[racket] big-bang is slow to render on screen?

Yes, the `main` version runs normally fast, while the `main2` version is
slow.


On Tue, Apr 22, 2014 at 4:15 PM, Matthias Felleisen <matthias at ccs.neu.edu>wrote:

>
> The attached file is from a vignette that I have been working on
> ("Programming with Class"). It simulates 'big-bang' without a lot of the
> student protections and the machinery needed to make it compatible with the
> stepper etc. It also cuts out some of the software engineering playing I
> did (but which turned out to be useful over the years).
>
> The fragment below runs your program (as far as I can tell) like the
> original. Could you please measure this new version of your 'funny' machine?
>
> Thanks -- Matthias
>
> #lang racket
>
> ;;; Run this file with `racket test-big-bang.rkt`
> ;;; then type quickly "asdf" to trigger several successive to-draw events.
> ;;; Drawing the scene is fast, but rendering it on-screen is very slow?
>
> (require 2htdp/image
>          2htdp/planetcute
>          "bb.rkt")
>
> (define elt-width (image-width grass-block))
> (define elt-height (image-height grass-block))
> (define elt-height/2 (/ elt-height 2))
>
> (define view-width 800)
> (define view-height 400)
> (define window-width view-width)
> (define window-height (+ view-height elt-height))
>
> (define grid-size 10)
>
> (define (stack-rows . col-picts)
>   (for/fold ([img empty-image])
>     ([cp col-picts])
>     (underlay/align/offset
>      "center" "bottom"
>      img 0 elt-height/2 cp)))
>
> (define (client-draw-all)
>   (apply stack-rows
>          (for/list ([i grid-size])
>            (apply beside/align "bottom"
>                   (for/list ([j grid-size])
>                     grass-block)))))
>
> (define t0 (current-milliseconds))
> (define (print-time str)
>   (printf "~a at ~a\n" str (- (current-milliseconds) t0)))
>
> ;; uncomment if you want to compare old and new
> #;
> (define (main2)
>   (local-require 2htdp/universe)
>   (big-bang
>    '()
>    (to-draw (λ(w)
>               (print-time "to-draw")
>               (display "to-draw: ")
>               (time (client-draw-all)))
>             window-width window-height)
>    (on-key (λ(w k)(print-time (format "on-key ~a" k))))))
>
> (define (main)
>     (send (new world%
>                [state0 10]
>                ;; -------------------------------------------------------
>                ;; from Laurent's code
>                [to-draw
>                 (λ(w)
>                   (print-time "to-draw")
>                   (display "to-draw: ")
>                   (time (client-draw-all)))]
>                [on-key (λ(w k)(print-time (format "on-key ~a" k)))]
>                ;; -------------------------------------------------------
>                [width window-width]
>                [height window-height]
>                [on-mouse #f])
>           start))
>
>
>
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