1.WinSize->CCDirector.cpp

const Size& Director::getWinSize(void) const
{
    return _winSizeInPoints;      /*看這裡返回的這個值，是在setOpenGLView中賦值的*/
}

void Director::setOpenGLView(GLView *openGLView)
{
    CCASSERT(openGLView, "opengl view should not be null");

    if (_openGLView != openGLView)
    {
        // Configuration. Gather GPU info
        Configuration *conf = Configuration::getInstance();
        conf->gatherGPUInfo();
        CCLOG("%s\n",conf->getInfo().c_str());

        if(_openGLView)
            _openGLView->release();
        _openGLView = openGLView;
        _openGLView->retain();

        // set size
        _winSizeInPoints = _openGLView->getDesignResolutionSize(); /*重點:可見winsize就是設計解析度大小*/

        _isStatusLabelUpdated = true;

        if (_openGLView)
        {
            setGLDefaultValues();
        }

        _renderer->initGLView();

        CHECK_GL_ERROR_DEBUG();

        if (_eventDispatcher)
        {
            _eventDispatcher->setEnabled(true);
        }
        
        _defaultFBO = experimental::FrameBuffer::getOrCreateDefaultFBO(_openGLView);
        _defaultFBO->retain();
    }
}
 

2.VisibleSize->CCGLView.cpp

Size GLView::getVisibleSize() const
{
    /*
      1.可見,visibleSize除了在NO_BORDER這種特殊情況下，其餘的也等於設計解析度大小(很容易理解:因為除了NO_BORDER情況下，其餘UI介面都是顯示完全的呀!當然可視大小就等於CocosStudio中那個畫布的大小，即設計解析度大小)
      2.可見,在非NO_BORDER情況下，winSize和VisibleSize大小是一樣的
    */
    if (_resolutionPolicy == ResolutionPolicy::NO_BORDER)  
    {
        return Size(_screenSize.width/_scaleX, _screenSize.height/_scaleY);
    }
    else 
    {
        return _designResolutionSize;
    }
}
 

android下視窗建立過程

3.FrameSize->CCGLView.cpp

//也就是說:最開始一單傳入完畢，那麼就固定不變了，到底width和height在那裡傳入的呢?下面以cocos2dx 3.10版本原始碼.  android系統為例子進行分析。
void GLView::setFrameSize(float width, float height)
{
    _designResolutionSize = _screenSize = Size(width, height); //setFrameSize設定的值儲存為螢幕大小了
}

//返回設定的setFrameSize大小
const Size& GLView::getFrameSize() const
{
    return _screenSize;
}

//android下面，通過android系統api，獲取到螢幕的大小.對就是螢幕的大小！！！前2個引數，是螢幕變化後的寬高，後2個是變化前的寬高
 @Override
    protected void onSizeChanged(final int pNewSurfaceWidth, final int pNewSurfaceHeight, final int pOldSurfaceWidth, final int pOldSurfaceHeight) {
        if(!this.isInEditMode()) {
            this.mCocos2dxRenderer.setScreenWidthAndHeight(pNewSurfaceWidth, pNewSurfaceHeight);
        }
    }

//根據獲得螢幕的大小，設定暫存下螢幕大小
public void setScreenWidthAndHeight(final int surfaceWidth, final int surfaceHeight) {
        this.mScreenWidth = surfaceWidth;
        this.mScreenHeight = surfaceHeight;
    }

//android通過jni呼叫cocos2dx的介面，根據android系統獲取到的螢幕寬高，傳給cocos2dx，然後設定OpenGLView視窗
@Override
    public void onSurfaceCreated(final GL10 GL10, final EGLConfig EGLConfig) {
        Cocos2dxRenderer.nativeInit(this.mScreenWidth, this.mScreenHeight);
        this.mLastTickInNanoSeconds = System.nanoTime();
        mNativeInitCompleted = true;
    }


//可見，setFrameSize在Android等系統內，是自動呼叫，傳入的大小，所以GL視窗的大小恰好等於Android手機螢幕的大小
JNIEXPORT void Java_org_cocos2dx_lib_Cocos2dxRenderer_nativeInit(JNIEnv*  env, jobject thiz, jint w, jint h)
{
    auto director = cocos2d::Director::getInstance();
    auto glview = director->getOpenGLView();
    if (!glview)
    {
        glview = cocos2d::GLViewImpl::create("Android app");
        glview->setFrameSize(w, h);  //在這傳入視窗大小了，從而啟動應用
        director->setOpenGLView(glview);

