[NTG-context] font expansion MkXL vs. MkIV

[Hans Hagen]

On 2/16/2020 9:22 PM, Pablo Rodriguez wrote:
> Hi Wolfgang and Hans,
> 
> I have the following sample:
> 
>      \setuppapersize[A5]
>      \definefontfeature[default][default]
>          [protrusion=quality, expansion=quality]
>      \definefontfamily[mainface][rm][Source Serif Pro]
>      \setupalign[hanging, hz]
>      \setupbodyfont[mainface, 17pt]
>      %~ \setupbodyfont[helvetica, 17pt]
>      \starttext
>      \input zapf
>      \stoptext
> 
> hz doesn’t work fine in MkXL, but it works fine in MkIV.
> 
> I think the flow of characters is broken in MKXL. Some
> 
> With TeX Gyre Heros (https://pdf.ousia.tk/mkiv-hz.pdf and
> https://pdf.ousia.tk/mkxl-hz.pdf):
> 
> - "computer": line 5.
> - "basic": line 8.
> - "showing": line 10.
> 
> With Source Serif Pro, also (https://pdf.ousia.tk/ssp-mkiv-hz.pdf and
> https://pdf.ousia.tk/ssp-mkxl-hz.pdf):
> 
> - "publishing": line 2.
> - "about": line 4.
> - "between": line 10.
> 
> I’m experiencing this wherever I use hz with MkXL.
> 
> Sorry, but cannot the default values for quality font expansion be the
> same in MkIV and MkXL?
> 
> Many thanks for your help,
in lmtx there is more precise handling of edge cases (protrusion) that 
are ignored in mkiv ... so any difference that you observe can simply be 
a side effect of tex deciding otherwise (because these calculations do 
influence linebreaks)

anyway, you should use 'stretch' to because otherwise expansion and 
protrusion has not enough options to do better (the linebreak third pass 
that is)

\setupalign[hanging, stretch, hz]

Hans

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