Volume 4 is a complete guide to programming with the X Toolkit Intrinsics, the library of C language routines that facilitates the design of user interfaces with reusable components called widgets. It provides concepts and examples that show how to use the various X Toolkit routines. The first few chapters are devoted to using widgets; the remainder of the book covers the more complex task of writing new widgets. Volume 4 includes: Introduction to the X Window System. Building applications with widgets. Constructing a bitmap editor with widgets. An overview of each widget in the widget set. Basic widget methods./li> Events, translations, and accelerators. Event handlers, timeouts, and work procedures. Resource management and type conversion. Selections and window manager interaction. Geometry management. Menus, gadgets, and cascaded pop-ups. Miscellaneous techniques. Comparison of Athena, OSF/Motif, and AT&T OPEN LOOK widgets. This book is designed to be used with Volume 5, X Toolkit Intrinsics Reference Manual , which provides reference pages for each of the Xt functions, the widget classes defined by Xt, and the Athena widget set.