Solution for Extended Tamil

[Richard Wordingham]

On Mon, 22 Jan 2024 20:07:26 +0000
Richard Wordingham via Unicode <unicode at corp.unicode.org> wrote:

> On Mon, 22 Jan 2024 18:23:03 +0000
> James Kass via Unicode <unicode at corp.unicode.org> wrote:
> 
> > Has any effort been made to use OpenType to get the desired
> > display? Classifying the superscripts digits as "marks" in the GDEF
> > (glyph definition) table and then using GPOS (glyph positioning)
> > for the desired placement?  Or has the user community accepted the
> > plain-text legibility of the /de facto/ standard encoding order and
> > reconciled with the fact that not all published books can be
> > exactly rendered in plain-text?  
> 
> I think the first big question is whether the font (envisioned as
> active code) will be presented with letter, non-ligating right matra
> and digit in the same glyph run.

I suppose we should try it, but I have a suspicion that that won't
happen under OpenType.  It might be possible to circumvent the full
application of the script-dependent shaping engine in some renderers by
not supplying any OTL data for the Tamil script, but relying on
definitions for the default script.  While I know that trick for the USE
for Tai Tham will leave us with a feature by default, I don't know
whether that is so for the other rendering engines.  Additionally, the
run might still be restricted to one 'cluster', which would defeat the
font.

Richard.