GNU bug report logs - #47856
auto-fill-mode vs. oriental languages: no respect

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From: Eli Zaretskii <eliz <at> gnu.org>
To: jidanni <at> jidanni.org
Cc: 47856 <at> debbugs.gnu.org
Subject: bug#47856: auto-fill-mode vs. oriental languages: no respect
Date: Tue, 20 Apr 2021 14:24:45 +0300

> From: Eli Zaretskii <eliz <at> gnu.org>
> Date: Tue, 20 Apr 2021 01:20:02 -0400
> Cc: 47856 <at> debbugs.gnu.org
> 
> Please help me understand the issue by answering those questions,
> and please provide any additional information that could be of
> relevance, so that we could make some progress here.  TIA.

Never mind, I've managed to figure this out on my own.  So, back to
the TIL department:

 . For CJK scripts, Emacs's filling commands are allowed to break a
   line at _any_ character, not just at whitespace.  This is not just
   Emacs's invention: the Unicode Line-Breaking Algorithm mandates the
   same, albeit via special properties it assigns to CJK characters.

 . If you load 'kinsoku', Emacs will additionally refrain from
   breaking lines between some CJK characters, where there are special
   rules which prohibit that.  But still, line can be broken almost at
   any place in CJK text, even under the kinsoku rules.

 . Conclusion: this is the intended behavior, a feature.

So yeah, it's a documentation issue, to be fixed soon enough.

> "Well browsers will break your oriental lines arbitrarily anyway. Bug closed."
> 
> Yes, but they do that a the ends of lines they render.

If this is what you want, it's a different feature: you need to turn
on word-wrap (M-x visual-line-mode RET), not auto-fill.  In Emacs 28,
there will be an additional option, word-wrap-by-category, which will
obey kinsoku rules in visual-line-mode.

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