cocos2dx 3.5 ”hello world“解析

cocos2dx 3.5工程下自带的helloworld程序目录如下：

先看看main.h和main.cpp:

#ifndef __MAIN_H__
#define __MAIN_H__

#define WIN32_LEAN_AND_MEAN             // Exclude rarely-used stuff from Windows headers

// Windows Header Files:
#include <windows.h>
#include <tchar.h>

// C RunTime Header Files
#include "CCStdC.h"

#endif    // __MAIN_H__

#include "main.h"
#include "../Classes/AppDelegate.h"

USING_NS_CC;

int APIENTRY _tWinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPTSTR    lpCmdLine,int       nCmdShow)
{
    UNREFERENCED_PARAMETER(hPrevInstance);
    UNREFERENCED_PARAMETER(lpCmdLine);

    // create the application instance
    AppDelegate app;
    return Application::getInstance()->run();
}

#ifndef  _APP_DELEGATE_H_
#define  _APP_DELEGATE_H_

#include "cocos2d.h"

/**
@brief    The cocos2d Application.

The reason for implement as private inheritance is to hide some interface call by Director.
*/
class  AppDelegate : private cocos2d::Application
{
public:
    AppDelegate();
    virtual ~AppDelegate();

    virtual void initGLContextAttrs();
    
    /**
    @brief    Implement Director and Scene init code here.
    @return true    Initialize success,app continue.
    @return false   Initialize failed,app terminate.
    */
    virtual bool applicationDidFinishLaunching();

    /**
    @brief  The function be called when the application enter background
    @param  the pointer of the application
    */
    virtual void applicationDidEnterBackground();

    /**
    @brief  The function be called when the application enter foreground
    @param  the pointer of the application
    */
    virtual void applicationWillEnterForeground();
};

#endif // _APP_DELEGATE_H_

#include "AppDelegate.h"

#include <vector>
#include <string>

#include "HelloWorldScene.h"
#include "AppMacros.h"

USING_NS_CC;
using namespace std;

AppDelegate::AppDelegate() {

}

AppDelegate::~AppDelegate() 
{
}

void AppDelegate::initGLContextAttrs()
{
    GLContextAttrs glContextAttrs = {8,8,24,8};

    GLView::setGLContextAttrs(glContextAttrs);
}

bool AppDelegate::<strong><span style="color:#ff0000;">applicationDidFinishLaunching</span></strong>() {
    // initialize director
    auto director = Director::getInstance();
    auto glview = director->getOpenGLView();
    if(!glview) {
        glview = GLViewImpl::create("Cpp Empty Test");
        director->setOpenGLView(glview);
    }

    director->setOpenGLView(glview);

    // Set the design resolution
#if (CC_TARGET_PLATFORM == CC_PLATFORM_WP8)
    // a bug in DirectX 11 level9-x on the device prevents ResolutionPolicy::NO_BORDER from working correctly
    glview->setDesignResolutionSize(designResolutionSize.width,designResolutionSize.height,ResolutionPolicy::SHOW_ALL);
#else
    glview->setDesignResolutionSize(designResolutionSize.width,ResolutionPolicy::SHOW_ALL);
#endif

	Size frameSize = glview->getFrameSize();
    
    vector<string> searchPath;

    // In this demo,we select resource according to the frame's height.
    // If the resource size is different from design resolution size,you need to set contentScaleFactor.
    // We use the ratio of resource's height to the height of design resolution,// this can make sure that the resource's height could fit for the height of design resolution.

