pict: vline: Add docstring.

* pict.scm (vline): Add docstring.

1 files changed, 7 insertions, 3 deletions

diff --git a/pict.scm b/pict.scm
index 21312b4..60b7b12 100644
--- a/pict.scm
+++ b/pict.scm
@@ -558,9 +558,13 @@ are accepted to override the line color and line thickness."
           #:color color #:stroke-width stroke-width)))
 
 (define* (vline w h
-               #:key
-               (color "black")
-               (stroke-width 1))
+                #:key
+                (color "black")
+                (stroke-width 1))
+  "Return a vertical line segment of height H.  The bounding box width
+is W and the line is drawn in the horizontal center of the bounding
+box.  The keys COLOR (a string) and STROKE-WIDTH (a number) are
+accepted to override the line color and line thickness."
   (let ((hcenter (exact->inexact (/ w 2))))
     (line hcenter 0 hcenter h w h
           #:color color #:stroke-width stroke-width)))