# Copy theoremfont option from newtxtext

In Bringhurst it is suggested to use upright parentheses and punctuation in italic text.

The newtxtext packages allows for the option theoremfont which replaces figures, punctuation and parentheses in amsthm environments (which are my main source of italic text) by upright versions.

I would like to make use of this functionality, but I don't want to use newtx fonts. I tried looking into the package's source code and found the line \DeclareOption{theoremfont}{\ntx@thrmtrue}, but I can't seem to find where and how this boolean is used.

I was asked to include a MWE, however I don't have much to include. Here is an example of a theorem which should be changed quite drastically:

\documentclass{article}

\usepackage{amsthm}

\theoremstyle{plain}
\newtheorem{theorem}{Theorem}

\begin{document}
\begin{theorem}
At theorem with [brackets], \{braces\}, (parentheses), 1 or 2 numbers, and some punctuation\ldots!
\end{theorem}
\end{document}

Workaround:

\documentclass{article}

\usepackage{embrac}

\usepackage{amsthm}
\newtheorem{theorem}{Theorem}

\usepackage{embrac}

\newtheoremstyle{plain}
{\topsep}   % ABOVESPACE
{\topsep}   % BELOWSPACE
{}       % BODYFONT
{0pt}       % INDENT (empty value is the same as 0pt)