This is ../info/emacs-mime, produced by makeinfo version 4.6 from
emacs-mime.texi.

INFO-DIR-SECTION The Emacs editor and associated tools
START-INFO-DIR-ENTRY
* Emacs MIME: (emacs-mime).   The MIME de/composition library.
END-INFO-DIR-ENTRY

   This file documents the Emacs MIME interface functionality.

   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
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.

   (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.


File: emacs-mime,  Node: Top,  Next: Interface Functions,  Up: (dir)

Emacs MIME
**********

This manual documents the libraries used to compose and display MIME
messages.

   This is not a manual meant for users; it's a manual directed at
people who want to write functions and commands that manipulate MIME
elements.

   MIME is short for "Multipurpose Internet Mail Extensions".  This
standard is documented in a number of RFCs; mainly RFC2045 (Format of
Internet Message Bodies), RFC2046 (Media Types), RFC2047 (Message
Header Extensions for Non-ASCII Text), RFC2048 (Registration
Procedures), RFC2049 (Conformance Criteria and Examples).  It is highly
recommended that anyone who intends writing MIME-compliant software
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.


File: emacs-mime,  Node: Interface Functions,  Next: Basic Functions,  Prev: Top,  Up: Top

Interface Functions
*******************

The `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 `Content-Type'
header that only allows ASCII characters in the parameter list.
RFC2231 expands on RFC2045 syntax to provide a scheme for continuation
headers and non-ASCII characters.

   The traditional way to deal with this is just to update the library
functions to parse the new syntax.  However, this is sometimes the wrong
thing to do.  In some instances it may be vital to be able to understand
both the old syntax as well as the new syntax, and if there is only one
library, one must choose between the old version of the library and the
new version of the library.

   The Emacs MIME library takes a different tack.  It defines a series
of low-level libraries (`rfc2047.el', `rfc2231.el' and so on) that
parses strictly according to the corresponding standard.  However,
normal programs would not use the functions provided by these libraries
directly, but instead use the functions provided by the `mail-parse'
library.  The functions in this library are just aliases to the
corresponding functions in the latest low-level libraries.  Using this
scheme, programs get a consistent interface they can use, and library
developers are free to create write code that handles new standards.

   The following functions are defined by this library:

 - Function: mail-header-parse-content-type string
     Parse STRING, a `Content-Type' header, and return a content-type
     list in the following format:

          ("type/subtype"
           (attribute1 . value1)
           (attribute2 . value2)
           ...)

     Here's an example:

          (mail-header-parse-content-type
           "image/gif; name=\"b980912.gif\"")
          => ("image/gif" (name . "b980912.gif"))

 - Function: mail-header-parse-content-disposition string
     Parse STRING, a `Content-Disposition' header, and return a
     content-type list in the format above.

 - Function: mail-content-type-get ct attribute
     Returns the value of the given ATTRIBUTE from the content-type
     list CT.

          (mail-content-type-get
           '("image/gif" (name . "b980912.gif")) 'name)
          => "b980912.gif"

 - Function: mail-header-encode-parameter param value
     Takes a parameter string `PARAM=VALUE' and returns an encoded
     version of it.  This is used for parameters in headers like
     `Content-Type' and `Content-Disposition'.

 - Function: mail-header-remove-comments string
     Return a comment-free version of STRING.

          (mail-header-remove-comments
           "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
          => "Gnus/5.070027  "

 - Function: mail-header-remove-whitespace string
     Remove linear white space from STRING.  Space inside quoted
     strings and comments is preserved.

          (mail-header-remove-whitespace
           "image/gif; name=\"Name with spaces\"")
          => "image/gif;name=\"Name with spaces\""

 - Function: mail-header-get-comment string
     Return the last comment in STRING.

          (mail-header-get-comment
           "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
          => "Finnish Landrace"

 - Function: mail-header-parse-address string
     Parse an address string STRING and return a list containing the
     mailbox and the plaintext name.

          (mail-header-parse-address
           "Hrvoje Niksic <hniksic@srce.hr>")
          => ("hniksic@srce.hr" . "Hrvoje Niksic")

 - Function: mail-header-parse-addresses string
     Parse STRING as a list of addresses and return a list of elements
     like the one described above.

          (mail-header-parse-addresses
           "Hrvoje Niksic <hniksic@srce.hr>, Steinar Bang <sb@metis.no>")
          => (("hniksic@srce.hr" . "Hrvoje Niksic")
               ("sb@metis.no" . "Steinar Bang"))

 - Function: mail-header-parse-date string
     Parse a date STRING and return an Emacs time structure.

 - Function: mail-narrow-to-head
     Narrow the buffer to the header section of the buffer.  Point is
     placed at the beginning of the narrowed buffer.

 - Function: mail-header-narrow-to-field
     Narrow the buffer to the header under point.

 - Function: mail-encode-encoded-word-region start end
     Encode the non-ASCII words in the region STARTto END.  For
     instance, `Naïve' is encoded as `=?iso-8859-1?q?Na=EFve?='.

