-\input texinfo @c -*-texinfo-*-
+\input texinfo
-@setfilename message
+@setfilename emacs-mime
@settitle Emacs MIME Manual
@synindex fn cp
@synindex vr cp
@synindex pg cp
-@c @direntry
-@c * Emacs Mime: (emacs-mime). The MIME de/composition library.
-@c @end direntry
+@dircategory Emacs
+@direntry
+* Emacs MIME: (emacs-mime). The MIME de/composition library.
+@end direntry
@iftex
@finalout
@end iftex
@setchapternewpage odd
-@ifinfo
+@ifnottex
This file documents the Emacs MIME interface functionality.
-Copyright (C) 1996 Free Software Foundation, Inc.
+Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
-Permission is granted to make and distribute verbatim copies of
-this manual provided the copyright notice and this permission notice
-are preserved on all copies.
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.1 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, with the Front-Cover texts being ``A GNU
+Manual'', and with the Back-Cover Texts as in (a) below. A copy of the
+license is included in the section entitled ``GNU Free Documentation
+License'' in the Emacs manual.
-@ignore
-Permission is granted to process this file through Tex and print the
-results, provided the printed document carries copying permission
-notice identical to this one except for the removal of this paragraph
-(this paragraph not being relevant to the printed manual).
+(a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
+this GNU Manual, like GNU software. Copies published by the Free
+Software Foundation raise funds for GNU development.''
-@end ignore
-Permission is granted to copy and distribute modified versions of this
-manual under the conditions for verbatim copying, provided also that the
-entire resulting derived work is distributed under the terms of a
-permission notice identical to this one.
-
-Permission is granted to copy and distribute translations of this manual
-into another language, under the above conditions for modified versions.
-@end ifinfo
+This document is part of a collection distributed under the GNU Free
+Documentation License. If you want to distribute this document
+separately from the collection, you can do so by adding a copy of the
+license to the document, as described in section 6 of the license.
+@end ifnottex
@tex
@page
@vskip 0pt plus 1filll
-Copyright @copyright{} 1998 Free Software Foundation, Inc.
-
-Permission is granted to make and distribute verbatim copies of
-this manual provided the copyright notice and this permission notice
-are preserved on all copies.
-
-Permission is granted to copy and distribute modified versions of this
-manual under the conditions for verbatim copying, provided that the
-entire resulting derived work is distributed under the terms of a
-permission notice identical to this one.
-
-Permission is granted to copy and distribute translations of this manual
-into another language, under the above conditions for modified versions.
-
+Copyright @copyright{} 1998, 1999, 2000 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
+any later version published by the Free Software Foundation; with the
+Invariant Sections being none, with the Front-Cover texts being ``A GNU
+Manual'', and with the Back-Cover Texts as in (a) below. A copy of the
+license is included in the section entitled ``GNU Free Documentation
+License'' in the Emacs manual.
+
+(a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
+this GNU Manual, like GNU software. Copies published by the Free
+Software Foundation raise funds for GNU development.''
+
+This document is part of a collection distributed under the GNU Free
+Documentation License. If you want to distribute this document
+separately from the collection, you can do so by adding a copy of the
+license to the document, as described in section 6 of the license.
@end titlepage
@page
@end tex
@node Top
-@top Emacs Mime
+@top Emacs MIME
This manual documents the libraries used to compose and display
@sc{mime} messages.
read at least RFC2045 and RFC2047.
@menu
+* Interface Functions:: An abstraction over the basic functions.
* Basic Functions:: Utility and basic parsing functions.
* Decoding and Viewing:: A framework for decoding and viewing.
+* Composing:: MML; a language for describing MIME parts.
+* Standards:: A summary of RFCs and working documents used.
* Index:: Function and variable index.
@end menu
-@node Basic Functions
-@chapter Basic Functions
-
-This chapter describes the basic, ground-level functions for parsing and
-handling. Covered here is parsing @code{From} lines, removing comments
-from header lines, decoding encoded words, parsing date headers and so
-on. High-level functionality is dealt with in the @pxref{Decoding and
-Viewing} chapter.
-
-@menu
-* mail-parse:: The generalized @sc{mime} and mail interface.
-* rfc2231:: Parsing @code{Content-Type} headers.
-* drums:: Handling mail headers defined by RFC822bis.
-* rfc2047:: En/decoding encoded words in headers.
-* time-date:: Functions for parsing dates and manipulating time.
-* qp:: Quoted-Printable en/decoding.
-* base64:: Base64 en/decoding.
-@end menu
-
-
-@node mail-parse
-@section mail-parse
+@node Interface Functions
+@chapter Interface Functions
+@cindex interface functions
+@cindex mail-parse
-It is perhaps misleading to place the @code{mail-parse} library in this
-chapter. It is not a basic low-level library---rather, it is an
-abstraction over the actual low-level libraries that are described in the
-subsequent sections.
