How to determine *actual* visible region of a window?

["Gaurav Jain" <gaurav anywhere gmail com>]

Hi,

For the purpose of my application, I need to programmatically
determine the actual 'exposed' region of a gdk window.  The exposed
region should not include any obscured regions of the window.  For
example, if there's some external window in front of my application's
window, then the exposed region should not include the area obscured
by that external window, but should include all other area that's
visible.

I tried using the API gdk_drawable_get_visible_region() but this
doesn't exclude the obscured regions, so it's not of my use.

Does somebody know of any suitable API that I can use to achieve what
I want?  Or is there a method that somebody could suggest that I could
use to calculate this region?

Any help would be really appreciated.

Thanks in advance.
Gaurav