Problem in Qt, Qwt with right-click on QwtPlot and taking X and Y coordinates, signal selected

Good day! There are QwtPlot and QwtCurve, in short, blue graph, which was built using the library Qwt. Question: how to make sure that when you right-click on QwtPlot, pictured red vertical line (as in the figure, the coordinate X is taken from the cursor position)?

I can draw a line, but I can not determine which signal to connect to a slot draw. I tried to signal void QwtPlotPicker:: selected (const QPointF & pos) bind to a slot dr开发者_运维知识库aw, but the problem is that when Clicking the signal does not work (tested step by step in debugging). In what may be the problem?

P.S. Thanks in advance!

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Is your QwtPlotPicker initialized with the canvas of the plot? And what are your selectionFlags set to for the QwtPlotPicker? (You should be using QwtPicker::ClickSelection)