\input texinfo @c -*-texinfo-*-
-@c %**start of header
+
@setfilename elpher.info
-@settitle Elpher Manual v1.0.0
-@c %**end of header
+@settitle Elpher Manual v2.10.0
+
+@dircategory Emacs
+@direntry
+* Elpher: (elpher). A gopher and gemini client for Emacs.
+@end direntry
@copying
-This manual documents Elpher, a gopher client for Emacs.
+This manual documents Elpher, a gopher and gemini client for Emacs.
-Copyright @copyright{} 2019 Tim Vaughan
+Copyright @copyright{} 2019, 2020 Tim Vaughan
@quotation
The source and documentation of Elpher is free software. You can
@end copying
@titlepage
-@title Elpher Gopher Client Manual
+@title Elpher Gopher and Gemini Client Manual
@author Tim Vaughan
@page
@insertcopying
@end ifnottex
+@macro keycmd{key,cmd}
+@item \key\ (@code{\cmd\})
+@findex \cmd\
+@end macro
+
@menu
* Introduction:: Elpher Overview: what's this all about?
+* Installation:: Installing Elpher
+* Quick Start:: Get up and running quickly
* Navigation:: Fundamentals of Elpher navigation
* Bookmarks:: How to record and visit bookmarks
+* Gopher character encodings:: How Elpher selects encodings for gopher pages
+* Encrypted gopher connections:: How and when TLS is enabled for gopher
+* Gemini support:: Support for the Gemini protocol
+* Finger support:: Support for the Finger protocol
* Customization:: How to customize various aspects of Elpher
-* Hacking:: Contributing changes to Elpher
-* Index::
+* Command Index::
+
+@detailmenu
+ --- The Detailed Node Listing ---
+
+Navigation
+
+* Within-page navigation:: Moving about within a page
+* Between-page navigation:: Commands for moving between pages
+* History and Caching:: Explanation of how Elpher represents history
+
+@end detailmenu
@end menu
-@node Introduction, Navigation, Top, Top
+@node Introduction, Installation, Top, Top
@chapter Introduction
-Elpher aims to be a capable and practical gopher client for Emacs. Its
-focus is on easy keyboard-driven navigation based on sensible default
-bindings (with out-of-the-box support for Evil). It is intended to be
-robust and behave in non-surprising ways at all times. Additionally,
-Elpher provides the following bells and whistles:
+Elpher aims to be a capable and practical gopher and gemini client for
+Emacs. Its focus is on easy keyboard-driven navigation based on
+sensible default bindings (with out-of-the-box support for Evil). It is
+intended to be robust and behave in non-surprising ways at all times.
+Additionally, Elpher provides the following bells and whistles:
@itemize
@item
-an easily navigable history, sporting caching of visited sites (both
+followable web and gopher links in plain text,
+
+@item
+an easily navigable history, sporting caching of visited pages (both
content and cursor position),
@item
auto-completing menu item navigation,
@item
-followable web and gopher links in plain text,
+direct visualization of image files where supported (no writing to
+disk),
@item
-direct visualization of image files where supported (no writing to
-disk), and
+a bookmark management system,
@item
-a simple bookmark management system.
-@end itemize
+basic support for the new ``heavier than gopher, lighter than the web'' Gemini protocol,
-Throughout this manual, the
+@item
+support for the Finger protocol.
+
+@end itemize
Elpher is still under active development. Although we try very hard to
ensure that releases are bug-free, this cannot be guaranteed. However,
this also means that any usability features that you feel are missing
-can likely by incoroporated quickly, so please get in touch if you
+can likely by incorporated quickly, so please get in touch if you
have some ideas.
-@node Navigation, Bookmarks, Introduction, Top
+@node Installation, Quick Start, Introduction, Top
+@chapter Installation
+
+Elpher is available from the MELPA package repository. If you have
+never installed packages from this repository before, you'll need
+to follow the instructions at @url{https://melpa.org/#/getting-started}.
+
+@noindent To install Elpher, enter the following:
+
+@example
+@kbd{M-x package-install @key{RET} elpher @key{RET}}
+@end example
+
+@noindent To uninstall, use
+
+@example
+@kbd{M-x package-delete @key{RET} elpher @key{RET}}.
