Qt with Cascades UI Examples Documentation

TrafficLightController.cpp Example File

trafficlight/src/TrafficLightController.cpp
    /****************************************************************************
     **
     ** Portions Copyright (C) 2012 Research In Motion Limited.
     ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
     ** All rights reserved.
     ** Contact: Research In Motion Ltd. (http://www.rim.com/company/contact/)
     ** Contact: Nokia Corporation (qt-info@nokia.com)
     **
     ** This file is part of the examples of the BB10 Platform and is derived
     ** from a similar file that is part of the Qt Toolkit.
     **
     ** You may use this file under the terms of the BSD license as follows:
     **
     ** "Redistribution and use in source and binary forms, with or without
     ** modification, are permitted provided that the following conditions are
     ** met:
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     **     notice, this list of conditions and the following disclaimer in
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     ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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    #include "TrafficLightController.hpp"

    #include <QHistoryState>
    #include <QStateMachine>
    #include <QTimer>

    TrafficLightController::TrafficLightController(QObject *parent)
        : QObject(parent)
        , m_redOn(false)
        , m_yellowOn(false)
        , m_greenOn(false)
        , m_paused(false)
        , m_timer(new QTimer(this))
    {
        // Create and start the state machine
        setupStateMachine();

        // Start the timer to trigger state changes
        m_timer->start();
    }

    bool TrafficLightController::redOn() const
    {
        return m_redOn;
    }

    void TrafficLightController::setRedOn(bool on)
    {
        if (m_redOn != on) {
            m_redOn = on;
            emit redOnChanged();
        }
    }

    bool TrafficLightController::yellowOn() const
    {
        return m_yellowOn;
    }

    void TrafficLightController::setYellowOn(bool on)
    {
        if (m_yellowOn != on) {
            m_yellowOn = on;
            emit yellowOnChanged();
        }
    }

    bool TrafficLightController::greenOn() const
    {
        return m_greenOn;
    }

    void TrafficLightController::setGreenOn(bool on)
    {
        if (m_greenOn != on) {
            m_greenOn = on;
            emit greenOnChanged();
        }
    }

    bool TrafficLightController::paused() const
    {
        return m_paused;
    }

    void TrafficLightController::setPaused(bool paused)
    {
        if (m_paused != paused) {
            m_paused = paused;
            emit pausedChanged();
        }
    }

    void TrafficLightController::pause()
    {
        emit pauseRequested();
    }

    void TrafficLightController::setupStateMachine()
    {
        /**
         * The state machine consists of two top-level states
         *   - runningState
         *   - pausedState
         *
         * The runningState consists of 4 child states that represent the 4 phase
         * of a traffic light cycle:
         *   - stopState:   The red light is on, cars have to wait
         *   - waitState:   The red and yellow lights are on, cars can prepare to drive
         *   - driveState:  The green light is on, cars can drive
         *   - slowState:   The yellow light is on, cars have to slow down and stop
         *
         * Additionally the runningState contains a QHistoryState as child state, which is
         * used when going back from pausedState to runningState to ensure that we continue
         * execution at the same state we have been before we switched to the pausedState.
         */

        // Create the state machine
        QStateMachine *machine = new QStateMachine(this);

        // Create the two top-level states
        QState *runningState = new QState(machine);
        QState *pausedState = new QState(machine);

        // Create the child states for the runningState
        QState *stopState = new QState(runningState);
        QState *waitState = new QState(runningState);
        QState *driveState = new QState(runningState);
        QState *slowState = new QState(runningState);

        QHistoryState *historyState = new QHistoryState(runningState);

        // Define which properties should be modified when entering a state:

        /**
         * Depending on whether we are in runningState or pausedState, the 'paused' property
         * of the TrafficLightControl object will be set to false/true.
         */
        runningState->assignProperty(this, "paused", false);
        pausedState->assignProperty(this, "paused", true);

        /**
         * For each phase state we define which light should be enabled and
         * how long the phase should last.
         */
        stopState->assignProperty(this, "redOn", true);
        stopState->assignProperty(this, "yellowOn", false);
        stopState->assignProperty(this, "greenOn", false);
        stopState->assignProperty(m_timer, "interval", 5000);

        waitState->assignProperty(this, "redOn", true);
        waitState->assignProperty(this, "yellowOn", true);
        waitState->assignProperty(this, "greenOn", false);
        waitState->assignProperty(m_timer, "interval", 2000);

        driveState->assignProperty(this, "redOn", false);
        driveState->assignProperty(this, "yellowOn", false);
        driveState->assignProperty(this, "greenOn", true);
        driveState->assignProperty(m_timer, "interval", 5000);

        slowState->assignProperty(this, "redOn", false);
        slowState->assignProperty(this, "yellowOn", true);
        slowState->assignProperty(this, "greenOn", false);
        slowState->assignProperty(m_timer, "interval", 2000);

        // Define the transitions between the single states:

        /**
         * We cycle through the phase states whenever the timer emits the timeout()
         * signal.
         */
        stopState->addTransition(m_timer, SIGNAL(timeout()), waitState);
        waitState->addTransition(m_timer, SIGNAL(timeout()), driveState);
        driveState->addTransition(m_timer, SIGNAL(timeout()), slowState);
        slowState->addTransition(m_timer, SIGNAL(timeout()), stopState);

        /**
         * If we are in runningState and the pauseRequested() signal is emitted (that happens
         * when the pause() slot has been invoked) then we go to the pausedState.
         * If we are now in the pausedState and the pauseRequested() signal is emitted again,
         * we go to the historyState which will forward us to the phase state we have been in
         * when we left the runningState.
         */
        runningState->addTransition(this, SIGNAL(pauseRequested()), pausedState);
        pausedState->addTransition(this, SIGNAL(pauseRequested()), historyState);

        // Define which child state should be the initial state
        runningState->setInitialState(stopState);
        machine->setInitialState(runningState);

        // Start the state machine
        machine->start();
    }