> I expect that if you call call-next-method at the top of your EVENT
  > method rather than at the end then the OS will establish the new value

  I have tried to do that. But it doesn't work.
  Any idea?

An oversight of mine.  I forgot that the OS implements the item-list
widget to change its value on the mouse-button-up rather than the
mouse-button-down.  So you would need to check the value after the
default button-up handler rather than after the button-down as I had
suggested.

After calling subclass-widget on a my-list widget, the following code
will print its current value after any button-up.

---------------------------------------------------------------------------
(defclass my-list (single-item-list)())

(defclass my-list-window (pc::single-item-list-pane)())

(defmethod widget-device ((dialog-item my-list) dialog)
   'my-list-window)

(defmethod event ((window my-list-window)(msg (eql mouse-left-up))
                  buttons data time)
   (call-next-method) ;; select the new value if there is one
   (let* ((widget (window-dialog-item window)))
      (when widget
         (print (dialog-item-value widget))))) ;; print current value
---------------------------------------------------------------------------

Ken Cheetham                          <franz.com at cheetham>
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