Fix `draw-line` procedure.

* sicp-picture-language.scm(draw-line): Fix.

1 files changed, 6 insertions, 9 deletions

diff --git a/sicp-picture-language.scm b/sicp-picture-language.scm
index 39f9c8e..379aa0e 100644
--- a/sicp-picture-language.scm
+++ b/sicp-picture-language.scm
@@ -122,15 +122,12 @@
     (($ <vect> x1 y1)
      (match end-vect
        (($ <vect> x2 y2)
-        (let* ((screen (current-screen))
-               (w (pict-width screen))
-               (h (pict-height screen)))
-          (current-screen
-           (lb-superimpose
-            (line (* w x1) (- h (* h y1))
-                  (* w x2) (- h (* h y2))
-                  #:stroke-width (current-line-stroke-width)
-                  #:color (current-line-color))))))))))
+        (let ((screen (current-screen)))
+          (let ((l (line x1 y1
+                         x2 y2
+                         #:stroke-width (current-line-stroke-width)
+                         #:color (current-line-color))))
+            (current-screen (pin-over screen 0 0 l)))))))))
 
 (define current-screen (make-parameter #f))
 (define current-pict-ids (make-parameter '()))