[NTG-context] Broken kerning if hz is turned on?

Hans Hagen j.hagen at xs4all.nl
Sun Jun 2 12:45:16 CEST 2019


On 6/2/2019 8:36 AM, Mikael P. Sundqvist wrote:
> On Mon, May 20, 2019 at 9:55 PM Wolfgang Schuster 
> <wolfgang.schuster.lists at gmail.com 
> <mailto:wolfgang.schuster.lists at gmail.com>> wrote:
> 
>     Mikael P. Sundqvist schrieb am 20.05.2019 um 21:41:
>      > Hi,
>      >
>      > attached is the result of running latest lmtx on
>      >
>      >
>     \definefontfeature[default][default][protrusion=quality,expansion=quality]
>     \definefontfeature [default] [default] [threshold=20,expansion=quality]
>      > \setupalign[hz]
>      > \setupbodyfont[lucidaot]
>      >
>      > \starttext
>      > Gauss öppnade med denna studie ett helt nytt fält inom matematiken,
>      > det som
>      > handlar om \emph{elliptiska funktioner} och \emph{modulära former}.
>      > \stoptext
>      >
>      > What happens with the space between the characters in "studie", that
>      > becomes "s tudie"? The spacing between some other characters are
>     also
>      > off (ma tematiken), but not as much as in studie.
>     It's a problem with Lucida Opentype which lacks kerning (I reported the
>     same problem a while ago).
> 
>     Wolfgang
> 
> 
> 
> Hi,
> 
> thank you Wolfgang (I just realized I only sent my thank you to you 
> privately)!
> 
> Your threshold=20 solved that particular case. But look at the following 
> example:
> 
> \definefontfeature[default][default][threshold=20,protrusion=quality,expansion=quality,lnum=yes,itlc=yes]
> 
> \setupalign[hz,hanging,line,height]
> 
> \definebodyfontenvironment[9bp][interlinespace=12bp]
> \setupbodyfont[lucidaot,9bp]
> 
> \starttext
> Gränsvärde föreligger i en inre punkt i definitionsmängden om och endast
> om höger- och vänstergränsvärde existerar där och är lika.
> \stoptext
> 
> I attach the output (latest lmtx). The word "endast" shows up as "endas t".
> 
> So, what does this threshold do? I can play with the 20. If I change it 
> to 5 it looks better here (not perfect), but my document is approx. 250 
> pages, so, I fear it will break somewhere else...
> 
> I hope that this does not mean that the Lucida font turns out to be 
> useless :(
Lucida does without kerning so where in other fonts we have more of less 
tight boundingboxes + kerns, in lucida we have large side bearings and 
in that case widening works out a bit different visually (thicker 
vertical strokes as usual with hz + expanded built in side bearings), 
definitely on screen.

Now, one thing that happens in the backend is that glyphs are output as 
sequences and scaled as whole and occasionally the starting points get 
synchronized .. this is what threshold deals with.

Anyway, I might improve thinsg over time as in context lmtx we have a 
bit more control over matters.

One can argue if intercharacter kerns have to be stretched in other 
cases but in context that is configureable.

Hans

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