Volume 6A: Motif Programming Manual

The Gadget class hierarchy

The Gadget class is a superclass for all of the Motif gadgets. Like Primitive, this class is a metaclass that is never

instantiated. However, gadgets are not widgets. The Gadget class is subclassed from the RectObj class, not from the

Core widget class. the figure shows the class hierarchy for gadgets.

4.3 Application Layout

While the controls are the most obvious part of a graphical user interface, these elements alone do not make an

effective interface. A random arrangement of buttons or a collection of nested menus can make an application as

obscure and as difficult to use as one with a command−line interface. The arrangement of the controls in an

application makes all the difference.

To help you lay out your application, Motif provides you with a set of manager widgets. You can think of manager

widgets as boxes in which you can put things. These boxes, however, can grow or shrink as necessary to provide the

best fit possible for the items that they contain. You can place boxes inside of other boxes, whether or not they contain

other items. By using different size boxes, you can organize things in many different ways.

Manager widgets are so named because they manage the size and position of other widgets. The relationship between

a manager widget and the widgets that it manages is commonly referred to as the parent−child model. The manager

acts as the parent, and ...