@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2001,
-@c 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Free Software Foundation, Inc.
+@c Copyright (C) 1990-1995, 1998-1999, 2001-2014 Free Software
+@c Foundation, Inc.
@c See the file elisp.texi for copying conditions.
-@setfilename ../../info/help
-@node Documentation, Files, Modes, Top
+@node Documentation
@chapter Documentation
@cindex documentation strings
- GNU Emacs Lisp has convenient on-line help facilities, most of which
-derive their information from the documentation strings associated with
-functions and variables. This chapter describes how to write good
-documentation strings for your Lisp programs, as well as how to write
-programs to access documentation.
+ GNU Emacs has convenient built-in help facilities, most of which
+derive their information from documentation strings associated with
+functions and variables. This chapter describes how to access
+documentation strings in Lisp programs.
+
+ The contents of a documentation string should follow certain
+conventions. In particular, its first line should be a complete
+sentence (or two complete sentences) that briefly describes what the
+function or variable does. @xref{Documentation Tips}, for how to
+write good documentation strings.
Note that the documentation strings for Emacs are not the same thing
as the Emacs manual. Manuals have their own source files, written in
topics of discussion.
For commands to display documentation strings, see @ref{Help, ,
-Help, emacs, The GNU Emacs Manual}. For the conventions for writing
-documentation strings, see @ref{Documentation Tips}.
+Help, emacs, The GNU Emacs Manual}.
@menu
-* Documentation Basics:: Good style for doc strings.
- Where to put them. How Emacs stores them.
+* Documentation Basics:: Where doc strings are defined and stored.
* Accessing Documentation:: How Lisp programs can access doc strings.
* Keys in Documentation:: Substituting current key bindings.
* Describing Characters:: Making printable descriptions of
@end menu
@node Documentation Basics
-@comment node-name, next, previous, up
@section Documentation Basics
@cindex documentation conventions
@cindex writing a documentation string
@cindex string, writing a doc string
A documentation string is written using the Lisp syntax for strings,
-with double-quote characters surrounding the text of the string. This
-is because it really is a Lisp string object. The string serves as
-documentation when it is written in the proper place in the definition
-of a function or variable. In a function definition, the documentation
-string follows the argument list. In a variable definition, the
-documentation string follows the initial value of the variable.
-
- When you write a documentation string, make the first line a
-complete sentence (or two complete sentences) since some commands,
-such as @code{apropos}, show only the first line of a multi-line
-documentation string. Also, you should not indent the second line of
-a documentation string, if it has one, because that looks odd when you
-use @kbd{C-h f} (@code{describe-function}) or @kbd{C-h v}
-(@code{describe-variable}) to view the documentation string. There
-are many other conventions for doc strings; see @ref{Documentation
-Tips}.
-
- Documentation strings can contain several special substrings, which
-stand for key bindings to be looked up in the current keymaps when the
-documentation is displayed. This allows documentation strings to refer
-to the keys for related commands and be accurate even when a user
-rearranges the key bindings. (@xref{Keys in Documentation}.)
-
-@vindex emacs-lisp-docstring-fill-column
- Emacs Lisp mode fills documentation strings to the width
-specified by @code{emacs-lisp-docstring-fill-column}.
-
- In Emacs Lisp, a documentation string is accessible through the
-function or variable that it describes:
-
-@itemize @bullet
-@item
-@kindex function-documentation
-The documentation for a function is usually stored in the function
-definition itself (@pxref{Lambda Expressions}). The function
-@code{documentation} knows how to extract it. You can also put
-function documentation in the @code{function-documentation} property
-of the function name. That is useful with definitions such as
-keyboard macros that can't hold a documentation string.
-
-@item
-@kindex variable-documentation
-The documentation for a variable is stored in the variable's property
-list under the property name @code{variable-documentation}. The
-function @code{documentation-property} knows how to retrieve it.
-@end itemize
-
-@cindex @file{DOC-@var{version}} (documentation) file
-To save space, the documentation for preloaded functions and variables
-(including primitive functions and autoloaded functions) is stored in
-the file @file{emacs/etc/DOC-@var{version}}---not inside Emacs. The
-documentation strings for functions and variables loaded during the
-Emacs session from byte-compiled files are stored in those files
-(@pxref{Docs and Compilation}).
-
-The data structure inside Emacs has an integer offset into the file, or
-a list containing a file name and an integer, in place of the
-documentation string. The functions @code{documentation} and
-@code{documentation-property} use that information to fetch the
-documentation string from the appropriate file; this is transparent to
-the user.
