Declaring a Specific Math Symbol in a TTF Font (LuaLaTeX)

Question

I'm trying to work around a classic problem in LaTeX for anyone that deals with Electromagnetism: define Griffiths' script-r notation. This time, I want to do it using the actual Kaufmann font he uses in his book, and I've already managed to get the files. While in LuaLaTeX it is easy to use the fonts "freely", I want to define a math symbol that uses it so that the code works well with other packages I use, such as the bold vector commands defined by physics.

After reading this answer on the post concerning the generic script-r problem, I was trying to implement the script-r notation by means of the \DeclareMathSymbol command, but I can't understand how to use Kaufmann font in it.

In short: I have two .ttf font files, Kaufmann-Regular.ttf and Kaufmann-Bold.ttf. How can I use them to define a math symbol \rcurs using Kaufmann font such that commands like \mathbf{\rcurs} return its bold version?

Do you need a unicode-math solution (where the range= option is available)? — Cicada, May 06 '22 at 05:21
@Cicada I don't really know what the range= option does, so I guess no, but it would be nice to be aware of the limitations of the solution =) — Níckolas Alves, May 06 '22 at 12:00
Somewhat related... Check math font - TeX - LaTeX Stack Exchange (alright, my TeX knowledge regarding fonts is not yet good enough to understand the content there, but looks like you needed it to fiddle around a bit. Here you already have a font file it should be possible?) — user202729, May 07 '22 at 00:36
LuaTeX: Use single symbol from other font in math mode - TeX - LaTeX Stack Exchange might help — user202729, May 07 '22 at 00:41
Remark, the macro \unimath_get_mathstyle: can be used to detect whether it's inside/outside symbf (which is documented API), while for \mathbf the best you can do is to look at \the\fam (in my testing it's -1 for normal and 4 for mathbf, but this is probably not guaranteed). Read unicode-math docs for difference between mathbf and symbf. — user202729, May 30 '22 at 15:02

Cicada · Answer 1 · 2022-05-08T13:42:56.923

Math alphabets and operators form a set, so doing mix-and-match will usually require low-level adjustments of different kinds.

Having said that, there are various ways and methods to import a symbol.

(1)

The simplest way is to include the glyphs as images\PDFs, and resize etc when needed, like Griffiths does:

Code:

\documentclass{report}
\usepackage{graphicx}
\def\rcurs{{\mbox{$\resizebox{.16in}{.08in}{\includegraphics{ScriptR}}$}}}
\def\brcurs{{\mbox{$\resizebox{.16in}{.08in}{\includegraphics{BoldR}}$}}}
\def\hrcurs{{\mbox{$\hat \brcurs$}}}
\begin{document}
Here's a sample:
$\resizebox{.16in}{.08in}{\includegraphics{BoldR}}$
Can I put it into a line of type?  $\resizebox{.21in}{.11in}{\includegraphics{BoldR}}$
How about using the macro: \brcurs.
How about using the macro: \rcurs?
How about using the macro: \hrcurs?
What if it's in an equation?
\begin{equation}
{\bf E} = {1\over 4\pi\epsilon_0}\int {\rho\over \rcurs^2}{\hrcurs},d\tau.
\end{equation}
\end{document}

See the Griffiths zip file http://academic.reed.edu/physics/faculty/griffiths/script_r.zip, via Script-r Symbol

(2)

The next most simplest way is to use one of the \math... functions (here, \mathord): Defining a math symbol of variable sizes in XeTeX with \Umathchardef via LuaTeX: Use single symbol from other font in math mode

Here's a list of them:

(texdoc source2e)

MWE

\documentclass{report}
\usepackage{xcolor}
\usepackage{unicode-math}
\setmathfont{Asana-Math}
\newfontfamily{\miama}{Miama}[Colour=red,
Scale=1.3,
Path=C:/Users/.../tl/texlive/2020/texmf-dist/fonts/opentype/public/miama/,
Extension=.otf,
UprightFont=*,
]
\DeclareRobustCommand\mysym{%
  \mathord{\text{\normalfont\miama r}}%
}
%\def\rcurs{{\mbox{$\resizebox{.16in}{.08in}{\includegraphics{ScriptR}}$}}}
%\def\brcurs{{\mbox{$\resizebox{.16in}{.08in}{\includegraphics{BoldR}}$}}}
%\def\hrcurs{{\mbox{$\hat \brcurs$}}}
\def\hrcurs{{\mbox{$\hat\mbfscrr$}}}
\begin{document}
\fbox{Asana-Math: $\mbfscrr, \mscrr $}
Here's a sample:
$\mbfscrr$
Can I put it into a line of type?  $\mbfscrr$
How about using the macro: \hrcurs?
What if it's in an equation?
\begin{equation}
\symbf{E} = {1\over 4\mitpi\mitepsilon_0}\int {\mitrho\over \mscrr^2}{\hat\mbfscrr},d\mittau.
\end{equation}
\renewcommand\mbfscrr{{\mysym}}
\def\hrcurs{{\mbox{$\hat\mbfscrr$}}}
\bigskip
\fbox{Miama: $\mysym$}
Here's a sample:
$\mysym$
Can I put it into a line of type?  $\mysym$
How about using the macro: \hrcurs?
What if it's in an equation?
\begin{equation}
\symbf{E} = {1\over 4\mitpi\mitepsilon_0}\int {\mitrho\over \mscrr^2}{\hat\mbfscrr},d\mittau.
\end{equation}
\end{document}

