XULrunner

I came across XULrunner (GUI rendering backend used by Firefox and Thunderbird), and thought the concept is really interesting - building GUIs in XML. I read the Wikipedia page, and thought it was as clear as mud. I read the intro documentation and tutorial too on the Mozilla Developer Centre.

They all emphasize that XUL is only for the GUI, and has nothing to do with the application logic. The tutorial on MDC only covered how to create a simple UI, but my big question is, how do I interface the UI with code? In what language? The tutorial seems to suggest Javascript... but I find it hard to believe that Firefox is written in Javascript entirely.

Anyone has experience using XULrunner?

> but I find it hard to believe that Firefox is written in Javascript entirely.
A lot of it is.

I *think* that's what XPCOM is for -> http://www-128.ibm.com/developerwork.../co-xpcom.html

Firefox is written mostly in C++ and JavaScript.
XUL is used to describe user interfaces, CSS to style them, .properties and DTDs to localize them. JavaScript is used for behavior.
C++ is the foundation of all this. The XUL (and HTML) renderers are written in C++, the network stuff is written in C++, the JavaScript interpreter/JITter is written in C++. XPConnect (written in C++ and a bit of assembly) allows JavaScript and C++ code to interoperate.

Ah I see. I will look into it some more (aiming to make a cross-platform WLM client, mainly for practice).

Upon reading some protocol documents... forget about it =). I'll think of something else to make.