Geometry problem

[Kazunobu Kuriyama]

Hi, all.

I have a question about the GNUstep's geometry.
The question is as follows:


       X
   |-------|    Object A
-- +---------------------------------------------------
 | |(0,0)
Y | |
 | |            Object B
-- |       +----------------------------------------
   |       |(X,Y)
   |       |
   |       |
   |       |


Here, you have two GUI objects Object A and Object B.  Object A
is the main window of an GNUstep application, and Object B is an
instance of either the NSView class or its subclass.  The coordinates
system is taken as shown above.  Ignore the border width for now
because it's a matter of arithmetic.  Then, you need to know the
coordinates values (X, Y) to implement a method declared in the
interface of Object B.  Write a piece of code to calculate X and Y.
The code should be independent of the underlying window system.

If Object A is a parent or ancestor of Object B (in a sense of
window hierarchy), the answer may be easy.  I have no idea,
however, if Object A is an instance of NSApplication.

Could you help me so that I won't devise GSTranslateCoordinates,
a ridiculous wrapper of XTranslateCoordinates() that ruins
the GNUstep's OO structure?

Thank you.