From a5e0a9378daaee6a04ce8e2298e9d87137ee6048 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Thu, 30 Aug 2018 07:46:33 -0400
Subject: node-2d: Add follow-bezier-path method.

---
 starling/node-2d.scm | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/starling/node-2d.scm b/starling/node-2d.scm
index ccbb17b..8e3cad6 100644
--- a/starling/node-2d.scm
+++ b/starling/node-2d.scm
@@ -21,6 +21,7 @@
 ;;; Code:
 
 (define-module (starling node-2d)
+  #:use-module (chickadee math bezier)
   #:use-module (chickadee math easings)
   #:use-module (chickadee math matrix)
   #:use-module (chickadee math rect)
@@ -67,6 +68,7 @@
             rotate-to
             scale-by
             scale-to
+            follow-bezier-path
 
             <sprite>
             texture
@@ -349,6 +351,22 @@
 (define-method (scale-by (node <node-2d>) dsx dsy duration)
   (scale-by node dsx dsy duration smoothstep))
 
+(define-method (follow-bezier-path (node <node-2d>) path duration forward?)
+  (let ((p (position node))
+        (path (if forward? path (reverse path))))
+    (for-each (lambda (bezier)
+                (tween duration
+                       (if forward? 0.0 1.0)
+                       (if forward? 1.0 0.0)
+                       (lambda (t)
+                         (bezier-curve-point-at! p bezier t)
+                         (dirty! node))
+                       #:ease linear))
+              path)))
+
+(define-method (follow-bezier-path (node <node-2d>) path duration)
+  (follow-bezier-path node path duration #t))
+
 ;; Events
 
 (define-method (update* (node <node-2d>) dt)
-- 
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