This file documents the Emacs-w3 World Wide Web browser.

Copyright (C) 1993, 1994, 1995 William M. Perry

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.

This manual documents the Emacs-w3 World Wide Web browser, a Lisp program which runs as a subsystem under Emacs.  The manual is divided into the following chapters.

Introduction
************

Emacs-w3 is an Emacs subsystem that allows the user to browse the wonderful World Wide Web.

The World Wide Web was started at the CERN physics institute in Switzerland in 1991.  The project was initially started by Tim Berners-Lee (timbl@w3.org) for distributing data between different research groups effectively.

The Web has since grown into the most advanced information system currently on the internet.  It is now a global hypertext system with servers and browsers (programs written to interpret the hypertext language and display it correctly, and allow the user to follow links) exist for all major platforms (VMS, Windows, DOS, Unix, VM, NeXTstep, Amiga, and Macintosh).

The basic concepts used in the Web are hypertext and hypermedia. Hypertext is the same as regular text, with one exception---it can contain links (cross-references) to other textual documents.  Hypermedia is slightly different---it can contain links to other forms of media (movies, sounds, interactive programs, etc.).

WWW also allows searches of indices that are located anywhere on the network; in this respect, it mirrors certain capabilities found in both WAIS and Gopher.
----------------
CLIENT SIDE VIEW
----------------
The WWW world consists of documents and links.  Indexes are special documents which, rather than being read, may be searched.  The result of such a search is another virtual document containing links to the documents found.  A simple protocol, HTTP is used to allow a browser program to request a keyword search by a remote information server.

The web contains documents in many formats.  Those documents which are hypertext, (real or virtual) contain links to other documents, or places within documents.  All documents, whether real, virtual or indexes, look similar to the reader and are contained within the same addressing scheme.
-------------------------
INFORMATION PROVIDER VIEW
-------------------------
WWW browsers can access many existing data systems via existing protocols (FTP, NNTP) or via HTTP and a gateway.  In this way, the critical mass of data is quickly exceeded, and the increasing use of the system by readers and information suppliers encourage each other.

Providing information is as simple as running the WWW server and pointing it at an existing directory structure.  The server automatically generates the a hypertext view of the files to guide the user around.

To personalize it, a few SGML hypertext files can be written to give an even more friendly view.  Also, any file available by anonymous FTP, or any internet newsgroup can be immediately linked into the web.  The very small start-up effort is designed to allow small contributions.  At the other end of the scale, large information providers may provide an HTTP server with full text or keyword indexing.  This may allow access to a large existing database without changing the way that database is managed.  Such gateways have already been made into Oracle(tm), WAIS, and Digital's VMS/Help systems, to name but a few.

The WWW model gets over the frustrating incompatibilities of data format between suppliers and reader by allowing negotiation of format between a smart browser and a smart server.  This should provide a basis for extension into multimedia, and allow those who share application standards to make full use of them across the web.

Here is some more specific information about what Emacs-w3 does and does not understand:

Supported Markup Languages
**************************

Several different markup languages, and various extensions to those languages, are supported by Emacs-w3.
----------
HTML 2.0
----------
HTML is composed of a set of elements that define a document and guide its display.  An HTML element may include a name, some attributes and some text or hypertext, and appears in an HTML document as <tag_name>text</tag_name>, <tag_name attribute_name=argument>text</tag_name>, or just <tag_name>.

For example: <title> My Useful Document </title>, and <pre width=60> A lot of text here.  </pre>.

An HTML document is composed of a single element: <html>...</html>, that is, in turn, composed of head and body elements: <head>...</head>, and <body>...</body>.  To allow older HTML documents to remain readable, <html>, <head>, and <body> are actually optional within HTML documents.

All the tags and attributes of HTML are fully supported in Emacs-w3.

The full HTML 2.0 specification is available via the web at http://www.hal.com/users/connolly/html-spec/HTML_TOC.html, or via anonymous ftp to www.ics.uci.edu:/pub/ietf/html/.

----------
HTML 3.0
----------
The HTML 3.0 language is an extension of HTML, with a large degree of backwards compatibility with HTML 2.0.  The latest revision of HTML 3.0 can be retrieved via anonymous ftp to ftp.w3.org, the file is /www/arena/html3-dtd.txt.  The following HTML 3.0 language elements are supported by Emacs-w3:

  * ID tags for headers and paragraphs.  This makes it possible to reference points within a document and not require empty hypertext links to do it.

  * Named BASE tags.  Base tags allow you to specify how relative links within a document should be resolved (typically with a different URL than that which was used to retrieve the file).  This is useful if you want to store the file on disk, but still have the links work correctly.

     HTML 3.0 extends the power of the BASE tag by allowing multiple BASE tags in a single document, each with a NAME or ID attribute.  Any other tag required either the HREF or SRC attribute can also have the BASE attribute.  If this matches the NAME/ID of a BASE tag, then that URL is used as the basis for resolving the relative link.  If no base tag matches the, a base tag with no NAME/ID is used.  If no such base tag exists, the URL of the document is used.

  * Text alignment.  Most tags that cause a line break (BR, H?, P, etc) can now take an optional ALIGN attribute, which specifies how the text enclosed within it is to be aligned.  Valid alignments are:

     left
          The default alignment, causes text to be flush left, with a ragged right edge.

     right
          Causes text to be flush right, with a ragged left margin.

     center
          Causes text to be centered between the left and right margins (this can be affected by list indentation, blockquotes, and a few other tags).

     justify
          Causes text to be fully justified (both right and left margins smooth).

     indent
          Causes text to be indented from the left margin.

  * Limited font selection.  Using the <big> and <small> tags, HTML 3.0 gives the user some control over font size without the overhead of a stylesheet.See Style Sheets

  * Subscripts and superscripts.  The <sub> and <sup> tags allow you to have limited math markup anywhere in your document.

  * More powerful inlined images.  With the <fig> tag, you now have much more control over inlined image formatting.  Chief among them in usefulness for Emacs-w3 users is the ability to put the old <img> tag's alt text before the </fig> element, and the ability to include markup in it.  For example: <fig ismap src="fancyhrule.gif"><hr></fig>, so that the user with inlined images turned off will get the same effect.

  * Better control over list formatting.  For odered (<OL>) lists, you can now specify the type of numbering to use.  With the new 'type' attribute, you can specify arabic, alphabetical, or roman numbering, in either upper or lowercase.  Also, the optional 'start' attribute lets you specify the starting list item number.

     For unordered lists (<UL>), you can specify that the browser should not insert any bullets on list items by using the new PLAIN attribute.

  * More form widgets.  New input types include RANGE, FILE, images, and named submit and reset buttons.

  * LINK support.  LINKs allow the author to specify the relevance between documents easily.  This makes it possible to point to dictionaries, glossaries, abd indices, or to specify the author of a document.

  * Annotations.  Can have <footnote> and <margin> notes that show up as footnotes at the bottom of a document.

  * Notes and admonishments.  The NOTE tag provides a way to specify a warning or other standard information.  Shows appropriate bitmap if possible.  Similar to warning dialogs in Windows/Macintosh.  Syntax is <note role=simple|note|caution|warning>A note for the user</note>.  The default role is 'simple'.

  * Infinitely nested lists, and use of paragraphs and headers within lists.

----------
Netscape-HTML
----------
I hate to say it, but I broke down and actually included some of the netscape extensions into Emacs-w3.

<font>...</font>
     You can change the font size.  Valid values range from 0-7. The default font size is 3. The value given can optionally have a '+' or '-' character in front of it to specify that it is relative to the document basefont.

<center>...</center>
     This ugly, ill-thought-out alternative to the HTML 3.0 align attribute on headers and paragraphs was included for compatibility, and as an example of how not to do things.

<isindex>
     The isindex tag can now take a prompt attribute, to get rid of the default 'This is a searchable index' label.

<hr width=xx align=xx>
     You can now control the width of a horizontal rule, in relation to the total window size.  The WIDTH attribute specifies how wide the rule should be, as a percentage of the window width.

     The ALIGN attribute specifies where the horizontal rule is placed. Valid values are left, right, center, and indent.

<body background=URL bgcolor=RGB TEXT=RGB LINK=RGB VLINK=RGB>
     You can specify various colors and formatting issues on a document wide basis.  This is done with various attributes on the BODY tag. Stylesheets are really a better way to do this, and are recommended. This is just for compatibility.  See Style Sheets

     BACKGROUND=URL
          Specifies a graphic to tile in the background of the document.  This only works in XEmacs 19.12.

     BGCOLOR=COLOR
          Specifies the background of the document, as a color instead of a graphic.  COLOR should be either an RGB specification (like "#FF00BB"), or a logical color name (like "PaleGoldenrod").  The logical color names supported are system dependent.

     TEXT=COLOR
          Specifies the color of text on the page.  COLOR should be either an RGB specification (like "#FF00BB"), or a logical color name (like "PaleGoldenrod").  The logical color names supported are system dependent.

     LINK=COLOR
          Specifies the color of hypertext links on the page.  COLOR should be either an RGB specification (like "#FF00BB"), or a logical color name (like "PaleGoldenrod").  The logical color names supported are system dependent.

     VLINK=COLOR
          Specifies the color of hypertext links that have been visited already. COLOR should be either an RGB specification (like "#FF00BB"), or a logical color name (like "PaleGoldenrod").  The logical color names supported are system dependent.

----------
Extras
----------
There are several different markup elements that are not officially part of HTML or HTML 3.0 that Emacs-w3 supports.  These are either items that were dropped from HTML 3.0 after I had implemented them, or experimental parts of HTML that should not be counted as "official" or long lived.

  * More <HR> improvements.  You can add text into a horizontal rule by using the LABEL and TEXTALIGN attributes.

          <hr label="testing" textalign="right">
          yields
          ----------------------------------------------------------testing-

          <hr label="testing" textalign="center">
          yields
          -----------------------------testing------------------------------

          <hr label="testing" textalign="left">
          yields
          -Testing----------------------------------------------------------

  * Entity definitions within documents.  This allows the author of an HTML page to define per-document macros.  Syntax is <!ENTITY TAG "Expansion of Tag">, which replaces all occurences of &TAG; with Expansion of Tag.

  * Embedding of arbitrary objects into an HTML document.  With the <embed> tag, you can insert any document, or image.  The most entertaining use of this is with embedding MPEG movies into an emacs buffer.  This requires Lucid Emacs 19.10, or XEmacs 19.11, as well as a slightly patched version of mpeg_play 2.0 (the patch is available from ftp.cs.indiana.edu:/pub/elisp/w3/mpeg_patch).

  * FLAME support.  For truly interesting dynamic documents.  This is replaced with a random quote from Mr. Angry (see M-x flame for a sample).

  * The top ten tags that did not make it into netscape.  These tags were posted to the newsgroup comp.infosystems.www.misc by Laura Lemay (lemay@netcom.com).  Much thanks to her for the humor.

     <wired>...</wired>
          Renders the enclosed text in a suitably ugly font/color combination.  If no default has been set up by the user, this is the default font, with red text on a yellow background.

     <roach>...</roach>
          When selected, the enclosed text runs and hides under the nearest window.  OR, giggles a lot and demands nachos, depending on your definition of "roach." (the formal definition, of course, to be determined by the Official Honorary Internet Standards Committee For Moving Really Slowly.)

     <kill_sgml>

          Should anyone foolish enough to think that HTML is still SGML and try and run a netscape-html document through an SGML editor, processor, or other tool, this tag causes an immediate core dump, erases anything on your disk with "DTD" in the name, and emails a randomly-selected insult to Tim Pierce.

          Emacs-w3 just inserts a rude comment.

     <pinhead>
          Inserts "zippyisms" into the enclosed text.  Perfect for those professional documents.  This is sure to be a favorite of mine!

     <secret>...</secret>
          In order to read the enclosed text, you have to have secret spy decoder glasses (available direct from Mcom for a reasonable fee).  You can also read it by holding your computer in front of a full moon during the autumn solstice.

          In Emacs-w3, this displays the text using rot13 encoding.

     <hype>
          Causes Marc Andreesen to magically appear and grant you an interview (whether you want one or not).  Please use this tag sparingly.

     <peek>....</peek>

     <poke>...</poke>
          So you want more control over screen layout in HTML?  Well, here ya go.

          Actually, <peek> could almost be considered useful.  The VARIABLE attribute can be used to insert the value of an emacs variable into the current document.  Things like 'Welcome to my page, <peek variable=user-mail-address>' can be useful in freaking people out.

     <yogsothoth>
          Summons the elder gods to suck away your immortal soul.  Or Bill Gates, if the elder gods are busy.  Unpredictable (but amusing) results occur when the <YOGSOTHOTH> and <HYPE> tags are used in close proximity.

     <blink>...</blink>
          Causes the enclosed text to .... ooops that one made it in.

Supported Protocols
*******************

Emacs-w3 supports the following protocols

Usenet News
     Can either display an entire newsgroup or specific articles by Message-ID: header.  This supports a unix-style .newsrc file, so the user does not see articles they have read using another newsreader, but due to how news URLs work, Emacs-w3 cannot update the users .newsrc after they have read news.

