GLView基本分析

GLView是cocos2d-x基于OpenGL ES的调用封装UI库。

OpenGL本身是跨平台的计算机图形实现API，在每一个平台的详细实现是不一样。所以每次使用之前先要初始化，去设置平台相关的信息。以下以win32的平台实现去分析：首先进入win32程序实现的入口文件：

bool AppDelegate::applicationDidFinishLaunching() {
    // initialize director
    auto director = Director::getInstance();
    auto glview = director->getOpenGLView();
    if(!glview) {
        glview = GLView::create("My Game"); //创建GL对象
        director->setOpenGLView(glview);
    }

    // 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::createScene();

    // run
    director->runWithScene(scene);

    return true;
}

GLView* GLView::create(const std::string& viewName)
{
    auto ret = new GLView;
    if(ret && ret->initWithRect(viewName, Rect(0, 0, 960, 640), 1)) {//3.2之后。win32的窗体应该实在这里改，Android和其它平台也有相似的文件文件
        ret->autorelease();
        return ret;
    }

    return nullptr;
}

设置GLView的初始化信息，比較有意思：

bool GLView::initWithRect(const std::string& viewName, Rect rect, float frameZoomFactor)
{
    setViewName(viewName);//窗体名字

    _frameZoomFactor = frameZoomFactor;//基础深度值。即Z轴

    glfwWindowHint(GLFW_RESIZABLE,GL_FALSE); //这句我也没看懂，求教

win32注冊窗体，这个就是真正的窗体。为什么之前说cocos2d的程序是单窗体单线程，这里是就明确了，我们仅仅使用单例Director，永远仅仅管理一个窗体

    _mainWindow = glfwCreateWindow(rect.size.width * _frameZoomFactor,
                                   rect.size.height * _frameZoomFactor,
                                   _viewName.c_str(),
                                   _monitor,
                                   nullptr);
    glfwMakeContextCurrent(_mainWindow);//设置为当前画布（Contex也有翻译为上下文、文本）

    glfwSetMouseButtonCallback(_mainWindow, GLFWEventHandler::onGLFWMouseCallBack);//鼠标的相关事件监听，在移动平台则应该是Touch began end 、focus（切换屏幕或应用会触发）
    glfwSetCursorPosCallback(_mainWindow, GLFWEventHandler::onGLFWMouseMoveCallBack);//拖动回调注冊
    glfwSetScrollCallback(_mainWindow, GLFWEventHandler::onGLFWMouseScrollCallback);//滚屏事件注冊，平时我们拖动TableView时就是由这个进行直接回调
    glfwSetCharCallback(_mainWindow, GLFWEventHandler::onGLFWCharCallback);//字符输入事件回调

</pre><pre code_snippet_id="498510" snippet_file_name="blog_20141027_8_222555" name="code" class="cpp"><pre name="code" class="cpp">/*

The key functions deal with physical keys, with layout independent
 *  [key tokens](@ref keys) named after their values in the standard US keyboard
 *  layout.  If you want to input text, use the
 *  [character callback](@ref glfwSetCharCallback) instead.
    glfwSetWindowPosCallback(_mainWindow, GLFWEventHandler::onGLFWWindowPosCallback);
    glfwSetFramebufferSizeCallback(_mainWindow, GLFWEventHandler::onGLFWframebuffersize);
    glfwSetWindowSizeCallback(_mainWindow, GLFWEventHandler::onGLFWWindowSizeFunCallback);

    setFrameSize(rect.size.width, rect.size.height);

*/

/*以上是原Api声明，实际意思：全部的物理键盘按键操作都会由这个触发，可是虚拟键盘的实现我还不清楚，应该是通过前面的MouseButton来之后调用CharCallback实现*/

glfwSetKeyCallback(_mainWindow, GLFWEventHandler::onGLFWKeyCallback);

glfwSetWindowPosCallback(_mainWindow, GLFWEventHandler::onGLFWWindowPosCallback); //屏幕拖动事件回调。在wp8和相关平台实现才须要
    glfwSetFramebufferSizeCallback(_mainWindow, GLFWEventHandler::onGLFWframebuffersize);//帧缓存大小设置？谁知道细节
    glfwSetWindowSizeCallback(_mainWindow, GLFWEventHandler::onGLFWWindowSizeFunCallback); //窗体大小的设置眼下在移动设备上是没有这个相关接口，win32和mac才有

