Re: What does `undecided' do for encoding text?

[Eli Zaretskii]

> From: Kenichi Handa <address@hidden>
> CC: address@hidden
> Date: Tue, 10 Feb 2009 20:16:53 +0900
> 
> > This may have nothing to do with what the programmer did.  My use case
> > was in Rmail: if the original message had non-ASCII text encoded with
> > QP or B64, Rmail would (correctly) return `undecided' when it detects
> > the message encoding.  Suppose you then edit the message and add
> > non-ASCII characters as raw bytes, e.g. by base64-decode-region, and
> > type "C-c C-c".  rmail-cease-edit now needs to encode the text and put
> > it back into the mbox buffer, and the immediate choice it has for the
> > pertinent coding-system is to use buffer-file-coding-system of the
> > buffer where the message was edited.  But the value of
> > buffer-file-coding-system in that buffer is `undecided'...
> 
> The situation is the same as visiting an ASCII only file,
> entering some non-ASCII characters, and saving it.  In that
> case, we use selecte-safe-coding-system to decide the coding
> system to encode the buffer contents.

I think that's a different situation: base64-decode-region inserts raw
bytes, not non-ASCII characters.  So select-safe-coding-system may not
work correctly, because (AFAIK) it was not designed for that case.