Can LuaTeX create HTML?

Question

I heard that LuaTeX provides access to the internals of TeX. So, I have two questions in this regard:

• Is it possible to modify the output routine with LuaTeX so that HTML is produced instead of DVI or PDF?
• If possible, are there any projects aiming at this?

Answer 1

As it is possible to access nodes created by \special commands, we can access tags inserted by tex4ht. Small proof of concept is lua4ht package.

Advantage is that it supports fontspec and unicode-math packages, which tex4ht doesn't support otherwise, the downside is that mathml production is broken, so it is produced as normal italic text in the sample. In theory, we can produce mathml directly from LuaTeX's math nodes, I've tried some exercises in this direction and it seemed doable.

Sample:

\documentclass{article}

\usepackage{fontspec}
\usepackage{unicode-math}

\begin{document}

\section{Font support}

Příliš \textit{žluťoučký kůň} úpěl \textsc{ďábelské ódy}. A \textbf{další text}

\section{Math}

$\forall x \in X, \quad \exists y \leq \epsilon$

\section{Tables}

\begin{tabular}{ll}
  hello & world\\
  hello & again\\
\end{tabular}
\end{document}

we need also small config file, hej.cfg:

\Preamble{xhtml}

\Configure{textit}{\HCode{<em>}}{\HCode{</em>}}
\Configure{textbf}{\HCode{<strong>}}{\HCode{</strong>}}
\Configure{textsc}{\HCode{<span class="sc">}}{\HCode{</span>}}
\Configure{$}{\HCode{<span class="inline-math">}}{\HCode{</span>}}{}
\begin{document}
\Css{.sc{font-variant: small-caps;}}
\Css{.inline-math{font-style:italic;}}
\EndPreamble

compile with:

make4ht -b lua4ht -um draft -c hej.cfg  sample.tex  "new-accents"

and the result:

  <h3 class="sectionHead"><span class="titlemark">1 </span> <a 
 id="x1-10001"></a>Font support</h3> <!--l. 10--><p class="noindent" >Příliš <em>žluťoučký kůň</em> úpěl <span class="sc">ďábelské ódy</span>. A <strong>další text</strong>  </p><!--l. 12--><p class="noindent" > </p><h3 class="sectionHead"><span class="titlemark">2 </span> <a 
 id="x1-20002"></a>Math</h3> <!--l. 14--><p class="noindent" ><span class="inline-math">∀∈, ∃≤</span>  </p><!--l. 16--><p class="noindent" > </p><h3 class="sectionHead"><span class="titlemark">3 </span> <a 
 id="x1-30003"></a>Tables</h3><div class="tabular"> <table id="TBL-1" class="tabular" 
cellspacing="0" cellpadding="0"  
><colgroup id="TBL-1-1g"><col 
id="TBL-1-1" /><col 
id="TBL-1-2" /></colgroup><tr  
 style="vertical-align:baseline;" id="TBL-1-1-"><td  style="white-space:nowrap; text-align:left;" id="TBL-1-1-1"  
class="td11">  hello  </td><td  style="white-space:nowrap; text-align:left;" id="TBL-1-1-2"  
class="td11">  world  </td></tr><tr  
 style="vertical-align:baseline;" id="TBL-1-2-"><td  style="white-space:nowrap; text-align:left;" id="TBL-1-2-1"  
class="td11">  hello  </td><td  style="white-space:nowrap; text-align:left;" id="TBL-1-2-2"  
class="td11">  again  </td></tr><tr  
 style="vertical-align:baseline;" id="TBL-1-3-"><td  style="white-space:nowrap; text-align:left;" id="TBL-1-3-1"  
class="td11">   </td></tr></table> </div>