-\input texinfo @c -*-texinfo-*-
+\input texinfo
@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, 2001, 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 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
This manual documents the libraries used to compose and display
@sc{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 @sc{mime}
-elements.
+This manual is directed at users who want to modify the behaviour of
+the MIME encoding/decoding process or want a more detailed picture of
+how the Emacs MIME library works, and people who want to write
+functions and commands that manipulate @sc{mime} elements.
@sc{mime} is short for @dfn{Multipurpose Internet Mail Extensions}.
This standard is documented in a number of RFCs; mainly RFC2045 (Format
read at least RFC2045 and RFC2047.
@menu
+* Decoding and Viewing:: A framework for decoding and viewing.
+* Composing:: MML; a language for describing @sc{mime} parts.
* Interface Functions:: An abstraction over the basic functions.
* Basic Functions:: Utility and basic parsing functions.
-* Decoding and Viewing:: A framework for decoding and viewing.
* Standards:: A summary of RFCs and working documents used.
* Index:: Function and variable index.
@end menu
+@node Decoding and Viewing
+@chapter Decoding and Viewing
+
+This chapter deals with decoding and viewing @sc{mime} messages on a
+higher level.
+
+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 analysis.
+
+@menu
+* Dissection:: Analyzing a @sc{mime} message.
+* Non-MIME:: Analyzing a non-@sc{mime} message.
+* Handles:: Handle manipulations.
+* Display:: Displaying handles.
+* Display Customization:: Variables that affect display.
+* New Viewers:: How to write your own viewers.
+@end menu
+
+
+@node Dissection
+@section Dissection
+
+The @code{mm-dissect-buffer} is the function responsible for dissecting
+a @sc{mime} article. If given a multipart message, it will recursively
+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-@sc{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
+
+A @sc{mime} handle is a list that fully describes a @sc{mime}
+component.
+
+The following macros can be used to access elements in a handle:
+
+@table @code
+@item mm-handle-buffer
+@findex mm-handle-buffer
+Return the buffer that holds the contents of the undecoded @sc{mime}
+part.
+
+@item mm-handle-type
+@findex mm-handle-type
+Return the parsed @code{Content-Type} of the part.
+
+@item mm-handle-encoding
+@findex mm-handle-encoding
+Return the @code{Content-Transfer-Encoding} of the part.
+
+@item mm-handle-undisplayer
+@findex mm-handle-undisplayer
+Return the object that can be used to remove the displayed part (if it
+has been displayed).
+
+@item mm-handle-set-undisplayer
+@findex mm-handle-set-undisplayer
+Set the undisplayer object.
+
+@item mm-handle-disposition
+@findex mm-handle-disposition
+Return the parsed @code{Content-Disposition} of the part.
+
+@item mm-handle-disposition
+@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
+
+
+@node Display
+@section Display
+
+Functions for displaying, removing and saving.
+
+@table @code
+@item mm-display-part
+@findex mm-display-part
+Display the part.
+
+@item mm-remove-part
+@findex mm-remove-part
+Remove the part (if it has been displayed).
+
+@item mm-inlinable-p
+@findex mm-inlinable-p
+Say whether a @sc{mime} type can be displayed inline.
+
+@item mm-automatic-display-p
+@findex mm-automatic-display-p
+Say whether a @sc{mime} type should be displayed automatically.
+
+@item mm-destroy-part
+@findex mm-destroy-part
+Free all resources occupied by a part.
+
+@item mm-save-part
+@findex mm-save-part
+Offer to save the part in a file.
+
+@item mm-pipe-part
+@findex mm-pipe-part
+Offer to pipe the part to some process.
+
+@item mm-interactively-view-part
+@findex mm-interactively-view-part
+Prompt for a mailcap method to use to view the part.
+
+@end table
+
+
+@node Display Customization
+@section Display Customization
+
+@table @code
+
+@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.
+
+@item mm-inline-text-html-renderer
+This selects the function used to render @sc{html}. The predefined
+renderers are selected by the symbols @code{w3},
+@code{w3m}@footnote{See @uref{http://emacs-w3m.namazu.org/} for more
+information about emacs-w3m}, @code{links}, @code{lynx} or
+@code{html2text}. You can also specify a function, which will be
+called with a @sc{mime} handle as the argument.
+
+@item mm-inline-text-html-with-images
+Some @sc{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}.@footnote{The command @kbd{T} will load all images. If you
+have set the option @code{w3m-key-binding} to @code{info}, use @kbd{i}
+or @kbd{I} instead.}
+
+@item mm-inline-text-html-with-w3m-keymap
+You can use emacs-w3m command keys in the inlined text/html part by
+setting this option to non-@code{nil}. The default value is @code{t}.
