QChart update automatically problem

[Alien]

Hello,
I've implemented a simple line chart to update automatically with a timer as a data feeder

#include "ui_mainwindow.h"
#include <QtCharts/QChartGlobal>
#include <QValueAxis>
#include <QDebug>


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

    m_chart = new QChart();
    m_chart->setTitle("Encoders");

    m_series = new QLineSeries();

    QValueAxis *axisX = new QValueAxis();
    axisX->setRange(0, 1000);
    QValueAxis *axisY = new QValueAxis();
    axisY->setRange(-100, 100);

    /*
     * Without these two lines chart will never update
     *
     */
    m_series->append(0,-100);
    m_series->append(1000,100);


    m_chart->setAxisX(axisX);
    m_chart->setAxisY(axisY);

    m_view = new QChartView(m_chart);
    m_view->setRenderHint(QPainter::Antialiasing);


    QPen pen(QRgb(0xfd000A));
    pen.setWidth(0.5);
    m_series->setPen(pen);
    m_chart->addSeries(m_series);


    ui->gridLayout->addWidget(m_view,1,0);




    m_timer = new QTimer(this);
    connect(m_timer, SIGNAL(timeout()), this, SLOT(updateChart()));
    m_timer->start(5);
}

/*******************************************************/
void MainWindow::updateChart()
{
    static int seed = 0;

    qreal x = seed;
    qreal y = qrand()%100;

    y=(qrand()%17==0)?-y:y;

    if(seed%1000==0)
    {
        m_series->clear();
        seed=0;
        x=seed;
        qDebug()<<"SET ZERO";
    }
    m_series->append(x,y);

    seed+=1;
}

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

Chart get update after each data which append to m_series but if I remove the below lines in the constructor:

m_series->append(0,-100);
m_series->append(1000,100);

chart will never update?!!! Also if I put wrong values for these two lines, chart's behaviuor goes wrong for example if I put the below lines instead of previous one:

m_series->append(0,-100);
m_series->append(100,100);

x axis will be limit to 0~100 even though I setAxisX 0~1000.

I can't understand the behavior of chart could you please give me a hint?

[MrShawn]

Try attaching your axis to the series as well as the chart. Off a quick inspection you are only attaching to the chart.
By not attaching the axis to the series it is likely building a dflt axis off your initial values. Which is why when you do 100 vs 1000 your range is limited.

[Alien]

This post is deleted!

[Alien]

@MrShawn ,Thanks a lot now it works fine