Static kCTFontFeatureSettingsAttribute 

pub unsafe static kCTFontFeatureSettingsAttribute: &'static CFString

Available on crate feature CTFontDescriptor only.

kCTFontFeatureSettingsAttribute

The array of typographic feature settings.

This key is used to specify an array of zero or more feature settings. Each setting dictionary indicates which setting should be applied. In the case of duplicate or conflicting settings the last setting in the list will take precedence. In the case of AAT settings, it is the caller’s responsibility to handle exclusive and non-exclusive settings as necessary. An AAT setting dictionary contains a tuple of a kCTFontFeatureTypeIdentifierKey key-value pair and a kCTFontFeatureSelectorIdentifierKey key-value pair. An OpenType setting dictionary contains a tuple of a kCTFontOpenTypeFeatureTag key-value pair and a kCTFontOpenTypeFeatureValue key-value pair.

Starting with OS X 10.10 and iOS 8.0, settings are also accepted (but not returned) in the following simplified forms: An OpenType setting can be either an array pair of tag string and value number, or a tag string on its own. For example: @ [ “ c2sc“, @1 ] or simply @“c2sc”. An unspecified value enables the feature and a value of zero disables it. An AAT setting can be specified as an array pair of type and selector numbers. For example: @ [ @ (kUpperCaseType), @ (kUpperCaseSmallCapsSelector) ].

See also Apple’s documentation