Hello.
I have a problem with QChart.
When i plot >3000 samples it goes incredibly slow. I tried plotting a signal with 16000 samples, which took 13 seconds to plot.

Here is the bit that is causing problems:

Qt Code: 
  1. QLineSeries *lineseries = new QLineSeries();
  2.       QScatterSeries *scatterseries = new QScatterSeries();
  3.       QTime mytimer;
  4.       mytimer.start();
  5.       lineseries->append(ali[bandnr].toList()); // QVector<QPointF>
  6.       scatterseries->append(ali[bandnr].toList());
  7.       chart_->addSeries(lineseries);
  8.       chart_->addSeries(scatterseries);
  9.       qDebug() << "time: " << mytimer.elapsed();
  10.  
  11.       scatterseries->setMarkerSize(8);
  12.       scatterseries->setPen(Qt::NoPen); // do not make border around points
  13.       QString name = "hello";
  14.       connect(scatterseries, &QScatterSeries::clicked, this, &LinePlot::keepCallout_);
  15.       connect(scatterseries, &QScatterSeries::hovered, [=](QPointF point, bool state) {this->tooltip_(point, state, name); });
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"ali" is just a QVector<QVector<QPointF>>
I read somewhere that appending the data to the QLineSeries/QScatterSeries before adding them to QChart would improve speed. But its the same.
I also read that using "replace" instead of "append" should increase the speed. But it doesn't change anything.

The reason i also add a QScatterSeries is to make my "hover" tooltip only appear on actual data points.

I also tried QCustomPlot instead, which uses 0.142 seconds to plot the same data. Why is QChart that much slower? Is there a solution to make it faster?

Best Regards
DAVC