add the Quad easing methods for Tween

git-svn-id: http://svn.openlayers.org/trunk/openlayers@6415 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Tween.js

@@ -268,3 +268,51 @@ OpenLayers.Easing.Expo = {
 
     CLASS_NAME: "OpenLayers.Easing.Expo"
 };
+
+/**
+ * Namespace: OpenLayers.Easing.Quad
+ */
+OpenLayers.Easing.Quad = {
+    
+    /**
+     * Function: easeIn
+     * 
+     * Parameters:
+     * t - {Float} time
+     * b - {Float} beginning position
+     * c - {Float} total change
+     * d - {Float} duration of the transition
+     */
+    easeIn: function(t, b, c, d) {
+        return c*(t/=d)*t + b;
+    },
+    
+    /**
+     * Function: easeOut
+     * 
+     * Parameters:
+     * t - {Float} time
+     * b - {Float} beginning position
+     * c - {Float} total change
+     * d - {Float} duration of the transition
+     */
+    easeOut: function(t, b, c, d) {
+        return -c *(t/=d)*(t-2) + b;
+    },
+    
+    /**
+     * Function: easeInOut
+     * 
+     * Parameters:
+     * t - {Float} time
+     * b - {Float} beginning position
+     * c - {Float} total change
+     * d - {Float} duration of the transition
+     */
+    easeInOut: function(t, b, c, d) {
+        if ((t/=d/2) < 1) return c/2*t*t + b;
+		return -c/2 * ((--t)*(t-2) - 1) + b;
+    },
+
+    CLASS_NAME: "OpenLayers.Easing.Quad"
+};

tests/manual/tween.html

@@ -65,6 +65,7 @@
     <select name="transition" id="transition" onchange="changeTween()">
         <option value="Linear">Linear</option>
         <option value="Expo">Expo</option>
+        <option value="Quad">Quad</option>
     </select>
     <select name="easing" id="easing" onchange="changeTween()">
         <option value="easeIn">EaseIn</option>