[XeTeX] bug in polyglossia/sanskrit? (problem with diacritical marks)

[Zdenek Wagner]

Hi,

I can do it later this afternoon and I know how to build FreeFont from
your svn repo.

Zdeněk Wagner
http://ttsm.icpf.cas.cz/team/wagner.shtml
http://icebearsoft.euweb.cz

čt 16. 5. 2019 v 23:00 odesílatel Steve White <stevan.white at gmail.com> napsal:
>
> Hi,
>
> I looked through the attachments to the previous postings, and some of the
> images are consistent with the positioning feature being turned off.
> That may now be fixed for FreeSerif.
>
> However there were some that showed a completely wrong mark appearing,
> far from the base mark.  I have no idea what that might be, but it's
> hard for me to tell
> just what fonts were causing which problems.
>
> Could somebody please systematically make images of
>
>     TL 2017  vs  2018
>     fonts  FreeSerif  vs  Sanskrit 2003  vs  Murty Sanskrit
>
> If anybody needs a recent build of GNU FreeFont,  I can provide that.
>
> Thanks!
>
>
> On Thu, May 16, 2019 at 10:43 PM Steve White <stevan.white at gmail.com> wrote:
> >
> > Hi Jonathan,
> >
> > You may have a point, although I don't think it's the whole story.
> >
> > (Most of what follows is font-techy. Upshot is: I did find suspicious
> > issues in FreeFont, and have now fixed them.)
> >
> > The font feature in FreeSerif that positions generic marks like these is
> >
> > mark ('generic marks above')
> >
> > Indeed the 'dev2' script was different from the 'deva' script, being set
> > nly for language 'dflt'.  That is formally a bug, but I don't see why it
> > would matter here, as the "script" in which the problem happens is Latin
> > (the base characters beinig from the Latin range).
> >
> > However, now that I look at the 'latn' script entries for that same feature...
> > it lacks the 'SAN ' language.  As I understand the logic, that would
> > result in the feature not being applied.
> >
> > Now in the case of FreeFont, that should result in the mark crudely
> > appearing over the preceding character without GPOS placement, as these
> > marks have negative right bearing.
> >
> > I have fixed these issues in FreeFont SVN.
> >
> > It will be interesting to hear if they alleviate the issue in the newer
> > version of TL.  It might suggest triggers the effect.
> >
> > Cheers!
> >
> >
> > On Thu, May 16, 2019 at 2:30 PM Jonathan Kew <jfkthame at gmail.com> wrote:
> > >
> > > On 16/05/2019 12:31, Ulrike Fischer wrote:
> > > > Am Mon, 13 May 2019 17:52:17 +0200 schrieb François Patte:
> > > >
> > > >> I have just made a fresh install of texlive 2019 and encountered a
> > > >> problem with the diacritical marks of romanized sanskrit.
> > > >
> > >
> > > Do the 'dev2' script tables in FreeSerif include positioning features
> > > for the various combining diacritics on Latin characters? I'm guessing
> > > not, in which case it's unsurprising that the results will be poor if
> > > you present it with accented Latin, yet request Devanagari shaping behavior.
> > >
> > > I'd expect romanized Sanskrit should be typeset with script=latn, or
> > > with no explicit script specification.
> > >
> > > JK
> > >
> > > > (copied from f.c.t.t):
> > > >
> > > > One can see it with plain xetex too, and it is not the font (I'm
> > > > forcing it to 2018), et it is not xdvipdfmx (it happens with tl19
> > > > and tl18 version). So it is quite probably an xetex engine bug.
> > > >
> > > > A plain xetex example:
> > > >
> > > > \XeTeXtracingfonts=1
> > > > \font\test="[C:/texlive/2018/texmf-dist/fonts/opentype/public/gnu-freefont/FreeSerif.otf]/OT:script=dev2;"
> > > > \test  ā ī ū ṛ ṝ ḷ ḹ ṭ ḍ ṅ ś ṣ ḥ
> > > > \bye
> > > >
> > > >
> > > > Comparing the versions gives
> > > > 2019:
> > > > Compiled with ICU version 63.1; using 63.1
> > > > Compiled with zlib version 1.2.11; using 1.2.11
> > > > Compiled with FreeType2 version 2.9.1; using 2.9.1
> > > > Compiled with Graphite2 version 1.3.13; using 1.3.13
> > > > Compiled with HarfBuzz version 2.3.1; using 2.3.1
> > > > Compiled with libpng version 1.6.36; using 1.6.36
> > > > Compiled with poppler version 0.68.0
> > > > Compiled with fontconfig version 2.13.1; using 2.13.1
> > > >
> > > > 2018:
> > > > Compiled with ICU version 61.1; using 61.1
> > > > Compiled with zlib version 1.2.11; using 1.2.11
> > > > Compiled with FreeType2 version 2.9.1; using 2.9.1
> > > > Compiled with Graphite2 version 1.3.11; using 1.3.11
> > > > Compiled with HarfBuzz version 1.7.6; using 1.7.6
> > > > Compiled with libpng version 1.6.34; using 1.6.34
> > > > Compiled with poppler version 0.64.0
> > > > Compiled with fontconfig version 2.13.0; using 2.13.0
> > > >
> > > > The first suspect is HarfBuzz.
> > > >
> > > >
> > > >
> > > >
> > >
>