[Solved]et the size of the QGraphicsView

[stereomatching]

"The red rectangle":http://postimage.org/image/gqrf29mrh/

It is a QGraphicsView under a QMainWindow

@
graph_scene_ = new QGraphicsScene(this);
graph_scene_->addItem(graph_pixmap_ = new QGraphicsPixmapItem);
graph_view_ = new QGraphicsView(graph_scene_, this);

graph_view_->setDragMode(QGraphicsView::ScrollHandDrag);

setCentralWidget(graph_view_);

@

I only need the size of the area surrounded by the red rectangle but not the whole
area which could reach by the scrollBar.

[stereomatching]

I just find the answer, size() and viewport()->size()
whatevever, I need to find out the different of these
size.Thanks