Static kCTFontCharacterSetAttribute 

pub unsafe static kCTFontCharacterSetAttribute: &'static CFString

Available on crate feature CTFontDescriptor only.

kCTFontCharacterSetAttribute

The font Unicode character coverage set.

The value for this key is a CFCharacterSetRef. Creating a font with this attribute will restrict the font to a subset of its actual character set.

See also Apple’s documentation