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diff --git a/lispref/help.texi b/lispref/help.texi deleted file mode 100644 index 5b0b2f993ba..00000000000 --- a/lispref/help.texi +++ /dev/null @@ -1,627 +0,0 @@ -@c -*-texinfo-*- -@c This is part of the GNU Emacs Lisp Reference Manual. -@c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc. -@c See the file elisp.texi for copying conditions. -@setfilename ../info/help -@node Documentation, Files, Modes, Top -@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. - - Note that the documentation strings for Emacs are not the same thing -as the Emacs manual. Manuals have their own source files, written in -the Texinfo language; documentation strings are specified in the -definitions of the functions and variables they apply to. A collection -of documentation strings is not sufficient as a manual because a good -manual is not organized in that fashion; it is organized in terms of -topics of discussion. - -@menu -* Documentation Basics:: Good style for doc strings. - Where to put them. How Emacs stores them. -* Accessing Documentation:: How Lisp programs can access doc strings. -* Keys in Documentation:: Substituting current key bindings. -* Describing Characters:: Making printable descriptions of - non-printing characters and key sequences. -* Help Functions:: Subroutines used by Emacs help facilities. -@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 you have one, because that looks odd when you use @kbd{C-h f} -(@code{describe-function}) or @kbd{C-h v} (@code{describe-variable}). -@xref{Documentation Tips}. - - Documentation strings may 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{Accessing Documentation}.) - - Within the Lisp world, a documentation string accessible through the -function or variable that it describes: - -@itemize @bullet -@item -The documentation for a function is stored in the function definition -itself (@pxref{Lambda Expressions}). The function -@code{documentation} knows how to extract it. - -@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 extract it. -@end itemize - -@cindex @file{DOC} (documentation) file -@cindex @file{emacs/etc/DOC-@var{version}} -@cindex @file{etc/DOC-@var{version}} -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}}. The documentation for -functions and variables loaded during the Emacs session from -byte-compiled files is 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 string and an integer, in place of the documentation -string. The functions @code{documentation} and -@code{documentation-property} use that information to read the -documentation from the appropriate file; this is transparent to the -user. - - For information on the uses of documentation strings, see @ref{Help, , -Help, emacs, The GNU Emacs Manual}. - -@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.c} and -@file{digest-doc.c}. - -@node Accessing Documentation -@section Access to Documentation Strings - -@defun documentation-property symbol property &optional verbatim -This function returns the documentation string that is recorded -@var{symbol}'s property list under property @var{property}. It -retrieves the text from a file if necessary, and runs -@code{substitute-command-keys} to substitute actual key bindings. (This -substitution is not done if @var{verbatim} is non-@code{nil}; the -@var{verbatim} argument exists only as of Emacs 19.) - -@smallexample -@group -(documentation-property 'command-line-processed - 'variable-documentation) - @result{} "t once command line has been processed" -@end group -@group -(symbol-plist 'command-line-processed) - @result{} (variable-documentation 188902) -@end group -@end smallexample -@end defun - -@defun documentation function &optional verbatim -This function returns the documentation string of @var{function}. It -reads the text from a file if necessary. Then (unless @var{verbatim} is -non-@code{nil}) it calls @code{substitute-command-keys}, to return a -value containing the actual (current) key bindings. - -The function @code{documentation} 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}. -@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. - -@smallexample -@group -(defun describe-symbols (pattern) - "Describe the Emacs Lisp symbols matching PATTERN. -All symbols that have PATTERN in their name are described -in the `*Help*' buffer." - (interactive "sDescribe symbols matching: ") - (let ((describe-func - (function - (lambda (s) -@end group -@group - ;; @r{Print description of symbol.} - (if (fboundp s) ; @r{It is a function.} - (princ - (format "%s\t%s\n%s\n\n" s - (if (commandp s) - (let ((keys (where-is-internal s))) - (if keys - (concat - "Keys: " - (mapconcat 'key-description - keys " ")) - "Keys: none")) - "Function") -@end group -@group - (or (documentation s) - "not documented")))) - - (if (boundp s) ; @r{It is a variable.} -@end group -@group - (princ - (format "%s\t%s\n%s\n\n" s - (if (user-variable-p s) - "Option " "Variable") -@end group -@group - (or (documentation-property - s 'variable-documentation) - "not documented"))))))) - sym-list) -@end group - -@group - ;; @r{Build a list of symbols that match pattern.