        cocos2d::Application::getInstance()->run();
    }
    else
    {
        cocos2d::GL::invalidateStateCache();
        cocos2d::GLProgramCache::getInstance()->reloadDefaultGLPrograms();
        cocos2d::DrawPrimitives::init();
        cocos2d::VolatileTextureMgr::reloadAllTextures();

        cocos2d::EventCustom recreatedEvent(EVENT_RENDERER_RECREATED);
        director->getEventDispatcher()->dispatchEvent(&recreatedEvent);
        director->setGLDefaultValues();
    }
    cocos2d::network::_preloadJavaDownloaderClass();
}
 

ios下視窗建立過程

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    
    
    cocos2d::Application *app = cocos2d::Application::getInstance();
    app->initGLContextAttrs();
    cocos2d::GLViewImpl::convertAttrs();
    
    // Override point for customization after application launch.
    
    // Add the view controller's view to the window and display.
    /*
	[email protected](nonatomic) CGRect            bounds;      // default bounds is zero origin, frame size. animatable
	2.可見建立的這個eaglView視窗大小也是自動傳入，等於螢幕大小.所以不要看別人bb，自己看下原始碼，一切瞭如指掌了。
    */
    window = [[UIWindow alloc] initWithFrame: [[UIScreen mainScreen] bounds]];
    CCEAGLView *eaglView = [CCEAGLView viewWithFrame: [window bounds]
                                         pixelFormat: (NSString*)cocos2d::GLViewImpl::_pixelFormat
                                         depthFormat: cocos2d::GLViewImpl::_depthFormat
                                  preserveBackbuffer: NO
                                          sharegroup: nil
                                       multiSampling: NO
                                     numberOfSamples: 0 ];
    
    [eaglView setMultipleTouchEnabled:NO];

    // Use RootViewController manage CCEAGLView
    viewController = [[RootViewController alloc] initWithNibName:nil bundle:nil];
    viewController.wantsFullScreenLayout = YES;
    viewController.view = eaglView;
    
    // Set RootViewController to window
    if ( [[UIDevice currentDevice].systemVersion floatValue] < 6.0)
    {
        // warning: addSubView doesn't work on iOS6
        [window addSubview: viewController.view];
    }
    else
    {
        // use this method on ios6
        [window setRootViewController:viewController];
    }
    
    [window makeKeyAndVisible];
    
    [[UIApplication sharedApplication] setStatusBarHidden: YES];
    
    //覆蓋安裝時第一次執行需清除遊戲快取
    std::string version = cocos2d::UserDefault::getInstance()->getStringForKey([RUN_VERSION UTF8String]);
    NSString* runVersion = [NSString stringWithUTF8String:version.c_str()];
    NSString* appVersion = [NativeInterface getVersionName];
    if(![appVersion isEqualToString:runVersion]){
        
        std::string cachePath = cocos2d::FileUtils::getInstance()->getWritablePath();
        NSString* path = [NSString stringWithUTF8String:cachePath.c_str()];
        NSFileManager *fileManager=[NSFileManager defaultManager];
        if ([fileManager fileExistsAtPath:path]) {
            NSArray *childerFiles=[fileManager subpathsAtPath:path];
            for (NSString *fileName in childerFiles) {
                NSString *absolutePath=[path stringByAppendingPathComponent:fileName];
                [fileManager removeItemAtPath:absolutePath error:nil];
            }
        }
        
        cocos2d::UserDefault::getInstance()->setStringForKey([RUN_VERSION UTF8String], [appVersion UTF8String]);
    }
    
  
    //do something 
    
    // IMPORTANT: Setting the GLView should be done after creating the RootViewController
    cocos2d::GLView *glview = cocos2d::GLViewImpl::createWithEAGLView(eaglView);
    cocos2d::Director::getInstance()->setOpenGLView(glview);
    
   
    
    app->run();  //跑起來吧...
    return YES;
}

那麼，螢幕適配策略，cocos2dx是怎麼起作用的呢?也就是setDesignResolution到底是怎麼起作用的呢？

//設定設計解析度(也就是我們看到的視窗)
void GLView::setDesignResolutionSize(float width, float height, ResolutionPolicy resolutionPolicy)
{
    CCASSERT(resolutionPolicy != ResolutionPolicy::UNKNOWN, "should set resolutionPolicy");
    
    if (width == 0.0f || height == 0.0f)
    {
        return;
    }

    _designResolutionSize.setSize(width, height);
    _resolutionPolicy = resolutionPolicy;
    
    //設定完適配策略後，生效
    updateDesignResolutionSize();
 }

//
void GLView::updateDesignResolutionSize()
{
    if (_screenSize.width > 0 && _screenSize.height > 0
        && _designResolutionSize.width > 0 && _designResolutionSize.height > 0)
    {
        _scaleX = (float)_screenSize.width / _designResolutionSize.width;
        _scaleY = (float)_screenSize.height / _designResolutionSize.height;
        
        if (_resolutionPolicy == ResolutionPolicy::NO_BORDER)
        {
            _scaleX = _scaleY = MAX(_scaleX, _scaleY);
        }
        
        else if (_resolutionPolicy == ResolutionPolicy::SHOW_ALL)
        {
            _scaleX = _scaleY = MIN(_scaleX, _scaleY);
        }
        
        else if ( _resolutionPolicy == ResolutionPolicy::FIXED_HEIGHT) {
            _scaleX = _scaleY;
            _designResolutionSize.width = ceilf(_screenSize.width/_scaleX);
        }
        
        else if ( _resolutionPolicy == ResolutionPolicy::FIXED_WIDTH) {
            _scaleY = _scaleX;
            _designResolutionSize.height = ceilf(_screenSize.height/_scaleY);
        }
        
        // calculate the rect of viewport
	//按照適配策略計算出來的放縮比例,更改視口大小
        float viewPortW = _designResolutionSize.width * _scaleX;
        float viewPortH = _designResolutionSize.height * _scaleY;
        
        _viewPortRect.setRect((_screenSize.width - viewPortW) / 2, (_screenSize.height - viewPortH) / 2, viewPortW, viewPortH);
        
        // reset director's member variables to fit visible rect
        auto director = Director::getInstance();
        director->_winSizeInPoints = getDesignResolutionSize();  //重點:再次設定winSize大小，可見winSize就是設計解析度
        director->_isStatusLabelUpdated = true;
        director->setGLDefaultValues();
    }
}

-----華麗分割線-----

小結：

直接了當，上來先說結果我的理解:

FrameSize:  

螢幕實際解析度，比如:常見的手機1920 * 1080，但是你的手機尺寸可以有5寸，可以有6.44寸等。。這個FrameSize和手機尺寸大小沒有關係，是固定的值。 所看到的螢幕尺寸也許是按照這個螢幕解析度進行放縮後的結果吧。

在win上或者mac模擬器上，這個調整完後，發現彈出的框大小有變化。

WinSize:  

設計解析度，就是你在setDesignResolution中傳遞的前2個引數的值得大小。

cocosstudio中畫布的大小其實是資源解析度，如: 在棋牌中的畫布大小，1280 * 720。在傳遞setDesignResolution值的時候，傳入的設計解析度的大小未必就等於Cocostudio中資源解析度的大小，這是為了後面的計算方便。

VisibleSize：

從原始碼可以看出，除非NO_BORDER情況下，否則，visibleSize大小就是等於winSize大小。因此為了計算方便，有時候傳遞進入setDesignResolution中前2個引數的值，會根據FrameSize也就是螢幕解析度適配後，傳遞一個根據資源解析度進行放縮的一個值，然後在第三個引數中傳遞NO_BORDER，這時，VisibleSize大小恰好就是帶黑邊的整個螢幕的大小，這樣方便計算。

因此要想拉伸背景圖，那麼

local Design = {
    width = 1280,
    height = 720,
}

self.schemeSize = cc.Director:getInstance():getVisibleSize()
self.showSize = Design

-- 背景圖會進行拉伸
function AdaptationScheme:setBg(bgNode)
	if not bgNode then
		gt.log("the params bgNode is err!!!")
		return
	end
	bgNode:setScaleX(self.schemeSize.width/self.showSize.width)
	bgNode:setScaleY(self.schemeSize.height/self.showSize.height)
end

然後根據螢幕寬高比:

function AdaptationScheme:getRatio()
	return FrameSize.width/FrameSize.height
end

因此，適配的原理總結為一句話:就是根據"螢幕解析度"，也就是FrameSize的寬高比的值，來決定到底採用哪種適配方式，從而決定setDesignResolution的第三個引數。其中setDesignResolution的前2個引數是設計解析度，也就是我們在CocosStudio中拼介面時，畫布的大小。

螢幕適配相關好文章：（不是特別強烈推薦！！！因為我覺得看別人分析容易誤解人，還是我上面自己分析的原始碼好撒!）

當然了，我覺得看這些文章不如看下cocos2dx原始碼來的直白，很清楚就有了自己的理解。所以原始碼之前了無祕密，有了疑惑的時候，看原始碼吧！！！