Sublcassing QwtPlotItem to customize its drawing behaviour

[corrado1972]

I don't know if my trouble is properly related to Qwt or widely to c++

How do I override draw method of an item (curve, marker) for customize its drawing behaviour ?

I tried with this code, but I can't take the control of overrided draw method, seems that compiler is ignoring it:

This is the code that is not working:

class train_evt_marker: public QwtPlotMarker
{
    public:
        train_evt_marker():QwtPlotMarker()
        {
            // here I see this log message
            QLOG_TRACE()<<"-------------constructor MARKER-------------";
        }
 
    void draw(QPainter *painter, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect)
    {
        // here I can't see the log messages... is this overrided method ignored??
        QLOG_TRACE()<<"-------------DRAw MARKER-------------";
        // calling the parent method continuing the draw of the curve
        QwtPlotMarker::draw(painter,xMap,yMap,canvasRect);
    }
};

class train_evt_marker: public QwtPlotMarker
{
    public:
        train_evt_marker():QwtPlotMarker()
        {
            // here I see this log message
            QLOG_TRACE()<<"-------------constructor MARKER-------------";
        }

    void draw(QPainter *painter, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect)
    {
        // here I can't see the log messages... is this overrided method ignored??
        QLOG_TRACE()<<"-------------DRAw MARKER-------------";
        // calling the parent method continuing the draw of the curve
        QwtPlotMarker::draw(painter,xMap,yMap,canvasRect);
    }
};

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TIA