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

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 15 Mar 2015 23:15:56 +0000
> From: Richard Wordingham <richard.wordingham@ntlworld.com>
> 
> Eli Zaretskii wrote:
> 
> > Only this should be necessary:
> >
> >  1) Modify fontset.el to add the script.
> 
> Is this meant to be relevant to the use of Emacs 24?  In Emacs 24, Tai
> Tham is already listed in fontset.el.

Sorry, you are right.  I've misread that line to mean you want to
change the setup of the default fontset, not that you want to add the
script (which is already recognized by default).

> The examples in 'modifying fontsets' seem to be irrelevant, and
> certainly didn't help.  I may be missing something subtle, but I was
> already picking up the right font, and adding it to the default fontset
> does not seem to make any difference, in either Emacs 23.3.1 or Emacs
> 24.

Then what exactly is/was your problem with that script?  Your question
said:

> Is it 'simple' to add complex text layout (CTL) for the Tai Tham
> script on non-Windows systems?

Emacs does CTL on Unix by using 2 m17l libraries.  Here's a citation
from INSTALL:

  * Complex Text Layout support libraries

  On GNU and Unix systems, Emacs needs the optional libraries "m17n-db",
  "libm17n-flt", "libotf" to correctly display such complex scripts as
  Indic and Khmer, and also for scripts that require Arabic shaping
  support (Arabic and Farsi).  On some systems, particularly GNU/Linux,
  these libraries may be already present or available as additional
  packages.  Note that if there is a separate `dev' or `devel' package,
  for use at compilation time rather than run time, you will need that
  as well as the corresponding run time package; typically the dev
  package will contain header files and a library archive.  Otherwise,
  you can download the libraries from <http://www.nongnu.org/m17n/>.

  Note that Emacs cannot support complex scripts on a TTY, unless the
  terminal includes such a support.

But you seem to have these libraries already, so I'm unsure what
exactly is the problem you are having.

> Might the character categories be relevant?  They don't seem to be set
> for Tai Tham characters, though they are set for Tai Viet characters,
> which are slightly younger.

Which categories did you have in mind?  "Category" is too general a
term here.

> I also notice that a sequence of Thai consonants does not prompy any
> m17n action, but that m17n action occurs as soon as a combining
> character (vowel, tone mark etc.) is entered.

If the problem is with character compositions (is it?), then perhaps
the corresponding rules are not defined yet, and should be added.  Or
maybe the versions of those libraries you have don't yet have support
for Tai Tham.

Bottom line, I think I'm confused about the problems you are trying to
solve, so please elaborate on them.