\boldmath with unicode-math AND fonts with a MATH table

Question

There are several questions on this site about \boldmath with unicode-math. As Example 1 below shows, \boldmath does not in general work for unicode fonts with a MATH table, unless there is a specific bold version of the math font. So far, I have not found one for any fonts except XITS Math; from what I have heard, Lucida has one, too, but it is not free. How can I set the \boldmath font with unicode-math? provides an ugly solution that only works for XeLaTeX. Since I am using LuaLaTeX, I am looking for something else (and prettier).

Bold italic math with unicode-math contains a solution to get it to work using unicode fonts without a proper MATH table. The solution also works for fonts with a proper MATH table, provided you replace the math font with the italic text font (see Example 2). As the example shows, the accent (\hat) does not look good in this case.

So the preferable solution would be:

• Ordinary, non-bold math should be typeset using TeX Gyre Pagella Math
• \boldmath math should be typeset using the bold italic text font TeX Gyre Pagella Bold Italic

I tried that in Example 3 below, but it seems text and math fonts do not work together in this case, for integral signs and everything else break.

Finally, I tried in Example 4 to play around with version=bold, but curiously, this makes all math bold. Is this a bug?

Can someone get this to work for me?

% !TeX program=luatex
\documentclass{article}

\usepackage{fontspec,amsmath}

\setmainfont[Ligatures=TeX]{TeX Gyre Pagella}

\usepackage{unicode-math}

\newcommand\mytest{
    \[ \hat f(t) = \int_0^t \hat f'(x)\, dx \]
    {\boldmath \[ \hat f(t) = \int_0^t \hat f'(x)\, dx \]}
}

\begin{document}

Example 1:

\setmathfont{TeX Gyre Pagella Math}

\mytest

Example 2:

\setmathfont{TeX Gyre Pagella Math}

\setmathfont[
   range=\mathit/{latin,Latin,greek,Greek,num},
   BoldFont=TeX Gyre Pagella Bold Italic
]{TeX Gyre Pagella Italic}

\mytest

Example 3:

\setmathfont[BoldFont=TeX Gyre Pagella Bold Italic]{TeX Gyre Pagella Math}

\mytest

Example 4:

\setmathfont{TeX Gyre Pagella Math}
\setmathfont[
     version=bold,
     range=\mathit/{latin,Latin,greek,Greek,num}
]{TeX Gyre Pagella Bold Italic}

\mytest

\end{document}

Answer 1

Well the logical solution is to setup a new math version, which should be independant from the normal math version.

But imho there is today not much chance to get the version key working in your use case. As long as only real math fonts are involved it works fine, but in the combination with range and text fonts it is buggy as one math version affects the other.

Currently I would implement a bold mathversion by embolden a real math font. In xelatex this can be done with FakeBold and version (as long as no other text fonts are involved). In lualatex you could use a pdfliteral:

\documentclass{article}
\usepackage{fontspec,amsmath}
\setmainfont[Ligatures=TeX]{TeX Gyre Pagella}
\usepackage{unicode-math}
\setmathfont{TeX Gyre Pagella Math}

\begin{document}

\[ \hat f(t) = \int_0^t \hat f'(x)\, dx \]

\pdfliteral direct {2 Tr 0.2 w} %the second factor is the boldness

\[ \hat f(t) = \int_0^t \hat f'(x)\, dx \]

\pdfliteral direct {0 Tr 0 w}%

\end{document}

Answer 2

Unicode has defined the bold and bold italic (and others) mathematical alphanumeric characters covering latin, greek, and digit characters, so they are already included in an conforming OpenType mathematical font.

Here is an example using the bold range:

\documentclass{article}
\usepackage{fontspec,amsmath}
\usepackage{unicode-math}
\setmainfont[Ligatures=TeX]{TeX Gyre Pagella}
\setmathfont{TeX Gyre Pagella Math}
\begin{document}
\[
  \hat f(t) = \int_0^t \hat f'(x)\, dx
\]
\[
  \mathbf{\hat f}(t) = \int_0^t \mathbf{\hat f}'(x)\, dx
\]
\end{document}

A couple of notes. I remember there being an issue with accents with single-atom elements which can be fixed by prefixing the atom to be accented with an empty group (so, for example, \hat{{}f}, if need be).

Also, whether or not the bolded alphabets are in italic, can be determined by – according to the unicode-math documentation – the bold-style=ISO configuration option.

Answer 3

Here is a solution that gets “\boldmath to automatically activate bold italic math,” as desired. It necessarily relies, however, as Ulrike Fischer mentioned on the presence of a “real bold math font.” (Hence, it cannot be achieved with TeX Gyre Pagella Math, because there is no TeX Gyre Pagella Math Bold, as already pointed out by egreg.)

To my knowledge, currently (September 2, 2022) only five such fonts exist:

1. the open-source font XITSMath-Bold.otf (already mentioned in the comments, included in the standard TeX distributions, and used in my solution),
2. the commercial font Minion Math (which even comes in four weights),
3. the commercial font Lucida Bright,
4. the open-source font Fira Math (wich comes in as many as 12 weights but as of today has rather incomplete glyph coverage), and
5. the open-source KpMath font (which is included in the standard TeX distributions via the kpfonts-otf package and even comes in four weights plus a sans-serif version).

