bug#66970: 29.1; Overwrite-mode is not working with Korean characters

[Eli Zaretskii <eliz@gnu.org>]

tags 66970 moreinfo
thanks

> Date: Tue, 7 Nov 2023 01:07:00 +0900
> From: SUKBEOM KIM <sukbeom.kim@gmail.com>
> 
> I found a bug with typing Korean characters that "overwrite-mode" is not
> actually working well. (For Japanese/Chinese characters, there is no
> issue at all.)
> 
> aeoiu
> => あえu
> => 아에aeiou

Please provide a full recipe, starting from "emacs -Q", including from
what text to start and which characters to type.  I'm not sure I
understand the situation in enough detail to investigate.

> In the thread, one of the Japanese users reported a bug but it is not
> appropriate for Korean characters which requires a combination of
> sub-characters to make a character unlike other Japanese or Chinese
> characters.

To investigate, we need to see an example of characters that are
composed in the Korean case, and then are overwritten.  AFAIU, the
text you show above doesn't include character composition.

Emacs 29 also has the new variable composition-break-at-point, which
perhaps could be useful in at least some use cases of overwriting
Korean text (and any other text where characters are composed).

Thanks.