connect(_scene, SIGNAL(sceneRectChanged(const QRectF &)), this, SLOT(sceneRectChanged(const QRectF &)));
connect(_scene, SIGNAL(lastLineChanged(QGraphicsItem *, qreal)), this, SLOT(lastLineChanged(QGraphicsItem *, qreal)));
setScene(_scene);
connect(_scene, SIGNAL(sceneRectChanged(const QRectF &)), this, SLOT(sceneRectChanged(const QRectF &)));
connect(_scene, SIGNAL(lastLineChanged(QGraphicsItem *, qreal)), this, SLOT(lastLineChanged(QGraphicsItem *, qreal)));
setScene(_scene);