Context may also determine which glyph is used to represent a character.
Many glyphs do not have a one-to-one relationship to characters: one or more glyphs may make up a single character (for example, an "i" could be rendered as a dot accent over a dotless "i"), and a single glyph can represent two or more characters ("f" and "i" could be represented by the "fi" ligature). Fonts usually incorporate other information, such as which glyphs represent ligatures or contextual forms. Here's an example of a kanji glyph which corresponds to characters in several different languages:Ī fontis a collection of glyphs with some element of design consistency, such as the use of serifs or consistent stroke thickness. For example, glyphs in different fonts, such as Times Roman or Zapf Chancery, may be used to represent the character "A". A glyphrepresents the visual, graphical appearance of a character. A characteris an abstract object having a single and unique semantic or phonetic meaning. Font features that will be supported by your font must be a part of the Registry to suggest additions to the Registry, contact: Characters, Glyphs, and Fontsįundamental to understanding text processing is the distinction between characters and glyphs. You may include one or more of these features or create your own text features. Additional features will be added by Apple and by font developers. The font tables store sets of strings identifying the features that can be presented to the user.Īpple has defined a set of text features in the AAT Font Feature Registry. Applications can pick and choose your font to determine the features available. See the Unicode Consortium's web site for more information on Unicode.įont vendors can create tables that implement different sets of features. You may also need The Unicode Standard: Worldwide Character Encoding, version 2.0, which is available from Addison-Wesley. The other tables of the resource are described in the TrueType font specification. The complete 'sfnt' resource is not described here. This document explains the font tables you include in the 'sfnt' resource in order for your font to offer special features and effects. This document is intended for font developers who are creating fonts to be used with AAT.
Many of these features are required for scripts other than Roman, such as Arabic or Devanagari.Īpple currently provides support for drawing using AAT fonts via Apple Type Services for Unicode™ Imaging (ATSUI). About Apple Advanced Typography Fonts IntroductionĪpple's text imaging technology, Apple Advanced Typography (AAT), enables applications to provide users with fonts having special typographical effects, such as cursive connection, ornateness, and complex ligatures.
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