Programming Firefox

Chapter 12. XUL Widget Reference

Complex open source software such as the Firefox framework can be an intimidating read when you’re trying to make sense of its nuances and structure. But a basic understanding of how XUL widgets are defined and implemented is essential if developers are to take full advantage of the rich features of such a framework.

This chapter provides a basic overview of how to define and implement XUL widgets, including a discussion of:

• The organization of file families that define XUL widgets

• How and where core classes are defined

• How to read the XML Bindings Language (XBL) bindings to determine a widget’s properties and methods

• A reference list of the XUL widgets that comprise interface elements

Browser Package Files

In this book we have discussed a large number of XUL elements—XML tags that the Firefox framework reads as instructions for painting an interface and providing services to an application. This section discusses a subset of XUL elements: the widgets that provide the appearance and interaction tools for an application’s interface.

All XUL widgets have attributes whose values are obtained and modified by the get/setAttribute("someAttributeName") method, properties whose values are obtained by a dot (.) reference such as someElement.someProperty, and methods.

Methods that access attributes by way of getAttribute( ) return the string assigned to the attribute in the XUL source file, and property references return the value of an expression (e.g., Boolean ...