OSG 改变窗口大小

     viewer.realize();//需要realize，否则窗口为null
     osgViewer::GraphicsWindow *pWnd = dynamic_cast<osgViewer::GraphicsWindow*>(viewer.getCamera()->getGraphicsContext());
     if (pWnd) {
         pWnd->setWindowRectangle(, , ,);

         pWnd->setWindowDecoration(true);
     }

在main函数中添加，在viewer.run()之前。