Making the date picker popup a child of the combobox.
Otherwise, problems occure when embedding the KDateEdit in an itemview (as in the todo view of KOrganizer).

This is because QStyledItemDelegate monitors focus changes and only ignores those which are between different child widgets of the editor.

As the popup was no child of the editor, QStyledItemDelegate thought that the focus moved away from the editor, and closed it.

So no interaction with the popup was possible.

That's fixed now.

There should be no impact on all other use cases.