Whats the difference between the parent widget and the owner window?
There are two kinds of relationships, parent->child, and owner->owned. For all except the root widget, a parent->child relationship exists. When a parent is destroyed, the parent it its turn destroys the children. In the case of owner->owned, the relationship cuts across the widget tree. In most cases, the programmer needs to make explicit arrangements for owners to delete the objects that they own. For example, a toolbar shell and a main window are on equal levels in the widget tree (both directly under root), but there is an owned/owner relationship also. So the main window must explicitly delete the toolbar shell. It sounds complicated, but the problem really only occurs for top-level windows, i.e. dialogs owned by main window, and so on. Even in pretty large applications, only a handful of such objects typically exist. Think of those owned widgets as icons and fonts, which also must be explicitly destroyed.