+The @code{mail-parse} library is an abstraction over the actual
+low-level libraries that are described in the next chapter.
Standards change, and so programs have to change to fit in the new
mold. For instance, RFC2045 describes a syntax for the
@example
(mail-header-parse-content-type
"image/gif; name=\"b980912.gif\"")
-
-=> ("image/gif" (name . "b980912.gif"))
+@result{} ("image/gif" (name . "b980912.gif"))
@end example
@item mail-header-parse-content-disposition
@example
(mail-content-type-get
'("image/gif" (name . "b980912.gif")) 'name)
-
-=> "b980912.gif"
+@result{} "b980912.gif"
@end example
+@item mail-header-encode-parameter
+@findex mail-header-encode-parameter
+Takes a parameter string and returns an encoded version of the string.
+This is used for parameters in headers like @code{Content-Type} and
+@code{Content-Disposition}.
+
@item mail-header-remove-comments
@findex mail-header-remove-comments
Return a comment-free version of a header.
@example
(mail-header-remove-comments
"Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
-
-=> "Gnus/5.070027 "
+@result{} "Gnus/5.070027 "
@end example
@item mail-header-remove-whitespace
@example
(mail-header-remove-whitespace
"image/gif; name=\"Name with spaces\"")
-=> "image/gif;name=\"Name with spaces\""
+@result{} "image/gif;name=\"Name with spaces\""
@end example
@item mail-header-get-comment
Return the last comment in a header.
@example
-(mail-header-get-comment
+(mail-header-get-comment
"Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
-=> "Finnish Landrace"
+@result{} "Finnish Landrace"
@end example
@item mail-header-parse-address
@example
(mail-header-parse-address
"Hrvoje Niksic <hniksic@@srce.hr>")
-=> ("hniksic@@srce.hr" . "Hrvoje Niksic")
+@result{} ("hniksic@@srce.hr" . "Hrvoje Niksic")
@end example
@item mail-header-parse-addresses
@example
(mail-header-parse-addresses
"Hrvoje Niksic <hniksic@@srce.hr>, Steinar Bang <sb@@metis.no>")
- => (("hniksic@@srce.hr" . "Hrvoje Niksic")
+@result{} (("hniksic@@srce.hr" . "Hrvoje Niksic")
("sb@@metis.no" . "Steinar Bang"))
@end example
@item mail-header-narrow-to-field
@findex mail-header-narrow-to-field
-Narrow the buffer to the header under point.
+Narrow the buffer to the header under point. Understands continuation
+headers.
+
+@item mail-header-fold-field
+@findex mail-header-fold-field
+Fold the header under point.
+
+@item mail-header-unfold-field
+@findex mail-header-unfold-field
+Unfold the header under point.
+
+@item mail-header-field-value
+@findex mail-header-field-value
+Return the value of the field under point.
@item mail-encode-encoded-word-region
@findex mail-encode-encoded-word-region
@example
(mail-encode-encoded-word-string
"This is naïve, baby")
-=> "This is =?iso-8859-1?q?na=EFve,?= baby"
+@result{} "This is =?iso-8859-1?q?na=EFve,?= baby"
@end example
@item mail-decode-encoded-word-region
@example
(mail-decode-encoded-word-string
"This is =?iso-8859-1?q?na=EFve,?= baby")
-=> "This is naïve, baby"
+@result{} "This is naïve, baby"
@end example
@end table
-Currently, @code{mail-parse} is an abstraction over @code{drums},
-@code{rfc2047} and @code{rfc2231}. These are documented in the
-subsequent sections.
+Currently, @code{mail-parse} is an abstraction over @code{ietf-drums},
+@code{rfc2047}, @code{rfc2045} and @code{rfc2231}. These are documented
+in the subsequent sections.
+
+
+
+@node Basic Functions
+@chapter Basic Functions
+
+This chapter describes the basic, ground-level functions for parsing and
+handling. Covered here is parsing @code{From} lines, removing comments
+from header lines, decoding encoded words, parsing date headers and so
+on. High-level functionality is dealt with in the next chapter
+(@pxref{Decoding and Viewing}).
+
+@menu
+* rfc2045:: Encoding @code{Content-Type} headers.
+* rfc2231:: Parsing @code{Content-Type} headers.
+* ietf-drums:: Handling mail headers defined by RFC822bis.
+* rfc2047:: En/decoding encoded words in headers.
+* time-date:: Functions for parsing dates and manipulating time.
+* qp:: Quoted-Printable en/decoding.
+* base64:: Base64 en/decoding.
+* binhex:: Binhex decoding.
+* uudecode:: Uuencode decoding.
+* rfc1843:: Decoding HZ-encoded text.
