callout.h Example File

callout/callout.h
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 #ifndef CALLOUT_H
 #define CALLOUT_H

 #include <QtCharts/QChartGlobal>
 #include <QtWidgets/QGraphicsItem>
 #include <QtGui/QFont>

 class QGraphicsSceneMouseEvent;

 QT_CHARTS_BEGIN_NAMESPACE
 class QChart;
 QT_CHARTS_END_NAMESPACE

 QT_CHARTS_USE_NAMESPACE

 class Callout : public QGraphicsItem
 {
 public:
     Callout(QChart *parent);

     void setText(const QString &text);
     void setAnchor(QPointF point);
     void updateGeometry();

     QRectF boundingRect() const;
     void paint(QPainter *painter, const QStyleOptionGraphicsItem *option,QWidget *widget);

 protected:
     void mousePressEvent(QGraphicsSceneMouseEvent *event);
     void mouseMoveEvent(QGraphicsSceneMouseEvent *event);

 private:
     QString m_text;
     QRectF m_textRect;
     QRectF m_rect;
     QPointF m_anchor;
     QFont m_font;
     QChart *m_chart;
 };

 #endif // CALLOUT_H