Need to implement 2 grabbable cursors(markers)

I will be needing to implement 2 cursors (markers) in my graph. One should be able to grab
and move each of the 2 cursors with a deltaX, deltaY being displayed somewhere that
shows the difference between cursor1 and cursor 2.

This seems like functionality that someone would have already done, so before I start to reinvent the wheel, are there any examples of similar functionality out there?

If not any suggestions on how to best approach it?

Thank you.

Mark

Something like this ?

Code:

---

class DistancePicker : public QwtPlotPicker
{
public:
   DistancePicker( QwtPlotCanvas*);
 
protected:
   virtual void drawRubberBand(QPainter*) const;
   virtual QwtText trackerText(const QwtDoublePoint& pos) const;
};
 
DistancePicker::DistancePicker(QwtPlotCanvas* canvas):
   QwtPlotPicker(canvas),  
{    
   /*
      We don't have a picker for a line, but the rectangle
      selection is also selection of 2 points, so all we
      have to do is to change the rubberband.
    */
   setSelectionFlags(QwtPicker::RectSelection);
   setRubberBand(PolygonRubberBand);
   setTrackerMode(QwtPicker::ActiveOnly);
}  
 
void DistancePicker::drawRubberBand(QPainter *painter) const
{
   painter->drawPolygon(selection());
}  
 
QwtText DistancePicker::trackerText(const QwtDoublePoint &pos) const
{
   QwtText text( " selection() as distance string " );
 
   QColor bg(Qt::white);
   bg.setAlpha(180);
   text.setBackgroundBrush(QBrush(bg));
   return text;
}

---