missing characters: combining marks above runs of more than 2 base letters

How can we encode long runs of characters surrounded by an inverted
breve, when there are more than 2 characters in the run ?
For now we can use combining half marks for macrons, but the
conjoining behavior of the combining conjoining macron is not
warrantied with womething else than half-marks for the macron itself,
and does not apply to the combining inverted breve half marks, or the
combining tilde half marks.

One example here, where it is used to denote what is called in French
"scansion", i.e. for marking how versified syllables are pronounced
and counted in classical poems in Latin :

http://fr.wikisource.org/wiki/Page:Mommsen_-_Histoire_romaine_-_Tome_1.djvu/321

For rendering it, the page had to use a quirk, documented in a
template (http://fr.wikisource.org/wiki/Mod%e8le:Multiligature), i.e.
using combining half marks only for the first and last character, and
then joining them with an adjusted top border. I don't fill this is
really "plain-text".

Could the Unicode text specify that a left half mark, when it is
followed by a right half-mark on the same line, has to be joined ? And
which character can we select in a font to mark the intermediate
characters between them ?

Also, on the same page, I am wondering if the other combining signs
appearing on the last line of the quoted poem, for noting the exact
"scansion" tones are really all acute accents (I think that there's a
distinct sign for the low-raising tone that appears above a thick
line), and if the few curved separators on the baseline are really
liaison symbols (which should then be below the base line).

-- Philippe.
Received on Fri Nov 18 2011 - 01:36:00 CST