Parentheses don't display wth libertine/newtxmath and sansmath

Question

I'm trying to make an environment that uses sans-serif math by default inside the environment, but not outside of it. To do this I'm using the sansmath package.

The problem is that, when used with \usepackage[libertine]{newtxmath}

Here's an example:

\documentclass[10pt]{article}

\usepackage[tt=false, type1=true]{libertine}
\usepackage[libertine]{newtxmath} %works if I remove this
\usepackage{sansmath}


\begin{document}
$(0 + 1) + 2$

\begin{sansmath}
$(3 + 4) + 5$
\end{sansmath}
\end{document}

The non-sans part displays fine, but the brackets in the sans section don't show up at all. They do if I remove the newtxmath package.

Is there something I can do to get sansmath and libertine working together?

Answer 1

In Unicode Engines

In unicode-math, you can load Libertinus Math as your main math font, and another with version=sans. This cuts the Gordian knot of legacy 8-bit font encodings.

\documentclass[10pt]{article}
\usepackage{unicode-math}

\defaultfontfeatures{ Scale=MatchLowercase, Ligatures=TeX }

\setmainfont{Libertinus Serif}[Scale=1.0]
\setsansfont{Libertinus Sans}
\setmathfont{Libertinus Math}
\setmathfont{kpmath-sans}[version=sans]

\newenvironment{sansmath}{\mathversion{sans}}

\begin{document}
$(0 + 1) + 2$

\begin{sansmath}
$(3 + 4) + 5$
\end{sansmath}
\end{document}

In PDFTeX

You can try patching in the math alphabet from the newtxsf package.

\documentclass[10pt]{article}
\usepackage[T1]{fontenc}
\usepackage{libertinus}

\DeclareMathVersion{sans}
\SetSymbolFont{operators}{sans}{\encodingdefault}{\sfdefault}{m}{n}
\SetMathAlphabet{\mathit}{sans}{\encodingdefault}{\sfdefault}{m}{it}
\SetMathAlphabet{\mathsf}{sans}{\encodingdefault}{\sfdefault}{m}{n}
\SetMathAlphabet{\mathbf}{sans}{\encodingdefault}{\sfdefault}{b}{n}
\SetSymbolFont{letters}{sans}{OML}{ntxsfmi}{m}{it}
% \SetSymbolFont{lettersA}{sans}{U}{ntxsfmia}{m}{it}

\newenvironment{sansmath}{\mathversion{sans}}


\begin{document}
$(0 + 1) + 2$

\begin{sansmath}
$(3 + 4) + 5$
\end{sansmath}
\end{document}