that's really strange.

you could try to change the declaration, but I don't think that'll make a difference:
Qt Code: 
  1. PlotPicker *d_picker;//<-----
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this is my initialization:
Qt Code: 
  1. d_picker = new PlotPicker (QwtPlot::xBottom, QwtPlot::yLeft, QwtPicker::PointSelection | QwtPicker::DragSelection, QwtPlotPicker::NoRubberBand, QwtPicker::AlwaysOn, plot->canvas());
  2.     d_picker->setTrackerPen(QColor(Qt::darkGreen));
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and my constructor is empty:
Qt Code: 
  1. PlotPicker ::PlotPicker (int xAxis, int yAxis, int selectionFlags, RubberBand rubberBand, DisplayMode trackerMode, QwtPlotCanvas* canvas)
  2. : QwtPlotPicker(xAxis, yAxis, selectionFlags, rubberBand, trackerMode, canvas)
  3.   {
  4.   }
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and my trackerText is declared "protected" instead of "private", but that definitively does not make a difference (I checked that)