Commit 2a886892 authored by Eli Zaretskii's avatar Eli Zaretskii
Browse files

Document the way Emacs prompts for a safe coding system when the

buffer is saved.
parent db7a3ede
...@@ -636,6 +636,34 @@ a different coding system, you can specify a different coding system for ...@@ -636,6 +636,34 @@ a different coding system, you can specify a different coding system for
the buffer using @code{set-buffer-file-coding-system} (@pxref{Specify the buffer using @code{set-buffer-file-coding-system} (@pxref{Specify
Coding}). Coding}).
While editing a file, you will sometimes insert characters which
cannot be encoded with the coding system stored in
@code{buffer-file-coding-system}. For example, suppose you start with
an ASCII file and insert a few Latin-1 characters into it. Or you could
edit a text file in Polish encoded in @code{iso-8859-2} and add to it
translations of several Polish words into Russian. When you save the
buffer, Emacs can no longer use the previous value of the buffer's
coding system, because the characters you added cannot be encoded by
that coding system.
When that happens, Emacs tries the most-preferred coding system (set
by @kbd{M-x prefer-coding-system} or @kbd{M-x
set-language-environment}), and if that coding system can safely encode
all of the characters in the buffer, Emacs uses it, and stores its value
in @code{buffer-file-coding-system}. Otherwise, Emacs pops up a window
with a list of coding systems suitable for encoding the buffer, and
prompts you to choose one of those coding systems.
If you insert characters which cannot be encoded by the buffer's
coding system while editing a mail message, Emacs behaves a bit
differently. It additionally checks whether the most-preferred coding
system is recommended for use in MIME messages; if it isn't, Emacs tells
you that the most-preferred coding system is not recommended and prompts
you for another coding system. This is so you won't inadvertently send
a message encoded in a way that your recipient's mail software will have
difficulty decoding. (If you do want to use the most-preferred coding
system, you can type its name to Emacs prompt anyway.)
@vindex sendmail-coding-system @vindex sendmail-coding-system
When you send a message with Mail mode (@pxref{Sending Mail}), Emacs has When you send a message with Mail mode (@pxref{Sending Mail}), Emacs has
four different ways to determine the coding system to use for encoding four different ways to determine the coding system to use for encoding
......
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