Mozilla's Simple And Flexible XUL

To go beyond simple HTML, historically the only options have been to use Java technology or plug-ins. Now, you have a new way -- write and display applications natively in XML. The Mozilla platform provides such a mechanism. In this article, Nigel McFarlane introduces XUL (the XML User-interface Language). XUL is set of GUI widgets with extensive cross-platform support that are designed for building GUI elements for applications that have traditional, non-HTML GUIs.

The Mozilla platform is a bundle of freely available open source technology that underlies many user-oriented software applications. Some of these applications are desktops and some are development tools, but the most famous ones are Web browsers, including Mozilla, AOL for the Macintosh, Galeon on Linux, and Netscape.

Although these browsers are mostly used to display HTML, the platform beneath them offers much more. In particular, the Mozilla platform's extensive support for XML provides an alternative to Java technology for the creation of applets and applications. In this article, I'll demonstrate how to create such applets using XML tags instead of Java classes. It is a refreshingly simple, yet powerful approach.

Although the Mozilla platform has its share of object classes (more than a thousand at last count), it is best known for its deep use of XML. For some flavors of XML (like XHTML), the platform provides full rendering support while for other flavors (like RDF), it provides support for data processing only. Rendering support is required if an XML document is to have a visual representation. The platform has rendering support for HTML/XHTML, MathML, optionally SVG, and also its own XUL, covered in this article.