Apple Advanced Typography
| Developer(s) | Apple Inc |
|---|---|
| Operating system | Classic Mac OS, macOS |
| Type | System Utility |
| License | Proprietary |
| Website | developer.apple.com/ fonts |
Apple Advanced Typography (AAT) is Apple Inc.'s computer software for advanced font rendering, supporting internationalization and complex features for typographers, a successor to Apple's little-used QuickDraw GX font technology of the mid-1990s. It is a set of extensions to the TrueType outline font standard, with smartfont features similar to the OpenType font format that was developed by Adobe and Microsoft, and the open source Graphite. It also incorporates concepts from Adobe's "multiple master" font format, allowing for axes of traits to be defined and morphing of a glyph independently along each of these axes. AAT font features do not alter the underlying typed text; they only affect the characters' representation during glyph conversion.
Significant features of AAT currently include:
AAT font features are supported on Mac OS 8.5 and above and all versions of macOS. The cross-platform ICU library provide basic AAT support for left-to-right scripts.
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. Provision was added at the same time for the relative positioning of two glyphs via anchor points via the ‘kerx’ and ‘ankr’ tables.
As of Mac OS X 10.5 Leopard, partial support for OpenType is available. As of 2011, support is limited to Western and Arabic scripts. If a font has AAT tables, they will be used for typography. If the font does not have AAT tables but does have OpenType tables, they will be used to the extent that the system supports them.
This means that many OpenType fonts for Western or Middle Eastern scripts can be used without modification on Mac OS X 10.5, but South Asian scripts such as Thai and Devanagari cannot. These require AAT tables for proper layout.
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