+@end example
+
+While not recommended, it is also possible to install Elpher directly by
+downloading the file @file{elpher.el} from
+@url{gopher://thelambdalab.xyz/1/projects/elpher/}, adding it to a directory in
+your @code{load-path}, and then adding
+
+@example
+(require 'elpher)
+@end example
+
+@noindent to your Emacs initialization file.
+
+@node Quick Start, Navigation, Installation, Top
+@chapter Quick Start
+
+Before diving into the minutiae of the different commands available,
+we will quickly describe how to get up and running with Elpher.
+
+Once installed, you can launch Elpher using
+
+@example
+@kbd{M-x elpher @key{RET}}
+@end example
+
+@noindent This will switch to the *Elpher* buffer and display a start
+page, with information on each of the default keyboard bindings.
+
+From here you can move point between links (which may be menu items or
+inline URLs in text files) by using @key{TAB} and @kbd{S-@key{TAB}},
+as in Info. You can also jump directly to a menu item using @key{m}, or
+use the standard Emacs or Evil motion and search commands to find your
+way around. To open a link, press @key{RET}. (Where a mouse is
+available, Clicking on a link with the mouse cursor has the same
+effect.)
+
+To return to the page you just followed the link from, press @key{u}.
+
+Elpher caches (for the duration of an Emacs session) both page contents
+and the position of point on each of the pages (gopher menus, gemini
+pages, query results, or text pages) you visit, restoring these when you
+next visit the same page. Thus, pressing @key{u} displays the previous
+page in exactly the same state as when you left, meaning that you can
+quickly and visually explore the different documents in a menu without
+having to wait for anything to reload.
+
+Of course, sometimes you'll @emph{want} to reload the current page
+rather than stick with the cached version. To do this use @key{R}.
+(This is particularly useful for search query results, where this
+allows you to perform a different search.)
+
+That's more-or-less it. Elpher supports a number of other features, such
+as bookmarking, support for different coding schemes and TLS encryption,
+and a variety of customization options, all of which are explained in
+the rest of this document. However the emphasis is on keeping the basic
+navigation experience as intuitive and responsive as possible.
+
+@node Navigation, Bookmarks, Quick Start, Top
@chapter Navigation
+Throughout this manual, we use the word ``page'' to refer to any
+visualization of a response from a gopher or gemini server, be it a
+menu/directory, query result, text file or image. We use
-Elpher's navigation interface heavily inspired by the Emacs Info mode.
+Elpher's navigation interface is inspired by the Emacs Info mode.
+Movement within a page is essentially the same as moving
+around any other text file in Emacs, but with special keys
+for quickly jumping between menu items and URLs in text files.
+Movement between pages is facilitated by a simple linear history
+coupled with caching of pages and cursor position.
@menu
-* Within-page navigation::
-* Between-page navigation::
+* Within-page navigation:: Moving about within a page
+* Between-page navigation:: Commands for moving between pages
+* History and Caching:: Explanation of how Elpher represents history
@end menu
+
@node Within-page navigation, Between-page navigation, Navigation, Navigation
@section Within-page navigation
-Within a single page
+To move about within a page, you should be able use the same keys you usually
+use to browse files in Emacs. This is even true when Evil mode is
+enabled. Paragraph hopping, searching etc should work as usual.
+
+In addition, the following commands are provided for quickly moving between
+links and menu items.
+
+@table @asis
+@keycmd{@key{TAB}, elpher-next-link}
+Move to the next link or menu item in the file.
+
+@keycmd{@kbd{Shift-@key{TAB}}/@key{backtab}, @code{elpher-prev-link}}
+Move to the previous link or menu item in the file.
+
+@keycmd{@key{m}, elpher-jump}
+Jump directly to a link within a file by specifying its display string
+or link text. (Unlike the previous two commands, this immediately opens
+the selected link.
+@end table
+
+The following commands can be used to retrieve information about the
+current page, or the address of the link at point:
+
+@table @asis
+@keycmd{@key{i}, elpher-info-link}
+Display host, port and selector information for the link at point.
