qwt_plot_curve.cpp

    }

    polyline = ::clipPolygon(painter, d_data->paintAttributes, polyline);

    QwtPainter::drawPolyline(painter, polyline);

    if ( d_data->brush.style() != Qt::NoBrush )
        fillCurve(painter, xMap, yMap, polyline);
}


/*!
  \brief Specify an attribute for drawing the curve

  The attributes can be used to modify the drawing style.
  The following attributes are defined:<dl>
  <dt>Fitted</dt>
  <dd>For Lines only. A QwtCurveFitter tries to
      interpolate/smooth the curve, before it is painted.
      Note that curve fitting requires temorary memory
      for calculating coefficients and additional points.
      If painting in Fitted mode is slow it might be better
      to fit the points, before they are passed to QwtPlotCurve.
  </dd>
  <dt>Inverted</dt>
  <dd>For Steps only. Draws a step function
      from the right to the left.</dd></dl>

  \param attribute Curve attribute
  \param on On/Off

  /sa testCurveAttribute(), setCurveFitter()
*/
void QwtPlotCurve::setCurveAttribute(CurveAttribute attribute, bool on)
{
    if ( bool(d_data->attributes & attribute) == on )
        return;

    if ( on )
        d_data->attributes |= attribute;
    else
        d_data->attributes &= ~attribute;

    itemChanged();
}

/*!
    \return true, if attribute is enabled
    \sa setCurveAttribute()
*/
bool QwtPlotCurve::testCurveAttribute(CurveAttribute attribute) const
{
    return d_data->attributes & attribute;
}

/*!
  Assign the curve type

  <dt>QwtPlotCurve::Yfx
  <dd>Draws y as a function of x (the default). The
      baseline is interpreted as a horizontal line
      with y = baseline().</dd>
  <dt>QwtPlotCurve::Xfy
  <dd>Draws x as a function of y. The baseline is
      interpreted as a vertical line with x = baseline().</dd>

  The baseline is used for aligning the sticks, or
  filling the curve with a brush.

  \sa curveType()
*/
void QwtPlotCurve::setCurveType(CurveType curveType)
{
    if ( d_data->curveType != curveType ) {
        d_data->curveType = curveType;
        itemChanged();
    }
}

/*!
   Return the curve type
   \sa setCurveType()
*/
QwtPlotCurve::CurveType QwtPlotCurve::curveType() const
{
    return d_data->curveType;
}

void QwtPlotCurve::setCurveFitter(QwtCurveFitter *curveFitter)
{
    delete d_data->curveFitter;
    d_data->curveFitter = curveFitter;

    itemChanged();
}

QwtCurveFitter *QwtPlotCurve::curveFitter() const
{
    return d_data->curveFitter;
}

/*!
  Fill the area between the curve and the baseline with
  the curve brush

  \param painter Painter
  \param xMap x map
  \param yMap y map
  \param pa Polygon

  \sa setBrush(), setBaseline(), setCurveType()
*/

void QwtPlotCurve::fillCurve(QPainter *painter,
                             const QwtScaleMap &xMap, const QwtScaleMap &yMap,
                             QwtPolygon &pa) const
{
    if ( d_data->brush.style() == Qt::NoBrush )
        return;

    closePolyline(xMap, yMap, pa);
    if ( pa.count() <= 2 ) // a line can't be filled
        return;

    QBrush b = d_data->brush;
    if ( !b.color().isValid() )
        b.setColor(d_data->pen.color());

    painter->save();

    painter->setPen(QPen(Qt::NoPen));
    painter->setBrush(b);

    QwtPainter::drawPolygon(painter, pa);

    painter->restore();
}

/*!
  \brief Complete a polygon to be a closed polygon
         including the area between the original polygon
         and the baseline.
  \param xMap X map
  \param yMap Y map
  \param pa Polygon to be completed
*/

void QwtPlotCurve::closePolyline(
    const QwtScaleMap &xMap, const QwtScaleMap &yMap,
    QwtPolygon &pa) const
{
    const int sz = pa.size();
    if ( sz < 2 )
        return;

    pa.resize(sz + 2);

    if ( d_data->curveType == QwtPlotCurve::Xfy ) {
        pa.setPoint(sz,
                    xMap.transform(d_data->reference), pa.point(sz - 1).y());
        pa.setPoint(sz + 1,
                    xMap.transform(d_data->reference), pa.point(0).y());
    } else {
        pa.setPoint(sz,
                    pa.point(sz - 1).x(), yMap.transform(d_data->reference));
        pa.setPoint(pa.size() - 1,
                    pa.point(0).x(), yMap.transform(d_data->reference));
    }
}

/*!
  \brief Draw symbols
  \param painter Painter
  \param symbol Curve symbol
  \param xMap x map
  \param yMap y map
  \param from index of the first point to be painted
  \param to index of the last point to be painted

