Curve seem not so clear when seBrush ?

[lwz]

When curve is setBrush , sections of the curve miss. The curve is not clear as before . Does anyone know how to solve this problem ?
Thanks


curve.jpg

[wysota]

What is missing?

[lwz]

Not missing , but it seems the part of the curve is covered by the brush area

[wysota]

Is it visible on your screenshot?

[lwz]

I can see some red . If the curve is set Width larger, I can see the whole curve. But it is thinner than others ,and many points in the curve on the brush side.


curve3.jpg

[wysota]

I'm sorry, I don't understand what you mean.

[Uwe]

But it is thinner than others ,and many points in the curve on the brush side.

The reason for this effect is obvious when looking at the implementation of QwtPlotCurve::drawLines: it draws the curve lines first before drawing the fill area in a second run. Interestingly this always been like this.

The code below inverts this drawing order, but be aware that it is not a complete replacement for all what needs to be done inside of QwtPlotCurve::drawLines. A fix that qualifies to be added to SVN has to take care of more use cases and of course should try to avoid wasting memory for having 2 temporary polygons for all points at the same time.

Uwe

class Curve: public QwtPlotCurve
{
public:
    Curve( const QString& title ):
        QwtPlotCurve( title )
    {
    }
 
protected:
    virtual void drawLines( QPainter *painter,
        const QwtScaleMap &xMap, const QwtScaleMap &yMap,
        const QRectF &canvasRect, int from, int to ) const
    {
        QwtPointMapper mapper;
        mapper.setBoundingRect( canvasRect );
 
        QPolygonF polyline = mapper.toPolygonF( xMap, yMap, data(), from, to );
 
        QPolygonF outline = polyline;
        fillCurve( painter, xMap, yMap, canvasRect, outline );
        QwtPainter::drawPolyline( painter, polyline );
    }
};

class Curve: public QwtPlotCurve
{
public:
    Curve( const QString& title ):
        QwtPlotCurve( title )
    {
    }

protected:
    virtual void drawLines( QPainter *painter,
        const QwtScaleMap &xMap, const QwtScaleMap &yMap,
        const QRectF &canvasRect, int from, int to ) const
    {
        QwtPointMapper mapper;
        mapper.setBoundingRect( canvasRect );

        QPolygonF polyline = mapper.toPolygonF( xMap, yMap, data(), from, to );

        QPolygonF outline = polyline;
        fillCurve( painter, xMap, yMap, canvasRect, outline );
        QwtPainter::drawPolyline( painter, polyline );
    }
};

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[lwz]

oh,I see, thanks