void QLed::paintEvent(QPaintEvent *)

{

    QString ledShapeAndColor;

    QPainter painter(this);

    painter.setRenderHint(QPainter::Antialiasing, true);

    ledShapeAndColor=shapes[m_shape];

    if(m_value)

        ledShapeAndColor.append(colors[m_onColor]);

    else

        ledShapeAndColor.append(colors[m_offColor]);

    
    render = new QtSvgRenderer();

    renderer->load(ledShapeAndColor);

    renderer->render(&painter);

}

MainWindow::MainWindow(QWidget *parent) :

    QMainWindow(parent),

    ui(new Ui::MainWindow)

{

    ui->setupUi(this);

    qDebug()<<"MainWindow.";

    ui->led1->setShape(SQUARE);

    ui->led1->setOnColor(GREEN);

    ui->led2->setShape(CIRCLE);

    ui->led2->setOnColor(RED);

    led_status = TRUE;

    timer.setInterval(100);

    timer.start();

    connect(&timer, SIGNAL(timeout()), this, SLOT(timeHandler()), Qt::DirectConnection);

}

void MainWindow::timeHandler()

{

    //qDebug()<<"timeHandler()";

    if(led_status)

    {

        ui->led1->setValue(TRUE);

        ui->led2->setValue(TRUE);

        led_status = FALSE;

    }

    else

    {

        ui->led1->setValue(FALSE);

        ui->led2->setValue(FALSE);

        led_status = TRUE;

    }

}

References:

https://stackoverflow.com/questions/39592363/pulse-led-on-button-toggle-in-qt

https://stackoverflow.com/questions/8551690/how-to-render-a-scaled-svg-to-a-qimage

https://doc.qt.io/qt-5/qsvgrenderer.html#details