(Charset Translation): Fix description of process.

man/emacs-mime.texi

@@ -18,7 +18,7 @@
 
 This file documents the Emacs MIME interface functionality.
 
-Copyright (C) 1998,99,2000 Free Software Foundation, Inc.
+Copyright (C) 1998,99,2000, 2002 Free Software Foundation, Inc.
 
 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.1 or
@@ -47,7 +47,7 @@ license to the document, as described in section 6 of the license.
 @page
 
 @vskip 0pt plus 1filll
-Copyright @copyright{} 1998,99,2000 Free Software Foundation, Inc.
+Copyright @copyright{} 1998,99,2000, 2002 Free Software Foundation, Inc.
 
 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.1 or
@@ -1264,7 +1264,9 @@ has been composed inside Emacs, an appropriate @sc{mime} charset has to
 be chosen.
 
 @vindex mail-parse-charset
-If you are running a non-Mule Emacs, this process is simple: if the part
+@cindex unibyte Emacs
+If you are running a non-Mule XEmacs, or Emacs in unibyte
+mode@footnote{Deprecated!}, this process is simple: if the part
 contains any non-@sc{ascii} (8-bit) characters, the @sc{mime} charset
 given by @code{mail-parse-charset} (a symbol) is used.  (Never set this
 variable directly, though.  If you want to change the default charset,
@@ -1274,23 +1276,31 @@ Variables, message, Message Manual}, for example.)  If there are only
 @sc{ascii} characters, the @sc{mime} charset @samp{US-ASCII} is used, of
 course.
 
-@cindex Mule
-@cindex UTF-8
-@cindex Unicode
+@cindex multibyte Emacs
+@cindex @code{mime-charset} property
+In a normal (multibyte) Emacs session, a list of coding systems is
+derived that can encode the message part's content and correspond to
+MIME charsets (according to their @code{mime-charset} property).  This
+list is according to the normal priority rules and the highest priority
+one is chosen to encode the part.  If no such coding system can encode
+the part's contents, they are split into several parts such that each
+can be encoded with an appropriate coding system/@sc{mime}
+charset.@footnote{The part can only be split at line boundaries,
+though---if more than one @sc{mime} charset is required to encode a
+single line, it is not possible to encode the part.}  Note that this
+procedure works with any correctly-defined coding systems, not just
+built-in ones.  Given a suitably-defined UTF-8 coding system---one
+capable of encoding the Emacs charsets you use---it is not normally
+necessary to split a part by charset.
+
 @vindex mm-mime-mule-charset-alist
-Things are slightly more complicated when running Emacs with Mule
-support.  In this case, a list of the Mule charsets used in the part is
-obtained, and the corresponding @sc{mime} charsets are determined.  If
-this results in a single @sc{mime} charset, this is used to encode the
-part.  But if the resulting list of @sc{mime} charsets contains more
-than one element, two things can happen: if it is possible to encode the
-part via UTF-8, this charset is used.  (For this, Emacs must support the
-@code{utf-8} coding system, and the part must consist entirely of
-characters which have Unicode counterparts.)  If UTF-8 is not available,
-the part is split into several, so that each one can be encoded with a
-single @sc{mime} charset.  The part can only be split at line
-boundaries, though---if more than one @sc{mime} charset is required to
-encode a single line, it is not possible to encode the part.
+@cindex XEmacs/Mule
+It isn't possible to do this properly in XEmacs/Mule.  Instead, a list
+of the Mule charsets used in the part is obtained, and the
+corresponding @sc{mime} charsets are determined by lookup in
+@code{mm-mime-mule-charset-alist}.  If the list elements all
+correspond to a single @sc{mime} charset, that is used to encode the
+part.  Otherwise, the part is split as above.
 
 @node Conversion
 @section Conversion