Re: emacs-27 60c84ad: ; * etc/TODO: Fix last change.

[Eli Zaretskii]

> From: Robert Pluim <address@hidden>
> Cc: address@hidden
> Date: Mon, 02 Mar 2020 16:06:17 +0100
> 
> Or we could take a leaf out of FE0F's book, and just do:
> 
>  "\N{U+1F3C3}...?\N{U+FE0F}"
> 
> but I thought that since this runs inside redisplay, we should strive
> to make the patterns as specific as possible.

Not sure if it's better to have several rules rather than one which
used regexp conditionals.  The code in composite.c iterates through
the rules one by one, each time calling the regex search, whereas a
single regexp will be compiled once, then matched, and regex-emacs.c
is quite optimized.  So it might be best to have something like (for
the sequences you show)

  \U001f3c3[\U001f3fb-\U001f3ff]?\u200d[\u2640\u2642]\ufe0f

We use such regexps a lot in composition rules elsewhere.