} - (mapatoms (function - (lambda (sym) - (if (string-match pattern (symbol-name sym)) - (setq sym-list (cons sym sym-list)))))) -@end group - -@group - ;; @r{Display the data.} - (with-output-to-temp-buffer "*Help*" - (mapcar describe-func (sort sym-list 'string<)) - (print-help-return-message)))) -@end group -@end smallexample - - The @code{describe-symbols} function works like @code{apropos}, -but provides more information. - -@smallexample -@group -(describe-symbols "goal") - ----------- Buffer: *Help* ---------- -goal-column Option -*Semipermanent goal column for vertical motion, as set by @dots{} -@end group -@c Do not blithely break or fill these lines. -@c That makes them incorrect. - -@group -set-goal-column Command: C-x C-n -Set the current horizontal position as a goal for C-n and C-p. -@end group -@c DO NOT put a blank line here! That is factually inaccurate! -@group -Those commands will move to this position in the line moved to -rather than trying to keep the same horizontal position. -With a non-nil argument, clears out the goal column -so that C-n and C-p resume vertical motion. -The goal column is stored in the variable `goal-column'. -@end group - -@group -temporary-goal-column Variable -Current goal column for vertical motion. -It is the column where point was -at the start of current run of vertical motion commands. -When the `track-eol' feature is doing its job, the value is 9999. ----------- Buffer: *Help* ---------- -@end group -@end smallexample - -@defun Snarf-documentation filename - 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}. - - Emacs finds the file @var{filename} in the @file{emacs/etc} directory. -When the dumped Emacs is later executed, the same file is found in the -directory @code{doc-directory}. Usually @var{filename} is -@code{"DOC-@var{version}"}. -@end defun - -@c Emacs 19 feature -@defvar doc-directory -This variable holds the name of the directory which should contion the -file @code{"DOC-@var{version}"} 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 -different when you run Emacs from the directory where you built it, -without actually installing it. See @code{data-directory} in @ref{Help -Functions}. - -In older Emacs versions, @code{exec-directory} was used for this. -@end defvar - -@node Keys in Documentation -@section Substituting Key Bindings in Documentation -@cindex documentation, keys in -@cindex keys in documentation strings -@cindex substituting keys in documentation - - When documentation strings refer to key sequences, they should use the -current, actual key bindings. They can do so using certain special text -sequences described below. Accessing documentation strings in the usual -way substitutes current key binding information for these special -sequences. This works by calling @code{substitute-command-keys}. You -can also call that function yourself. - - Here is a list of the special sequences and what they mean: - -@table @code -@item \[@var{command}] -stands for a key sequence that will invoke @var{command}, or @samp{M-x -@var{command}} if @var{command} has no key bindings. - -@item \@{@var{mapvar}@} -stands for a summary of the value of @var{mapvar}, which should be a -keymap. The summary is made by @code{describe-bindings}. - -@item \<@var{mapvar}> -stands for no text itself. It is used for a side effect: it specifies -@var{mapvar} as the keymap for any following @samp{\[@var{command}]} -sequences in this documentation string. - -@item \= -quotes the following character and is discarded; thus, @samp{\=\[} puts -@samp{\[} into the output, and @samp{\=\=} puts @samp{\=} into the -output. -@end table - -@strong{Please note:} Each @samp{\} must be doubled when written in a -string in Emacs Lisp. - -@defun substitute-command-keys string -This function scans @var{string} for the above special sequences and -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. -@end defun - - Here are examples of the special sequences: - -@smallexample -@group -(substitute-command-keys - "To abort recursive edit, type: \\[abort-recursive-edit]") -@result{} "To abort recursive edit, type: C-]" -@end group - -@group -(substitute-command-keys - "The keys that are defined for the minibuffer here are: - \\@{minibuffer-local-must-match-map@}") -@result{} "The keys that are defined for the minibuffer here are: -@end group - -? minibuffer-completion-help -SPC minibuffer-complete-word -TAB minibuffer-complete -LFD minibuffer-complete-and-exit -RET minibuffer-complete-and-exit -C-g abort-recursive-edit -" - -@group -(substitute-command-keys - "To abort a recursive edit from the minibuffer, type\ -\\<minibuffer-local-must-match-map>\\[abort-recursive-edit].") -@result{} "To abort a recursive edit from the minibuffer, type C-g." -@end group -@end smallexample - -@node Describing Characters -@section Describing Characters for Help Messages - - These