-
-@c Wordy to prevent overfull hbox. --rjc 15mar92
- The @file{emacs/lib-src} directory contains two utilities that you can
-use to print nice-looking hardcopy for the file
-@file{emacs/etc/DOC-@var{version}}. These are @file{sorted-doc} and
-@file{digest-doc}.
+with double-quote characters surrounding the text. It is, in fact, an
+actual Lisp string. When the string appears in the proper place in a
+function or variable definition, it serves as the function's or
+variable's documentation.
+
+@cindex @code{function-documentation} property
+ In a function definition (a @code{lambda} or @code{defun} form), the
+documentation string is specified after the argument list, and is
+normally stored directly in the function object. @xref{Function
+Documentation}. You can also put function documentation in the
+@code{function-documentation} property of a function name
+(@pxref{Accessing Documentation}).
+
+@cindex @code{variable-documentation} property
+ In a variable definition (a @code{defvar} form), the documentation
+string is specified after the initial value. @xref{Defining
+Variables}. The string is stored in the variable's
+@code{variable-documentation} property.
+
+@cindex @file{DOC} (documentation) file
+ Sometimes, Emacs does not keep documentation strings in memory.
+There are two such circumstances. Firstly, to save memory, the
+documentation for preloaded functions and variables (including
+primitives) is kept in a file named @file{DOC}, in the directory
+specified by @code{doc-directory} (@pxref{Accessing Documentation}).
+Secondly, when a function or variable is loaded from a byte-compiled
+file, Emacs avoids loading its documentation string (@pxref{Docs and
+Compilation}). In both cases, Emacs looks up the documentation string
+from the file only when needed, such as when the user calls @kbd{C-h
+f} (@code{describe-function}) for a function.
+
+ Documentation strings can contain special @dfn{key substitution
+sequences}, referring to key bindings which are looked up only when
+the user views the documentation. This allows the help commands to
+display the correct keys even if a user rearranges the default key
+bindings. @xref{Keys in Documentation}.
+
+ In the documentation string of an autoloaded command
+(@pxref{Autoload}), these key-substitution sequences have an
+additional special effect: they cause @kbd{C-h f} on the command to
+trigger autoloading. (This is needed for correctly setting up the
+hyperlinks in the @file{*Help*} buffer.)
@node Accessing Documentation
@section Access to Documentation Strings
@defun documentation-property symbol property &optional verbatim
-This function returns the documentation string that is recorded in
-@var{symbol}'s property list under property @var{property}. It
-retrieves the text from a file if the value calls for that. If the
-property value isn't @code{nil}, isn't a string, and doesn't refer to
-text in a file, then it is evaluated to obtain a string.
-
-The last thing this function does is pass the string through
-@code{substitute-command-keys} to substitute actual key bindings,
-unless @var{verbatim} is non-@code{nil}.
+This function returns the documentation string recorded in
+@var{symbol}'s property list under property @var{property}. It is
+most often used to look up the documentation strings of variables, for
+which @var{property} is @code{variable-documentation}. However, it
+can also be used to look up other kinds of documentation, such as for
+customization groups (but for function documentation, use the
+@code{documentation} function, below).
+
+If the property value refers to a documentation string stored in the
+@file{DOC} file or a byte-compiled file, this function looks up that
+string and returns it.
+
+If the property value isn't @code{nil}, isn't a string, and doesn't
+refer to text in a file, then it is evaluated as a Lisp expression to
+obtain a string.
+
+Finally, this function passes the string through
+@code{substitute-command-keys} to substitute key bindings (@pxref{Keys
+in Documentation}). It skips this step if @var{verbatim} is
+non-@code{nil}.
@smallexample
@group
If @var{function} is a symbol, this function first looks for the
@code{function-documentation} property of that symbol; if that has a
non-@code{nil} value, the documentation comes from that value (if the
-value is not a string, it is evaluated). If @var{function} is not a
-symbol, or if it has no @code{function-documentation} property, then
-@code{documentation} extracts the documentation string from the actual
-function definition, reading it from a file if called for.
+value is not a string, it is evaluated).
-Finally, unless @var{verbatim} is non-@code{nil}, it calls
-@code{substitute-command-keys} so as to return a value containing the
-actual (current) key bindings.
+If @var{function} is not a symbol, or if it has no
+@code{function-documentation} property, then @code{documentation}
+extracts the documentation string from the actual function definition,
+reading it from a file if called for.
-The function @code{documentation} signals a @code{void-function} error
+Finally, unless @var{verbatim} is non-@code{nil}, this function calls
+@code{substitute-command-keys}. The result is the documentation
+string to return.
