[osg]osg窗口显示和单屏幕显示

osg::ref_ptr<osg::Node> loadedModel = osgDB::readNodeFile("cow.osg");
 osg::ref_ptr<osgViewer::Viewer> viewer = new osgViewer::Viewer;
 {
  osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits;
  traits->x = 40;
  traits->y = 40;
  traits->width = 600;
  traits->height = 480;
  traits->windowDecoration = true;
  traits->doubleBuffer = true;
  traits->sharedContext = 0;

  osg::ref_ptr<osg::GraphicsContext> gc = osg::GraphicsContext::createGraphicsContext(traits.get());

  osg::ref_ptr<osg::Camera> camera = new osg::Camera;
  camera->setGraphicsContext(gc.get());
  camera->setViewport(new osg::Viewport(0,0, traits->width, traits->height));
  GLenum buffer = traits->doubleBuffer ? GL_BACK : GL_FRONT;
  camera->setDrawBuffer(buffer);
  camera->setReadBuffer(buffer);

  // add this slave camera to the viewer, with a shift left of the projection matrix
  viewer->addSlave(camera.get());
 }
 osgUtil::Optimizer optimizer;
 optimizer.optimize(loadedModel.get());
 viewer->setSceneData(loadedModel.get());

//viewer->setUpViewOnSingleScreen(0);//这里是单屏幕显示

 return viewer->run();