| Platform SDK: International Features |
The Unicode-based Microsoft® OpenType® font format extends the TrueType font file format. OpenType fonts allow mapping between characters and glyphs, enabling support for ligatures, positional forms, alternates, and other substitutions. OpenType fonts may also include information that supports two-dimensional glyph positioning and glyph attachment, and may contain either TrueType or PostScript outlines.
Layout features within OpenType fonts are organized by scripts and languages, allowing a single font to support multiple writing systems, even within the same script. To ensure consistency in text layout operations and to avoid unnecessary overhead in font files or applications, many of the text layout and language semantic algorithms are included in Uniscribe. This relieves the font developer from having to define generalized script rules within a font.
Applications may introduce their own knowledge or preferences regarding script layout. OpenType layout fonts may even contain layout rules that duplicate or supersede those applied by OS services. The layered structure of OS services supporting text layout allows a client to choose which layout information to use, and how to apply it.