Thanks,
Thats exactly what I needed.
Stephen
PS Here is another version
#lang racket/gui
;;;
;;; WORLD
;;;
(define-struct world (lines))
(define the-world
(make-world '()))
; ((0 . 0) (0 . 300) (250 . 250)) ((150 . 176) (10 . 4) (280 . 10))
;;;
;;; USER LAND
;;;
(define (on-mouse-event world event)
(let ((x (send event get-x))
(y (send event get-y)))
(cond
[(and (send event get-left-down) (send event button-changed?))
(make-world (cons (cons (cons x y) '()) (world-lines world)))]
[(and (send event get-left-down) (send event moving?) (not (send
event button-changed?)))
(make-world (cons (cons (cons x y) (car (world-lines world))) (cdr
(world-lines world))))]
[else world])))
(define (on-paint world dc)
(for-each (λ (lines) (send dc draw-lines lines))
(world-lines world)))
;;;
;;; SYSTEM
;;;
(define user:on-paint on-paint)
(define diagramframe (new frame% [label "paint"]
[width 300] [height 300]
[x 1000][y 300]))
(define paintcanvas%
(class canvas%
(inherit get-dc refresh)
(super-new)
(send (get-dc) set-pen "red" 10 'solid )
(define/override (on-paint)
(send (get-dc) suspend-flush)
(user:on-paint the-world (get-dc))
(send (get-dc) resume-flush))
(define/override (on-event mouse-event)
(let* ([old-world the-world]
[new-world (on-mouse-event the-world mouse-event)])
(if (eq? old-world new-world)
(super on-event mouse-event)
(begin
(set! the-world new-world)
(refresh)))))))
(define paintcanvas (new paintcanvas% [parent diagramframe]))
(send diagramframe show #t)
On Mon, Apr 9, 2012 at 12:12 PM, Jens Axel Søgaard <jensa...@soegaard.net>wrote:
> Hi Stephen,
>
> Here is how I would do it.
>
> /Jens Axel
>
> #lang racket/gui
>
> ;;;
> ;;; WORLD
> ;;;
>
> (define-struct world (lines))
> (define the-world (make-world '((0 . 0) (0 . 300) (250 . 250) (150 .
> 176) (10 . 4) (280 . 10))))
>
> ;;;
> ;;; USER LAND
> ;;;
>
> (define (on-mouse-event world event)
> (if (and (send event get-left-down)
> (send event moving?)
> #; (send event button-changed?))
> (let ((x (send event get-x))
> (y (send event get-y)))
> (make-world (cons (cons x y) (world-lines world))))
> world))
>
> (define (on-paint world dc)
> (send dc draw-lines
> (map pair->point (world-lines world))))
>
> (define (pair->point p)
> (make-object point% (car p) (cdr p)))
>
>
> ;;;
> ;;; SYSTEM
> ;;;
>
> (define user:on-paint on-paint)
>
> (define diagramframe (new frame% [label "paint"] [width 300] [height
> 300] [x 1000][y 300]))
>
> (define paintcanvas%
> (class canvas%
> (inherit get-dc refresh)
> (super-new)
>
> (define/override (on-paint)
> (send (get-dc) suspend-flush)
> (user:on-paint the-world (get-dc))
> (send (get-dc) resume-flush))
>
> (define/override (on-event mouse-event)
> (let* ([old-world the-world]
> [new-world (on-mouse-event the-world mouse-event)])
> (if (eq? old-world new-world)
> (super on-event mouse-event)
> (begin
> (set! the-world new-world)
> (refresh)))))))
>
> (define paintcanvas (new paintcanvas% [parent diagramframe]))
> (send diagramframe show #t)
>
>
>
> 2012/4/9 Stephen De Gabrielle <stephen.degabrie...@acm.org>:
> > Hi,
> >
> > I thought I'd try a simple GUI app using the world/universe mutation-free
> > approach, but trying to implement the 'world/universe' program design
> > myself.
> >
> > I've got my little sketch below, but I quickly came to conclusion that
> while
> > I could use the teachpack, I don't know how to achieve the teachpack
> > functionality myself.
> >
> > I'm guessing I should use continuations, but that doesn't seem to be the
> > approach in the universe.rkt source.
> >
> > I could always just stuff the program into the canvas class, (as earlier
> > games like slidey and same seem to do), but I really want to get a handle
> > on how to implement the 'world/universe' style of program control.
> >
> > Any suggestons would be appreciated.
> >
> > Kind regards,
> >
> > Stephen
> >
> >
> > ;;;;----
> > #lang racket/gui
> >
> > ; simple drawing program
> > ; mousedown starts recording a list of points
> > ; mousechanged starts recording a new list
> > ; paint callback paints the list of lists as lines.
> >
> > (define diagramframe (new frame% [label "paint"] [width 300] [height
> 300] [x
> > 1000][y 300]))
> >
> > ;(define lines '(((0 . 0) (0 . 300) (250 . 250) (150 . 176))))
> > (define lines '(((0 . 0) (0 . 300) (250 . 250) (150 . 176))
> > ((10 . 4) (280 . 10))))
> >
> > (define paintcanvas%
> > (class canvas%
> > (init-field mouse-event-callback)
> > (super-new)
> > (define dc (send this get-dc))
> > (define/override (on-event mouse-event)
> > (mouse-event-callback mouse-event))))
> >
> > (define (paint-cb c dc)
> > (for-each (λ (line) (send dc draw-lines line)) lines))
> >
> > (define (me-cb mouse-event)
> > (let ((x (send mouse-event get-x))
> > (y (send mouse-event get-y)))
> > (when (and (send mouse-event get-left-down)
> > (send mouse-event moving?))
> > (if (send mouse-event button-changed?)
> > ; if true append as new list
> > '()
> > ; if false append existing list
> > '())))
> > )
> >
> > (define Paintcanvas (new paintcanvas%
> > [parent diagramframe]
> > [paint-callback paint-cb]
> > [mouse-event-callback me-cb]))
> >
> > (define (main world)
> > (when world (main (??? world)))
> > (send diagramframe show #t))
> >
> > (main lines)
> >
> > (send diagramframe show #t)
> >
> > ;;-----
> >
> > ____________________
> > Racket Users list:
> > http://lists.racket-lang.org/users
> >
>
> --
> Jens Axel Søgaard
>
--
--
Stephen De Gabrielle
stephen.degabrie...@acm.org
Telephone +44 (0)20 85670911
Mobile +44 (0)79 85189045
http://www.degabrielle.name/stephen
----
Professor: Oh God! I clicked without reading!
Cubert: And I slightly modified something I own!
Professor: We're monsters!
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