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High performance live chart

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  • B Offline
    B Offline
    BartBlackMagic
    wrote on last edited by BartBlackMagic
    #1

    Scenario: sensor data is streamed at a fast pace and needs to be rendered live onto a QML ChartView using a couple of line series.

    Question: what is the most performant way to render the results? Do I:

    • buffer the results in C++ and send a signal with a QVariantList<QPointF> when a time threshold is exceeded which is then read and added to the LineSeries in qml -> exposing C++ via a context property
    • expose the QAbstractSeries from QML to C++ and fill it in C++ at a predefined refresh rate using a QTimer as in this example? -> Interacting with QML Objects from C++ which has a disclaimer in the docs here NOT to use it
    • don't use QML (which would be disappointing)
    • other ways?
    1 Reply Last reply
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    • oria66O Offline
      oria66O Offline
      oria66
      wrote on last edited by
      #2

      Hello @BartBlackMagic. The Qt Charts are not famous for their performance with real-time real data. Other people may say that use Qwt or QCustomPlot, but I would rather prefer Qt Charts with all its defects. Concretely, I love Qml, so why go out and find a 3rd party plotter?

      In your case, I face a similar problem last months. I choose the first option that you show. And it works pretty well for me.

      The truth is out there

      1 Reply Last reply
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      • M Offline
        M Offline
        MAthias_Va
        wrote on last edited by MAthias_Va
        #3

        @oria66 this is exactly what I need to do too, can you provide an example code!

        ODБOïO oria66O 2 Replies Last reply
        0
        • M MAthias_Va

          @oria66 this is exactly what I need to do too, can you provide an example code!

          ODБOïO Offline
          ODБOïO Offline
          ODБOï
          wrote on last edited by
          #4

          http://qwt.sourceforge.net/
          https://www.qcustomplot.com/

          M 1 Reply Last reply
          0
          • ODБOïO ODБOï

            http://qwt.sourceforge.net/
            https://www.qcustomplot.com/

            M Offline
            M Offline
            MAthias_Va
            wrote on last edited by
            #5

            @LeLev Thanks for your suggest, I think I can't use third party as I already crossed compiled my device with only Qt libraries!

            JKSHJ 1 Reply Last reply
            0
            • GrecKoG Offline
              GrecKoG Offline
              GrecKo
              Qt Champions 2018
              wrote on last edited by
              #6

              What about QtCharts with VXYModelMapper ?

              M 1 Reply Last reply
              0
              • M MAthias_Va

                @oria66 this is exactly what I need to do too, can you provide an example code!

                oria66O Offline
                oria66O Offline
                oria66
                wrote on last edited by
                #7

                @MAthias_Va. Give some time to isolate an example from my code. Is proprietary code, so I must change a lot of things. I will send you in your post, ok? The developers must help us each other.

                The truth is out there

                M 1 Reply Last reply
                0
                • M MAthias_Va

                  @LeLev Thanks for your suggest, I think I can't use third party as I already crossed compiled my device with only Qt libraries!

                  JKSHJ Offline
                  JKSHJ Offline
                  JKSH
                  Moderators
                  wrote on last edited by
                  #8

                  @MAthias_Va said in High performance live chart:

                  I think I can't use third party as I already crossed compiled my device with only Qt libraries!

                  You can cross-compile the 3rd party libraries later, right?

                  Qt Doc Search for browsers: forum.qt.io/topic/35616/web-browser-extension-for-improved-doc-searches

                  M 1 Reply Last reply
                  0
                  • oria66O oria66

                    @MAthias_Va. Give some time to isolate an example from my code. Is proprietary code, so I must change a lot of things. I will send you in your post, ok? The developers must help us each other.

                    M Offline
                    M Offline
                    MAthias_Va
                    wrote on last edited by
                    #9

                    @oria66 that would be great, thanks!

                    1 Reply Last reply
                    0
                    • GrecKoG GrecKo

                      What about QtCharts with VXYModelMapper ?

                      M Offline
                      M Offline
                      MAthias_Va
                      wrote on last edited by
                      #10

                      @GrecKo I will check it, thanks

                      1 Reply Last reply
                      0
                      • JKSHJ JKSH

                        @MAthias_Va said in High performance live chart:

                        I think I can't use third party as I already crossed compiled my device with only Qt libraries!

                        You can cross-compile the 3rd party libraries later, right?

                        M Offline
                        M Offline
                        MAthias_Va
                        wrote on last edited by
                        #11

                        @JKSH I followed this method, https://wiki.qt.io/RaspberryPi2EGLFS to cross compile

                        1 Reply Last reply
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