Re: search-default-mode char-fold-to-regexp and Greek Extended block characters

[Eli Zaretskii]

> From: Robert Pluim <address@hidden>
> Cc: address@hidden
> Date: Fri, 19 Jul 2019 18:03:05 +0200
> 
>     >> 1. ί (\u03af GREEK SMALL LETTER IOTA WITH TONOS)
>     >> 2. ί (\u1f77 GREEK SMALL LETTER IOTA WITH OXIA)
>     >> 
>     >> I do C-s C-x 8 RET 03b9
>     >> 
>     >> isearch will find the iota with tonos, but not the iota with oxia,
>     >> even though the decomposition of the decomposition of the latter
>     >> contains iota. Is that expected?
> 
>     Eli> I suggest to step through the loop in char-fold.el and see what
>     Eli> happens there for ί.
> 
> After poking around, the char-fold-table entry for \u1f77 contains
> \u1f77 and \u03af, but not \u03b9, so this is expected. I then started
> looking into the further details of unicode decomposition and
> normalization, and decided that I definitely donʼt know enough about
> this to decide if this is a bug or not :-)

  (get-char-code-property ?ί 'decomposition) => (943) ; (#x03af) i.e (?ί)
  (get-char-code-property ?ί 'decomposition) => (953 769) ; (#x03b9 #x0301)

Do we expand the decomposition property recursively?  It sounds like
we don't, but maybe we should.