+* mailcap:: How parts are displayed is specified by the @file{.mailcap} file
+@end menu
+
+
+@node rfc2045
+@section rfc2045
+
+RFC2045 is the ``main'' @sc{mime} document, and as such, one would
+imagine that there would be a lot to implement. But there isn't, since
+most of the implementation details are delegated to the subsequent
+RFCs.
+
+So @file{rfc2045.el} has only a single function:
+
+@table @code
+@item rfc2045-encode-string
+@findex rfc2045-encode-string
+Takes a parameter and a value and returns a @samp{PARAM=VALUE} string.
+@var{value} will be quoted if there are non-safe characters in it.
+@end table
@node rfc2231
@example
(rfc2231-parse-string
- "application/x-stuff;
+ "application/x-stuff;
title*0*=us-ascii'en'This%20is%20even%20more%20;
title*1*=%2A%2A%2Afun%2A%2A%2A%20;
title*2=\"isn't it!\"")
-=> ("application/x-stuff"
+@result{} ("application/x-stuff"
(title . "This is even more ***fun*** isn't it!"))
@end example
@item rfc2231-get-value
@findex rfc2231-get-value
-Takes one of the lists on the format above and return
+Takes one of the lists on the format above and returns
the value of the specified attribute.
+@item rfc2231-encode-string
+@findex rfc2231-encode-string
+Encode a parameter in headers likes @code{Content-Type} and
+@code{Content-Disposition}.
+
@end table
-@node drums
-@section drums
+@node ietf-drums
+@section ietf-drums
@dfn{drums} is an IETF working group that is working on the replacement
for RFC822.
The functions provided by this library include:
@table @code
-@item drums-remove-comments
-@findex drums-remove-comments
+@item ietf-drums-remove-comments
+@findex ietf-drums-remove-comments
Remove the comments from the argument and return the results.
-@item drums-remove-whitespace
-@findex drums-remove-whitespace
+@item ietf-drums-remove-whitespace
+@findex ietf-drums-remove-whitespace
Remove linear white space from the string and return the results.
Spaces inside quoted strings and comments are left untouched.
-@item drums-get-comment
-@findex drums-get-comment
+@item ietf-drums-get-comment
+@findex ietf-drums-get-comment
Return the last most comment from the string.
-@item drums-parse-address
-@findex drums-parse-address
+@item ietf-drums-parse-address
+@findex ietf-drums-parse-address
Parse an address string and return a list that contains the mailbox and
the plain text name.
-@item drums-parse-addresses
-@findex drums-parse-addresses
+@item ietf-drums-parse-addresses
+@findex ietf-drums-parse-addresses
Parse a string that contains any number of comma-separated addresses and
return a list that contains mailbox/plain text pairs.
-@item drums-parse-date
-@findex drums-parse-date
+@item ietf-drums-parse-date
+@findex ietf-drums-parse-date
Parse a date string and return an Emacs time structure.
-@item drums-narrow-to-header
-@findex drums-narrow-to-header
+@item ietf-drums-narrow-to-header
+@findex ietf-drums-narrow-to-header
Narrow the buffer to the header section of the current buffer.
@end table
The @code{Q} encoding isn't quite the same for all headers. Some
headers allow a narrower range of characters, and that is what this
variable is for. It's an alist of header regexps / allowable character
-ranges.
+ranges.
@item rfc2047-encoded-word-regexp
@vindex rfc2047-encoded-word-regexp
-When decoding words, this library looks for matches to this regexp.
+When decoding words, this library looks for matches to this regexp.
@end table
and manipulating time. (Not by using tesseracts, though, I'm sorry to
say.)
-These functions converts between five formats: A date string, an Emacs
+These functions convert between five formats: A date string, an Emacs
time structure, a decoded time list, a second number, and a day number.
-The functions have quite self-explanatory names, so the following just
-gives an overview of which functions are available.
+Here's a bunch of time/date/second/day examples:
@example
(parse-time-string "Sat Sep 12 12:21:54 1998 +0200")
-=> (54 21 12 12 9 1998 6 nil 7200)
+@result{} (54 21 12 12 9 1998 6 nil 7200)
(date-to-time "Sat Sep 12 12:21:54 1998 +0200")
-=> (13818 19266)
+@result{} (13818 19266)
(time-to-seconds '(13818 19266))
-=> 905595714.0
+@result{} 905595714.0
(seconds-to-time 905595714.0)
-=> (13818 19266 0)
+@result{} (13818 19266 0)
-(time-to-day '(13818 19266))
-=> 729644
+(time-to-days '(13818 19266))
+@result{} 729644
(days-to-time 729644)
-=> (961933 65536)
+@result{} (961933 65536)
(time-since '(13818 19266))
-=> (0 430)
+@result{} (0 430)
(time-less-p '(13818 19266) '(13818 19145))
-=> nil
+@result{} nil
(subtract-time '(13818 19266) '(13818 19145))
-=> (0 121)
+@result{} (0 121)
(days-between "Sat Sep 12 12:21:54 1998 +0200"
"Sat Sep 07 12:21:54 1998 +0200")
-=> 5
+@result{} 5
(date-leap-year-p 2000)
-=> t
+@result{} t
(time-to-day-in-year '(13818 19266))
-=> 255
+@result{} 255
+(time-to-number-of-days
+ (time-since
+ (date-to-time "Mon, 01 Jan 2001 02:22:26 GMT")))
+@result{} 4.146122685185185
@end example
And finally, we have @code{safe-date-to-time}, which does the same as
@code{date-to-time}, but returns a zero time if the date is
syntactically malformed.
