···<date: 2013-10-01, Tuesday>···<from: Khaled Hosny>···

> On Tue, Oct 01, 2013 at 11:20:52AM +0200, Hans Hagen wrote:
> > On 10/1/2013 10:05 AM, Marco Patzer wrote:
> > >On 2013–09–30 Hans Hagen wrote:
> > >
> > >>these are unrelated mechanisms where the first one just does some
> > >>pdf magic ... no feedback to tex about widths (ok, i could write
> > >>something better but never had and still don't have a reason for
> > >>that kind of low level pdf based approach to be really deeply
> > >>integrated)
> > >
> > >Thanks for the explanation. I was looking for a way to do slight
> > >letter spacing without breaking ligatures and thought I could
> > >leverage the stretch effect for that.
> > 
> > well, we break ligatures because ligatures make no sense in that
> > kind of kerned text (if they make sense at all, but that's a
> > different issue
> 
> Some ligatures should not be broken in letter-spaced text, typically
> represented by rlig in OpenType, e.g. Fraktur ch, ck, ſt and tz
> ligatures:
> http://unifraktur.sourceforge.net/letterspacing.html
 

When using the characterkerning method you can exempt ligatures
and character pairs from being letterspaced by defining the
functions typesetters.kerns.keepligature (<liganode>) and
typesetters.kerns.keeptogether (<prevglyph>, <glyph>),
respectively. If the function returns a truish value for the
given input, ligatures won’t be decomposed and no extra kerning
will be applied.

Best regards
Philipp