This file documents the Emacs MIME interface functionality.
-Copyright (C) 1996 Free Software Foundation, Inc.
+Copyright (C) 1998,99 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
@page
@vskip 0pt plus 1filll
-Copyright @copyright{} 1998 Free Software Foundation, Inc.
+Copyright @copyright{} 1998,99 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
* 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
@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
@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
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.
+* Handles:: Handle manipulations.
+* Display:: Displaying handles.
+* Customization:: Variables that affect display.
+* New Viewers:: How to write your own viewers.
@end menu
Prompt for a mailcap method to use to view the part.
@end table
-
+
+
+@node Customization
+@section 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,
+then the value of this variable should be set to:
+
+@lisp
+("text/html" "text/richtext")
+@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.
+
+
+@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.
+* Conversion:: Going from @sc{mime} to MML and vice versa.
+@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 size
+The size (in octets) of the part (@code{Content-Disposition}).
+
+@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
+
+
+@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 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 Standards
@chapter Standards
@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
+
@end table
-
-
+
+
@node Index
@chapter Index
@printindex cp
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