If a widget's geometry is restored to a screen, which is smaller than
the one it was saved from,
- the widget could appear (partly) off screen
- the widget's title bar and resize handles could be inaccessible
This patch refactors and documents checkRestoredGeometry.
In a first step, the restored geometry's size is checked against
a given screen size. It is corrected if necessary.
In a second step, the restored geometry is moved inside the screen,
if necessary.
It makes the function a static member of QWidgetPrivate in order to
expose it for auto testing and adds a respective test function to
tst_QWidget.
Fixes: QTBUG-77385
Fixes: QTBUG-4397
Task-number: QTBUG-69104
Pick-to: 6.5 6.4
Change-Id: I7172e27bfef86d82cd51de70b40de42e8895bae6
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>