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

  1. #1
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    Question 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

  2. #2
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    Default Re: Snapping mouse cursor to curves to show tracker text, click to make it stay

    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.

    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

  3. The following user says thank you to Uwe for this useful post:

    alex_sh (13th May 2019)

  4. #3
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    Default Re: Snapping mouse cursor to curves to show tracker text, click to make it stay

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

    Thanks!
    Alexander

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