Static kCTFontFeatureSelectorIdentifierKey 

pub unsafe static kCTFontFeatureSelectorIdentifierKey: &'static CFString

Available on crate feature CTFont only.

kCTFontFeatureSelectorIdentifierKey

Key to get the font feature selector identifier.

This key can be used with a selector dictionary corresponding to a feature type to obtain the selector identifier value as a CFNumberRef.

See also Apple’s documentation