OK, I haven't looked into it, but I gather that the .xpi is just a zipped archive of javascript that operates on some sort of syntactic tree for the webpage, with XML describing where to insert action hooks in the general operation of Firefox.

But it must be horrendeously painful to code the scripts in vi, restart firefox to test, etc.. Any thing that gets a little bigger than 30 lines would need hot-swapping of script code, a full blown debugger with step-by-step, variable inspection, test-case replay, etc...

Have you got any of these that you would recommend ?

Pierre