+The five data representations used are the following:
+
+@table @var
+@item date
+An RFC822 (or similar) date string. For instance: @code{"Sat Sep 12
+12:21:54 1998 +0200"}.
+
+@item time
+An internal Emacs time. For instance: @code{(13818 26466)}.
+
+@item seconds
+A floating point representation of the internal Emacs time. For
+instance: @code{905595714.0}.
+
+@item days
+An integer number representing the number of days since 00000101. For
+instance: @code{729644}.
+
+@item decoded time
+A list of decoded time. For instance: @code{(54 21 12 12 9 1998 6 t
+7200)}.
+@end table
+
+All the examples above represent the same moment.
+
+These are the functions available:
+
+@table @code
+@item date-to-time
+Take a date and return a time.
+
+@item time-to-seconds
+Take a time and return seconds.
+
+@item seconds-to-time
+Take seconds and return a time.
+
+@item time-to-days
+Take a time and return days.
+
+@item days-to-time
+Take days and return a time.
+
+@item date-to-day
+Take a date and return days.
+
+@item time-to-number-of-days
+Take a time and return the number of days that represents.
+
+@item safe-date-to-time
+Take a date and return a time. If the date is not syntactically valid,
+return a "zero" date.
+
+@item time-less-p
+Take two times and say whether the first time is less (i. e., earlier)
+than the second time.
+
+@item time-since
+Take a time and return a time saying how long it was since that time.
+
+@item subtract-time
+Take two times and subtract the second from the first. I. e., return
+the time between the two times.
+
+@item days-between
+Take two days and return the number of days between those two days.
+
+@item date-leap-year-p
+Take a year number and say whether it's a leap year.
+
+@item time-to-day-in-year
+Take a time and return the day number within the year that the time is
+in.
+
+@end table
@node qp
@node base64
@section base64
+@cindex base64
Base64 is an encoding that encodes three bytes into four characters,
thereby increasing the size by about 33%. The alphabet used for
@end table
+@node binhex
+@section binhex
+@cindex binhex
+@cindex Apple
+@cindex Macintosh
+
+@code{binhex} is an encoding that originated in Macintosh environments.
+The following function is supplied to deal with these:
+
+@table @code
+@item binhex-decode-region
+@findex binhex-decode-region
+Decode the encoded text in the region. If given a third parameter, only
+decode the @code{binhex} header and return the filename.
+
+@end table
+
+
+@node uudecode
+@section uudecode
+@cindex uuencode
+@cindex uudecode
+
+@code{uuencode} is probably still the most popular encoding of binaries
+used on Usenet, although @code{base64} rules the mail world.
+
+The following function is supplied by this package:
+
+@table @code
+@item uudecode-decode-region
+@findex uudecode-decode-region
+Decode the text in the region.
+@end table
+
+
+@node rfc1843
+@section rfc1843
+@cindex rfc1843
+@cindex HZ
+@cindex Chinese
+
+RFC1843 deals with mixing Chinese and ASCII characters in messages. In
+essence, RFC1843 switches between ASCII and Chinese by doing this:
+
+@example
+This sentence is in ASCII.
+The next sentence is in GB.~@{<:Ky2;S@{#,NpJ)l6HK!#~@}Bye.
+@end example
+
+Simple enough, and widely used in China.
+
+The following functions are available to handle this encoding:
+
+@table @code
+@item rfc1843-decode-region
+Decode HZ-encoded text in the region.
+
+@item rfc1843-decode-string
+Decode a HZ-encoded string and return the result.
+
+@end table
+
+
+@node mailcap
+@section mailcap
+
+The @file{~/.mailcap} file is parsed by most @sc{mime}-aware message
+handlers and describes how elements are supposed to be displayed.
+Here's an example file:
+
+@example
+image/*; gimp -8 %s
+audio/wav; wavplayer %s
+@end example
+
+This says that all image files should be displayed with @code{gimp}, and
+that WAVE audio files should be played by @code{wavplayer}.
+
+The @code{mailcap} library parses this file, and provides functions for
+matching types.
