[plt-scheme] MrEd question: display image-snip% in a window; deinitialization

From: Chongkai Zhu (czhu at cs.utah.edu)
Date: Thu Oct 5 23:25:13 EDT 2006

Thanks for the quick reply.

By "Override the `on-close' method of the frame", do you mean:

(define my-frame%
  (class frame%
    (override on-close)
    (define (on-close)
      ;my deinitialization code here
      (super on-close))))

? If yes, I get the following error message:

class*: superclass method for override, overment, or rename-super is not overrideable: on-close for class: my-frame%


----- Original Message ----- 
From: "Matthew Flatt" <mflatt at cs.utah.edu>
To: "Chongkai Zhu" <czhu at cs.utah.edu>
Cc: "pltscheme" <plt-scheme at list.cs.brown.edu>
Sent: Friday, October 06, 2006 10:57 AM
Subject: Re: [plt-scheme] MrEd question: display image-snip% in a window;deinitialization 

>> The second question is, when the user closes the main (and the only) frame by 
>> click the "X" on the title bar, how could I ask the program to do some extra 
>> deinitialization work? I tried the "application-quit-handler", but failed to 
>> figour out the "initial eventspace" thing. And my GUI doesn't use a menu.
> Override the `on-close' method of the frame. Or override `can-close?'
> if your extra work sometimes needs to cancel the close.
> Matthew

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