 - Function: mail-encode-encoded-word-buffer
     Encode the non-ASCII words in the current buffer.  This function is
     meant to be called with the buffer narrowed to the headers of a
     message.

 - Function: mail-encode-encoded-word-string string
     Encode the words that need encoding in STRING, and return the
     result.

          (mail-encode-encoded-word-string
           "This is naïve, baby")
          => "This is =?iso-8859-1?q?na=EFve,?= baby"

 - Function: mail-decode-encoded-word-region start end
     Decode the encoded words in the region STARTto END.

 - Function: mail-decode-encoded-word-string string
     Decode the encoded words in STRING and return the result.

          (mail-decode-encoded-word-string
           "This is =?iso-8859-1?q?na=EFve,?= baby")
          => "This is naïve, baby"

   Currently, `mail-parse' is an abstraction over `ietf-drums',
`rfc2047', `rfc2045' and `rfc2231'.  These are documented in the
subsequent sections.


File: emacs-mime,  Node: Basic Functions,  Next: Decoding and Viewing,  Prev: Interface Functions,  Up: Top

Basic Functions
***************

This chapter describes the basic, ground-level functions for parsing and
handling.  Covered here is parsing `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 (*note
Decoding and Viewing::).

* Menu:

* rfc2045::      Encoding `Content-Type' headers.
* rfc2231::      Parsing `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 mailcap files


File: emacs-mime,  Node: rfc2045,  Next: rfc2231,  Up: Basic Functions

rfc2045
=======

RFC2045 is the "main" 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 `rfc2045.el' has only a single function:

 - Function: rfc2045-encode-string parameter value
     Takes a PARAMETER and a VALUE and returns a `PARAM=VALUE' string.
     VALUE will be quoted if there are non-safe characters in it.


File: emacs-mime,  Node: rfc2231,  Next: ietf-drums,  Prev: rfc2045,  Up: Basic Functions

rfc2231
=======

RFC2231 defines a syntax for the `Content-Type' and
`Content-Disposition' headers.  Its snappy name is "MIME Parameter
Value and Encoded Word Extensions: Character Sets, Languages, and
Continuations".

   In short, these headers look something like this:

     Content-Type: 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!"

   They usually aren't this bad, though.

   The following functions are defined by this library:

 - Function: rfc2231-parse-string string
     Parse a `Content-Type' header STRING and return a list describing
     its elements.

          (rfc2231-parse-string
           "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"
              (title . "This is even more ***fun*** isn't it!"))

 - Function: rfc2231-get-value ct attribute
     Takes a list CT of the format above and returns the value of the
     specified ATTRIBUTE.

 - Function: rfc2231-encode-string parameter value
     Encode the string `PARAMETER=VALUE' for inclusion in headers likes
     `Content-Type' and `Content-Disposition'.


File: emacs-mime,  Node: ietf-drums,  Next: rfc2047,  Prev: rfc2231,  Up: Basic Functions

ietf-drums
==========

"drums" is an IETF working group that is working on the replacement for
RFC822.

   The functions provided by this library include:

 - Function: ietf-drums-remove-comments string
     Remove the comments from STRING and return the result.

 - Function: ietf-drums-remove-whitespace string
     Remove linear white space from STRING and return the result.
     Spaces inside quoted strings and comments are left untouched.

 - Function: ietf-drums-get-comment string
     Return the last most comment from STRING.

 - Function: ietf-drums-parse-address string
     Parse an address STRING and return a list of the mailbox and the
     plain text name.

 - Function: ietf-drums-parse-addresses string
     Parse STRING, containing any number of comma-separated addresses,
     and return a list of mailbox/plain text pairs.

 - Function: ietf-drums-parse-date string
     Parse the date STRING and return an Emacs time structure.

 - Function: ietf-drums-narrow-to-header
     Narrow the buffer to the header section of the current buffer.


File: emacs-mime,  Node: rfc2047,  Next: time-date,  Prev: ietf-drums,  Up: Basic Functions

rfc2047
=======

RFC2047 (Message Header Extensions for Non-ASCII Text) specifies how
non-ASCII text in headers are to be encoded.  This is actually rather
complicated, so a number of variables are necessary to tweak what this
library does.

   The following variables are tweakable:

 - Variable: rfc2047-default-charset
     Characters in this charset should not be decoded by this library.
     This defaults to `iso-8859-1'.

 - Variable: rfc2047-header-encoding-list
     This is an alist of header / encoding-type pairs.  Its main
     purpose is to prevent encoding of certain headers.

   The keys can either be header regexps, or `t'.

   The values can be either `nil', in which case the header(s) in
question won't be encoded, or `mime', which means that they will be
encoded.

 - Variable: rfc2047-charset-encoding-alist
     RFC2047 specifies two forms of encoding--`Q' (a
     Quoted-Printable-like encoding) and `B' (base64).  This alist
     specifies which charset should use which encoding.

 - Variable: rfc2047-encoding-function-alist
     This is an alist of encoding / function pairs.  The encodings are
     `Q', `B' and `nil'.

 - Variable: rfc2047-q-encoding-alist
     The `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 and allowable
     character ranges.

