Math version with "non-math font" besides unicode-math package

Question

I am writing a document which is mostly typeset with the STIX TWO fonts and compiled via XeLaTeX. Math mode is configured via unicode-math.

In certain contexts, I need an Arial/Helvetica/Tex Gyre Heros type sans-serif font. (It's ok if these sections come out a bit rugged, i.e. the missing scshape is no problem at all. I want to manually annotate diagrams which are itself set in Arial.)

For the normal text font, I set up a newfontface. Now I want to do the same for the math font, which I tried to achieve by defining a dedicated mathversion. Unfortunately this blocks the use of unicode-math range parameters, as range and version do not play well together.

As there is no such math font (using Fira Math compiles, but it looks quite different from Arial), I tried to use NFSS commands for that version definition.

Eventually, this fails with:

LaTeX Font Warning: Font shape `TU/Arial/m/n' undefined
(Font)              using `TU/lmr/m/n' instead on input line 29.

! Math formula deleted: Insufficient symbol fonts.
\resetMathstrut@ ->\setbox \z@ \hbox {$($
                                         }\ht \Mathstrutbox@ \ht \z@ \dp \Ma...
l.29 \begin{equation}

I put together a minimal example that demonstrates my problem:

\documentclass[english]{scrartcl}
\usepackage[math-style=ISO, bold-style=ISO]{unicode-math}

\defaultfontfeatures{Scale = MatchUppercase}
\setmainfont[Scale=0.97]{STIX Two Text}
\setmathfont[Scale=0.97]{STIX Two Math}
\setsansfont[Scale=1.07]{Libertinus Sans}

\newfontface\rootsans{Arial}
%\setmathfont[version=rootsans]{Fira Math} % <-- This works but Fira!=Arial

\DeclareMathVersion{rootsans} %<-- Tried an alternative approach, so far without success
\SetSymbolFont{letters}{rootsans}{TU}{Arial}{m}{n}
\SetSymbolFont{operators}{rootsans}{TU}{Arial}{m}{n}
\SetSymbolFont{symbols}{rootsans}{TU}{Arial}{m}{n}
\SetSymbolFont{largesymbols}{rootsans}{TU}{Arial}{m}{n}
\SetMathAlphabet{\mathrm}{rootsans}{TU}{Arial}{m}{n}

\begin{document}

\textsc{Euler}'s identity in normal mode:
\begin{equation}
e^{i\phi} + 1 = 0
\end{equation}

\rootsans
\mathversion{rootsans}
\textsc{Euler}'s identity with special font setting: 
\begin{equation}
e^{i\phi} + 1 = 0
\end{equation}
\end{document}

If I omit the mathversion everything works, but equation (2) does not match its the preceding line.

Is there anything I can do or do I have to live with Fira Math as Arial companion?

Answer 1

Not quite clear how you want to use text mode as if it were math mode (if I understand correctly), but you would have to do layout "by hand", or create a set of "text as math" commands with \setmathfontface (regular, italic, bold, etc).

Here, version with Noto Sans Math, and Fira Math; and by-hand Arial (which does not have dedicated mathematical Unicode blocks but luckily has Greek and Latin in it as text).

Note that 𝑒 (U+1D452 MATHEMATICAL ITALIC SMALL E) is not the same as a text roman e rendered in an italic face. Likewise with the sans 𝘦 (`U+1D626 MATHEMATICAL SANS-SERIF ITALIC SMALL E).

MWE

\documentclass{scrartcl}
\usepackage{xcolor}
\usepackage[math-style=ISO, bold-style=ISO]{unicode-math}

\defaultfontfeatures{Scale = MatchUppercase}
\setmathfont[Scale=0.97]{STIX Two Math}
\setmainfont[Scale=0.97]{STIX Two Text}
\setsansfont[Scale=1.07]{Libertinus Sans}
%\setmathfontface{\textm}[Scale=0.97]{Arial} % regular face

\newfontfamily\mysans{Arial}
\setmathfont[version=rootsans,Colour=blue]{Noto Sans Math} %
\setmathfont[version=rootsansb,Colour=red]{Fira Math} %


\begin{document}

\textsc{Euler}'s identity in normal mode:
\begin{equation}
e^{i\phi} + 1 = 0
\end{equation}

%\rootsans
\mathversion{rootsans}
\textsc{Euler}'s identity with special font setting (Noto Sans Math): 
\begin{equation}
e^{i\phi} + 1 = 0
\end{equation}


\mathversion{rootsansb}
\textsc{Euler}'s identity with special font setting (Fira Math): 
\begin{equation}
e^{i\phi} + 1 = 0
\end{equation}

{\mysans This is Arial: \textit{e\textsuperscript{iφ}} + 1 = 0}

\end{document}

---

Edit

There are various ways of accessing the alphabets in a math font (here, STIX Two Math)...

... and for a 'text as math' font which is not a math font (here, Arial), the input argument needs to be ordinary text (typeset from an italic face), not a mathematical symbol, i.e., φ (U+03C6 GREEK SMALL LETTER PHI) or ϕ (U+03D5 GREEK PHI SYMBOL) depending in the typeface, not 𝜙 (U+1D719 MATHEMATICAL ITALIC PHI SYMBOL).

MWE

\documentclass{article}
\usepackage{xcolor}
\usepackage[math-style=ISO, bold-style=ISO]{unicode-math}

\defaultfontfeatures{Scale = MatchUppercase}
\setmathfont[Scale=0.97]{STIX Two Math}
\setmainfont[Scale=0.97]{STIX Two Text}


\setmathfontface{\textarial}[Colour=red,Scale=0.97]{arial.ttf} 
\setmathfontface{\textariali}[Colour=red,Scale=0.97]{ariali.ttf} 

\begin{document}

Default: e $\mapsto e$

\begin{equation}
e^{i\phi} + 1 = 0
\end{equation}

Direct input: $𝘦𝘪𝜙𝟣𝟢$

\begin{equation}
𝘦^{𝘪𝜙} + 𝟣 = 𝟢
\end{equation}

\texttt{\textbackslash sym...} command: \textbackslash symsfit\{e\} $\mapsto \symsfit{e}$

\begin{equation}
\symsfit{e}^{\symsfit{i}\symsfit{\phi}} + \symsf{1} = \symsf{0}
\end{equation}

Named macros\footnote{See ...texmf-dist/tex/latex/unicode-math/unicode-math-table.tex}: \textbackslash mitsanse $\mapsto \mitsanse$

\begin{equation}
\mitsanse^{\mitsansi\mitphi} + \msansone = \msanszero
\end{equation}

\setmathfont{STIX Two Math}[Scale=0.97,range={sfit/latin,it/greek,sfup/num},Colour=blue]

\texttt{range=} option: \texttt{[range=\{sfit/latin,it/greek,sfup/num\}]}

\begin{equation}
\symsfit{e}^{\symsfit{i}\phi} + \symsfup{1} = \symsfup{0}
\end{equation}

`text as math' font (here, ϕ = U+03D5, text Greek):


\begin{equation}
\textariali{e}^{\textariali{i}\textariali{ϕ}} + \textarial{1} = \textarial{0}
\end{equation}


\end{document}