pict: ellipse: Consider the stroke width when computing dimensions.

* pict.scm (ellipse): Offset drawing by half the stroke width.

1 files changed, 15 insertions, 13 deletions

diff --git a/pict.scm b/pict.scm
index e1a6f82..27f8fdd 100644
--- a/pict.scm
+++ b/pict.scm
@@ -707,19 +707,21 @@ the given COLOR."
 BORDER-COLOR (a string) and BORDER-WIDTH (a number) are accepted to
 override the line color and line thickness."
   (make-pict
-   `(svg (@ (width ,w)
-            (height ,h)
-            (x 0)
-            (y 0))
-         (ellipse (@ (style ,(style-list->string
-                              `(("fill" "none")
-                                ("stroke" ,border-color)
-                                ("stroke-width"
-                                 ,(number->string border-width)))))
-                     (cx ,(/ w 2))
-                     (cy ,(/ h 2))
-                     (rx ,(/ w 2))
-                     (ry ,(/ h 2)))))))
+   (let ((w* (- w border-width))
+         (h* (- h border-width)))
+     `(svg (@ (width ,w)
+              (height ,h)
+              (x 0)
+              (y 0))
+           (ellipse (@ (style ,(style-list->string
+                                `(("fill" "none")
+                                  ("stroke" ,border-color)
+                                  ("stroke-width"
+                                   ,(number->string border-width)))))
+                       (cx ,(exact->inexact (+ (/ w* 2) (/ border-width 2))))
+                       (cy ,(exact->inexact (+ (/ h* 2) (/ border-width 2))))
+                       (rx ,(exact->inexact (/ w* 2)))
+                       (ry ,(exact->inexact (/ h* 2)))))))))
 
 (define* (filled-ellipse w h #:key (color "black"))
   (remove-outline (fill (ellipse w h) color)))