Dubious Window visible handling

Run the attached QML file with qmlscene. The root Window is only necessary, because qmlscene will always show the root Window independent of the visible property. The root Window can be ignored, only parentwin and childwin are of interest.

If the child is visible, but not the parent, both windows will NOT be shown.

1. If the parent is set to visible, as well, both parent and child will be shown.
2. If parent is set back to invisible again, child keeps on showing
3. In this state, even if the child is explicitly set to invisible, it keeps on showing

This is inconsistent, either the hierarchy should not be considered at all (and hence a child window should be shown independent of the parent) or an invisible parent should always make the child invisible, as well.

The results are independent of the modality or visibility Window properties.