bug#44020: 28.0.50; Prefer selection of colour emoji fonts?

[Eli Zaretskii <eliz@gnu.org>]

> From: Robert Pluim <rpluim@gmail.com>
> Cc: Lars Ingebrigtsen <larsi@gnus.org>,  44020@debbugs.gnu.org
> Date: Fri, 16 Oct 2020 10:19:12 +0200
> 
> 1. Deciding what fonts we should use for emoji. We can get a lot of
>    good results by adding appropriate 'set-fontset-font' calls to
>    emacs, independently of any other work (I also wonder if we should
>    change the default of use-default-font-for-symbols, given the
>    proliferation of both emoji and fonts dedicated to displaying them)
> 
> 2. Extract the emoji sequences from the Unicode data files and assign
>    them to a new 'emoji' script. Be prepared to choose your favourite
>    bikeshed colour.
> 
> 3. Add the appropriate entries to composition-function-table so that
>    the various multi-codepoint emoji sequences have a chance to be
>    rendered correctly, whether by HarfBuzz or the Apple thing whose
>    name I forget.
> 
> For [1], I think "Noto Color Emoji" and "Apple Color Emoji" would be a
> good start.

I agree, but [1] depends on [2], because set-fontset-font needs to
know the script.

Also, Noto Color Emoji has a free license, so it's okay for it to be
in fontset.el, but it is not clear to me whether Apple Color Emoji is
distributed under a free license.

> For [2], I think that was finished, except that Eli then updated Emacs
> to the next version of Unicode, and I haven't adjusted yet.

"Finished", in the sense that it is in Emacs already?

> Iʼll see if I can clean this up this weekend and throw it on a branch.

Thanks.

FWIW, I think this is good enough to land on master directly, I see no
need for a feature branch.