Dear UWE,

I'm testing QwtPlotCurve with "big data". Previously you said that in QWT SVN trunk there is QWT 6.2 where I can find QwtPlotCurve::FilterPointsAggressive to increase perfomance of plotting large data. So I use QWT 6.2 from SVN.
I plotted curves in cycle up to 20000 and each curve has 1000 points. Plotted data takes about 300 megabytes RAM and takes to plot maybe 25 seconds (I didn't measure exactly but not bad as few second is spent for reading data from SSD disk).
When I tried to add QwtPlotCurve::setPaintAttribute I didn't see any changes in perfomance. I tried to set MinimizeMemory/FilterPoints/FilterPointsAgressive to true/false with no luck. Maybe I do something wrong? Here is the code:
Qt Code:
  1. for (quint64 j = 0; j < nTrc; j++){
  2. QwtPlotCurve *curve = new QwtPlotCurve();
  3. curve->setPen( Qt::blue, 1 );
  4. curve->setRenderHint( QwtPlotItem::RenderAntialiased, true );
  5. curve->setOrientation(Qt::Vertical);
  6. curve->setSamples(Col<float>(TRACE_DATA.col(j)+j).memptr(), t.memptr(), nSamp); // data from Armadillo matrix
  7. curve->setPaintAttribute(QwtPlotCurve::MinimizeMemory, true); // I tried to swap true/false everywhere...
  8. curve->setPaintAttribute(QwtPlotCurve::FilterPoints, true);
  9. curve->setPaintAttribute(QwtPlotCurve::FilterPointsAggressive, true);
  10. curve->attach( plotForm );
  11. }
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Woud it help if I set curve->setRenderThreadCount(N); in my case (for hundreds and thousands curves)?

Here is how it looks for 50 lines (I tried it up to 20000 lines):
1.jpg