QwtPlot Performance: HowTo plot a lot points?

**elDell** · 8th May 2009, 13:55

Hi to everybody.
Are there any tricks to deal with a large amount of datapoint in QwtPlot? If I draw 500'000 points it takes a couple of time on every redraw.
I've tried the following without success:

Qt Code:

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myQwtPlot.canvas()->setPaintAttribute( QwtPlotCanvas::PaintCached, false );
myQwtPlot.canvas()->setPaintAttribute( QwtPlotCanvas::PaintPacked, false );
myQwtPlotCure.setPaintAttribute( QwtPlotCurve::PaintFiltered, true );

myQwtPlot.canvas()->setPaintAttribute( QwtPlotCanvas::PaintCached, false );
myQwtPlot.canvas()->setPaintAttribute( QwtPlotCanvas::PaintPacked, false );
myQwtPlotCure.setPaintAttribute( QwtPlotCurve::PaintFiltered, true );

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I've also added the zoom-implementation from the examples. If I click and move the mouse to position the rubberband for the zoom, the qwtPlot freezes for about 3 seconds!

I'm new in Qwt and don't see any way to solve the problem --> plese help me.

Thanks in advance
elDell