`after-change-functions' and undo

[Paul Pogonyshev]

Hi.

I'm having a problem with `after-change-functions' and undo
interference.  My `after-change' hook does magic things to
allow special property inheritance.  So, it can set certain
text properties on an inserted text chunk.

Everything works fine till I start undoing in the buffer.
It seems that `after-change' hook is invoked and, when
undoing a deletion, it sees an insertion and happily starts
mangling text properties.

So, the question is: can I prevent my `after-change' hook
from running while undo is in effect?  I couldn't figure out
from the manual.

Paul