In the doc: ( http://qwt.sourceforge.net/class_qwt...bf578824e2165e )

This method will attach a QwtPlotItem to the QwtPlot argument. It will first detach the QwtPlotItem from any plot from a previous call to attach (if necessary). If a NULL argument is passed, it will detach from any QwtPlot it was attached to.
But what if one want multiple Plot plot the same curve? If attach the curve to second plot, the it will be detached from the first plot. How to work around this?

Thanks in advance.