I am having some difficulties drawing multiple lines on my polar plot. I can create multiple qwtpolarmarkers on the plot but when I create a line of type qwtpolarcurve and attach it to the polar plot, only the last curve will be displayed.

pseudo code to illustrate:
Qt Code:
  1. QwtPolarMarker * polarmarker = new QwtPolarMarker();
  2. polarmarker->setPosition(......);
  3. polarmarker->attach(polarPlot);
  4. polarPlot->replot(); //1st marker is displayed
  6. QwtPolarMarker * polarmarker2 = new QwtPolarMarker();
  7. polarmarker2->setPosition(......);
  8. polarmarker2->attach(polarPlot);
  9. polarPlot->replot(); //2nd marker is displayed
  11. QwtPolarCurve * curve = new QwtPolarCurve();
  12. curve->setData(......);
  13. curve->attach(polarPlot);
  14. polarPlot->replot(); // 1st line is displayed
  16. QwtPolarCurve * curve2 = new QwtPolarCurve();
  17. curve2->setData(......);
  18. curve2->attach(polarPlot);
  19. polarPlot->replot(); // 2nd line is displayed, 1st line disappears
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I stepped through the codes and I can see that the 1st curve is plotted before disappearing on the last replot call. Any ideas on what I might be missing?