How to show xy coordinate on QLabel widget

[Astronomy]

Hi to Everyone,
i want the xy-coordinates too, but i want to save it to an integer or a double to display a Marker with a mouse click.
I had connected the Signal as UWE described and the signal is working. But i did not get the values, which are shown next to the mouse at the QwtPlot. e.g. (22000, 800). I only get from d_picker->trackerPosition() something like (139,81) which seem to be the pixel coordinates of the window.

My Question is:
How can i retrieve or transform the data "behind" the pixel-coordinates {like: (22000, 800) } ?
Or which additional Signal, must i connect to get the data which is displayed next to the mouse pointer?

thanks in advance,
Astronomy

here's my code:

CPlot::CPlot()  // constructor 
 
 // Crosslines of the mouse   - SELECTION
    d_picker = new QwtPlotPicker(QwtPlot::xBottom, QwtPlot::yLeft, QwtPicker::PointSelection | QwtPicker::DragSelection,
        QwtPlotPicker::CrossRubberBand, QwtPicker::AlwaysOn, this->canvas()); 
    d_picker->setRubberBandPen(QColor(Qt::green));
    d_picker->setRubberBand(QwtPicker::CrossRubberBand);
    connect(d_picker, SIGNAL(moved(const QPoint &)), SLOT(moved(const QPoint &)));
    connect(d_picker, SIGNAL(selected(const QwtPolygon &)), SLOT(selected(const QwtPolygon &)));
 //   connect(d_picker, SIGNAL(selected(const QwtDoublePoint &)), SLOT(selected(const QwtDoublePoint &)));
 
...[B] // as Uwe said..[/B]
 connect(d_picker, SIGNAL(selected(const QwtDoublePoint & )), SLOT(DrawMarkers()) );
...

CPlot::CPlot()  // constructor 

 // Crosslines of the mouse   - SELECTION
    d_picker = new QwtPlotPicker(QwtPlot::xBottom, QwtPlot::yLeft, QwtPicker::PointSelection | QwtPicker::DragSelection,
        QwtPlotPicker::CrossRubberBand, QwtPicker::AlwaysOn, this->canvas()); 
    d_picker->setRubberBandPen(QColor(Qt::green));
    d_picker->setRubberBand(QwtPicker::CrossRubberBand);
    connect(d_picker, SIGNAL(moved(const QPoint &)), SLOT(moved(const QPoint &)));
    connect(d_picker, SIGNAL(selected(const QwtPolygon &)), SLOT(selected(const QwtPolygon &)));
 //   connect(d_picker, SIGNAL(selected(const QwtDoublePoint &)), SLOT(selected(const QwtDoublePoint &)));

...[B] // as Uwe said..[/B]
 connect(d_picker, SIGNAL(selected(const QwtDoublePoint & )), SLOT(DrawMarkers()) );
...

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// My Signal of my QwtPlot derivation...

void CPlot::DrawMarkers()
{
    // Here the Markers for the selection will be placed on the plot..
    QwtPlotMarker *cSelectionMarker = new QwtPlotMarker();
    cSelectionMarker->setLabel(QString::fromLatin1("x-Selection"));
    cSelectionMarker->setLabelAlignment(Qt::AlignLeft | Qt::AlignBottom);
    cSelectionMarker->setLabelOrientation(Qt::Vertical);
    cSelectionMarker->setLineStyle(QwtPlotMarker::VLine);
    cSelectionMarker->setLinePen(QPen(Qt::red, 0, Qt::DashDotLine));
 
    int Test = 0;
  //  QwtDoublePoint pos;
    QPoint pos;    
    pos = d_picker->trackerPosition();
    test = pos.rx();                      // only for debugging: result was 139, seem to be the coordinates of the Window
    test = pos.ry();                         // debugging resultwas : 81  seem to be the coordinates of the Window
 
 
    test = d_picker->yAxis();  // debugging: result was 0, this comes from the constructor as a result of QwtPlot::yLeft
    test = d_picker->xAxis();     // debugging: result was 2, this comes from the constructor as a result of QwtPlot::xBottom
 
//d_picker->trackerText(pos);
 
 
    cSelectionMarker->setXValue( test ); //Set the Marker at mouseclick, not ok
   // cSelectionMarker->setXValue( 23000 ); //hardcoded Test, ok 
    cSelectionMarker->attach(this);
    replot();
}

void CPlot::DrawMarkers()
{
    // Here the Markers for the selection will be placed on the plot..
    QwtPlotMarker *cSelectionMarker = new QwtPlotMarker();
    cSelectionMarker->setLabel(QString::fromLatin1("x-Selection"));
    cSelectionMarker->setLabelAlignment(Qt::AlignLeft | Qt::AlignBottom);
    cSelectionMarker->setLabelOrientation(Qt::Vertical);
    cSelectionMarker->setLineStyle(QwtPlotMarker::VLine);
    cSelectionMarker->setLinePen(QPen(Qt::red, 0, Qt::DashDotLine));

    int Test = 0;
  //  QwtDoublePoint pos;
    QPoint pos;    
    pos = d_picker->trackerPosition();
    test = pos.rx();                      // only for debugging: result was 139, seem to be the coordinates of the Window
    test = pos.ry();                         // debugging resultwas : 81  seem to be the coordinates of the Window


    test = d_picker->yAxis();  // debugging: result was 0, this comes from the constructor as a result of QwtPlot::yLeft
    test = d_picker->xAxis();     // debugging: result was 2, this comes from the constructor as a result of QwtPlot::xBottom
   
//d_picker->trackerText(pos);


    cSelectionMarker->setXValue( test ); //Set the Marker at mouseclick, not ok
   // cSelectionMarker->setXValue( 23000 ); //hardcoded Test, ok 
    cSelectionMarker->attach(this);
    replot();
}

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