 - Variable: rfc2047-encoded-word-regexp
     When decoding words, this library looks for matches to this regexp.

   Those were the variables, and these are the functions:

 - Function: rfc2047-narrow-to-field
     Narrow the buffer to the header on the current line.

 - Function: rfc2047-encode-message-header
     Should be called narrowed to the header of a message.  Encodes
     according to `rfc2047-header-encoding-alist'.

 - Function: rfc2047-encode-region start end
     Encodes all encodable words in the region START to END.

 - Function: rfc2047-encode-string string
     Encode STRING and return the result.

 - Function: rfc2047-decode-region start end
     Decode the encoded words in the region START to END.

 - Function: rfc2047-decode-string string
     Decode STRING and return the result.


File: emacs-mime,  Node: time-date,  Next: qp,  Prev: rfc2047,  Up: Basic Functions

time-date
=========

While not really a part of the MIME library, it is convenient to
document this library here.  It deals with parsing `Date' headers and
manipulating time.  (Not by using tesseracts, though, I'm sorry to say.)

   These functions convert between five formats: a date string, an Emacs
time structure, a decoded time list, a number of seconds, and a day
number.

   The functions have quite self-explanatory names, so the following
just gives an overview of which functions are available.

     (parse-time-string "Sat Sep 12 12:21:54 1998 +0200")
     => (54 21 12 12 9 1998 6 nil 7200)
     
     (date-to-time "Sat Sep 12 12:21:54 1998 +0200")
     => (13818 19266)
     
     (time-to-seconds '(13818 19266))
     => 905595714.0
     
     (seconds-to-time 905595714.0)
     => (13818 19266 0)
     
     (time-to-day '(13818 19266))
     => 729644
     
     (days-to-time 729644)
     => (961933 65536)
     
     (time-since '(13818 19266))
     => (0 430)
     
     (time-less-p '(13818 19266) '(13818 19145))
     => nil
     
     (subtract-time '(13818 19266) '(13818 19145))
     => (0 121)
     
     (days-between "Sat Sep 12 12:21:54 1998 +0200"
                   "Sat Sep 07 12:21:54 1998 +0200")
     => 5
     
     (date-leap-year-p 2000)
     => t
     
     (time-to-day-in-year '(13818 19266))
     => 255

   And finally, we have `safe-date-to-time', which does the same as
`date-to-time', but returns a zero time if the date is syntactically
malformed.


File: emacs-mime,  Node: qp,  Next: base64,  Prev: time-date,  Up: Basic Functions

qp
==

This library deals with decoding and encoding Quoted-Printable text.

   Very briefly explained, QP encoding means translating all 8-bit
characters (and lots of control characters) into things that look like
`=EF'; that is, an equal sign followed by the byte encoded as a hex
string.  It is defined in RFC 2045.

   The following functions are defined by the library:

 - Command: quoted-printable-decode-region FROM TO &optional
          CODING-SYSTEM
     QP-decode all the encoded text in the region.  If CODING-SYSTEM is
     non-nil, decode bytes into characters with that coding-system.  It
     is probably better not to use CODING-SYSTEM; instead decode into a
     unibyte buffer, decode that appropriately and then interpret it as
     multibyte.

 - Function: quoted-printable-decode-string STRING &optional
          CODING-SYSTEM
     Return a QP-encoded copy of STRING.  If CODING-SYSTEM is non-nil,
     decode bytes into characters with that coding-system.

 - Command: quoted-printable-encode-region FROM TO &optional FOLD CLASS
     QP-encode all the region.  If FOLD is non-NIL, fold lines at 76
     characters, as required by the RFC.  If CLASS is non-`nil',
     translate the characters not matched by that regexp class, which
     should be in the form expected by SKIP-CHARS-FORWARD and should
     probably not contain literal eight-bit characters.  Specifying
     CLASS makes sense to do extra encoding in header fields.

     If variable MM-USE-ULTRA-SAFE-ENCODING is defined and non-`nil',
     fold lines unconditionally and encode `From ' and `-' at the start
     of lines..

 - Function: quoted-printable-encode-string string
     Return a QP-encoded copy of STRING.


File: emacs-mime,  Node: base64,  Next: binhex,  Prev: qp,  Up: Basic Functions

base64
======

Base64 is an encoding that encodes three bytes into four characters,
thereby increasing the size by about 33%.  The alphabet used for
encoding is very resistant to mangling during transit.  *Note Base 64
Encoding: (elisp)Base 64.


File: emacs-mime,  Node: binhex,  Next: uudecode,  Prev: base64,  Up: Basic Functions

binhex
======

Binhex is an encoding that originated in Macintosh environments.  The
following function is supplied to deal with these:

 - Function: binhex-decode-region start end &optional header-only
     Decode the encoded text in the region START to END.  If
     HEADER-ONLY is non-`nil', only decode the `binhex' header and
     return the file name.


File: emacs-mime,  Node: uudecode,  Next: rfc1843,  Prev: binhex,  Up: Basic Functions

uudecode
========

Uuencoding is probably still the most popular encoding of binaries used
on Usenet, although Base64 rules the mail world.

