Re: behavior of @math with HTML output

[Gavin Smith]

On Sat, Oct 15, 2022 at 07:14:04PM -0500, Jacob Bachmeyer wrote:
> Since @math is defined to use TeX syntax in its argument, would it be better
> to extend the other Texinfo processors to recognize \var inside @math and do
> whatever is needed to make it act as @var in that case?

@var already seems to do the right thing in Info, HTML, DocBook, LaTeX,
and texinfo.tex output.

I see no benefit to extending texi2any to recognize e.g. \var as well.  I'm
going to change the documentation to make it clear that Texinfo
@-commands are still accessed with @ not \ inside @math.

>    Because math expressions will often contain variables also mentioned
>    in running text, Texinfo supports one extension to plain TeX in
>    @math:  the Texinfo @var{...} command is available as \var{...}
>    inside the argument of a @math command.

It wouldn't be surprising if people wanted to use other Texinfo commands
inside @math too, so I'd rather leave it ambiguous.

> ... or something similar.  There is no (good) way to make this /not/ work
> with texinfo.tex (for TeXnical reasons) but the other Texinfo processors
> would need to be extended to support it.

Au contraire, code is needed in texinfo.tex for this (in the definition
of \sl, assigning \fam).

> > It also works well enough with MathJax with Patrice's latest change,
> > using \mathit for the variable names (there appears to be no "\mathsl" so
> > there is a slight difference in font style in and out of math - this
> > seems unavoidable).
> 
> If I am reading my copy of /TeX for the Impatient/ correctly, the ordinary
> plain TeX \sl command should work in math mode.

It does, but not with MathJax (or the version I tested).

> Note that I am not sure
> that HTML normally has slanted fonts at all, so MathJax may be stuck with
> substituting italics for slanted; this would be an output format limitation,
> much as plain text and Info lack the ability to change fonts at all, but
> should also be consistent:  if HTML substitutes italics for slanted, the
> normal use of @var would also produce italic text.