Is it possible to combine version and range when specifying a maths font with unicode-math?

Question

[Note that I am using LuaTeX for all compilations.]

Consider the following MWE which sets up several versions for maths using unicode-math's version key.

\documentclass{article}
\usepackage[math-style=TeX]{unicode-math}
\setmathfont{Latin Modern Math}
\setmathfont{Latin Modern Math}[version=lm]% sanity check
\setmathfont{Asana Math}[version=asana]
\setmathfont{TeX Gyre Schola Math}[version=tgs]
\setmathfont{Tex Gyre Termes Math}[version=tgt]
% \setmathfont{Tex Gyre Schola Math}[version=tgs, range=it]
% \setmathfont{Tex Gyre Termes Math}[version=tgt]
\newcommand*\testmaths{%
\begin{equation}
  \int_{t = 0}^{x^2} t dt
\end{equation}
\[
  \sin^2{\theta} + \cos^2{\theta} = 1
\]
}
\begin{document}
Latin Modern Math (\verb|normal|):
\testmaths

\mathversion{asana}
Asana Math (\verb|asana|):
\testmaths

\mathversion{tgt}
TeX Gyre Termes Math (\verb|tgt|):
\testmaths

\mathversion{normal}
Latin Modern Math (\verb|normal|):
\testmaths

{%
  \mathversion{tgs}
  TeX Gyre Schola Math (\verb|tgs|):
  \testmaths
}

Latin Modern Math (\verb|normal|):
\testmaths

\mathversion{lm}
Latin Modern Math (\verb|lm|):
\testmaths
\end{document}

This works fine.

However, this code cannot be combined with the use of range. Although the effect of range is to restrict the specified font to the given range, its use is not then restricted to the specified version. Instead, all versions are affected.

% \setmathfont{TeX Gyre Schola Math}[version=tgs]
\setmathfont{Tex Gyre Termes Math}[version=tgt]
\setmathfont{Tex Gyre Schola Math}[version=tgs, range=it]
% \setmathfont{Tex Gyre Termes Math}[version=tgt]

Or, changing the order, the specified range in the specified version simply ends up producing emptiness.

% \setmathfont{TeX Gyre Schola Math}[version=tgs]
% \setmathfont{Tex Gyre Termes Math}[version=tgt]
\setmathfont{Tex Gyre Schola Math}[version=tgs, range=it]
\setmathfont{Tex Gyre Termes Math}[version=tgt]

Why is this and can it be corrected?

EDIT

It is, of course, true that the above examples are incomplete because they do not define sufficient stuff for an alternative maths version. To do this, additional configuration would be required to ensure that all ranges are set for the alternative maths version(s). However, this cannot be done unless a single font is used for all ranges for a given version. This is quite unlike the standard case, where you must use multiple fonts to ensure complete coverage.

Here's a non-LuaTeX example using various fonts from Arev. The commands are mostly from arevmath.sty. Note that the macros are, essentially, each setting a relevant range for the new version, sansserif. (Even here, things are not really complete: there are symbols and maths alphabets to worry about. But hopefully the basic idea is clear.)

\documentclass{article}
\usepackage{lmodern}
\DeclareMathVersion{sansserif}
% modified from arev - node that a complete set up would need additional stuff
\SetSymbolFont{operators}    {sansserif}{OT1}{zavm}{m}{n}
\SetSymbolFont{letters}      {sansserif}{OML}{zavm}{m}{it}
\SetSymbolFont{symbols}      {sansserif}{OMS}{zavm}{m}{n}
\SetSymbolFont{largesymbols} {sansserif}{OMX}{mdbch}{m}{n}
\SetMathAlphabet{\mathnormal}{sansserif}{OML}{zavm}{m}{it}
\SetMathAlphabet{\mathit}    {sansserif}{OML}{zavm}{m}{it}
\SetMathAlphabet{\mathrm}    {sansserif}{OT1}{zavm}{m}{n}
\SetMathAlphabet{\mathsf}    {sansserif}{OML}{zavm}{m}{it}
\SetMathAlphabet{\mathbf}    {sansserif}{OT1}{zavm}{b}{n}
\SetMathAlphabet{\mathtt}    {sansserif}{T1} {fvm} {m}{n}
\newcommand*\testmaths{%
\begin{equation}
  \int_{t = 0}^{x^2} t dt
\end{equation}
\[
  \sin^2{\theta} + \cos^2{\theta} = 1
\]
}
\begin{document}
Latin Modern Math (\verb|normal|):
\testmaths

\mathversion{sansserif}
Arev (\verb|sansserif|):
\testmaths

\mathversion{normal}
Latin Modern Math (\verb|normal|):
\testmaths
\end{document}

The question is how to do the equivalent with unicode-math if you want letters to come from one maths font, say, and operators from another.

Answer 1

Imho the answer to the question is "no". Currently it won't work. unicode-math implements the range option by defining a new math family and then points the symbol(s) to this family. The code is not "version aware".

\documentclass{article}
\usepackage[math-style=TeX]{unicode-math}

\begin{document}
$ a $
[class: \Umathcharclass`\a]
[family: \Umathcharfam`\a]
[slot: \Umathcharslot`\a]


\setmathfont{Tex Gyre Schola Math}[range="61]

$ a $
[class: \Umathcharclass`\a]
[family: \Umathcharfam`\a]
[slot: \Umathcharslot`\a]

\setmathfont{Tex Gyre Termes Math}[range="61]

$ a $
[class: \Umathcharclass`\a]
[family: \Umathcharfam`\a]
[slot: \Umathcharslot`\a]

\end{document}

It would be quite difficult to change this -- on the technical side but also regarding the "logic". unicode-math would have to either store long list of symbols which should be remapped to other fonts if the mathversion change, or remap math fonts and in both case it would have to pay attention to varying range blocks in the various math version versions -- a nightmare for a maintainer.

While I do understand that people like to change (or add) glyphs in a math font I think that the range option should be used with care and not for large scale font manipulations. Imho the future for complicated setups lies not in more unicode-math code but in the "combo" font feature of luaotfload.