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O'Reilly Network: XUL Tools and What They Mean

May 21, 2000, 05:09 (0 Talkback[s])
(Other stories by Ian Oeschger)

"It doesn't make any difference how cool your toolbox is if you don't know the names and functions of its contents. XUL (pronounced "zule") is a rich environment for cross-platform development within the Mozilla project. In this article we're going to learn a little bit about the various XUL tools and discuss their use in the simplest terms possible."

"Mozilla is obviously a lot more than simply an interface. It's cross-platform, and standards-based, and yet in some way, the event handlers written once in JavaScript and living in the XUL interface are getting very serious things done down in the application core. Things like socket interfaces, editing, mail, and security. The technologies that make this possible are perhaps the least understood of the phalanx of innovations that is Mozilla. In addition to the small matter of programming these serious things in C++ and compiling them platform for platform, the architects and developers of Mozilla use three "XP" technologies to link the core with the interface."

"XPCOM is not a programming language but an approach to programming (in C++, say) that provides for a truly cross-platform Component Object Model. Based on COM, XPCOM insists that chunks of code provide language- and platform-neutral interfaces that other objects can use to access its services. XPCOM enforces rules for design and compilation that make it possible to use the services of an object without knowing anything about implementation. XPIDL, the Cross-Platform Interface Definition Language, is a language in which these interfaces insisted upon by XPCOM can be described. When XPIDL is used to describe the XPCOM interfaces, it makes those interfaces available in special header files. Finally, XPConnect is the technology that connects these XPCOM/XPIDL interfaces to JavaScript, the scripting language XUL uses."

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