[XeTeX] misplaced diacritical marks

[Alexander Schultheiß]

Hey,

I'm new to xetex/xelatex and I have problems with diacritical marks. I
found another thread describing a similar problem but the original
question sadly isn't addressed
(http://tug.org/pipermail/xetex/2004-August/000668.html).

Does xelatex honor anchors in GPOS tables of otf/ttf fonts? If I try
to place, say, a macron above an 'a' as well as a dot below it one of
the two diacritical marks is always misplaced; depending on the oder
of xelatex commands:

\d{\={a}} dot misplaced
\={\d{a}} macron misplaced

I tried it with my own font as well as with Junicode. The problem does
not depend on the choice of font, it seems. Also, if I try to place an
acute above a+macron the diacritics do not stack. Even worse, if
a+macron is not pre-composed within the font, xelatex is unable to
assemble it (Why?!). So my suspicion is that xelatex doen't honor
anchors within GPOS tables. Is this correct or do I miss something? If
correct, is there a way to make xelatex recognize anchors?

Thanks