I have extended QwtPolarItem to add some information to it, e.g., a timestamp. On a QwtPolarPlot, I want to be able to click on one of these items and display its timestamp. I'm using QwtPolarPicker to capture the mouse click. How do I use that to find the nearest QwtPolarItem? Would I be better off using something like the CanvasPicker that is in the event_filter example?