callout.h Example File

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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