+
+@keycmd{@key{I}, elpher-info-current}
+Display host, port and selector information for the current page.
+
+@keycmd{@key{c}, elpher-copy-link-url}
+Add URL representing address of link at point to the kill-ring and the
+system clipboard (if available).
-@node Between-page navigation, , Within-page navigation, Navigation
+@keycmd{@key{C}, elpher-copy-current-url}
+Add URL representing address of the current page to the kill-ring and
+the system clipboard (if available).
+
+@keycmd{@key{d}, elpher-download}
+Download link at point and save the result as a file. The minibuffer
+will prompt for the name of the file to write, with the default name being
+the display string (if available) associated with the link.
+
+@keycmd{@key{D}, elpher-download-current}
+This is similar to @code{elpher-download}, but instead applies to the
+current page rather than a link.
+
+@keycmd{@key{.}, elpher-view-raw}
+This displays the raw server response for the current page. While not
+useful for general browsing, it is useful for debugging incorrect rendering
+or out-of-spec server responses.
+@end table
+
+@node Between-page navigation, History and Caching, Within-page navigation, Navigation
@section Between-page navigation
-@node Bookmarks, Customization, Navigation, Top
+Moving to a different page can be accomplished in several ways,
+described by the following command:
+
+@table @asis
+@keycmd{@key{RET}\, @kbd{mouse-1}, elpher-follow-link}
+Follow the menu item or link at point (or selected with the mouse).
+
+Exactly what is meant by ``follow'' depends on the kind of item selected:
+
+@itemize
+@item
+For text or menu type items or links, the current page text is replaced
+by the text of this item. Unless the customization variable
+@code{elpher-use-header} (@pxref{Customization}) is
+@code{nil}, the display string of the link is displayed in the buffer header.
+Links to images behave similarly on Emacs systems supporting the display of
+bitmap graphics, however their content is not cached in memory by default.
+
+@item
+When followed, links to search/query items (type 7) prompt for input in
+the minibuffer then display the results in the same way as for text and menu
+items.
+
+@item
+Following links to binary files (and image files on unsupported systems)
+causes Elpher to prompt for a filename in which to save the content.
+
+@item
+Following links of type `h' with a selector having the `URL:' prefix, or
+unsuported URLs in text files, will result in Elpher using an external
+programme to open the URL. This will be either the default system browser
+or, if the @code{elpher-open-urls-with-eww} customization variable is non-nil,
+Emacs' own EWW browser. (See @pxref{Customization}.)
+
+@end itemize
+
+Once a text, menu or query response page has been displayed, its contents are
+cached for the duration of the Emacs session.
+
+@keycmd{@key{g}, elpher-go}
+Open a particular page by specifying either its full URL or just entering
+a gopher host name. (The protocol defaults to gopher, so gemini links must include the @code{gemini://} prefix.
+
+If a unsupported protocol is used in the URL the result will be the same
+as following a URL link of the same type from a link in a page.
+
+@keycmd{@key{o}, elpher-go-current}
+Prompts for a URL similar to @code{elpher-go}, but initialized to the URL
+of the current page. This allows you to easily try other selectors for the
+same server.
+
+Remember however, that the Gopher RFC 1436 provides @emph{no} guarantees about the
+structure of selectors.
+
+@keycmd{@key{O}, elpher-root-dir}
+Open the root page (empty selector) on the current host.
+
+@keycmd{@key{u}\, @kbd{mouse-3}, elpher-back}
+Return to the previous page, where ``previous'' means the page where the
+page which was displayed immediately before the current page.
+@end table
+
+
+@node History and Caching, , Between-page navigation, Navigation
+@section History and Caching
+
+The history and caching strategy in Elpher is extremely simple, but
+may be confusing without a good mental model of how it works. That
+is what this section attempts to provide.
+
+Essentially, @strong{every} time you navigate to a new page, either
+by clicking or pressing @key{RET} on a link, using @key{g} to jump
+to a new page by its address, or using @key{O} to open the root selector,
+the following two things occur:
+
+@enumerate
+@item
+the cursor position and content for the original page are recorded in an
+in-memory cache, and
+
+@item
+the original page is set as the ``parent'' of the new page.