+
+The @code{documentation} function signals a @code{void-function} error
if @var{function} has no function definition. However, it is OK if
the function definition has no documentation string. In that case,
@code{documentation} returns @code{nil}.
face.
@end defun
-@c Wordy to prevent overfull hboxes. --rjc 15mar92
Here is an example of using the two functions, @code{documentation} and
@code{documentation-property}, to display the documentation strings for
-several symbols in a @samp{*Help*} buffer.
+several symbols in a @file{*Help*} buffer.
@anchor{describe-symbols example}
@smallexample
@group
(princ
(format "%s\t%s\n%s\n\n" s
- (if (user-variable-p s)
+ (if (custom-variable-p s)
"Option " "Variable")
@end group
@group
@end group
@end smallexample
-@defun Snarf-documentation filename
@anchor{Definition of Snarf-documentation}
-This function is used only during Emacs initialization, just before
-the runnable Emacs is dumped. It finds the file offsets of the
-documentation strings stored in the file @var{filename}, and records
-them in the in-core function definitions and variable property lists in
-place of the actual strings. @xref{Building Emacs}.
+@defun Snarf-documentation filename
+This function is used when building Emacs, just before the runnable
+Emacs is dumped. It finds the positions of the documentation strings
+stored in the file @var{filename}, and records those positions into
+memory in the function definitions and variable property lists.
+@xref{Building Emacs}.
Emacs reads the file @var{filename} from the @file{emacs/etc} directory.
When the dumped Emacs is later executed, the same file will be looked
for in the directory @code{doc-directory}. Usually @var{filename} is
-@code{"DOC-@var{version}"}.
+@code{"DOC"}.
@end defun
@defvar doc-directory
This variable holds the name of the directory which should contain the
-file @code{"DOC-@var{version}"} that contains documentation strings for
+file @code{"DOC"} that contains documentation strings for
built-in and preloaded functions and variables.
In most cases, this is the same as @code{data-directory}. They may be
@cindex documentation, keys in
@cindex keys in documentation strings
@cindex substituting keys in documentation
+@cindex key substitution sequence
When documentation strings refer to key sequences, they should use the
current, actual key bindings. They can do so using certain special text
replaces them by what they stand for, returning the result as a string.
This permits display of documentation that refers accurately to the
user's own customized key bindings.
+
+@cindex advertised binding
+If a command has multiple bindings, this function normally uses the
+first one it finds. You can specify one particular key binding by
+assigning an @code{:advertised-binding} symbol property to the
+command, like this:
+
+@smallexample
+(put 'undo :advertised-binding [?\C-/])
+@end smallexample
+
+@noindent
+The @code{:advertised-binding} property also affects the binding shown
+in menu items (@pxref{Menu Bar}). The property is ignored if it
+specifies a key binding that the command does not actually have.
@end defun
Here are examples of the special sequences:
Emacs notation for keyboard input. A normal printing character
appears as itself, but a control character turns into a string
starting with @samp{C-}, a meta character turns into a string starting
-with @samp{M-}, and space, tab, etc.@: appear as @samp{SPC},
+with @samp{M-}, and space, tab, etc., appear as @samp{SPC},
@samp{TAB}, etc. A function key symbol appears inside angle brackets
@samp{<@dots{}>}. An event that is a list appears as the name of the
symbol in the @sc{car} of the list, inside angle brackets.
@end smallexample
@end defun
-@defun read-kbd-macro string &optional need-vector
+@deffn Command read-kbd-macro string &optional need-vector
This function is used mainly for operating on keyboard macros, but it
can also be used as a rough inverse for @code{key-description}. You
call it with a string containing key descriptions, separated by spaces;
(This may or may not be a single valid key sequence, depending on what
events you use; @pxref{Key Sequences}.) If @var{need-vector} is
non-@code{nil}, the return value is always a vector.
-@end defun
+@end deffn
@node Help Functions
@section Help Functions
The function returns a list of elements that look like this:
@example
-(@var{symbol} @var{score} @var{fn-doc} @var{var-doc}
+(@var{symbol} @var{score} @var{function-doc} @var{variable-doc}
@var{plist-doc} @var{widget-doc} @var{face-doc} @var{group-doc})
@end example
Here, @var{score} is an integer measure of how important the symbol
-seems to be as a match, and the remaining elements are documentation
-strings for @var{symbol}'s various roles (or @code{nil}).
+seems to be as a match. Each of the remaining elements is a
+documentation string, or @code{nil}, for @var{symbol} as a function,
+variable, etc.
