[webkit-dev] Extending Safari development

Hi, I was wondering how these guys extended Safari :- http://haoli.dnsalias.com/Saft/ With reference to adding in an extra preference tab and adding extra item to the context menu. I was investigating this and I think the path is using Text Input Managers, but couldn't see how you would go further from here or if this was the right path and then how to get the extra preference. Could you get access to the HTML source or selected src ? Thanks in advance for any pointers, Mark.