pub unsafe static kCTLigatureAttributeName: &'static CFStringCTStringAttributes only.Expand description
Controls ligature formation.
Value must be a CFNumberRef. Default is int value 1. The ligature attribute determines what kinds of ligatures should be used when displaying the string. A value of 0 indicates that only ligatures essential for proper rendering of text should be used, 1 indicates that standard ligatures should be used, and 2 indicates that all available ligatures should be used. Which ligatures are standard depends on the script and possibly the font. Arabic text, for example, requires ligatures for many character sequences, but has a rich set of additional ligatures that combine characters. English text has no essential ligatures, and typically has only two standard ligatures, those for “fi” and “fl” – all others being considered more advanced or fancy.
On iOS releases prior to 6.0 essential ligatures are applied if the font contains glyphs for any of U+FB00 through U+FB04 and the font lacks AAT or OpenType shaping tables, but as of 6.0 shaping tables (or the lack thereof) are treated as definitive.
See also Apple’s documentation