   The following function is supplied by this package:

 - Function: uudecode-decode-region start end &optional file-name
     Decode the text in the region START to END.  If FILE-NAME is
     non-`nil', save the result to FILE-NAME.


File: emacs-mime,  Node: rfc1843,  Next: mailcap,  Prev: uudecode,  Up: Basic Functions

rfc1843
=======

RFC1843 deals with mixing Chinese and ASCII characters in messages.  In
essence, RFC1843 switches between ASCII and Chinese by doing this:

     This sentence is in ASCII.
     The next sentence is in GB.~{<:Ky2;S{#,NpJ)l6HK!#~}Bye.

   Simple enough, and widely used in China.

   The following functions are available to handle this encoding:

 - Function: rfc1843-decode-region start end
     Decode HZ-encoded text in the region START to END.

 - Function: rfc1843-decode-string string
     Decode the HZ-encoded STRING and return the result.


File: emacs-mime,  Node: mailcap,  Prev: rfc1843,  Up: Basic Functions

mailcap
=======

As specified by RFC 1524, MIME-aware message handlers parse "mailcap"
files from a default list, which can be overridden by the `MAILCAP'
environment variable.  These describe how elements are supposed to be
displayed.  Here's an example file:

     image/*; gimp -8 %s
     audio/wav; wavplayer %s

   This says that all image files should be displayed with `gimp', and
that WAVE audio files should be played by `wavplayer'.

   The `mailcap' library parses such files, and provides functions for
matching types.

 - Variable: mailcap-mime-data
     This variable is an alist of alists containing backup viewing
     rules for MIME types.  These are overridden by rules for a type
     found in mailcap files.  The outer alist is keyed on the major
     content-type and the inner alists are keyed on the minor
     content-type (which can be a regular expression).

     For example:
          (("application"
            ("octet-stream"
             (viewer . mailcap-save-binary-file)
             (non-viewer . t)
             (type . "application/octet-stream"))
            ("plain"
             (viewer . view-mode)
             (test fboundp 'view-mode)
             (type . "text/plain")))

 - User Option: mailcap-default-mime-data
     This variable is the default value of `mailcap-mime-data'.  It
     exists to allow setting the value using Custom.  It is merged with
     values from mailcap files by `mailcap-parse-mailcaps'.

   Although it is not specified by the RFC, MIME tools normally use a
common means of associating file extensions with defualt MIME types in
the absence of other information about the type of a file.  The
information is found in per-user files `~/.mime.types' and system
`mime.types' files found in quasi-standard places.  Here is an example:

     application/x-dvi	dvi
     audio/mpeg		mpga mpega mp2 mp3
     image/jpeg		jpeg jpg jpe

 - Variable: mailcap-mime-extensions
     This variable is an alist MIME types keyed by file extensions.
     This is overridden by entries found in `mime.types' files.

 - User Option: mailcap-default-mime-extensions
     This variable is the default value of `mailcap-mime-extensions'.
     It exists to allow setting the value using Custom.  It is merged
     with values from mailcap files by `mailcap-parse-mimetypes'.

   Interface functions:

 - Function: mailcap-parse-mailcaps &optional path force
     Parse all the mailcap files specified in a path string PATH and
     merge them with the values from `mailcap-mime-data'.  Components of
     PATH are separated by the `path-separator' character appropriate
     for the system.  If FORCE is non-`nil', the files are re-parsed
     even if they have been parsed already.  If PATH is omitted, use
     the value of environment variable `MAILCAPS' if it is set;
     otherwise (on GNU and Unix) use the path defined in RFC 1524, plus
     `/usr/local/etc/mailcap'.

 - Function: mailcap-parse-mimetypes &optional path force
     Parse all the mimetypes specified in a path string PATH and merge
     them with the values from `mailcap-mime-extensions'.  Components
     of PATH are separated by the `path-separator' character
     appropriate for the system.  If PATH is omitted, use the value of
     environment variable `MIMETYPES' if set; otherwise use a default
     path consistent with that used by `mailcap-parse-mailcaps'.  If
     FORCE is non-`nil', the files are re-parsed even if they have been
     parsed already.

 - Function: mailcap-mime-info string &optional request
     Gets the viewer command for content-type STRING.  `nil' is
     returned if none is found.  Expects STRING to be a complete
     content-type header line.

     If REQUEST is non-`nil' it specifies what information to return.
     If it is nil or the empty string, the viewer (second field of the
     mailcap entry) will be returned.  If it is a string, then the
     mailcap field corresponding to that string will be returned
     (`print', `description', whatever).  If it is a number, all the
     information for this viewer is returned.  If it is `all', then all
     possible viewers for this type is returned.

 - Function: mailcap-mime-types
     This function returns a list of all the defined media types.

 - Function: mailcap-extension-to-mime extension
     This function returns the content type defined for a file with the
     given EXTENSION.


File: emacs-mime,  Node: Decoding and Viewing,  Next: Composing,  Prev: Basic Functions,  Up: Top

Decoding and Viewing
********************

This chapter deals with decoding and viewing MIME messages on a higher
level.

