Re: catch-cancel

[korcuska@ils.nwu.edu (Michael Korcuska)]

In article <korcuska-2805950935540001@korcuska.ils.nwu.edu>,
korcuska@ils.nwu.edu (Michael Korcuska) wrote:

> We ran into a strange problem the other day with catch-cancel and
> throw-cancel.  Inside a catch-cancel we create a window with a button
> which, when clicked, calls throw-cancel.  Unfortunately the throw wasn't
> being caught by the catch we set up.
> 
> After puzzling over this for a bit, we ditched (catch-cancel...) and used
> (catch :my-cancel ...).  Now it works fine.
> 
> Ok.  So catch-cancel must be doing something strange, right? 

Just following up to my own message.  Here's some code that illustrates
the problem.  Just change *tag* to something other than :cancel and the
code works.  Any comments?

(defparameter *tag* :cancel)

(let* ((btn (make-instance 'button-dialog-item
              :view-size #@(60 20)
              :view-position #@(20 40)
              :dialog-item-text "Cancel"
              :dialog-item-action #'(lambda (item)
                                      (declare (ignore item))
                                      (throw *tag* "Cancelled")))
            )
       (wind (make-instance 'window
               :window-type :single-edge-box
               :view-position :centered
               :view-size #@(100 100)
               :window-show nil
               :view-subviews (list btn))))
  (princ
   (catch *tag*
     (window-show wind)
     (princ "Looping until cancel button clicked")
     (loop for i from 1 to 500
           do (princ ".")
           finally (return "finished"))))
  (window-close wind)
  )

Michael Korcuska
Institute for the Learning Sciences
Northwestern University
korcuska@ils.nwu.edu