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#include <QtGui>

//! [0]

class LightWidget : public QWidget

{

    Q_OBJECT

    Q_PROPERTY(bool on READ isOn WRITE setOn)

public:

    LightWidget(const QColor &color, QWidget *parent = 0)

        : QWidget(parent), m_color(color), m_on(false) {}

    bool isOn() const

        { return m_on; }

    void setOn(bool on)

    {

        if (on == m_on)

            return;

        m_on = on;

        update();

    }

public slots:

    void turnOff() { setOn(false); }

    void turnOn() { setOn(true); }

protected:

    virtual void paintEvent(QPaintEvent *)

    {

        if (!m_on)

            return;

        QPainter painter(this);

        painter.setRenderHint(QPainter::Antialiasing);

        painter.setBrush(m_color);

        painter.drawEllipse(0, 0, width(), height());

    }

private:

    QColor m_color;

    bool m_on;

};

//! [0]

//! [1]

class TrafficLightWidget : public QWidget

{

public:

    TrafficLightWidget(QWidget *parent = 0)

        : QWidget(parent)

    {

        QVBoxLayout *vbox = new QVBoxLayout(this);

        m_red = new LightWidget(Qt::red);

        vbox->addWidget(m_red);

        m_yellow = new LightWidget(Qt::yellow);

        vbox->addWidget(m_yellow);

        m_green = new LightWidget(Qt::green);

        vbox->addWidget(m_green);

        QPalette pal = palette();

        pal.setColor(QPalette::Background, Qt::black);

        setPalette(pal);

        setAutoFillBackground(true);

    }

    LightWidget *redLight() const

        { return m_red; }

    LightWidget *yellowLight() const

        { return m_yellow; }

    LightWidget *greenLight() const

        { return m_green; }

private:

    LightWidget *m_red;

    LightWidget *m_yellow;

    LightWidget *m_green;

};

//! [1]

//! [2]

QState *createLightState(LightWidget *light, int duration, QState *parent = 0)

{

    QState *lightState = new QState(parent);

    QTimer *timer = new QTimer(lightState);

    timer->setInterval(duration);

    timer->setSingleShot(true);

    QState *timing = new QState(lightState);

    QObject::connect(timing, SIGNAL(entered()), light, SLOT(turnOn()));

    QObject::connect(timing, SIGNAL(entered()), timer, SLOT(start()));

    QObject::connect(timing, SIGNAL(exited()), light, SLOT(turnOff()));

    QFinalState *done = new QFinalState(lightState);

    timing->addTransition(timer, SIGNAL(timeout()), done);

    lightState->setInitialState(timing);

    return lightState;

}

//! [2]

//! [3]

class TrafficLight : public QWidget

{

public:

    TrafficLight(QWidget *parent = 0)

        : QWidget(parent)

    {

        QVBoxLayout *vbox = new QVBoxLayout(this);

        TrafficLightWidget *widget = new TrafficLightWidget();

        vbox->addWidget(widget);

        vbox->setMargin(0);

        QStateMachine *machine = new QStateMachine(this);

        QState *redGoingYellow = createLightState(widget->redLight(), 3000);

        redGoingYellow->setObjectName("redGoingYellow");

        QState *yellowGoingGreen = createLightState(widget->yellowLight(), 1000);

        yellowGoingGreen->setObjectName("yellowGoingGreen");

        redGoingYellow->addTransition(redGoingYellow, SIGNAL(finished()), yellowGoingGreen);

        QState *greenGoingYellow = createLightState(widget->greenLight(), 3000);

        greenGoingYellow->setObjectName("greenGoingYellow");

        yellowGoingGreen->addTransition(yellowGoingGreen, SIGNAL(finished()), greenGoingYellow);

        QState *yellowGoingRed = createLightState(widget->yellowLight(), 1000);

        yellowGoingRed->setObjectName("yellowGoingRed");

        greenGoingYellow->addTransition(greenGoingYellow, SIGNAL(finished()), yellowGoingRed);

        yellowGoingRed->addTransition(yellowGoingRed, SIGNAL(finished()), redGoingYellow);

        machine->addState(redGoingYellow);

        machine->addState(yellowGoingGreen);

        machine->addState(greenGoingYellow);

        machine->addState(yellowGoingRed);

        machine->setInitialState(redGoingYellow);

        machine->start();

    }

};

//! [3]

//! [4]

int main(int argc, char **argv)

{

    QApplication app(argc, argv);

    TrafficLight widget;

    widget.resize(110, 300);

    widget.show();

    return app.exec();

}

//! [4]

#include "main.moc"