Hi Franks,

thank you for your suggestions and fixes. It seems that it works correctly.

> But basically the main issue is that in the old LaTeX \document started
> out with \endgroup to cancel the \begingroup issued by \begin
>
> As \begin now offers hooks this \endgroup has moved into \begin to avoid
> that the hook code is not canceled by the end of  the group.
>
> The second issue is that the tex4ht calls \begin{document} inside
> \begin{document} again. There is also a call to \end{document} inside
> \document which doesn't do much other than breaking now.
>
> Furthermore LaTeX's enddocument hook is directly modified (and not
> through \AtEndDocument and that fails because it is below the official
> interfaces.
>

> %FMi close the group started by \begin{document} on second call
> %   \let\document\o:document
>     \def\document{\endgroup\o:document}%

Yes, this works for now, thank you.

> So without correcting/updating the redefinitions for \begin \end it has
> to be
>
>   \AddToHook{enddocument}
>             {\HtmlEnv\Configure{newpage}{}}
>   \AddToHook{enddocument/afterlastpage}
>             {\at:docend  \csname export:hook\endcsname}
>
>
> ------------------
>
> with that everything seems to be working.
>

This results in missing HTML footer in the last generated HTML file.
Fortunately,

\AddToHook{enddocument}
     {\HtmlEnv\Configure{newpage}{}\at:docend  \csname export:hook\endcsname}

works.

> However, a lot of the lowlevel patching code inside tex4ht seems to be
> only necessary because environment hooks are not available, so after
> adjusting \begin and \end to use the kernel definitions it should be
> possible to simplify a lot by simply using appropriate "env/foo/before"
> and "env/foo/after" hooks.

I hope it will be relatively easy to adapt our environment patching
routine to the new LaTeX hook system. It should definitely simplify
lot of the low-level code.

Thanks again for all your comments and code.

Michal