[XeTeX] fontspec 1.5 (& Lucida Math)

[Bruno Voisin]

Herb Schulz wrote:

> Actually, the lucbmath package gives me terrible trouble in even a simple
> document. My problem with \Gamma is with no math package! Try this:
> 
> %&program=xelatex
> %&encoding=UTF-8 Unicode
> % Basic XeLaTeX Document
> \documentclass{article}
> 
> \usepackage{fontspec}
> \setromanfont{Hoefler Text}
> 
> \begin{document}
> 
> Here is an Upper Case Gamma: \(\Gamma\)!
> 
> \end{document}
> 
> I get no \Gamma displayed.

In short: it's all my fault!

That's because in standard LaTeX, with the default OT1 encoding, as defined by /usr/local/teTeX/share/texmf.tetex/tex/latex/base/fontmath.ltx, \Gamma is taken from the "operators" font which is the text font CMR (the same is also true, actually, of plain TeX):

	\DeclareSymbolFont{operators}   {OT1}{cmr} {m}{n}
	
	\DeclareMathSymbol{\Gamma}{\mathalpha}{operators}{"00}

But fontspec.sty redefines this font as Hoefler Text which has no Gamma symbol:

	\AtBeginDocument
	  {
	   \SetSymbolFont{operators}{normal}\zf at enc\rmdefault\mddefault\updefault

I hadn't noticed this because with Lucida fonts, in lucidabr.sty, \Gamma is taken from other fonts which are not redefined to Hoefler Text, namely "mathupright" (= hlcm = LBMA = Math-Arrows) for the expert set or "largesymbols" (= hlcv = LBME = Math-Extension) for the non-expert set:

	\iflucida at expert
	 \DeclareSymbolFont{mathupright}{OML}{hlcm}{m}{n}
	\fi
	 [...]

	\iflucida at expert
	  \DeclareMathSymbol{\Gamma}{\mathord}{mathupright}{0}
	  [...]
	\else
	  \DeclareMathSymbol{\Gamma}{\mathord}{largesymbols}{'320}

And because Will had used my code as the basis for some of his, he hadn't noticed either.

This is the result of the idiosyncrasies of TeX, of its 7-bit inheritance, such that the capital Greek letters are taken from the main text font. The only fix I could think of is to add a new math symbol font for just containing these symbols:

	\DeclareSymbolFont{xoperators}   {OT1}{cmr} {m}{n}
	
	\DeclareMathSymbol{\Gamma}{\mathalpha}{xoperators}{"00}

etc., but that wouldn't work outside standard LaTeX, for example with Lucida fonts (the capital Greek letters would be taken from Computer Modern instead of Lucida).

In any case:

	%&program=xelatex
	%&encoding=UTF-8 Unicode
	% Basic XeLaTeX Document
	\documentclass{article}

	\usepackage{fontspec}
	\setromanfont{Hoefler Text}

	\begin{document}

	Here is an Upper Case Gamma: $\Gamma$!

	\end{document}

doesn't work, but


	%&program=xelatex
	%&encoding=UTF-8 Unicode
	% Basic XeLaTeX Document
	\documentclass{article}

	\usepackage[T1]{fontenc}
	\usepackage{lucidabr}

	\usepackage{fontspec}
	\setromanfont{Hoefler Text}

	\begin{document}

	Here is an Upper Case Gamma: $\Gamma$!

	\end{document}

does.

Bruno