   The main idea is to first analyze a MIME article, and then allow
other programs to do things based on the list of "handles" that are
returned as a result of this analysis.

* Menu:

* Dissection::     Analyzing a MIME message.
* Handles::        Handle manipulations.
* Display::        Displaying handles.
* Customization::  Variables that affect display.
* New Viewers::    How to write your own viewers.


File: emacs-mime,  Node: Dissection,  Next: Handles,  Up: Decoding and Viewing

Dissection
==========

The `mm-dissect-buffer' is the function responsible for dissecting a
MIME article.  If given a multipart message, it will recursively
descend the message, following the structure, and return a tree of MIME
handles that describes the structure of the message.


File: emacs-mime,  Node: Handles,  Next: Display,  Prev: Dissection,  Up: Decoding and Viewing

Handles
=======

A MIME handle is a list that fully describes a MIME component.

   The following macros can be used to access elements from the HANDLE
argument:

 - Macro: mm-handle-buffer handle
     Return the buffer that holds the contents of the undecoded MIME
     part.

 - Macro: mm-handle-type handle
     Return the parsed `Content-Type' of the part.

 - Macro: mm-handle-encoding handle
     Return the `Content-Transfer-Encoding' of the part.

 - Macro: mm-handle-undisplayer handle
     Return the function that can be used to remove the displayed part
     (if it has been displayed).

 - Macro: mm-handle-set-undisplayer handle function
     Set the undisplayer function for the part to function.

 - Macro: mm-handle-disposition
     Return the parsed `Content-Disposition' of the part.

 - Macro: mm-handle-disposition
     Return the description of the part.

 - Macro: mm-get-content-id id
     Returns the handle(s) referred to by ID, the `Content-ID' of the
     part.


File: emacs-mime,  Node: Display,  Next: Customization,  Prev: Handles,  Up: Decoding and Viewing

Display
=======

Functions for displaying, removing and saving.  In the descriptions
below, `the part' means the MIME part represented by the HANDLE
argument.

 - Function: mm-display-part handle &optional no-default
     Display the part.  Return `nil' if the part is removed, `inline'
     if it is displayed inline or `external' if it is displayed
     externally.  If NO-DEFAULT is non-`nil', the part is not displayed
     unless the MIME type of HANDLE is defined to be displayed inline
     or there is an display method defined for it; i.e.  no default
     external method will be used.

 - Function: mm-remove-part handle
     Remove the part if it has been displayed.

 - Function: mm-inlinable-p handle
     Return non-`nil' if the part can be displayed inline.

 - Function: mm-automatic-display-p handle
     Return non-`nil' if the user has requested automatic display of the
     MIME type of the part.

 - Function: mm-destroy-part handle
     Free all the resources used by the part.

 - Function: mm-save-part handle
     Save the part to a file.  The user is prompted for a file name to
     use.

 - Function: mm-pipe-part handle
     Pipe the part through a shell command.  The user is prompted for
     the command to use.

 - Function: mm-interactively-view-part handle
     Prompt for a mailcap method to use to view the part and display it
     externally using that method.


File: emacs-mime,  Node: Customization,  Next: New Viewers,  Prev: Display,  Up: Decoding and Viewing

Customization
=============

The display of MIME types may be customized with the following options.

 - User Option: mm-inline-media-tests
     This is an alist where the key is a MIME type, the second element
     is a function to display the part "inline" (i.e., inside Emacs),
     and the third element is a form to be `eval'ed to say whether the
     part can be displayed inline.

     This variable specifies whether a part _can_ be displayed inline,
     and, if so, how to do it.  It does not say whether parts are
     _actually_ displayed inline.

 - User Option: 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 MIME media types.

 - User Option: 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.

 - User Option: mm-attachment-override-types
     Some MIME agents create parts that have a content-disposition of
     `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.)

 - User Option: mm-discouraged-alternatives
     List of MIME types that are discouraged when viewing
     `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,
     `text/html' parts are very unwanted, and `text/richtech' parts are
     somewhat unwanted, then the value of this variable should be set
     to:

          ("text/html" "text/richtext")

 - User Option: 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
     `ImageMagick' or `xv').  Setting this variable to `t' disables
     this check and makes the library display all inline images as
     inline, regardless of their size.

 - User Option: mm-inline-override-p
     `mm-inlined-types' may include regular expressions, for example to
     specify that all `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
     `mm-inlined-types' includes `text/.*', then including `text/html'
     in this variable will cause `text/html' parts to be treated as
     attachments.


File: emacs-mime,  Node: New Viewers,  Prev: Customization,  Up: Decoding and Viewing

New Viewers
===========

Here's an example viewer for displaying `text/enriched' inline:

     (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)))

   We see that the function takes a 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 `mm-insert-part' and
`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.


File: emacs-mime,  Node: Composing,  Next: Standards,  Prev: Decoding and Viewing,  Up: Top

Composing
*********

Creating a MIME message is boring and non-trivial.  Therefore, a
library called `mml' has been defined that parses a language called MML
(MIME Meta Language) and generates MIME messages.