+@end enumerate
+
+The only way to return to pages in this history is by using @key{u},
+which returns to the previous of the current page. @footnote{The
+addition of the new page to the history happens even if the new page is
+one that has been seen before. This is mostly the desired behaviour.
+However, opening an explicit ``back'' link provided by a gopher menu or
+gemini page will also add a new entry to the history. Unless you
+haven't yet visited that menu, it's therefore better to use @key{u} to
+go back in this case.}
+
+One aspect that may seem peculiar is that Elpher lacks a corresponding ``next'' or
+``forward'' command. However, since Elpher caches the position of point,
+this will be automatically positioned on the link that was most recently followed
+from a given page. This means that, at least for links followed from menus
+and text files, the inverse of @key{u} is actually just @key{RET}.
+
+
+@node Bookmarks, Gopher character encodings, Navigation, Top
@chapter Bookmarks
-@node Customization, Hacking, Bookmarks, Top
+Elpher has a very simple link bookmarking system involving the
+following commands:
+
+@table @asis
+@keycmd{@key{a}, elpher-bookmark-link}
+Add a bookmark for the link at point. The minibuffer will prompt for
+a name for the bookmark, which defaults to the display string.
+
+@keycmd{@key{A}, elpher-bookmark-current}
+Add a bookmark for the current page. The minibuffer will prompt for
+a name for the bookmark, defaulting to the display string associated
+with the link that was followed to reach the current page.
+
+@keycmd{@key{x}, elpher-unbookmark-link}
+Immediately remove the bookmark (if one exists) to the link at point.
+
+@keycmd{@key{X}, elpher-unbookmark-current}
+Immediately remove the bookmark (if one exists) to the current page.
+
+@keycmd{@key{B}, elpher-bookmarks}
+Open a page displaying all current bookmarks. Note that this bookmark
+page is added to the history just as if you had opened it using a link.
+Thus to return to the previous page, use @kbd{u}. This also means
+that you can peruse the various bookmarks by visiting them in turn,
+using @kbd{u} to return to the bookmark page (where the position of point
+is cached), then moving to another bookmarked link and so on.
+@end table
+
+Bookmarks are stored as a s-exp in the file @file{elpher-bookmarks}
+in the user emacs directory (usually @file{~/.emacs.d/}).
+Any command which modifies the list of bookmarks immediately updates
+this file.
+
+@node Gopher character encodings, Encrypted gopher connections, Bookmarks, Top
+@chapter Gopher character encodings
+
+Responses Elpher retrieves from servers are initially read as pure
+binary data. When the data is intended to be interpreted as textual (as
+determined by the type parameter of the gopher menu item or the gopher
+URL), this data needs to be @emph{decoded} into a sequence of
+characters. To do this properly requires knowledge of the encoding
+system used by whoever authored the document.
+
+Unfortunately gopher lacks a systematic way of acquiring this necessary
+information. Thus, the details of the coding system must be either inferred from the binary data,
+or must be specified by the user.
+
+By default, Elpher applies Emacs' built-in character encoding detection
+system to the full (undecoded) response data and uses this to attempt to
+convert it into a character string.
+(See @pxref{Recognize coding, Recognizing coding systems, ,emacs}.) While
+this approach can be okay, it is important to realize that its inference
+algorithm is extremely primitive and depends heavily on assumptions based
+on the language settings of your emacs system.
+
+The alternative is to explicitly set the coding system used for decoding
+using the following command:
+
+@table @asis
+@keycmd{@key{S},elpher-set-coding-system}
+Causes a elpher to prompt for a coding system to use for decoding
+future gopher text. The @key{TAB} key can be used at this prompt to display a
+list of alternatives (which is extensive) and to auto-complete. An empty
+response will cause Elpher to return to its default auto-detection
+behaviour.
+@end table
+
+Note that changing the coding system only affects newly loaded text.
+Thus, if text has already been decoded using an incorrect system, you
+will need to select the correct coding and then reload the text using
+@key{R}.
+
+
+@node Encrypted gopher connections, Gemini support, Gopher character encodings, Top
+@chapter Encrypted gopher connections
+
+While RFC 1436 does not broach the topic of encryption at all, several
+modern gopher servers can serve content over encrypted connections,
+and a common choice for this is TLS.
