lisp/help.el

   1 ;;; help.el --- help commands for Emacs
   2
   3 ;; Copyright (C) 1985, 1986, 1993 Free Software Foundation, Inc.
   4
   5 ;; Maintainer: FSF
   6 ;; Keywords: help, internal
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software; you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation; either version 2, or (at your option)
  13 ;; any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs; see the file COPYING.  If not, write to
  22 ;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  23
  24 ;;; Commentary:
  25
  26 ;; This code implements GNU Emac's on-line help system, the one invoked by
  27 ;;`M-x help-for-help'.
  28
  29 ;;; Code:
  30
  31 ;; Get the macro make-help-screen when this is compiled,
  32 ;; or run interpreted, but not when the compiled code is loaded.
  33 (eval-when-compile (require 'help-macro))
  34
  35 (defvar help-map (make-sparse-keymap)
  36   "Keymap for characters following the Help key.")
  37
  38 (define-key global-map (char-to-string help-char) 'help-command)
  39 (fset 'help-command help-map)
  40
  41 (define-key help-map (char-to-string help-char) 'help-for-help)
  42 (define-key help-map "?" 'help-for-help)
  43
  44 (define-key help-map "\C-c" 'describe-copying)
  45 (define-key help-map "\C-d" 'describe-distribution)
  46 (define-key help-map "\C-w" 'describe-no-warranty)
  47 (define-key help-map "a" 'command-apropos)
  48
  49 (define-key help-map "b" 'describe-bindings)
  50
  51 (define-key help-map "c" 'describe-key-briefly)
  52 (define-key help-map "k" 'describe-key)
  53
  54 (define-key help-map "d" 'describe-function)
  55 (define-key help-map "f" 'describe-function)
  56
  57 (define-key help-map "i" 'info)
  58 (define-key help-map "\C-f" 'Info-goto-emacs-command-node)
  59 (define-key help-map "\C-k" 'Info-goto-emacs-key-command-node)
  60
  61 (define-key help-map "l" 'view-lossage)
  62
  63 (define-key help-map "m" 'describe-mode)
  64
  65 (define-key help-map "\C-n" 'view-emacs-news)
  66 (define-key help-map "n" 'view-emacs-news)
  67
  68 (define-key help-map "p" 'finder-by-keyword)
  69 (autoload 'finder-by-keyword "finder.el")
  70
  71 (define-key help-map "s" 'describe-syntax)
  72
  73 (define-key help-map "t" 'help-with-tutorial)
  74
  75 (define-key help-map "w" 'where-is)
  76
  77 (define-key help-map "v" 'describe-variable)
  78
  79 (defun help-with-tutorial ()
  80   "Select the Emacs learn-by-doing tutorial."
  81   (interactive)
  82   (let ((file (expand-file-name "~/TUTORIAL")))
  83     (delete-other-windows)
  84     (if (get-file-buffer file)
  85         (switch-to-buffer (get-file-buffer file))
  86       (switch-to-buffer (create-file-buffer file))
  87       (setq buffer-file-name file)
  88       (setq default-directory (expand-file-name "~/"))
  89       (setq buffer-auto-save-file-name nil)
  90       (insert-file-contents (expand-file-name "TUTORIAL" data-directory))
  91       (goto-char (point-min))
  92       (search-forward "\n<<")
  93       (beginning-of-line)
  94       (delete-region (point) (progn (end-of-line) (point)))
  95       (newline (- (window-height (selected-window))
  96                   (count-lines (point-min) (point))
  97                   6))
  98       (goto-char (point-min))
  99       (set-buffer-modified-p nil))))
 100
 101 (defun describe-key-briefly (key)
 102   "Print the name of the function KEY invokes.  KEY is a string."
 103   (interactive "kDescribe key briefly: ")
 104   (let ((defn (key-binding key)))
 105     (if (or (null defn) (integerp defn))
 106         (message "%s is undefined" (key-description key))
 107       (message "%s runs the command %s"
 108                (key-description key)
 109                (if (symbolp defn) defn (prin1-to-string defn))))))
 110
 111 (defun print-help-return-message (&optional function)
 112   "Display or return message saying how to restore windows after help command.
