overridden trackerTextF() being called mulitple time on mouse press down

I have created a subclass of the QwtPlotPicker (aka MyPlotPicker) and overridden the trackerTextF() function because I want it to display more than X/Y values. In my trackerTextF() function, all I do for the moment is print out the function name to the terminal using cout.

While the application is running, when I press the left mouse button down, my functions name appears in the terminal four times -- but I only expected to it to appear once.

I am guessing that for some reason the trackerTextF() function is being called four times, but I cannot figure out why that would be so. Is this by design? One thing I did notice is that if I change the picker machine from Drag to Click, my trackerTextF() function only gets called twice.

Here is my code...

Code:

---

class MyOtherPicker: public QwtPlotPicker
{
  public:
    MyOtherPicker(QwtPlotCanvas* pCanvas, Gui* pGui): QwtPlotPicker(QwtPlot::xBottom,
      QwtPlot::yLeft, QwtPlotPicker::CrossRubberBand, QwtPicker::ActiveOnly,
      pCanvas), mp_Gui(pGui)
    {
      setStateMachine(new QwtPickerClickPointMachine());
      setRubberBandPen(QColor(Qt::white));
    }
 
  protected:
    virtual QwtText trackerTextF(const QPointF &pos) const
    {
      cout << "trackerTextF" << endl;
      QwtText text;
      return text;
    }
 
  private:
    Gui* mp_Gui;
};

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