Creating Screenshot?

Hi All,

I'd like my code to create a screenshot of an interface or
(it's topmost) layout. This can be done by gp:make-image-from-port.
Unfortunately gp:make-image-from-port can't be applied 
to capi:interface or capi:layout.

Is it possible to obtain a reference to an interface's or 
layout's graphics port?


Thanks

Andreas