 113 Computes a message and applies the optional argument FUNCTION to it.
 114 If FUNCTION is nil, applies `message' to it, thus printing it."
 115   (and (not (get-buffer-window standard-output))
 116        (funcall (or function 'message)
 117                 (concat
 118                  (substitute-command-keys
 119                   (if (one-window-p t)
 120                       (if pop-up-windows
 121                           "Type \\[delete-other-windows] to remove help window."
 122                         "Type \\[switch-to-buffer] RET to remove help window.")
 123                     "Type \\[switch-to-buffer-other-window] RET to restore the other window."))
 124                  (substitute-command-keys
 125                   "  \\[scroll-other-window] to scroll the help.")))))
 126
 127 (defun describe-key (key)
 128   "Display documentation of the function invoked by KEY.  KEY is a string."
 129   (interactive "kDescribe key: ")
 130   (let ((defn (key-binding key)))
 131     (if (or (null defn) (integerp defn))
 132         (message "%s is undefined" (key-description key))
 133       (with-output-to-temp-buffer "*Help*"
 134         (prin1 defn)
 135         (princ ":\n")
 136         (if (documentation defn)
 137             (princ (documentation defn))
 138           (princ "not documented"))
 139         (print-help-return-message)))))
 140
 141 (defun describe-mode (&optional minor)
 142   "Display documentation of current major mode.
 143 If optional MINOR is non-nil (or prefix argument is given if interactive),
 144 display documentation of active minor modes as well.
 145 For this to work correctly for a minor mode, the mode's indicator variable
 146 (listed in `minor-mode-alist') must also be a function whose documentation
 147 describes the minor mode."
 148   (interactive)
 149   (with-output-to-temp-buffer "*Help*"
 150     (princ mode-name)
 151     (princ " Mode:\n")
 152     (princ (documentation major-mode))
 153     (let ((minor-modes minor-mode-alist)
 154           (locals (buffer-local-variables)))
 155       (while minor-modes
 156         (let* ((minor-mode (car (car minor-modes)))
 157                (indicator (car (cdr (car minor-modes))))
 158                (local-binding (assq minor-mode locals)))
 159           ;; Document a minor mode if it is listed in minor-mode-alist,
 160           ;; bound locally in this buffer, non-nil, and has a function
 161           ;; definition.
 162           (if (and local-binding
 163                    (cdr local-binding)
 164                    (fboundp minor-mode))
 165               (progn
 166                 (princ (format "\n\n\n%s minor mode (indicator%s):\n"
 167                                minor-mode indicator))
 168                 (princ (documentation minor-mode)))))
 169         (setq minor-modes (cdr minor-modes))))
 170     (print-help-return-message)))
 171
 172 ;; So keyboard macro definitions are documented correctly
 173 (fset 'defining-kbd-macro (symbol-function 'start-kbd-macro))
 174
 175 (defun describe-distribution ()
 176   "Display info on how to obtain the latest version of GNU Emacs."
 177   (interactive)
 178   (find-file-read-only
 179    (expand-file-name "DISTRIB" data-directory)))
 180
 181 (defun describe-copying ()
 182   "Display info on how you may redistribute copies of GNU Emacs."
 183   (interactive)
 184   (find-file-read-only
 185    (expand-file-name "COPYING" data-directory))
 186   (goto-char (point-min)))
 187
 188 (defun describe-no-warranty ()
 189   "Display info on all the kinds of warranty Emacs does NOT have."
 190   (interactive)
 191   (describe-copying)
 192   (let (case-fold-search)
 193     (search-forward "NO WARRANTY")
 194     (recenter 0)))
 195
 196 (defun view-emacs-news ()
 197   "Display info on recent changes to Emacs."
 198   (interactive)
 199   (find-file-read-only (expand-file-name "NEWS" data-directory)))
 200
 201 (defun view-lossage ()
 202   "Display last 100 input keystrokes."
