Is it possible to define pull-down menus as a type of window? Consider a menu's characteristics. A menu's position is restricted to the top of the screen. Its size is determined by the number of items it contains and the width of the longest item. A menu appears only when an entry on the menu bar is activated, and disappears when the command is executed. This type of behavior doesn't fit easily into the current windowing hierarchy. Pull-down menus thus require a separate hierarchy, which is beyond the scope of this chapter.
Remember that the classes developed here are simply a small example for demonstrating the process of object-oriented design. To write a professional windowing package, you would need to design a much larger class hierarchy. Also, note that the design presented in this chapter is only one of several possible designs for the windowing package described here.