Private Use areas

[Eli Zaretskii via Unicode]

> Date: Thu, 23 Aug 2018 20:30:52 +0200
> Cc: Richard Wordingham <richard.wordingham at ntlworld.com>
> From: "Janusz S. Bień via Unicode" <unicode at unicode.org>
> 
> >> and in Emacs - to my disappointed it looks like the Unicode data are
> >> set at the compile time, but perhaps this can be negotiated with the
> >> developers.
> >
> > Can you be more specific?
> 
> I often search characters by name with C-x 8 Return. I would like to use
> it also for MUFI characters, I have already the name list (the example
> directory at https://bitbucket.org/jsbien/unihistext/). I haven't looked
> very closely into the problem and don't remember now the details, but my
> impression was that it's not simple.

What is "it" in the last sentence?  IOW, what is not simple about that
with Emacs?

It is true that the Unicode related data is produced at build time,
but only some of that is actually recorded in the Emacs binary, the
rest is loaded upon demand.  But all the data is stored in data
structures that are mutable, given some Lisp programming.

(It is not clear to me which part of the Unicode data you would like
to change; are you talking about adding characters to the list of
those defined by Unicode?  If you are using the PUA codepoints, it's
possible that you will need to update Emacs's notion of PUA as well.)