nsIFrame and nsIPresContext are internal in firefox3, how to achieve the same functionality of these 2 interfaces

Hi,

I used nsiframe and nsIPresContext interfaces in my application to get
screen related information in firefox 2 but I see in firefox3, these
two interface are internal, so how can I achieve the same
functionality to get screen related information in firefox3?

Are there any equivalent public interfaces for these?
For example I used GetRect(),GetContent(), GetFrameState(&aResult),
GetViewExternal() APIs. Is there any way I can get the functionality
of these APIs through some other interfaces or API()s.

Please let me know if you have any pointers, it would be of great help
to me.

Thanks
Srinivas