如何添加十字准线QtChart带有签名值？

如何解决如何添加十字准线QtChart带有签名值？

任务： UPD有一个图表（QtChart）。代码：

from random import uniform
import sys

from PyQt5.QtWidgets import QApplication,QMainWindow,QVBoxLayout,QWidget
from PyQt5.QtChart import QChart,QChartView,QLineSeries

class Window(QMainWindow):
    def __init__(self):
        super().__init__()
        self.setGeometry(100,100,680,500)

        series = QLineSeries()
        for i in range(100):
            series.append(i,uniform(0,10))

        chart = QChart()
        chart.addSeries(series)
        chart.createDefaultAxes()
        chartview = QChartView(chart)

        central_widget = QWidget()
        self.setCentralWidget(central_widget)
        lay = QVBoxLayout(central_widget)
        lay.addWidget(chartview)
        self.setMouseTracking(True)

    def mouseMoveEvent(self,event):
        mouse_x = event.x()
        mouse_y = event.y()

if __name__ == "__main__":
    App = QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(App.exec_())

有必要： 将带有符号值的十字准线添加到图表（QtChart）。

目前是什么：

1. 通过示例How to return mouse coordinates in realtime?，可以了解如何获取鼠标坐标（更新代码）。
2. 很遗憾，我们没有取得任何进展。在图表文档（QT）中发现了一个具有类似功能https://doc.qt.io/qt-5/qtcharts-callout-example.html（不是您所需要的功能）的示例，但是主要问题是代码是用C ++编写的。

下面是C ++中的代码（如果有帮助的话）：

#include "callout.h"
#include <QtGui/QPainter>
#include <QtGui/QFontMetrics>
#include <QtWidgets/QGraphicsSceneMouseEvent>
#include <QtGui/QMouseEvent>
#include <QtCharts/QChart>

Callout::Callout(QChart *chart):
    QGraphicsItem(chart),m_chart(chart)
{
}

QRectF Callout::boundingRect() const
{
    QPointF anchor = mapFromParent(m_chart->mapToPosition(m_anchor));
    QRectF rect;
    rect.setLeft(qMin(m_rect.left()+20,anchor.x()));
    rect.setRight(qMax(m_rect.right(),anchor.x()));
    rect.setTop(qMin(m_rect.top(),anchor.y()));
    rect.setBottom(qMax(m_rect.bottom(),anchor.y()));
    return rect;
}

void Callout::paint(QPainter *painter,const QStyleOptionGraphicsItem *option,QWidget *widget)
{
    Q_UNUSED(option)
    Q_UNUSED(widget)
    QPainterPath path;
    path.addRoundedRect(m_rect,0);

    QPointF anchor = mapFromParent(m_chart->mapToPosition(m_anchor));
    if (!m_rect.contains(anchor)) {
        QPointF point1,point2;

        // establish the position of the anchor point in relation to m_rect
        bool above = anchor.y() <= m_rect.top();
        bool aboveCenter = anchor.y() > m_rect.top() && anchor.y() <= m_rect.center().y();
        bool belowCenter = anchor.y() > m_rect.center().y() && anchor.y() <= m_rect.bottom();
        bool below = anchor.y() > m_rect.bottom();

        bool onLeft = anchor.x() <= m_rect.left();
        bool leftOfCenter = anchor.x() > m_rect.left() && anchor.x() <= m_rect.center().x();
        bool rightOfCenter = anchor.x() > m_rect.center().x() && anchor.x() <= m_rect.right();
        bool onRight = anchor.x() > m_rect.right();

        // get the nearest m_rect corner.
        qreal x = (onRight + rightOfCenter) * m_rect.width();
        qreal y = (below + belowCenter) * m_rect.height();
        bool cornerCase = (above && onLeft) || (above && onRight) || (below && onLeft) || (below && onRight);
        bool vertical = qAbs(anchor.x() - x) > qAbs(anchor.y() - y);

        qreal x1 = x + leftOfCenter * 10 - rightOfCenter * 20 + cornerCase * !vertical * (onLeft * 10 - onRight * 20);
        qreal y1 = y + aboveCenter * 10 - belowCenter * 20 + cornerCase * vertical * (above * 10 - below * 20);;
        point1.setX(x1);
        point1.setY(y1);

        qreal x2 = x + leftOfCenter * 20 - rightOfCenter * 10 + cornerCase * !vertical * (onLeft * 20 - onRight * 10);;
        qreal y2 = y + aboveCenter * 20 - belowCenter * 10 + cornerCase * vertical * (above * 20 - below * 10);;
        point2.setX(x2);
        point2.setY(y2);

        path.moveTo(point1);
        path.lineTo(anchor);
        path.lineTo(point2);
        path = path.simplified();
    }
    painter->setBrush(QColor(255,255,255));
    painter->drawPath(path);
    painter->drawText(m_textRect,m_text);
}

void Callout::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
    event->setAccepted(true);
}

void Callout::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
    if (event->buttons() & Qt::LeftButton){
        setPos(mapToParent(event->pos() - event->buttonDownPos(Qt::LeftButton)));
        event->setAccepted(true);
    } else {
        event->setAccepted(false);
    }
}

void Callout::setText(const QString &text)
{
    m_text = text;
    QFontMetrics metrics(m_font);
    m_textRect = metrics.boundingRect(QRect(0,250,250),Qt::AlignLeft,m_text);
    m_textRect.translate(5,5);
    prepareGeometryChange();
    m_rect = m_textRect.adjusted(-5,-5,5,5);
}

void Callout::setAnchor(QPointF point)
{
    m_anchor = point;
}

void Callout::updateGeometry()
{
    prepareGeometryChange();
    setPos(m_chart->mapToPosition(m_anchor) + QPoint(10,-50));
}