> On Nov 6, 2017, at 7:23 PM, Luis Sanjuán <luisj.sanj...@gmail.com> wrote:
>
> Hi, Matthias. I'm not sure about it either, but one situation where learners
> or users might miss it is when they want to share their work. If their code
> follows the design principles HtDP teaches, the world rendering will rely on
> a single point of control, say the width and/or height of the scene. But
> those are ultimately bound to the particular size of the computer screen on
> which they coded. On the other hand, if they were able to set the relative
> display size as point of control, well written code will behave well on many
> different screens, while not so good code would be penalized when shared.
> Just a point to speak in favor of the inclusion, but there might be more
> solid reasons to reject it.
It’s a convincing argument and I have pushed a new piece of functionality so
that the display-mode clause can ‘pick up’ the size of the monitor in a
functional manner. I still think this design is a bit clunky and I will
consider it experimental until the next release. For an example, see below —
Matthias
#lang htdp/isl+
(require 2htdp/universe)
(require 2htdp/image)
(require 2htdp/abstraction)
(define-struct world [size width height])
;; World = (make-world Number [Maybe Number] [Maybe Number])
;; World Number -> World
(define (update-size w s)
(make-world s (world-width w) (world-height w)))
;; {'fullscreen, 'normal} -> Number
(define (main x)
(big-bang (make-world 900 #false #false)
(to-draw (lambda (x)
(match x
[(world size #false #false)
(circle (+ 20 (world-size x)) 'solid 'red)]
[(world size width height)
(overlay
(rectangle (* .20 width) (* .20 (world-height x)) 'solid
'blue)
(circle (+ 20 (world-size x)) 'solid 'red))])))
(on-tick (lambda (x) (update-size x (- (world-size x) 20))))
(stop-when (lambda (w) (< (world-size w) 0)))
(display-mode x
;; optional function to pick up the extent of the world
(lambda (w width height) (make-world (world-size w) width
height)))
(close-on-stop #true)))
(main 'fullscreen)
(main 'normal)
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