// check OpenGL version at first
    const GLubyte* glVersion = glGetString(GL_VERSION);

    if ( utils::atof((const char*)glVersion) < 1.5 ) //opengl1.5以上兼容
    {
        char strComplain[256] = {0};
        sprintf(strComplain,
                "OpenGL 1.5 or higher is required (your version is %s). Please upgrade the driver of your video card.",
                glVersion);
        MessageBox(strComplain, "OpenGL version too old");
        return false;
    }

    initGlew();

    // Enable point size by default.
    glEnable(GL_VERTEX_PROGRAM_POINT_SIZE);

    return true;
}

跳转

// helper
bool GLView::initGlew()
{
#if (CC_TARGET_PLATFORM != CC_PLATFORM_MAC)
    GLenum GlewInitResult = glewInit();//OpenGL库固定初始化函数。

if (GLEW_OK != GlewInitResult)
    {
        MessageBox((char *)glewGetErrorString(GlewInitResult), "OpenGL error");
        return false;
    }

    if (GLEW_ARB_vertex_shader && GLEW_ARB_fragment_shader)
    {
        log("Ready for GLSL");
    }
    else
    {
        log("Not totally ready :(");
    }

    if (glewIsSupported("GL_VERSION_2_0"))
    {
        log("Ready for OpenGL 2.0");
    }
    else
    {
        log("OpenGL 2.0 not supported");
    }

#if (CC_TARGET_PLATFORM == CC_PLATFORM_WIN32)
    if(glew_dynamic_binding() == false) //OpenGL是一个单独的状态机。须要使用window OpenGL的api去完毕硬件绑定。

用设计模式的思想能够当做OpenGL是个策略模式中的策略。而window OpenGL则是提供策略支持详细实现。<span style="font-family: Arial, Helvetica, sans-serif;">window OpenGL</span><span style="font-family: Arial, Helvetica, sans-serif;">同一时候的代理（window os才是真正去管理硬件的总代理） wgl的细节我也不熟。就此搁置</span>
    {
        MessageBox("No OpenGL framebuffer support. Please upgrade the driver of your video card.", "OpenGL error");
        return false;
    }
#endif

#endif // (CC_TARGET_PLATFORM != CC_PLATFORM_MAC)

    return true;
}

#if (CC_TARGET_PLATFORM == CC_PLATFORM_WIN32)
static bool glew_dynamic_binding()
{
    const char *gl_extensions = (const char*)glGetString(GL_EXTENSIONS);

    // If the current opengl driver doesn't have framebuffers methods, check if an extension exists
    if (glGenFramebuffers == nullptr)
    {
        log("OpenGL: glGenFramebuffers is nullptr, try to detect an extension");
        if (strstr(gl_extensions, "ARB_framebuffer_object"))
        {
            log("OpenGL: ARB_framebuffer_object is supported");

