[XeTeX] New Hyphenation for Phonemic Orthographies for English?

[Kenneth Reid Beesley]

   New Hyphenation for Phonemic Orthographies for English?


First, a hearty thanks to Jonathan Kew and all involved in
   creating and supporting XeTeX.  I'm using it successfully,
   with my own OpenType Font (created with FontForge) to
   typeset documents in the Deseret Alphabet.  I'm also using
   it with the Charis SIL font to typeset International Phonetic
   Alphabet.

My current project sets Deseret Alphabet and International
Phonetic Alphabet in parallel columns, and I need to define
hyphenation for both.  Too many long words are splaying over
the right margins.  The language is English, but written in
two separate phonemic-alphabet orthographies.  In the future,
might need hyphenation for the Shavian Alphabet as well.

   Q1:  What's the best approach to defining possible hyphenation
   points for English words written in these orthographies?  The Deseret
   Alphabet and Shavian characters lie in the supplementary Unicode space,
   so whatever scheme I adopt would need to handle supplementary
   characters.

   Q2:  Is it possible to specify globally that the end of an em-dash is
   a possible hyphenation point in text?

I'm an average LaTeX user, not a low-level TeX hacker, so any
advice from the experts would be most appreciated.

   Ken Beesley