 203   (interactive)
 204   (with-output-to-temp-buffer "*Help*"
 205     (princ (key-description (recent-keys)))
 206     (save-excursion
 207       (set-buffer standard-output)
 208       (goto-char (point-min))
 209       (while (progn (move-to-column 50) (not (eobp)))
 210         (search-forward " " nil t)
 211         (insert "\n")))
 212     (print-help-return-message)))
 213
 214 (make-help-screen help-for-help
 215   "a b c f i k l m n p s t v w C-c C-d C-n C-w.  Type \\[help-for-help] again for more help: "
 216   "You have typed \\[help-for-help], the help character.  Type a Help option:
 217
 218 a  command-apropos.   Give a substring, and see a list of commands
 219               (functions interactively callable) that contain
 220               that substring.  See also the  apropos  command.
 221 b  describe-bindings.  Display table of all key bindings.
 222 c  describe-key-briefly.  Type a command key sequence;
 223               it prints the function name that sequence runs.
 224 f  describe-function.  Type a function name and get documentation of it.
 225 i  info. The  info  documentation reader.
 226 k  describe-key.  Type a command key sequence;
 227               it displays the full documentation.
 228 l  view-lossage.  Shows last 100 characters you typed.
 229 m  describe-mode.  Print documentation of current major mode,
 230               which describes the commands peculiar to it.
 231 n  view-emacs-news.  Shows emacs news file.
 232 p  finder-by-keyword. Find packages matching a given topic keyword.
 233 s  describe-syntax.  Display contents of syntax table, plus explanations
 234 t  help-with-tutorial.  Select the Emacs learn-by-doing tutorial.
 235 v  describe-variable.  Type name of a variable;
 236               it displays the variable's documentation and value.
 237 w  where-is.  Type command name; it prints which keystrokes
 238               invoke that command.
 239 C-c print Emacs copying permission (General Public License).
 240 C-d print Emacs ordering information.
 241 C-n print news of recent Emacs changes.
 242 C-w print information on absence of warranty for GNU Emacs."
 243   help-map)
 244
 245 ;; Return a function which is called by the list containing point.
 246 ;; If that gives no function, return a function whose name is around point.
 247 ;; If that doesn't give a function, return nil.
 248 (defun function-called-at-point ()
 249   (or (condition-case ()
 250           (save-excursion
 251             (save-restriction
 252               (narrow-to-region (max (point-min) (- (point) 1000)) (point-max))
 253               (backward-up-list 1)
 254               (forward-char 1)
 255               (let (obj)
 256                 (setq obj (read (current-buffer)))
 257                 (and (symbolp obj) (fboundp obj) obj))))
 258         (error nil))
 259       (condition-case ()
 260           (save-excursion
 261             (forward-sexp -1)
 262             (skip-chars-forward "'")
 263             (let ((obj (read (current-buffer))))
 264               (and (symbolp obj) (fboundp obj) obj)))
 265         (error nil))))
 266
 267 (defun describe-function (function)
 268   "Display the full documentation of FUNCTION (a symbol)."
 269   (interactive
 270    (let ((fn (function-called-at-point))
 271          (enable-recursive-minibuffers t)
 272          val)
 273      (setq val (completing-read (if fn
 274                                     (format "Describe function (default %s): " fn)
 275                                   "Describe function: ")
 276                                 obarray 'fboundp t))
 277      (list (if (equal val "")
 278                fn (intern val)))))
 279   (with-output-to-temp-buffer "*Help*"
 280     (prin1 function)
 281     (princ ": ")
 282     (let* ((def (symbol-function function))
 283            (beg (if (commandp def) "an interactive " "a ")))
 284       (princ (cond ((or (stringp def)
 285                         (vectorp def))
 286                     "a keyboard macro.")
 287                    ((subrp def)
 288                     (concat beg "built-in function."))
 289                    ((byte-code-function-p def)
 290                     (concat beg "compiled Lisp function."))
 291                    ((symbolp def)
 292                     (format "alias for `%s'." def))
 293                    ((eq (car-safe def) 'lambda)
 294                     (concat beg "Lisp function."))
 295                    ((eq (car-safe def) 'macro)
 296                     "a Lisp macro.")
 297                    ((eq (car-safe def) 'mocklisp)
 298                     "a mocklisp function.")
 299                    ((eq (car-safe def) 'autoload)
 300                     (format "%s autoloaded Lisp %s."
