Function MACaptionAppearanceGetWindowOpacity 

pub unsafe extern "C-unwind" fn MACaptionAppearanceGetWindowOpacity(
    domain: MACaptionAppearanceDomain,
    behavior: *mut MACaptionAppearanceBehavior,
) -> CGFloat

Available on crate feature MACaptionAppearance only.

User preference for window opacity.

Parameter domain: Preference domain, see

 MACaptionAppearanceDomain

.

Parameter behavior: (see

 MACaptionAppearanceBehavior

)

Returns: User preference for window opacity.

Safety

behavior must be a valid pointer or null.