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/****************************************************************************
**
** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** GNU Free Documentation License
** 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.
**
** Other Usage
** Alternatively, this file may be used in accordance with the terms
** and conditions contained in a signed written agreement between you
** and Nokia.
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\example statemachine/trafficlight
\title Traffic Light Example
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.
*/
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