lisp/help.el

   1 ;;; help.el --- help commands for Emacs
   2
   3 ;; Copyright (C) 1985, 1986, 1993, 1994 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 "\C-p" 'describe-project)
  48 (define-key help-map "a" 'command-apropos)
  49
  50 (define-key help-map "b" 'describe-bindings)
  51
  52 (define-key help-map "c" 'describe-key-briefly)
  53 (define-key help-map "k" 'describe-key)
  54
  55 (define-key help-map "d" 'describe-function)
  56 (define-key help-map "f" 'describe-function)
  57
  58 (define-key help-map "i" 'info)
  59 (define-key help-map "\C-f" 'Info-goto-emacs-command-node)
  60 (define-key help-map "\C-k" 'Info-goto-emacs-key-command-node)
  61
  62 (define-key help-map "l" 'view-lossage)
  63
  64 (define-key help-map "m" 'describe-mode)
  65
  66 (define-key help-map "\C-n" 'view-emacs-news)
  67 (define-key help-map "n" 'view-emacs-news)
  68
  69 (define-key help-map "p" 'finder-by-keyword)
  70 (autoload 'finder-by-keyword "finder"
  71   "Find packages matching a given keyword." t)
  72
  73 (define-key help-map "s" 'describe-syntax)
  74
  75 (define-key help-map "t" 'help-with-tutorial)
  76
  77 (define-key help-map "w" 'where-is)
  78
  79 (define-key help-map "v" 'describe-variable)
  80
  81 (define-key help-map "q" 'help-quit)
  82
  83 (defun help-quit ()
  84   (interactive)
  85   nil)
  86
  87 (defun help-with-tutorial ()
  88   "Select the Emacs learn-by-doing tutorial."
  89   (interactive)
  90   (let ((file (expand-file-name "~/TUTORIAL")))
  91     (delete-other-windows)
  92     (if (get-file-buffer file)
  93         (switch-to-buffer (get-file-buffer file))
  94       (switch-to-buffer (create-file-buffer file))
  95       (setq buffer-file-name file)
  96       (setq default-directory (expand-file-name "~/"))
  97       (setq buffer-auto-save-file-name nil)
  98       (insert-file-contents (expand-file-name "TUTORIAL" data-directory))
  99       (goto-char (point-min))
 100       (search-forward "\n<<")
 101       (beginning-of-line)
 102       (delete-region (point) (progn (end-of-line) (point)))
 103       (let ((n (- (window-height (selected-window))
 104                   (count-lines (point-min) (point))
 105                   6)))
 106         (if (< n 12)
 107             (newline n)
 108           ;; Some people get confused by the large gap.
 109           (newline (/ n 2))
 110           (insert "[Middle of page left blank for didactic purposes.  "
 111                   "Text continues below]")
 112           (newline (- n (/ n 2)))))
 113       (goto-char (point-min))
 114       (set-buffer-modified-p nil))))
 115
 116 (defun describe-key-briefly (key)
 117   "Print the name of the function KEY invokes.  KEY is a string."
 118   (interactive "kDescribe key briefly: ")
 119   ;; If this key seq ends with a down event, discard the
 120   ;; following click or drag event.  Otherwise that would
 121   ;; erase the message.
 122   (let ((type (aref key (1- (length key)))))
 123     (if (listp type) (setq type (car type)))
 124     (and (symbolp type)
 125          (memq 'down (event-modifiers type))
 126          (read-event)))
 127   (let ((defn (key-binding key)))
 128     (if (or (null defn) (integerp defn))
 129         (message "%s is undefined" (key-description key))
 130       (message "%s runs the command %s"
 131                (key-description key)
 132                (if (symbolp defn) defn (prin1-to-string defn))))))
 133
 134 (defun print-help-return-message (&optional function)
 135   "Display or return message saying how to restore windows after help command.
