[NTG-context] Question to kernings (modern, sans, \bi)

[NTG-context] Question to kernings (modern, sans, \bi)

[Tomáš Hála]

Hi all,

the MWE below produces two pages with different kernings b-o and o-w.
(I have observed the same with \ss\it but not with \tf\bi or \tf\it.)

Viewed by three viewers. As evince and pdffonts report, only one font (LMSans10-BoldOblique) was loaded.
(All lmsans10-boldoblique.otf files on my computer since 2022 are the same.)

I cannot figure out why these two snippets give different result.
Could someone please explain? Or is it just a display/eye issue?

Best,

Tomáš 

%%%%%%%%%%%%%%%%%%%%%%%%
% Tested on: 
%   TL2025
%   ConTeXt ver: 2025.11.24 17:55
%   ConTeXt ver: 2024.06.21 23:45 LMTX (at c-o-w)
% Viewed by: xpdf, evince, mupdf
%%%%%%%%%%%%%%%%%%%%%%%%

\definefontfamily
  [mainface]

\starttext
  \startTEXpage[offset=3dd]
     \switchtobodyfont[modern,1cc]
     \ss\bi bowling
  \stopTEXpage
\page
  \startTEXpage[offset=3dd]
    \switchtobodyfont[mainface,1cc]
    \ss\bi bowling
  \stopTEXpage
\stoptext
%%%%%%%%%%%%%%%%%%%%%%%%
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[NTG-context] Re: Question to kernings (modern, sans, \bi)

[Pablo Rodriguez via ntg-context]

On 2/26/26 20:23, Tomáš Hála wrote:
> Hi all,
> 
> the MWE below produces two pages with different kernings b-o and o-w.
> (I have observed the same with \ss\it but not with \tf\bi or \tf\it.)

Hi Tomáš,

I think `\rm` would be the matching switch for `\ss` (roman and sans-serif).

> Viewed by three viewers. As evince and pdffonts report, only one
> font (LMSans10-BoldOblique) was loaded. (All lmsans10-
> boldoblique.otf files on my computer since 2022 are the same.)>
> I cannot figure out why these two snippets give different result.
> Could someone please explain? Or is it just a display/eye issue?

I can perceive a difference in “Evince” at 6564.6% zoom (and continuous
mode) compiling your original sample (no display or view glitch).

It disappears when I replace your first command with:

  \definefontfamily
    [mainface]
    [ss]
    [Latin Modern Sans]

I wonder whether by not defining properly the font family
(https://www.pragma-ade.com/general/qrcs/setup-en.pdf#search=definefontfamily
shows that the these first three brackets are required) may influence
how the font has its features enabled or not (kerning among them).

Sorry, it’s only a(n educated?) guess. Just in case it may help,

Pablo
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[NTG-context] Re: Question to kernings (modern, sans, \bi)

[Wolfgang Schuster]

Am 26.02.2026 um 20:23 schrieb Tomáš Hála:
> Hi all,
> 
> the MWE below produces two pages with different kernings b-o and o-w.
> (I have observed the same with \ss\it but not with \tf\bi or \tf\it.)

\tf and \ss are doing two different things, \tf is the switch to the 
switch to the upright alternative in a font style while \ss switches to 
the sans serif style.

Font alternatives: \tf, \it, \sl, \bf, \bi and \bs

Font styles: \rm, \ss and \tt

> Viewed by three viewers. As evince and pdffonts report, only one font (LMSans10-BoldOblique) was loaded.
> (All lmsans10-boldoblique.otf files on my computer since 2022 are the same.)
> 
> I cannot figure out why these two snippets give different result.
> Could someone please explain? Or is it just a display/eye issue?
> 
> Best,
> 
> Tomáš
> 
> %%%%%%%%%%%%%%%%%%%%%%%%
> % Tested on:
> %   TL2025
> %   ConTeXt ver: 2025.11.24 17:55
> %   ConTeXt ver: 2024.06.21 23:45 LMTX (at c-o-w)
> % Viewed by: xpdf, evince, mupdf
> %%%%%%%%%%%%%%%%%%%%%%%%
> 
> \definefontfamily
>    [mainface]

You're setting a font without specifying the style or font name.

