Font setup, in particular for \mathrm

[josephwright]

Out current font setup is the equivalent of

\DocumentMetadata{}
\documentclass{article}
\ExplSyntaxOn
\sys_if_engine_opentype:TF
  {
    \RequirePackage { unicode-math }
    \setmainfont { NewCM10-Regular.otf }
    \setsansfont { NewCMSans10-Regular.otf }
    \setmathfont { NewCMSansMath-Regular.otf }
  }
  { \RequirePackage { sansmathfonts } }
\cs_set:Npn \familydefault { \sfdefault }
\ExplSyntaxOff
\begin{document}

Some \textrm{text}; $y = mx + c$ but $D_{3\mathrm{h}}$

\end{document}

which leads to an oddity in terms of \mathrm - sanserif for pdfTeX, serifed for OpenType engines.

My previous font approach was more 'aggressive'

\DocumentMetadata{}
\documentclass{article}
\ExplSyntaxOn
\sys_if_engine_opentype:TF
  {
    \RequirePackage { unicode-math }
    \setsansfont { NewCMSans10-Regular.otf }
    \setmathfont { NewCMSansMath-Regular.otf }
  }
  { \RequirePackage { sansmathfonts } }
\cs_set_eq:NN \rmdefault \sfdefault
\ExplSyntaxOff
\begin{document}

Some \textrm{text}; $y = mx + c$ but $D_{3\mathrm{h}}$

\end{document}

but that means one can't use serifed fonts at all - and @Skillmon wasn't keen :)

What do we feel is the best default position to take, bearing in mind that we will document this and alternative approaches. Ideally I'd like to avoid needing \let\mathrm\mathsf, which I currently need in beamer.

[davidcarlisle]

This is similar to the general question about sans serif math setup, eg the original noto sans math had serifed letters in the math italic slots but the updated v3 has sans serif everywhere (duplicating the sans serif range) and if you want serif font do as you'd do for any other font family and load a new font .

Arguably with unicode-math it would be consistent to use \mathup (\symup) for the default non-italic style (so sans serif) and keep \mathrm as serif roman, but I think that's less useful, people use \mathrm{foo} and expect the deafult document style (mostly)

On the other hand if you do go for \mathup==\mathsf = sans and \mathrm = serif in unicode-math, I'd adjust pdflatex to match.

[u-fischer]

Imho that most people would expect that if they copy & paste an equation from a (serif) paper into a (sans serif) presentation that "it works" and has a consistent look. Which means that in $D_{3\mathrm{h}}$ everything should be in sans serif. So I would say \mathrm= sans serif, \mathsf=serif, \mathup=sans serif as default.

[FrankMittelbach]

With the same argument you can say that a user expects (knowing that the beamer style they use make the math sans) that they get serif if they ask for \mathrm and they explicitly put that in because of that, just like they expect to get upright sans if they say \mathsf in that scenario and not suddenly serif upright.

And to stay with you analogy \textcolor{blue}{colors}. If I make the current paragraph fully blue nobody would expect that the word colors comes out in black now. So if I paste that into a document set in blue I need to adjust what I pasted and it isn't adjusted for me (and imo it would be wrong if that would happen automatically).

[davidcarlisle]

@FrankMittelbach yes I know the argument can be made to cut either way:-) but if we ignore pdftex and just look at unicode fonts, by default there's only one math font, \mathrm/\symsf will use the classic ascii range, default letters will use the math italic range and \mathsf/symsf will use the math sans serif range. If you then chose a sans serif math font such as noto sans math, \mathsf and \symsf choose identical upright sans serif glyphs with different code points and the default letters use a slanted sans serif. You could of course load a second Serif math font and re-assign some of the ranges to be serif, but that's what I meant above by saying by default it should all go sans serif and if you need serif characters you need to load a second font.

[josephwright]

Note my original plan was to leave fonts entirely, basically because of this issue. But it was pointed out that most of the time some sans font setup is sensible: it’s a question of exactly which one.

[josephwright]

As a user wanting more ‘applied’ maths, I personally favour everything sans but I know there are arguments both ways.

[josephwright]

For the record, beamer leaves \mathrm alone, but then has some rather odd advice

Note: The command \mathrm will always produce upright (not slanted), serif text and the command \mathsf will always produce upright, sans-serif text. The command \mathbf will produce upright, bold-face, sans-serif or serif text, depending on whether mathsans or mathserif is used.

To produce an upright, sans-serif or serif text, depending on whether mathsans or mathserif is used, you can use for instance the command \operatorname from the amsmath package. Using this command instead of\mathrm or \mathsf directly will automatically adjust upright mathematical text if you switch from sans-serif to serif or back.

[Skillmon]

We could use the aggressive approach but also provide a load time option to not do any font setup at all.

[davidcarlisle]

you could give that a really descriptive name, like professionalfonts

[josephwright]

I think key is that we are going for a much easier to explain font arrangement than Beamer.

[josephwright]

I've decided we are going for the truly all-sans approach at the moment: I'll make sure this is explicitly documented as a different from beamer.