c – 在OpenGL / GLFW 3.2中切换窗口和全屏

#include <GL/gl.h>
#include <GLFW/glfw3.h>
#include <array>
#include <stdexcept>

class OpenGLWindow
{
private:

    std::array< int,2 > _wndPos         {0,0};
    std::array< int,2 > _wndSize        {0,2 > _vpSize         {0,0};
    bool                 _updateViewport = true;
    GLFWwindow *         _wnd            = nullptr;
    GLFWmonitor *        _monitor        = nullptr;

    void Resize( int cx,int cy );

public:

    void Init( int width,int height );
    static void CallbackResize(GLFWwindow* window,int cx,int cy);
    void MainLoop ( void );
    bool IsFullscreen( void );
    void SetFullScreen( bool fullscreen );
};

在创建窗口时,则将用户函数指针(glfwSetWindowUserPointer)设置为窗口管理类.调整大小的回调由glfwSetWindowSizeCallback设置.创建窗口后,可以通过glfwGetWindowPos和glfwGetWindowSize获取当前大小和位置.

void OpenGLWindow::Init( int width,int height )
{
    _wnd = glfwCreateWindow( width,"OGL window",nullptr,nullptr );
    if ( _wnd == nullptr )
    {
        glfwTerminate();
        throw std::runtime_error( "error initializing window" ); 
    }

    glfwMakeContextCurrent( _wnd );

    glfwSetWindowUserPointer( _wnd,this );
    glfwSetWindowSizeCallback( _wnd,OpenGLWindow::CallbackResize );

    _monitor =  glfwGetPrimaryMonitor();
    glfwGetWindowSize( _wnd,&_wndSize[0],&_wndSize[1] );
    glfwGetWindowPos( _wnd,&_wndPos[0],&_wndPos[1] );
    _updateViewport = true;
}

当调整大小通知发生时,可以通过glfwGetWindowUserPointer获取指向窗口管理类的指针：

static void OpenGLWindow::CallbackResize(GLFWwindow* window,int cy)
{
    void *ptr = glfwGetWindowUserPointer( window );
    if ( OpenGLWindow *wndPtr = static_cast<OpenGLWindow*>( ptr ) )
        wndPtr->Resize( cx,cy );
}

通知窗口大小的任何更改并存储新的窗口大小(glfwGetWindowSize)：

void OpenGLWindow::Resize( int cx,int cy )
{
    _updateViewport = true;
}

当窗口大小发生变化时,视口必须适合窗口大小(glViewport).这可以在应用程序的主循环中完成：

void OpenGLWindow::MainLoop ( void )
{
    while (!glfwWindowShouldClose(_wnd))
    {
        if ( _updateViewport )
        {
            glfwGetFramebufferSize( _wnd,&_vpSize[0],&_vpSize[1] );
            glViewport( 0,_vpSize[0],_vpSize[1] );
            _updateViewport = false;
        }

        // ..... render the scene

        glfwSwapBuffers(_wnd);
        glfwPollEvents();
    }
}

如果当前窗口处于全屏模式,可以通过询问窗口用于全屏模式的监视器(glfwGetWindowMonitor)来实现：

bool OpenGLWindow::IsFullscreen( void )
{
    return glfwGetWindowMonitor( _wnd ) != nullptr;
}

要打开和关闭全屏模式,必须使用全屏模式的监视器或使用nullptr调用glfwSetWindowMonitor：

void SetFullScreen( bool fullscreen )
{
    if ( IsFullscreen() == fullscreen )
    return;

    if ( fullscreen )
    {
        // backup windwo position and window size
        glfwGetWindowPos( _wnd,&_wndPos[1] );
        glfwGetWindowSize( _wnd,&_wndSize[1] );

        // get reolution of monitor
        const GLFWvidmode * mode = glfwGetVideoMode(glfwGetPrimaryMonitor());

        // swithc to full screen
        glfwSetWindowMonitor( _wnd,_monitor,mode->width,mode->height,0 );
    }
    else
    {
        // restore last window size and position
        glfwSetWindowMonitor( _wnd,_wndPos[0],_wndPos[1],_wndSize[0],_wndSize[1],0 );
    }

    _updateViewport = true;
}