class ProjectView : public QGraphicsView {
    Q_OBJECT

public:
    ProjectView(QWidget* parent = 0);
    ~ProjectView();

    QPointF m_lastPointF;
    bool isPressed;

protected:
    void mousePressEvent(QMouseEvent *event);
    void mouseMoveEvent(QMouseEvent* mouseEvent);
    void mouseReleaseEvent(QMouseEvent* mouseEvent);
};

ProjectView::ProjectView(QWidget* parent)
    : QGraphicsView(parent)
{
    this->setMouseTracking(true);

    this->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    this->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    this->verticalScrollBar()->blockSignals(true);
    this->horizontalScrollBar()->blockSignals(true);

    this->horizontalScrollBar()->setEnabled(false);
    this->verticalScrollBar()->setEnabled(false);
    this->verticalScrollBar()->setValue(this->verticalScrollBar()->minimum());
    this->horizontalScrollBar()->setValue(this->horizontalScrollBar()->minimum());

    this->setViewportUpdateMode(QGraphicsView::FullViewportUpdate);
    this->setDragMode(QGraphicsView::RubberBandDrag);
    this->setRubberBandSelectionMode(Qt::ContainsItemBoundingRect);
    this->setAcceptDrops(true);
}
ProjectView::~ProjectView()
{
    //qDebug()<<__FUNCTION__;
}

void ProjectView::mousePressEvent(QMouseEvent* mouseEvent)
{
    m_lastPointF = mouseEvent->pos();
    isPressed = true;

    QGraphicsView::mousePressEvent(mouseEvent);
}

void ProjectView::mouseMoveEvent(QMouseEvent* mouseEvent)
{
    if (isPressed ) {
        QPointF disPointF = mouseEvent->pos() - m_lastPointF;
        m_lastPointF = mouseEvent->pos();
        this->scene()->setSceneRect(this->scene()->sceneRect().x() - disPointF.x(),
            this->scene()->sceneRect().y() - disPointF.y(),
            this->scene()->sceneRect().width(),
            this->scene()->sceneRect().height());
        this->scene()->update();
    }
    
    QGraphicsView::mouseMoveEvent(mouseEvent);
}

void ProjectView::mouseReleaseEvent(QMouseEvent* mouseEvent)
{
    if (isPressed) {
        isPressed = false;
    }

    QGraphicsView::mouseReleaseEvent(mouseEvent);
}