Qt 5.7 | Qt Charts | Qml Oscilloscope | datasource.cpp Example File

Qt 5.7.1 Reference Documentation

# datasource.cpp Example File

qmloscilloscope/datasource.cpp

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      ** Copyright (C) 2016 The Qt Company Ltd.
      ** Contact: https://www.qt.io/licensing/
      **
      ** This file is part of the Qt Charts module of the Qt Toolkit.
      **
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      #include "datasource.h"
      #include <QtCharts/QXYSeries>
      #include <QtCharts/QAreaSeries>
      #include <QtQuick/QQuickView>
      #include <QtQuick/QQuickItem>
      #include <QtCore/QDebug>
      #include <QtCore/QtMath>

      QT_CHARTS_USE_NAMESPACE

      Q_DECLARE_METATYPE(QAbstractSeries *)
      Q_DECLARE_METATYPE(QAbstractAxis *)

      DataSource::DataSource(QQuickView *appViewer, QObject *parent) :
          QObject(parent),
          m_appViewer(appViewer),
          m_index(-1)
      {
          qRegisterMetaType<QAbstractSeries*>();
          qRegisterMetaType<QAbstractAxis*>();

          generateData(0, 5, 1024);
      }

      void DataSource::update(QAbstractSeries *series)
      {
          if (series) {
              QXYSeries *xySeries = static_cast<QXYSeries *>(series);
              m_index++;
              if (m_index > m_data.count() - 1)
                  m_index = 0;

              QVector<QPointF> points = m_data.at(m_index);
              // Use replace instead of clear + append, it's optimized for performance
              xySeries->replace(points);
          }
      }

      void DataSource::generateData(int type, int rowCount, int colCount)
      {
          // Remove previous data
          foreach (QVector<QPointF> row, m_data)
              row.clear();
          m_data.clear();

          // Append the new data depending on the type
          for (int i(0); i < rowCount; i++) {
              QVector<QPointF> points;
              points.reserve(colCount);
              for (int j(0); j < colCount; j++) {
                  qreal x(0);
                  qreal y(0);
                  switch (type) {
                  case 0:
                      // data with sin + random component
                      y = qSin(3.14159265358979 / 50 * j) + 0.5 + (qreal) rand() / (qreal) RAND_MAX;
                      x = j;
                      break;
                  case 1:
                      // linear data
                      x = j;
                      y = (qreal) i / 10;
                      break;
                  default:
                      // unknown, do nothing
                      break;
                  }
                  points.append(QPointF(x, y));
              }
              m_data.append(points);
          }
      }