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    41 

    42 /*!

    43     \example statemachine/trafficlight

    44     \title Traffic Light Example

    45 

    46     The Traffic Light example shows how to use \l{The State Machine Framework}

    47     to implement the control flow of a traffic light.

    48 

    49     \image trafficlight-example.png

    50 

    51     In this example we write a TrafficLightWidget class. The traffic light has

    52     three lights: Red, yellow and green. The traffic light transitions from

    53     one light to another (red to yellow to green to yellow to red again) at

    54     certain intervals.

    55 

    56     \snippet examples/statemachine/trafficlight/main.cpp 0

    57 

    58     The LightWidget class represents a single light of the traffic light. It

    59     provides an \c on property and two slots, turnOn() and turnOff(), to turn

    60     the light on and off, respectively. The widget paints itself in the color

    61     that's passed to the constructor.

    62 

    63     \snippet examples/statemachine/trafficlight/main.cpp 1

    64 

    65     The TrafficLightWidget class represents the visual part of the traffic

    66     light; it's a widget that contains three lights arranged vertically, and

    67     provides accessor functions for these.

    68 

    69     \snippet examples/statemachine/trafficlight/main.cpp 2

    70 

    71     The createLightState() function creates a state that turns a light on when

    72     the state is entered, and off when the state is exited. The state uses a

    73     timer, and as we shall see the timeout is used to transition from one

    74     LightState to another. Here is the statechart for the light state:

    75 

    76     \img trafficlight-example1.png

    77     \omit

    78     \caption This is a caption

    79     \endomit

    80 

    81     \snippet examples/statemachine/trafficlight/main.cpp 3

    82 

    83     The TrafficLight class combines the TrafficLightWidget with a state

    84     machine.  The state graph has four states: red-to-yellow, yellow-to-green,

    85     green-to-yellow and yellow-to-red. The initial state is red-to-yellow;

    86     when the state's timer times out, the state machine transitions to

    87     yellow-to-green. The same process repeats through the other states.

    88     This is what the statechart looks like:

    89 

    90     \img trafficlight-example2.png

    91     \omit

    92     \caption This is a caption

    93     \endomit

    94 

    95     \snippet examples/statemachine/trafficlight/main.cpp 4

    96 

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

    98 

    99 */