This project provides Qt/C++ primitives to ease building real time plot UI.

• Qt >= 5.0
• QCustomPlot (included in this repo)
• Gcc >= 6

Place the folders realtimeplot and QCustoPlot inside your Qt project folder. The folder realtimeplot contains the primitives, and the folder QCustomPlot is the 3rd party library of same name. You might need to add the folder realtimeplot to the INCLUDEPATH, otherwise you'll face errors generating the plot.ui c++ class.

QT       += core gui printsupport

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = realTimePlot
TEMPLATE = app

CONFIG += c++17

INCLUDEPATH += realtimeplot

SOURCES += main.cpp\
        mainwindow.cpp \
        QCustomPlot/qcustomplot.cpp \ 
        realtimeplot/plotarea.cpp \
        realtimeplot/pointstream.cpp

HEADERS  += mainwindow.h \
            QCustomPlot/qcustomplot.h \
            realtimeplot/plotarea.h \
            realtimeplot/pointstream.h

FORMS    += mainwindow.ui \
            realtimeplot/plotarea.ui

PlotArea is an UI component that inherits the class QCustomPlot and provides Real Time Plot similar to an Oscilloscope.

You might want to see the QCustomPlot documentation to see what features it provides by default. Fell free to customize or subclass PlotArea as needed.

This example instantiates a fixed number of curves, each one backed by its own stream of points. The curves are added to the same PlotArea as you can notice in the MainWindow's constructor.

We simulate a real-time stream of points in the timerEvent handler, which runs at the periodicity of SAMPLE_GENERATION_PERIOD.

You can check the file MainWindow.ui to see how we placed the PlotArea component to the MainWindow. However, if you need a more dynamic layout you may need to instantiate it programmatically.

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QDebug>
#include <qmath.h>

#define POINT_STREAM_NUM 4

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    for(int i=0; i<POINT_STREAM_NUM; i++) {
        QSharedPointer<PointStream> stream(new PointStream());
        stream->setSamplesPerSeconds(1000/SAMPLE_GENERATION_PERIOD);
        dataPoints << stream;
        ui->plotArea->addPointStream(stream);
    }

    ui->plotArea->setWindowLengthInSeconds(4.0);

    startTimer(SAMPLE_GENERATION_PERIOD);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::timerEvent(QTimerEvent *event)
{
    Q_UNUSED(event)

    constexpr double twoPi = 2.0*M_PI;
    constexpr double freq = 1.0; // 2Hz
    const double samplePeriod = 
        static_cast<double>(SAMPLE_GENERATION_PERIOD)/1000.0;

    for(int i=0; i<dataPoints.size(); i++) {
        double phase = (i*M_PI)/dataPoints.size();
        double value = qSin(phase + twoPi*freq*sampleNumber*samplePeriod);
        //qDebug() << sampleNumber << value;
        QVector<QPointF> data;
        data << QPointF(sampleNumber, value);
        dataPoints.at(i)->appendPoints(data);
    }

    sampleNumber++;
}

• Implement Circular Buffer
• Optimize the class Poitstream to use Circular Buffer
• Implement GraphFactory to handle CGraph Style