/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
** $QT_END_LICENSE$
**
****************************************************************************/

/*!
    \example statemachine/trafficlight
    \title Traffic Light Example

    \brief The Traffic Light example shows how to use \l{The State Machine Framework}
    to implement the control flow of a traffic light.

    \image trafficlight-example.png

    In this example we write a TrafficLightWidget class. The traffic light has
    three lights: Red, yellow and green. The traffic light transitions from
    one light to another (red to yellow to green to yellow to red again) at
    certain intervals.

    \snippet statemachine/trafficlight/main.cpp 0

    The LightWidget class represents a single light of the traffic light. It
    provides an \c on property and two slots, turnOn() and turnOff(), to turn
    the light on and off, respectively. The widget paints itself in the color
    that's passed to the constructor.

    \snippet statemachine/trafficlight/main.cpp 1

    The TrafficLightWidget class represents the visual part of the traffic
    light; it's a widget that contains three lights arranged vertically, and
    provides accessor functions for these.

    \snippet statemachine/trafficlight/main.cpp 2

    The createLightState() function creates a state that turns a light on when
    the state is entered, and off when the state is exited. The state uses a
    timer, and as we shall see the timeout is used to transition from one
    LightState to another. Here is the statechart for the light state:

    \image trafficlight-example1.png
    \omit
    \caption This is a caption
    \endomit

    \snippet statemachine/trafficlight/main.cpp 3

    The TrafficLight class combines the TrafficLightWidget with a state
    machine.  The state graph has four states: red-to-yellow, yellow-to-green,
    green-to-yellow and yellow-to-red. The initial state is red-to-yellow;
    when the state's timer times out, the state machine transitions to
    yellow-to-green. The same process repeats through the other states.
    This is what the statechart looks like:

    \image trafficlight-example2.png
    \omit
    \caption This is a caption
    \endomit

    \snippet statemachine/trafficlight/main.cpp 4

    The main() function constructs a TrafficLight and shows it.

*/