qt-everywhere-src-5.15.1/qtcharts/examples/charts/qmloscilloscope/datasource.cpp

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#include "datasource.h"
#include <QtCharts/QXYSeries>
#include <QtCharts/QAreaSeries>
#include <QtQuick/QQuickView>
#include <QtQuick/QQuickItem>
#include <QtCore/QDebug>
#include <QtCore/QRandomGenerator>
#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
    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(M_PI / 50 * j) + 0.5 + QRandomGenerator::global()->generateDouble();
                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);
    }
}