[plt-scheme] grid% - first go

On Sunday, December 28, 2003, at 04:51 PM, Guenther Schmidt wrote:

>  For list-related administrative tasks:
>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>
> Hi,
>
> below is a first draft for the grid% element.
>
> Any help for improving highly welcome! :-)
>
>
> (define grid%
>  (class pane%
>    (init (columns-init 1))
>    (field (columns columns-init))
>    (inherit get-children)
>    (define/override (place-children children width height)
>      (local
>          ((define child-width (ceiling (/ width columns)))
>           (define child-height (ceiling (/ height (ceiling (/ (length 
> children) columns)))))
>           (define (place a-list n)
>             (cond
>               ((empty? a-list) '())
>               (else                (cons                 (let* ((child 
> (car a-list))
>                        (width (first child))
>                        (height (second child))
>                        (x (* child-width (modulo n columns)))
>                        (y (* child-height (quotient n columns))))
>                   (list                    (+ x (round (/ (- 
> child-width width) 2)))                    (+ y (round (/ (- 
> child-height height) 2)))
>                    width height))
>                 (place (cdr a-list) (+ n 1)))))))
>        (place children 0)))
>    (define/override (container-size a-list)
>      (let ((max-h 0) (max-w 0))
>        (for-each
>         (lambda (x)
>           (if (> (first x) max-h) (set! max-h (first x)))
>           (if (> (second x) max-w) (set! max-w (second x))))
>         a-list)

FWIW, this can be written as
   (let ([max-h (apply max (map first a-list))]
           [max-w (apply max (map second a-list)])
     (values ... ...))

>        (values (* max-w columns) (* max-w (ceiling (/ (length a-list) 
> columns))))))
>    (super-new)))

In general, I suspect that you need more information about/from
the children. To see, create a frame with a gui-grid in it and do
something like this:

  (for-each (lambda (i) (new text-field (parent the-grid) (label i) 
(callback void)))
                   (build-list 22 number->string))

-- Matthias