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ATSUI Implementation of the Unicode Specification

This appendix provides additional details about the implementation of the Unicode specification in ATSUI. ATSUI provides full layout support for Unicode 3.2 and supports text rendering for all the features required by scripts included with version 2.1 of the Unicode standard or later. It does not provide other Unicode-related text processing services such as date and time formatting, collation, or string matching. The ability of ATSUI to render Unicode text is limited only by the available fonts the user has installed.

The correct handling of many Unicode characters requires that the current font supports those characters properly. For example, correct ligature formation requires that the font supports those features using Apple Advanced Typography (AAT) tables. If there is more than one equivalent combining character sequence for a given glyph, the font is responsible for mapping all such sequences to the correct glyph. For example, ATSUI does not automatically support conjoining Jamo in a Korean font that specifies precomposed glyphs only. For more details on the required AAT font tables and tools for creating them, see the description of Apple Advanced Typography at http://developer.apple.com/fonts/.

Contents:

Unsupported Control Characters
Surrogates
Character Properties

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