# class `CheckBox(Control)`

A CheckBox is a control which has either two or three possible states. The possible states of a two-state check box are on and off; three-state check boxes may have an additional state mixed. Clicking the CheckBox changes it from one state to another. Each time the state changes, its action is performed.

## Constructor

CheckBox(title)
  Constructs a CheckBox with the given title.

## Properties

> `title`
>   Title string to be displayed beside the check box.
> value
>   The state of the check box. May have the values True or False, and in the case of a three-state check box, 'mixed'.
> `action`
>   Action to perform when the user changes the state of the check box. See Actions.
> `auto_toggle`
>   True if the `on` property is to be automatically changed when the user clicks the check box. Defaults to true. If set to false, the action will still be performed when the check box is clicked, but the program is responsible for changing the state.
> mixed
>   If true, the check box can be in a mixed state. Defaults to false.

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