 301                             (if (commandp def) "an interactive" "an")
 302                             (if (nth 4 def) "macro" "function")
 303 ;;; Including the file name made this line too long.
 304 ;;;                         (nth 1 def)
 305                             ))
 306                    (t "")))
 307       (terpri)
 308       (let ((arglist (cond ((byte-code-function-p def)
 309                             (car (append def nil)))
 310                            ((eq (car-safe def) 'lambda)
 311                             (nth 1 def))
 312                            (t t))))
 313         (if (listp arglist)
 314             (progn
 315               (princ (cons function
 316                            (mapcar (lambda (arg)
 317                                      (if (memq arg '(&optional &rest))
 318                                          arg
 319                                        (intern (upcase (symbol-name arg)))))
 320                                    arglist)))
 321               (terpri))))
 322       (if (documentation function)
 323           (progn (terpri)
 324                  (princ (documentation function)))
 325         (princ "not documented"))
 326       )
 327     (print-help-return-message)
 328     ;; Return the text we displayed.
 329     (save-excursion (set-buffer standard-output) (buffer-string))))
 330
 331 (defun variable-at-point ()
 332   (condition-case ()
 333       (save-excursion
 334         (forward-sexp -1)
 335         (skip-chars-forward "'")
 336         (let ((obj (read (current-buffer))))
 337           (and (symbolp obj) (boundp obj) obj)))
 338     (error nil)))
 339
 340 (defun describe-variable (variable)
 341   "Display the full documentation of VARIABLE (a symbol).
 342 Returns the documentation as a string, also."
 343   (interactive
 344    (let ((v (variable-at-point))
 345          (enable-recursive-minibuffers t)
 346          val)
 347      (setq val (completing-read (if v
 348                                     (format "Describe variable (default %s): " v)
 349                                   "Describe variable: ")
 350                                 obarray 'boundp t))
 351      (list (if (equal val "")
 352                v (intern val)))))
 353   (with-output-to-temp-buffer "*Help*"
 354     (prin1 variable)
 355     (princ "'s value is ")
 356     (if (not (boundp variable))
 357         (princ "void.")
 358       (prin1 (symbol-value variable)))
 359     (terpri) (terpri)
 360     (princ "Documentation:")
 361     (terpri)
 362     (let ((doc (documentation-property variable 'variable-documentation)))
 363       (if doc
 364           (princ (substitute-command-keys doc))
 365         (princ "not documented as a variable.")))
 366     (print-help-return-message)
 367     ;; Return the text we displayed.
 368     (save-excursion (set-buffer standard-output) (buffer-string))))
 369
 370 (defun command-apropos (string)
 371   "Like apropos but lists only symbols that are names of commands
 372 \(interactively callable functions).  Argument REGEXP is a regular expression
 373 that is matched against command symbol names.  Returns list of symbols and
 374 documentation found."
 375   (interactive "sCommand apropos (regexp): ")
 376   (let ((message
 377          (let ((standard-output (get-buffer-create "*Help*")))
 378            (print-help-return-message 'identity))))
 379     (if (apropos string t 'commandp)
 380         (and message (message message)))))
 381
 382 (defun locate-library (library &optional nosuffix)
 383   "Show the full path name of Emacs library LIBRARY.
 384 This command searches the directories in `load-path' like `M-x load-library'
 385 to find the file that `M-x load-library RET LIBRARY RET' would load.
 386 Optional second arg NOSUFFIX non-nil means don't add suffixes `.elc' or `.el'
 387 to the specified name LIBRARY (a la calling `load' instead of `load-library')."
 388   (interactive "sLocate library: ")
 389   (catch 'answer
 390     (mapcar
 391      '(lambda (dir)
 392         (mapcar
 393          '(lambda (suf)
 394             (let ((try (expand-file-name (concat library suf) dir)))
 395               (and (file-readable-p try)
 396                    (null (file-directory-p try))
 397                    (progn
 398                      (message "Library is file %s" try)
 399                      (throw 'answer try)))))
 400          (if nosuffix '("") '(".elc" ".el" ""))))
 401      load-path)
 402     (message "No library %s in search path" library)
 403     nil))
 404
 405 ;;; help.el ends here