Choosing the Set of Renderable Strings

[James Kass via Unicode]

Richard Wordingham wrote,

⇒ Your example appears to be using the font called 'A Tai Tham KH New'.

Exactly.  The black boxes in the display were becoming tiresome.  The
font package is available from this Tai Tham web page:
http://www.kengtung.org/download-font/

(I'd downloaded a copy of "lamphun.otf", but the installer failed, so
I had to go a-hunting.)

Is it correct to say that the average daily Tai Tham use is already
being more-or-less served by the current state of the fonts and the
USE?  And that many of the problems you are reporting with respect to
things such as mark-to-mark positioning are happening with more exotic
uses of the script, such as the input and display of Pali texts using
the Tai Tham script?

⇒ And how am I supposed to position MAI SAM to the right of the
⇒ rightmost of the level 1 marks above?

Beats me, it's not happening here.  If the GPOS look-up is for (e.g.)
TONE-1 plus MAI SAM, and the string is being re-ordered by the system
to MAI SAM plus TONE-1 before being submitted to the font, then *that*
look-up won't happen.  In which case, change the look-up to accomodate
the re-ordered string.  I suppose you've already tried that.

⇒ The correct sequence is <LOW PHA, SIGN E, SIGN AA, MA, NA, SIGN E,
⇒ SIGN AA>, which is rendered by the Lamphun font as shown in the
⇒ attached PNG file.

ᨽᩮᩣᨾᨶᩮᩣ
To confirm, the NAA ligature isn't happening with the 'A Tai Tham KH New' font.

Changing the entry order to:
ᨽᩮᩣᨾᨶᩣᩮ
<LOW PHA, SIGN E, SIGN AA, MA, NA, SIGN AA, SIGN E>
... forms the NAA ligature and the vowel re-ordering matches the
Lamphun graphic you sent.  But that kludge probably breaks the
preferred encoding model/order.