# [NTG-context] Add ssty to libertinus

Hans Hagen j.hagen at xs4all.nl
Wed Oct 20 16:14:29 CEST 2021

On 10/20/2021 1:01 PM, Mikael Sundqvist via ntg-context wrote:
> Hi,
>
> looking at the output of
>
> \setupbodyfont[libertinus]
> %\setupmathematics[stylealternative={ssty}]
> \starttext
> $y'=f'$
> \switchtobodyfont[newcomputermodern-book]
> $y'=f'$
> \stoptext

ssty doesn't kick in as we're in textstyle here (and even then \addff
doesn't work in math mode; ssty is applied when we load a font, if at
all because not all characters in a math font have a ssty feature
definition)

> I think that the primes in libertinus are too small. Indeed, looking
> in the font, they look like the output. In lualatex* I get larger
> primes, and as far as I understand it is because unicode-math enables
> ssty.

it's a design decision ... (imo the tex and math font community never
could make up its mind about primes so it will always be a pain) ..
looks like here the creator assumed a script design size for text size

> I was not able to do so with \addff{ssty} or with
> \setupmathematics[stylealternative={ssty}]. What do I miss?
>
> Best regards, Mikael
>
> *The file I used in lualatex was this:
> \documentclass{article}
> \usepackage{fontspec}
> \usepackage{unicode-math}
> \setmathfont{LibertinusMath-Regular.otf}
> \begin{document}
> $u'f'$
> \end{document}
whatever latex does to make these primes large is unlikely going to
happen in context ... at some point, when these fonts stay as they are
(all math fonts seem to have issues, but different ones) we can write
font goodie files to 'fix them' at the font level, adding all kind of
hacks to the context math handler is just stimulating 'not fixing a font'

\setupbodyfont[cambria]
\starttext
$y'=f'$
$\textstyle\prime$
$\scriptstyle\prime$
$\scriptscriptstyle\prime$
\switchtobodyfont[libertinus]
$y'=f'$
$\textstyle\prime$
$\scriptstyle\prime$
$\scriptscriptstyle\prime$
\switchtobodyfont[newcomputermodern-book]
$y'=f'$
$\textstyle\prime$
$\scriptstyle\prime$
$\scriptscriptstyle\prime$
\stoptext

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