     To be more in line with the other URL schemes, Emacs-w3 lets you specify the hostname and port of an NNTP server in a news URL.  URLs of the form news://hostname:port/messageID work, but will not work in the majority of other browsers (yet).

HTTP
     Supports both the HTTP/0.9 and HTTP/1.0 protocols.  Fully MIME-compliant with regards to HTTP/1.0. See HTTP/1.0 Support

Gopher
     Support for all gopher types, include CSO queries.

Gopher+
     Support for Gopher+ retrievals. Support for converting ASK blocks into HTML 3.0 FORMS and submitting them back to the server.

FTP
     FTP is handled by either ange-ftp or efs, the choice is up to the individual user.

Local files
     Local files are handled, and MIME content-types are derived from the file extensions.

Telnet
     Telnet is handled by running the Emacs Lisp function telnet, or spawning an xterm running telnet.

TN3270
     TN3270 is handled by running a tn3270 program in an Emacs buffer, or spawning an xterm running tn3270.

Mailto
     Causes a mail message to be started to a specific address.

mailserver
     A more powerful version of mailto, which allows the author to specify the subject and body text of the mail message.  This type of link is never fully executed without user confirmation, because it is possible to insert insulting or threatening (and possibly illegal) data into the message.  The mail message is displayed, and the user must type 'yes' to send it.

X-exec
     A URL can cause a local executable to be run, and its output interpreted as if it had come from an HTTP server.  This is very useful, but is still an experimental protocol, hence the X- prefix.

SSL
     SSL requires a set of patches to the Emacs C code and SSLRef 2.0, or an external program to run in a subprocess (similar to the tcp.el package that comes with GNUS.  See SSL

Secure HTTP
     Work is in progress to add support for the Secure HTTP specification from Enterprise Information Technologies.  The specification for SHTTP can be found on EIT's web server at http://www.commerce.net/information/standards/drafts/shttp.txt.

Setting Up
**********

This section of the manual deals with getting, compiling, and configuring Emacs-w3.

Retrieving Emacs-w3
===================

If using Lucid Emacs 19.9 or later, skip to the section on starting Emacs-w3.  Emacs-w3 comes standard with all versions of Lucid Emacs from 19.9 onwards.

Three files are required when first installing Emacs-w3.  All of them can be found via anonymous ftp to ftp.cs.indiana.edu:/pub/elisp/w3.  The files are w3-XXX.tar.gz, where XXX is the version number of Emacs-w3 being retrieved, icons.tar.gz, which contains approximately 50 small icons that Emacs-w3 requires, and are available to HTML authors.  The extras.tar.gz file contains ange-ftp, html-mode, and nntp.

After retrieving the files, unpack them with the following commands: zcat w3-XXX.tar.gz | tar xvvf -, zcat icons.tar.gz | tar xvvf -, and zcat extras.tar.gz | tar xvvf -.  This unpacks the distribution into three subdirectories w3, icons, and extras.  To compile and install all the packages in the extras directory, please see the comments at the top of each lisp file.

Compiling Emacs-w3
==================

To install Emacs-w3, go into the w3 subdirectory and edit the Makefile.  These variables might need to be changed:

EMACS
     This variable controls what version of Emacs is used to compile the programs.  It should be the full path to the Emacs executable on the system.  The default is to use GNU Emacs (emacs).

LISPDIR
     This variable controls where the lisp code is copied to when it is installed (with make install).  This is usually the users personal lisp code directory (I prefer ~/lisp).  The value is run through expand-file-name and then added to the load-path.

DOTEMACS
     This variable points to the Emacs customization file, usually ~/.emacs.

INFODIR
     This variable points to the local info directory (usually /usr/local/info).  This can be any valid directory, as long as it is in Info-default-directory-list so that info-mode can find it.

MAKEINFO
     This variables controls how the info files are built.  Possible values are makeinfo or emacs -batch -q -f batch-texinfo-format.

Once the Makefile has been modified, several different targets can be built.

make w3
     This compiles all the .el files into the much faster .elc files.  If Jamie Zawinski's optimizing byte compiler (standard in GNU Emacs 19 and Lucid Emacs) is used, then a few compilation warnings are displayed (not many hopefully).  These can be safely ignored as long as everything finishes compiling.  This is the default target for make with no arguments.

make install
     Compiles all the .el files and copies .el and .elc files into the directory specified by LISPDIR.

make emacs
     Modifies the file specified by DOTEMACS.  A statement modifying the load-path variable and several autoload statements are added to the end of the file.

make all
     Compiles and installs the .el files, and also modify/create the DOTEMACS file.

make w3.info
     Creates the Emacs-readable info files.  The info files are created in the directory specified by INFODIR.  The makefile variable MAKEINFO determines how the info file is built.

make w3.dvi
     Creates the printable documentation, using tex and texindex to properly generate the indices.  A w3.dvi file is left in the current directory.

Basic Setup
===========

There are a few variables that almost all people need to change.

url-bad-port-list
     List of ports to warn the user about connecting to.  Defaults to just the mail and NNTP ports so a malicious HTML author cannot spoof mail or news to other people.

url-be-asynchronous
     Controls whether document retrievals over HTTP should be done in the background.  This allows emacs to keep working in other windows while large downloads occur.  Defaults to nil.  This variable is buffer-local, so use setq-default after loading Emacs-w3 to globally modify it, or set it in your ~/.emacs file.

url-confirmation-func
     What function to use for asking yes or no functions.  Possible values are 'yes-or-no-p or 'y-or-n-p, or any function that takes a single argument (the prompt), and returns t only if a positive answer is gotten.  Defaults to 'yes-or-no-p.

w3-default-action
     A lisp symbol specifying what action to take for files with extensions that are not in the mm-mime-extensions assoc list.  This is useful in case Emacs-w3 ever run across files with weird extensions (.foo, .README, .READMEFIRST, etc.).  In most circumstances, this should not be required anymore.

     Possible values: any lisp symbol.  Should be a function that takes no arguments.  The return value does not matter, it is ignored.  Some examples are 'w3-prepare-buffer or 'indented-text-mode.

w3-default-homepage
     The url to open at startup.  It can be any valid URL.  This defaults to the environment variable WWW_HOME if it is not set it in the users .emacs file. If WWW_HOME is undefined, then it defaults to the hypertext documentation for Emacs-w3 at Indiana University.

w3-delay-image-loads
     Controls the loading of inlined images.  If non-nil, images are not loaded.  For slow network connections, this is usually set to t.  Defaults to nil.

w3-delimit-emphasis
     Whether to use characters at the start and end of each bold/italic region.  Types of characters are specified in w3-style-tags-assoc.  w3-style-tags-assoc is an assoc list of style names, the cdr of each is a cons cell.  The car of this cell is the string to insert at the beginning of the emphasis, and the cdr is the string to insert at the end of the emphasis.  The default value is a good example.

          (
           (b       "*"  . "*")
           (address "*"  . "*")
           (byline  "_"  . "_")
           (cite    "_"  . "_")
           (cmd     "*"  . "*")
           (dfn     "*"  . "*")
           (em      "~"  . "~")
           (i       "~"  . "~")
           (q       "\"" . "\"")
           (removed ""   . "")
           (s       ""   . "")
           (strong  "*"  . "*")
           (sub     ""   . "")
           (sup     ""   . "")
           (u       "_"  . "_")
          )

w3-delimit-links
     Controls how hypertext links are displayed.  If this variable is eq to 'linkname, then the link NAME or ID of the link is inserted after the link text.  If nil, then nothing is done.  If it is non-nil and not eq to 'linkname, then [[ & ]] is inserted around the entire text of the link.  Is initially set to be t iff in normal Emacs, nil if in Epoch or Lucid Emacs, since links should be in different colors/fonts.

url-global-history-file
     The global history file used by both Mosaic/X and Emacs-w3.  This file contains a list of all the URLs that have been visited.  This file is parsed at startup and used to provide URL completion.  Emacs-w3 can read and write Mosaic/X or Netscape/X style history files, or use its own internal format (faster).  The file type is determined automatically, or prompted for if the file does not exist.

w3-hotlist-file
     Hotlist filename.  This should be the name of a file that is stored in NCSA's Mosaic/X or Netscape's format.  It is used to keep a listing of commonly accessed URL's without having to go through 20 levels of menus to get to them.

w3-personal-annotation-directory
     The directory where Emacs-w3 looks for personal annotations.  This is a directory that should hold the personal annotations stored in a Mosaic-compatible format. (ncsa-mosaic-personal-annotation-log-format-1)

url-pgp/pem-entity
     The name by which the user is known to PGP and/or PEM entities.  If this not set when w3-do-setup is run, it defaults to (user-real-login-name)@(system-name), which can often be wrong.

url-personal-mail-address
     Your full email address.  This is what is sent to HTTP/1.0 servers as the FROM field.  If this is not set when w3-do-setup is run, then it defaults to the value of url-pgp/pem-entity.

w3-right-border
     Amount of space to leave on right margin of WWW buffers.  This amount is subtracted from (window-width) for each new WWW buffer and used as the new fill-column.

w3-track-mouse
     Controls whether to track the mouse and message the url under the mouse. If this is non-nil, then a description of the hypertext area under the mouse is shown in the minibuffer.  This shows what type of link (inlined image, form entry area, delayed image, delayed MPEG, or hypertext reference) is under the cursor, and the destination.  This only works in Emacs-19, Lucid Emacs, or XEmacs.

w3-use-forms-index
     Non-nil means translate <ISINDEX> tags into a hypertext form.  A single text entry box is drawn where the ISINDEX tag appears.  If t, the isindex handling is the same as Mosaic for X.

url-use-hypertext-gopher
     Controls how gopher documents are retrieved.  If non-nil, the gopher pages are converted into HTML and parsed just like any other page.  If nil, the requests are passed off to the gopher.el package by Scott Snyder.  Using the gopher.el package loses the gopher+ support, and inlined searching.

url-wais-gateway-port
     The port # of the WAIS gateway to pass all wais:// requests to. See Native WAIS Support

url-wais-gateway-server
     The machine name where the WAIS gateway lives.  See Native WAIS Support

url-xterm-command
     Command used to start a windowed shell, similar to an xterm.  This string is passed through format, and should expect four strings: the title of the window, the program name to execute, and the server and port number.  The default is for xterm, which is very unix-centric, but is the most common case.

Firewalls
=========

There are several different reasons why you may need to use the gateway support in Emacs-w3.

 1. You are behind a firewall.  This is usually the case at large corporations with paranoid system-administrators.

 2. You are using TERM  (TERM is a user-level protocol for emulating IP over a serial line.  More information is available at sunsite.unc.edu:/pub/Linux/apps/comm/term) for slip-like access to the internet.

     NOTE: Emacs 19.22 has patches to enable native TERM networking, to enable it, #define TERM in the appropriate s/*.h file for your operating system, then change the SYSTEM_LIBS define to include the termnet library that comes with the latest versions of TERM.

 3. For some reason your version of Emacs can't resolve hostnames.  This happens quite often on Sun workstations and some ultrix machines.  Some C libraries do not include the hostname resolver routines in their static libraries.  If Emacs was linked statically, this means it won't be able to get to any machines off your local net.  This is characterized by being able to reach someplace with a raw ip number, but not its hostname (http://129.79.254.191/ works, but http://www.cs.indiana.edu/ doesn't).

     If for some reason your system administrator will not recompile Emacs with the -lresolv library or dynamic linking, you need to act as if you were behind a firewall.  Another alternative is to set the variable url-broken-resolution - this will use the support in ange-ftp or EFS to use nslookup in a subprocess to do all hostname resolving.  See the variables efs-nslookup-bprogram, efs-nslookup-on-connect, and efs-nslookup-threshold if you are using EFS, or ange-ftp-nslookup-program if you are using Ange-Ftp.

 4. You are running Lucid Emacs 19.x and Solaris 2.x (SunOS 5.x).  For some reason, network processes under Solaris and Lucid Emacs never get a status of exit or closed.  This causes retrieval of HTTP and gopher pages to hang indefinitely, with Emacs chewing up large amounts of your CPU time.

     NOTE: You do not need to use gateways anymore for this problem.

     With the release of Lucid Emacs 19.10, this problem is fixed if you #define FIX_SOLARIS_W3_BUG somewhere in your config.h or s/*.h configuration file.  This will be in the stock 19.11 release of XEmacs

Emacs-w3 has support for using the gateway mechanism for certain domains, and directly connecting to others.  To use this, you must change the value of url-gateway-local-host-regexp.  This should be a regular expression  (Please see the full Emacs distribution for a description of regular expressions) that matches local hosts that do not require the use of a gateway.  If nil, then all connections are made through the gateway.

Emacs-w3 supports several methods of getting around gateways.  The variable url-gateway-method controls which of these methods is used.  This variable can have several values (use these as symbol names, not strings):

program
     Run a program in a subprocess to connect to remote hosts (examples are itelnet (Itelnet is a standard name for a telnet executable that is capable of escaping the firewall.  Check with your system administrators to see if you have anything similar), an expect (Expect is a scripting language that allows you to control interactive programs (like telnet) very easily.  It is available from gatekeeper.dec.com:/pub/GNU/expect-3.24.0.tar.gz) script, etc.).

host
     This allows you to log into another local computer that has access to the internet, and run a telnet-like program from there.

tcp
     Masanobu UMEDA umerin@mse.kyutech.ac.jp has written a very nice replacement for the standard networking in Emacs.  This does basically the same thing that a method of program does, but is slightly more transparent to the user.

native
     This means that Emacs-w3 should use the builtin networking code of Emacs. This should be used only if there is no firewall, or someone at your site has already hacked the Emacs source to get around your firewall.

