摘要: 此文对cocos2d-x引擎中最具代表性,最能体现框架结构的几个类做了简单的介绍, 包括Director,Application, Renderer, EventDispatcher, Scheduler. 对于这些类, 也只对关系主要流程的方法做了介绍, 略过了容错代码和其它细节. 主要目的是让大家快速的对cocos2d-x引擎有一个全面笼统的认识, 也方便快速定位问题.

• 博客: http://www.cnblogs.com/jhzhu
• 邮箱: jhzhuustc@gmail.com
• 作者: 知明所以
• 时间: 2014-07-21

GLView

cocos2d-x对openGL的封装. 不同平台下, openGL有一些差别.

openGL

一段简单的例子

以下内容引用自Introduction to OpenGL. 需要更具体的介绍也可参考这个链接.

#include <whateverYouNeed.h>main() {   InitializeAWindowPlease();   glClearColor (0.0, 0.0, 0.0, 0.0);   glClear (GL_COLOR_BUFFER_BIT);   glColor3f (1.0, 1.0, 1.0);   glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);   glBegin(GL_POLYGON);      glVertex3f (0.25, 0.25, 0.0);      glVertex3f (0.75, 0.25, 0.0);      glVertex3f (0.75, 0.75, 0.0);      glVertex3f (0.25, 0.75, 0.0);   glEnd();   glFlush();   UpdateTheWindowAndCheckForEvents();}

OpenGL Command Syntax

• OpenGL commands use the prefix gl and initial capital letters for each word making up the command name
• some seemingly extraneous letters appended to some command names (for example, the 3f in glColor3f() and glVertex3f())

OpenGL as a State Machine

OpenGL is a state machine. You put it into various states (or modes) that then remain in effect until you change them.

Application

主要方法:

virtual const char * getCurrentLanguage();virtual Platform getTargetPlatform();virtual void setAnimationInterval(double interval);int run();//启动主循环

run()函数

int Application::run(){    ...    while(!glview->windowShouldClose())    {        QueryPerformanceCounter(&nNow);        if (nNow.QuadPart - nLast.QuadPart > _animationInterval.QuadPart)        {            nLast.QuadPart = nNow.QuadPart;            director->mainLoop();       //Director进行这一帧的渲染            glview->pollEvents();       // This function processes only those events that have already been received and then returns immediately.        }        else        {            Sleep(0);        }    }    ...    return true;}

Director

主要函数预览

//openGL Matrix Operate    void pushMatrix(MATRIX_STACK_TYPE type);    void popMatrix(MATRIX_STACK_TYPE type);    void loadIdentityMatrix(MATRIX_STACK_TYPE type);    void loadMatrix(MATRIX_STACK_TYPE type, const Mat4& mat);    void multiplyMatrix(MATRIX_STACK_TYPE type, const Mat4& mat);    Mat4 getMatrix(MATRIX_STACK_TYPE type);    void resetMatrixStack();//View Data    inline double getAnimationInterval();    inline bool isDisplayStats();    inline GLView* getOpenGLView();    inline Projection getProjection();    Size getVisibleSize() const;    Vec2 getVisibleOrigin() const;    Vec2 convertToGL(const Vec2& point);    Vec2 convertToUI(const Vec2& point);    float getZEye() const;// Scene 场景管理    inline Scene* getRunningScene();    void runWithScene(Scene *scene);    void pushScene(Scene *scene);// 控制绘制的暂停和恢复    void end();    void pause();    void resume();//绘制图形(界面展示最重要的函数)    void drawScene();//Getter and Setter    Scheduler* getScheduler() const { return _scheduler; }    void setScheduler(Scheduler* scheduler);    ActionManager* getActionManager() const { return _actionManager; }    void setActionManager(ActionManager* actionManager);    EventDispatcher* getEventDispatcher() const { return _eventDispatcher; }    void setEventDispatcher(EventDispatcher* dispatcher);    Renderer* getRenderer() const { return _renderer; }

drawScene(): 主要绘制函数

// Draw the Scenevoid Director::drawScene(){    ...    if (! _paused)    {        _scheduler->update(_deltaTime);                         //Scheduler 定时器 更新        _eventDispatcher->dispatchEvent(_eventAfterUpdate);     //Dispatcher 抛发事件.    }    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);         //glClear    if (_nextScene)                                             //取得下一个将要显示的Scene.    {        setNextScene();    }    pushMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);      //将上一次绘制的Context放到堆栈    // draw the scene    if (_runningScene)    {        _runningScene->visit(_renderer, Mat4::IDENTITY, false);        _eventDispatcher->dispatchEvent(_eventAfterVisit);    }    _renderer->render();                                        //渲染    _eventDispatcher->dispatchEvent(_eventAfterDraw);    popMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);       //返回到上一次绘制时的状态.    // swap buffers    if (_openGLView)    {        _openGLView->swapBuffers();                             //把上面渲染的结果显示到屏幕    }    ...}