functions convert events, key sequences or characters to textual -descriptions. These descriptions are useful for including arbitrary -text characters or key sequences in messages, because they convert -non-printing and whitespace characters to sequences of printing -characters. The description of a non-whitespace printing character is -the character itself. - -@defun key-description sequence -@cindex Emacs event standard notation -This function returns a string containing the Emacs standard notation -for the input events in @var{sequence}. The argument @var{sequence} may -be a string, vector or list. @xref{Input Events}, for more information -about valid events. See also the examples for -@code{single-key-description}, below. -@end defun - -@defun single-key-description event -@cindex event printing -@cindex character printing -@cindex control character printing -@cindex meta character printing -This function returns a string describing @var{event} in the standard -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, linefeed, etc.@: appear as @samp{SPC}, @samp{LFD}, etc. A -function key symbol appears as itself. An event that is a list appears -as the name of the symbol in the @sc{car} of the list. - -@smallexample -@group -(single-key-description ?\C-x) - @result{} "C-x" -@end group -@group -(key-description "\C-x \M-y \n \t \r \f123") - @result{} "C-x SPC M-y SPC LFD SPC TAB SPC RET SPC C-l 1 2 3" -@end group -@group -(single-key-description 'C-mouse-1) - @result{} "C-mouse-1" -@end group -@end smallexample -@end defun - -@defun text-char-description character -This function returns a string describing @var{character} in the -standard Emacs notation for characters that appear in text---like -@code{single-key-description}, except that control characters are -represented with a leading caret (which is how control characters in -Emacs buffers are usually displayed). - -@smallexample -@group -(text-char-description ?\C-c) - @result{} "^C" -@end group -@group -(text-char-description ?\M-m) - @result{} "M-m" -@end group -@group -(text-char-description ?\C-\M-m) - @result{} "M-^M" -@end group -@end smallexample -@end defun - -@node Help Functions -@section Help Functions - - Emacs provides a variety of on-line help functions, all accessible to -the user as subcommands of the prefix @kbd{C-h}. For more information -about them, see @ref{Help, , Help, emacs, The GNU Emacs Manual}. Here -we describe some program-level interfaces to the same information. - -@deffn Command apropos regexp &optional do-all predicate -This function finds all symbols whose names contain a match for the -regular expression @var{regexp}, and returns a list of them -(@pxref{Regular Expressions}). It also displays the symbols in a buffer -named @samp{*Help*}, each with a one-line description. - -@c Emacs 19 feature -If @var{do-all} is non-@code{nil}, then @code{apropos} also shows -key bindings for the functions that are found. - -If @var{predicate} is non-@code{nil}, it should be a function to be -called on each symbol that has matched @var{regexp}. Only symbols for -which @var{predicate} returns a non-@code{nil} value are listed or -displayed. - -In the first of the following examples, @code{apropos} finds all the -symbols with names containing @samp{exec}. In the second example, it -finds and returns only those symbols that are also commands. -(We don't show the output that results in the @samp{*Help*} buffer.) - -@smallexample -@group -(apropos "exec") - @result{} (Buffer-menu-execute command-execute exec-directory - exec-path execute-extended-command execute-kbd-macro - executing-kbd-macro executing-macro) -@end group - -@group -(apropos "exec" nil 'commandp) - @result{} (Buffer-menu-execute execute-extended-command) -@end group -@ignore -@group ----------- Buffer: *Help* ---------- -Buffer-menu-execute - Function: Save and/or delete buffers marked with - M-x Buffer-menu-save or M-x Buffer-menu-delete commands. -execute-extended-command ESC x - Function: Read function name, then read its - arguments and call it. ----------- Buffer: *Help* ---------- -@end group -@end ignore -@end smallexample - -The command @kbd{C-h a} (@code{command-apropos}) calls @code{apropos}, -but specifies a @var{predicate} to restrict the output to symbols that -are commands. The call to @code{apropos} looks like this: - -@smallexample -(apropos string t 'commandp) -@end smallexample -@end deffn - -@c Emacs 19 feature -@deffn Command super-apropos regexp &optional do-all -This function differs from @code{apropos} in that it searches -documentation strings as well as symbol names for matches for -@var{regexp}. By default, it searches the documentation strings only -for preloaded functions and variables. If @var{do-all} is -non-@code{nil}, it scans the names and documentation strings of all -functions and variables. -@end deffn - -@defvar help-map -The value of this variable is a local keymap for characters following the -Help key, @kbd{C-h}. -@end defvar - -@deffn {Prefix Command} help-command -This symbol is not a function; its function definition is actually the -keymap known as @code{help-map}. It is defined in @file{help.el} as -follows: - -@smallexample -@group -(define-key global-map "\C-h" 'help-command) -(fset 'help-command help-map) -@end group -@end smallexample -@end deffn - -@defun print-help-return-message &optional function -This function builds a string that explains how to restore the previous -state of the windows after a help command. After building the message, -it applies @var{function} to it if @var{function} is non-@code{nil}. -Otherwise it calls @code{message} to display it in the echo area. - -This function expects to be called inside a -@code{with-output-to-temp-buffer} special form, and expects -@code{standard-output} to have the value bound by that special form. -For an example of its use, see the long example in @ref{Accessing -Documentation}. -@end defun - -@defvar help-char -The value of this variable is the help character---the character that -Emacs recognizes as meaning Help. By default, it is 8, which is -@kbd{C-h}. When Emacs reads this character, if @code{help-form} is -non-@code{nil} Lisp expression, it evaluates that expression, and -displays the result in a window if it is a string. - -Usually the value of @code{help-form}'s value is @code{nil}. Then the -help character has no special meaning at the level of command input, and -it becomes part of a key sequence in the normal way. The standard key -binding of @kbd{C-h} is a prefix key for several general-purpose help -features. - -The help character is special after prefix keys, too. If it has no -binding as a subcommand of the prefix key, it runs -@code{describe-prefix-bindings}, which displays a list of all the -subcommands of the prefix key. -@end defvar - -@defvar help-form -If this variable is non-@code{nil}, its value is a form to evaluate -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 exception is when @kbd{C-h} is meaningful input.) -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{Minibuffer Misc}). -@end defvar - -@defvar prefix-help-command -This variable holds a function to print help for a prefix character. -The function is called when the user types a prefix key followed by the -help character, and the help character has no binding after that prefix. -The variable's default value is @code{describe-prefix-bindings}. -@end defvar - -@defun 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 - - The following two functions are found in the library @file{helper}. -They are for modes that want to provide help without relinquishing -control, such as the ``electric'' modes. You must load that library -with @code{(require 'helper)} in order to use them. Their names begin -with @samp{Helper} to distinguish them from the ordinary help functions. - -@deffn Command Helper-describe-bindings -This command pops up a window displaying a help buffer containing a -listing of all of the key bindings from both the local and global keymaps. -It works by calling @code{describe-bindings}. -@end deffn - -@deffn Command Helper-help -This command provides help for the current mode. It prompts the user -in the minibuffer with the message @samp{Help (Type ? for further -options)}, and then provides assistance in finding out what the key -bindings are, and what the mode is intended for. It returns @code{nil}. - -This can be customized by changing the map @code{Helper-help-map}. -@end deffn - -@c Emacs 19 feature -@defvar data-directory -This variable holds the name of the directory in which Emacs finds -certain documentation and text files that come with Emacs. In older -Emacs versions, @code{exec-directory} was used for this. -@end defvar - -@c Emacs 19 feature -@defmac make-help-screen fname help-line help-text help-map -This macro defines a help command named @var{fname} that acts like a -prefix key that shows a list of the subcommands it offers. - -When invoked, @var{fname} displays @var{help-text} in a window, then -reads and executes a key sequence according to @var{help-map}. The -string @var{help-text} should describe the bindings available in -@var{help-map}. - -The command @var{fname} is defined to handle a few events itself, by -scrolling the display of @var{help-text}. When @var{fname} reads one of -those special events, it does the scrolling and then reads another -event. When it reads an event that is not one of those few, and which -has a binding in @var{help-map}, it executes that key's binding and -then returns. - -The argument @var{help-line} should be a single-line summary of the -alternatives in @var{help-map}. In the current version of Emacs, this -argument is used only if you set the option @code{three-step-help} to -@code{t}. -@end defmac - -@defopt three-step-help -If this variable is non-@code{nil}, commands defined with -@code{make-help-screen} display their @var{help-line} strings in the -echo area at first, and display the longer @var{help-text} strings only -if the user types the help character again. -@end defopt |