Two of these need a bit more explanation than that: If you are running a program in a subprocess to emulate a network connection, you need to set a few extra variables.  The variable url-gateway-telnet-program should point to an executable that accepts a hostname and port # as its arguments, and passes standard input to the remote host.  This can be either the full path to the executable or just the basename.  The variable url-gateway-telnet-ready-regexp controls how long Emacs-w3 should wait after spawning the subprocess to start sending to its standard input. This gets around a bug where telnet would miss the beginning of requests becausse it did not buffer its input before opening a connection.  This should be a regular expression to watch for that signifies the end of the setup of url-gateway-telnet-program.  The default should work fine for telnet.

If you are using the host-based gatway method, things get a bit more complicated.  This is basically my attempt to do some of the basic stuff of expect within elisp.  First off, set the variable url-gateway-host to be the name of your gateway machine.

The variable url-gateway-connect-program controls how the host is reached.  The easiest way is to have a program that does not require a username and password to allow you to login.  The most common of these is the rsh command.

If you do not have rsh, then things get very ugly.  First, set the variable url-gateway-program-interactive to non-nil.  Then you need to define the variables url-gateway-host-username and url-gateway-host-password to be the username and password necessary to log into the gateway machine.  The regular expressions in the variables url-gateway-handholding-login-regexp and url-gateway-handholding-password-regexp should match the login and password prompts on the gateway system respectively.  For example:

     (setq url-gateway-connect-program "telnet"
           url-gateway-host-program "telnet"
           url-gateway-program-interactive t
           url-gateway-host-username "wmperry"
           url-gateway-host-password "yeahrightkeepdreaming"
           url-gateway-host "moose.cs.indiana.edu"
           url-gateway-host-program-ready-regexp "Escape character is .*"
           url-gateway-handholding-login-regexp "ogin:"
           url-gateway-handholding-password-regexp "ord:")

This should take care of you logging into the remote system.  The variable url-gateway-host-prompt-pattern should contain a regular expression that matches the shell prompt on the remote machine.  This should appear no where in the login banner/setup, or things could get very confused.

Now you are ready to actually get off of your local network!  The variable url-gateway-host-program-ready-regexp should contain a regular expression that matches the end of the setup of url-gateway-host-program when it tries to make a connection to an off-firewall machine.  (Basically the same as url-gateway-telnet-ready-regexp.

Now you should be all set up to get outside your local network.  If none of this makes sense, its probably my fault.  Please check with your network administrators to see if they have a program that does most of this for you already, since somebody somewhere at your company has probably been through something similar to this before, and would be much more helpful/knowledgeable about your local setup than I would be. But feel free to mail me as a last resort.

Proxy Gateways
==============

In late January 1993, Kevin Altis and Lou Montulli proposed and implemented a new proxy service.  This service requires the use of environment variables to specify a gateway server/port # to send protocol requests to.  Each protocol (http, wais, gopher, ftp, etc.) can have a different gateway server.  The environment variables are PROTOCOL_proxy, where PROTOCOL is one of gopher, file, http, ftp, or wais.

The main thing to understand about the proxy gateway is that instead of a partial URL being sent to the HTTP server, which is what we do today when a client talks directly to an HTTP server, a client must send a full URL (http://..., gopher://..., ftp://...) to the proxy gateway server, the rest of the HTTP message is the same. For gopher and ftp, the proxy gateway server returns the data encapsulated as a MIME content type to the client like a normal HTTP message. HTTP MIME content types are returned for all URL requests, regardless of the protocol type of the URL. FTP directories, Gopher directories, etc. are returned as text/html.

Basic Usage
***********

Emacs-w3 is similar to the Info package all Emacs users hold near and dear to their hearts (see Info (The Info Manual), for a description of Info).  Basically, space and backspace control scrolling, and return or mouse2 follows a hypertext link.  The f and b keys maneuver around the various links on the page.

NOTE: To enter data into a form entry area, you must select it using return or mouse2 just like a hypertext link.

On non-graphic terminals (vt100, DOS, etc.), or with a graphics terminal and old versions (18.xx) of Emacs, hypertext links are surrounded by '[[' and ']]' by default.  On a graphics terminal with newer versions of Emacs (epoch, lucid, or FSF 19), the links are in bold print. See Controlling Formatting for information on how to change this, or for help on getting the highlighting to work on graphics terminals.

There are approximately 50 keys bound to special Emacs-w3 functions.  The basic rule of thumb regarding keybindings in Emacs-w3 is that a lowercase key takes an action on the current document, and an uppercase key takes an action on the document pointed to by the hypertext link under the cursor.

There are several areas that the keybindings fall into: movement, information, action, and miscellaneous.

Movement
========

SPC
     Scroll downward in the buffer.  With prefix arg, scroll down that many screenfuls.

DEL
     Scroll upward in the buffer.  With prefix arg, scroll up that many screenfuls.

<, M-x w3-start-of-document
     Go to start of document

>, M-x w3-end-of-document
     Go to end of document

Shift-TAB, b, M-x w3-back-link
     Attempts to move backward one link area in the current document. Signals an error if no previous links are found.

H, M-x w3-show-hotlist
     A hypertext listing of the items in the hotlist is generated on the fly, and the links can be followed normally.

h, M-x w3-use-hotlist
     Possibly go to a link in the hotlist.  A new buffer is created for the new document.

m, M-x w3-complete-link
     Choose a link from the current buffer and follow it.  A completing-read is done on all the links, so space and TAB can be used for completion.

TAB, f, n, M-x w3-forward-link
     Attempts to move forward one link area in the current document.  Signals an error if no more links are found.

Information
===========

These functions relate information about one or more links on the current document.

v, M-x url-view-url
     This shows the URL of the current document in the minibuffer.

V, M-x w3-view-this-url
     This shows the URL of the hypertext link under point in the minibuffer. If there is not a hypertext link under point, then it shows the type of form entry area under point.  If there is no form entry area under point, then it shows the inlined image's URL that is under point, if any.

i, M-x w3-document-information
     Shows miscellaneous information about the currently displayed document. This includes the URL, the last modified date, MIME headers, the HTTP response code, and the LINK tags found in the document (that describe relations between this and other documents).

I, M-x w3-document-information-this-url
     Shows information about the URL at point.  If it is an HTTP link, the HTTP/1.0 HEAD method is used to retrieve information, and this is what is displayed.  If it is a file or an ftp link, information about the file is shown, including whether it is a directory, who owns it, last access, modified, and changed times, the size, and the file type that Emacs-w3 thinks it is (text/plain, image/gif, etc).

s, M-x w3-source-document
     This shows the HTML source of the current document in a separate buffer. The buffer-name is based on the document's URL.

S, M-x w3-source-document-at-point
     Shows the HTML source of the hypertext link under point in a separate buffer.  The buffer-name is based on the document's URL.

k, C-k, M-x w3-save-url
     This stores the current document's URL in the kill ring, and also in the current window-system's clipboard, if possible.

K, M-x w3-save-this-url
     Stores the URL of the document under point in the kill ring, and also in the current window-system's clipboard, if possible.

Action
======

First, here are the keys and functions that bring up a new hypertext page, usually creating a new buffer.

return
     Pressing return when over a hyperlink attempts to follow the link under the cursor.  With a prefix argument (C-u), this forces the file to be saved to disk instead of being passed off to other viewers or being parsed as HTML.

     Pressing return when over a form input field will prompt in the minibuffer for the data to insert into the input field.  Type checking is done, and the data is only entered into the form when data of the correct type is entered (ie: you can't enter 44 for 'date' field, etc).

button2, M-x w3-follow-mouse
     This function expects to be bound to a mouse button.  It moves to the point under mouse and tries to fetch the link that was clicked on.  If no link is found, a message is displayed in the minibuffer.

     Pressing return when over a form input field will prompt in the minibuffer for the data to insert into the input field.  Type checking is done, and the data is only entered into the form when data of the correct type is entered (ie: you can't enter 44 for 'date' field, etc).

C-button2, M-return, M-x w3-follow-inlined-image
     This function tries to retrieve the inlined image that is under point. It ignores any form entry areas or hyperlinks, and blindly follows any inlined image.  Useful for seeing images that are meant to be used as hyperlinks when not on a terminal capable of displaying graphics.

p, M-x w3-print-this-url
     Prints out the current buffer in a variety of formats, including Postscript, HTML source, or formatted text.

P, M-x w3-print-url-under-point
     Prints out the URL under point in a variety of formats, including Postscript, HTML source, or formatted text.

m, M-x w3-complete-link
     Choose from a list of all the hyperlinks in the current buffer.  Use space and tab to complete on the links.

r, g, M-x w3-reload-document
     Reload the current document---the current buffer is killed, and the URL it was visiting is fetched and redisplayed.  The position within the buffer remains the same (unless the document has changed since it was last retrieved, in which case it should be relatively close).

C-o, M-x w3-fetch
     This function prompts for a URL in the minibuffer, and attempts to fetch it.  If there are any errors, or Emacs-w3 cannot understand the type of link requested, the errors are displayed in a hypertext buffer.

o, M-x w3-open-local
     Find a local file, interactively.  This prompts for a local file name to open.  The file must exist, and may be a directory.  If the requested file is a directory and url-use-hypertext-dired is nil, then a dired-mode buffer is displayed.  If nonnil, then Emacs-w3 automatically generates a hypertext listing of the directory. The hypertext mode is the default, so that all the keys and functions remain the same.

M-s, M-x w3-search
     Perform a search, if this is a searchable index.  This sends a string of the type 'URL?search-terms' to the server this document was retrieved from.  Searching requires a server - Emacs-w3 can not do local file searching, as there are too many possible types of searches people could want to do.  Generally, the only URL types that allow searching are HTTP, gopher, and X-EXEC.

C-c C-b, M-x w3-show-history-list
     If url-keep-history is non-nil, then Emacs-w3 keeps track of all the URLs visited in an Emacs session.  This function takes all the links that are in that internal list, and formats them as hypertext links in a list.

And here are the commands to move around between Emacs-w3 buffers:

l, M-x w3-goto-last-buffer
     Go to last WWW buffer visited

q, M-x w3-quit
     Quits WWW mode.  This kills the current buffer and goes to the most recently visited buffer.

u, M-x w3-leave-buffer
     This is similar to w3-quit, but the buffer is not killed, it is moved to the bottom of the buffer list (so it is the least likely to show up as the default with switch-to-buffer).  This is different from w3-goto-last-buffer in that it does not return to the last WWW page visited - it is the same as using switch-to-buffer - the buffer left in the window is fairly random.

B, M-x w3-backward-in-history
     Take one step back along the path in the current history.  Has no effect if at the beginning of the history list.

F, M-x w3-forward-in-history
     Take one step forward along the path in the current history.  Has no effect if at the end of the history list.

Miscellaneous
=============

M-m, M-x w3-mail-current-document
     Mails the current document to someone.  Choose from several different formats to mail: formatted text, HTML source, PostScript, or LaTeX source. When the HTML source is mailed, then an appropriate <base> tag is inserted at the beginning of the document so that relative links may be followed correctly by whoever receives the mail.

M-M, M-x w3-mail-document-under-point
     Mails the document pointed to by the hypertext link under point to someone. Choose from several different formats to mail: formatted text, HTML source, PostScript, or LaTeX source.  When the HTML source is mailed, then an appropriate <base> tag is inserted at the beginning of the document so that relative links may be followed correctly by whoever receives the mail.

p, M-x w3-print-this-url
     Prints the current document.  Choose from several different formats to print: formatted text, HTML source, PostScript (with ps-print), or by using LaTeX and dvips).

     When the formatted text is printed, the normal lpr-buffer function is called, and the variables lpr-command and lpr-switches control how the document is printed.

     When the HTML source is printed, then an appropriate <base> tag is inserted at the beginning of the document. When postscript is printed, then the HTML source of the document is converted into LaTeX source.  If the variable w3-use-html2latex is non-nil, then the program specified by w3-html2latex-prog is run in a subprocess with the arguments in w3-html2latex-args.  The w3-html2latex-prog must accept HTML source on its standard input and send the LaTeX output to standard output.  If w3-use-html2latex is nil, then an Emacs Lisp function uses regular expressions to replace the HTML code with LaTeX markup.  The variable w3-latex-docstyle controls how the document is laid out in this case, and postscript figures are printed as well.

P, M-x w3-print-url-under-point
     Prints the document pointed to by the hypertext link under point. Please see the documentation for w3-print-this-url directly above for more information.

M-x w3-insert-formatted-url
     Insert a fully formatted HTML link into another buffer.  This gets the name and URL of either the current buffer, or, with a prefix arg, of the link under point, and construct the appropriate <a...>...</a> markup and insert it into the desired buffer.

M-tab, M-x w3-insert-this-url
     Inserts the URL of the current document into another buffer.  Buffer is prompted for in the minibuffer.  With prefix arg, uses the URL of the link under point.

