[plt-scheme] Trouble with GUI

Oops, nevermind.  All that lets you omit is the super-new at the end.

Daniel

On Sun, 17 Oct 2004 03:27:23 +0900, Daniel Silva <daniel.silva at gmail.com> wrote:
> On Fri, 15 Oct 2004 17:46:50 -0500, Arctic Fidelity <af at aaronhsu.com> wrote:
> 
> 
> >   For list-related administrative tasks:
> >   http://list.cs.brown.edu/mailman/listinfo/plt-scheme
> >
> > On 15 Oct 2004 at 8:49, Matthew Flatt wrote:
> >
> > > At Fri, 15 Oct 2004 08:46:13 -0500, "Arctic Fidelity" wrote:
> > > > I think I have the ouput buffer okay, but what's getting me is
> > > > processing the keys. I understand how I would process the buttons,
> > > > but how would I capture the key events from anywhere but the
> > > > output field, and then according to what key was pressed, update
> > > > my disabled text-field appropriately.
> > > >
> > > > The plan I had was to create a procedure for the main window
> > > > which would take the input from the keys, and process it from there.
> > > > However, I cannot seem to figure out how to use "on-subwindow-
> > > > char" or how to change what happens with that, as the frame% has
> > > > nowhere that I can specify a callback procedure.
> > >
> > > I think you're on the right track with `on-subwindow-char'. You need to
> > > derive a subclass of frame% that overrides `on-subwindow-char'.
> >
> > I was afraid you were going to say that, I was actually hoping there
> > was a way I could do that without having to override the defaults,
> > but I suppose that's just what happens. ;-)
> 
> Try using a Java-style new operator too :)
> Examples in the test function:
> 
> (module overriding-new mzscheme
> 
>   (provide overriding-new)
> 
>   (require (lib "class.ss"))
> 
>   (define-syntax (overriding-new stx)
>     (syntax-case stx (local inherit)
>       [(_ super%
>           (local (inherit-field super-field ...) (define (fn args ...)
> bodies ...) ...)
>           (field value) ...)
>        #`(new (class super%
>                 (inherit-field super-field ...)
>                 (begin
>                   (define/override (fn args ...)
>                     bodies ...) ...)
>                 (super-new))
>               (field value)
>               ...)]
>       [(_ super%
>           (local (define (fn args ...) bodies ...) ...)
>           (field value) ...)
>        #`(_ super% (local (inherit-field) (define (fn args ...) bodies
> ...) ...) (field value) ...)]
>       ))
> 
>   (define (test)
>     (define C%
>       (class object%
>         (init-field x)
>         (define/public (add y)
>           (+ x y))
>         (define/public (sub y)
>           (- x y))
>         (super-new)))
> 
>     (define c (new C% (x 1)))
>     ;; oops, turn addition into multiplication, sub. into mult.
>     (define d (overriding-new C%
>                               (local
>                                   (inherit-field x)
>                                   (define (add y)
>                                     (* x y))
>                                   (define (sub y)
>                                     (/ x y)))
>                               (x 1)))
> 
>     (define (check expected actual)
>       (unless (= expected actual)
>         (error 'check (format "expected ~a, got ~a"
>                               expected actual))))
> 
>     (check 3 (send c add 2))
>     (check -1 (send c sub 2))
>     (check 2 (send d add 2))
>     (check 1/2 (send d sub 2)))
> 
>   )
>