Distinguishing COENG TA from COENG DA in Khmer script

[Martin J. Dürst]

Hello Richard,

I'm not an expert on OpenType or Khmer (except for having been on the 
side of separately encoding subscript letters in Unicode list 
discussions in the 1990ies), but a few comments and questions below.

On 23/06/2020 20:54, Richard Wordingham via Unicode wrote:
> The modern Khmer language does not make use of a COENG DA distinct from
> COENG TA.  The normal practice is to render them the same, with a
> recommendation from Unicode that the choice be based on the sound the
> subscript represents.  At least, there was such a recommendation; I
> tried to find it again, but failed.  The visual distinction faded out
> in the 1920's according to Antelme.
> 
> Now, the Khmer script is not just used for modern languages of
> Cambodia.  It is used for transcribing Old Khmer (for words, at least)
> and was the religious script of most of Thailand until the 19th
> century, and was also the secular script in southern Thailand.  In
> these usages, COENG TA and COENG DA are distinct, or at least, TA and DA
> have distinct subscripts that are clearly associated with them.
> 
> Is it legitimate for a font to deliberately render the corresponding
> named sequences differently while claiming to respect characters'
> character identities?

A font for Old Khmer,... would do that, wouldn't it? I couldn't see 
anything wrong with that.

> I thought it obviously was, but I received a
> demurral when I asked about the best way to request an arbitrary
> OpenType font to make the distinction.

A truly arbitrary (i.e. arbitrarily choosen) OpenType font probably 
wouldn't cover Khmer anyway, so it would be unable to even start to make 
this distinction.

> (I expect the overwhelming
> majority would refuse to make the distinction.)

The majority of fonts that actually cover modern Khmer might not include 
the relevant glyphs.

> I am therefore asking
> here for advice on the legitimacy of such a request.

I'm guessing that your request was either "How can I coerce a font 
covering modern Khmer to show different glyphs for COENG TA and COENG 
DA?" or "How can I create a font that will allow to show different 
glyphs for COENG TA and COENG DA?"

The reply to the former question is probably "you can't because the font 
doesn't contain the necessary glyph". For the later question, I think it 
should be possible, unless there's some OpenType stuff for Khmer that 
gets in the way.

> Conceivably we need
> a new character to make the distinction.

Do you mean you want to make the distinction in modern Khmer fonts? 
Would that be e.g. for words of Old Khmer that are cited in modern 
Khmer, or something similar?

Regards,   Martin.



> 
> Richard.