(2a)

Getting the accent adustments correct will require kerning etc. Here, a different non-math font avoids that issue:

MWE

\documentclass{report}
\usepackage{xcolor}
\usepackage{unicode-math}
\setmathfont{Asana-Math}
\newfontfamily{\gfs}{GFSBodoni}[Colour=red,
Scale=1.3,
Path=C:/Users/.../tl/texlive/2020/texmf-dist/fonts/opentype/public/gfsbodoni/,
Extension=.otf,
UprightFont=*,
ItalicFont=GFSBodoniIt,
BoldFont=GFSBodoniBold,
BoldItalicFont=GFSBodoniBoldIt,
]
\DeclareRobustCommand\mysymbi{%
  \mathord{\text{\normalfont\gfs\bfseries\itshape r}}%
}
\DeclareRobustCommand\mysym{%
  \mathord{\text{\normalfont\gfs\itshape r}}%
}
\def\hrcurs{{\mbox{$\hat\mbfscrr$}}}
\begin{document}
\fbox{Asana-Math: $\mbfscrr, \mscrr $}
Here's a sample:
$\mbfscrr$
Can I put it into a line of type?  $\mbfscrr$
How about using the macro: \hrcurs?
What if it's in an equation?
\begin{equation}
\symbf{E} = {1\over 4\mitpi\mitepsilon_0}\int {\mitrho\over \mscrr^2}{\hat\mbfscrr},d\mittau.
\end{equation}
\renewcommand\mbfscrr{{\mysymbi}}
\def\hrcurs{{\mbox{$\hat\mbfscrr$}}}
\bigskip
\fbox{GFS Bodoni: $\mysymbi, \mysym$}
Here's a sample:
$\mysym$
Can I put it into a line of type?  $\mysym$
How about using the macro: \hrcurs?
What if it's in an equation?
\begin{equation}
\symbf{E} = {1\over 4\mitpi\mitepsilon_0}\int {\mitrho\over \mysym^2}{\hat\mbfscrr},d\mittau.
\end{equation}
\end{document}

(3)

Next, mapping using unicode-math package's range= font option.

Mapping from a Unicode math font:

MWE

\documentclass{report}
\usepackage{xcolor}
\usepackage{unicode-math}
\setmathfont{Asana-Math}
\def\hrcurs{{\mbox{$\hat\mbfscrr$}}}
\begin{document}
\fbox{Asana-Math: $\mbfscrr,\mscrr$}
Here's a sample:
$\mbfscrr$
Can I put it into a line of type?  $\mbfscrr$
How about using the macro: \hrcurs?
What if it's in an equation?
\begin{equation}
\symbf{E} = {1\over 4\mitpi\mitepsilon_0}\int {\mitrho\over \mscrr^2}{\hat\mbfscrr},d\mittau.
\end{equation}
\setmathfont{TexGyreSchola-Math}[range={\mbfscrr,\mscrr},Colour=red]
\bigskip
\fbox{TexGyreSchola-Math: $\mbfscrr,\mscrr$}
Here's a sample:
$\mbfscrr$
Can I put it into a line of type?  $\mbfscrr$
How about using the macro: \hrcurs?
What if it's in an equation?
\begin{equation}
\symbf{E} = {1\over 4\mitpi\mitepsilon_0}\int {\mitrho\over \mscrr^2}{\hat\mbfscrr},d\mittau.
\end{equation}
\end{document}

(4)

\DeclareMathSymbol uses legacy font techniques. ttf\otf fonts can be used by assigning them an NFSS-alias via fontspec package (so xelatex or lualatex as compiler), and then going through multiple steps as per the linked question.

The option is NFSSFamily=.

The example uses QTFloraline font (in the tex distribution)L it has a regular face and a bold face. Substitute your kaufmann files instead.

