def _mouseMoveEvent(e):
            if e.buttons() == Qt.MidButton:
                offset = self.previousMousePos - e.pos()
                self.previousMousePos = e.pos()

                self.view.verticalScrollBar().setValue(self.view.verticalScrollBar().value() + offset.y())
                self.view.horizontalScrollBar().setValue(self.view.horizontalScrollBar().value() + offset.x())
            else:
                QGraphicsView.mouseMoveEvent(self.view, e)

 def _mouseReleaseEvent(e):
     QGraphicsView.mouseReleaseEvent(self.view, e)
     self.view.viewport().setCursor(Qt.ArrowCursor)

 def _enterEvent(e):
     QGraphicsView.enterEvent(self.view, e)
     self.view.viewport().setCursor(Qt.ArrowCursor)

 def _mousePressEvent(e):
     if e.button() == Qt.MidButton:
         self.previousMousePos = e.pos()
     else:
         QGraphicsView.mousePressEvent(self.view, e)