bug#27872: 26.0.50; freeze when opening file with emojis

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 30 Jul 2017 23:07:44 +0100
> From: Alan Third <alan@idiocy.org>
> Cc: Eli Zaretskii <eliz@gnu.org>, 27872@debbugs.gnu.org
> 
> My understanding is that if you have Symbola installed it’s one of the
> first fonts Emacs checks for emoji. If you don’t have it installed, or
> Emacs can’t find the glyph it’s looking for, then it searches other
> fonts for them.

That's right.

> I think that means you’ve probably got a font that doesn’t get on well
> with Emacs. We should be able to find out which one if you’re willing
> to try building a custom version which prints out each font family as
> it tries them.

I think it means that the freeze wasn't a freeze, but just a very long
search for a font that could support the character.  It was made even
longer by using up a lot of memory, which caused paging and slowed
Emacs down.  Not sure why it used up so much memory, perhaps that's
due to some very large font, or maybe it's a bug in the macOS code
which is involved in the search.

Having Symbola installed is a Good Thing anyway, because Emacs by
default will try to use it for many unusual characters.