    // if the frame's height is larger than the height of medium resource size,select large resource.
	if (frameSize.height > mediumResource.size.height)
	{
        searchPath.push_back(largeResource.directory);

        director->setContentScaleFactor(MIN(largeResource.size.height/designResolutionSize.height,largeResource.size.width/designResolutionSize.width));
	}
    // if the frame's height is larger than the height of small resource size,select medium resource.
    else if (frameSize.height > smallResource.size.height)
    {
        searchPath.push_back(mediumResource.directory);
        
        director->setContentScaleFactor(MIN(mediumResource.size.height/designResolutionSize.height,mediumResource.size.width/designResolutionSize.width));
    }
    // if the frame's height is smaller than the height of medium resource size,select small resource.
	else
    {
        searchPath.push_back(smallResource.directory);

        director->setContentScaleFactor(MIN(smallResource.size.height/designResolutionSize.height,smallResource.size.width/designResolutionSize.width));
    }
    
    // set searching path
    FileUtils::getInstance()->setSearchPaths(searchPath);
	
    // turn on display FPS
    director->setDisplayStats(true);

    // set FPS. the default value is 1.0/60 if you don't call this
    director->setAnimationInterval(1.0 / 60);

    // create a scene. it's an autorelease object
    auto scene = HelloWorld::scene();

    // run
    director->runWithScene(scene);

    return true;
}

// This function will be called when the app is inactive. When comes a phone call,it's be invoked too
void AppDelegate::applicationDidEnterBackground() {
    Director::getInstance()->stopAnimation();

    // if you use SimpleAudioEngine,it must be pause
    // SimpleAudioEngine::sharedEngine()->pauseBackgroundMusic();
}

// this function will be called when the app is active again
void AppDelegate::applicationWillEnterForeground() {
    Director::getInstance()->startAnimation();

    // if you use SimpleAudioEngine,it must resume here
    // SimpleAudioEngine::sharedEngine()->resumeBackgroundMusic();
}

1）程序启动后，创建应用程序代理对象，此时会调用其基类构造函数：

Application::Application()
: _instance(nullptr),_accelTable(nullptr)
{
    _instance    = GetModuleHandle(nullptr);
    _animationInterval.QuadPart = 0;
    CC_ASSERT(! sm_pSharedApplication);
    sm_pSharedApplication = this;
}

Application::getInstance()->run();

int Application::run()
{
    PVRFrameEnableControlWindow(false);

    // Main message loop:
    LARGE_INTEGER nLast;
    LARGE_INTEGER nNow;

    QueryPerformanceCounter(&nLast);

    initGLContextAttrs();

    // Initialize instance and cocos2d.
    if (!<span style="color:#ff0000;"><strong>applicationDidFinishLaunching</strong></span>())
    {
        return 0;
    }

    auto director = Director::getInstance();
    auto glview = director->getOpenGLView();

    // Retain glview to avoid glview being released in the while loop
    glview->retain();

    while(!glview->windowShouldClose())
    {
        QueryPerformanceCounter(&nNow);
        if (nNow.QuadPart - nLast.QuadPart > _animationInterval.QuadPart)
        {
            nLast.QuadPart = nNow.QuadPart - (nNow.QuadPart % _animationInterval.QuadPart);
            
            director->mainLoop();
            glview->pollEvents();
        }
        else
        {
            Sleep(1);
        }
    }

    // Director should still do a cleanup if the window was closed manually.
    if (glview->isOpenGLReady())
    {
        director->end();
        director->mainLoop();
        director = nullptr;
    }
    glview->release();
    return true;
}

<span style="color:#ff0000;"><strong>  while(!glview->windowShouldClose())
    {
        QueryPerformanceCounter(&nNow);
        if (nNow.QuadPart - nLast.QuadPart > _animationInterval.QuadPart)
        {
            nLast.QuadPart = nNow.QuadPart - (nNow.QuadPart % _animationInterval.QuadPart);
            
            director->mainLoop();
            glview->pollEvents();
        }
        else
        {
            Sleep(1);
        }<span style="font-family: Arial,Helvetica,sans-serif;">｝</span></strong></span>

