"Which function to call to handle a drop of that type.
If the type for the drop is not present, or the function is nil,
the drop is rejected. The function takes three arguments, WINDOW, ACTION
-and DATA. WINDOW is where the drop occured, ACTION is the action for
+and DATA. WINDOW is where the drop occurred, ACTION is the action for
this drop (copy, move, link, private or ask) as determined by a previous
call to `x-dnd-test-function'. DATA is the drop data.
The function shall return the action used (copy, move, link or private) if drop