OSG 改變窗口大小

    viewer.realize();//需要realize，否則窗口為null
    osgViewer::GraphicsWindow *pWnd = dynamic_cast<osgViewer::GraphicsWindow*>(viewer.getCamera()->getGraphicsContext());
    if (pWnd) {
        pWnd->setWindowRectangle(20, 20, 600,600);

        pWnd->setWindowDecoration(true);
    }

在main函數中添加，在viewer.run()之前。