Returns the preferred opacity for the text highlight.
- iOS 7.0+
- macOS 10.9+
- Mac Catalyst 13.0+
- tvOS 9.0+
A pointer to memory. On return, this memory holds the caption appearance behavior for this preference setting. For possible values see
NULLwhen you do not need the behavior setting.
A float value, ranging from
1, representing the opacity of the color behind the text and above the window color.