+
+@table @code
+@item mailcap-mime-data
+@vindex mailcap-mime-data
+This variable is an alist of alists containing backup viewing rules.
+
+@end table
+
+Interface functions:
+
+@table @code
+@item mailcap-parse-mailcaps
+@findex mailcap-parse-mailcaps
+Parse the @code{~/.mailcap} file.
+
+@item mailcap-mime-info
+Takes a @sc{mime} type as its argument and returns the matching viewer.
+
+@end table
+
+
+
@node Decoding and Viewing
@chapter Decoding and Viewing
The main idea is to first analyze a @sc{mime} article, and then allow
other programs to do things based on the list of @dfn{handles} that are
-returned as a result of this analyze.
+returned as a result of this analysis.
@menu
-* Dissection:: Analyzing a @sc{mime} message.
-* Handles:: Handle manipulations.
-* Display:: Displaying handles.
+* Dissection:: Analyzing a @sc{mime} message.
+* Non-MIME:: Analyzing a non-@sc{mime} message.
+* Handles:: Handle manipulations.
+* Display:: Displaying handles.
+* Customization:: Variables that affect display.
+* New Viewers:: How to write your own viewers.
@end menu
descend the message, following the structure, and return a tree of
@sc{mime} handles that describes the structure of the message.
+@node Non-MIME
+@section Non-MIME
+
+Gnus also understands some non-MIME attachments, such as postscript,
+uuencode, binhex, shar, forward, gnatsweb, pgp. Each of these features
+can be disabled by add an item into @code{mm-uu-configure-list}.
+For example,
+
+@lisp
+(require 'mm-uu)
+(add-to-list 'mm-uu-configure-list '(pgp-signed . disabled))
+@end lisp
+
+@table @code
+@item postscript
+@findex postscript
+Postscript file.
+
+@item uu
+@findex uu
+Uuencoded file.
+
+@item binhex
+@findex binhex
+Binhex encoded file.
+
+@item shar
+@findex shar
+Shar archive file.
+
+@item forward
+@findex forward
+Non-@sc{mime} forwarded message.
+
+@item gnatsweb
+@findex gnatsweb
+Gnatsweb attachment.
+
+@item pgp-signed
+@findex pgp-signed
+PGP signed clear text.
+
+@item pgp-encrypted
+@findex pgp-encrypted
+PGP encrypted clear text.
+
+@item pgp-key
+@findex pgp-key
+PGP public keys.
+
+@item emacs-sources
+@findex emacs-sources
+Emacs source code. This item works only in the groups matching
+@code{mm-uu-emacs-sources-regexp}.
+
+@end table
@node Handles
@section Handles
@findex mm-handle-disposition
Return the description of the part.
+@item mm-get-content-id
+Returns the handle(s) referred to by @code{Content-ID}.
+
@end table
Prompt for a mailcap method to use to view the part.
@end table
-
+
+
+@node Customization
+@section Customization
+
+@table @code
+
+@item mm-inline-text-html-renderer
+@findex mm-inline-text-html-render-with-w3
+@findex mm-inline-text-html-render-with-w3m
+This function will be used to convert the HTML to the text. There are
+two pre-defined functions: @code{mm-inline-text-html-render-with-w3},
+which uses Emacs/w3; and @code{mm-inline-text-html-render-with-w3m},
+which uses emacs-w3m (see @uref{http://emacs-w3m.namazu.org/} for more
+information about emacs-w3m). The function will be called with a MIME
+handle as the argument.
+
+@item mm-inline-text-html-with-images
+Some HTML mails might have the trick of spammers using @samp{<img>} tags.
+It is likely to be intended to verify whether you have read the mail.
+You can prevent your personal informations from leaking by setting this
+option to @code{nil} (which is the default). It is currently ignored by
+Emacs/w3. For emacs-w3m, you may use the command @kbd{t} on the image
+anchor to show an image even if it is @code{nil}.
+
+@item mm-inline-media-tests
+This is an alist where the key is a @sc{mime} type, the second element
+is a function to display the part @dfn{inline} (i.e., inside Emacs), and
+the third element is a form to be @code{eval}ed to say whether the part
+can be displayed inline.
+
+This variable specifies whether a part @emph{can} be displayed inline,
+and, if so, how to do it. It does not say whether parts are
+@emph{actually} displayed inline.
+
+@item mm-inlined-types
+This, on the other hand, says what types are to be displayed inline, if
+they satisfy the conditions set by the variable above. It's a list of
+@sc{mime} media types.
+
+@item mm-automatic-display
+This is a list of types that are to be displayed ``automatically'', but
+only if the above variable allows it. That is, only inlinable parts can
+be displayed automatically.
+
+@item mm-attachment-override-types
+Some @sc{mime} agents create parts that have a content-disposition of
+@samp{attachment}. This variable allows overriding that disposition and
+displaying the part inline. (Note that the disposition is only
+overridden if we are able to, and want to, display the part inline.)