+
+@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.
+* Encoding Customization:: Variables that affect encoding.
+* Charset Translation:: How charsets are mapped from @sc{mule} to @sc{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}). @xref{Charset Translation}.
+
+@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}). @xref{Charset
+Translation}.
+
+@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 Encoding Customization
+@section Encoding Customization
+
+@table @code
+
+@item mm-body-charset-encoding-alist
+@vindex mm-body-charset-encoding-alist
+Mapping from MIME charset to encoding to use. This variable is
+usually used except, e.g., when other requirements force a specific
+encoding (digitally signed messages require 7bit encodings). The
+default is @code{((iso-2022-jp . 7bit) (iso-2022-jp-2 . 7bit))}. As
+an example, if you do not want to have ISO-8859-1 characters
+quoted-printable encoded, you may add @code{(iso-8859-1 . 8bit)} to
+this variable. You can override this setting on a per-message basis
+by using the @code{encoding} MML tag (@pxref{MML Definition}).
+
+@item mm-coding-system-priorities
+@vindex mm-coding-system-priorities
+Prioritize coding systems to use for outgoing messages. The default
+is nil, which means to use the defaults in Emacs. It is a list of
+coding system symbols (aliases of coding systems does not work, use
+@kbd{M-x describe-coding-system} to make sure you are not specifying
+an alias in this variable). For example, if you have configured Emacs
+to use prefer UTF-8, but wish that outgoing messages should be sent in
+ISO-8859-1 if possible, you can set this variable to
+@code{(iso-latin-1)}. You can override this setting on a per-message
+basis by using the @code{charset} MML tag (@pxref{MML Definition}).
+
+@item mm-content-transfer-encoding-defaults
+@vindex mm-content-transfer-encoding-defaults
+Mapping from MIME types to encoding to use. This variable is usually
+used except, e.g., when other requirements force a safer encoding
+(digitally signed messages require 7bit encoding). Besides the normal
+MIME encodings, @code{qp-or-base64} may be used to indicate that for
+each case the most efficient of quoted-printable and base64 should be
+used. You can override this setting on a per-message basis by using
+the @code{encoding} MML tag (@pxref{MML Definition}).
+
+@item mm-use-ultra-safe-encoding
+@vindex mm-use-ultra-safe-encoding
+When this is non-nil, it means that textual parts are encoded as
+quoted-printable if they contain lines longer than 76 characters or
+starting with "From " in the body. Non-7bit encodings (8bit, binary)
+are generally disallowed. This reduce the probability that a non-8bit
+clean MTA or MDA changes the message. This should never be set
+directly, but bound by other functions when necessary (e.g., when
+encoding messages that are to be digitally signed).
+
+@end table
+
+@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.
+
+When running Emacs with @sc{mule} support, the preferences for which
+coding system to use is inherited from Emacs itself. This means that
+if Emacs is set up to prefer UTF-8, it will be used when encoding
+messages. You can modify this by altering the
+@code{mm-coding-system-priorities} variable though (@pxref{Encoding
+Customization}).
+
+The charset to be used can be overriden by setting the @code{charset}
+MML tag (@pxref{MML Definition}) when composing the message.
+
+The encoding of characters (quoted-printable, 8bit etc) is orthogonal
+to the discussion here, and is controlled by the variables
+@code{mm-body-charset-encoding-alist} and
+@code{mm-content-transfer-encoding-defaults} (@pxref{Encoding
+Customization}).
+
+@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 Interface Functions
@chapter Interface Functions
@cindex interface functions
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 (@file{rfc2047.el}, @file{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
-@code{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 Emacs @sc{mime} library takes a different tack. It defines a
+series of low-level libraries (@file{rfc2047.el}, @file{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 @code{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:
@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.
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)")
-@result{} "Finnish Landrace"
+@result{} "Finnish Landrace"
@end example
@item mail-header-parse-address
@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
Encode the non-ASCII words in the region. For instance,
-@samp{Na\e$B}W\e(Be} is encoded as @samp{=?iso-8859-1?q?Na=EFve?=}.
+@samp{Naïve} is encoded as @samp{=?iso-8859-1?q?Na=EFve?=}.
@item mail-encode-encoded-word-buffer
@findex mail-encode-encoded-word-buffer
@example
(mail-encode-encoded-word-string
- "This is na\e$B}W\e(Be, baby")
+ "This is naïve, baby")
@result{} "This is =?iso-8859-1?q?na=EFve,?= baby"
@end example
@example
(mail-decode-encoded-word-string
"This is =?iso-8859-1?q?na=EFve,?= baby")
-@result{} "This is na\e$B}W\e(Be, baby"
+@result{} "This is naïve, baby"
@end example
@end table
Currently, @code{mail-parse} is an abstraction over @code{ietf-drums},
-@code{rfc2047} and @code{rfc2231}. These are documented in the
-subsequent sections.
