QChart 鼠标移动到曲线上，显示曲线的点（已封装成dll）// Qtooltip

本文链接：https://blog.youkuaiyun.com/a1ngel/article/details/104049848

本文介绍如何从QtCharts官方示例中封装Callout组件，包括代码实现、绘图和布局调整。提供了.cpp文件中的关键函数，如boundingRect、paint、setText、setAnchor等，以及如何设置颜色和更新几何形状。

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1、准备工作

该封装案例取自Qt chart的官方示例。

找到官方列子

如果安装了qt examples，路径如下图：

如果未安装examples，访问官方网址：https://doc.qt.io/qt-5/qtcharts-callout-example.html

2、开始封装有效代码

这边不研究源码，请自行测试，下面贴出所有代码

.cpp中

//.cpp
//虚函数获取区域大小
QRectF QCallout::boundingRect() const
{
   QPointF anchor = mapFromParent(m_chart->mapToPosition(m_anchor));
   QRectF rect;
   rect.setLeft(qMin(m_rect.left(), 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;
}
//重绘
void QCallout::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
   Q_UNUSED(option)
       Q_UNUSED(widget)
       QPainterPath path;
   path.addRoundedRect(m_rect, 5, 5); //将圆角矩形加入路径

   QPointF anchor = mapFromParent(m_chart->mapToPosition(m_anchor));//返回图列的相对位置
   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(rectColor);
   painter->drawPath(path);
   painter->setPen(textColor);
   painter->setFont(m_font);
   painter->drawText(m_textRect, m_text);

   // qDebug()<<"已经进入 paint";
}
void QCallout::setText(QString text)
{
   m_text = text;
   QFontMetrics metrics(m_font); //获取文字的宽带等
   m_font.setPointSize(15);
   m_textRect = metrics.boundingRect(QRect(0, 0, 150, 150), Qt::AlignLeft, m_text);// 返回一个边界矩形。
   m_textRect.translate(5, 5);//移动距离
   prepareGeometryChange();
   m_rect = m_textRect.adjusted(-5, -5, 5, 5);//将现有的坐标加入坐标系中。

}
//设置点击点
void QCallout::setAnchor(QPointF point)
{
   m_anchor = point;
}
//更新绘图
void QCallout::updateGeometry()
{
   prepareGeometryChange();
   setPos(m_chart->mapToPosition(m_anchor) + QPoint(10, -50));
}
//设置颜色
void QCallout::setRectColor(QColor c1, QColor c2, int num)
{
   textColor = c1;
   rectColor = c2;
   fontSize = num;
}