+
+@item mm-discouraged-alternatives
+List of @sc{mime} types that are discouraged when viewing
+@samp{multipart/alternative}. Viewing agents are supposed to view the
+last possible part of a message, as that is supposed to be the richest.
+However, users may prefer other types instead, and this list says what
+types are most unwanted. If, for instance, @samp{text/html} parts are
+very unwanted, and @samp{text/richtech} parts are somewhat unwanted,
+you could say something like:
+
+@lisp
+(setq mm-discouraged-alternatives
+ '("text/html" "text/richtext")
+ mm-automatic-display
+ (remove "text/html" mm-automatic-display))
+@end lisp
+
+@item mm-inline-large-images-p
+When displaying inline images that are larger than the window, XEmacs
+does not enable scrolling, which means that you cannot see the whole
+image. To prevent this, the library tries to determine the image size
+before displaying it inline, and if it doesn't fit the window, the
+library will display it externally (e.g. with @samp{ImageMagick} or
+@samp{xv}). Setting this variable to @code{t} disables this check and
+makes the library display all inline images as inline, regardless of
+their size.
+
+@item mm-inline-override-type
+@code{mm-inlined-types} may include regular expressions, for example to
+specify that all @samp{text/.*} parts be displayed inline. If a user
+prefers to have a type that matches such a regular expression be treated
+as an attachment, that can be accomplished by setting this variable to a
+list containing that type. For example assuming @code{mm-inlined-types}
+includes @samp{text/.*}, then including @samp{text/html} in this
+variable will cause @samp{text/html} parts to be treated as attachments.
+
+@end table
+
+
+@node New Viewers
+@section New Viewers
+
+Here's an example viewer for displaying @code{text/enriched} inline:
+
+@lisp
+(defun mm-display-enriched-inline (handle)
+ (let (text)
+ (with-temp-buffer
+ (mm-insert-part handle)
+ (save-window-excursion
+ (enriched-decode (point-min) (point-max))
+ (setq text (buffer-string))))
+ (mm-insert-inline handle text)))
+@end lisp
+
+We see that the function takes a @sc{mime} handle as its parameter. It
+then goes to a temporary buffer, inserts the text of the part, does some
+work on the text, stores the result, goes back to the buffer it was
+called from and inserts the result.
+
+The two important helper functions here are @code{mm-insert-part} and
+@code{mm-insert-inline}. The first function inserts the text of the
+handle in the current buffer. It handles charset and/or content
+transfer decoding. The second function just inserts whatever text you
+tell it to insert, but it also sets things up so that the text can be
+``undisplayed' in a convenient manner.
+
+
+@node Composing
+@chapter Composing
+@cindex Composing
+@cindex MIME Composing
+@cindex MML
+@cindex MIME Meta Language
+
+Creating a @sc{mime} message is boring and non-trivial. Therefore, a
+library called @code{mml} has been defined that parses a language called
+MML (@sc{mime} Meta Language) and generates @sc{mime} messages.
+
+@findex mml-generate-mime
+The main interface function is @code{mml-generate-mime}. It will
+examine the contents of the current (narrowed-to) buffer and return a
+string containing the @sc{mime} message.
+
+@menu
+* Simple MML Example:: An example MML document.
+* MML Definition:: All valid MML elements.
+* Advanced MML Example:: Another example MML document.
+* Charset Translation:: How charsets are mapped from @sc{mule} to MIME.
+* Conversion:: Going from @sc{mime} to MML and vice versa.
+* Flowed text:: Soft and hard newlines.
+@end menu
+
+
+@node Simple MML Example
+@section Simple MML Example
+
+Here's a simple @samp{multipart/alternative}:
+
+@example
+<#multipart type=alternative>
+This is a plain text part.
+<#part type=text/enriched>
+<center>This is a centered enriched part</center>
+<#/multipart>
+@end example
+
+After running this through @code{mml-generate-mime}, we get this:
+
+@example
+Content-Type: multipart/alternative; boundary="=-=-="
+
+
+--=-=-=
+
+
+This is a plain text part.
+
+--=-=-=
+Content-Type: text/enriched
+
+
+<center>This is a centered enriched part</center>
+
+--=-=-=--
+@end example
+
+
+@node MML Definition
+@section MML Definition
+
+The MML language is very simple. It looks a bit like an SGML
+application, but it's not.
+
+The main concept of MML is the @dfn{part}. Each part can be of a
+different type or use a different charset. The way to delineate a part
+is with a @samp{<#part ...>} tag. Multipart parts can be introduced
+with the @samp{<#multipart ...>} tag. Parts are ended by the
+@samp{<#/part>} or @samp{<#/multipart>} tags. Parts started with the
+@samp{<#part ...>} tags are also closed by the next open tag.