可看出这里主要是做渲染场景的工作，glview->pollEvents()代码主要为：

void GLViewImpl::pollEvents()
{
    glfwPollEvents();
}

// Draw the Scene
void Director::drawScene()
{
    // calculate "global" dt
    calculateDeltaTime();
    
    if (_openGLView)
    {
        _openGLView->pollEvents();
    }

    //tick before glClear: issue #533
    if (! _paused)
    {
        <span style="color:#ff0000;"><strong>_scheduler->update(_deltaTime);</strong></span>
        _eventDispatcher->dispatchEvent(_eventAfterUpdate);
    }

    _renderer->clear();

    /* to avoid flickr,nextScene MUST be here: after tick and before draw.
     * FIXME: Which bug is this one. It seems that it can't be reproduced with v0.9
     */
    if (_nextScene)
    {
        setNextScene();
    }

    pushMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);
    
    if (_runningScene)
    {
#if CC_USE_PHYSICS
        auto physicsWorld = _runningScene->getPhysicsWorld();
        if (physicsWorld && physicsWorld->isAutoStep())
        {
            physicsWorld->update(_deltaTime,false);
        }
#endif
        //clear draw stats
        _renderer->clearDrawStats();
        
        //render the scene
        _runningScene->render(_renderer);
        
        _eventDispatcher->dispatchEvent(_eventAfterVisit);
    }

    // draw the notifications node
    if (_notificationNode)
    {
        _notificationNode->visit(_renderer,Mat4::IDENTITY,0);
    }

    if (_displayStats)
    {
        showStats();
    }
    _renderer->render();

    _eventDispatcher->dispatchEvent(_eventAfterDraw);

    popMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);

    _totalFrames++;

    // swap buffers
    if (_openGLView)
    {
        _openGLView->swapBuffers();
    }

    if (_displayStats)
    {
        calculateMPF();
    }
}

// main loop
void Scheduler::update(float dt)
{
    _updateHashLocked = true;

    if (_timeScale != 1.0f)
    {
        dt *= _timeScale;
    }

    //
    // Selector callbacks
    //

    // Iterate over all the Updates' selectors
    tListEntry *entry,*tmp;

    // updates with priority < 0
    DL_FOREACH_SAFE(_updatesNegList,entry,tmp)
    {
        if ((! entry->paused) && (! entry->markedForDeletion))
        {
            entry->callback(dt);
        }
    }

    // updates with priority == 0
    DL_FOREACH_SAFE(_updates0List,tmp)
    {
        if ((! entry->paused) && (! entry->markedForDeletion))
        {
            entry->callback(dt);
        }
    }

    // updates with priority > 0
    DL_FOREACH_SAFE(_updatesPosList,tmp)
    {
        if ((! entry->paused) && (! entry->markedForDeletion))
        {
            entry->callback(dt);
        }
    }

    // Iterate over all the custom selectors
    for (tHashTimerEntry *elt = _hashForTimers; elt != nullptr; )
    {
        _currentTarget = elt;
        _currentTargetSalvaged = false;

        if (! _currentTarget->paused)
        {
            // The 'timers' array may change while inside this loop
            for (elt->timerIndex = 0; elt->timerIndex < elt->timers->num; ++(elt->timerIndex))
            {
                elt->currentTimer = (Timer*)(elt->timers->arr[elt->timerIndex]);
                elt->currentTimerSalvaged = false;

                elt->currentTimer->update(dt);

                if (elt->currentTimerSalvaged)
                {
                    // The currentTimer told the remove itself. To prevent the timer from
                    // accidentally deallocating itself before finishing its step,we retained
                    // it. Now that step is done,it's safe to release it.
                    elt->currentTimer->release();
                }

                elt->currentTimer = nullptr;
            }
        }

        // elt,at this moment,is still valid
        // so it is safe to ask this here (issue #490)
        elt = (tHashTimerEntry *)elt->hh.next;

        // only delete currentTarget if no actions were scheduled during the cycle (issue #481)
        if (_currentTargetSalvaged && _currentTarget->timers->num == 0)
        {
            removeHashElement(_currentTarget);
        }
    }

