Make4ht MathML and TeX

Question

When using Make4ht how to get MathML and LaTeX code in HTML?

My MWE is:

%!TEX TS-program = lualatex
%!TEX encoding = UTF-8 Unicode

\documentclass{elife}

\title{Grasp movement initiation and representation}

\begin{document}

We recorded single neurons in F1 and hold actions, and investigated the population-level differences could explain, please refer $t_{1,92} = -0.55$ plotted $\mathbf{V_{Obs}}$ at x10 gain)  how condition.


\end{document}

Answer 1

It is possible to do that, but it is not that easy. Here is a MWE:

\documentclass{article}
\newcommand\eqannotate[1]{#1}

\title{Grasp movement initiation and representation}

\begin{document}

We recorded single neurons in F1 and hold actions, and investigated the population-level differences could explain, please refer $t_{1,92} = -0.55$ plotted $\mathbf{V_{Obs}}$ at x10 gain)  how condition.

\[
  c^2 = \sqrt{a^2+b^2}  
\]


\begin{equation}
  \eqannotate{c^2 = \sqrt{a^2+b^2}}
\end{equation}
\end{document}

As you can see, I introduced the \eqannotate command, which is used in the equation environment. I am afraid that it is not easily possible to catch contents of environments, so they need to be marked by hand (or using pre-processing script).

Here is a configuration file:

\Preamble{xhtml}
\newtoks\eqtoks 


\def\AltMath#1${\eqtoks{#1}% 
   #1\HCode{</mrow><annotation encoding="application/x-tex">\the\eqtoks</annotation>}$} 
\Configure{$}{\Configure{@math}{display="inline"}\DviMath\HCode{<semantics><mrow>}}{\HCode{</semantics>}\EndDviMath}{\expandafter\AltMath} 

\long\def\AltDisplay#1\]{\eqtoks{#1}#1\HCode{</mrow><annotation encoding="application/x-tex">\the\eqtoks</annotation></semantics>}\]}
\Configure{[]}{\Configure{@math}{display="block"}\DviMath$$\DisplayMathtrue\HCode{<semantics><mrow>}\AltDisplay}{$$\EndDviMath}

\renewcommand\eqannotate[1]{\eqtoks{#1}\HCode{<semantics><mrow>}#1\HCode{</mrow><annotation encoding="application/x-tex">\the\eqtoks</annotation></semantics>}}


\begin{document}
\EndPreamble

MathML has the <annotation> element, it can be used to insert raw LaTeX code to the HTML as an annotation.

\Configure{$} and \Configure{[]} configure what HTML code will be inserted for $ ... $ and \[ ... \]. It also calls command that saves the original LaTeX code in a token list, typesets MathML and then prints the saved tokens inside <annotation>. Most of this code is copied from mathml.4ht, it is only a bit simplified.

Regarding wrong formatting of $\mathbf{V_{Obs}}$, this can be fixed using the following DOM filter:

local domfilter = require "make4ht-domfilter"


local function find_mstyle(x)
  -- find if element has <mstyle> parent, and its value of mathvariant
  if not x:is_element() then
    return nil
  elseif x:get_element_name() == "mstyle" then
    return x:get_attribute("mathvariant")
  else
    return find_mstyle(x:get_parent())
  end
end


local process = domfilter {
  function(dom)
    -- fix bold subscript
    for _, el in ipairs(dom:query_selector "mstyle mi") do
      local mathvariant = find_mstyle(el:get_parent())
      if mathvariant and el:get_attribute("mathvariant") then
        el:set_attribute("mathvariant", mathvariant)
      end
    end
    return dom
  end 
}

Make:match("html$", process)

Compile using:

make4ht -e build.lua -c config.cfg sample.tex "mathml,mathjax"

This is the resulting HTML:

<p class='noindent'>We recorded single neurons in F1 and hold actions, and investigated
the population-level differences could explain, please refer
<!--  l. 9  --><math display='inline' xmlns='http://www.w3.org/1998/Math/MathML'><semantics><mrow><msub><mrow><mi>t</mi></mrow><mrow><mn>1</mn><mo class='MathClass-punc'>,</mo><mn>92</mn></mrow></msub> <mo class='MathClass-rel'>=</mo> <mo class='MathClass-bin'>−</mo><mn>0.55</mn></mrow><annotation encoding='application/x-tex'>t_{1,92} = -0.55</annotation></semantics></math> plotted
<!--  l. 9  --><math display='inline' xmlns='http://www.w3.org/1998/Math/MathML'><semantics><mrow><mstyle mathvariant='bold'><msub><mrow><mi>V</mi></mrow><mrow><mi mathvariant='bold'>Obs</mi></mrow></msub></mstyle></mrow><annotation encoding='application/x-tex'>\mathbf {V_{Obs}}</annotation></semantics></math> at
x10 gain) how condition.
</p><!--  l. 11  --><p class='indent'>   <!--  l. 11  --><math display='block' xmlns='http://www.w3.org/1998/Math/MathML'>
                                          <semantics><mrow><msup><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msup> <mo class='MathClass-rel'>=</mo> <msqrt><mrow><msup><mrow><mi>a</mi></mrow><mrow><mn>2</mn> </mrow> </msup> <mo class='MathClass-bin'>+</mo> <msup><mrow><mi>b</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></msqrt></mrow><annotation encoding='application/x-tex'> c^2 = \sqrt {a^2+b^2} </annotation></semantics>
</math>
</p>
   <table class='equation'><tr><td>
<!--  l. 16  --><math class='equation' display='block' xmlns='http://www.w3.org/1998/Math/MathML'>
                           <mstyle class='label' id='x1-2r1'></mstyle><!--  endlabel  --><semantics><msup><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msup> <mo class='MathClass-rel'>=</mo> <msqrt><mrow><msup><mrow><mi>a</mi></mrow><mrow><mn>2</mn> </mrow> </msup> <mo class='MathClass-bin'>+</mo> <msup><mrow><mi>b</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></msqrt><annotation encoding='application/x-tex'>c^2 = \sqrt {a^2+b^2}</annotation></semantics>
</math></td><td class='eq-no'>(1)</td></tr></table>

And rendered page: