Method drawArrow

graph_view.cpp:850–863

}

void MyGraphicsLineItem::drawArrow(){
    QPointF leftEnd = QPointF(eP.x() - cos(angle - M_PI / 6) * arrowLength, eP.y() - sin(angle - M_PI / 6) * arrowLength);
    QPointF rightEnd = QPointF(eP.x() - cos(angle + M_PI / 6) * arrowLength, eP.y() - sin(angle + M_PI / 6) * arrowLength);

    QPainterPath arrowPath;
    arrowPath.moveTo(leftEnd);
    arrowPath.lineTo(eP);
    arrowPath.lineTo(rightEnd);

    QGraphicsPathItem* arrowItem = new QGraphicsPathItem(arrowPath);
    arrowItem->setPen(curPen);
    this->scene()->addItem(arrowItem);
    arrow = arrowItem;
}

void MyGraphicsLineItem::delArrow(){
    if(arrow != nullptr){