We've started doing a fair bit of work with XUL, the Mozilla XML-based User Interface Language (there's a hint in there about a big upcoming announcement for the In-Between-Line-Readers among you). It's a really interesting environment to work in and really easy to learn since the entire Firefox browser is built in XUL and you can take it apart to study by example.

Now that we've clocked in a couple of days worth, we thought we'd share a few quick tips for those aspiring extension developers:

1. You can use the DOM Inspector to look inside any element of chrome, the term Mozilla uses to refer to the browser's interface. Just open the inspector and use the URL to your chrome as the address - try chrome://browser/content/browser.xul to pick apart the browser's interface.
2. You can use Venkman, the Mozilla JavaScript debugger, to step through you component's code too. If you're running Firefox (as opposed to Mozilla), you'll need to grab the Venkman Extension first, then launch it from the Tools menu. You won't see any chrome files at first, but they'll all show up if you turn off Exclude Browser Files in the Debug menu. Make sure that the component you want to debug is actually open or the files won't be listed (i.e.: if you're trying to debug a window, open the window once to get the files listed, set a breakpoint, close and reopen).
3. This one's a little more obscure but might save you a whole bunch of hair pulling - you can load a stringbundle from inside an overlay on a window, and the bundle will be visible in the DOM Inspector, but you won't be able to access it using JavaScript. Seems to be a bug, though we couldn't find anything listed in BugZilla. You can insert the stringbundle in the JavaScript first and then insert it into the window, or you can just put the stringbundle into the window instead. If anyone has a better workaround, we'd love to hear it.
   

That's it for the first installment - stay tuned as we learn more :)