Also, in the commonly used Hebrew *transliteration*, the same function
(fricative pronunciation) is indicated by a macron above g and p but
below b, d, k and t, for the same reason. It occurs only with these
letters (sometimes also written below h). There might be an argument for
using instead of g and p plus combining macron g and p plus combining
line below - especially as if these were ever capitalised the line would
probably be moved below. But there would need to be a clear rule that
such combining marks are moved from below to above g and p.
The argument makes sense but I think the example should be reversed.
For _b_, _d_, _k_ and _t_ but not _h_ precombined forms with an underbar already appear in Unicode in the Latin Extended Additional section with canonical decompositions to the letter followed by U+0331 COMBINING MACRON BELOW.
I have seen transliterations which used an underbar with _p_ and _g_, either below the descender or passing through the descender. Either could be produced by U+0331 depending on how the font handled this diacritic for characters with descenders.
Accordingly the Unicode analysis of such combinations fits my own intuitive feeling that the low position is the normal position for a diacritic bar indicating fricative pronunciation. The occasional placing of the bar above the letter is the exception for typographical reasons.
In meaning this bar below a stop character is essentially identical in meaning to a bar placed through a stop character. This is also seen and a few of these combinations are covered by Unicode. What we really have is a fricative indication bar that can be placed under a stop character or through a stop character (sometimes diagonally) to indicate a fricative (or sometimes affricate) pronunciation.
Unicode encodes U+1E20 and U+1E21 as combinations of lower and uppercase _g_ with macron. The forms have canonical decomposition to _g_ or _G_ followed by U+0304. This seems to rule out being able to consider a bar above and a bar below as variants of the same character within Unicode.
There is no composite character encoded for _p_ or _P_ with either U+0304 or U+0331.
IPA specifications also indicate that U+0325 COMBINING RING BELOW and some other diacritics normally placed beneath a character may instead be displayed above a character for typographical reasons.
But Unicode specifications currently say nothing about the possibility of moving under-diacritics to an over-character position for typographical reasons except for combination of _g_ and cedilla. Of course if diacritics are so moved then combining classes are even more broken than they seem to be now. This one exception is already a problem in theory though probably not in practice.
Perhaps we need instead special search folding between upper position and lower position diacritics that are otherwise identical in form, e.g. between U+0304 (COMBINING MACRON) and U+0331 (COMBINING MACRON BELOW), between U+ 030A (COMBING RING ABOVE) and U+0325 (COMBINING RING BELOW) and so forth for any diacritics where an upper form and a lower form may have the same meaning.
Jim Allan
