Improve updateProjectionUniform performance

Author: pandamicro

cocos2d/kazmath/gl/mat4stack.js

@@ -36,6 +36,7 @@
     cc.math.Matrix4Stack = function (top, stack) {
         this.top = top;
         this.stack = stack || [];
+        this.lastUpdated = 0;
         //this._matrixPool = [];            // use pool in next version
     };
     cc.km_mat4_stack = cc.math.Matrix4Stack;

cocos2d/kazmath/gl/matrix.js

@@ -106,6 +106,7 @@
                 throw new Error("Invalid matrix mode specified");   //TODO: Proper error handling
                 break;
         }
+        cc.current_stack.lastUpdated = cc.director.getTotalFrames();
     };
 
     cc.kmGLLoadIdentity = function () {

cocos2d/shaders/CCGLProgram.js

@@ -39,6 +39,7 @@ cc.GLProgram = cc.Class.extend(/** @lends cc.GLProgram# */{
     _uniforms: null,
     _hashForUniforms: null,
     _usesTime: false,
+    _projectionUpdated: -1,
 
     // Uniform cache
     _updateUniformLocation: function (location) {
@@ -684,8 +685,12 @@ cc.GLProgram = cc.Class.extend(/** @lends cc.GLProgram# */{
         this._glContext.uniformMatrix4fv(this._uniforms[cc.UNIFORM_PMATRIX_S], false, cc.projection_matrix_stack.top.mat);
     },
 
-    _updateProjectionUniform: function(){
-        this._glContext.uniformMatrix4fv(this._uniforms[cc.UNIFORM_PMATRIX_S], false, cc.projection_matrix_stack.top.mat);  
+    _updateProjectionUniform: function () {
+        var stack = cc.projection_matrix_stack;
+        if (stack.lastUpdated !== this._projectionUpdated) {
+            this._glContext.uniformMatrix4fv(this._uniforms[cc.UNIFORM_PMATRIX_S], false, stack.top.mat);
+            this._projectionUpdated = stack.lastUpdated;
+        }
     },
 
     /**