a window which may be at the pointer position, but should be ignored, since it is put up by the drag source as an icon
the screen where the destination window is sought
the x position of the pointer in root coordinates
the y position of the pointer in root coordinates
location to store the destination window in
location to store the DND protocol in
2.2
Finds the destination window and DND protocol to use at the given pointer position.
This function is called by the drag source to obtain the dest_window and protocol parameters for gdk_drag_motion().