lisp/help.el

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