[HarfBuzz] Mai Kang Lai in Tai Tham, summary draft

[Richard Wordingham]

On Mon, 20 May 2013 15:08:19 +0700
Theppitak Karoonboonyanan <thep at linux.thai.net> wrote:

> Hi again,
> 
> I have drafted a summary for Mai Kang Lai in Tai Tham as we have
> discussed so far.
> 
>   http://linux.thai.net/~thep/esaan-scripts/tham-issues/mai-kang-lai.html
> 
> With this, I have also added some more evidences for Lanna I have
> found. Please add if I still miss something.

For the recoding solution, you wrote:

"A possible workaround is to exclude LA from the above rule. This is
quite safe because NGA and LA are never conjoined in Pali grammar."

While Pali doesn't have -ṅl- or -ṃl-, we do have Sanskrit influence
to contend with.  Thus, although Pali for 'masculine' is _pullinga_, the
MFL lists <BA, U, MAI KANG, LA, I, NGA, SAKOT, LOW KA> ปุงลิงคะ with
this meaning. Given the dictionary's spelling habits, I half expected to
see MAI KANG LAI sitting on the BA.  I don't think we can rely on MAI
KANG LAI never sliding forward onto a LA.

If we're going to go for a coding solution, I'd rather go for a new
character.  However, out of ignorance, I have to ask - are non-shifted
MAI KANG LAI and CONSONANT SIGN NGA different?  Lao Tham suggests they
might be the same thing.

Another conceivable solution you mention is, "Fonts for Lao Tham and
the shifting school of Lanna may provide GSUB rule to reorder Mai Kang
Lai themselves."

This goes against what I first learnt about GSUB.  I suppose it is
tied up with how one handles editing of clusters of characters.
Perhaps I'm just a semi-literate foreigner, but I frequently find
myself having to edit 'legacy grapheme clusters'.  It's helpful when
the cursor actually shows me where I am within the cluster - but that
can only be done if the connection between characters and glyphs is
maintained.  Using GSUB to change the order of characters destroys that
information, which is why reordering is supposed to done by the
script-specific shaping logic.

I still haven't equipped myself to experiment with GPOS as a way of
correcting the minor deficiencies of shaping.  I'm about two weeks away
at my current rate of progress.

However, I think we are at a point where Behdad can say what he thinks
of the 'rphf' option.

Richard.