Hi,
The story seems that when XeTeX inserts tokens due to
\XeTeXinterchartoks it has already read the character at the
right side of the insertion point for update of the space
factor value.
\newXeTeXintercharclass \cclA
\newXeTeXintercharclass \cclB
\newXeTeXintercharclass \cclC
\XeTeXcharclass
Hi,
=
\newXeTeXintercharclass \mycharclassA
\newXeTeXintercharclass \mycharclassP
\XeTeXcharclass `\A \mycharclassA
\XeTeXcharclass `\. \mycharclassP
\XeTeXinterchartoks \mycharclassA \mycharclassP = {\relax}
\XeTeXinterchartokenstate = 0
A\relax.\the\spacefactor % 1000; ok.
\XeTeXinterchart
