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/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
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** Commercial Usage
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** accordance with the Qt Commercial License Agreement provided with the
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** a written agreement between you and Nokia.
**
** GNU Lesser General Public License Usage
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** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file. Please review the following information to
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**
** In addition, as a special exception, Nokia gives you certain additional
** rights. These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
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** GNU General Public License Usage
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****************************************************************************/
/*!
\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 examples/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 examples/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 examples/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:
\img trafficlight-example1.png
\omit
\caption This is a caption
\endomit
\snippet examples/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:
\img trafficlight-example2.png
\omit
\caption This is a caption
\endomit
\snippet examples/statemachine/trafficlight/main.cpp 4
The main() function constructs a TrafficLight and shows it.
*/
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