   The main interface function is `mml-generate-mime'.  It will examine
the contents of the current (narrowed-to) buffer and return a string
containing the 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 Mule to MIME.
* Conversion::                     Going from MIME to MML and vice versa.


File: emacs-mime,  Node: Simple MML Example,  Next: MML Definition,  Up: Composing

Simple MML Example
==================

Here's a simple `multipart/alternative':

     <#multipart type=alternative>
     This is a plain text part.
     <#part type=text/enriched>
     <center>This is a centered enriched part</center>
     <#/multipart>

   After running this through `mml-generate-mime', we get this:

     Content-Type: multipart/alternative; boundary="=-=-="
     
     
     --=-=-=
     
     
     This is a plain text part.
     
     --=-=-=
     Content-Type: text/enriched
     
     
     <center>This is a centered enriched part</center>
     
     --=-=-=--


File: emacs-mime,  Node: MML Definition,  Next: Advanced MML Example,  Prev: Simple MML Example,  Up: Composing

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 "part".  Each part can be of a
different type or use a different charset.  The way to delineate a part
is with a `<#part ...>' tag.  Multipart parts can be introduced with
the `<#multipart ...>' tag.  Parts are ended by the `<#/part>' or
`<#/multipart>' tags.  Parts started with the `<#part ...>' tags are
also closed by the next open tag.

   There's also the `<#external ...>' tag.  These introduce
`external/message-body' parts.

   Each tag can contain zero or more parameters on the form
`parameter=value'.  The values may be enclosed in quotation marks, but
that's not necessary unless the value contains white space.  So
`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 MIME
parameter names; the things in the parentheses say which header it will
be used in.

`type'
     The MIME type of the part (`Content-Type').

`filename'
     Use the contents of the file in the body of the part
     (`Content-Disposition').

`charset'
     The contents of the body of the part are to be encoded in the
     character set speficied (`Content-Type').

`name'
     Might be used to suggest a file name if the part is to be saved to
     a file (`Content-Type').

`disposition'
     Valid values are `inline' and `attachment' (`Content-Disposition').

`encoding'
     Valid values are `7bit', `8bit', `quoted-printable' and `base64'
     (`Content-Transfer-Encoding').

`description'
     A description of the part (`Content-Description').

`creation-date'
     RFC822 date when the part was created (`Content-Disposition').

`modification-date'
     RFC822 date when the part was modified (`Content-Disposition').

`read-date'
     RFC822 date when the part was read (`Content-Disposition').

`size'
     The size (in octets) of the part (`Content-Disposition').


   Parameters for `application/octet-stream':

`type'
     Type of the part; informal--meant for human readers
     (`Content-Type').

   Parameters for `message/external-body':

`access-type'
     A word indicating the supported access mechanism by which the file
     may be obtained.  Values include `ftp', `anon-ftp', `tftp',
     `localfile', and `mailserver'.  (`Content-Type'.)

`expiration'
     The RFC822 date after which the file may no longer be fetched.
     (`Content-Type'.)

`size'
     The size (in octets) of the file.  (`Content-Type'.)

`permission'
     Valid values are `read' and `read-write' (`Content-Type').



File: emacs-mime,  Node: Advanced MML Example,  Next: Charset Translation,  Prev: MML Definition,  Up: Composing

Advanced MML Example
====================

Here's a complex multipart message.  It's a `multipart/mixed' that
contains many parts, one of which is a `multipart/alternative'.

     <#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>

   And this is the resulting MIME message:

     Content-Type: multipart/mixed; boundary="=-=-="
     
     
     --=-=-=
     
     
     
     --=-=-=
     Content-Type: image/jpeg;
      filename="~/rms.jpg"
     Content-Disposition: inline;
      filename="~/rms.jpg"
     Content-Transfer-Encoding: base64
     
     /9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRof
     Hh0aHBwgJC4nICIsIxwcKDcpLDAxNDQ0Hyc5PTgyPC4zNDL/wAALCAAwADABAREA/8QAHwAA
     AQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQR
     BRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RF
     RkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ip
     qrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/9oACAEB
     AAA/AO/rifFHjldNuGsrDa0qcSSHkA+gHrXKw+LtWLrMb+RgTyhbr+HSug07xNqV9fQtZrNI
     AyiaE/NuBPOOOP0rvRNE880KOC8TbXXGCv1FPqjrF4LDR7u5L7SkTFT/ALWOP1xXgTuXfc7E
     sx6nua6rwp4IvvEM8chCxWxOdzn7wz6V9AaB4S07w9p5itow0rDLSY5Pt9K43xO66P4xs71m
     2QXiGCbA4yOVJ9+1aYORkdK434lyNH4ahCnG66VT9Nj15JFbPdX0MS43M4VQf5/yr2vSpLnw
     5ZW8dlCZ8KFXjOPX0/mK6rSPEGt3Angu44fNEReHYNvIH3TzXDeKNO8RX+kSX2ouZkicTIOc
     L+g7E810ulFjpVtv3bwgB3HJyK5L4quY/C9sVxk3ij/xx6850u7t1mtp/wDlpEw3An3Jr3Dw
     34gsbWza4nBlhC5LDsaW6+IFgupQyCF3iHH7gA7c9R9ay7zx6t7aX9jHC4smhfBkGCvHGfrm
     tLQ7hbnRrV1GPkAP1x1/Hr+Ncr8Vzjwrbf8AX6v/AKA9eQRyYlQk8Yx9K6XTNbkgia2ciSIn
     7p5Ga9Atte0LTLKO6it4i7dVRFJDcZ4PvXN+JvEMF9bILVGXJLSZ4zkjivRPDaeX4b08HOTC
     pOffmua+KkbS+GLVUGT9tT/0B68eeIpIFYjB70+OOVXyoOM9+M1eaWeCLzHPyHGO/NVWvJJm
     jQ8KGH1NfQWhXSXmh2c8eArRLwO3HSv/2Q==
     
     --=-=-=
     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.
     
     --=-=-=--


File: emacs-mime,  Node: Charset Translation,  Next: Conversion,  Prev: Advanced MML Example,  Up: Composing

Charset Translation
===================

During translation from MML to MIME, for each MIME part which has been
composed inside Emacs, an appropriate MIME charset has to be chosen.

   If you are running a non-Mule XEmacs, or Emacs in unibyte mode(1),
this process is simple: if the part contains any non-ASCII (8-bit)
characters, the MIME charset given by `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 MIME messages.  *Note Various Message
Variables: (message)Various Message Variables, for example.)  If there
are only ASCII characters, the MIME charset `US-ASCII' is used, of
course.

   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 `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/MIME charset.(2)  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.

   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 MIME charsets are determined by lookup in
`mm-mime-mule-charset-alist'.  If the list elements all correspond to a
single MIME charset, that is used to encode the part.  Otherwise, the
part is split as above.

   ---------- Footnotes ----------

   (1) Deprecated!

   (2) The part can only be split at line boundaries, though--if more
than one MIME charset is required to encode a single line, it is not
possible to encode the part.


File: emacs-mime,  Node: Conversion,  Prev: Charset Translation,  Up: Composing

Conversion
==========

A (multipart) MIME message can be converted to MML with the
`mime-to-mml' function.  It works on the message in the current buffer,
and substitutes MML markup for 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.

   An MML message can be converted back to MIME by the `mml-to-mime'
function.

   These functions are in certain senses "lossy"--you will not get back
an identical message if you run MIME-TO-MML and then 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 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.


File: emacs-mime,  Node: Standards,  Next: Index,  Prev: Composing,  Up: Top

Standards
*********

The Emacs 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 `http://quimby.gnus.org/notes/'.

"RFC822"
"STD11"
     Standard for the Format of ARPA Internet Text Messages.

"RFC1036"
     Standard for Interchange of USENET Messages

"RFC1524"
     A User Agent Configuration Mechanism For Multimedia Mail Format
     Information

"RFC2045"
     Format of Internet Message Bodies

"RFC2046"
     Media Types

"RFC2047"
     Message Header Extensions for Non-ASCII Text

"RFC2048"
     Registration Procedures

"RFC2049"
     Conformance Criteria and Examples

"RFC2231"
     MIME Parameter Value and Encoded Word Extensions: Character Sets,
     Languages, and Continuations

"RFC1843"
     HZ - A Data Format for Exchanging Files of Arbitrarily Mixed
     Chinese and ASCII characters

"draft-ietf-drums-msg-fmt-05.txt"
     Draft for the successor of RFC822

"RFC2112"
     The MIME Multipart/Related Content-type

"RFC1892"
     The Multipart/Report Content Type for the Reporting of Mail System
     Administrative Messages

"RFC2183"
     Communicating Presentation Information in Internet Messages: The
     Content-Disposition Header Field



File: emacs-mime,  Node: Index,  Prev: Standards,  Up: Top

Index
*****

* Menu:

