how to use QwtplotCurve::fillcurve Fill area above baseline and below the curve

[lazy_learner]

something like http://www.halliburton.com/public/la...promaxvsp3.jpg

I have tried following code ,but it is not what I want

void QwtPlotCurveAnteo::fillCurve(QPainter *painter,
          const QwtScaleMap &xMap,
          const QwtScaleMap &yMap,
          const QRectF & canvasRect,
          QPolygonF & polygon) const
{
    painter->save();
    painter->setClipRect(xMap.transform(baseline()),0,100,1000,
                         Qt::ReplaceClip);
 
    QwtPlotCurve::fillCurve(painter, xMap, yMap, canvasRect, polygon);
 
    painter->setClipRect(xMap.transform(baseline()),0,100,1000,
                         Qt::NoClip);
    painter->restore();
 
    return;
}

void QwtPlotCurveAnteo::fillCurve(QPainter *painter,
          const QwtScaleMap &xMap,
          const QwtScaleMap &yMap,
          const QRectF & canvasRect,
          QPolygonF & polygon) const
{
    painter->save();
    painter->setClipRect(xMap.transform(baseline()),0,100,1000,
                         Qt::ReplaceClip);

    QwtPlotCurve::fillCurve(painter, xMap, yMap, canvasRect, polygon);

    painter->setClipRect(xMap.transform(baseline()),0,100,1000,
                         Qt::NoClip);
    painter->restore();

    return;
}

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