 136 Computes a message and applies the optional argument FUNCTION to it.
 137 If FUNCTION is nil, applies `message' to it, thus printing it."
 138   (and (not (get-buffer-window standard-output))
 139        (let ((first-message
 140               (cond ((or (member (buffer-name standard-output)
 141                                  special-display-buffer-names)
 142                          (assoc (buffer-name standard-output)
 143                                 special-display-buffer-names)
 144                          (let (found
 145                                (tail special-display-regexps)
 146                                (name (buffer-name standard-output)))
 147                            (while (and tail (not found))
 148                              (if (or (and (consp (car taiul))
 149                                           (string-match (car (car tail)) name))
 150                                      (and (stringp (car tail))
 151                                           (string-match (car tail) name)))
 152                                  (setq found t))
 153                              (setq tail (cdr tail)))
 154                            found))
 155                      ;; If the help output buffer is a special display buffer,
 156                      ;; don't say anything about how to get rid of it.
 157                      ;; First of all, the user will do that with the window
 158                      ;; manager, not with Emacs.
 159                      ;; Secondly, the buffer has not been displayed yet,
 160                      ;; so we don't know whether its frame will be selected.
 161                      ;; Even the message about scrolling the help
 162                      ;; might be wrong, but it seems worth showing it anyway.
 163                      nil)
 164                     ((not (one-window-p t))
 165                      "Type \\[switch-to-buffer-other-window] RET to restore the other window.")
 166                     (pop-up-windows
 167                      "Type \\[delete-other-windows] to remove help window.")
 168                     (t
 169                      "Type \\[switch-to-buffer] RET to remove help window."))))
 170          (funcall (or function 'message)
 171                   (concat
 172                    (if first-message
 173                        (substitute-command-keys first-message)
 174                      "")
 175                    (if first-message "  " "")
 176                    (substitute-command-keys
 177                     "\\[scroll-other-window] to scroll the help."))))))
 178
 179 (defun describe-key (key)
 180   "Display documentation of the function invoked by KEY.  KEY is a string."
 181   (interactive "kDescribe key: ")
 182   ;; If this key seq ends with a down event, discard the
 183   ;; following click or drag event.  Otherwise that would
 184   ;; erase the message.
 185   (let ((type (aref key (1- (length key)))))
 186     (if (listp type) (setq type (car type)))
 187     (and (symbolp type)
 188          (memq 'down (event-modifiers type))
 189          (read-event)))
 190   (let ((defn (key-binding key)))
 191     (if (or (null defn) (integerp defn))
 192         (message "%s is undefined" (key-description key))
 193       (with-output-to-temp-buffer "*Help*"
 194         (prin1 defn)
 195         (princ ":\n")
 196         (if (documentation defn)
 197             (princ (documentation defn))
 198           (princ "not documented"))
 199         (print-help-return-message)))))
 200
 201 (defun describe-mode ()
 202   "Display documentation of current major mode and minor modes.
 203 For this to work correctly for a minor mode, the mode's indicator variable
 204 \(listed in `minor-mode-alist') must also be a function whose documentation
 205 describes the minor mode."
 206   (interactive)
 207   (with-output-to-temp-buffer "*Help*"
 208     (let ((minor-modes minor-mode-alist)
 209           (locals (buffer-local-variables)))
 210       (while minor-modes
 211         (let* ((minor-mode (car (car minor-modes)))
 212                (indicator (car (cdr (car minor-modes))))
 213                (local-binding (assq minor-mode locals)))
 214           ;; Document a minor mode if it is listed in minor-mode-alist,
 215           ;; bound locally in this buffer, non-nil, and has a function
 216           ;; definition.