+
+Elpher can retrieve selectors using Emacs' built-in TLS support which
+uses the GnuTLS library. (It is possible to build emacs without
+GnuTLS, in which case encryption is not supported.)
+
+To retrieve documents using TLS, Elpher's TLS mode must be enabled.
+This can be directly toggled using @key{T}, but note that just as with
+the character encoding, changing this mode only affects subsequent
+connections.
+
+Alternatively, TLS mode is @emph{automatically} enabled whenever
+gopher URLs starting with @code{gophers://} are followed.
+
+The mode is sticky, so it remains active until switched off.
+It can also be automatically switched off when a TLS connection fails.
+In this case Elpher will prompt for your confirmation to ensure that
+you can't accidentally make a non-TLS connection.
+
+@node Gemini support, Finger support, Encrypted gopher connections, Top
+@chapter Gemini support
+
+@uref{gopher://gemini.circumlunar.space, Gemini}
+is a new protocol being developed by several members of
+gopherspace. It aims to solve some of the long-standing technical
+issues associated with gopher as a protocol, while keeping the major benefits.
+For instance, it _requires_ encrypted connections, it does away with
+the selector type, and allows servers to explicitly specify the
+character coding scheme used for text documents.
+
+The latest versions of Elpher aim to provide seamless transitions between
+gemini and gopher documents. Basically you should be able to open,
+bookmark, download and otherwise interact with gemini pages in exactly
+the same way as you do with other non-gemini pages. The only major
+difference from your perspective as a user is that you should no longer
+have to worry about manually toggling TLS on or off (for gemini it's
+always on), and you should never have to manually set a character coding
+scheme.
+
+The gemini protocol specification recommends a Trust on First Use (TOFU)
+behaviour when validating gemini server TLS certificates. This is
+because many gemini servers rely on self-signed certificates rather
+than certificates signed by a CA. Sadly however, this TOFU behaviour is
+far from straight-forward to configure using Emacs' existing Network
+Security Manager. For this reason, elpher defaults to performing no
+certificate verification by default. This behaviour can be easily
+customized by setting the @code{elpher-gemini-TLS-cert-checks}
+customization variable to non-nil.
+
+The gemini specification concerns both the protocol and a simple text
+document format (mimetype text/gemini) which is like a mixture between
+gophermap files and markdown-formatted files but simpler than both.
+Elpher renders gemini responses which are provided in this format in
+line with the rules in the spec. This includes wrapping long lines at
+word boundaries. The specific column at which this text is wrapped is
+defined by the customization variable
+@code{elpher-gemini-max-fill-width}, which is set to 80 columns by
+default. (This is slightly wider than Emacs' default fill width of 70
+columns due to the fact that there are a significant amount of older
+gemini content which, against the advice of the current spec, hard wraps
+at <80 columns. The larger default allows this to still look okay,
+while still keeping content without hard wraps looking pleasant.)
+
+The text/gemini format also possesses a section header syntax similar to
+markdown. Elpher allows different header levels to be drawn with
+different, customizable, faces. By default, on graphically-capable
+emacs systems, these faces are given different heights to distinguish
+among levels. On terminal systems, the level is indicated by the
+number of preceding # symbols.
+
+I should emphasize however that, while it is definitely functional,
+Elpher's gemini support is still experimental, and various aspects will
+change as the protocol develops further.
+
+@section Client Certificates for Gemini
+
+Gemini makes explicit use of the client certificate mechanism that TLS
+provides for allowing clients to authenticate themselves with servers.
+The Gemini specification suggests two distinct classes of client
+certificates: short-lived certificates used to identify you for a single
+session, and more permanent certificates used to identify you over a
+longer time period.
+
+When Elpher receives a request for a client certificate from a server,
+it will present you with the option to create and use a single-use
+``throwaway'' certificate, or to use a ``persistent''
+certificate (optionally creating it or installing pre-existing key and
+certificate files).
