[Mono-winforms-list] How to know the rect associated with a handle ?

[Dasnois Benjamin]

Hello,
I'm working on a CommonDialog implementation but I need to know the
rectangle associated with a handle (IntPtr)
I saw two functions to do this: the first one is  Win32GetClientRect
in XplatUIWin32 and the second one is GetWindowPos in XplatUI
So I suppose one is for linux (X server) and the other one is for
windows but I would like to know how I can know which one to use, in
other words: how can I know if I'm under windows or linux ? Or maybe
there's a simpler solution ?

Thanks.

-- 
DASNOIS Benjamin