A Boolean value that indicates whether the button allows a mixed state.
- macOS 10.0+
The value of this property is
YES if the button has three states (on, off, and mixed), or
NO if the button has two states (on and off). The default value is
NO. On and off states (also referred to as alternate and normal) indicate that the button is either clicked or not clicked. Mixed state is typically used for checkboxes or radio buttons. For example, suppose the state of a checkbox is used to denote whether a text field contains bold text. If all of the text in the text field is bold, then the checkbox appears checked (on). If none of the text is bold, then the checkbox appears unchecked (off). If some of the text is bold, then the checkbox contains a dash (mixed).