* Apple:                                 binhex.
* base64:                                base64.
* binhex:                                binhex.
* binhex-decode-region:                  binhex.
* charsets:                              Charset Translation.
* Chinese:                               rfc1843.
* Composing:                             Composing.
* date-leap-year-p:                      time-date.
* date-to-time:                          time-date.
* days-between:                          time-date.
* days-to-time:                          time-date.
* HZ:                                    rfc1843.
* ietf-drums-get-comment:                ietf-drums.
* ietf-drums-narrow-to-header:           ietf-drums.
* ietf-drums-parse-address:              ietf-drums.
* ietf-drums-parse-addresses:            ietf-drums.
* ietf-drums-parse-date:                 ietf-drums.
* ietf-drums-remove-comments:            ietf-drums.
* ietf-drums-remove-whitespace:          ietf-drums.
* interface functions:                   Interface Functions.
* Macintosh:                             binhex.
* mail-content-type-get:                 Interface Functions.
* mail-decode-encoded-word-region:       Interface Functions.
* mail-decode-encoded-word-string:       Interface Functions.
* mail-encode-encoded-word-buffer:       Interface Functions.
* mail-encode-encoded-word-region:       Interface Functions.
* mail-encode-encoded-word-string:       Interface Functions.
* mail-header-encode-parameter:          Interface Functions.
* mail-header-get-comment:               Interface Functions.
* mail-header-narrow-to-field:           Interface Functions.
* mail-header-parse-address:             Interface Functions.
* mail-header-parse-addresses:           Interface Functions.
* mail-header-parse-content-disposition: Interface Functions.
* mail-header-parse-content-type:        Interface Functions.
* mail-header-parse-date:                Interface Functions.
* mail-header-remove-comments:           Interface Functions.
* mail-header-remove-whitespace:         Interface Functions.
* mail-narrow-to-head:                   Interface Functions.
* mail-parse:                            Interface Functions.
* mail-parse-charset:                    Charset Translation.
* mailcap-default-mime-data:             mailcap.
* mailcap-default-mime-extensions:       mailcap.
* mailcap-extension-to-mime:             mailcap.
* mailcap-mime-data:                     mailcap.
* mailcap-mime-extensions:               mailcap.
* mailcap-mime-info:                     mailcap.
* mailcap-mime-types:                    mailcap.
* mailcap-parse-mailcaps:                mailcap.
* mailcap-parse-mimetypes:               mailcap.
* MIME Composing:                        Composing.
* MIME Meta Language:                    Composing.
* mime-charset property:                 Charset Translation.
* mime-to-mml:                           Conversion.
* mm-attachment-override-types:          Customization.
* mm-automatic-display:                  Customization.
* mm-automatic-display-p:                Display.
* mm-destroy-part:                       Display.
* mm-discouraged-alternatives:           Customization.
* mm-display-part:                       Display.
* mm-get-content-id:                     Handles.
* mm-handle-buffer:                      Handles.
* mm-handle-disposition:                 Handles.
* mm-handle-encoding:                    Handles.
* mm-handle-set-undisplayer:             Handles.
* mm-handle-type:                        Handles.
* mm-handle-undisplayer:                 Handles.
* mm-inlinable-p:                        Display.
* mm-inline-large-images-p:              Customization.
* mm-inline-media-tests:                 Customization.
* mm-inline-override-p:                  Customization.
* mm-inlined-types:                      Customization.
* mm-interactively-view-part:            Display.
* mm-mime-mule-charset-alist:            Charset Translation.
* mm-pipe-part:                          Display.
* mm-remove-part:                        Display.
* mm-save-part:                          Display.
* MML:                                   Composing.
* mml-generate-mime:                     Composing.
* mml-to-mime:                           Conversion.
* multibyte Emacs:                       Charset Translation.
* parse-time-string:                     time-date.
* quoted-printable-decode-region:        qp.
* quoted-printable-decode-string:        qp.
* quoted-printable-encode-region:        qp.
* quoted-printable-encode-string:        qp.
* rfc1843:                               rfc1843.
* rfc1843-decode-region:                 rfc1843.
* rfc1843-decode-string:                 rfc1843.
* rfc2045-encode-string:                 rfc2045.
* rfc2047-charset-encoding-alist:        rfc2047.
* rfc2047-decode-region:                 rfc2047.
* rfc2047-decode-string:                 rfc2047.
* rfc2047-default-charset:               rfc2047.
* rfc2047-encode-message-header:         rfc2047.
* rfc2047-encode-region:                 rfc2047.
* rfc2047-encode-string:                 rfc2047.
* rfc2047-encoded-word-regexp:           rfc2047.
* rfc2047-encoding-function-alist:       rfc2047.
* rfc2047-header-encoding-list:          rfc2047.
* rfc2047-narrow-to-field:               rfc2047.
* rfc2047-q-encoding-alist:              rfc2047.
* rfc2231-encode-string:                 rfc2231.
* rfc2231-get-value:                     rfc2231.
* rfc2231-parse-string:                  rfc2231.
* safe-date-to-time:                     time-date.
* seconds-to-time:                       time-date.
* subtract-time:                         time-date.
* time-less-p:                           time-date.
* time-since:                            time-date.
* time-to-day:                           time-date.
* time-to-day-in-year:                   time-date.
* time-to-seconds:                       time-date.
* unibyte Emacs:                         Charset Translation.
* uudecode:                              uudecode.
* uudecode-decode-region:                uudecode.
* uuencode:                              uudecode.
* XEmacs/Mule:                           Charset Translation.

* Menu:


Tag Table:
Node: Top1286
Node: Interface Functions2449
Node: Basic Functions8101
Node: rfc20459113
Node: rfc22319647
Node: ietf-drums11027
Node: rfc204712183
Node: time-date14514
Node: qp16098
Node: base6417894
Node: binhex18223
Node: uudecode18671
Node: rfc184319137
Node: mailcap19793
Node: Decoding and Viewing24279
Node: Dissection24913
Node: Handles25278
Node: Display26367
Node: Customization27870
Node: New Viewers30985
Node: Composing32093
Node: Simple MML Example32914
Node: MML Definition33589
Node: Advanced MML Example36402
Node: Charset Translation39236
Ref: Charset Translation-Footnote-141224
Ref: Charset Translation-Footnote-241244
Node: Conversion41413
Node: Standards42501
Node: Index43902

End Tag Table
