mathversion and bold symbols

[stone-zeng]

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Description

Now ExtraBold, Heavy, Ultra in Fira Math do not have bold symbols (U+1D400 etc).

If using several weights containing the above ones, for example, Thin+Ultra, then when set \mathversion for them, the bold symbols of the normal weights (Thin in the example) will disappear.

Check/indicate

• [x] Relevant for XeTeX
• [x] Relevant for LuaTeX
• [ ] Issue tracker has been searched for similar issues?
• [ ] Links to <tex.stackexchange.com> discussion if appropriate

Minimal example demonstrating the issue

\documentclass{article}
\usepackage{amsmath,unicode-math}
\setmathfont{FiraMath-Thin.otf}[version=Thin]
\setmathfont{FiraMath-Regular.otf}[version=Regular]
% \setmathfont{FiraMath-Ultra.otf}[version=Ultra]

\begin{document}
\mathversion{Thin}    $ ABC abc \symbf{abc} $ \par
\mathversion{Regular} $ ABC abc \symbf{abc} $ \par
% \mathversion{Ultra}   $ ABC abc \symbf{abc} $ \par
\end{document}

If uncomment the Ultra lines, then the bold symbols of Thin and Regular disappear:

Further details

The only other math font that contains multiple weights is (as far as I know) is XITS Math Bold. But it uses the same glyphs as normal weights for the bold weights (U+1D400 is the same as U+0041). So should I create the mapping in Fira Math Ultra etc as in XITS Math Bold?

[wspr]

Interesting (albeit problematic!). Thanks for the nice test case.

The math version implementation has always had its problems; I think the \symXX commands need a lot more work to hook in correctly with the math versions.

Unfortunately I can’t promise a timely fix at the moment, it’s a busy time of year...