How to take a full page screenshot?

yetanotherqtfan

The following code can be used in a QWebEngineView based class to take a screenshot into an image:
QSize size=page()->contentsSize().toSize();
QImage image(size, QImage::Format_ARGB32);
QPainter painter(&image);
render(&painter);

However, only part of the web page(that is shown on the view widget) is captured. In QtWebkit, I can use setViewPort to capture the whole page but QWebEngineView does not have this function. How can I capture the entire web page now?

Thanks!