[pyatspi2] How to get current element (tab or application) ?

Hi everyone! I've developed software to make focus tracking in Compiz 
environment but I doesn't find how to get the current tab on terminal or 
Firefox. I have found some method to get the current application 
(event.host_application) but nothing to deal with the tab or a specific 
window of an application. If you can give me more information about that 
and how Orca does I would be grateful.
The goal of that need is to block focus tracking with the current element.

Best regards.

-- 
Alex ARNAUD