Enter/Return in CAPI:MULTI-LINE-TEXT-INPUT-PANE with :CALLBACK

If I give a :callback to a capi:multi-line-text-input pane, is it
expected that the callback will be called when the user presses
Enter/Return?  E.g., in the following code:

(capi:contain
 (make-instance 'capi:multi-line-text-input-pane
                :callback #'(lambda (&rest args)
                              (break "~A" args))))

On Windows, when I press Enter/Return I get a break dialog, but on OS
X I don't.  In both cases I'm running LW6.  Is there supposed to be a
consistent behavior?

[I realize, of course, that having a callback that is typically
invoked by pressing Enter/Return in a pane where Enter/Return should
insert an Enter/Return is already a strange situation.  It happened
when I switched from using a capi:text-input-pane to a
capi:multi-line-text-input-pane.  I've removed the callback, since I
want to be able to put in Newlines.]

//JT

-- 
Joshua Taylor, http://www.cs.rpi.edu/~tayloj/