-It also displays the symbols in a buffer named @samp{*Apropos*}, each
+It also displays the symbols in a buffer named @file{*Apropos*}, each
with a one-line description taken from the beginning of its
documentation string.
@defopt help-event-list
The value of this variable is a list of event types that serve as
-alternative ``help characters.'' These events are handled just like the
+alternative ``help characters''. These events are handled just like the
event specified by @code{help-char}.
@end defopt
whenever the character @code{help-char} is read. If evaluating the form
produces a string, that string is displayed.
-A command that calls @code{read-event} or @code{read-char} probably
-should bind @code{help-form} to a non-@code{nil} expression while it
-does input. (The time when you should not do this is when @kbd{C-h} has
-some other meaning.) Evaluating this expression should result in a
-string that explains what the input is for and how to enter it properly.
+A command that calls @code{read-event}, @code{read-char-choice}, or
+@code{read-char} probably should bind @code{help-form} to a
+non-@code{nil} expression while it does input. (The time when you
+should not do this is when @kbd{C-h} has some other meaning.)
+Evaluating this expression should result in a string that explains
+what the input is for and how to enter it properly.
Entry to the minibuffer binds this variable to the value of
@code{minibuffer-help-form} (@pxref{Definition of minibuffer-help-form}).
variable's default value is @code{describe-prefix-bindings}.
@end defvar
-@defun describe-prefix-bindings
+@deffn Command describe-prefix-bindings
This function calls @code{describe-bindings} to display a list of all
the subcommands of the prefix key of the most recent key sequence. The
prefix described consists of all but the last event of that key
sequence. (The last event is, presumably, the help character.)
-@end defun
+@end deffn
The following two functions are meant for modes that want to provide
help without relinquishing control, such as the ``electric'' modes.
options)}, and then provides assistance in finding out what the key
bindings are, and what the mode is intended for. It returns @code{nil}.
+@vindex Helper-help-map
This can be customized by changing the map @code{Helper-help-map}.
@end deffn
@defun help-buffer
This function returns the name of the help buffer, which is normally
-@samp{*Help*}; if such a buffer does not exist, it is first created.
+@file{*Help*}; if such a buffer does not exist, it is first created.
@end defun
+@vindex help-window-select
@defmac with-help-window buffer-name body@dots{}
-This macro evaluates the @var{body} forms, inserting any output they
-produce into a buffer named @var{buffer-name} like
-@code{with-output-to-temp-buffer} (@pxref{Temporary Displays}).
-(Usually, @var{buffer-name} should be the value returned by the
-function @code{help-buffer}.) It also puts the specified buffer into
-Help mode and displays a message telling the user how to quit and
-scroll the help window.
+This macro evaluates @var{body} like @code{with-output-to-temp-buffer}
+(@pxref{Temporary Displays}), inserting any output produced by its forms
+into a buffer named @var{buffer-name}. (Usually, @var{buffer-name}
+should be the value returned by the function @code{help-buffer}.) It
+also puts the specified buffer into Help mode and displays a message
+telling the user how to quit and scroll the help window. It selects the
+help window if the current value of the user option
+@code{help-window-select} has been set accordingly. It returns the last
+value in @var{body}.
@end defmac
@defun help-setup-xref item interactive-p
-This function updates the cross reference data in the @samp{*Help*}
+This function updates the cross reference data in the @file{*Help*}
buffer, which is used to regenerate the help information when the user
clicks on the @samp{Back} or @samp{Forward} buttons. Most commands
-that use the @samp{*Help*} buffer should invoke this function before
+that use the @file{*Help*} buffer should invoke this function before
clearing the buffer. The @var{item} argument should have the form
-@code{(@var{funtion} . @var{args})}, where @var{funtion} is a function
+@code{(@var{function} . @var{args})}, where @var{function} is a function
to call, with argument list @var{args}, to regenerate the help buffer.
The @var{interactive-p} argument is non-@code{nil} if the calling
command was invoked interactively; in that case, the stack of items
-for the @samp{*Help*} buffer's @samp{Back} buttons is cleared.
+for the @file{*Help*} buffer's @samp{Back} buttons is cleared.
@end defun
@xref{describe-symbols example}, for an example of using
echo area at first, and display the longer @var{help-text} strings only
if the user types the help character again.
@end defopt
-
-@ignore
- arch-tag: ba36b4c2-e60f-49e2-bc25-61158fdcd815
-@end ignore
HCoop / bpt / emacs.git / blobdiff