U, M-x w3-use-links
     Select one of the <LINK> tags from this document and fetch it.  Links are attributes of a specific document, and can tell such things as who made the document, where a table of contents is located, etc.

     Link tags specify relationships between documents in two ways.  Normal (forward) relationships (where the link has a REL="xxx" attribute), and reverse relationships (where the link has a REV="xxx" attribute).  This first asks what type of link to follow (Normal or Reverse), then does a completing-read on only the links that have that type of relationship.

Compatibility with Mosaic & Netscape
************************************

Since NCSA Mosaic for Xwindows or Netscape is the de-facto hypertext browser at most sites, Emacs-w3 is compatible with them in several ways.

Hotlist Handling
================

In order to avoid having to traverse many documents to get to the same document over and over, Emacs-w3 supports a ``hotlist'' like Mosaic.  This is a file that contains URLs and aliases.  Hotlists allow quick access to any document in the Web, providing it has been visited and added to the hotlist. The variable w3-hotlist-file determines where this information is saved.  The structure of the file is compatible with Mosaic's hotlist file, so this defaults to ~/.mosaic-hotlist-default.

Hotlist commands are:

M-x w3-import-netscape-bookmarks
     Converts a Netscape bookmark file into Emacs-w3's internal hotlist format.

a, M-x w3-hotlist-add-document
     This adds the current document to the hotlist, with the buffer name as its identifier.  Modifies the file specified by w3-hotlist-file. If this is given a PREFIX-ARGUMENT (via C-u), the title is prompted for instead of automatically defaulting to the buffer-name.

M-x w3-hotlist-refresh
     This rereads the default hostlist file specified by w3-hotlist-file.

d, M-x w3-hotlist-delete
     Prompts for the alias of the entry to kill.  Pressing the spacebar or tab will list out partial completions.  The internal representation of the hotlist and the file specified by w3-hotlist-file are updated.

M-x w3-hotlist-rename-entry
     Some hotlist item names can be very unwieldy (`Mosaic for X level 2 fill out form support'), or uninformative (`Index of /').  If you are not satisfied with how a specific item is labeled, you may change it by typing M-x w3-rename-hotlist-entry.  Prompts for the item to rename in the minibuffer---use the spacebar or tab key for completion. After having chosen an item to rename, prompts for a new title until a unique title is entered.  Modifies the file specified by w3-hotlist-file.

H, M-x w3-use-hotlist
     Prompts for the alias to jump to.  Pressing the spacebar or tab key shows partial completions.

M-x w3-show-hotlist
     This converts the hotlist into HTML and displays it.

History
=======

NCSA Mosaic keeps track of the URLs followed from a page, so that it can provide forward and back buttons to keep a path of URLs that can be traversed easily. If the variable url-keep-history is t, then Emacs-w3 keeps a list of all the URLs visited in a session. To view a listing of the history for this session of Emacs-w3, use M-x w3-show-history from any buffer, and Emacs-w3 generates an HTML document showing every URL visited since Emacs started (or cleared the history list), and then format it.  Any of the links can be chosen and followed to the original document.  To clear the history list, choose 'Clear History' from the 'Options' menu.

Another twist on the history list mechanism is the fact that all Emacs-w3 buffers remember what URL, buffer, and buffer position you were at before jumping to this document, and also keeps track of where you jump to from that buffer.  This means that you can go forwards and backwards very easily along the path you took to reach a particular document.  To go forward, use the function w3-forward-in-history, to go backward, use the function w3-backward-in-history.  These are fairly stable functions, but may not work as expected all the time. First, the buffer-list is used to look at the URL of every buffer, and if it matches the item in the history list you are looking for, then it is brought forward.  If no buffer containing the desired URL is found, then the URL is fetched.  Then the desired position in the buffer is searched for.

Global History
==============

Mosaic and Netscape supports the idea of a ``history'' of URLs the user has visited, and it displays them in a different style than normal URLs. If the variable url-keep-history is t, then Emacs-w3 keeps a list of all the URLs visited in a session.  The file is automatically written to disk when exiting emacs.  The list is added to those already in the file specified by url-global-history-file, which defaults to ~/.mosaic-global-history.

If any URL in the list is found in the file, it is not saved, but new ones are added at the end of the file.

The function that saves the global history list is smart enough to notice what style of history list you are using (Netscape or XMosaic), and writes out the new additions appropriately.

One of the nice things about keeping a global history files is that Emacs-w3 can use it as a completion table.  When doing M-x w3-fetch, pressing the tab or space keys will show all completions for a partial URL.  This is very useful, especially for very long URLs that are not in a hotlist, or for seeing all the pages from a particular web server before choosing which to retrieve.

Annotations
===========

Mosaic can annotate documents.  Annotations are comments about the current document, and these annotations appear as a link to the comments at the end of the document when you browse it in Mosaic. The original file is not changed. There are two types of annotations supported in Mosaic, and both are supported by Emacs-w3 as well.

Group Annotations
-----------------

NOTE: The group annotation experiment has been terminated.  It will be replaced with support on the server side for adding <LINK> tags to documents.

Personal Annotations
--------------------

If you do not want to share your musings about a particular document with the entire network, you can add a personal annotation that only you can see.  Personal annotations are stored in a subdirectory in the users account on the local disk, with a log file that contains information about what URLs have been annotated and which files contain the annotations.

Emacs-w3 looks in the directory specified by w3-personal-annotation-directory (defaults to ~/.mosaic-personal-annotations).  Any personal annotations for a document are automatically appended when it is retrieved.

To add a new personal annotation, type M-x w3-add-personal-annotation.  This creates a new buffer, in the mode specified by w3-annotation-mode.  This defaults to html-mode.  If this variable is nil, or it points to an undefined function, then default-major-mode is consulted.

A minor mode redefines C-c C-c to complete the annotation and store it on the local disk.

To delete a personal annotation, it must be the current page.  Once reading the annotation, M-x w3-delete-personal-annotation will remove it.  This deletes the file containing the annotation, and any references to it in the annotation log file.

Editing personal annotations is not yet supported.

Controlling Formatting
**********************

How Emacs-w3 formats a document is very customizable.  How a document is displayed depends on whether the user is on a terminal capable of graphics and a few variables.

The following sections describe in more detail how to change the formatting of a document.

General formatting conventions
==============================

--------------------
Setting the fill column
--------------------
Each time a document is parsed, the fill-column is recalculated using window-width and w3-right-border. w3-right-border is an integer specifying how much room at the right edge of the screen to leave blank.  The fill-column is set to (- (window-width) w3-right-border).
--------------------
Formatting of hypertext links
--------------------
If the variable w3-delimit-links is non-nil (the default for text-terminals), then hypertext links are surrounded by text specified by the user.  The variables w3-link-start-delimiter and w3-link-end-delimiter control what text is at the start and end of a hypertext link.  These variables are cons-pairs of two strings.

If a link has never been visited before (it is not in the global history), then the car of these variables is inserted at the start and end of the link.  If the link has been visited before, then the cdr is inserted.  So, links look like:

     [[This is a hypertext link]] that has never been visited.
     {{This one, however}} has been seen before at some point in time.

--------------------
Formatting of lists
--------------------
There are several different ways to control the formatting of lists. The most obvious is how deeply they are indented relative to the rest of the paragraphs in the document.  To control this, set the variable w3-indent-level.  This is the number of spaces to indent lists and other items requiring special margins.

Another thing that is easy to change about lists is the bullet character put at the front of each list item.  This is controlled by the variable w3-list-chars-assoc, which is an assoc list.  This is a list of lists, each sublist describing what to put at the start of each particular list type.  The car of this list should be a symbol (not a string) representing the type of list (e.g., ul). The rest of the list should consist of strings to insert at certain levels of lists.  The nth element of this list is used when the list is nested n + 1 levels.  If the list is not long enough to define a string for a certain nesting level, then it defaults to either a '*' or a '.'.
--------------------
Formatting of directory listings
--------------------
When Emacs-w3 encounters a link to a directory (whether by local file access or via ftp), it can either create an HTML document on the fly, or use dired-mode to peruse the listing.  The variable url-use-hypertext-dired controls this behavior.

If the value is t, Emacs-w3 uses directory-files to list them out and transform the directory into a hypertext document, then pass it through the parser like any other document.

If the value is nil, just pass the directory off to dired using find-file.  Using this option loses all the hypertext abilities of Emacs-w3, and the users is unable to load documents in the directory directly into Emacs-w3 by clicking with the mouse, etc.

A new option in the 2.2 series is url-forms-based-ftp - this is still in the experimental stages, but can be useful.  If url-forms-based-ftp is t, then all automatically generated directory listings will have a form mixed in with the file listing. Each file will have a checkbox next to it, and a row of buttons at the bottom of the screen.  Selecting one of the buttons at the bottom of the screen will take the designated action on all the marked files. Currently, only deleting and copying marked files is supported.
--------------------
Formatting of gopher directories
--------------------
There are two different ways of viewing gopher links.  The built-in support that converts gopher directories into HTML, or the gopher.el package by Scott Snyder snyder@fnald0.fnal.gov. The variable that controls this is w3-use-hypertext-gopher.  If set to nil, then gopher.el is used.  Any other value causes Emacs-w3 to use its internal gopher support.  If using gopher.el, all the hypertext capabilities of Emacs-w3 are lost. All the functionality of gopher.el is now available in the hypertext version, and the hypertext version supports Gopher+ and ASK blocks.

The main way to control the display of gopher directories is by the variable w3-gopher-labels.  This variable controls the text that is inserted at the front of each item.  This is an assoc list of gopher types (as one character strings), and a string to insert just after the list item.  All the normal gopher types are defined.  Entries should be similar to: ("0" . "(TXT)").  I have tried to keep all the tags to three characters plus two parentheses.
--------------------
Creating a horizontal rule
--------------------
Horizontal rules (<HR> tags in HTML[+]) are used to separate chunks of a document, and is meant to be rendered as a solid line across the page.  Some terminals display characters differently, so the variable w3-horizontal-rule-char controls which character is used to draw a horizontal bar.  This variable must be the ASCII value of the character, not a string.  The variable is passed through make-string whenever a horizontal rule of a certain width is necessary.

On character based terminals
============================

On character based terminals, there is no easy way to show that a certain range of text is in bold or italics.  If the variable w3-delimit-emphasis is non-nil, then Emacs-w3 can insert characters before and after character formatting commands in HTML documents.  The defaul value of w3-delimit-emphasis is automatically set based on the type of window system and version of Emacs being used.

Two variables control what text is inserted around different markup tags.  w3-header-chars-assoc controls what characters are inserted around header items, and w3-style-chars-assoc controls what characters are inserted around most other markup (italics, addresses, etc.).

w3-header-chars-assoc is an assoc list of header tags and a list of formatting instructions.  The car of the list is the level of the header (1--6).  The rest of the list should contain three items. The first item is text to insert before the header.  The second item is text to insert after the header.  Both should have reserved characters converted to their HTML[+] entity definitions.  The third item is a function to call on the area the header is in.  This function is called with arguments specifying the start and ending character positions of the header.  The starting point is always first.  To convert a region to upper case, please use w3-upcase-region instead of upcase-region, so that URLs within the region are not corrupted.

w3-style-chars-assoc is an assoc list of style tags and a list of strings.  The car of the list is the type of style tag it specifies (DFN, B, I, etc.).  The rest of the list should contain two items.  The car is text to insert before the stylized text.  The cdr is text to insert after the stylized text.  Both should have reserved characters converted to their HTML[+] entity definitions.
If using Emacs 19.2x on a VT100 compatible terminal, Emacs-w3 can show links, headers, and various other types of emphasis in bold or underlined text.

To do this, set the variable w3-emacs19-hack-faces-p to non-nil in your ~/.emacs file.  Also make sure that the environment variable TERM is set to the correct terminal type.

If there is a function called w3-emacs19-hack-TERMINAL, then this is used to setup the special characters that turn on bold and underlined text.  If this function does not exist, it is fairly easy to write one from scratch, using the terminal's entry in the /etc/termcap file.

Each function should use the standard-display-table to replace ^A, ^B, ^C, and ^D with escape sequences that turn on highlighting. When reading the /etc/termcap file, be on the lookout for these codes:

us
     Code to turn on underlining

ue
     Code to turn off underlining

mb
     Code to turn on boldface type

se
     Code to turn off all attributes

Here is an example for creating the VT100 control sequences:

     (defun w3-emacs19-hack-vt100 ()
       "Hack 'faces' for ttys (vt100)"
       (or standard-display-table
           (setq standard-display-table (make-vector 261 nil)))
       (aset standard-display-table 1 (vector (create-glyph "\e[4m")))
       (aset standard-display-table 2 (vector (create-glyph "\e[m")))
       (aset standard-display-table 3 (vector (create-glyph "\e[5m")))
       (aset standard-display-table 4 (vector (create-glyph "\e[m")))
       )

To turn off the highlighting features, set the variable w3-emacs19-hack-faces-p to nil and execute the function w3-emacs19-unhack-faces

NOTE: This highlighting is not perfect and could cause some odd display glitches, especially when Emacs does a smart redisplay and doesn't redraw the whole screen.  C-l usually fixes these problems.

