QwtPlotPicker picks points of whole canvas, but I need only the points on QwtPlotCurv

[rawfool]

As I'm giving the canvas of the plot, it's taking the whole canvas for mouse tracking. But how do I set it to track/show only the points of the curve?

curve->setSamples(xValues, yValues, 11);
curve->attach(oParamGraph);
 
oParamGraph->setAxisScaleDraw(QwtPlot::xBottom, new TimeScaleDraw(cpuStat.upTime()));
oParamGraph->setAxisScale(QwtPlot::xBottom, 0, 165, 15);
oMyPicker = new QwtPlotPicker(QwtPlot::xBottom, QwtPlot::yLeft, QwtPlotPicker::NoRubberBand, QwtPicker::AlwaysOn, oParamGraph[iCount]->canvas());

curve->setSamples(xValues, yValues, 11);
curve->attach(oParamGraph);

oParamGraph->setAxisScaleDraw(QwtPlot::xBottom, new TimeScaleDraw(cpuStat.upTime()));
oParamGraph->setAxisScale(QwtPlot::xBottom, 0, 165, 15);
oMyPicker = new QwtPlotPicker(QwtPlot::xBottom, QwtPlot::yLeft, QwtPlotPicker::NoRubberBand, QwtPicker::AlwaysOn, oParamGraph[iCount]->canvas());

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Thank you.