[tex4ht] exerquiz problems

Tomas Davidek Tomas.Davidek at cern.ch
Thu Jan 21 07:47:17 CET 2021

Thanks a lot, Michal, this helped a lot. I am usually running several 
checks on the LaTeX code, but both pdflatex and lacheck did not reveal 
this problem.



On 1/19/21 11:10 PM, Michal Hoftich wrote:
> Dear Tomáš,
>> Well, the error message suggests there might be a problem in the 
>> configuration file (split.cfg), but - when getting rid of the 
>> exerquiz environment, the error message disappears. It's strange, 
>> maybe there is some interference between the align and example 
>> environments?? I don't know.
>> Attached is a tarball containing all files needed for running the 
>> example. The examples are two - one with the exercise environment 
>> heavily used (exerquiz_exx.tex) and another without using this 
>> environment (exerquiz_ex.tex, this one runs ok).
> In this particular example, exerquiz_exx.tex, I've found a following 
> issue:
> Vztah~(\ref{eq:cross_section_annihilation}) dává číselnou hodnotu
> \begin{displaymath}
>   \label{eq:cross_section_value}
>   \sigma
> =\frac{4\pi\left(\frac{1}{137}\right)^2\left(0{,}197~\gev\cdot\mathrm{fm}\right)^2}{3s}
>   \doteq 8{,}66\cdot 10^{-6}\frac{1}{s~[\gev^2]}~\mathrm{fm}^2
>   % = 2{,}232\cdot 10^{-5}~\gev^{-2} = \\
>   % & = 2{,}232\cdot 10^{-5}\times 0{,}197^2~\mathrm{fm}^2 = 8{,}7\cdot
>   % 10^{-7}~\mathrm{fm}\nonumber
> \end{displaymath}
> The issue is with the \label command. It compiles correctly when I 
> remove it. I think the issue is that displaymath is internally 
> equation*, which is unnumbered and it cannot produce a number in \ref 
> anyway.
> There must be something else going on though, because when I try a 
> following MWE:
> \documentclass{article}
> \usepackage{amsmath}
> \begin{document}
> \begin{displaymath}
>   a=b
>   \label{ahoj}
> \end{displaymath}
> Ref: \ref{ahoj}
> \end{document}
> it compiles without errors. It even produces hyperlinks, just the 
> hyperlink produced by \ref is empty, so you cannot click on it.
> So there is something going on, but it would be best to remove the 
> \label from this displaymath, as it is not useful anyway. You even 
> don't reference it anywhere.
>> I should also note that - even when getting the error messages - the 
>> resulting HTML page looks reasonably, but when adding more chapters, 
>> the code crashes. So apparently one should avoid these error messages 
>> for large documents....
> I could compile the sample file using:
> make4ht -f html5+dvisvgm_hashes -m draft -c split.cfg -a debug 
> exerquiz_exx.tex "svg,2,fn-in"
> The `-f html5+dvisvgm_hashes` option can significantly speed up the 
> compilation, because it reuses math images.
> I've also introduced `svg` and `fn-in` options, the first one requires 
> SVG images, the second puts footnotes at the end of the chapter where 
> they were used, instead of standalone files.
>> Maybe the problem can be fixed by an improvement in the configuration 
>> file split.cfg??
> Other than that, I can see only one issue regarding validity of the 
> produced HTML files, there is spurious `</form>` element in the lasth 
> HTML file. I need to investigate where it comes from.
> Best regards,
> Michal

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