Adapt mx.effects.easing or Tweener functions to be used for paths.

git-svn-id: svn+ssh://src.earth.threerings.net/nenya/trunk@367 ed5b42cb-e716-0410-a449-f6a68f950b19

src/as/com/threerings/flash/path/EasingPath.as

@@ -0,0 +1,70 @@
+//
+// $Id: LinePath.as 359 2007-12-03 21:08:33Z dhoover $
+
+package com.threerings.flash.path {
+
+import flash.display.DisplayObject;
+
+/**
+ * Adapts mx.effects.easing or Tweener functions for use as a Path.
+ */
+public class EasingPath extends Path
+{
+    /**
+     * @param destX the destination x coordinate
+     * @param destY the destination y coordinate
+     * @param duration the duration of the path, in milliseconds.
+     * @param xfunc a Function to provide x coordinates. Signature: 
+     *        function (t :Number, b :Number, c :Number, d :Number) :Number
+     *        t = elapsed time
+     *        b = initial position
+     *        c = total change in position
+     *        d = duration
+     * @param yfunc a Function to provide y coordinates. If omitted, the xfunc is used.
+     * @param startX the starting x coordinate. If omitted, the DisplayObject's current coordinate
+     *        is used.
+     * @param startY the starting y coordinate. If omitted, the DisplayObject's current coordinate
+     *        is used.
+     */
+    public function EasingPath (
+        target :DisplayObject, destX :Number, destY :Number, duration :int,
+        xfunc :Function, yfunc :Function = null, startX :Number = NaN, startY :Number = NaN)
+    {
+        if (isNaN(startX)) {
+            startX = target.x;
+        }
+        if (isNaN(startY)) {
+            startY = target.y;
+        }
+        if (yfunc == null) {
+            yfunc = xfunc;
+        }
+        _duration = duration;
+        _startX = startX;
+        _startY = startY;
+        _deltaX = destX - startX;
+        _deltaY = destY - startY;
+        _xfunc = xfunc;
+        _yfunc = yfunc;
+        init(target);
+    }
+
+    override protected function tick (curStamp :int) :int
+    {
+        var t :Number = curStamp - _startStamp;
+        _target.x = _xfunc(t, _startX, _deltaX, _duration);
+        _target.y = _yfunc(t, _startY, _deltaY, _duration);
+
+        // return the number of milliseconds before we're done
+        return _duration - t;
+    }
+
+    protected var _xfunc :Function;
+    protected var _yfunc :Function;
+    protected var _startX :Number;
+    protected var _startY :Number;
+    protected var _deltaX :Number;
+    protected var _deltaY :Number;
+    protected var _duration :int;
+}
+}