+
+Certificate creation in Elpher requires an installation of OpenSSL, and
+---in particular---that Elpher be able to run the @command{openssl} command-line
+utility. By default, Elpher assumes that the @command{openssl} is on the
+system path, but the precise location can be set by customizing the
+@code{elpher-openssl-command} variable.
+
+Each generated certificate results in the creation of a .key file and
+a .crt file. In the case of a throwaway certificate, these files are
+stored in the temporary directory indicated by the Emacs variable
+@code{temporary-file-directory} and are deleted when ``forgotten''
+(as described below).
+
+In the case of persistent certificates, these files are stored in the
+folder defined by the Elpher variable
+@code{elpher-certificate-directory}, and are never deleted by Elpher.
+(Of course you can delete them yourself whenever you like.)
+The base name of the files (i.e. sans extension) is what Elpher uses
+to identify the certificate.
+
+Using throwaway certificates is as simple as pressing the @key{t}
+key at the prompt which appears following a certificate request from
+a server. There is nothing more to do.
+
+Using a persistent certificate requires instead selecting @key{p} from the same
+menu. This will result in Elpher asking you for the name identifying
+the certificate. This entry autocompletes to the list of known certificate
+names, so you can use @key{TAB} to display the list.
+
+In the case that you choose a name that does not belong to the list of
+known certificates, Elpher will offer to create one for you or to
+``install'' one from existing key and certificate files.
+Pressing the @key{n} key will cause Elpher to begin the process of
+creating a new persistent certificate, using some additional
+details for which you will be prompted.
+Alternatively, pressing the @key{i} key will cause Elpher to ask for the
+locations of edisting key and certificate files to add to
+@code{elpher-certificate-directory} under the chosen name.
+
+Once a certificate is selected, it will be used for all subsequent TLS
+transactions to the host for which the certificate was created.
+It is immediately ``forgotten'' when a TLS connection to another host
+is attempted, or the following command is issued:
+
+@table @asis
+@keycmd{@key{F},elpher-forget-certificate}
+Causes Elpher to immediately forget any currently-loaded client certificate.
+@end table
+
+In either case, ``forgetting'' means that the details of the key and
+certificate file pair are erased from memory. Furthermore, in the case
+of throw-away certificates, the corresponding files are deleted.
+
+
+@node Finger support, Customization, Gemini support, Top
+@chapter Finger support
+
+Incidentally, Elpher has native support for querying finger servers.
+Of course, one could argue that this functionality is more easily
+provided by one's local telnet client. However finger URLs do appear
+on occasion in gopherspace, and it's nice to be able to open them
+in place.
+
+Elpher interprets @code{finger://} URLs as follows:
+
+@itemize
+
+@item
+The host is determined by the host name portion of the URL.
+
+@item
+In the case that the @emph{file name} portion of the URL is non-empty (besides
+the leading slash), this is interpreted as the user to finger.
+
+@item
+Otherwise, the @emph{user} portion of the URL is interpreted as the user to finger.
+
+@item
+If no user is provided, the root directory of the finger server is requested.
+
+@end itemize
+
+Thus @code{finger://user@@hostname} and @code{finger://hostname/user} are both equivalent.
+
+(The precedence of the /user notation over the user@ notation reflects a
+preference of the community.)
+
+@node Customization, Command Index, Finger support, Top
@chapter Customization
-@node Hacking, Index, Customization, Top
-@chapter Hacking
+Various parts of Elpher can be customized via the
+variables belonging to the elpher customization group, accessible
+using
+
+@example
+@kbd{M-x customize-group elpher @key{RET}}
+@end example
+
+@noindent This group contains a number of faces that can be modified to change
+the appearance of Elpher, including one face per menu item type.
+
+The group also contains variables for customizing the behaviour of
+Elpher. This includes how to open arbitrary (non-gopher) URLs, whether
+to display buffer headers, how to deal with ANSI escape sequences in
+text, the timeout to impose on network connections, and whether to
+prompt for confirmation when switching away from TLS.
+
+See the customization group itself for details.
-@node Index, , Hacking, Top
-@unnumbered Index
+@node Command Index, , Customization, Top
+@unnumbered Command Index
-@printindex cp
+@printindex fn
@bye
The Lambda Lab / projects / elpher.git / blobdiff