Snapping mouse cursor to curves to show tracker text, click to make it stay

Hi,

Thanks a lot for the great Qwt!

Is it possible to do something like Qt Charts' "callout" example in Qwt (or something similar)?

This is my task:

1. The mouse cursor's tracker (showing X and Y coordinates) should "snap" to a curve if it's close enough. I'm not sure yet whether it should be the actual curve points or the interpolated curve. I guess just the curve points would be fine.

2. The tracker texts (showing X and Y coordinates) should stay there (maybe as a marker item) when the user clicks (actually, control-clicks) that point. Multiple such markers should be possible. Control-clicking them again should remove them (though this could be done though a context menu to remove all such markers).

Any pointers, examples, or even suggestions to forget about this are welcome! :)

Thanks a lot!
Alexander

Quote:

---

The mouse cursor's tracker (showing X and Y coordinates) should "snap" to a curve if it's close enough.

---

This is usually done with a QwtPlotPicker - maybe have a look at the curveTracker example for inspiration.

Quote:

---

The tracker texts (showing X and Y coordinates) should stay there (maybe as a marker item) when the user clicks (actually, control-clicks) that point.

---

If you assign a QwtPickerClickPointMachine to your picker you get signals in plot coordinates for each click. Then all you have to do is to insert/remove a QwtPlotMarker.

HTH,
Uwe

Thank you very much, Uwe.
I'll follow your suggestions.

Thanks!
Alexander