XeTeX
XeTeX, by Jonathan Kew, is a
successor to the shareware TeX/GX program for Macintoshes. It was
developed as a WEB ‘change file’ applied to the original source
of TeX; the main changes include:
- The input stage
- XeTeX by default reads Unicode (UTF-8, for
instance), although it’s also capable of interpreting differently
encoded files (for backwards compatibility). Multibyte characters
are reduced to a single internal character upon reading, so they are
considered as a unique entity when tokenization is performed. (So,
for example, you can have command names in cyrillic, if you must,
but such a practice is not recommended.)
- The font management
- a substantial revision has added support
for OpenType and TrueType fonts, delegating some parts to
third-party libraries.
- The maths font set up
- XeTeX introduces new primitives for
extending the
\mathcode and \mathchardef commands in TeX,
allowing the user to specify characters in the whole Unicode set and
in 256 ‘math families’ (TeX only has 16, which limits some maths
coding techniques).
- “Post-processing” features (A)
- XeTeX links to the
teckit library so it can apply a
map file
that allows transformation of characters in already formed token
lists, before they are processed in the “stomach” for typesetting.
In this way, a declaration “Ligatures=TeX” is provided,
which attaches a map directive to the font that transforms the
character combinations (familiar to TeX users) into a single
character; for instance --- is transformed into
“—”.
- “Post-processing” features (B)
- Characters can be assigned to
an “interchar token class” and it is possible to specify tokens to
be added when there is a transition from one class to another. The
packages polyglossia, xeCJK and
ucharclasses exploit this feature.
Otherwise, the process of typesetting is essentially the same as
TeX’s. (However some changes have also been made in the
hyphenation stage that may give slightly different results if the same
document is compiled with PDFTeX or XeTeX.)
- polyglossia.sty
- polyglossia
- xeCJK.sty
- xecjk
- ucharclasses.sty
- ucharclasses
This answer last edited: 2013-02-21
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