% !TEX program = xelatex


\documentclass{minimal}


\usepackage{ifthen}
\usepackage[svgnames]{xcolor}

\usepackage[
   mathit = sym, mathup = sym, mathbf = sym,
   math-style = ISO, bold-style = ISO
]{unicode-math}

\setmainfont{LinLibertine_R.otf}[
   ItalicFont = LinLibertine_RI.otf,
   BoldFont = LinLibertine_RB.otf,
   BoldItalicFont = LinLibertine_RBI.otf
]
\setmonofont{FiraMono-Medium.otf}[
   Scale = 0.81,
   Color = DarkBlue
]

\setmathfont{XITSMath-Regular.otf}[
   BoldFont = XITSMath-Bold.otf
]
\setmathfont{XITSMath-Regular.otf}[
   version = mathitVersion
]
\setmathfont{XITSMath-Regular.otf}[
   version = mathbfitVersion
]
\setmathfont{XITSMath-Bold.otf}[
   version = boldmathVersion
]

\setmathfont{LinLibertine_R.otf}[
   range = up/{num, latin, Latin, greek, Greek},
   BoldFont = LinLibertine_RB.otf
]
\setmathfont{LinLibertine_RI.otf}[
   range = it/{num, latin, Latin, greek, Greek},
   BoldFont = LinLibertine_RBI.otf,
   NFSSFamily = mathitalic
]
\setmathfont{LinLibertine_RBI.otf}[
   range = bfit/{latin, Latin, greek, Greek},
   NFSSFamily = mathbolditalic
]
\setmathfont{LinLibertine_RB.otf}[
   range = bfup/{num, latin, Latin, greek, Greek}
]

\newif \ifBoldMath \BoldMathfalse
\let \mathversionorig \mathversion
\renewcommand{\mathversion}[1]{%
   \ifthenelse{\equal{#1}{bold}}{%
      \BoldMathtrue%
   }{%
      \BoldMathfalse%
   }%
   \mathversionorig{#1}%
}

\AtBeginDocument{%
   \let \mathitorig \mathit%
   \renewcommand{\mathit}[1]{%
      \ifBoldMath%
         \textbf{%
            \SetSymbolFont{__um_fam1}{boldmathVersion}{TU}{mathbolditalic}{b}{it}%
            \SetSymbolFont{__um_fam2}{boldmathVersion}{TU}{mathbolditalic}{b}{it}%
            \mathversion{boldmathVersion}%
            \(\mathitorig{#1}\)%
         }
      \else%
         \textit{%
            \SetSymbolFont{__um_fam1}{mathitVersion}{TU}{mathitalic}{m}{it}%
            \mathversion{mathitVersion}%
            \(\mathitorig{#1}\)%
         }%
      \fi%
   }%
   \let \mathbfitorig \mathbfit%
   \renewcommand{\mathbfit}[1]{{%
      \textbf{%
          \SetSymbolFont{__um_fam1}{mathbfitVersion}{TU}{mathbolditalic}{b}{it}%
          \mathversion{mathbfitVersion}%
          \(\mathbfitorig{#1}\)%
      }%
   }}%
}

\newcommand{\testUnicodeMath}{%
   \bigskip
   \begin{tabular}{l @{\quad}l @{\quad} l @{\quad} l @{\quad} l}
       Row
       & Math version/alphabet
       & Regular
       & Upright
       & Italic \\[\medskipamount]
       1
       & Text
       & A = 1a
       & \textup{B = 2b}
       & \textit{C = 3c} \\
       2 &
       \texttt{\textbackslash textbf}
       & \textbf{A = 1a}
       & \textbf{\textup{B = 2b}}
       & \textbf{\textit{C = 3c}} \\
       3
       & \texttt{\textbackslash mathversion\{normal\}} (default)
       & $A = 1a + \beta \times \Gamma \int_{-\infty}^{\infty} \frac{\mathup{d}x}{2}$
       & $\mathup{B = 2b + \beta \times \Gamma}$
       & $\mathit{C = 3c + \beta \times \Gamma}$ \\
       4
       & \texttt{\textbackslash mathversion\{bold\}}/\texttt{\textbackslash boldmath}
       & \boldmath $A = 1a + \beta \times \Gamma \int_{-\infty}^{\infty} \frac{\mathup{d}x}{2}$
       & \boldmath $\mathup{B = 2b + \beta \times \Gamma}$
       & \boldmath $\mathit{C = 3c + \beta \times \Gamma}$ \\
       5
       & \texttt{\textbackslash mathbf}/\texttt{\textbackslash mathbfup}/\texttt{\textbackslash mathbfit}
       & $\mathbf{A = 1a + \beta \times \Gamma \int_{-\infty}^{\infty} \frac{\mathup{d}x}{2}}$
       & $\mathbfup{B = 2b + \beta \times \Gamma}$
       & $\mathbfit{C = 3c + \beta \times \Gamma}$ \\
   \end{tabular}%
   \bigskip
   \bigskip
}


\begin{document}

\testUnicodeMath

\textit{Check that everything works properly by invoking it a~second time:}

\testUnicodeMath

\textit{Check that everything works properly by invoking it a~third time:}

\testUnicodeMath

\end{document}

This produces the following output—note that the “3” in table rows 3–5 is italic, in line with the formatting produced by the original LaTeX \mathit:

I also posted this solution in the different thread that Gaussler mentioned.