tex4ht does not scale math font along with text when using mathjax

Question

In this MWE documentclass{article} usepackage{amsmath} begin{document} tiny All of this font should be tiny include the math begin{align*} sin x &= 1 end{align*} normalsize All of this font should be normal include the math begin{align*} sin x &= 1 end{align*} end{document} Both math and text fonts sizes change when compiled to PDF. But when compiling to HTML using tex4ht and when using mathjax option, only the text size is changed. Math size remains normal. make4ht -ulm default foo5.tex "mathjax,htm" gives The raw HTML generated is

All of this font should be tiny include the math begin {align*} sin x &= 1 end {align*}

All of this font should be normal include the math begin {align*} sin x &= 1 end {align*}

Is this tex4ht issue or mathjax? And how to make both text and math change size at same time as the case is when compiling to PDF? Using TL 2020 on Linux.

michal.h21 · Accepted Answer

When you change font using font switches like tiny, TeX4ht produces extra <span> elements that hold the font information, like in this case:

<span class='rm-lmr-5'>All of this font should be tiny include the math </span>begin {align*} sin x &amp;= 1 end {align*}

This depends on the font information in the DVI file. In this case, problem is that we don't (and cannot) keep this font information in math, so you need to change your code slightly.

I would use a custom environment that changes font size to tiny. We can configure that environment do produce HTML code that can be styled using CSS. It should then work with MathJax.

Here is the updated TeX file:

documentclass{article}
usepackage{amsmath}
newenvironment{mytiny}{tiny}{}
begin{document}

begin{mytiny}
All of this font should be tiny include the math
begin{align*} 
sin x &= 1
end{align*} 
end{mytiny}

normalsize
All of this font should be normal include the math
begin{align*} 
sin x &= 1
end{align*} 
end{document}

It can be configured using the following .cfg file:

Preamble{xhtml}
renewenvironment{mytiny}{}{}
ConfigureEnv{mytiny}{ifvmodeIgnoreParfiEndPHCode{<div class="tiny">}par}{ifvmodeIgnoreParfiEndPHCode{</div}}{}{}

Css{div.tiny{font-size: 0.8em;}}
begin{document}
EndPreamble

It produces the following HTML code:

  <div class='tiny'>
<!-- l. 7 --><p class='indent'>   All of this font should be tiny include the math begin {align*} sin x &amp;= 1 end {align*}
</p>
   </div>

}par}{ifvmodeIgnoreParfiEndPHCode{

All of this font should be tiny include the math begin {align*} sin x &= 1 end {align*}

tex4ht does not scale math font along with text when using mathjax

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