Draw line in PolarPlot

[juancaa]

Hi! Ive been trying to implement some code to draw a line from the origin to a given point in a polar plot but I couldnt do it, is there someone who can help me or give me some tips?

Thanks!

[Uwe]

IMO QwtPolarMarker should be extended to offer to draw a line to the origin - but for the moment you have to use QwtPolarCurve ( with 2 points ) for this.
Alternatively you could overload QwtPolarMarker::draw like this:

void YourPolarMarker::draw( QPainter *painter,
    const QwtScaleMap &azimuthMap, const QwtScaleMap &radialMap,
    const QPointF &pole, double radius,
    const QRectF &canvasRect ) const
{
    const double r = radialMap.transform( position().radius() );
    const double a = azimuthMap.transform( position().azimuth() );
 
    const QPointF pos = qwtPolar2Pos( pole, r, a );
 
    painter->setPen( ... );
    painter->drawLine( pole, pos );
 
    QwtPolarMarker::draw( painter, ... );
}

void YourPolarMarker::draw( QPainter *painter,
    const QwtScaleMap &azimuthMap, const QwtScaleMap &radialMap,
    const QPointF &pole, double radius,
    const QRectF &canvasRect ) const
{
    const double r = radialMap.transform( position().radius() );
    const double a = azimuthMap.transform( position().azimuth() );

    const QPointF pos = qwtPolar2Pos( pole, r, a );

    painter->setPen( ... );
    painter->drawLine( pole, pos );

    QwtPolarMarker::draw( painter, ... );
}

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Uwe