What is the official way to get an icon coordinates from a NautilusFile ?

[Vincent Noel <vincent noel gmail com>]

Hey all,
I'm trying to come up with a patch for bug #147994 - visual
notification when you double-click on something on your desktop (e.g.
the "zooming boxes" you get when you click a launcher on your panel).
In order to do this, I need to find the screen coordinates of the
selected icon in the active window - I've tried to get them using
   position_string = nautilus_file_get_metadata (file,
NAUTILUS_METADATA_KEY_ICON_POSITION, "");
But it does not work (I get nonsense as a result).

What is the good, official way to do this ?
Thanks
Cheers
Vincent