Static kCTFontFeatureTooltipTextKey 

pub unsafe static kCTFontFeatureTooltipTextKey: &'static CFString

Available on crate feature CTFont only.

kCTFontFeatureTooltipTextKey

Key to get the font feature tooltip text.

This key can be used with a font feature dictionary to get the localized tooltip text as a CFStringRef.

See also Apple’s documentation