% $Id: tex4ht-mathjax.tex 1012 2021-11-19 09:35:54Z michal_h21 $
% compile: latex tex4ht-mathjax
%
% Copyright 2018-2021 TeX Users Group
% Released under LPPL 1.3c+.
% See tex4ht-cpright.tex for license text.

\ifx \HTML\UnDef
   \def\HTML{mathjax-latex-4ht} 
   \def\CONFIG{\jobname}
   \def\MAKETITLE{\author{Michal Hoftich}}
   \def\next{\input mktex4ht.4ht  \endinput}
   \expandafter\next
\fi

\input{common-code}
\input{common}
\input{tex4ht-cpright}

\<mathjax-latex-4ht\><<<
% mathjax-latex-4ht.sty (|version), generated from |jobname.tex
% Copyright 2018-2021 TeX Users Group
|<TeX4ht copywrite|>
|<required packages|>
|<defined commands|>
\AtBeginDocument{%
|<configurations|>
}
\endinput
>>>

We don't require additional packages anymore, as everything necessary is included
in LaTeX kernel now.
% \RequirePackage{etoolbox,expl3,environ}
\<required packages\><<<
>>>

The \verb|\alteqtoks| command saves the used command in HTML. It uses detokenize command
to insert arguments verbatim. The side effect of this is that detokeize inserts space
after each control sequence. This is completely valid TeX code, but earlier versions of
MathJax didn't like that, rendering resulted in error.

Fortunatelly, MathJax 3 supports these spaces, so we can remove regular expressions for space handling.
The original code was this:

% % convert \ { to \:{ 
% \regex_replace_all:nnN { \x{5C} \x{20} \x{7B} } { \x{5C} \x{3A} \x{7B} } \l_tmpa_tl
% % delete spaces before left brackets
% \regex_replace_all:nnN { \x{20} \x{7B} } { \x{7B} } \l_tmpa_tl
% % replace \\:{ back to \\ { -- this can be introduced by the previous regex
% \regex_replace_all:nnN { \x{5C} \x{5C}  \x{3A} \x{7B} } { \x{5C} \x{5C} \x{20} \x{7B} } \l_tmpa_tl


We still use regula expressions to escape invalid XML characters to entities, so it works only with LaTeX.

\<defined commands\><<<
\ExplSyntaxOn
\cs_new_protected:Npn \alteqtoks #1
{
  \tl_set:Nx \l_tmpa_tl {\detokenize{#1}}
  % % replace < > and & with xml entities
  \regex_replace_all:nnN { \x{26} } { &amp; } \l_tmpa_tl
  \regex_replace_all:nnN { \x{3C} } { &lt; } \l_tmpa_tl 
  \regex_replace_all:nnN { \x{3E} } { &gt; } \l_tmpa_tl
  % replace \par command with blank lines
  \regex_replace_all:nnN { \x{5C}par } {\x{A}\x{A}} \l_tmpa_tl
  \tl_set:Nx \l_tmpb_tl{ \l_tmpa_tl }
  \HCode{\l_tmpb_tl}
}
\ExplSyntaxOff

>>>

Provide configuratio for MathJax

\<defined commands\><<<
\NewConfigure{MathJaxConfig}{1}
>>>

The following commands are used for patching of the standard math commands and
environments. They will then keep the LaTeX code unchanged.

\<defined commands\><<<

\long\def\AltlMath#1\){\expandafter\alteqtoks{\(#1\)}\)}
\long\def\AltlDisplay#1\]{\alteqtoks{\[#1\]}\]}
\long\def\AltMathOne#1${\alteqtoks{\(#1\)}$}
% this seems a bit hacky -- we need to skip some code inserted at the 
% beginning of each display math
\long\def\AltlDisplayDollars\fi#1$${\alteqtoks{\[#1\]}$$}

\newcommand\VerbMathToks[2]{%
  \alteqtoks{\begin{#2}
    #1
  \end{#2}}%
}
>>>

The \verb|\VerbMath| command redefines environments to pass their content
verbatim to the HTML output.

\<defined commands\><<<
\ExplSyntaxOn
\newcommand\VerbMath[1]{%
  \cs_if_exist:cTF{#1}{
    \RenewDocumentEnvironment{#1}{+!b}{%
      \NoFonts\expandafter\VerbMathToks\expandafter{##1}{#1}\EndNoFonts%
    }{}
  }{}%
}
\ExplSyntaxOff
>>>

The \verb|\fixmathjaxtoc| command is used for patching commands which should
keep their verbatim appearance in the TOC

\<defined commands\><<<
\def\fixmathjaxtoc#1{\Configure{writetoc}{\def#1{\detokenize{#1}}}}
>>>

Some math commands cause issues when used in sections, so we will deactivate them.

\<defined commands\><<<
\def\fixmathjaxsec#1{\def#1{\detokenize{#1}}}
>>>

Require verbatim math environments.

\<configurations\><<<
\VerbMath{subarray}
\VerbMath{smallmatrix}
\VerbMath{matrix}
\VerbMath{pmatrix}
\VerbMath{bmatrix}
\VerbMath{Bmatrix}
\VerbMath{vmatrix}
\VerbMath{Vmatrix}
\VerbMath{cases}
\VerbMath{subequations}
\VerbMath{aligned}
\VerbMath{alignedat}
\VerbMath{gathered}
\VerbMath{gather}
\VerbMath{gather*}
\VerbMath{alignat}
\VerbMath{alignat*}
\VerbMath{xalignat}
\VerbMath{xalignat*}
\VerbMath{xxalignat}
\VerbMath{align}
\VerbMath{align*}
\VerbMath{flalign}
\VerbMath{flalign*}
\VerbMath{split}
\VerbMath{multline}
\VerbMath{multline*}
\VerbMath{equation}
\VerbMath{equation*}
\VerbMath{math}
\VerbMath{displaymath}
\VerbMath{eqnarray}
\VerbMath{eqnarray*}
>>>

It is necessary to reset env configurations for multiline 
environments, because default TeX4ht configurations turn
them into pictures.

\<configurations\><<<
\ConfigureEnv{gather}{}{}{}{}
\ConfigureEnv{gather*}{}{}{}{}
\ConfigureEnv{multline}{}{}{}{}
\ConfigureEnv{multline*}{}{}{}{}
>>>


Fixes for tables of contents.

\<configurations\><<<
\fixmathjaxsec\left
\fixmathjaxsec\right
\fixmathjaxtoc\int
\fixmathjaxtoc\,
\fixmathjaxtoc\sin
\fixmathjaxtoc\cos
\fixmathjaxtoc\tan
\fixmathjaxtoc\arcsin
\fixmathjaxtoc\arccos
\fixmathjaxtoc\arctan
\fixmathjaxtoc\csc
\fixmathjaxtoc\sec
\fixmathjaxtoc\cot
\fixmathjaxtoc\sinh
\fixmathjaxtoc\cosh
\fixmathjaxtoc\tanh
\fixmathjaxtoc\coth
\fixmathjaxtoc\log
\fixmathjaxtoc\ln
\fixmathjaxtoc\sum
\fixmathjaxtoc\(
\fixmathjaxtoc\)
\fixmathjaxtoc\begin
\fixmathjaxtoc\end
\fixmathjaxtoc\\
\fixmathjaxtoc\exp
>>>
