cocos2d-x 3.0 分辨率自适应方案
1. 简介
对于cocos2dx的分辨率方案原来一知半解，终于今天有机会给搞清楚了。在cocos2d-x中的几种分辨率：
1.1 Framebuffer分辨率（其大小依赖于硬件设备）
保存在EGLViewProtocol类的Size _screenSize;
在nativeactivity.cpp的cocos_init中调用setFrameSize设置Framebuffer大小，Framebuffer大小在engine_init_display中调用以下代码获取：
EGLint w, h;
eglQuerySurface(display, surface, EGL_WIDTH, &w);
eglQuerySurface(display, surface, EGL_HEIGHT, &h);
获取方式：
EGLView::getInstance()->getFrameSize();
1.2 设计分辨率（其大小依赖于游戏设计人员，与硬件设备无关）
游戏UI设计人员或程序人员都是基于此尺寸进行设计。
获取方式：
（1）游戏设计窗口大小：Director::getInstance()->getVisibleSize(); //实际从EGLView中获取
（2）游戏设计窗口原点：Director::getInstance()->getVisibleOrigin(); //实际从EGView中获取
2. 分辨率自适应
分辨率自适应：即把设计好的游戏以全屏方式(但背景图片不一定能全部显示出来)显示在目标设备上，以给用户最好的体验。
可以通过EGLView::getInstance()->setDesignResolutionSize(float width, float height, ResolutionPolicy resolutionPolicy)来告诉cocos2d-x 3.0游戏设计分辨率，然后cocos2d-x 3.0将自动根据设置的resolutionPolicy进行scale，以实现全屏显示。
其参考代码及相关log如下所示：
#define DESIGN_WIDTH 1280
#define DESIGN_HEIGHT 800
bool AppDelegate::applicationDidFinishLaunching() {
// initialize director
auto director = Director::getInstance();
auto eglView = EGLView::getInstance();
director->setOpenGLView(eglView);
// 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);
// resolution information
Size size;
size= director->getWinSize();
log("***IDONG: Director getWinSize:w=%f,h=%f",size.width,size.height);
size = director->getWinSizeInPixels();
log("***IDONG: Director getWinSizeInPixels:w=%f,h=%f",size.width,size.height);
size = director->getVisibleSize();
log("***IDONG: Director getVisibleSize:w=%f,h=%f",size.width,size.height);
Point point = director->getVisibleOrigin();
log("***IDONG: Director getVisibleOrigin:x=%f,y=%f",point.x,point.y);
log("***IDONG: Director BS: getContentScaleFactor: scaleFactor=%f",director->getContentScaleFactor());
// set design resolution size
eglView->setDesignResolutionSize(DESIGN_WIDTH,DESIGN_HEIGHT,ResolutionPolicy::NO_BORDER);
log("***IDONG:\n");
log("***IDONG: Director AS: getContentScaleFactor: scaleFactor=%f",director->getContentScaleFactor());
size= director->getWinSize();
log("***IDONG: Director getWinSize:w=%f,h=%f",size.width,size.height);
size = director->getWinSizeInPixels();
log("***IDONG: Director getWinSizeInPixels:w=%f,h=%f",size.width,size.height);
size = director->getVisibleSize();
log("***IDONG: Director getVisibleSize:w=%f,h=%f",size.width,size.height);
point = director->getVisibleOrigin();
log("***IDONG: Director getVisibleOrigin:x=%f,y=%f",point.x,point.y);
// create a scene. it's an autorelease object
auto scene = StartLayer::createScene();
// run
director->runWithScene(scene);
return true;
}
相关log信息：
Director getWinSize:w=1920.000000,h=1032.000000 Director getWinSizeInPixels:w=1920.000000,h=1032.000000 Director getVisibleSize:w=1920.000000,h=1032.000000 Director getVisibleOrigin:x=0.000000,y=0.000000 Director BS: getContentScaleFactor: scaleFactor=1.000000 Director AS: getContentScaleFactor: scaleFactor=1.000000 Director getWinSize:w=1280.000000,h=800.000000 Director getWinSizeInPixels:w=1280.000000,h=800.000000 Director getVisibleSize:w=1280.000000,h=688.000000 Director getVisibleOrigin:x=0.000000,y=56.000000
2.1 显示规则
1) 游戏背景画面不一定能全部显示，但关键部分必须显示，所以在背景画面上的四周不要放置重要信息
2) 游戏元素必须全部显示，且其位置基于Director::getVisibleSize和Director::getVisibleOrigin 来进行放置，如需要把一个sprite放置于屏幕中央，其代码可以为：
Size visibleSize = Director::getInstance()->getVisibleSize();
Point origin = Director::getInstance()->getVisibleOrigin();
//////////////////////////////
// 2. add background
//auto sprite = Sprite::create("map_logo_ocean_001_sx.jpg",Rect(0,168,visibleSize.width,visibleSize.height));
auto sprite = Sprite::create("map_logo_ocean_001_sx.jpg");
// position the sprite on the center of the screen
sprite->setPosition(Point(visibleSize.width/2 + origin.x, visibleSize.height/2 + origin.y));
// add the sprite as a child to this layer
this->addChild(sprite, 0);