如何在MFC应用程序中嵌入OpenGL渲染上下文

Question

我想在MFC MDI应用程序中嵌入OpenGL应用程序，即openscenegraph库。我已经创建了MFC应用程序作为标签式MDI文档，它从CView类派生MainForm和ChildForm，通常交换控件的窗口句柄和OpenGL渲染上下文（有一些初始化）足以让场景在控件中显示。我希望OpenGL场景位于子窗体内。

上述场景的问题是，首先我不知道从CView类派生MDI是否正确，或者不同的类更适合于此目的。其次，使用下面的代码m_hWnd总是返回零，因此无法初始化上下文。

   CChildFrame::CChildFrame()
{
    // TODO: add member initialization code here
    osgViewer::Viewer viewer;

    //osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits;
    RECT rect;
    HWND hw;    

    hw = m_hWnd;

    ::GetWindowRect(m_hWnd, &rect);

    osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits;

    // Init the Windata Variable that holds the handle for the Window to display OSG in.
    osg::ref_ptr<osg::Referenced> windata = new osgViewer::GraphicsWindowWin32::WindowData(m_hWnd);

    // Setup the traits parameters
    traits->x = 0;
    traits->y = 0;
    traits->width = rect.right - rect.left;
    traits->height = rect.bottom - rect.top;
    traits->windowDecoration = false;
    traits->doubleBuffer = true;
    traits->sharedContext = 0;
    traits->setInheritedWindowPixelFormat = true;
    traits->inheritedWindowData = windata;

    // Create the Graphics Context
    osg::GraphicsContext* gc = osg::GraphicsContext::createGraphicsContext(traits.get());

    // Init a new Camera (Master for this View)
    osg::ref_ptr<osg::Camera> camera = new osg::Camera;

    // Assign Graphics Context to the Camera
    camera->setGraphicsContext(gc);

    // Set the viewport for the Camera
    camera->setViewport(new osg::Viewport(traits->x, traits->y, traits->width, traits->height));

    // Set projection matrix and camera attribtues
    camera->setClearMask(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
    camera->setClearColor(osg::Vec4f(0.2f, 0.2f, 0.4f, 1.0f));
    camera->setProjectionMatrixAsPerspective(
        30.0f, static_cast<double>(traits->width) / static_cast<double>(traits->height), 1.0, 1000.0);

    // Add the Camera to the Viewer
    //mViewer->addSlave(camera.get());
    viewer.setCamera(camera.get());

    // Add the Camera Manipulator to the Viewer
    viewer.setCameraManipulator(new osgGA::OrbitManipulator());

    osg::ref_ptr<osg::Group> root = new osg::Group;
    osg::ref_ptr<osg::Geode> geode = new osg::Geode;
    geode->addDrawable(new osg::ShapeDrawable(new osg::Box(osg::Vec3(0.0f, 0.0f, -0.5f), 100.0f, 100.0f, 1.0f)));

    root->addChild(geode.get());

    viewer.setSceneData(root.get());
    viewer.realize();
}