qwt_plot_curve.cpp

    if ( plot() == NULL || numSamples <= 0 )
        return -1;

    const QwtSeriesData<QPointF> *series = data();

    const QwtScaleMap xMap = plot()->canvasMap( xAxis() );
    const QwtScaleMap yMap = plot()->canvasMap( yAxis() );

    int index = -1;
    double dmin = 1.0e10;

    for ( uint i = 0; i < numSamples; i++ )
    {
        const QPointF sample = series->sample( i );

        const double cx = xMap.transform( sample.x() ) - pos.x();
        const double cy = yMap.transform( sample.y() ) - pos.y();

        const double f = qwtSqr( cx ) + qwtSqr( cy );
        if ( f < dmin )
        {
            index = i;
            dmin = f;
        }
    }
    if ( dist )
        *dist = qSqrt( dmin );

    return index;
}

/*!
   \return Icon representing the curve on the legend

   \param index Index of the legend entry 
                ( ignored as there is only one )
   \param size Icon size

   \sa QwtPlotItem::setLegendIconSize(), QwtPlotItem::legendData()
 */
QwtGraphic QwtPlotCurve::legendIcon( int index, 
    const QSizeF &size ) const
{
    Q_UNUSED( index );

    if ( size.isEmpty() )
        return QwtGraphic();

    QwtGraphic graphic;
    graphic.setDefaultSize( size );
    graphic.setRenderHint( QwtGraphic::RenderPensUnscaled, true );

    QPainter painter( &graphic );
    painter.setRenderHint( QPainter::Antialiasing,
        testRenderHint( QwtPlotItem::RenderAntialiased ) );

    if ( d_data->legendAttributes == 0 ||
        d_data->legendAttributes & QwtPlotCurve::LegendShowBrush )
    {
        QBrush brush = d_data->brush;

        if ( brush.style() == Qt::NoBrush &&
            d_data->legendAttributes == 0 )
        {
            if ( style() != QwtPlotCurve::NoCurve )
            {
                brush = QBrush( pen().color() );
            }
            else if ( d_data->symbol &&
                ( d_data->symbol->style() != QwtSymbol::NoSymbol ) )
            {
                brush = QBrush( d_data->symbol->pen().color() );
            }
        }

        if ( brush.style() != Qt::NoBrush )
        {
            QRectF r( 0, 0, size.width(), size.height() );
            painter.fillRect( r, brush );
        }
    }

    if ( d_data->legendAttributes & QwtPlotCurve::LegendShowLine )
    {
        if ( pen() != Qt::NoPen )
        {
            QPen pn = pen();
            pn.setCapStyle( Qt::FlatCap );

            painter.setPen( pn );

            const double y = 0.5 * size.height();
            QwtPainter::drawLine( &painter, 0.0, y, size.width(), y );
        }
    }

    if ( d_data->legendAttributes & QwtPlotCurve::LegendShowSymbol )
    {
        if ( d_data->symbol )
        {
            QRectF r( 0, 0, size.width(), size.height() );
            d_data->symbol->drawSymbol( &painter, r );
        }
    }

    return graphic;
}

/*!
  Initialize data with an array of points.

  \param samples Vector of points
  \note QVector is implicitly shared
  \note QPolygonF is derived from QVector<QPointF>
*/
void QwtPlotCurve::setSamples( const QVector<QPointF> &samples )
{
    setData( new QwtPointSeriesData( samples ) );
}

/*!
  Assign a series of points

  setSamples() is just a wrapper for setData() without any additional
  value - beside that it is easier to find for the developer.

  \param data Data
  \warning The item takes ownership of the data object, deleting
           it when its not used anymore.
*/
void QwtPlotCurve::setSamples( QwtSeriesData<QPointF> *data )
{
    setData( data );
}

#ifndef QWT_NO_COMPAT

/*!
  \brief Initialize the data by pointing to memory blocks which 
         are not managed by QwtPlotCurve.

  setRawSamples is provided for efficiency. 
  It is important to keep the pointers
  during the lifetime of the underlying QwtCPointerData class.

  \param xData pointer to x data
  \param yData pointer to y data
  \param size size of x and y

  \sa QwtCPointerData
*/
void QwtPlotCurve::setRawSamples( 
    const double *xData, const double *yData, int size )
{
    setData( new QwtCPointerData( xData, yData, size ) );
}

/*!
  Set data by copying x- and y-values from specified memory blocks.
  Contrary to setRawSamples(), this function makes a 'deep copy' of
  the data.

  \param xData pointer to x values
  \param yData pointer to y values
  \param size size of xData and yData

  \sa QwtPointArrayData
*/
void QwtPlotCurve::setSamples( 
    const double *xData, const double *yData, int size )
{
    setData( new QwtPointArrayData( xData, yData, size ) );
}

/*!
  \brief Initialize data with x- and y-arrays (explicitly shared)

  \param xData x data
  \param yData y data

  \sa QwtPointArrayData
*/
void QwtPlotCurve::setSamples( const QVector<double> &xData,
    const QVector<double> &yData )
{
    setData( new QwtPointArrayData( xData, yData ) );
}

#endif // !QWT_NO_COMPAT