Node::visit() 函数

预览

Node::visit() 的主要功能就是

1. 调用所有孩子的visit函数
2. 调用self->draw()函数

void Node::visit(Renderer* renderer, const Mat4 &parentTransform, uint32_t parentFlags){    // quick return if not visible. children won‘t be drawn.    if (!_visible)    {        return;    }    uint32_t flags = processParentFlags(parentTransform, parentFlags);    // IMPORTANT:    // To ease the migration to v3.0, we still support the Mat4 stack,    // but it is deprecated and your code should not rely on it    Director* director = Director::getInstance();    director->pushMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);    director->loadMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW, _modelViewTransform);    int i = 0;    if(!_children.empty())    {        sortAllChildren();        // draw children zOrder < 0        for( ; i < _children.size(); i++ )        {            auto node = _children.at(i);            if ( node && node->_localZOrder < 0 )                node->visit(renderer, _modelViewTransform, flags);            else                break;        }        // self draw        this->draw(renderer, _modelViewTransform, flags);        for(auto it=_children.cbegin()+i; it != _children.cend(); ++it)            (*it)->visit(renderer, _modelViewTransform, flags);    }    else    {        this->draw(renderer, _modelViewTransform, flags);    }    director->popMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);}

Node::draw()

因为Node是所有可显示对象的父类, 没有任何显示内容, 所以draw函数为空.
这里我们以Sprite::draw函数为例简单介绍下draw的作用.

void Sprite::draw(Renderer *renderer, const Mat4 &transform, uint32_t flags){    // Don‘t do calculate the culling if the transform was not updated    _insideBounds = (flags & FLAGS_TRANSFORM_DIRTY) ? renderer->checkVisibility(transform, _contentSize) : _insideBounds;    if(_insideBounds)    {        _quadCommand.init(_globalZOrder, _texture->getName(), getGLProgramState(), _blendFunc, &_quad, 1, transform);        renderer->addCommand(&_quadCommand);    }}

我们看到, Sprite::draw函数主要实现了[添加一个QuadCommand到Render中去]的功能.
再看看Label的绘制函数.

Label::draw

void Label::draw(Renderer *renderer, const Mat4 &transform, uint32_t flags){    // Don‘t do calculate the culling if the transform was not updated    _insideBounds = (flags & FLAGS_TRANSFORM_DIRTY) ? renderer->checkVisibility(transform, _contentSize) : _insideBounds;    if(_insideBounds) {        _customCommand.init(_globalZOrder);        _customCommand.func = CC_CALLBACK_0(Label::onDraw, this, transform, flags);        renderer->addCommand(&_customCommand);    }}

其实, 跟Sprite::draw也差不多. 关键在于这个RenderCommand怎么构造和执行的.

Renderer 渲染器

主要函数预览

    void initGLView();    /** Adds a `RenderComamnd` into the renderer */    void addCommand(RenderCommand* command);    /** Adds a `RenderComamnd` into the renderer specifying a particular render queue ID */    void addCommand(RenderCommand* command, int renderQueue);    /** Pushes a group into the render queue */    void pushGroup(int renderQueueID);    /** Pops a group from the render queue */    void popGroup();    /** Creates a render queue and returns its Id */    int createRenderQueue();    /** Renders into the GLView all the queued `RenderCommand` objects */    void render();

可见它主要由两个功能:

1. 对ReanderCommand进行排序和分类管理
2. 进行渲染:render()

渲染函数Renderer::render()

void Renderer::render(){   ...    if (_glViewAssigned)    {       ...        //排列渲染队列        for (auto &renderqueue : _renderGroups)        {            renderqueue.sort();        }         //进行渲染        visitRenderQueue(_renderGroups[0]);        ...    }    ...}

Renderer::visitRenderQueue

按照顺序执行所有的 RenderCommand

void Renderer::visitRenderQueue(const RenderQueue& queue){    ssize_t size = queue.size();    for (ssize_t index = 0; index < size; ++index)    {        auto command = queue[index];        auto commandType = command->getType();        if(RenderCommand::Type::QUAD_COMMAND == commandType)        {            auto cmd = static_cast<QuadCommand*>(command);            //Batch quads            if(_numQuads + cmd->getQuadCount() > VBO_SIZE)            {                drawBatchedQuads();            }            _batchedQuadCommands.push_back(cmd);            memcpy(_quads + _numQuads, cmd->getQuads(), sizeof(V3F_C4B_T2F_Quad) * cmd->getQuadCount());            convertToWorldCoordinates(_quads + _numQuads, cmd->getQuadCount(), cmd->getModelView());            _numQuads += cmd->getQuadCount();        }        else if(RenderCommand::Type::GROUP_COMMAND == commandType)        {            flush();            int renderQueueID = ((GroupCommand*) command)->getRenderQueueID();            visitRenderQueue(_renderGroups[renderQueueID]);        }        else if(RenderCommand::Type::CUSTOM_COMMAND == commandType)        {            ...        }        ...    }}

openGL VAO, VBO 介绍.

GLSL渲染语言入门与VBO、VAO使用：绘制一个三角形
OpenGL 4.0 VAO VBO 理解

Schelduler介绍

Schelduler是cocos2d-x中实现延迟调用,定时调用时最重要的功能. 类似于其他语言中的Timer
他最核心的函数就是:

void schedule(const ccSchedulerFunc& callback, void *target, float interval, unsigned int repeat, float delay, bool paused, const std::string& key);

用来启动一个定时操作: 在延迟delay时间后, 每隔repeat时间, 调用一次callback. target用来标记这个操作属于谁, 方便管理, 比如在析构的时候调用void unschedule(void *target)即可移除当前对象的所有定时操作.

Schelduler的其它大部分方法, 要么是它的衍生, 为了减少调用参数; 要么是对定时操作的控制, 比如暂停, 恢复, 移除等. 如果只对想对框架的各个模块有大概的了解, 可以不做深入.

EventDispatcher

(后续添加)

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