[XeTeX] Fontspec bug?

[Bruno Voisin]

I just tried to convert a document of mine using bare-bones XeLaTeX  
font selection of the form:

> \usepackage[LY1]{fontenc}
> \usepackage[expert,lucidasmallscale]{lucidabr}
>
> \DeclareFontFamily{U}{hoeflertext}{}
> \DeclareFontShape{U}{hoeflertext}{m}{n}
>   {<-> "Hoefler\space Text:mapping=tex-text;
>           Number\space Case=Upper\space Case\space Numbers
>        "}{}
> \DeclareFontShape{U}{hoeflertext}{m}{it}
>   {<-> "Hoefler\space Text\space Italic:mapping=tex-text;
>           Number\space Case=Uppercase\space Numbers;
>           Smart\space Swashes=!Line\space Final\space Swashes,
>                               !Line\space Initial\space Swashes
>        "}{}
> [...]
> \renewcommand{\encodingdefault}{U}
> \renewcommand{\rmdefault}{hoeflertext}
>
> \SetSymbolFont{operators}{normal}{\encodingdefault}{\rmdefault}{m}{n}
> \SetSymbolFont{operators}{bold}  {\encodingdefault}{\rmdefault}{b}{n}
> \SetMathAlphabet{\mathrm}{normal}{\encodingdefault}{\rmdefault}{m}{n}
> \SetMathAlphabet{\mathbf}{normal}{\encodingdefault}{\rmdefault}{b}{n}
> \SetMathAlphabet{\mathit}{normal}{\encodingdefault}{\rmdefault}{m}{it}
> \SetMathAlphabet{\mathrm}{bold}  {\encodingdefault}{\rmdefault}{b}{n}
> \SetMathAlphabet{\mathit}{bold}  {\encodingdefault}{\rmdefault}{b}{it}

to font selection using the fontspec package:

> \usepackage[LY1]{fontenc}
> \usepackage[expert,lucidasmallscale]{lucidabr}
>
> \usepackage{fontspec}
> \defaultfontfeatures{%
>   Mapping=tex-text,
>   Numbers={Lining},
>   Contextuals={NoLineInitial,NoLineFinal}
>   }
> \setromanfont{Hoefler Text}

No need to emphasize the convenience of the second approach!

However, looking more closely I noticed numbers in math formulae are  
typeset in Hoefler Text as intended in the first case (thanks to the  
redefinition of the operators font, see \DeclareMathSymbol{0} 
{\mathalpha}{operators}{`0} etc. in /usr/local/teTeX/share/ 
texmf.tetex/tex/latex/base/fontmath.ltx), but in Computer Modern when  
using fontspec (v1.9).

It seems the culprit is line 936 of fontspec.sty, which instead of

     \ifzf at math@lucida

should read

     \ifzf at math@lucida\else

so that the whole stuff becomes

\def\zf at rmmaths{\rmdefault}
[...]
   \@ifpackageloaded{lucbmath}{\zf at math@lucidatrue}{}
   \@ifpackageloaded{lucidabr}{\zf at math@lucidatrue}{}
   \DeclareSymbolFont{legacymaths}{OT1}{cmr}{m}{n}
   [...]
   \ifzf at math@euler\else
     [...]
     \ifzf at math@lucida\else
       \DeclareMathSymbol{0}{\mathalpha}{legacymaths}{`0}
       [...]
     \fi
   \fi
   \DeclareSymbolFont{operators}\zf at enc\zf at rmmaths\mddefault\updefault
   \SetSymbolFont{operators}{normal}\zf at enc\zf at rmmaths\mddefault 
\updefault

implying that the operators font (by default \zf at rmmaths = \rmdefault  
= (here) Hoefler Text) is used for numbers in maths when Lucida is  
used and the legacymaths font (i.e. CMR) otherwise.

However, even in this case I'm not quite certain that the use of  
Lucida should dictate whether or not the text font (not necessarily  
Lucida, for example here) is used for typesetting numbers in maths  
mode. I remember the introduction of the legacymaths mechanism in  
fontspec resulted from the use of the operators font for some  
diacritics in LaTeX by default, but I must admit I don't remember the  
whole story.

Bruno Voisin