Summary:
This change fixes the hotspot calculation by introducing a dedicated
matrix to map the hotspot.
To better test the hotspot a small test application is added. The app
renders a red point at the cursor position and uses a cross for cursor
with the hotspot position being transparent. So if KWin renders the
cursor at the correct position a red point is visible in the center of
the cross. The test app supports several cursor hotspot positions:
* center (default)
* top left
* top right
* bottom right
* bottom left
To switch between the variants press the space key.
Test Plan:
Rotated screen, used test app to verify the hotspot is
correct. Also scaled display, still correct
Reviewers: #kwin, #plasma
Subscribers: plasma-devel, kwin
Tags: #kwin
Differential Revision: https://phabricator.kde.org/D8668
