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")
  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   ;; If this key seq ends with a down event, discard the
 105   ;; following click or drag event.  Otherwise that would
 106   ;; erase the message.
 107   (let ((type (aref key (1- (length key)))))
 108     (if (listp type) (setq type (car type)))
 109     (and (symbolp type)
 110          (memq 'down (event-modifiers type))
 111          (read-event)))
 112   (let ((defn (key-binding key)))
 113     (if (or (null defn) (integerp defn))
 114         (message "%s is undefined" (key-description key))
 115       (message "%s runs the command %s"
 116                (key-description key)
 117                (if (symbolp defn) defn (prin1-to-string defn))))))
 118
 119 (defun print-help-return-message (&optional function)
 120   "Display or return message saying how to restore windows after help command.
 121 Computes a message and applies the optional argument FUNCTION to it.
 122 If FUNCTION is nil, applies `message' to it, thus printing it."
 123   (and (not (get-buffer-window standard-output))
 124        (funcall (or function 'message)
 125                 (concat
 126                  (substitute-command-keys
 127                   (if (one-window-p t)
 128                       (if pop-up-windows
 129                           "Type \\[delete-other-windows] to remove help window."
 130                         "Type \\[switch-to-buffer] RET to remove help window.")
 131                     "Type \\[switch-to-buffer-other-window] RET to restore the other window."))
 132                  (substitute-command-keys
 133                   "  \\[scroll-other-window] to scroll the help.")))))
 134
 135 (defun describe-key (key)
 136   "Display documentation of the function invoked by KEY.  KEY is a string."
 137   (interactive "kDescribe key: ")
 138   ;; If this key seq ends with a down event, discard the
 139   ;; following click or drag event.  Otherwise that would
 140   ;; erase the message.
 141   (let ((type (aref key (1- (length key)))))
 142     (if (listp type) (setq type (car type)))
 143     (and (symbolp type)
 144          (memq 'down (event-modifiers type))
 145          (read-event)))
 146   (let ((defn (key-binding key)))
 147     (if (or (null defn) (integerp defn))
 148         (message "%s is undefined" (key-description key))
 149       (with-output-to-temp-buffer "*Help*"
 150         (prin1 defn)
 151         (princ ":\n")
 152         (if (documentation defn)
 153             (princ (documentation defn))
 154           (princ "not documented"))
 155         (print-help-return-message)))))
 156
 157 (defun describe-mode (&optional minor)
 158   "Display documentation of current major mode.
 159 If optional MINOR is non-nil (or prefix argument is given if interactive),
 160 display documentation of active minor modes as well.
 161 For this to work correctly for a minor mode, the mode's indicator variable
 162 \(listed in `minor-mode-alist') must also be a function whose documentation
 163 describes the minor mode."
 164   (interactive)
 165   (with-output-to-temp-buffer "*Help*"
 166     (princ mode-name)
 167     (princ " Mode:\n")
 168     (princ (documentation major-mode))
 169     (let ((minor-modes minor-mode-alist)
 170           (locals (buffer-local-variables)))
 171       (while minor-modes
 172         (let* ((minor-mode (car (car minor-modes)))
 173                (indicator (car (cdr (car minor-modes))))
 174                (local-binding (assq minor-mode locals)))
 175           ;; Document a minor mode if it is listed in minor-mode-alist,
 176           ;; bound locally in this buffer, non-nil, and has a function
 177           ;; definition.
 178           (if (and local-binding
 179                    (cdr local-binding)
 180                    (fboundp minor-mode))
 181               (progn
 182                 (princ (format "\n\n\n%s minor mode (indicator%s):\n"
 183                                minor-mode indicator))
 184                 (princ (documentation minor-mode)))))
 185         (setq minor-modes (cdr minor-modes))))
 186     (print-help-return-message)))
 187
 188 ;; So keyboard macro definitions are documented correctly
 189 (fset 'defining-kbd-macro (symbol-function 'start-kbd-macro))
 190
 191 (defun describe-distribution ()
 192   "Display info on how to obtain the latest version of GNU Emacs."
 193   (interactive)
 194   (find-file-read-only
 195    (expand-file-name "DISTRIB" data-directory)))
 196
 197 (defun describe-copying ()
 198   "Display info on how you may redistribute copies of GNU Emacs."
 199   (interactive)
 200   (find-file-read-only
 201    (expand-file-name "COPYING" data-directory))
 202   (goto-char (point-min)))
 203
 204 (defun describe-no-warranty ()
 205   "Display info on all the kinds of warranty Emacs does NOT have."
 206   (interactive)
 207   (describe-copying)
 208   (let (case-fold-search)
 209     (search-forward "NO WARRANTY")
 210     (recenter 0)))
 211
 212 (defun describe-prefix-bindings ()
 213   "Describe the bindings of the prefix used to reach this command.