With graphics workstations
==========================

When running in a graphic environemnt (Xwindows or NeXTstep for example), the fonts and colors used by Emacs-w3 to display text can be controlled by setting a few resources.  To specify these resources:

  * Xwindows: Place them into the ~/.Xresources file or the /usr/lib/X11/app-defaults/Emacs file.

  * NeXTstep: When using the NeXTstep port of Emacs 19, use the dwrite command to install these resources.  The command should look something like: (dwrite Emacs <Style>.Attribute<item> value, where style and attribute are one of the choices below.

  * OS/2 or Windows: When using the Lucid Emacs or FSF Emacs that has been ported to the Presentation Manager or Windows 3.x, the documentation states where to store a file that Emacs looks at for Xresources.

The resources for each version of Emacs are the same.  For each style of text that Emacs-w3 uses, you can specify any of the following resources by replacing <style> with the actual style name.

  * Emacs*<Style>.AttributeFont: Font name

  * Emacs*<Style>.AttributeForeground: Foreground color

  * Emacs*<Style>.AttributeBackground: Background color

  * Emacs*<Style>.AttributeUnderline: Underline text?

Emacs-w3 uses these special style names:

w3-node-style
     For links to other documents

w3-visited-node-style
     For displaying hypertext links that have been viewed before

All other styles can be specified by using the tag name as the <Style> section of the resource.  For example: Emacs*h1.attributeForeground, or Emacs*address.attributeForeground.

When running in Lucid Emacs 19.10 or XEmacs 19.11 and higher, Emacs-w3 can display inlined images and MPEG movies.  There are several variables that control how and when the images are displayed.

Since Lucid/XEmacs only natively understands XPixmaps and XBitmaps, GIFs and other image types must first be converted to one of these formats. To do this, the netpbm utilities (Available via anonymous ftp from ftp.x.org:/R5contrib/netpbm-1mar1994.tar.gz, and most large ftp sites.) programs are normally used.  This is a suite of freeware image conversion tools.  The variable w3-graphic-converter-alist controls how each image type is converted.  This is an assoc list, keyed on the MIME content-type.  The car is the content-type, and the cdr is a string suitable to pass to format.  A %s in this string will be replaced with a converter from the ppm image format to an XPixmap (or XBitmap, if being run on a monochrome display).  By default, the emacs-w3 browser has converters for:

 1. image/x-xbitmap

 2. image/xbitmap

 3. image/xbm

 4. image/gif

 5. image/jpeg

 6. image/x-fax

 7. image/x-raster

 8. image/windowdump

 9. image/x-icon

 10. image/portable-graymap

 11. image/portable-pixmap

 12. image/x-pixmap

 13. image/x-xpixmap

 14. image/pict

 15. image/x-macpaint

 16. image/x-targa

 17. image/tiff

Since most displays are (sadly) not 24-bit, Emacs-w3 can automatically dither an image, so that it does not fill up the application' colormap too quickly.  If w3-color-use-reducing is non-nil, then the images will use reduced colors.  If w3-color-filter is eq to 'ppmquant, then the ppmquant program will be used.  If eq to 'ppmdither, then the ppmdither program will be used.  The ppmdither program tends to give better results.  The values of w3-color-max-red, w3-color-max-blue, and w3-color-max-green control how many colors the inlined images can use.  If using ppmquant, then the product of these three variables is used as the maximum number of colors per image.  If using ppmdither, then only the set number of color cells can be allocated per image.  See the man pages for ppmdither and ppmquant for more information on how the dithering is actually done.  w3-color-filter may also be a string, specifying exactly what external filter to use.  An example is: ppmquant -fs -map ~/pixmaps/colormap.ppm.

When running in XEmacs 19.11 or XEmacs 19.12, Emacs-w3 can insert an MPEG movie in the middle of a buffer.  This utilizes a now deprecated feature of HTML 3.0, so its use should be limited to pages you do not mind modifying once the standard way to do this is nailed down.

The basic syntax is:

     <embed href="somevideo.mpg" type="video/mpeg">

This requires a special version of the standard mpeg_play mpeg player.  Patches against the 2.0 version are available at ftp://ftp.cs.indiana.edu/pub/elisp/w3/mpeg_patch.  The variable w3-mpeg-program should point to this executable, and w3-mpeg-args should be a list of any additional arguments to be passed to the player.  By default, this includes -LOOP, so the mpeg plays continuously.

Because images and movies can take up an incredible amount of bandwidth, it is useful to be able to control whether they are loaded or not.  By default, images and movies are loaded automatically, but the variables w3-delay-image-loads and w3-delay-mpeg-loads control this. If set to non-nil, then the images or movies are not loaded until explicitly requested by the user.

To load any delayed images, use the function w3-load-delayed-images.  Its counterpart for delayed movies is w3-load-delayed-mpegs

HTTP/1.0 Support
****************

The new revision of the HTTP specification adds much more functionality to the server side of a transaction.  Access authorization has been added, and several types of redirection can occur.  All of this negotiation and redirection should take place before the user ever sees the first requested page---this avoids the overhead of parsing any error messages or old documents the server may have returned with the redirection or authorization message.  The new protocol is also MIME (Multipurpose Internet Mail Extensions, see RFC 1341) compliant.

Redirection
===========

One of the most useful aspects of HTTP/1.0 is the ability to transparently move files between different servers (perhaps even different protocols).  Most of the WWW browsers support redirection in some form or another.  The Emacs browser supports all three types of redirection in the HTTP/1.0 specification (error codes 301, 302, and 303).

Whenever a redirection response is detected, the URL specified by the Location: header is retrieved.  All relative references are resolved before requesting the new URL.

An HTML editor that is tightly integrated with Emacs-w3 is planned, and will include the ability to edit documents to change their links if a permanent relocation is seen.

Authentication
==============

Lots of information is useful to a group of people within an organization, or a group working on a project, but it is not always wise to distribute this information to the world at large.

The HTTP/1.0 protocol adds the capability to have authentication based on usernames and passwords.  If the improper username/password pair is sent to the server, an error code of 401, Unauthorized is returned by the server.

The browser has a very extensible interface to its authentication handling. When a 401 error code is received, the WWW-Authenticate header is checked---this header field should be a space-separated list of suitable authorization schemes for the requested URL.  The value of this header is read into a lisp symbol by way of Emacs's read-string function.  This lisp symbol looks like url-authtype-auth, where authtype is replaced by the correct authorization type.  The authorization types defined in the latest HTTP/1.0 specification include user, basic, public key, and kerberos (versions 4 and 5).  If a function of this name is currently defined, then the function is called via funcall with several parameters:

 1. The URL being authenticated.

 2. whether to prompt for a username/password if no cached data is found.

 3. whether to overwrite an old username/password if the information is found in the cache.

This interface was chosen for its flexibility and extensibility.  The main routine that does the MIME parsing and the building of the Authorization header does not need to know how to handle each type of authentication, and the addition of a new method for authentication is simply a matter of defining one function that conforms to a simple interface.

Payment
=======

The Chargeto: header will be used to pay for services offered over the World Wide Web.  Such things as electronic magazines and commercial databases all need a way to restrict access to only authorized subscribers.  The format of the header has yet to be specified, but the interface and storage techniques will be similar to the Authorization section.

MIME Support
============

MIME is an emerging standard for multimedia mail.  It offers a very flexible typing mechanism.  The type of a file/message is specified in two parts, separated by a '/'.  The first part is a general category of data (text, application, image, etc.).  The second part is the specific type of data (postscript, gif, jpeg, etc.).  So text/html specifies an HTML document, whereas image/x-xwindowdump specifies an image of an Xwindow taken with the xwd program.

This typing allows much more flexibility in naming files.  HTTP/1.0 servers can now send back content-type headers in response to a request, and not have the client second-guess it based on file extensions.  HTML files can now be named something.gif (not a great idea, but doable).

Adding MIME types based on file extensions
------------------------------------------

For some protocols however, it is still necessary to guess the content of a file based on the file extension.  This type of guess-work should only be needed when accessing files via FTP, local file access, or old HTTP/0.9 servers.

Instead of specifying how to view things twice, once based on content-type and once based on the file extension, it is easier to map file extensions to MIME content-types.  The variable that controls this is mm-mime-extensions.

This variable is an assoc list of file extensions and the corresponding MIME content-type.  A sample entry looks like: (".movie" . "video/x-sgi-movie") This makes all files that end in .movie (foo.movie and bar.movie) be interpreted as SGI animation files.  If a content-type is defined for the document, then this is over-ridden.  Regular expressions can NOT be used.

Both Mosaic and the NCSA HTTP daemon rely on a separate file for mapping file extensions to MIME types.  Instead of having the users of Emacs-w3 duplicate this in lisp, this file can be parsed using the url-parse-mimetypes function.  This function is called each time w3 is loaded.  It tries to locate mimetype files in several places. If the environment variable MIMETYPES is nonempty, then this is assumed to specify a UNIX-like path of mimetype files (this is a colon separated string of pathnames).  If the MIMETYPES environment variable is empty, then Emacs-w3 looks for these files:

 1. ~/.mime-types

 2. /etc/mime-types

 3. /usr/etc/mime-types

 4. /usr/local/etc/mime-types

 5. /usr/local/www/conf/mime-types

Each line contains information for one http type.  These types resemble MIME types.  To add new ones, use subtypes beginning with x-, such as application/x-myprogram.  Lines beginning with # are comment lines, and suitably ignored.  Each line consists of:

type/subtype ext1 ext2 ...  extN

type/subtype is the MIME-like type of the document. ext* is any number of space-separated filename extensions which correspond to the MIME type.

Mapping gopher types to MIME types
----------------------------------

In order to avoid having to specify viewers for gopher in a different way, Emacs-w3 converts gopher types to MIME media types and uses the standard mailcap viewers.  The variable url-gopher-to-mime determines how this mapping of gopher types to MIME is done.  This is an assoc list, the car of each element should be a character (not a string) specifying the gopher type.  The cdr of each element should be a string, specifying what MIME media type the gopher object should be treated as.

The default value for this should be sufficient for most uses, but if any gopher types have been left out, or mislabeled, please let wmperry@spry.com know.

Specifying Viewers
------------------

Not all files look as they should when parsed as an HTML document (whitespace is stripped, paragraphs are reformatted, and lots of little changes that make the document look unrecognizable).  Files may be passed to external programs or Emacs Lisp functions to be viewed.

Not all files can be viewed accurately from within an Emacs session (GIF files for example, or audio files).  For this reason, the user can specify file "viewers" based on MIME content-types.  This is done with the standard mailcap file.  See Mailcap File

Mailcap File
============

NCSA Mosaic and almost all other WWW browsers rely on a separate file for mapping MIME types to external viewing programs.  This takes some of the burden off of browser developers, so each browser does not have to support all image formats, or postscript, etc.  Instead of having the users of Emacs-w3 duplicate this in lisp, this file can be parsed using the mm-parse-mailcaps function.  This function is called each time w3 is loaded.  It tries to locate mimetype files in several places. If the environment variable MAILCAPS is nonempty, then this is assumed to specify a UNIX-like path of mimetype files (this is a colon separated string of pathnames).  If the MAILCAPS environment variable is empty, then Emacs-w3 looks for these files:

 1. ~/.mailcap

 2. /etc/mailcap

 3. /usr/etc/mailcap

 4. /usr/local/etc/mailcap

This format of this file is specified in RFC 1343, but a brief synopsis follows (this is taken verbatim from sections of RFC 1343).

Each mailcap file consists of a set of entries that describe the proper handling of one media type at the local site.  For example, one line might tell how to display a message in Group III fax format.  A mailcap file consists of a sequence of such individual entries, separated by newlines (according to the operating system's newline conventions). Blank lines and lines that start with the "#" character (ASCII 35) are considered comments, and are ignored.  Long entries may be continued on multiple lines if each non-terminal line ends with a backslash character ('\', ASCII 92), in which case the multiple lines are to be treated as a single mailcap entry.  Note that for such "continued" lines, the backslash must be the last character on the line to be continued.

Each mailcap entry consists of a number of fields, separated by semi-colons.  The first two fields are required, and must occur in the specified order.  The remaining fields are optional, and may appear in any order.

The first field is the content-type, which indicates the type of data this mailcap entry describes how to handle.  It is to be matched against the type/subtype specification in the "Content-Type" header field of an Internet mail message.  If the subtype is specified as "*", it is intended to match all subtypes of the named content-type.

The second field, view-command, is a specification of how the message or body part can be viewed at the local site.  Although the syntax of this field is fully specified, the semantics of program execution are necessarily somewhat operating system dependent.

The optional fields, which may be given in any order, are as follows:

  * The "compose" field may be used to specify a program that can be used to compose a new body or body part in the given format.  Its intended use is to support mail composing agents that support the composition of multiple types of mail using external composing agents.  As with the view- command, the semantics of program execution are operating system dependent.  The result of the composing program may be data that is not yet suitable for mail transport---that is, a Content-Transfer-Encoding may need to be applied to the data.

  * The "composetyped" field is similar to the "compose" field, but is to be used when the composing program needs to specify the Content-type header field to be applied to the composed data.  The "compose" field is simpler, and is preferred for use with existing (non-mail-oriented) programs for composing data in a given format.  The "composetyped" field is necessary when the Content-type information must include auxilliary parameters, and the composition program must then know enough about mail formats to produce output that includes the mail type information.

