datasource.cpp Example File

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  #include "datasource.h"
  #include <QtCore/QtMath>

  QT_CHARTS_USE_NAMESPACE

  DataSource::DataSource(QObject *parent) :
      QObject(parent),
      m_index(-1)
  {
      generateData(0, 0, 0);
  }

  void DataSource::update(QAbstractSeries *series, int seriesIndex)
  {
      if (series) {
          QXYSeries *xySeries = static_cast<QXYSeries *>(series);
          const QVector<QVector<QPointF> > &seriesData = m_data.at(seriesIndex);
          if (seriesIndex == 0)
              m_index++;
          if (m_index > seriesData.count() - 1)
              m_index = 0;

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

  void DataSource::handleSceneChanged()
  {
      m_dataUpdater.start();
  }

  void DataSource::updateAllSeries()
  {
      static int frameCount = 0;
      static QString labelText = QStringLiteral("FPS: %1");

      for (int i = 0; i < m_seriesList.size(); i++)
          update(m_seriesList[i], i);

      frameCount++;
      int elapsed = m_fpsTimer.elapsed();
      if (elapsed >= 1000) {
          elapsed = m_fpsTimer.restart();
          qreal fps = qreal(0.1 * int(10000.0 * (qreal(frameCount) / qreal(elapsed))));
          m_fpsLabel->setText(labelText.arg(QString::number(fps, 'f', 1)));
          m_fpsLabel->adjustSize();
          frameCount = 0;
      }
  }

  void DataSource::startUpdates(const QList<QXYSeries *> &seriesList, QLabel *fpsLabel)
  {
      m_seriesList = seriesList;
      m_fpsLabel = fpsLabel;

      m_dataUpdater.setInterval(0);
      m_dataUpdater.setSingleShot(true);
      QObject::connect(&m_dataUpdater, &QTimer::timeout,
                       this, &DataSource::updateAllSeries);

      m_fpsTimer.start();
      updateAllSeries();
  }

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

      m_data.clear();

      qreal xAdjustment = 20.0 / (colCount * rowCount);
      qreal yMultiplier = 3.0 / qreal(seriesCount);

      // Append the new data depending on the type
      for (int k(0); k < seriesCount; k++) {
          QVector<QVector<QPointF> > seriesData;
          qreal height = qreal(k) * (10.0 / qreal(seriesCount)) + 0.3;
          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);
                  // data with sin + random component
                  y = height + (yMultiplier * qSin(3.14159265358979 / 50 * j)
                                + (yMultiplier * (qreal) rand() / (qreal) RAND_MAX));
                  // 0.000001 added to make values logaxis compatible
                  x = 0.000001 + 20.0 * (qreal(j) / qreal(colCount)) + (xAdjustment * qreal(i));
                  points.append(QPointF(x, y));
              }
              seriesData.append(points);
          }
          m_data.append(seriesData);
      }
  }