QwtPlotCurve draw it's full contents without using current zoom information

[Uwe]

Using the characteristics of the data is the job of the application code - QwtPlotCurve doesn't know about them.

I recommend to derive from QwtSeriesData<QPointF> ( or one of its derived classed ), where you return only points from the current zoom interval: check the pure virtual methods.

To know the current scale interval do:

connect( plot->axisWidget( QwtPlot::xBottom ), SIGNAL( scaleDivChanged() ), this, updateCurrentZoom() );

connect( plot->axisWidget( QwtPlot::xBottom ), SIGNAL( scaleDivChanged() ), this, updateCurrentZoom() );

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and something like this:

void YourWhatever::updateCurrentZoom()
{
    const QwtScaleDiv scaleDiv = plot->axisScaleDiv( QwtPlot::xBottom );
    updateCurrentZoom( scaleDiv->interval() );
}

void YourWhatever::updateCurrentZoom()
{
    const QwtScaleDiv scaleDiv = plot->axisScaleDiv( QwtPlot::xBottom );
    updateCurrentZoom( scaleDiv->interval() );
}

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Uwe