pict: hline: Add docstring.

* pict.scm (hline): Add docstring.

1 files changed, 7 insertions, 3 deletions

diff --git a/pict.scm b/pict.scm
index f12848c..21312b4 100644
--- a/pict.scm
+++ b/pict.scm
@@ -546,9 +546,13 @@ the line color and line thickness."
                               ,(number->string stroke-width))))))))))
 
 (define* (hline w h
-               #:key
-               (color "black")
-               (stroke-width 1))
+                #:key
+                (color "black")
+                (stroke-width 1))
+  "Return a horizontal line segment of width W.  The bounding box
+height is H and the line is drawn in the vertical 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 ((vcenter (exact->inexact (/ h 2))))
     (line 0 vcenter w vcenter w h
           #:color color #:stroke-width stroke-width)))