 217           (if (and local-binding
 218                    (cdr local-binding)
 219                    (fboundp minor-mode))
 220               (let ((pretty-minor-mode minor-mode))
 221                 (if (string-match "-mode$" (symbol-name minor-mode))
 222                     (setq pretty-minor-mode
 223                           (capitalize
 224                            (substring (symbol-name minor-mode)
 225                                       0 (match-beginning 0)))))
 226                 (while (and indicator (symbolp indicator))
 227                   (setq indicator (symbol-value indicator)))
 228                 (princ (format "%s minor mode (indicator%s):\n"
 229                                pretty-minor-mode indicator))
 230                 (princ (documentation minor-mode))
 231                 (princ "\n\n"))))
 232         (setq minor-modes (cdr minor-modes))))
 233     (princ mode-name)
 234     (princ " mode:\n")
 235     (princ (documentation major-mode))
 236     (print-help-return-message)))
 237
 238 ;; So keyboard macro definitions are documented correctly
 239 (fset 'defining-kbd-macro (symbol-function 'start-kbd-macro))
 240
 241 (defun describe-distribution ()
 242   "Display info on how to obtain the latest version of GNU Emacs."
 243   (interactive)
 244   (find-file-read-only
 245    (expand-file-name "DISTRIB" data-directory)))
 246
 247 (defun describe-copying ()
 248   "Display info on how you may redistribute copies of GNU Emacs."
 249   (interactive)
 250   (find-file-read-only
 251    (expand-file-name "COPYING" data-directory))
 252   (goto-char (point-min)))
 253
 254 (defun describe-project ()
 255   "Display info on the GNU project."
 256   (interactive)
 257   (find-file-read-only
 258    (expand-file-name "GNU" data-directory))
 259   (goto-char (point-min)))
 260
 261 (defun describe-no-warranty ()
 262   "Display info on all the kinds of warranty Emacs does NOT have."
 263   (interactive)
 264   (describe-copying)
 265   (let (case-fold-search)
 266     (search-forward "NO WARRANTY")
 267     (recenter 0)))
 268
 269 (defun describe-prefix-bindings ()
 270   "Describe the bindings of the prefix used to reach this command.
 271 The prefix described consists of all but the last event
 272 of the key sequence that ran this command."
 273   (interactive)
 274   (let* ((key (this-command-keys))
 275          (prefix (make-vector (1- (length key)) nil))
 276          i)
 277     (setq i 0)
 278     (while (< i (length prefix))
 279       (aset prefix i (aref key i))
 280       (setq i (1+ i)))
 281     (describe-bindings prefix)))
 282 ;; Make C-h after a prefix, when not specifically bound,
 283 ;; run describe-prefix-bindings.
 284 (setq prefix-help-command 'describe-prefix-bindings)
 285
 286 (defun view-emacs-news ()
 287   "Display info on recent changes to Emacs."
 288   (interactive)
 289   (find-file-read-only (expand-file-name "NEWS" data-directory)))
 290
 291 (defun view-lossage ()
 292   "Display last 100 input keystrokes."
 293   (interactive)
 294   (with-output-to-temp-buffer "*Help*"
 295     (princ (mapconcat (function (lambda (key)
 296                                   (if (or (integerp key)
 297                                           (symbolp key)
 298                                           (listp key))
 299                                       (single-key-description key)
 300                                     (prin1-to-string key nil))))
 301                       (recent-keys)
 302                       " "))
 303     (save-excursion
 304       (set-buffer standard-output)
 305       (goto-char (point-min))
 306       (while (progn (move-to-column 50) (not (eobp)))
 307         (search-forward " " nil t)
 308         (insert "\n")))
 309     (print-help-return-message)))
 310
 311 (defalias 'help 'help-for-help)
 312 (make-help-screen help-for-help
 313   "a b c f C-f i k C-k l m n p s t v w C-c C-d C-n C-w, or ? for more help:"
 314   "You have typed \\[help-command], the help character.  Type a Help option:
 315 \(Use \\<help-map>\\[scroll-up] or \\[scroll-down] to scroll through this text.
 316 Type \\<help-map>\\[help-quit] to exit the Help command.)
 317
 318 a  command-apropos.  Give a substring, and see a list of commands
 319         (functions interactively callable) that contain
 320         that substring.  See also the  apropos  command.
