Editing Apple Advanced Typography (section)

== Features ==
[[Image:Zapfino.svg|thumb|right|312px|Example of the extra glyphs and ligatures available in the ''[[Zapfino]]'' typeface]]

Significant features of AAT include:

* Several degrees of [[ligature (typography)|ligature]] control
* [[Kashida]] justification and joiners
* Cross-stream [[kerning]] (required for [[Nasta'liq]] [[Urdu]], for example)
* Indic vowel rearrangement
* Independently controllable substitution of:
** [[Text figures|Old style figures]]
** [[Small caps]] and [[Initial|drop caps]]
** [[swash (typography)|Swash]] variants
** Alternative glyphs:
*** Individual alternatives on a per-glyph basis
*** Wholesale alternatives, such as engraved text
** Anything else the font designer wants to add
* Glyph variation axes

AAT font features are supported on [[Mac OS 8.5]] and above and all versions of macOS. The cross-platform [[International Components for Unicode|ICU]] library provided basic AAT support for left-to-right scripts.<ref>{{cite web|url=http://userguide.icu-project.org/layoutengine#TOC-Overview|title=Layout Engine - ICU User Guide|publisher=}}</ref> [[HarfBuzz]] version 2 has added AAT shaping support, an open-source implementation of the technology<ref>{{Cite web|url=https://www.phoronix.com/scan.php?page=news_item&px=HarfBuzz-2.0-Released|title = HarfBuzz 2.0 Released for Advancing Open-Source Text Shaping |website=Phoronix |date=19 October 2018}}</ref> which [[Google Chrome|Chrome]]/[[Chromium (web browser)|Chromium]] as version 72 and [[LibreOffice]] as version 6.3 uses it instead of CoreText for rendering macOS AAT fonts in cross-platform way.

As of [[OS X Yosemite]] and [[iOS 8]], AAT supports language-specific shaping—that is, changing how glyphs are processed depending on the human language they are being used to represent. This support is available through the use of language tags in [[Core Text]].<ref>{{cite web|url=https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6ltag.html|title=Language Tag Table|author=|publisher=Apple Inc.}}</ref> Provision was added at the same time for the relative positioning of two glyphs via anchor points via the 'kerx' and 'ankr' tables.<ref>{{cite web|url=https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6ankr.html|title=Anchor Point Table|author=|publisher=Apple Inc.}}</ref>