[XeTeX] On combining diacritics again

[Florian Grammel]

After reading this thread I think I have understood the odd (i.e.  
varying between TextEdit and XeLaTeX) diacritic placements that were  
puzzling me. But as I need a wide range of PUA-characters from a  
special font, using Doulos SIL or any other font unfortunately isn't  
a solution for me. So I was wondering whether anybody here could help  
me out with a workaround for the problem...

I was thinking of two ways, but don't have the technical skills to  
realize them:

Wouldn't it be very practical -- as there are so few fonts with the  
proper AAT-support -- to make XeTeX imitate Cocoa's font-behaviour,  
as least when one needs it? As I understand from Jonathan's  
explanations, this isn't feasible on the font-engine level. But might  
be somebody with a better understanding of TeX than me could suggest  
how one could solve this with a sort of macro? When meeting a glyph  
from a certain list (e.g. a combining diacritic), this macro would  
read the dimensions of the antecedent glyph-box and would "kern" the  
diacritic, so that it a) is placed centred in relation to the box and  
b) outside of it.

If none of the experts can be tempted to waste some of their spare  
time to solve this probably not too trivial problem -- I still will  
be looking for a handy way to adjust the placement without fiddling  
with the font itself. I would prefer not to alter the text itself,  
but define the changed placement (vertically or horizontally  
respectively) for a given pair of glyphs once and for all in the  
preamble.


I would be very grateful for any help to get my diacritics to behave!

Best wishes,

Florian.