Re: Hyphenation patterns and adjusted kerning: ConTeXt vs. LuaTeX

[Hans Hagen <pragma@wxs.nl>]

On 25-2-2011 1:18, Heilmann, Till A. wrote:
> Maybe the ConTeXt community can be of assistance to the LuaTeX bunch ...
>
> As a new LuaTeX user, I came across the following problem: Using Lua(La)TeX, customized kerning of letter pairs (via the FeatureFile capability of fontspec) is ignored when it coincides with a possible hyphenation of a word (e.g. between 'f' and 'h' in German words like 'aufhalten'; see first minimal example below).
>
> Ulrike Fischer was so kind to point out two things (http://tug.org/pipermail/luatex/2011-February/002569.html): First, the problem seems to be the break points between the adjusted kerning pairs. Second, ConTeXt seems to handle this case correctly (see second minimal example below; feature file bonum.fea from first example required).
>
> I am no expert in neither LuaTeX nor context, but Ulrike suggested I post here and ask if the (typographically correct) ConTeXt behavior or solution can be reproduced with Lua(La)TeX.
>
> Thanks,
> - Till
>
> 1. Lua(La)TeX
>
> \begin{filecontents*}{bonum.fea}
> languagesystem DFLT dflt;
> languagesystem latn dflt;
> feature kern {
> pos f h 100;
> } kern;
> \end{filecontents*}
> \documentclass{article}
> \usepackage[ngerman]{babel}
> \usepackage{fontspec}
> \setmainfont[FeatureFile=bonum.fea]{TeX Gyre Bonum}
> \begin{document}
> fh aufhalten
> \end{document}

I cannot test that (I only have the context minimals installed) but I 
don't know anything about latex internals so it would be a wild guess. 
Maybe babel is interfering?  In base mode kerning and and hyphenation 
happen in the traditional tex way, so there is not much extra trickery 
taking place.

> 2. ConTeXt
>
> \mainlanguage	[de]
> \definefontfeature[test][featurefile=bonum,kern=yes]
> \definefont[test][name:texgyrebonum*test]
> \starttext
> \test fh aufhalten
> \stoptext

Indeed I see a kern.

Hans

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