I am trying to make a realtime plot and so far I got it to show a continuous sine wave, but the plot is not moving continuously on the x-axis, but more like every second it jumps one tick to the left. How can I fix this when using the QwtDateScaleDraw and QwtDateScaleEngine? I am sure it is easy, but I can not figure it out...

My code:

Qt Code: 
  1. MyPlot::MyPlot(QWidget *parent) : QWidget(parent)
  2. {
  3.     xData = new QList<double>();
  4.     yData = new QList<double>();
  5.     plot = new QwtPlot(this);
  6.     layout = new QHBoxLayout();
  7.  
  8.     //Add widget to layout.
  9.     layout->addWidget(plot);
  10.  
  11.     //Add curves.
  12.     curve1 = new QwtPlotCurve("Curve 1");
  13.     curve1->setSamples(xData->toVector(), yData->toVector());
  14.     curve1->attach(plot);
  15.  
  16.     //Set x-axis scaling.
  17.     QwtDateScaleDraw *qwtDateScaleDraw = new QwtDateScaleDraw (Qt::OffsetFromUTC);
  18.     QwtDateScaleEngine *qwtDateScaleEngine = new QwtDateScaleEngine(Qt::OffsetFromUTC);
  19.     qwtDateScaleDraw->setDateFormat(QwtDate::Second, "hh:mm:ss");
  20.     qwtDateScaleDraw->setUtcOffset(QDateTime::currentMSecsSinceEpoch() / 1000);
  21.  
  22.     plot->setAxisScaleDraw ( QwtPlot::xBottom, qwtDateScaleDraw);
  23.     plot->setAxisScaleEngine ( QwtPlot::xBottom, qwtDateScaleEngine);
  24.     plot->setAxisMaxMajor(QwtPlot::xBottom, 0);
  25.     plot->setAxisMaxMinor(QwtPlot::xBottom, 10);
  26.  
  27.     //Replot.
  28.     plot->replot();
  29.  
  30.     //Simulated data timer.
  31.     QTimer *timer = new QTimer(this);
  32.     connect(timer, SIGNAL(timeout()), this, SLOT(appendData()));
  33.     timer->start(1);
  34. }
  35.  
  36. void MyPlot::appendData()
  37. {
  38.     static unsigned int counter = 0;
  39.  
  40.     //Add new data.
  41.     xData->append(counter);
  42.     yData->append(sin(M_PI*( (double)counter++ / 180)));
  43.  
  44.     //Remove oldest data.
  45.     if (yData->size() > 1000)
  46.     {
  47.         xData->removeFirst();
  48.         yData->removeFirst();
  49.     }
  50.  
  51.     //Set data.
  52.     curve1->setSamples(xData->toVector(), yData->toVector());
  53.  
  54.     //Replot.
  55.     plot->replot();
  56. }
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