  * The "edit" field may be used to specify a program that can be used to edit a body or body part in the given format.  In many cases, it may be identical in content to the "compose" field, and shares the operating-system dependent semantics for program execution.

  * The "print" field may be used to specify a program that can be used to print a message or body part in the given format.  As with the view-command, the semantics of program execution are operating system dependent.

  * The "test" field may be used to test some external condition (e.g.  the machine architecture, or the window system in use) to determine whether or not the mailcap line applies.  It specifies a program to be run to test some condition.  The semantics of execution and of the value returned by the test program are operating system dependent.  If the test fails, a subsequent mailcap entry should be sought.  Multiple test fields are not permitted---since a test can call a program, it can already be arbitrarily complex.

  * The "needsterminal" field indicates that the view-command must be run on an interactive terminal.  This is needed to inform window-oriented user agents that an interactive terminal is needed.  (The decision is not left exclusively to the view-command because in some circumstances it may not be possible for such programs to tell whether or not they are on interactive terminals.)  The needsterminal command should be assumed to apply to the compose and edit commands, too, if they exist.  Note that this is NOT a test---it is a requirement for the environment in which the program will be executed, and should typically cause the creation of a terminal window when not executed on either a real terminal or a terminal window.

  * The "copiousoutput" field indicates that the output from the view-command will be an extended stream of output, and is to be interpreted as advice to the UA (User Agent mail- reading program) that the output should be either paged or made scrollable. Note that it is probably a mistake if needsterminal and copiousoutput are both specified.

  * The "description" field simply provides a textual description, optionally quoted, that describes the type of data, to be used optionally by mail readers that wish to describe the data before offering to display it.

  * The "x11-bitmap" field names a file, in X11 bitmap (xbm) format, which points to an appropriate icon to be used to visually denote the presence of this kind of data.

  * Any other fields beginning with "x-" may be included for local or mailer-specific extensions of this format.  Implementations should simply ignore all such unrecognized fields to permit such extensions, some of which might be standardized in a future version of this document.

Security
********

There are an increasing number of ways to authenticate yourself to a web servivce.  Emacs-w3 tries to support as many as possible.

HTTP/1.0 Basic Authentication
=============================

The weakest authentication available, not recommended if you are at all serious about security on your web site.  This is simply a string that looks like user:password that has been Base64 encoded, as defined in RFC 1421.  It is given as an example of how to write an authorization module.  All of the functions for storing, retrieving, and over-writing the cached authorization information should all be handled by one function (although it would be perfectly acceptable to have a stub function that passed off to three larger functions based on its parameters).  The most efficient way to store the cached information is by an assoc-list of assoc-lists.  The top level assoc list is keyed on the name of the server. The secondary assoc-list is keyed on the full path of the file that is protected.  Thus, a sample authorization cache would look like this:

     ((``info.cern.ch''    . ((``/foo''        . ``d21wZXJyeTp0ZXN0aW5n'')
                              (``/bar''        . ``amtvbnJhdGg6ZGlzbWVtYmVy'')
                              (``/foo/x.html'' . ``dmlvbGV0dDpvcGVuZ2w='')))
      (``cs.indiana.edu''  . ((``/elisp/w3/''  . ``dGxvb3M6Y29ucXVlcg=='')
                              (``/''           . ``bXZhbmhleW46a2lsbGh1bGljaw=='')))
     )

The structure consists of two assoc-lists for the sake of speed.  The list of cached information could conceivably hold several thousand links (if the user does not exit Emacs for long periods of time.)  If the list were keyed on a full URL, the assoc function would have to search through every link before failing to find a new URL.  With the current scheme, assoc only has to search though a few items (maximum is the number of HTTP servers, which should always be much, much smaller than the number of distinct URLs.)  Even with a 3:1 ratio of URLs to each server, this is a big win.

HTTP/1.0 Digest Authentication
==============================

Jeffery L. Hostetler, John Franks, Philip Hallam-Baker, Ari Luotonen, Eric W. Sink, and Lawrence C. Stewart have an internet draft for a new authentication mechanism.  For the complete specification, please see draft-ietf-http-digest-aa-01.txt in your nearest internet drafts archive (One is ftp://ds.internic.net/internet-drafts).  What follows is mainly taken from the March 24, 1995 version of the internet draft.

The protocol referred to as "HTTP/1.0" includes specification for a Basic Access Authentication scheme.  This scheme is not considered to be a secure method of user authentication, as the user name and password are passed over the network in an unencrypted form.  A specification for a new authentication scheme is needed for future versions of the HTTP protocol.  This document provides specification for such a scheme, referred to as "Digest Access Authentication".

The Digest Access Authentication scheme is not intended to be a complete answer to the need for security in the World Wide Web.  This scheme provides no encryption of object content.  The intent is simply to facilitate secure access authentication.

Like Basic Access Authentication, the Digest scheme is based on a simple challenge-response paradigm.  The Digest scheme challenges using a nonce value.  A valid response contains the MD5 checksum of the password and the given nonce value.  In this way, the password is never sent in the clear.  Just as with the Basic scheme, the username and password must be prearranged in some fashion.

If a server receives a request for an access-protected object, and an acceptable Authorizatation header is not sent, the server responds with:

     HTTP/1.1 401 Unauthorized
     WWW-Authenticate: Digest realm="<realm>",
                                 domain="<domain>",
                                 nonce="<nonce>",
                                 opaque="<opaque>",
                                 stale="<TRUE | FALSE>"

The meanings of the identifers used above are as follows:

<realm>
     A name given to users so they know which username and password to send.

<domain>  OPTIONAL
     A comma separated list of URIs, as specified for HTTP/1.0.  The intent is that the client could use this information to know the set of URIs for which the same authentication information should be sent.  The URIs in this list may exist on different servers.  If this keyword is omitted or empty, the client should assume that the domain consists of all URIs on the responding server.

<nonce>
     A server-specified integer value which may be uniquely generated each time a 401 response is made.  Servers may defend themselves against replay attacks by refusing to reuse nonce values.  The nonce should be considered opqaue by the client.

<opaque>  OPTIONAL
     A string of data, specified by the server, which should returned by the client unchanged.  It is recommended that this string be base64 or hexadecimal data.  Specifically, since the string is passed in the header lines as a quoted string, the double-quote character is not allowed.

<stale>   OPTIONAL
     A flag, indicating that the previous request from the client was rejected because the nonce value was stale.  If stale is TRUE, the client may wish to simply retry the request with a new encrypted response, without reprompting the user for a new username and password.

The client is expected to retry the request, passing an Authorization header line as follows:

     Authorization: Digest
                username="<username>",             -- required
                realm="<realm>",                   -- required
                nonce="<nonce>",                   -- required
                uri="<requested-uri>",             -- required
                response="<digest>",               -- required
                message="<message-digest>",        -- OPTIONAL
                opaque="<opaque>"                  -- required if provided by server

             where <digest> := H( H(A1) + ":" + N + ":" + H(A2) )
       and <message-digest> := H( H(A1) + ":" + N + ":" + H(<message-body>) )

             where:

                     A1 := U + ':' + R + ':' + P
                     A2 := <Method> + ':' + <requested-uri>

                     with:
                             N -- nonce value
                             U -- username
                             R -- realm
                             P -- password
                             <Method> -- from header line 0
                             <requested-uri> -- uri sans proxy/routing

Where H() is the RSA Data Security, Inc. MD5 Message-Digest Algorithm (RFC 1321.  R.Rivest, "The MD5 Message-Digest Algorithm", http://ds.internic.net/rfc/rfc1321.txt, April 1992.).

Upon receiving the Authorization information, the server may check its validity by looking up its known password which corresponds to the submitted <username>.  Then, the server must perform the same MD5 operation performed by the client, and compare the result to the given <response>.

Note that the HTTP server does not actually need to know the user's clear text password.  As long as H(A1) is available to the server, the validity of an Authorization header may be verified.

All keyword-value pairs must be expressed in characters from the US-ASCII character set, excluding control characters.

SSL
===

SSL is the Secure Sockets Layer interface developed by Netscape Communications  (http://www.netscape.com/).

In order to use SSL in Emacs-w3, you will need one of the reference implementations of SSL that are publicly available.  These are the implementations that I am aware of:

SSLRef 2.0
     Available from Netscape Communications at http://www.netscape.com/newsref/std/sslref.html.  This requires the RSARef library, which is not exportable.  The RSARef library is available from ftp://ftp.rsa.com/rsaref/

SSLeay 0.4
     An implementation by Eric Young (eay@mincom.oz.au) that is free for commerial or noncommercial use, and was developed completely outside the US by a non-US citizen.  More information can be found at ftp://ftp.psy.uq.oz.au/pub/Crypto/SSL/

Whichever reference implementation you choose to download (I recommend the SSLeay distribution, just to thumb a nose at the NSA :), you must have a program you can run in a subprocess that takes a hostname and port number on the command line, and reads/writes to standard input/output (the Netscape implementation comes with one of these by default).  Once you hvae this program, set the variable ssl-program-name to point to the executable.

This should be all you need to do.  In the future, I will be distributing a set of patches to Emacs 19.xx and XEmacs 19.xx to SSL-enable them, for the sake of speed.

NOTE: This implementation does not support the use of client certificates, but then nobody else supports that area of the protocol either, so I'm not too worried about it.

PGP/PEM
=======

Most of this section was taken from the documentation written by Rob McCool robm@ncsa.uiuc.edu.  Gratefully reproduced here with permission from him. (See http://hoohoo.ncsa.uiuc.edu/docs/PEMPGP.html).

RIPEM is 'Riordan's Internet Privacy Enhanced Mail', and is currently on version 1.2b3.  US citizens can ftp it from ripem.msu.edu:/pub/crypt/ripem.

PGP is 'Pretty Good Privacy', and is currently on version 2.6.  The legal controversies that plagued earlier versions have been resolved, so this is a competely legal program now.  There is also a legal version for european users, called 2.6ui (the Unofficial International version).

PGP and PEM are programs to allow you and a second party to communicate in a way which does not allow third parties to read them, and which certify that the person who sent the message is really who they claim they are.

PGP and PEM both use RSA encryption.  The U.S.  government has strict export controls over foreign use of this technology, so people outside the U.S.  may have a difficult time finding programs which perform the encryption.

You will need a working copy of either Pretty Good Privacy or RIPEM to begin with.  You should be familiar with the program and have generated your own public/private key pair.  You should be able to use the TIS/PEM program with the PEM authorization type.  I haven't tried it.  This tutorial is written assuming that you are using RIPEM.

Currently, the protocol has been implemented with PEM and PGP using local key files on the server side, and on the client side with PEM using finger to retrieve the server's public key.

As you can tell, parties who wish to use Emacs-w3 and httpd with PEM or PGP encryption will need to communicate beforehand and find a tamper-proof way to exchange their public keys.

Pioneers get shot full of arrows.  This work is currently in the experimental stages and thus may have some problems that I have overlooked.  The only known problem that I know about is that the messages are currently not timestamped.  This means that a malicious user could record your encrypted message with a packet sniffer and repeat it back to the server ad nauseum.  Although they would not be able to read the reply, if the request was something you were being charged for, you may have a large bill to pay by the time they're through.

This protocol is almost word-for-word a copy of Tony Sander's RIPEM based scheme, generalized a little.  Below, wherever you see PEM you can replace it with PGP and get the same thing.

     *Client:*

     GET /docs/protected.html HTTP/1.0
     UserAgent: Emacs-W3/2.1.x

     *Server:*

     HTTP/1.0 401 Unauthorized
     WWW-Authenticate: PEM entity="webmaster@hoohoo.ncsa.uiuc.edu"
     Server: NCSA/1.1

     *Client:*

     GET / HTTP/1.0
     Authorization: PEM entity="robm@ncsa.uiuc.edu"
     Content-type: application/x-www-pem-request

     --- BEGIN PRIVACY-ENHANCED MESSAGE ---
     this is the real request, encrypted
     --- END PRIVACY-ENHANCED MESSAGE ---

     *Server:*

     HTTP/1.0 200 OK
     Content-type: application/x-www-pem-reply

     --- BEGIN PRIVACY-ENHANCED MESSAGE ---
     this is the real reply, encrypted
     --- END PRIVACY-ENHANCED MESSAGE ---
     That's it.

Emacs-w3 uses the excellent mailcrypt package written by Jin S Choi jsc@mit.edu. (Available via anonymous ftp to archive.cis.ohio-state.edu in /pub/gnu/emacs/elisp-archive/interfaces/mailcrypt.el.Z).  This package takes care of calling ripem and/or pgp with the correct arguments.  Please see the documentation at the top of mailcrypt.el for instructions on using mailcrypt.  All bug reports about mailcrypt should go to Jin S Choi, but bugs about how I use it in Emacs-w3 should of course be directed to me.

