What is the best way to work around the current USE CV+C limitation in Tai Tham?

[Richard Wordingham via Unicode]

On Wed, 22 May 2019 00:14:57 -0400
Ed Trager <ed.trager at gmail.com> wrote:

> I'm hoping one or both of you can provide me some guidance on this,
> thank you! Unfortunately, my OpenType skills are not at the "ninja"
> level required to get around all of the limitations in USE ...

If blind copying of Lamphun or Da Lekh, which I allow and encourage in
this respect, is not possible, then one can reduce the skill level in
one ways. One is to indiscriminately eliminate dotted circles that
follow marks; that would simplify the conditions in those fonts.  (I
know that eliminating dotted circles present in the original string is
wrong - it's collateral damage in opposing oppression.)

Unfortunately, it's not as simple as that.  If the USE is still
misclassifying the InSC medial consonants as USE-medial consonants,
then they can still leave one with the need to do Indic reordering in
the font, e.g. with the reflexes of <consonant>/ria/, to be encoded
<consonant, MEDIAL RA, SAKOT, LOW YA, SIGN E>, as the dotted circles
prevent SIGN E reordering to the start of the cluster. 

The second way is to attack individual cases.  For example, one
probably get away with a special substitutions to repair the HarfBuzz
and Windows corruptions of ᨯᩪᩕᩣ.  I don't know if CoreText has yet
another corruption.

Richard.