+@code{rfc2047}, @code{rfc2045} and @code{rfc2231}. These are documented
+in the subsequent sections.
(@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.
@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
@section 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!\"")
@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
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
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")
(seconds-to-time 905595714.0)
@result{} (13818 19266 0)
-(time-to-day '(13818 19266))
+(time-to-days '(13818 19266))
@result{} 729644
(days-to-time 729644)
(time-to-day-in-year '(13818 19266))
@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
@example
image/*; gimp -8 %s
audio/wav; wavplayer %s
+application/msword; catdoc %s ; copiousoutput ; nametemplate=%s.doc
@end example
-This says that all image files should be displayed with @samp{xv}, and
-that realaudio files should be played by @samp{rvplayer}.
+This says that all image files should be displayed with @code{gimp},
+that WAVE audio files should be played by @code{wavplayer}, and that
+MS-WORD files should be inlined by @code{catdoc}.
The @code{mailcap} library parses this file, and provides functions for
matching types.
-@node Decoding and Viewing
-@chapter Decoding and Viewing
-
-This chapter deals with decoding and viewing @sc{mime} messages on a
-higher level.
-
-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 analysis.
-
-@menu
-* Dissection:: Analyzing a @sc{mime} message.
-* Handles:: Handle manipulations.
-* Display:: Displaying handles.
-@end menu
-
-
-@node Dissection
-@section Dissection
-
-The @code{mm-dissect-buffer} is the function responsible for dissecting
-a @sc{mime} article. If given a multipart message, it will recursively
-descend the message, following the structure, and return a tree of
-@sc{mime} handles that describes the structure of the message.
-
-
-@node Handles
-@section Handles
-
-A @sc{mime} handle is a list that fully describes a @sc{mime}
-component.
-
-The following macros can be used to access elements in a handle:
-
-@table @code
-@item mm-handle-buffer
-@findex mm-handle-buffer
-Return the buffer that holds the contents of the undecoded @sc{mime}
-part.
-
-@item mm-handle-type
-@findex mm-handle-type
-Return the parsed @code{Content-Type} of the part.
-
-@item mm-handle-encoding
-@findex mm-handle-encoding
-Return the @code{Content-Transfer-Encoding} of the part.
-
-@item mm-handle-undisplayer
-@findex mm-handle-undisplayer
-Return the object that can be used to remove the displayed part (if it
-has been displayed).
-
-@item mm-handle-set-undisplayer
-@findex mm-handle-set-undisplayer
-Set the undisplayer object.
-
-@item mm-handle-disposition
-@findex mm-handle-disposition
-Return the parsed @code{Content-Disposition} of the part.
-
-@item mm-handle-disposition
-@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
-
-
-@node Display
-@section Display
-
-Functions for displaying, removing and saving.
-
-@table @code
-@item mm-display-part
-@findex mm-display-part
-Display the part.
-
-@item mm-remove-part
-@findex mm-remove-part
-Remove the part (if it has been displayed).
-
-@item mm-inlinable-p
-@findex mm-inlinable-p
-Say whether a @sc{mime} type can be displayed inline.
-
-@item mm-automatic-display-p
-@findex mm-automatic-display-p
-Say whether a @sc{mime} type should be displayed automatically.
-
-@item mm-destroy-part
-@findex mm-destroy-part
-Free all resources occupied by a part.
-
-@item mm-save-part
-@findex mm-save-part
-Offer to save the part in a file.
-
-@item mm-pipe-part
-@findex mm-pipe-part
-Offer to pipe the part to some process.
-
-@item mm-interactively-view-part
-@findex mm-interactively-view-part
-Prompt for a mailcap method to use to view the part.
-
-@end table
-
-
@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 @samp{http://www.stud.ifi.uio.no/~larsi/notes/}.
+fetched from @uref{http://quimby.gnus.org/notes/}.
@table @dfn
@item RFC822
Conformance Criteria and Examples
@item RFC2231
-MIME Parameter Value and Encoded Word Extensions: Character Sets,
+@sc{mime} Parameter Value and Encoded Word Extensions: Character Sets,
Languages, and Continuations
@item RFC1843
@item draft-ietf-drums-msg-fmt-05.txt
Draft for the successor of RFC822
+@item RFC2112
+The @sc{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
@printindex cp
@contents
@bye
+\f
+@c Local Variables:
+@c mode: texinfo
+@c coding: iso-8859-1
@c End:
projects / elisp / gnus.git- / blobdiff