This makes the code clearer and decouples it from the
GLWidget.
As a drive-by, add a global shortcut to close.
Change-Id: I3469d29bc367acc17c5f8acf9d46219259b8315b
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
(cherry picked from commit f172b964f6d9fc8cadeb7b5efeb3f59c0f8f16f6)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
