Better support for non-ASCII characters when LuaLaTeX or XeLaTeX is used?

[nad]

The fonts chosen by acmart have little support for non-ASCII characters when LuaLaTeX or XeLaTeX is used. For instance, consider the following UTF8-encoded file:

\documentclass{acmart}

\tracinglostchars=2

\begin{document}

$a^2$ ∀ $∀$ $\forall$

\end{document}

If I process this file using lualatex, then the following warnings are printed:

Missing character: There is no ∀ (U+2200) in font LinLibertineT-tlf-ot1!
Missing character: There is no ∀ (U+2200) in font LinLibertineT-tlf-t1!

With xelatex I get the following warnings:

Missing character: There is no ∀ in font LinLibertineT-tlf-t1!
Missing character: There is no ∀ in font LinLibertineT-tlf-ot1!

The problem can be partially fixed by using fontspec:

\usepackage[no-math]{fontspec}
\setmainfont{Linux Libertine O}

Now the first occurrence of ∀ is typeset, but not the second one. If I remove the no-math option, then the second occurrence is also typeset, but not in the same way as $\forall$, and the digit 2 is also typeset in a different way.

Is there some way to use fontspec (and perhaps unicode-math) to provide support for a large set of additional characters, without changing the appearance of characters that are currently supported?

[bracevac]

One solution: Consider using the libertinus font package, which fixes bugs in Libertine and adds a proper math font version compatible with unicode-math. You will need to change the corresponding lines in acmart.sty of course.

@borisveytsman
I wonder if the ACM would consider using the libertinus package instead of libertine+newtxmath (or at least add a package option).
That would make xetex/luatex/unicode-math users happy.

I would love to write conference papers with unicode-math, but only if there is no technical obstacle in ACM's publication processes. E.g., would it work to submit a camera ready based
on a custom acmart that just swaps the font? The fonts are practically identical, but the embedded font names might differ.

[arthuraa]

It would be great to see unicode-math supported properly in acmart. I've already had a few issues preparing camera-ready versions to circumvent this limitation.

[rionda]

+1. Better support for Lua and unicode-math would be a good idea.

[Blaisorblade]

Filed #398 on the libertinus switch, hoping it'll get more attention.