Kerning and ligatures in math roman font

Kerning and ligatures in math roman font

[Ulrike Fischer]

In this example there is no kerning and no ligatures in the math:

\starttext
 WAiff $\mfunction{WAiff}$
\stoptext

This is a different behaviour than with legacy math fonts. 

A question about this has been asked some month ago on tex.sx
(http://tex.stackexchange.com/questions/252493/ligatures-are-not-used-in-opentype-maths-families).
The problem (or feature) exist also with xetex. 

With luatex one can avoid to loose the kerning by loading as math
roman font a font in mode base
(http://tex.stackexchange.com/questions/277362/lualatex-no-kerning-within-operatorname-when-not-loading-lmodern-package/277395#277395,
I have no idea how to do this in context).

Is this a luatex/xetex bug? Or a feature? How could one enable
kerning and/or ligatures without going back to base mode? 


-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/

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Re: Kerning and ligatures in math roman font

[Hans Hagen]

On 11/9/2015 12:39 PM, Ulrike Fischer wrote:
> In this example there is no kerning and no ligatures in the math:
>
> \starttext
>   WAiff $\mfunction{WAiff}$
> \stoptext
>
> This is a different behaviour than with legacy math fonts.

depends what legacy is ...

> A question about this has been asked some month ago on tex.sx
> (http://tex.stackexchange.com/questions/252493/ligatures-are-not-used-in-opentype-maths-families).
> The problem (or feature) exist also with xetex.
>
> With luatex one can avoid to loose the kerning by loading as math
> roman font a font in mode base
> (http://tex.stackexchange.com/questions/277362/lualatex-no-kerning-within-operatorname-when-not-loading-lmodern-package/277395#277395,
> I have no idea how to do this in context).
>
> Is this a luatex/xetex bug? Or a feature? How could one enable
> kerning and/or ligatures without going back to base mode?

most math fonts don't have ligatures etc ... in fact, as ligatures are a 
language/script related feature and math is the script it makes not much 
sense either

in context you can do:

\setupmathematics
   [functionstyle=normal]

which will use a box which then will trigger text fonts

Hans

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Re: Kerning and ligatures in math roman font

[Ulrike Fischer]

Am Mon, 9 Nov 2015 13:13:12 +0100 schrieb Hans Hagen:

>> In this example there is no kerning and no ligatures in the math:
>>
>> \starttext
>>   WAiff $\mfunction{WAiff}$
>> \stoptext
>>
>> This is a different behaviour than with legacy math fonts.
> 
> depends what legacy is ...

I meant the fonts you would get with plaintex or pdflatex.

>> A question about this has been asked some month ago on tex.sx
>> (http://tex.stackexchange.com/questions/252493/ligatures-are-not-used-in-opentype-maths-families).
>> The problem (or feature) exist also with xetex.
>>
>> With luatex one can avoid to loose the kerning by loading as math
>> roman font a font in mode base
>> (http://tex.stackexchange.com/questions/277362/lualatex-no-kerning-within-operatorname-when-not-loading-lmodern-package/277395#277395,
>> I have no idea how to do this in context).
>>
>> Is this a luatex/xetex bug? Or a feature? How could one enable
>> kerning and/or ligatures without going back to base mode?
 
> most math fonts don't have ligatures etc ... in fact, as ligatures are a 
> language/script related feature and math is the script it makes not much 
> sense either

But the plaintex and latex examples on tex.SX don't use a math font
for operatornames like \sin or for \mathrm (which seems to be
\mfunction in context). It is a text font and it has ligatures and
kerning informations, but they are not used in math. 

Doesn't use context for \mfunction a text font too? I thought so
because it has kerning when used outside math:

\starttext
\mfunction{WAiff}

$\mfunction{WAiff}$
\stoptext

Also bad kerning in operator names is a nuisance. I don't think that
the default result of
\definemathcommand[VA][nolop]{\mfunction{VA}} is good looking. 



> in context you can do:
> 
> \setupmathematics
>    [functionstyle=normal]
> 
> which will use a box which then will trigger text fonts

Yes, one workaround is to quit math mode. The other to use fonts in
mode "base". But I would like to understand why workarounds are
needed at all. 


