #kwin, zzag

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D25903