Didier Verna writes:
... especially the process of deciding which area really needs to be
updated. For instance, change the default face background
pixmap specifier for say, a buffer "foo", and switch from and
to this buffer a bit.
We should remember that some of this stuff has never worked
right. Your example certainly hasn't. The problem here is the
lack of a proper internal notification of the change. I think
the problem is general to locale-specific face changes, as
opposed to domain-specific changes.
I haven't found redisplay problems hard to fix, but there is a
long period of study required before it becomes obvious where to
look to fix problem. This study would still be required if we
were to do a rewrite, alas, because Emacs has some historical
display behavior that we would have to duplicate.