qwt-6.0.2 subclassing QwtPlotCurve and reimpl. drawSymbols for rotated markers

Hello you all,
I'm using qwt 6.0.2 and I'm trying to draw rotated markers by a custom angle, tipically 30° counterclockwise.

Surfing the group, I found this thread in which is described how to plot custom markers/symbols: unfortunately doesn't work for me, because the signature of the method QwtPlotCurve::drawSymbols doesn't match with my version.
How do I solve this?

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Added after 57 minutes:

Actually I solved quick and dirty modifying directly QwtPlotMarker sources.

Addedo to .h:

Code:

---

void setLabelRotationAngle(double angle = 0.0);
...
private:
    double _rotationAngle;

---

Added to .cpp:

Code:

---

QwtPlotMarker::QwtPlotMarker():
    QwtPlotItem( QwtText( "Marker" ) ),
    _rotationAngle(0.0)
{
    d_data = new PrivateData;
    setZ( 30.0 );
}
.....
void QwtPlotMarker::setLabelRotationAngle(double angle)
{
    _rotationAngle = angle;
}

---

and into drawlabel method:

Code:

---

void QwtPlotMarker::drawLabel( QPainter *painter,
    const QRectF &canvasRect, const QPointF &pos ) const
{
.....
    if (_rotationAngle != 0.0){
        painter->setRenderHint(QPainter::Antialiasing);
        painter->rotate(_rotationAngle);
    }
const QRectF textRect( 0, 0, textSize.width(), textSize.height() );
    d_data->label.draw( painter, textRect );
}

---

the client side:

Code:

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marker->setLabel(QString::fromLatin1(QDateTime::fromTime_t(ge->timestamp).toString("hh:mm").toAscii()));
marker->setLabelOrientation(Qt::Horizontal);
marker->setLinePen(QPen(Qt::darkGray, 0, Qt::DotLine));
marker->setLineStyle(QwtPlotMarker::NoLine);
marker->setXValue(ge->timestamp);
marker->setYValue(d);
marker->setLabelAlignment(Qt::AlignCenter | Qt::AlignLeft);
// the tip:
marker->setLabelRotationAngle(-30.0);
 
curve->add_marker(marker);
marker->attach(this);

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the results: