Re: how reliable is rendering of complex scripts?

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 04 Oct 2015 10:09:03 +0200 (CEST)
> Cc: emacs-devel@gnu.org, handa@gnu.org
> From: Werner LEMBERG <wl@gnu.org>
> 
> >>   https://github.com/behdad/harfbuzz/tree/master/test/shaping
> >>   https://github.com/behdad/harfbuzz/tree/master/util
> > 
> > I will see if we can extract something from there to see how Emacs
> > displays those scripts.
> 
> The nice thing about `hb-shape' is that it doesn't output graphics but
> a textual representation of the GSUB and GPOS manipulation results
> (including reordering of the input).  In other words, Emacs could use
> the same output format in a special test mode, making comparisons very
> simple – and automated!

Too bad.  It means these tests cannot be easily used by Emacs, because
(1) the shaping engine is not part of Emacs, and (2) to have something
even approximately close, Someone™ will have to add code to
composite.c, composite.el, etc. to produce such a textual description,
and for that, that Someone™ will have to study and understand the code
there enough to write the additions.  Unless Handa-san will find time
to do the main parts of this, of course.

Perhaps a good first step would be for someone to produce pictures of
the rendered texts from those tests (using Harfbuzz or anything else
that can be used as reference), and then we could compare that with
what Emacs produces for the same texts, and see how good or bad we are
doing.

Thanks.