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fix rotation problems and sense of `transform'-like operations

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so that they conceptually apply after the current
 transformation, instead of before the current transformation;
 more general rotation problems were related to aligned drawing
 and the calculation of the effective scale for alignment
This commit is contained in:
Matthew Flatt 2011-05-10 08:55:24 -06:00
parent dc7e8ef379
commit 0011f5957d
2 changed files with 8 additions and 4 deletions
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10
collects/racket/draw/private/dc.rkt
View File

@ -379,8 +379,11 @@
(cairo_matrix_translate mx origin-x origin-y)
(cairo_matrix_scale mx scale-x scale-y)
(cairo_matrix_rotate mx (- rotation))
(set! effective-scale-x (cairo_matrix_t-xx mx))
(set! effective-scale-y (cairo_matrix_t-yy mx))
(let ([ssq (lambda (a b) (sqrt (+ (* a a) (* b b))))])
(set! effective-scale-x (ssq (cairo_matrix_t-xx mx)
(cairo_matrix_t-xy mx)))
(set! effective-scale-y (ssq (cairo_matrix_t-yy mx)
(cairo_matrix_t-yx mx))))
(set! effective-origin-x (cairo_matrix_t-x0 mx))
(set! effective-origin-y (cairo_matrix_t-y0 mx))
(let ([v (vector (cairo_matrix_t-xx mx)
@ -448,13 +451,14 @@
(cairo_matrix_translate mx origin-x origin-y)
(cairo_matrix_scale mx scale-x scale-y)
(cairo_matrix_rotate mx (- rotation))
(cairo_matrix_multiply mx mx mx2)
(cairo_matrix_multiply mx mx2 mx)
(set! origin-x 0.0)
(set! origin-y 0.0)
(set! scale-x 1.0)
(set! scale-y 1.0)
(set! rotation 0.0)
(set! matrix mx)
(reset-effective!)
(reset-matrix)))
(def/public (set-initial-matrix [matrix-vector? m])

2
collects/scribblings/draw/dc-intf.scrbl
View File

@ -1151,7 +1151,7 @@ rotation settings have their identity values.
[dy real?])
void?]{
Adds a scaling of @racket[dx] in the X-direction and @racket[dy] in
Adds a translation of @racket[dx] in the X-direction and @racket[dy] in
the Y-direction to the drawing context's current transformation.
Afterward, the drawing context's transformation is represented in the