Non-Unix Operating Systems
**************************

VMS
===

:: WORK ::

OS/2
====

:: WORK ::

MS-DOS
======

:: WORK ::

16-Bit Windows
==============

:: WORK ::

32-Bit Windows
==============

:: WORK ::

Macintosh
=========

:: WORK ::

Amiga
=====

:: WORK ::

Advanced Features
*****************

Style Sheets
============

Emacs-w3 currently supports the experimental style sheet mechanism proposed by H&kon W. Lie of the W3 Consortium.  This allows for the author to specify what a document should look like, and yet allow the end user to override any of the stylistic changes.  This allows for people with special needs (most notably the visually impaired) to override style bindings that could make a document totally unreadable.

A stylesheet consists of comments and directives.  A comment is any line starting with a #, and is terminated by the end of the line.  A directive includes the tag name, an attribute name, and a value.  A sample stylesheet is:

     <style notation="experimental">
     # This line is a comment
     # These will be ignored, up the the terminating end-of-line
     #
     h1: align=center
     h1: color.text=yellow
     h1: color.background=red
     h1: font.size *= 2
     </style>

Below is a comprehensive list of the attribute names.

color.text
     Specifies the foreground color of the text for this item.

color.background
     Specifies the background color of the text for this item.

background.bitmap
     Specifies a bitmap to be used as the background for this item.

font.size
     Specifies the font size.  This can be specified with the +=, -=, /=, or *=  operator, signifying a change from the default font size.  For example, font.size *= 2 would mean a font twice as large as the default font.

font.style
     Specifies the font style.  This controls whether a font is bold, italic, underlined, or any combination of these.  The value can be a comma or ampersand (&) separated list of values.

font.family
     Specifies the font family - this is the basic type of font.  Note that not all font families will be available on all platforms, or even the same platform in a slightly different configuration.  If the specified font family cannot be found on the machine, the default font is used instead.

align
     Specifies how the text contained within the item is to be aligned. Possible values are left, right, justify, center, or indent.

width
     Specifies how wide the item should be.  This is only used for horizontal rules (<HR>) tags right now.

To include a stylesheet into your document, simply use the <style> tag. You can use the notation attribute to specify what language the stylesheet is specified in.  The default is experimental.  The data between the <style> and </style> tags is the stylsheet proper - no HTML parsing is done to this data - it is treated similar to an <XMP> section of text.  To reference an external stylesheet, you should use the <link> tag.

     <link rel="stylesheet" href="/bill.style">

If these two mechanisms are mixed, then the URL is resolved first, and the contents of the <style> tag take precedence if there are any conflicting directives.

In the future, DSSSL and DSSSL-lite will be supported as valid stylesheet languages, but not in this release.

Disk Caching
============

A cache stores the information on a page on your local machine.  When requesting a page that is in the cache, Emacs-w3 can retrieve the page from the cache more quickly than retrieving the page again from its location out on the network.  With a well-populated cache, the speed of browsing the web is dramatically increased.

The first time a page is requested, Emacs-w3 retrieves the page from the network.  When requesting a page that is in the cache, Emacs-w3 checks to see if the page has changed since it was last retrieved from the remote machine.  If it has not changed, the local copy is used, saving the transmission of the file over the network.

To turn on disk caching, set the variable url-automatic-caching to non-nil, or choose the 'Caching' menu item (under `Options'). That is all there is to it.  It is recommended that you use the clean-cache shell script fist, to allow for future cleaning of the cache.  This shell script will remove all files that have not been accessed since it was last run.  To keep the cache pared down, it is recommended that this script be run from at or cron (see the manual pages for crontab(5) or at(1) for more information)

With a large cache of documents on the local disk, it can be very handy when traveling, or any other time the network connection is not active (a laptop with a dial-on-demand PPP connection, etc).  Emacs-w3 can rely solely on its cache, and avoid checking to see if the page has changed on the remote server.  In the case of a dial-on-demand PPP connection, this will keep the phone line free as long as possible, only bringing up the PPP connection when asking for a page that is not located in the cache.  This is very useful for demonstrations as well.  To turn this feature on, set the variable url-standalone-mode to non-nil, or choose the `Use Cache Only' menu item (under `Options')

Emacs-w3 caches files under the temporary directory specified by url-temporary-directory, in a user-specific subdirectory (determined by the user-real-login-name function).  The cache files are stored under their original names, so a URL like: http://www.spry.com/foo/bar/baz.html would be stored in a cache file named: /tmp/wmperry/com/spry/www/foo/bar/baz.html.  Sometimes, espcially with gopher links, there will be name conflicts, and an error will be signalled.  This cannot be avoided, and still have reasonable performance at startup time (reading in an index file of all the cached pages can take a long time on slow machines, or even fast machines with large caches).  If you are running XEmacs 19.12 or later, you can use an alternate naming scheme that avoids name conflicts, but loses the human readability of the cache file names.  The cache files will look like: /tmp/wmperry/acbd18db4cc2f85cedef654fccc4a4d8, which is certainly unique, but not very user-friendly.  To turn this on, add this to your .emacs file:

     (add-hook 'w3-load-hooks '(lambda ()
                                  (fset 'url-create-cached-filename
                                        'url-create-cached-filename-using-md5)))

If you will not be using other emacs variants, I highly recommend this method of creating the cache filename.

Searching
=========

In the file w3-search.el is a function that some may find handy.  It is not 100% completed yet, so if you run into any problems with it, please try to fix it, not just say its broken.

The function is w3-do-search.  It must be called with at least one argument.  All others are optional.  Arguments are TERM, BASE, HOPS-LIMIT, and RESTRICTION.  This recursively descends all the child links of the current document for TERM. TERM may be a string, in which case it is treated as a regular expression, and re-search-forward is used, or a symbol, in which case it is funcalled with 1 argument, the current URL being searched.

BASE is the URL to start searching from.

HOPS-LIMIT is the maximum number of nodes to descend before the search dies out.

RESTRICTION is a regular expression or function to call with one argument, a URL that could be searched.  If RESTRICTION returns non-nil, then the URL is added to the queue, otherwise it is discarded.  This is useful for restricting searching to either certain types of URLs (only search ftp links), or restricting searching to one domain (only search stuff in the indiana.edu domain).

You may check several variables from the main w3-do-search routine in any functions passed to it (as RESTRICTION or TERM). QUEUE is the queue of links to be searched, HOPS is the current number of hops from the root document, RESULTS is an assoc list of (URL . RETVAL), where RETVAL is the value returned from previous calls to the TERM function (or point if searching for a regular expression).

The function returns a list of the form: ((URL . RETVAL)...)

Please note that there is no interactive use for this function yet---it was designed for non-interactive, batch-mode processing.  However, if anyone wants to write a wrapper function for it, please feel free.

Interfacing to Mail/News
========================

More and more people are including URLs in their signatures, and within the body of mail messages.  It can get quite tedious to type these into the minibuffer to follow one.

To access URLs with VM, the following in your ~/.emacs or ~/.vm files should do the trick.  It adds two keybindings to the main VM message window.  The middle mouse button now tries to follow a hypertext link.

     (add-hook 'vm-mode-hook
               (function
                 (lambda ()
                   (define-key vm-mode-map [mouse-2] 'w3-maybe-follow-link-mouse)
                   (define-key vm-mode-map "\r"      'w3-maybe-follow-link))))

To access URLs with RMAIL, the following in your ~/.emacs file should do the trick.

     (add-hook 'rmail-mode-hook
     	  (function
     	   (lambda ()
     	     (define-key rmail-mode-map [mouse-2] 'w3-maybe-follow-link-mouse)
     	     (define-key rmail-mode-map "\r"      'w3-maybe-follow-link))))

To access URLs with GNUS, the following in your ~/.emacs file should od the trick.

     (add-hook 'gnus-article-mode-hook
               (function
                 (lambda ()
                   (define-key gnus-article-mode-map [mouse-2]
                               'w3-maybe-follow-link-mouse)
                   (define-key gnus-article-mode-map "\r"
                               'w3-maybe-follow-link))))

NOTE: XEmacs 19.12 has a special version of VM and GNUS that does the highlighting of URLs automatically.  All that is required to follow one of these links is clicking the middle mouse button on the highlighted text.

Debugging HTML
==============

If you are feeling adventurous, or are just as anal as I am about people writing valid HTML, you can set the variable w3-debug-html to t and see what happens.

If a emacs-w3 thinks it has encountered invalid HTML, then a debugging message is logged to the buffer specified by w3-debug-buffer. This can be a buffer object, or the name of a buffer.

NOTE: This has not yet been reintegrated into the new display engine and parser.

Native WAIS Support
===================

This version of Emacs-W3 supports native WAIS querying (earlier versions required the use of a gateway program).  In order to use the native WAIS support, a working waisq binary is required.  I recommend the distribution from think.com - ftp://think.com/wais/wais-8-b6.1.tar.Z is a good place to start.

The variable url-waisq-prog must point to this executable, and one of url-wais-gateway-server or url-wais-gateway-port should be nil.

When a WAIS URL is encountered, a form will be automatically generated and displayed.  After typing in your search term, the query will be sent to the server by running the url-waisq-prog in a subprocess.  The results will be converted into HTML and displayed.

Rating Links
============

The w3-link-delimiter-info variable can be used to 'rate' a URL when it shows up in an HTML page.  If non-nil, then this should be a list specifying (or a symbol specifying the name) of a function. This function should expect one argument, a fully specified URL, and should return a string.  This string is inserted after the link text.

If a user has decided that all links served from blort.com are too laden with images, and wants to be warned that a link points at this host, they could do something like this:

     (defun check-url (url)
       (if (string-match "://[^/]blort.com" url)
          "[SLOW!]" ""))

     (setq w3-link-delimiter-info 'check-url)

So that all links pointing to any site at blort.com shows up as "Some link[SLOW!]" instead of just "Some link".

Gopher+ Support
===============

The gopher+ support in Emacs-w3 is limited to the conversion of ASK blocks into HTML 3.0 forms, and the usage of the content-length given by the gopher+ server to give a nice status bar on the bottom of the screen.

This will hopefully be extended to include the Gopher+ method of content-type negotiation, but this may be a while.

Hooks
=====

These are the various hooks that can be used to customize some of Emacs-w3's behavior.  They are arranged in the order in which they would happen when retrieving a document.  All of these are functions (or lists of functions) that are called consecutively.

w3-load-hooks
     These hooks are run by w3-do-setup the first time a URL is fetched.  All the w3 variables are initialized before this hook is run.

w3-file-done-hooks
     These hooks are run by w3-prepare-buffer after all parsing on a document has been done.  All url-current-* and w3-current-* variables are initialized when this hook is run. This is run before the buffer is shown, and before any inlined images are downloaded and converted.

w3-file-prepare-hooks
     These hooks are run by w3-prepare-buffer before any parsing is done on the HTML file.  The HTTP/1.0 headers specified by w3-show-headers have been inserted, the syntax table has been set to w3-parse-args-syntax-table, and any personal annotations have been inserted by the time this hook is run.

w3-mode-hooks
     These hooks are run after a buffer has been parsed and displayed, but before any inlined images are downloaded and converted.

w3-source-file-hooks
     These hooks are run after displaying a document's source

Miscellaneous variables
=======================

There are lots of variables that control the real nitty-gritty of Emacs-w3 that the beginning user probably shouldn't mess with.  Here they are.

w3-icon-directory-list
     A list of directorys to look in for the w3 standard icons...  must end in a /!  If the directory data-directory/w3 exists, then this is automatically added to the default value of http://cs.indiana.edu/elisp/w3/icons/.

w3-keep-old-buffers
     Whether to keep old buffers around when following links.  If you do not like having lots of buffers in one Emacs session, you should set this to nil.  I recommend setting it to t, so that backtracking from one link to another is faster.

url-passwd-entry-func
     This is a symbol indicating which function to call to read in a password.  It is set up depending on whether you are running EFS or ange-ftp at startup if it is nil.  This function should accept the prompt string as its first argument, and the default value as its second argument.

w3-reuse-buffers
     Determines what happens when w3-fetch is called on a document that has already been loaded into another buffer.  Possible values are: nil, yes, and no.  nil will ask the user if Emacs-w3 should reuse the buffer (this is the default value).  A value of yes means assume the user wants to always reuse the buffer.  A value of no means assume the user always wants to re-fetch the document.

w3-show-headers
     This is a list of HTTP/1.0 headers to show at the end of a buffer.  All the headers should be in lowercase.  They are inserted at the end of the buffer in a <UL> list.  Alternatively, if this is simply t, then all the HTTP/1.0 headers are shown.  The default value is nil.

w3-show-status, url-show-status
     Whether to show progress messages in the minibuffer. w3-show-status controls if messages about the parsing are displayed, and url-show-status controls if a running total of the number of bytes transferred is displayed.  These Can cause a large performance hit if using a remote X display over a slow link, or a terminal with a slow modem.

mm-content-transfer-encodings
     An assoc list of CONTENT-TRANSFER-ENCODINGS or CONTENT-ENCODINGS and the appropriate decoding algorithms for each. If the cdr of a node is a list, then this specifies the decoder is an external program, with the program as the first item in the list, and the rest of the list specifying arguments to be passed on the command line. If using an external decoder, it must accept its input from stdin and send its output to stdout.

     If the cdr of a node is a symbol whose function definition is non-nil, then that encoding can be handled internally.  The function is called with 2 arguments, buffer positions bounding the region to be decoded.  The function should completely replace that region with the unencoded information.