            glIsRenderbuffer = (PFNGLISRENDERBUFFERPROC) wglGetProcAddress("glIsRenderbuffer");
            glBindRenderbuffer = (PFNGLBINDRENDERBUFFERPROC) wglGetProcAddress("glBindRenderbuffer");
            glDeleteRenderbuffers = (PFNGLDELETERENDERBUFFERSPROC) wglGetProcAddress("glDeleteRenderbuffers");
            glGenRenderbuffers = (PFNGLGENRENDERBUFFERSPROC) wglGetProcAddress("glGenRenderbuffers");
            glRenderbufferStorage = (PFNGLRENDERBUFFERSTORAGEPROC) wglGetProcAddress("glRenderbufferStorage");
            glGetRenderbufferParameteriv = (PFNGLGETRENDERBUFFERPARAMETERIVPROC) wglGetProcAddress("glGetRenderbufferParameteriv");
            glIsFramebuffer = (PFNGLISFRAMEBUFFERPROC) wglGetProcAddress("glIsFramebuffer");
            glBindFramebuffer = (PFNGLBINDFRAMEBUFFERPROC) wglGetProcAddress("glBindFramebuffer");
            glDeleteFramebuffers = (PFNGLDELETEFRAMEBUFFERSPROC) wglGetProcAddress("glDeleteFramebuffers");
            glGenFramebuffers = (PFNGLGENFRAMEBUFFERSPROC) wglGetProcAddress("glGenFramebuffers");
            glCheckFramebufferStatus = (PFNGLCHECKFRAMEBUFFERSTATUSPROC) wglGetProcAddress("glCheckFramebufferStatus");
            glFramebufferTexture1D = (PFNGLFRAMEBUFFERTEXTURE1DPROC) wglGetProcAddress("glFramebufferTexture1D");
            glFramebufferTexture2D = (PFNGLFRAMEBUFFERTEXTURE2DPROC) wglGetProcAddress("glFramebufferTexture2D");
            glFramebufferTexture3D = (PFNGLFRAMEBUFFERTEXTURE3DPROC) wglGetProcAddress("glFramebufferTexture3D");
            glFramebufferRenderbuffer = (PFNGLFRAMEBUFFERRENDERBUFFERPROC) wglGetProcAddress("glFramebufferRenderbuffer");
            glGetFramebufferAttachmentParameteriv = (PFNGLGETFRAMEBUFFERATTACHMENTPARAMETERIVPROC) wglGetProcAddress("glGetFramebufferAttachmentParameteriv");
            glGenerateMipmap = (PFNGLGENERATEMIPMAPPROC) wglGetProcAddress("glGenerateMipmap");
        }
        else
        if (strstr(gl_extensions, "EXT_framebuffer_object"))
        {
            log("OpenGL: EXT_framebuffer_object is supported");
            glIsRenderbuffer = (PFNGLISRENDERBUFFERPROC) wglGetProcAddress("glIsRenderbufferEXT");
            glBindRenderbuffer = (PFNGLBINDRENDERBUFFERPROC) wglGetProcAddress("glBindRenderbufferEXT");
            glDeleteRenderbuffers = (PFNGLDELETERENDERBUFFERSPROC) wglGetProcAddress("glDeleteRenderbuffersEXT");
            glGenRenderbuffers = (PFNGLGENRENDERBUFFERSPROC) wglGetProcAddress("glGenRenderbuffersEXT");
            glRenderbufferStorage = (PFNGLRENDERBUFFERSTORAGEPROC) wglGetProcAddress("glRenderbufferStorageEXT");
            glGetRenderbufferParameteriv = (PFNGLGETRENDERBUFFERPARAMETERIVPROC) wglGetProcAddress("glGetRenderbufferParameterivEXT");
            glIsFramebuffer = (PFNGLISFRAMEBUFFERPROC) wglGetProcAddress("glIsFramebufferEXT");
            glBindFramebuffer = (PFNGLBINDFRAMEBUFFERPROC) wglGetProcAddress("glBindFramebufferEXT");
            glDeleteFramebuffers = (PFNGLDELETEFRAMEBUFFERSPROC) wglGetProcAddress("glDeleteFramebuffersEXT");
            glGenFramebuffers = (PFNGLGENFRAMEBUFFERSPROC) wglGetProcAddress("glGenFramebuffersEXT");
            glCheckFramebufferStatus = (PFNGLCHECKFRAMEBUFFERSTATUSPROC) wglGetProcAddress("glCheckFramebufferStatusEXT");
            glFramebufferTexture1D = (PFNGLFRAMEBUFFERTEXTURE1DPROC) wglGetProcAddress("glFramebufferTexture1DEXT");
            glFramebufferTexture2D = (PFNGLFRAMEBUFFERTEXTURE2DPROC) wglGetProcAddress("glFramebufferTexture2DEXT");
            glFramebufferTexture3D = (PFNGLFRAMEBUFFERTEXTURE3DPROC) wglGetProcAddress("glFramebufferTexture3DEXT");
            glFramebufferRenderbuffer = (PFNGLFRAMEBUFFERRENDERBUFFERPROC) wglGetProcAddress("glFramebufferRenderbufferEXT");
            glGetFramebufferAttachmentParameteriv = (PFNGLGETFRAMEBUFFERATTACHMENTPARAMETERIVPROC) wglGetProcAddress("glGetFramebufferAttachmentParameterivEXT");
            glGenerateMipmap = (PFNGLGENERATEMIPMAPPROC) wglGetProcAddress("glGenerateMipmapEXT");
        }
        else
        {
            log("OpenGL: No framebuffers extension is supported");
            log("OpenGL: Any call to Fbo will crash!");
            return false;
        }
    }
    return true;
}
#endif