MWE

\documentclass{article}
\usepackage{xcolor}
\usepackage{unicode-math}
\setmathfont{Asana-Math}
\newfontface\ffontc{QTFloraline}[
Extension=.otf,
UprightFont=,
BoldFont=-Bold,
NFSSFamily=floraline,
]
\usepackage{bm}
\DeclareFontFamily{U}{floraline}{}
\DeclareFontShape{U}{floraline}{m}{n}{<-> QTFloraline}{}
\DeclareFontShape{U}{floraline}{b}{n}{<-> QTFloraline-Bold}{}
\DeclareSymbolFont{myfloraline}{U}{floraline}{m}{n}
\SetSymbolFont{myfloraline}{bold}{U}{floraline}{b}{n}
\DeclareMathSymbol{\rcurs}{\mathalpha}{myfloraline}{`\r}
\DeclareBoldMathCommand{\brcurs}{\rcurs}
\newcommand*\hrcurs{\hat{\brcurs}}
\begin{document}
[
  \mathbf{E}(\mathbf{r}) = \frac{1}{4 \pi \epsilon_0} \int\limits_{\mathcal{V}} \frac{\rho(\mathbf{r}')}{\rcurs^2} \hrcurs d \tau'
]
Using \texttt{unicode-math} macros:
[
  \symbfup{E}(\symbfup{r}) = \frac{1}{4 \mitpi \mitepsilon_0} \int\limits_{\symcal{V}} \frac{\mitrho(\symbfup{r}')}{\rcurs^2} \hrcurs d \mittau'
]
\end{document}

(5)

For one or two symbols, the \mathord{} method is easier, and doesn't use up a whole math alphabet either.

As it turns out, unicode-math defines two macros, \mbfscrr and \mscrr. These can just be redefined (renewcommand) via \mathord, and that's that.

The code steps through the stages of what to change, illustrating each result, reaching the final step using QTChanceryType font:

MWE

\documentclass{report}
\usepackage{xcolor}
\usepackage{unicode-math}
\setmathfont{Asana-Math}
\newfontface\bodb{BOD_BLAR.TTF}[Colour=red]
\newfontface\ffontbreg{QTChanceryType.otf}
\newfontface\ffontbbold{QTChanceryType-Bold.otf}
\DeclareRobustCommand\xmbfscrr{%
\mathord{\text{\normalfont\bodb A}}%
}
\DeclareRobustCommand\myscrr{%
\mathord{\text{\normalfont\ffontbreg r}}%
}
\DeclareRobustCommand\mybfscrr{%
\mathord{\text{\normalfont\ffontbbold r}}%
}
\begin{document}
%======================: 0: base
\fbox{Asana-Math: $\mbfscrr,\mscrr$}
\begin{equation}
\symbfup{E} = {\frac{1}{4\mitpi\mitepsilon_0}}\int {\frac{\mitrho}{\mscrr^2}}{\hat\mbfscrr},d\mittau.
\end{equation}
%======================: 1: A
\renewcommand{\mbfscrr}{A}
\bigskip
\begin{equation}
\symbfup{E} = {\frac{1}{4\mitpi\mitepsilon_0}}\int {\frac{\mitrho}{\mscrr^2}}{\hat\mbfscrr},d\mittau.
\end{equation}
%======================: 2: A from another font
\renewcommand{\mbfscrr}{{\xmbfscrr}}
\bigskip
\begin{equation}
\symbfup{E} = {\frac{1}{4\mitpi\mitepsilon_0}}\int {\frac{\mitrho}{\mscrr^2}}{\hat\mbfscrr},d\mittau.
\end{equation}
%======================:  3: r and bold r, from another font
\renewcommand{\mbfscrr}{{\mybfscrr}}
\renewcommand{\mscrr}{{\myscrr}}
\bigskip
\begin{equation}
\symbfup{E} = {\frac{1}{4\mitpi\mitepsilon_0}}\int {\frac{\mitrho}{\mscrr^2}}{\hat\mbfscrr},d\mittau.
\end{equation}
\end{document}

Addendum

To avoid ambiguity, text mode and math mode are completely different universes, in terms of fonts.

Where does the italic x () come from in a Unicode maths font, if there is just plain upright Latin and Greek in it?

From the Mathematical Alphanumeric Symbols block:

$x$ (or \mitx) will fetch the italic "version":

and $\mathbf{x}$ (more correctly, \symbfit{x}, or \mbfitx) will get the bold italic x:

They are different glyphs, in different slots (bold, or not bold, has semantic meaning, unlike in text mode, where the x is the same slot in the regular font file, and in the bold font file.

Copy-pasting Unicode math symbols preserves the semantic meaning.

That is why, in math mode, you need to define two glyphs, and .

I think this miss the whole point of the question. OP already know how to use character from ttf file, they're asking how to make the same command render differently when it's inside or outside mathbf. — user202729, May 08 '22 at 03:35
@user202729 See addendum. "Inside or outside" is text mode concept; in math mode, boldness (or not) is part of the glyph, and the (same) glyph cannot be inside itself or outside itself: hence, two glyphs. — Cicada, May 08 '22 at 13:48

Declaring a Specific Math Symbol in a TTF Font (LuaLaTeX)

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