    // delete all updates that are marked for deletion
    // updates with priority < 0
    DL_FOREACH_SAFE(_updatesNegList,tmp)
    {
        if (entry->markedForDeletion)
        {
            this->removeUpdateFromHash(entry);
        }
    }

    // updates with priority == 0
    DL_FOREACH_SAFE(_updates0List,tmp)
    {
        if (entry->markedForDeletion)
        {
            this->removeUpdateFromHash(entry);
        }
    }

    // updates with priority > 0
    DL_FOREACH_SAFE(_updatesPosList,tmp)
    {
        if (entry->markedForDeletion)
        {
            this->removeUpdateFromHash(entry);
        }
    }

    _updateHashLocked = false;
    _currentTarget = nullptr;

#if CC_ENABLE_SCRIPT_BINDING
    //
    // Script callbacks
    //

    // Iterate over all the script callbacks
    if (!_scriptHandlerEntries.empty())
    {
        for (auto i = _scriptHandlerEntries.size() - 1; i >= 0; i--)
        {
            SchedulerScriptHandlerEntry* eachEntry = _scriptHandlerEntries.at(i);
            if (eachEntry->isMarkedForDeletion())
            {
                _scriptHandlerEntries.erase(i);
            }
            else if (!eachEntry->isPaused())
            {
                eachEntry->getTimer()->update(dt);
            }
        }
    }
#endif
    //
    // Functions allocated from another thread
    //

    // Testing size is faster than locking / unlocking.
    // And almost never there will be functions scheduled to be called.
    if( !_functionsToPerform.empty() ) {
        _performMutex.lock();
        // fixed #4123: Save the callback functions,they must be invoked after '_performMutex.unlock()',otherwise if new functions are added in callback,it will cause thread deadlock.
        auto temp = _functionsToPerform;
        _functionsToPerform.clear();
        _performMutex.unlock();
        for( const auto &function : temp ) {
            function();
        }
        
    }
}

Scene* HelloWorld::scene()
{
    // 'scene' is an autorelease object
    auto scene = Scene::create();
    
    // 'layer' is an autorelease object
    HelloWorld *layer = <span style="color:#ff0000;"><strong>HelloWorld::create</strong></span>();

    // add layer as a child to scene
    scene->addChild(layer);

    // return the scene
    return scene;
}

#define CREATE_FUNC(__TYPE__) 
static __TYPE__* create() 
{ 
    __TYPE__ *pRet = new(std::nothrow) __TYPE__(); 
    if (pRet && pRet->init()) 
    { 
        pRet->autorelease(); 
        return pRet; 
    } 
    else 
    { 
        delete pRet; 
        pRet = NULL; 
        return NULL; 
    } 
}

最后，我们欣赏下glfw框架下的helloworld程序：

#include <glfw3.h>

int main(void)
{
	GLFWwindow* window;

	/* Initialize the library */
	if (!glfwInit())
		return -1;

	/* Create a windowed mode window and its OpenGL context */
	window = glfwCreateWindow(480,320,"Hello World",NULL,NULL);
	if (!window)
	{
		glfwTerminate();
		return -1;
	}

	/* Make the window's context current */
	glfwMakeContextCurrent(window);

	/* Loop until the user closes the window */
	while (!glfwWindowShouldClose(window))
	{
		/* Draw a triangle */
		glBegin(GL_TRIANGLES);

		glColor3f(1.0,0.0,0.0);    // Red
		glVertex3f(0.0,1.0,0.0);

		glColor3f(0.0,0.0);    // Green
		glVertex3f(-1.0,-1.0,1.0);    // Blue
		glVertex3f(1.0,0.0);

		glEnd();

		/* Swap front and back buffers */
		glfwSwapBuffers(window);

		/* Poll for and process events */
		glfwPollEvents();
	}

	glfwTerminate();
	return 0;
}

（编辑：李大同）

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