Because no style has been set the default style "rm" is used and because 
no font has been set nothing can be found, which results in the fallback 
selection of the "modern" typeface.

What you get here is the same as the following typeface setting:

\definetypeface [mainface] [rm] [serif] [modern] [default]

> \starttext
>    \startTEXpage[offset=3dd]
>       \switchtobodyfont[modern,1cc]
>       \ss\bi bowling
>    \stopTEXpage
> \page
>    \startTEXpage[offset=3dd]
>      \switchtobodyfont[mainface,1cc]
>      \ss\bi bowling

You're switching to the sans serif style which hasn't been defined in 
your custom "mainface" typeface where only a serif style has been set.

Wolfgang

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[NTG-context] Re: Question to kernings (modern, sans, \bi)

[Tomáš Hála]

Thanks to Pablo and Wolfgang for quick reactions, it is clearer to me now.

(The issue with \tf can be skipped, I was too deep in the problem that I did not realise that it does not make sense.)

> >\starttext
> >   \startTEXpage[offset=3dd]
> >      \switchtobodyfont[modern,1cc]
> >      \ss\bi bowling
> >   \stopTEXpage
> >\page
> >   \startTEXpage[offset=3dd]
> >     \switchtobodyfont[mainface,1cc]
> >     \ss\bi bowling

> You're switching to the sans serif style which hasn't been defined in
> your custom "mainface" typeface where only a serif style has been set.

Ok. The sans bold italic font was still loaded and used and I expected that
the font has been loaded with its kernings but it seems that it is not true.
Where are the kernings read in this case from?

I am just asking because the kernings between b-o and o-w in my (incorrect)
example looks better than the original ones where (imo) the "o" is moved to the right too much.

Tomáš

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[NTG-context] Re: Question to kernings (modern, sans, \bi)

[Pablo Rodriguez via ntg-context]

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On 2/27/26 03:37, Tomáš Hála wrote:
> […]
> Where are the kernings read in this case from?

They come from the font, actually they come from the (GPOS) `kern` table
of `lmsans10-boldoblique.otf`.

> I am just asking because the kernings between b-o and o-w in my
> (incorrect) example looks better than the original ones where (imo)
> the "o" is moved to the right too much.

See the attachments: with and without kern tables.

Kerning value of -31 of 'w' after 'o' may make sense (in “owl”), but a
value of 31 of 'o' after 'b' doesn’t make sense at all (see “bow”).

The same happens (with values of -28 and 28) with `lmsans10-oblique.otf`.

After checking `lmsans10-bold.otf` and `lmsans10-regular.otf` (all from
`tex/texmf/fonts/data/gust/lm/`): obliques share these kerning values
from their upright and bold counterparts.

I have checked that there is a 2.006 version
(https://www.gust.org.pl/projects/e-foundry/latin-modern/download/lm-hist.txt/view).
Although we use the 2.004, this issue isn’t fixed in latest version.

According to the README
(https://www.gust.org.pl/projects/e-foundry/latin-modern/download/readme-latin-modern.txt/view),
Bogusław Jackowski is the LM maintainer, so I guess an email message to
him would be the way to report the issue (at least, I was unable to find
any other way to report an issue).

Many thanks for hitting (what seems to be) an issue with the LM fonts,

Pablo

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[NTG-context] Re: Question to kernings (modern, sans, \bi)

[Tomáš Hála]

> Bogusław Jackowski is the LM maintainer, so I guess an email message to him would be the way to report the issue ...
> Many thanks for hitting (what seems to be) an issue with the LM fonts,

Reported to Jacko.

Thanks once more.

Tomáš
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