+
+There's also the @samp{<#external ...>} tag. These introduce
+@samp{external/message-body} parts.
+
+Each tag can contain zero or more parameters on the form
+@samp{parameter=value}. The values may be enclosed in quotation marks,
+but that's not necessary unless the value contains white space. So
+@samp{filename=/home/user/#hello$^yes} is perfectly valid.
+
+The following parameters have meaning in MML; parameters that have no
+meaning are ignored. The MML parameter names are the same as the
+@sc{mime} parameter names; the things in the parentheses say which
+header it will be used in.
+
+@table @samp
+@item type
+The @sc{mime} type of the part (@code{Content-Type}).
+
+@item filename
+Use the contents of the file in the body of the part
+(@code{Content-Disposition}).
+
+@item charset
+The contents of the body of the part are to be encoded in the character
+set speficied (@code{Content-Type}).
+
+@item name
+Might be used to suggest a file name if the part is to be saved
+to a file (@code{Content-Type}).
+
+@item disposition
+Valid values are @samp{inline} and @samp{attachment}
+(@code{Content-Disposition}).
+
+@item encoding
+Valid values are @samp{7bit}, @samp{8bit}, @samp{quoted-printable} and
+@samp{base64} (@code{Content-Transfer-Encoding}).
+
+@item description
+A description of the part (@code{Content-Description}).
+
+@item creation-date
+RFC822 date when the part was created (@code{Content-Disposition}).
+
+@item modification-date
+RFC822 date when the part was modified (@code{Content-Disposition}).
+
+@item read-date
+RFC822 date when the part was read (@code{Content-Disposition}).
+
+@item recipients
+Who to encrypt/sign the part to. This field is used to override any
+auto-detection based on the To/CC headers.
+
+@item size
+The size (in octets) of the part (@code{Content-Disposition}).
+
+@item sign
+What technology to sign this MML part with (@code{smime}, @code{pgp}
+or @code{pgpmime})
+
+@item encrypt
+What technology to encrypt this MML part with (@code{smime},
+@code{pgp} or @code{pgpmime})
+
+@end table
+
+Parameters for @samp{application/octet-stream}:
+
+@table @samp
+@item type
+Type of the part; informal---meant for human readers
+(@code{Content-Type}).
+@end table
+
+Parameters for @samp{message/external-body}:
+
+@table @samp
+@item access-type
+A word indicating the supported access mechanism by which the file may
+be obtained. Values include @samp{ftp}, @samp{anon-ftp}, @samp{tftp},
+@samp{localfile}, and @samp{mailserver}. (@code{Content-Type}.)
+
+@item expiration
+The RFC822 date after which the file may no longer be fetched.
+(@code{Content-Type}.)
+
+@item size
+The size (in octets) of the file. (@code{Content-Type}.)
+
+@item permission
+Valid values are @samp{read} and @samp{read-write}
+(@code{Content-Type}).
+
+@end table
+
+Parameters for @samp{sign=smime}:
+
+@table @samp
+
+@item keyfile
+File containing key and certificate for signer.
+
+@end table
+
+Parameters for @samp{encrypt=smime}:
+
+@table @samp
+
+@item certfile
+File containing certificate for recipient.
+
+@end table
+
+
+@node Advanced MML Example
+@section Advanced MML Example
+
+Here's a complex multipart message. It's a @samp{multipart/mixed} that
+contains many parts, one of which is a @samp{multipart/alternative}.
+
+@example
+<#multipart type=mixed>
+<#part type=image/jpeg filename=~/rms.jpg disposition=inline>
+<#multipart type=alternative>
+This is a plain text part.
+<#part type=text/enriched name=enriched.txt>
+<center>This is a centered enriched part</center>
+<#/multipart>
+This is a new plain text part.
+<#part disposition=attachment>
+This plain text part is an attachment.
+<#/multipart>
+@end example
+
+And this is the resulting @sc{mime} message:
+
+@example
+Content-Type: multipart/mixed; boundary="=-=-="
+
+
+--=-=-=
+
+
+
+--=-=-=
+Content-Type: image/jpeg;
+ filename="~/rms.jpg"
+Content-Disposition: inline;
+ filename="~/rms.jpg"
+Content-Transfer-Encoding: base64
+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+
+--=-=-=
+Content-Type: multipart/alternative; boundary="==-=-="
+
+
+--==-=-=
+
+
+This is a plain text part.
+
+--==-=-=
+Content-Type: text/enriched;
+ name="enriched.txt"
+
+
+<center>This is a centered enriched part</center>
+
+--==-=-=--
+
+--=-=-=
+
+This is a new plain text part.
+
+--=-=-=
+Content-Disposition: attachment
+
+
+This plain text part is an attachment.
