Add ssty to libertinus

Add ssty to libertinus

[Mikael Sundqvist via ntg-context]

Hi,

looking at the output of

\setupbodyfont[libertinus]
%\setupmathematics[stylealternative={ssty}]
\starttext
%\addff{ssty}
$y'=f'$
\switchtobodyfont[newcomputermodern-book]
$y'=f'$
\stoptext

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.

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}
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Re: Add ssty to libertinus

[Hans Hagen via ntg-context]

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
> %\addff{ssty}
> $y'=f'$
> \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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