Pan GraphicsView

Pan GraphicsView

void WorkspaceView::mousePressEvent(QMouseEvent *event)
{
    Q_D(WorkspaceView);
    QGraphicsView::mousePressEvent(event);

    if (event->button()==Qt::MiddleButton) {
        d->m_lastPanPosition = event->pos();
        d->m_panning = true;
        setCursor(Qt::ClosedHandCursor);
    }
}

void WorkspaceView::mouseMoveEvent(QMouseEvent *event)
{
    Q_D(WorkspaceView);
    QGraphicsView::mouseMoveEvent(event);
    if(d->m_panning) {
        //Get how much we panned
        QPointF delta = mapToScene(d->m_lastPanPosition.toPoint()) - mapToScene(event->pos());
        d->m_lastPanPosition = event->pos();
        setCenter(center() + delta);
    }
}

void WorkspaceView::mouseReleaseEvent(QMouseEvent *event)
{
     Q_D(WorkspaceView);
    QGraphicsView::mouseReleaseEvent(event);
    if (d->m_panning) {
        setCursor(Qt::ArrowCursor);
        d->m_lastPanPosition = QPoint();
        d->m_panning = false;
    }
}

 void updateSceneRect()
    {
        Q_Q(WorkspaceScene);
        QRectF rect = q->itemsBoundingRect();
        const int width = rect.width();
        const int height = rect.height();
        rect.adjust(-width/2, -height/2 , width/2, height/2);
        q->setSceneRect(rect);
    }