Re: scratch/tzz/auth-source-reveal-mode f16a4c8 2/3: Support regular expressions and API for prettify-symbols-mode

[Stefan Monnier]

> +For example: \"abc[123]\" matching \"abc1\", \"abc2\", or
> +\"abc3\" could be mapped to the Unicode WORLD MAP. Note again the
> +IDENTIFIER is an arbitrary Lisp symbol.
> + (my-worldmap \"abc[123]\" 128506)

I think using ?\U0001f5fa might be "natural" for a unicode char.

More importantly, I think we should accommodate cases where the regexp
needs to match some of the context, i.e. where only some submatch needs
to be prettified.
E.g. we could say that the text affected is either submatch 1 or
submatch 0 (where submatch 0 is used if there's (match-end 1) is nil).


        Stefan