[doc] docstring on with-grid-bezier

1 files changed, 13 insertions, 3 deletions

diff --git a/src/grid-geometry.lisp b/src/grid-geometry.lisp
index b23b207..c046032 100644
--- a/src/grid-geometry.lisp
+++ b/src/grid-geometry.lisp
@@ -102,9 +102,19 @@ top right corners of the bounding box for POLY "
 
 
 (defmacro with-grid-bezier
-    ((x y) (control-pts &key (step 0.001)) &body body)
-  (with-gensyms (fn points a)
-    `(let* ((,points
+    ((x y) (control-pts &key (count 1000)) &body body)
+  "CONTROL-POINTS is an expression that evalueates to a list of (X Y)
+pairs, these are the control points for the curve.. COUNT is the
+number of points on the bezier curve that will be calclated. The first
+point is always the first control point and the last point is always
+the last control point.  Use high counts for smooth curves, as needed.
+
+Evaluates the BODY with X Y bound to a point on the bezier curve.
+"
+  (with-gensyms (fn points a step)
+    `(let* ((,step
+              (/ 1.0 ,count))
+            (,points
               ,control-pts)
             (,fn
               (apply #'bezier-lambda ,points)))