Fixed three bugs that it sets to other value when the parameter is 0.

Author: dingpinglv

cocos2d/core/platform/CCTypes.js

@@ -36,7 +36,7 @@ cc.Color = function (r, g, b, a) {
     this.r = r || 0;
     this.g = g || 0;
     this.b = b || 0;
-    this.a = a || 255;
+    this.a = (a == null) ? 255 : a;
 };
 
 /**
@@ -66,8 +66,8 @@ cc.color = function (r, g, b, a) {
     if (typeof r === "string")
         return cc.hexToColor(r);
     if (typeof r === "object")
-        return {r: r.r, g: r.g, b: r.b, a: r.a || 255};
-    return  {r: r, g: g, b: b, a: a || 255 };
+        return {r: r.r, g: r.g, b: r.b, a: (r.a == null) ? 255 : r.a};
+    return  {r: r, g: g, b: b, a: (r.a == null) ? 255 : r.a};
 };
 
 /**

cocos2d/core/platform/CCTypesWebGL.js

@@ -74,11 +74,10 @@ cc._tmp.WebGLColor = function () {
         this._rU8[0] = r || 0;
         this._gU8[0] = g || 0;
         this._bU8[0] = b || 0;
-        this._aU8[0] = a || 255;
+        this._aU8[0] = (a == null) ? 255 : a;
 
-        if (a === undefined) {
+        if (a === undefined)
             this.a_undefined = true;
-        }
     };
     /**
      * @constant

extensions/ccui/base-classes/UIWidget.js

@@ -972,7 +972,7 @@ ccui.Widget = ccui.ProtectedNode.extend(/** @lends ccui.Widget# */{
                     this._positionPercent.x = 0;
                     this._positionPercent.y = 0;
                 } else {
-                    if (posY) {
+                    if (posY == undefined) {
                         this._positionPercent.x = pos / pSize.width;
                         this._positionPercent.y = posY / pSize.height;
                     } else {