This online book is a reference for the XML-based User Interface Language (XUL). Mozilla has configurable, downloadable chrome, meaning that the arrangement and even presence or absence of controls in the main window is not hardwired into the application, but loaded from a separate UI description.
In fact, most of Mozilla’s windows (and dialogs) will be described using this mechanism. XUL (pronounced “zool,” as if that spelling helped any, and short for “XML User Interface Language”) is our name for the language in which these UI descriptions are built.
Window chrome is displayed and managed by the same layout engine that manages HTML content in the browser. UI descriptions, then, look a great deal like HTML 4. XUL is an application of XML. In fact, it is just XML with specific meaning defined for a few element types, and into which HTML can be scattered.
- Window structure
- Menus and popups
- Tabs and grouping
- Text and images
- Helper elements
Link: Read online.