 214 The prefix described consists of all but the last event
 215 of the key sequence that ran this command."
 216   (interactive)
 217   (let* ((key (this-command-keys))
 218          (prefix (make-vector (1- (length key)) nil))
 219          i)
 220     (setq i 0)
 221     (while (< i (length prefix))
 222       (aset prefix i (aref key i))
 223       (setq i (1+ i)))
 224     (describe-bindings prefix)))
 225 ;; Make C-h after a prefix, when not specifically bound,
 226 ;; run describe-prefix-bindings.
 227 (setq prefix-help-command 'describe-prefix-bindings)
 228
 229 (defun view-emacs-news ()
 230   "Display info on recent changes to Emacs."
 231   (interactive)
 232   (find-file-read-only (expand-file-name "NEWS" data-directory)))
 233
 234 (defun view-lossage ()
 235   "Display last 100 input keystrokes."
 236   (interactive)
 237   (with-output-to-temp-buffer "*Help*"
 238     (princ (key-description (recent-keys)))
 239     (save-excursion
 240       (set-buffer standard-output)
 241       (goto-char (point-min))
 242       (while (progn (move-to-column 50) (not (eobp)))
 243         (search-forward " " nil t)
 244         (insert "\n")))
 245     (print-help-return-message)))
 246
 247 (make-help-screen help-for-help
 248   "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: "
 249   "You have typed \\[help-for-help], the help character.  Type a Help option:
 250
 251 a  command-apropos.   Give a substring, and see a list of commands
 252               (functions interactively callable) that contain
 253               that substring.  See also the  apropos  command.
 254 b  describe-bindings.  Display table of all key bindings.
 255 c  describe-key-briefly.  Type a command key sequence;
 256               it prints the function name that sequence runs.
 257 f  describe-function.  Type a function name and get documentation of it.
 258 i  info. The  info  documentation reader.
 259 k  describe-key.  Type a command key sequence;
 260               it displays the full documentation.
 261 l  view-lossage.  Shows last 100 characters you typed.
 262 m  describe-mode.  Print documentation of current major mode,
 263               which describes the commands peculiar to it.
 264 n  view-emacs-news.  Shows emacs news file.
 265 p  finder-by-keyword. Find packages matching a given topic keyword.
 266 s  describe-syntax.  Display contents of syntax table, plus explanations
 267 t  help-with-tutorial.  Select the Emacs learn-by-doing tutorial.
 268 v  describe-variable.  Type name of a variable;
 269               it displays the variable's documentation and value.
 270 w  where-is.  Type command name; it prints which keystrokes
 271               invoke that command.
 272 C-c print Emacs copying permission (General Public License).
 273 C-d print Emacs ordering information.
 274 C-n print news of recent Emacs changes.
 275 C-w print information on absence of warranty for GNU Emacs."
 276   help-map)
 277
 278 ;; Return a function which is called by the list containing point.
 279 ;; If that gives no function, return a function whose name is around point.
 280 ;; If that doesn't give a function, return nil.
 281 (defun function-called-at-point ()
 282   (or (condition-case ()
 283           (save-excursion
 284             (save-restriction
 285               (narrow-to-region (max (point-min) (- (point) 1000)) (point-max))
 286               (backward-up-list 1)
 287               (forward-char 1)
 288               (let (obj)
 289                 (setq obj (read (current-buffer)))
 290                 (and (symbolp obj) (fboundp obj) obj))))
 291         (error nil))
 292       (condition-case ()
 293           (save-excursion
 294             (forward-sexp -1)
 295             (skip-chars-forward "'")
 296             (let ((obj (read (current-buffer))))
 297               (and (symbolp obj) (fboundp obj) obj)))
 298         (error nil))))
 299
 300 (defun describe-function (function)
 301   "Display the full documentation of FUNCTION (a symbol)."
 302   (interactive
 303    (let ((fn (function-called-at-point))
 304          (enable-recursive-minibuffers t)
 305          val)
 306      (setq val (completing-read (if fn
 307                                     (format "Describe function (default %s): " fn)
 308                                   "Describe function: ")
 309                                 obarray 'fboundp t))
 310      (list (if (equal val "")
 311                fn (intern val)))))
 312   (with-output-to-temp-buffer "*Help*"
 313     (prin1 function)
 314     (princ ": ")
 315     (let* ((def (symbol-function function))
 316            (beg (if (commandp def) "an interactive " "a ")))
 317       (princ (cond ((or (stringp def)
 318                         (vectorp def))
 319                     "a keyboard macro.")
 320                    ((subrp def)
 321                     (concat beg "built-in function."))