+
+--=-=-=--
+@end example
+
+@node Charset Translation
+@section Charset Translation
+@cindex charsets
+
+During translation from MML to @sc{mime}, for each @sc{mime} part which
+has been composed inside Emacs, an appropriate charset has to be chosen.
+
+@vindex mail-parse-charset
+If you are running a non-@sc{mule} Emacs, this process is simple: If the
+part contains any non-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,
+please consult the documentation of the package which you use to process
+@sc{mime} messages.
+@xref{Various Message Variables, , Various Message Variables, message,
+ Message Manual}, for example.)
+If there are only ASCII characters, the @sc{mime} charset US-ASCII is
+used, of course.
+
+@cindex MULE
+@cindex UTF-8
+@cindex Unicode
+@vindex mm-mime-mule-charset-alist
+Things are slightly more complicated when running Emacs with @sc{mule}
+support. In this case, a list of the @sc{mule} charsets used in the
+part is obtained, and the @sc{mule} charsets are translated to @sc{mime}
+charsets by consulting the variable @code{mm-mime-mule-charset-alist}.
+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
+for some reason, the part is split into several ones, 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.
+
+@node Conversion
+@section Conversion
+
+@findex mime-to-mml
+A (multipart) @sc{mime} message can be converted to MML with the
+@code{mime-to-mml} function. It works on the message in the current
+buffer, and substitutes MML markup for @sc{mime} boundaries.
+Non-textual parts do not have their contents in the buffer, but instead
+have the contents in separate buffers that are referred to from the MML
+tags.
+
+@findex mml-to-mime
+An MML message can be converted back to @sc{mime} by the
+@code{mml-to-mime} function.
+
+These functions are in certain senses ``lossy''---you will not get back
+an identical message if you run @sc{mime-to-mml} and then
+@sc{mml-to-mime}. Not only will trivial things like the order of the
+headers differ, but the contents of the headers may also be different.
+For instance, the original message may use base64 encoding on text,
+while @sc{mml-to-mime} may decide to use quoted-printable encoding, and
+so on.
+
+In essence, however, these two functions should be the inverse of each
+other. The resulting contents of the message should remain equivalent,
+if not identical.
+
+
+@node Flowed text
+@section Flowed text
+@cindex format=flowed
+
+The Emacs @sc{mime} library will respect the @code{use-hard-newlines}
+variable (@pxref{Hard and Soft Newlines, ,Hard and Soft Newlines,
+emacs, Emacs Manual}) when encoding a message, and the
+``format=flowed'' Content-Type parameter when decoding a message.
+
+On encoding text, lines terminated by soft newline characters are
+filled together and wrapped after the column decided by
+@code{fill-flowed-encode-column}. This variable controls how the text
+will look in a client that does not support flowed text, the default
+is to wrap after 66 characters. If hard newline characters are not
+present in the buffer, no flow encoding occurs.
+
+On decoding flowed text, lines with soft newline characters are filled
+together and wrapped after the column decided by
+@code{fill-flowed-display-column}. The default is to wrap after
+@code{fill-column}.
+
+@node Standards
+@chapter Standards
+
+The Emacs @sc{mime} library implements handling of various elements
+according to a (somewhat) large number of RFCs, drafts and standards
+documents. This chapter lists the relevant ones. They can all be
+fetched from @uref{http://quimby.gnus.org/notes/}.
+
+@table @dfn
+@item RFC822
+@itemx STD11
+Standard for the Format of ARPA Internet Text Messages.
+
+@item RFC1036
+Standard for Interchange of USENET Messages
+
+@item RFC2045
+Format of Internet Message Bodies
+
+@item RFC2046
+Media Types
+
+@item RFC2047
+Message Header Extensions for Non-ASCII Text
+
+@item RFC2048
+Registration Procedures
+
+@item RFC2049
+Conformance Criteria and Examples
+
+@item RFC2231
+MIME Parameter Value and Encoded Word Extensions: Character Sets,
+Languages, and Continuations
+
+@item RFC1843
+HZ - A Data Format for Exchanging Files of Arbitrarily Mixed Chinese and
+ASCII characters
+
+@item draft-ietf-drums-msg-fmt-05.txt
+Draft for the successor of RFC822
+
+@item RFC2112
+The MIME Multipart/Related Content-type
+
+@item RFC1892
+The Multipart/Report Content Type for the Reporting of Mail System
+Administrative Messages
+
+@item RFC2183
+Communicating Presentation Information in Internet Messages: The
+Content-Disposition Header Field
+
+@item RFC2646
+Documentation of the text/plain format parameter for flowed text.
+
+@end table
+
@node Index
@chapter Index
@contents
@bye
+\f
+@c Local Variables:
+@c mode: texinfo
+@c coding: iso-8859-1
@c End:
projects / gnus / blobdiff