Gets whether a toggle button is toggled on (true) or off (false).
This property can be set only if the toggle property is set to true.
For a CheckBox control, indicates whether the box is displaying a check mark. For a RadioButton control, indicates whether the control is selected.
The user can change this property by clicking the control, but you can also set the property programmatically.
In previous versions, if the toggle property was set to true, changing this property also dispatched a change event. Starting in version 3.0, setting this property programmatically only dispatches a valueCommit event.
The default value is false.