Save the bound texture unit so that the sampler can be updated dynamiclly.

cocos/renderer/CCGLProgramState.cpp

@@ -497,9 +497,21 @@ void GLProgramState::setUniformTexture(const std::string &uniformName, GLuint te
 {
     auto v = getUniformValue(uniformName);
     if (v)
-        v->setTexture(textureId, _textureUnitIndex++);
+    {
+        if (_boundTextureUnits.find(uniformName) != _boundTextureUnits.end())
+        {
+            v->setTexture(textureId, _boundTextureUnits[uniformName]);
+        }
+        else
+        {
+            v->setTexture(textureId, _textureUnitIndex);
+            _boundTextureUnits[uniformName] = _textureUnitIndex++;
+        }
+    }
     else
+    {
         CCLOG("cocos2d: warning: Uniform not found: %s", uniformName.c_str());
+    }
 }
 
 

cocos/renderer/CCGLProgramState.h

@@ -191,6 +191,7 @@ protected:
     bool _uniformAttributeValueDirty;
     std::unordered_map<std::string, UniformValue> _uniforms;
     std::unordered_map<std::string, VertexAttribValue> _attributes;
+    std::unordered_map<std::string, int> _boundTextureUnits;
 
     int _textureUnitIndex;
     uint32_t _vertexAttribsFlags;

tests/cpp-tests/Classes/ShaderTest/ShaderTest.cpp

@@ -785,27 +785,31 @@ bool ShaderMultiTexture::init()
 
         // Right: normal sprite
         auto right = Sprite::create("Images/grossinis_sister2.png");
-        addChild(right);
+        addChild(right, 0, rightSpriteTag);
         right->setPosition(s.width*3/4, s.height/2);
 
 
         // Center: MultiTexture
-        _sprite = Sprite::create("Images/grossinis_sister1.png");
-        Texture2D *texture1 = Director::getInstance()->getTextureCache()->addImage("Images/grossinis_sister2.png");
-
+        _sprite = Sprite::createWithTexture(left->getTexture());
         addChild(_sprite);
-
         _sprite->setPosition(Vec2(s.width/2, s.height/2));
 
         auto glprogram = GLProgram::createWithFilenames("Shaders/example_MultiTexture.vsh", "Shaders/example_MultiTexture.fsh");
         auto glprogramstate = GLProgramState::getOrCreateWithGLProgram(glprogram);
         _sprite->setGLProgramState(glprogramstate);
 
-        glprogramstate->setUniformTexture("u_texture1", texture1);
+        glprogramstate->setUniformTexture("u_texture1", right->getTexture());
         glprogramstate->setUniformFloat("u_interpolate",0.5);
 
         // slider
         createSliderCtl();
+        
+        // menu
+        auto label = Label::createWithTTF(TTFConfig("fonts/arial.ttf"), "change");
+        auto mi = MenuItemLabel::create(label, CC_CALLBACK_1(ShaderMultiTexture::changeTexture, this));
+        auto menu = Menu::create(mi, nullptr);
+        addChild(menu);
+        menu->setPosition(s.width * 7 / 8, s.height / 2);
 
         return true;
     }
@@ -813,6 +817,21 @@ bool ShaderMultiTexture::init()
     return false;
 }
 
+void ShaderMultiTexture::changeTexture(Ref*)
+{
+    static const int textureFilesCount = 3;
+    static const std::string textureFiles[textureFilesCount] = {
+        "Images/grossini.png",
+        "Images/grossinis_sister1.png",
+        "Images/grossinis_sister2.png"
+    };
+    auto textrue = Director::getInstance()->getTextureCache()->addImage(textureFiles[_changedTextureId++ % textureFilesCount]);
+    Sprite* right = dynamic_cast<Sprite*>(getChildByTag(rightSpriteTag));
+    right->setTexture(textrue);
+    auto programState = _sprite->getGLProgramState();
+    programState->setUniformTexture("u_texture1", right->getTexture());
+}
+
 
 ///---------------------------------------
 //

tests/cpp-tests/Classes/ShaderTest/ShaderTest.h

@@ -166,9 +166,12 @@ public:
 
 class ShaderMultiTexture : public ShaderTestDemo
 {
+    static const int rightSpriteTag = 2014;
 public:
     ShaderMultiTexture();
     ui::Slider* createSliderCtl();
+    void changeTexture(Ref*);
+    int _changedTextureId;
     Sprite *_sprite;
 
     virtual std::string title() const override;