You must provide a way for Motif applications programmers to instantiate your new widget. Chapter 2 explained how to make widgets accessible to C applications. We now explain how to make your new widgets accessible to a User Interface Language (UIL) application. If you have no need of making your widgets accessible to a UIL application, you can skip this chapter.
UIL is a programming language designed for rapid prototyping of Motif interfaces. A UIL program consists mainly of definitions of the application's widget hierarchy. That is, a UIL program tells the Motif Resource Manager (MRM) which widgets to instantiate. (For details on writing UIL applications, see the Motif Programmer's Reference.)
Motif vendors typically provide a UIL compiler that "understands" only those widgets in the Motif toolkit. Fortunately, UIL is an extensible language. This means that, when you write a new widget, you can expand the UIL language to make the compiler understand your new widget.