 322                    ((byte-code-function-p def)
 323                     (concat beg "compiled Lisp function."))
 324                    ((symbolp def)
 325                     (format "alias for `%s'." def))
 326                    ((eq (car-safe def) 'lambda)
 327                     (concat beg "Lisp function."))
 328                    ((eq (car-safe def) 'macro)
 329                     "a Lisp macro.")
 330                    ((eq (car-safe def) 'mocklisp)
 331                     "a mocklisp function.")
 332                    ((eq (car-safe def) 'autoload)
 333                     (format "%s autoloaded Lisp %s."
 334                             (if (commandp def) "an interactive" "an")
 335                             (if (nth 4 def) "macro" "function")
 336 ;;; Including the file name made this line too long.
 337 ;;;                         (nth 1 def)
 338                             ))
 339                    (t "")))
 340       (terpri)
 341       (let ((arglist (cond ((byte-code-function-p def)
 342                             (car (append def nil)))
 343                            ((eq (car-safe def) 'lambda)
 344                             (nth 1 def))
 345                            (t t))))
 346         (if (listp arglist)
 347             (progn
 348               (princ (cons function
 349                            (mapcar (lambda (arg)
 350                                      (if (memq arg '(&optional &rest))
 351                                          arg
 352                                        (intern (upcase (symbol-name arg)))))
 353                                    arglist)))
 354               (terpri))))
 355       (if (documentation function)
 356           (progn (terpri)
 357                  (princ (documentation function)))
 358         (princ "not documented"))
 359       )
 360     (print-help-return-message)
 361     ;; Return the text we displayed.
 362     (save-excursion (set-buffer standard-output) (buffer-string))))
 363
 364 (defun variable-at-point ()
 365   (condition-case ()
 366       (save-excursion
 367         (forward-sexp -1)
 368         (skip-chars-forward "'")
 369         (let ((obj (read (current-buffer))))
 370           (and (symbolp obj) (boundp obj) obj)))
 371     (error nil)))
 372
 373 (defun describe-variable (variable)
 374   "Display the full documentation of VARIABLE (a symbol).
 375 Returns the documentation as a string, also."
 376   (interactive
 377    (let ((v (variable-at-point))
 378          (enable-recursive-minibuffers t)
 379          val)
 380      (setq val (completing-read (if v
 381                                     (format "Describe variable (default %s): " v)
 382                                   "Describe variable: ")
 383                                 obarray 'boundp t))
 384      (list (if (equal val "")
 385                v (intern val)))))
 386   (with-output-to-temp-buffer "*Help*"
 387     (prin1 variable)
 388     (princ "'s value is ")
 389     (if (not (boundp variable))
 390         (princ "void.")
 391       (prin1 (symbol-value variable)))
 392     (terpri) (terpri)
 393     (princ "Documentation:")
 394     (terpri)
 395     (let ((doc (documentation-property variable 'variable-documentation)))
 396       (if doc
 397           (princ (substitute-command-keys doc))
 398         (princ "not documented as a variable.")))
 399     (print-help-return-message)
 400     ;; Return the text we displayed.
 401     (save-excursion (set-buffer standard-output) (buffer-string))))
 402
 403 (defun command-apropos (string)
 404   "Like apropos but lists only symbols that are names of commands
 405 \(interactively callable functions).  Argument REGEXP is a regular expression
 406 that is matched against command symbol names.  Returns list of symbols and
 407 documentation found."
 408   (interactive "sCommand apropos (regexp): ")
 409   (let ((message
 410          (let ((standard-output (get-buffer-create "*Help*")))
 411            (print-help-return-message 'identity))))
 412     (if (apropos string t 'commandp)
 413         (and message (message message)))))
 414
 415 (defun locate-library (library &optional nosuffix)
 416   "Show the full path name of Emacs library LIBRARY.
 417 This command searches the directories in `load-path' like `M-x load-library'
 418 to find the file that `M-x load-library RET LIBRARY RET' would load.
 419 Optional second arg NOSUFFIX non-nil means don't add suffixes `.elc' or `.el'
 420 to the specified name LIBRARY (a la calling `load' instead of `load-library')."
 421   (interactive "sLocate library: ")
 422   (catch 'answer
 423     (mapcar
 424      '(lambda (dir)
 425         (mapcar
 426          '(lambda (suf)
 427             (let ((try (expand-file-name (concat library suf) dir)))
 428               (and (file-readable-p try)
 429                    (null (file-directory-p try))
 430                    (progn
 431                      (message "Library is file %s" try)
 432                      (throw 'answer try)))))
 433          (if nosuffix '("") '(".elc" ".el" ""))))
 434      load-path)
 435     (message "No library %s in search path" library)
 436     nil))
 437
 438 ;;; help.el ends here