Apple Advanced Typography
Apple Advanced Typography ( AAT ) is a software-based overall concept for the bundling of font technologies of the macOS operating system from Apple , which combines several sub-concepts of recent developments, so that it provides sophisticated typographical options on the application level . In AAT, the ability to work with fonts as they existed under QuickDraw GX is revived after QuickDraw GX was discontinued by Apple. AAT enables automatic ligatures , different glyphs for each letter, and automatic decorative letters. AAT goes beyond the capabilities of OpenType in many typographical functions .
Programs that support AAT are XeTeX , TextEdit, and many other Cocoa programs.