[Tex/LaTex] Differences between LuaTeX, ConTeXt and XeTeX

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I’m interested in the differences and commonalities between the “new” (La)TeX processors:

Personally, I’ve only used XeTeX so far and without having the time to try out all three systems, I’m having a surprisingly hard time setting them off from one each other.

As I understand it, these systems are actually very different in some regards. So I’m explicitly asking for strengths and weaknesses in every-day use (whatever that is), rather than very special scenarios.

(I’ve already asked a similar question on Super User some time ago.)

Best Answer

Both LuaTeX and XeTeX are UTF-8 engines for processing TeX documents. This means that the input (.tex files) can contain characters that with pdfTeX are difficult to use directly. Both can also use system fonts, again in contrast to pdfTeX. However, the two are very different in approach.

XeTeX uses system-specific libraries to work. This means that it is very easy to use 'out of the box' for loading system fonts and other UTF-8 tasks. Indeed, it was written for this purpose: supporting languages, etc., that traditional TeX struggles with. This makes for an easy to use engine for end users, particularly if you use the fontspec package on LaTeX. However, because things are 'farmed out' to the OS, there is a trade-off in flexibility terms.

In contrast, LuaTeX has bigger aims. The idea is to add a scripting language (Lua) to TeX, and to open up the internals of TeX to this language. The result is that a lot is possible, but it has to be programmed in. There is growing LaTeX support for LuaTeX: fontspec v2 supports it, and new packages are being written to use more of the new features.

At the moment, I'd use XeTeX for UTF-8 and font support, unless I was after particular effects that only LuaTeX does well (Arabic typography is a particular challenge). The choice btween XeTeX and LuaTeX is 'tight': both have advantages depending on your exact requirements. (I'm on the LaTeX kernel team, so as a programmer I'm very keen on exploiting LuaTeX.)

ConTeXt is not an engine, and so is in a slightly different place here. ConTeXt is a format for TeX, like LaTeX, but is newer and much larger. ConTeXt Mark IV is a LuaTeX-only implementation. The people behind ConTeXt are very active in developing LuaTeX, and are using the new features to extend TeX and what ConTeXt can do. I've already pointed out that I'm working on LaTeX, so of course I'd like to see new features in LaTeX do the same. This is something I and the other members of the LaTeX project are working on.

Related Solutions

[Tex/LaTex] Drawbacks of XeTeX/LuaTeX

Math isn't the problem if you are happy with the "normal" math fonts used already by pdftex. This will work fine with xelatex + lualatex too. You can also try unicode-math but I don't know if it works in all cases.

The multilanguage support is more problematic: As you are using different scripts (greek, russian) you can't use babel (at least for this languages), as it will break the unicode font support. So you need polyglossia and this doesn't work with lualatex yet as it use (at least for some languages) xetex specific commands like \XeTeXinterclass. Also the support files of some of the languages (e.g. french) are much more sophisticated in the babel version. It is possible to mix babel + polyglossia but it depends a lot on the actual language combination if and how good it works.

Regarding the microtype support: The newest version of xetex can do protrusion (I haven't tried it yet), lualatex can protrusion + expansion. The author of microtype has just announced on c.t.t. that a preliminary version of microtype exists which supports both engines.
But at least for lualatex it isn't needed, one can activate both without problems manually:

 \documentclass[fontsize=12pt]{scrartcl}
  \pdfprotrudechars1
  \pdfadjustspacing1

 \usepackage{lipsum}
 \usepackage{fontspec}
 \newfontfeature{Microtype}{protrusion=default;expansion=default;}
 \setmainfont[Microtype,Ligatures=TeX]{Linux Libertine O}
 \begin{document}
 \lipsum
 \end{document}

[Tex/LaTex] Are XeTeX and LuaTeX platform dependent

LuaTeX OpenType support is fully implemented using Lua code (as Khaled wrote), which means that it is platform independent as long as identical font files are used.

But note that that is usually only the case for fonts that are part of a portable TeX distribution like TeXLive. LuaTeX also allows one to use system-installed fonts, and these will typically be a little different not only between competing operating systems, but also between different versions (or even updates) of one particular operating system.

LuaTeX uses no system font libraries, not for anything, not even fontconfig.

Anyway, LuaTeX documents should be platform independent if these conditions are met:

The underlying platform offers IEEE754 double precision floating point as well as 64-bit integer values (but without this, the luatex executable will probably not even compile. Neither will xetex, nor pdftex).
All used runtime (TeX, Lua, font, pattern, etc.) files are identical.
No Lua nor TeX code is used that explicitly does platform-dependent things.

The last point is what makes it hard to give a definitive answer. However, that condition exists for pdfTeX and even traditional TeX just the same. It is a bit more obvious in LuaTeX, but it is not at all hard to write platform-dependent documents in any of the other TeX- and TeX-like engines.

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[Tex/LaTex] Drawbacks of XeTeX/LuaTeX

[Tex/LaTex] Are XeTeX and LuaTeX platform dependent

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