Re: Adding Tai Tham Script to GNU/Linux Distribution's Version of Emacs

[Richard Wordingham]

On Wed, 18 Mar 2015 08:27:37 +0000
Richard Wordingham <richard.wordingham@ntlworld.com> wrote:

> On Mon, 16 Mar 2015 18:34:03 +0200
> Eli Zaretskii <eliz@gnu.org> wrote:
> 
> > My guess is that you will have to write a tai-tham.el file with
> > similar data for Tai Tham, and then load it into Emacs.  All the
> > rest should "just work".

> It's now mostly working, but with some strange anomalies.

The problem is that function font-shape-gstring, defined in file
font.c, which *appears* to be the correct composition function, does not
grok the m17n FLT module, or at least not at Version 1.6.3.  A work
around appears to be declare all the strings passed to m17n by Emacs as
grapheme clusters, which can be done by the special symbols < > in the
FLT generator commands.  I'm preparing a bug report.  Without the < >
symbols, the 'composition' of swapping consonant and vowel round to
convert from logical and phonetic order to visual order is declared to
be a shaper error!

I detest grapheme clusters.  I refuse to believe that in a Tai
language, the users consider every combination of consonant, vowel and
tone as a single letter.  Indeed, there were howls of outrage when the
practical effects of Unicode declaring a Thai preposed vowel plus
consonant to be a grapheme cluster struck, and the standard was
rapidly reversed.

Richard.