  \sa setSymbol(), draw(), drawCurve()
*/
void QwtPlotCurve::drawSymbols(QPainter *painter, const QwtSymbol &symbol,
                               const QwtScaleMap &xMap, const QwtScaleMap &yMap,
                               int from, int to) const
{
    painter->setBrush(symbol.brush());

    const QwtMetricsMap &metricsMap = QwtPainter::metricsMap();

    QPen pen = symbol.pen();

#if SCALE_PEN
    if ( pen.width() > 0 )
        pen.setWidth(metricsMap.screenToLayoutX(pen.width()));
#endif

    painter->setPen(pen);

    QRect rect;
    rect.setSize(metricsMap.screenToLayout(symbol.size()));

    if ( to > from && d_data->paintAttributes & PaintFiltered ) {
        const QRect window = painter->window();
        if ( window.isEmpty() )
            return;

        PrivateData::PixelMatrix pixelMatrix(window);

        for (int i = from; i <= to; i++) {
            const QPoint pi( xMap.transform(x(i)),
                             yMap.transform(y(i)) );

            if ( pixelMatrix.testPixel(pi) ) {
                rect.moveCenter(pi);
                symbol.draw(painter, rect);
            }
        }
    } else {
        for (int i = from; i <= to; i++) {
            const int xi = xMap.transform(x(i));
            const int yi = yMap.transform(y(i));

            rect.moveCenter(QPoint(xi, yi));
            symbol.draw(painter, rect);
        }
    }
}

/*!
  \brief Set the value of the baseline

  The baseline is needed for filling the curve with a brush or
  the Sticks drawing style.
  The default value is 0.0. The interpretation
  of the baseline depends on the CurveType. With QwtPlotCurve::Yfx,
  the baseline is interpreted as a horizontal line at y = baseline(),
  with QwtPlotCurve::Yfy, it is interpreted as a vertical line at
  x = baseline().
  \param reference baseline
  \sa baseline(), setBrush(), setStyle(), setCurveType()
*/
void QwtPlotCurve::setBaseline(double reference)
{
    if ( d_data->reference != reference ) {
        d_data->reference = reference;
        itemChanged();
    }
}

/*!
    Return the value of the baseline
    \sa setBaseline
*/
double QwtPlotCurve::baseline() const
{
    return d_data->reference;
}

/*!
  Return the size of the data arrays
  \sa setData()
*/
int QwtPlotCurve::dataSize() const
{
    return d_xy->size();
}

int QwtPlotCurve::closestPoint(const QPoint &pos, double *dist) const
{
    if ( plot() == NULL || dataSize() <= 0 )
        return -1;

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

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

    for (int i=0; i < dataSize(); i++) {
        const double cx = xMap.xTransform(x(i)) - pos.x();
        const double cy = yMap.xTransform(y(i)) - pos.y();

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

    return index;
}

//!  Update the widget that represents the curve on the legend
void QwtPlotCurve::updateLegend(QwtLegend *legend) const
{
    if ( !legend )
        return;

    QwtPlotItem::updateLegend(legend);

    QWidget *widget = legend->find(this);
    if ( !widget || !widget->inherits("QwtLegendItem") )
        return;

    QwtLegendItem *legendItem = (QwtLegendItem *)widget;

#if QT_VERSION < 0x040000
    const bool doUpdate = legendItem->isUpdatesEnabled();
#else
    const bool doUpdate = legendItem->updatesEnabled();
#endif
    legendItem->setUpdatesEnabled(false);

    const int policy = legend->displayPolicy();

    if (policy == QwtLegend::FixedIdentifier) {
        int mode = legend->identifierMode();

        if (mode & QwtLegendItem::ShowLine)
            legendItem->setCurvePen(pen());

        if (mode & QwtLegendItem::ShowSymbol)
            legendItem->setSymbol(symbol());

        if (mode & QwtLegendItem::ShowText)
            legendItem->setText(title());
        else
            legendItem->setText(QwtText());

        legendItem->setIdentifierMode(mode);
    } else if (policy == QwtLegend::AutoIdentifier) {
        int mode = 0;

        if (QwtPlotCurve::NoCurve != style()) {
            legendItem->setCurvePen(pen());
            mode |= QwtLegendItem::ShowLine;
        }
        if (QwtSymbol::NoSymbol != symbol().style()) {
            legendItem->setSymbol(symbol());
            mode |= QwtLegendItem::ShowSymbol;
        }
        if ( !title().isEmpty() ) {
            legendItem->setText(title());
            mode |= QwtLegendItem::ShowText;
        } else {
            legendItem->setText(QwtText());
        }
        legendItem->setIdentifierMode(mode);
    }

    legendItem->setUpdatesEnabled(doUpdate);
    legendItem->update();
}