     Currently supported transfer encodings are: base64, x-gzip, 7bit, 8bit, binary, x-compress, x-hqx, and quoted-printable.

url-uncompressor-alist
     An assoc list of file extensions and the appropriate uncompression programs for each.  This is used to build the Accept-encoding header for HTTP/1.0 requests.

url-waisq-prog
     Name of the waisq executable on this system.  This should be the waisq program from think.com's wais8-b5.1 distribution.

More Help
*********

If you need more help on Emacs-w3, please send me mail (wmperry@spry.com).  Several discussion lists have also been created for Emacs-w3.  To subscribe, send mail to majordomo@indiana.edu, with the body of the message 'subscribe LISTNAME <YOUR EMAIL ADDRES>'.  All other mail should go to <listname>@indiana.edu.

  * w3-announce -- this list is for anyone interested in Emacs-w3, and should in general only be used by me.  The gnu.emacs.sources newsgroup and a few other mailing lists are included on this.  You may use this if you have written an enhancement to Emacs-w3 that you wish more people to know about. (www-announce@w3.org is included on this list).

  * w3-beta -- this list is for beta testers of Emacs-w3.  These brave souls test out not-quite stable code.

  * w3-dev -- a list consisting of myself and a few other people who are interested in the internals of Emacs-w3, and doing active development work. Pretty dead right now, but I hope it will grow.

If you need more help on the World Wide Web in general, please refer to the newsgroup comp.infosystems.www.  There are also several discussion lists concerning the Web.  Send mail to listserv@w3.org with a subject line of 'subscribe <listname>'.  All mail should go to <listname>@w3.org.  Administrative mail should go to www-admin@w3.org.  The lists are:

  * www-talk -- for general discussion of the World Wide Web, where its going, new features, etc.  All the major developers are subscribed to this list.

  * www-announce -- for announcements concerning the World Wide Web.  Server changes, new servers, new software, etc.

As a last resort, you may always mail me.  I'll try to answer as quickly as I can.

Future Directions
*****************

Changes are constantly being made to the Emacs browser (hopefully all for the better).  This is a list of the things that are being worked on right now.

  Fix before 2.3

      1. Imagemap extensions (drag areas)

      2. PATHs

      3. TABLEs

      4. MATHs

      5. DSSSL and DSSSL-Lite Style sheets

  Long range goals

      1. Multi-DTD browsing

Internals of Emacs-w3
*********************

This chapter attempts to explain some of the internal workings of Emacs-w3 and various data structures that are used.  It also details some functions that are useful for using some of the Emacs-w3 functionality from within your own programs, or extending the current capabilities of Emacs-w3.

Generalized ZONES
=================

Due to the many different flavors of Emacs in existence, the addition of data and font information to arbitrary regions of text has been generalized.  The following functions are defined for using/manipulating these zones of data.

w3-add-zone (start end style data &optional highlight)
     This function creates a zone between buffer positions start and end, with font information specified by style, and a data segment of data. If the optional argument highlight is non-nil, then the region highlights when the mouse moves over it.

w3-zone-at (point)
     Returns the the zone at POINT.  Preference is given to hypertext links, then to form entry areas, then to inlined images.  So if an inlined image was part of a hypertext link, this would always return the hypertext link.

w3-zone-data (zone)
     Returns the zone's data segment. The data structures used in Emacs-w3 are relatively simple.  They are just list structures that follow a certain format.  The two main data types are form objects, link objects,and inlined images.  All the information for these types of links are stored as lists.

w3-zone-hidden-p (zone)
     Returns t if and only if a zone is currently invisible.

w3-hide-zone (start end)
     Makes a region of text from start to end invisible.

w3-unhide-zone (start end)
     Makes a region of text from start to end visible again.

w3-zone-start (zone)
     Returns an integer that is the start of zone, as a buffer position.  In Emacs 18.xx, this returns a marker instead of an integer, but it can be used just like an integer.

w3-zone-end (zone)
     Returns an integer that is the end of zone, as a buffer position.  In Emacs 18.xx, this returns a marker instead of an integer, but it can be used just like an integer.

w3-zone-eq (zone1 zone2)
     Returns t if and only if zone1 and zone2 represent the same region of text in the same buffer, with the same properties and data.

w3-delete-zone (zone)
     Removes zone from its buffer (or current buffer).  The return value is irrelevant, and varies for each version of Emacs.

w3-all-zones ()
     Returns a list of all the zones contained in the current buffer.  Useful for extracting information about hypertext links or form entry areas.  Programs should not rely on this list being sorted, as the order varies with each version of Emacs.

w3-zone-at (pt)
     This returns the zone at character position PT in the current buffer that is either a link or a forms entry area.  Returns nil if no link at point.

These data structures are what is generally returned by w3-zone-data.

Global variables
================

There are also some variables that may be useful if you are writing a program or function that interacts with Emacs-w3.  All of the w3-current-* variables are local to each buffer.

url-current-mime-headers
     An assoc list of all the MIME headers for the current document.  Keyed on the lowercase MIME header (e.g., content-type or content-encoding.

url-current-server
     Server that the current document was retrieved from.

url-current-file
     Filename of the current document

url-current-type
     A string representing what network protocol was used to retrieve the current buffer's document.  Can be one of http, gopher, file, ftp, news, or mailto.

url-current-port
     Port # of the current document.

w3-current-last-buffer
     The last buffer seen before this one.

w3-running-FSF19
     This is t if and only if we are running in FSF Emacs 19.

w3-running-epoch
     This is t if and only if we are running in Epoch 4.x

w3-running-xemacs
     This is t if and only if we are running in Lucid Emacs, WinEmacs, or XEmacs.

Data Structures
===============

Form objects are used to store information about a FORM data entry area.

 1. 'w3form

 2. A cons pair of (METHOD . URL), where METHOD specifies what method to use to retrieve the form when it is submitted (e.g., GET) and URL is a fully specified URL pointing at where to submit the FORM data to.

 3. The type of input area this is.  (e.g., CHECKBOX or RADIO)

 4. The name of the input tag.  This is used when sending the form to the server, so that the server can tell what data is what.

 5. The default value of the input area.  Gotten from the INPUT tag at creation time.

 6. The current value of the input area.

 7. Whether the item is checked or not.  Only used for RADIO or CHECKBOX items.

 8. The size (in characters) of the input area.  Not used for CHECKBOX, RADIO, or TEXTAREA input areas.

 9. The maximum length of the input.  Only used for TEXT or PASSWORD input areas.

 10. The form that this input area belongs to.  Each form in the same buffer has a unique identifier assigned when the document is parsed.  It is used when the form is submitted to get only the data for the correct form.

 11. A list of strings that represent the choices for this input area.  Only used for SELECT tags.

 12. A string or nil, specifying the ID attribute on this input tag.

A new development in the World Wide Web is the concept of collapsible areas of text.  If a zone controls one of these regions, it is marked with the w3expandlist property.  The format of this structure is:

 1. 'w3expandlist

 2. A marker representing the start of the hidden text as a buffer position.

 3. A marker representing the end of the hidden text as a buffer position.

A zone with the w3graphic property is a link to an inlined image's source file.

 1. 'w3graphic

 2. The full URL of the inlined image.  This is only ever returned if the inlined image is the only extent under point, or w3-follow-inlined-image is invoked.

A zone with the w3 property is a full-fledged hypertext link to another document.

 1. 'w3

 2. The ID attribute of this link.  Used for resolving references to specific points within a document (e.g., file.html#sectionA.

 3. The HREF attribute of this link.  This is a fully specified URL pointing at a network resource.  All relative directory references should have been removed before being stored in this structure.

 4. The text between the <A> and </A> tags.  This is used to build menus or to get the text of a link without doing a buffer-substring.

 5. The URN attribute of this link.  Currently not used for anything, waiting for the URN specification to be hammered out.

 6. The REL attribute of this link.  Specifies the links relevance to the current document.

 7. The REV attribute of this link.  Specifies the current documents relevance to the link.

 8. The METHODS attribute, which tells what methods can be used on this link.  (e.g., GET, HEAD, PUT.

Miscellaneous Functions
=======================

I have done quite a bit of work trying to make a clean interface to the internals of Emacs-w3.  Here is a list of functions that you can use to take advantage of the World Wide Web.

url-clear-tmp-buffer
     Sets the current buffer to be url-working-buffer, creating it if necessary, and erase it.  This should usually be called before retrieving URLs.

w3-convert-html-to-latex
     Takes a buffer of HTML markup (which should be in w3-working-buffer), and convert it into LaTeX.  This is an adaptation of the simple sed scripts from Cern.  Does as good a job as the html2latex program, and I usually prefer its formatting over html2latex's.

w3-fetch
     This function takes a URL as its only argument. It then attempts to retrieve the URL.  For example: (w3-fetch "http://cs.indiana.edu/") would retrieve the Indiana University CS home page and parse it as HTML.

w3-fix-entities-in-string
     This function takes a string, and removes all HTML[+] entity references from it, replacing them with the correct character(s).  It consults the variable w3-html-entities for the entity names and translations. For example, (w3-fix-entities-in-string "&gt;testing&lt;&amp;") would return ">testing<&".

url-generate-new-buffer-name
     This function takes a string, and returns the first unique buffer name using that string as a base.  For example (url-generate-new-buffer-name "new-buff") would return "new-buff<1>" if buffer new-buff already existed.

url-generate-unique-filename
     This functions returns a string that represents a unique filename in the /tmp directory.  For example, (url-generate-unique-filename) would return "/tmp/url-tmp129440".  The filename is arrived at by using a unique prefix (url-tmp), the uid of the current user (12944 in my case), and a number that is incremented if a file already exists.

url-buffer-visiting (url)
     Return the name of a buffer (if any) that is visiting URL.

url-create-mime-request (fname ref-url)
     Create a MIME request for the file fname.  The Referer: field of the HTTP/1.0 request is set to the value of ref-url if necessary.  Returns a string that can be sent to an HTTP server.  The request uses several variables that control how the request looks.

     If the value of url-request-extra-headers is non-nil, then it is used as extra MIME headers when an HTTP/1.0 request is created.

url-get-url-at-point
     This function returns the url at a point specified by an optional argument.  If no argument is given to the function (point) is used. Tries to find the url closest to that point, but does not change the users position in the buffer.  Has a preference for looking backward when not directly on a URL.

url-hexify-string
     This function takes a string and replaces any characters that are not acceptable in a URL with the "escaped" encoding that is standard for URLs (replaces the character with a % followed by the hexadecimal representation of the ASCII value of the character).  For example, (url-hexify-string "this is a test") would return "this%20is%20a%20test".

url-open-stream
     This function takes the same parameters as open-network-stream, and functions similarly.  It takes a process name, a buffer name, a host name, and a port number or server name.  It attempts to open a network connection to the remote host on the specified port/service name, with output going to the buffer.  It returns the process object that is the network connection.

url-retrieve
     This function takes 3 arguments, a URL, a method type, and a data block. It then attempts to retrieve the URL using the specified method, using data (if any) as the body of the MIME request.  For example: (url-retrieve "http://cs.indiana.edu/") would retrieve the Computer Science home page from Indiana University.  This function does no parsing of the retrieved page, and leaves you in the buffer containing the document you requested.  Any HTTP/1.0 redirection/authorization is done before this function exits.

url-unhex-string
     This is the opposite of w3-hexify-string.  It removes any %XXX encoded characters in a string.  For example (url-unhex-string "this%20is%20a%20test") would return "this is a test".

w3-view-this-url
     This function returns the URL of the zone under point (if no zone is under point, then it returns nil).  If the optional argument is nil, then the URL is also displayed in the minibuffer.

url-view-url
     This function returns the URL of current document.  If the optional argument is nil, then the URL is also displayed in the minibuffer.

MIME Functions
==============

mm-compose-type(TYPE)
     Compose a body section of MIME-type TYPE.  This uses the compose field of a mailcap entry to generate the data, and returns a string that contains the data, with a correct content-type header.

mm-extension-to-mime(EXTN)
     Return the MIME content-type of the file extension EXTN

mm-mime-info(ST ND REQUEST)
     Get the mime viewer command for a specific MIME type. If ST is a number, then the MIME type is the buffer-substring between ST and ND, otherwise ST should be a string specifying the MIME type and associated data.  Returns nil if the specified type is not found.

     Expects a complete content-type header line as its argument.  This can be simple like text/html, or complex like text/plain; charset=blah; foo=bar

     Third argument REQUEST specifies what information to return.  If it is nil or the empty string, the viewer (second field of the mailcap entry) is returned.  If it is a string, then the mailcap field corresponding to that string is returned (print, description, whatever). If a number, then all the information for this specific viewer is returned.

mm-parse-mailcap(FILE)
     Parse the mailcap file specified by FILE.

mm-parse-mailcaps(PATH)
     Parse the default mailcap files.  Optional argument PATH specifies a UNIX-style path of where to find the mailcap files.  This function must be run before the rest of the mm-* functions.

mm-parse-mimetype-file(FILE)
     Parse out a mime-types file specified by FILE.

mm-parse-mimetypes(PATH)
     Parse the default mimetypes files.  Optional argument PATH specifies a UNIX-style path of where to find the mimetypes files.