qwtplotdirectpainter don´t use penwidth of the curve

[aker]

Hello!

This is my first post to this forum. I usually allways find here a solution to my problem, but in this case I don´t...
I have an Application which uses qwt 6.1.0. I realized a real-time-plot based on the realtime and oscilloscope example. I have now 2 or more realtime curves in the plot and paint this to the canvas by QwtPlotDirectPainter.
One curve I want to display in different penwidth. The penwidth is working when I do a replot of the plot, but then I have a performance problem.
Can I set a penwidth so the directpainter paint the curve thicker??

Andre

[Uwe]

One curve I want to display in different penwidth. The penwidth is working when I do a replot of the plot, but then I have a performance problem.
Can I set a penwidth so the directpainter paint the curve thicker?

QwtPlotDirectPainter calls QwtPlotCurve::drawSeries(), where the curve pen is used for drawing the lines.
So setting a curve pen ( QwtPlotCurve::setPen() ) will affect the curve in the same way as with using replot().

Uwe

[aker]

Hello Uwe,

sorry but I can´t get it running. I set a pen to the curve with setPen() but only the color changes.
I tried it with my application and then with the oscilloscope example. Only when I do a replot() the pen uses the penWidth which I want to have.
This is the code from the example where I set a new pen.

d_curve = new QwtPlotCurve();
    d_curve->setStyle( QwtPlotCurve::Lines );
   // d_curve->setPen( canvas()->palette().color( QPalette::WindowText ) );
    d_curve->setRenderHint( QwtPlotItem::RenderAntialiased, true );
    d_curve->setPaintAttribute( QwtPlotCurve::ClipPolygons, false );
    d_curve->setData( new CurveData() );
    d_curve->attach( this );
 
    QPen p;
    p.setColor(Qt::red);
    p.setWidthF(5);
    d_curve->setPen(p);

d_curve = new QwtPlotCurve();
    d_curve->setStyle( QwtPlotCurve::Lines );
   // d_curve->setPen( canvas()->palette().color( QPalette::WindowText ) );
    d_curve->setRenderHint( QwtPlotItem::RenderAntialiased, true );
    d_curve->setPaintAttribute( QwtPlotCurve::ClipPolygons, false );
    d_curve->setData( new CurveData() );
    d_curve->attach( this );

    QPen p;
    p.setColor(Qt::red);
    p.setWidthF(5);
    d_curve->setPen(p);

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and only when I do a replot after drawSeries() the line have a width of 5.

void Plot::updateCurve()
{
    CurveData *data = static_cast<CurveData *>( d_curve->data() );
    data->values().lock();
 
    const int numPoints = data->size();
    if ( numPoints > d_paintedPoints )
    {
        const bool doClip = !canvas()->testAttribute( Qt::WA_PaintOnScreen );
        if ( doClip )
        {
            /*
                Depending on the platform setting a clip might be an important
                performance issue. F.e. for Qt Embedded this reduces the
                part of the backing store that has to be copied out - maybe
                to an unaccelerated frame buffer device.
            */
 
            const QwtScaleMap xMap = canvasMap( d_curve->xAxis() );
            const QwtScaleMap yMap = canvasMap( d_curve->yAxis() );
 
            QRectF br = qwtBoundingRect( *data,
                d_paintedPoints - 1, numPoints - 1 );
 
            const QRect clipRect = QwtScaleMap::transform( xMap, yMap, br ).toRect();
            d_directPainter->setClipRegion( clipRect );
        }
 
 
        d_directPainter->drawSeries( d_curve,
            d_paintedPoints - 1, numPoints - 1 );
 
        d_paintedPoints = numPoints;
    }
 
    data->values().unlock();
 
    [COLOR="#FF0000"]replot();[/COLOR]
}

void Plot::updateCurve()
{
    CurveData *data = static_cast<CurveData *>( d_curve->data() );
    data->values().lock();

    const int numPoints = data->size();
    if ( numPoints > d_paintedPoints )
    {
        const bool doClip = !canvas()->testAttribute( Qt::WA_PaintOnScreen );
        if ( doClip )
        {
            /*
                Depending on the platform setting a clip might be an important
                performance issue. F.e. for Qt Embedded this reduces the
                part of the backing store that has to be copied out - maybe
                to an unaccelerated frame buffer device.
            */

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

            QRectF br = qwtBoundingRect( *data,
                d_paintedPoints - 1, numPoints - 1 );

            const QRect clipRect = QwtScaleMap::transform( xMap, yMap, br ).toRect();
            d_directPainter->setClipRegion( clipRect );
        }


        d_directPainter->drawSeries( d_curve,
            d_paintedPoints - 1, numPoints - 1 );

        d_paintedPoints = numPoints;
    }

    data->values().unlock();

    [COLOR="#FF0000"]replot();[/COLOR]
}

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Can you tell me what I do wrong???

Andre

[Uwe]

...and only when I do a replot after drawSeries() the line have a width of 5.

The direct painter simply draws on top of the existing plot - nothing gets erased, what has been painted before.

If you want to apply a modified curve pen to replace parts of a curve, that you have painted before, you have to call replot - calling drawSeries() before is not necessary. There might be optimizations, when drawing with a thicker pen, but in general it is like this.

Uwe

[aker]

Hello Uwe,

yes you are right! I played around with some things and I also changed the data collection period. The penwidth is thicker but it looks not so smooth than after a complete replot.

Thank you Uwe!