-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/

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Re: Kerning and ligatures in math roman font

[Hans Hagen]

On 11/9/2015 2:06 PM, Ulrike Fischer wrote:

> Yes, one workaround is to quit math mode. The other to use fonts in
> mode "base". But I would like to understand why workarounds are
> needed at all.

because opentype math fonts are just math fonts (simple for text, rich 
for math)

Hans

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                                           Hans Hagen | PRAGMA ADE
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                                              | www.pragma-pod.nl
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Re: Kerning and ligatures in math roman font

[Ulrike Fischer]

Am Mon, 9 Nov 2015 14:22:45 +0100 schrieb Hans Hagen:

>> Yes, one workaround is to quit math mode. The other to use fonts in
>> mode "base". But I would like to understand why workarounds are
>> needed at all.
 
> because opentype math fonts are just math fonts (simple for text, rich 
> for math)

But there is no math font involved. This latex example

\documentclass{article}
\usepackage{fontspec}
\begin{document}
VA $\mathrm{VA}$
\end{document}

uses exactly one font:

<d:/texlive/2015/texmf-dist/fonts/opentype/public/lm/lmroman10-regular.otf>

But outside math it is kerned, inside not. 

And this plain tex example doesn't use math fonts either. 

\input luaotfload.sty

\font\Urm=Arial:mode=node;script=latn;language=DFLT;+tlig;+trep;
\textfont0\Urm
\Urm VA $\fam0 VA$ %no kerning in math

\font\Urmbase=Arial:mode=base;script=latn;language=DFLT;+tlig;+trep;
\textfont0\Urmbase
\Urm VA $\fam0 VA$ %kerning in math
\bye

(I used Arial so that one can see clearly that a text font is used)

-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/

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Re: Kerning and ligatures in math roman font

[Hans Hagen]

On 11/9/2015 2:59 PM, Ulrike Fischer wrote:
> Am Mon, 9 Nov 2015 14:22:45 +0100 schrieb Hans Hagen:
>
>>> Yes, one workaround is to quit math mode. The other to use fonts in
>>> mode "base". But I would like to understand why workarounds are
>>> needed at all.
>
>> because opentype math fonts are just math fonts (simple for text, rich
>> for math)
>
> But there is no math font involved. This latex example
>
> \documentclass{article}
> \usepackage{fontspec}
> \begin{document}
> VA $\mathrm{VA}$
> \end{document}
>
> uses exactly one font:
>
> <d:/texlive/2015/texmf-dist/fonts/opentype/public/lm/lmroman10-regular.otf>
>
> But outside math it is kerned, inside not.
>
> And this plain tex example doesn't use math fonts either.
>
> \input luaotfload.sty
>
> \font\Urm=Arial:mode=node;script=latn;language=DFLT;+tlig;+trep;
> \textfont0\Urm
> \Urm VA $\fam0 VA$ %no kerning in math
>
> \font\Urmbase=Arial:mode=base;script=latn;language=DFLT;+tlig;+trep;
> \textfont0\Urmbase
> \Urm VA $\fam0 VA$ %kerning in math
> \bye
>
> (I used Arial so that one can see clearly that a text font is used)

you don't enable kerning but anyhow, here is a context example:

\usemodule[oldotf]

\starttext

\showfontkerns

\font\Urm=arial:mode=node;+tlig;+trep;+kern;
\font\Urm=lmroman10-regular:mode=base;+kern;
\textfont0\Urm
\Urm VA $\fam0 VA$

\stoptext

basemode should work (no node mode in math but features are normal 
simple ... keep in mind that node lists in math are quite different)

Hans



-- 

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                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
     tel: 038 477 53 69 | voip: 087 875 68 74 | www.pragma-ade.com
                                              | www.pragma-pod.nl
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Re: Kerning and ligatures in math roman font

[Ulrike Fischer]

Am Mon, 9 Nov 2015 16:44:34 +0100 schrieb Hans Hagen:

> you don't enable kerning but anyhow, 

In text mode kerning seems to be activated by default, but it
doesn't change the output if I add it.

> here is a context example:

Curious, here I get no kerning at all for arial. I tried all sort of
variants but the distance between V and A is wider then with
plaintex and \showfontkerns give no output. 


-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/

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