When combining listings and JetBrains Mono * glyphs drop to the baseline (and are too big)

Question

Preparing a book where I use JetBrains Mono (Github Repo) (JBM) for code I noticed that in all the listings the * characters where rendered far to deep (on the baseline) and quite big. Also the *** ligature came out as three (fallen) * glyphs.

At this point JBM was declared as a new family:

\newfontfamily\JBMmdfamily{JetBrains Mono}[
  UprightFont    = *-Regular,
  ItalicFont     = *-Italic,
  BoldFont       = *-Bold,
  BoldItalicFont = *-BoldItalic
]

After fiddling around a bit I found that adding {*}{*}1 {***}{{***}}3 entries to a literate key in \lstset{} seemed to work. So I exchanged those characters by themselves which is funny but it works. Sort of. Looking closer I noticed that in the output spaces after those characters disappeared. Adding the keepspaces setting remedied that, so:

\lstset{
  keepspaces        = true,
%   showspaces        = false,
  literate  = {*}{*}1 {***}{{***}}3
}

(showspaces = truea lets other funny things happen but that is out of scope here.)

Later I noticed that just using

\setmonofont{JetBrains Mono}[…]

instead of

\newfontfamily\JBMmdfamily{JetBrains Mono}[…]

with the same body solved all those issues, no other \foo needed. I just don’t understand how that works. Someone care to explain?

My new problem now is, I need \texttt (etc.) to switch to the text typewriter type.

Here’s sort of a MWE:

    %!TEX TS-program = lualatex
\documentclass{article}
\usepackage{fontspec,listings}

\setmonofont{JetBrains Mono}[
  UprightFont    = *-Regular,
  ItalicFont     = *-Italic,
  BoldFont       = *-Bold,
  BoldItalicFont = *-BoldItalic,
]

\newfontfamily\JBMmdfamily{JetBrains Mono}[
  UprightFont    = *-Regular,
  ItalicFont     = *-Italic,
  BoldFont       = *-Bold,
  BoldItalicFont = *-BoldItalic,
]

\parskip=3mm
\parindent=0pt
\begin{document}

\subsection*{Both bindings seem to function:}

ttfamily:    {\ttfamily x*y * z + a *** b }

JBMmdfamily: {\JBMmdfamily x*y * z + a *** b }

\subsection*{listings needs either \textbackslash{}ttfamily:}
lstlisting/ttfamily:       \lstinline[basicstyle = \ttfamily]! x*y * z + a *** b !

lstlisting/JBMmdfamily: \lstinline[basicstyle = \JBMmdfamily]! x*y * z + a *** b !

\begin{lstlisting}[basicstyle = \ttfamily]
\ttfamily:     x*y * z + a *** b
\end{lstlisting}

\begin{lstlisting}[basicstyle = \JBMmdfamily]
\JBMmdfamily:  x*y * z + a *** b
\end{lstlisting}

\subsection*{… or keepspace \& literate:}
\lstset{
  keepspaces        = true,
  % showspaces        = true,
  literate  = {*}{*}1 {***}{{***}}3
}

lstlisting/ttfamily:       \lstinline[basicstyle = \ttfamily]! x*y * z + a *** b !

lstlisting/JBMmdfamily: \lstinline[basicstyle = \JBMmdfamily]! x*y * z + a *** b !

\begin{lstlisting}[basicstyle = \ttfamily]
\ttfamily:     x*y * z + a *** b
\end{lstlisting}

\begin{lstlisting}[basicstyle = \JBMmdfamily]
\JBMmdfamily:  x*y * z + a *** b
\end{lstlisting}

\end{document}

Any ideas? Thanks for all nudges and pointers …

Just corrected the source and added a picture of my result. There were a few errors, sorry for that.

Answer 1

The listings package uses \textasteriskcentered when it finds *; if the font has the character at U+2217, it uses it and, lo and behold, the character in the JetBrains Mono font at that slot is a lowered big asterisk. Unless the family is \ttdefault.

In the package we find

\lst@ProcessOther {"2A}{\lst@ttfamily*\textasteriskcentered}

which exactly means what I described above.

It turns out, however, that if the definition is changed to use \lst@ttfamily**, the ligature only works in \lstinline and not in a full fledged lstlisting environment (characters are treated in different ways). Thus literate is needed anyway.

Note: font selection is slightly different because I don't have the fonts available in the system, so I need to call them by file name.

\documentclass{article}
\usepackage{fontspec,listings}

\setmonofont{JetBrainsMono}[
  Extension      = .ttf,
  UprightFont    = *-Regular,
  ItalicFont     = *-Italic,
  BoldFont       = *-Bold,
  BoldItalicFont = *-Bold-Italic,
]

\newfontfamily\JBMmdfamily{JetBrainsMono}[
  Extension      = .ttf,
  UprightFont    = *-Regular,
  ItalicFont     = *-Italic,
  BoldFont       = *-Bold,
  BoldItalicFont = *-Bold-Italic,
]

\makeatletter
\lst@CCPutMacro\lst@ProcessOther{"2A}{\lst@ttfamily**}\@empty\z@\@empty
\makeatother

\lstset{
  keepspaces = true,
  % showspaces = true,
  % literate = {***}{{***}}3,
}

\begin{document}

The wrong character:{\ttfamily x\textasteriskcentered y}

\bigskip

ttfamily:    {\ttfamily x*y * z + a *** b }

JBMmdfamily: {\JBMmdfamily x*y * z + a *** b }


lstlisting/ttfamily:       \lstinline[basicstyle = \ttfamily]! x*y * z + a *** b !

lstlisting/JBMmdfamily: \lstinline[basicstyle = \JBMmdfamily]! x*y * z + a *** b !

\begin{lstlisting}[basicstyle = \ttfamily]
\ttfamily:     x*y * z + a *** b
\end{lstlisting}

\begin{lstlisting}[basicstyle = \JBMmdfamily]
\JBMmdfamily:      x*y * z + a *** b
\end{lstlisting}

\end{document}

Uncommenting the literate line yields, instead