how to viewpoert size of frameSize save only the canvas not the scrollbars of QWidget

Qt Enthusiast

In continutaion with
https://forum.qt.io/topic/80540/how-to-save-the-pixmap-of-qwidget-without-borders-what-is-way-we-can-save-best-quality-image/6

In the following code

// view port is the only the QWidget- scrollbars
5111 QPixmap *pixmap = new QPixmap(viewport()->size());
5112 // QPixmap *pixmap = new QPixmap(this->frameSize());
5113 QPainter painter;
5114 painter.begin(pixmap);
5115 render(&painter);
5116 painter.end();
5117 pixmap->save(fileName);
5118 delete pixmap;
5119 }

or in following code
5111 QPixmap *pixmap = new QPixmap(this->frameSzie());
5112 // QPixmap *pixmap = new QPixmap(this->frameSize());
5113 QPainter painter;
5114 painter.begin(pixmap);
5115 render(&painter);
5116 painter.end();
5117 pixmap->save(fileName);
5118 delete pixmap;
5119 }

In this cases my QWidget saves only the visible part of QWidget without scrollbars . It will be helpful if some one can explain how

viewport()->size() and this->frameSzie() tells the painter to save only visible part of canvas without scrollbars