[HarfBuzz] Exposing attachment tree / Arabic joining to shaping clients

[Behdad Esfahbod]

On Tue, Nov 12, 2019 at 7:31 PM Martin Hosken <mhosken at gmail.com> wrote:

> Dear Behdad,
>
> > For reason that many of you know (letter-spacing, Arabic elongation,
> other
> > postprocessing) I like to expose attachment data to the shaping clients.
> > There's two separate pieces so far:
> >
> > - The Arabic joining info, which is applicable to all Arabic-like fonts
> > even the ones that do NOT use cursive joining.
> >
> > - Mark attachment and cursive attachment.  These form a tree with a
> > attachment-type enum.
> >
> > I'm not sure which slots in the pos buffer to expose this in.  The latter
> > definitely belongs to the pos buffer, whereas the former is more a
> property
> > of the text.  So I feel like we should expose them separately.
> >
> > Ideas?
>
> Pulling back into the more generic script question, I think both may be
> covered by giving the attachment parent and attachment type. Thus Arabic
> joining is via cursive attachment


Except that simple linear Arabic-like fonts don't do cursive joining.
Letters just line up next to each other.


> and diacritic attachment via mark attachment. IMHO, this would then also
> apply naturally to other scripts and give some help with regard to
> justification.
>
> Yours,
> Martin
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-- 
behdad
http://behdad.org/
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