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added the ability for the line function to draw in both positive and negative x and y directions

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svn: r2285
This commit is contained in:
Robby Findler 2006-02-19 16:04:45 +00:00
parent cd8239c29f
commit c7b023f76d
2 changed files with 21 additions and 12 deletions
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23
collects/htdp/image.ss
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@ -302,18 +302,17 @@ plt/collects/tests/mzscheme/image-test.ss
(check-coordinate 'line x "first")
(check-coordinate 'line y "second")
(check-image-color 'line color "third")
(check-sizes 'line (+ x 1) (+ y 1))
(let ([draw-proc
(make-color-wrapper
color 'transparent 'solid
(lambda (dc dx dy)
(send dc draw-line dx dy (+ dx x) (+ dy y))))]
[mask-proc
(make-color-wrapper
'black 'transparent 'solid
(lambda (dc dx dy)
(send dc draw-line dx dy (+ dx x) (+ dy y))))])
(make-simple-cache-image-snip (+ x 1) (+ y 1) 0 0 draw-proc mask-proc)))
(let ([w (+ (abs x) 1)]
[h (+ (abs y) 1)]
[px (abs (min x 0))]
[py (abs (min y 0))])
(check-sizes 'line w h)
(let* ([do-draw
(λ (dc dx dy)
(send dc draw-line (+ px dx) (+ py dy) (+ dx px x) (+ dy py y)))]
[draw-proc (make-color-wrapper color 'transparent 'solid do-draw)]
[mask-proc (make-color-wrapper 'black 'transparent 'solid do-draw)])
(make-simple-cache-image-snip w h px py draw-proc mask-proc))))
;; test what happens when the line moves out of the box.
(define (add-line raw-i pre-x1 pre-y1 pre-x2 pre-y2 color-in)

10
collects/tests/mzscheme/htdp-image.ss
View File

@ -486,6 +486,16 @@
(image=? (line 0 4 'red)
(color-list->image (list red red red red red) 1 5 0 0)))
(test #t
'line
(image=? (line 0 -4 'red)
(color-list->image (list red red red red red) 1 5 0 4)))
(test #t
'line
(image=? (line -4 0 'red)
(color-list->image (list red red red red red) 5 1 4 0)))
;; note: next two tests may be platform-specific... I'm not sure.
;; I developed them under macos x. -robby
(test #t