Différences

Ci-dessous, les différences entre deux révisions de la page.

--- generalites:glossaire:xetex_et_luatex [2018/06/03 10:03] – d.p.carlisle
+++ 1_generalites:glossaire:xetex_et_luatex [2021/03/20 13:05] (Version actuelle) – Suppression de la page désormais inutile. yannick.tanguy
@@ Ligne 1: / Ligne 1: @@
----
-title: What are XeTeX and LuaTeX?
-category: background
-tags:
-  - xetex
-  - luatex
-permalink: /FAQ-xetex-luatex
-date: 2018-05-25
-redirect_from:
- - /FAQ-luatex
- - /FAQ-xetex
----
-The standard [pdfTeX](FAQ-pdftex) engine is fully backward-compatible with
-Knuth's TeX. As such, it remains an 8-bit system using specialist [font
-metrics](FAQ-tfm). In contrast, the engines XeTeX and LuaTeX are both
-Unicode-based and able to load standard system (OpenType) fonts. Internally,
-they differ in approach: the same outcomes are reached using very different
-philosophies. There are advantages to the user in each approach.
-[XeTeX](http://scripts.sil.org/xetex) is a Unicode TeX engine which can load
-system fonts directly using the HarfBuzz library, which is built in. To do
-this, the `\font` primitive is extended. In order to support these major
-concepts, a range of TeX primitives are extended. For most LaTeX end users,
-these subtleties are transparent, with the LaTeX kernel and
-[`fontspec`](https://ctan.org/pkg/fontspec) package providing interfaces.
-Like Knuth's TeX, it does not directly produce PDF output but rather works
-_via_ an intermediate format, XDV (eXtended DVI). Unlike the classical
-[DVI](FAQ-dvi) format produced by TeX, XDV files cannot be viewed directly, and
-are normally converted directly to PDF as part of the `xetex` run. (The
-conversion itself is carried out by `xdvpdfmx`.)
-LuaTeX consists of a TeX-like engine with a Lua interpreter "embedded" in it;
-the Lua interpreter has access to many of the data structures used for
-typesetting, so that the programmer may also interpolate chunks of Lua code
-into their (La)TeX macros, or as "call-backs" for use when the TeX-like
-engine does certain operations.
-LuaTeX, like [XeTeX](FAQ-xetex), is a Unicode engine and is capable of loading
-system fonts. In contrast to XeTeX, the latter ability is not "built-in" to
-the engine itself, but is added using Lua code. This possibility to modify the
-behaviour of the engine at the "user" end makes it particularly powerful.
-Whilst there are some (deliberate) differences between the behavior of LuaTeX
-and that of Knuth's TeX (or [pdfTeX](FAQ-pdftex)), for most users, LuaTeX may
-be used as a drop-in replacement. For most LaTeX end users, the subtleties are
-transparent, with the LaTeX kernel and
-[`fontspec`](https://ctan.org/pkg/fontspec) package providing interfaces.
-[ConTeXt](FAQ-context) Mark&nbsp;4 (the current version) _requires_ LuaTeX:
-this is again transparent to users.