 321 b  describe-bindings.  Display table of all key bindings.
 322 c  describe-key-briefly.  Type a command key sequence;
 323         it prints the function name that sequence runs.
 324 f  describe-function.  Type a function name and get documentation of it.
 325 C-f Info-goto-emacs-command-node.  Type a function name;
 326         it takes you to the Info node for that command.
 327 i  info. The  info  documentation reader.
 328 k  describe-key.  Type a command key sequence;
 329         it displays the full documentation.
 330 C-k Info-goto-emacs-key-command-node.  Type a command key sequence;
 331         it takes you to the Info node for the command bound to that key.
 332 l  view-lossage.  Shows last 100 characters you typed.
 333 m  describe-mode.  Print documentation of current major mode,
 334         which describes the commands peculiar to it.
 335 n  view-emacs-news.  Shows emacs news file.
 336 p  finder-by-keyword. Find packages matching a given topic keyword.
 337 s  describe-syntax.  Display contents of syntax table, plus explanations
 338 t  help-with-tutorial.  Select the Emacs learn-by-doing tutorial.
 339 v  describe-variable.  Type name of a variable;
 340         it displays the variable's documentation and value.
 341 w  where-is.  Type command name; it prints which keystrokes
 342         invoke that command.
 343 C-c print Emacs copying permission (General Public License).
 344 C-d print Emacs ordering information.
 345 C-n print news of recent Emacs changes.
 346 C-p print information about the GNU project.
 347 C-w print information on absence of warranty for GNU Emacs."
 348   help-map)
 349
 350 ;; Return a function which is called by the list containing point.
 351 ;; If that gives no function, return a function whose name is around point.
 352 ;; If that doesn't give a function, return nil.
 353 (defun function-called-at-point ()
 354   (or (condition-case ()
 355           (save-excursion
 356             (save-restriction
 357               (narrow-to-region (max (point-min) (- (point) 1000)) (point-max))
 358               (backward-up-list 1)
 359               (forward-char 1)
 360               (let (obj)
 361                 (setq obj (read (current-buffer)))
 362                 (and (symbolp obj) (fboundp obj) obj))))
 363         (error nil))
 364       (condition-case ()
 365           (save-excursion
 366             (forward-sexp -1)
 367             (skip-chars-forward "'")
 368             (let ((obj (read (current-buffer))))
 369               (and (symbolp obj) (fboundp obj) obj)))
 370         (error nil))))
 371
 372 (defun describe-function-find-file (function)
 373   (let ((files load-history)
 374         file functions)
 375     (while files
 376       (if (memq function (cdr (car files)))
 377           (setq file (car (car files)) files nil))
 378       (setq files (cdr files)))
 379     file))
 380
 381 (defun describe-function (function)
 382   "Display the full documentation of FUNCTION (a symbol)."
 383   (interactive
 384    (let ((fn (function-called-at-point))
 385          (enable-recursive-minibuffers t)
 386          val)
 387      (setq val (completing-read (if fn
 388                                     (format "Describe function (default %s): " fn)
 389                                   "Describe function: ")
 390                                 obarray 'fboundp t))
 391      (list (if (equal val "")
 392                fn (intern val)))))
 393   (with-output-to-temp-buffer "*Help*"
 394     (prin1 function)
 395     (princ ": ")
 396     (let* ((def (symbol-function function))
 397            (beg (if (commandp def) "an interactive " "a ")))
 398       (princ (cond ((or (stringp def)
 399                         (vectorp def))
 400                     "a keyboard macro")
 401                    ((subrp def)
 402                     (concat beg "built-in function"))
 403                    ((byte-code-function-p def)
 404                     (concat beg "compiled Lisp function"))
 405                    ((symbolp def)
 406                     (format "alias for `%s'" def))
 407                    ((eq (car-safe def) 'lambda)
 408                     (concat beg "Lisp function"))
 409                    ((eq (car-safe def) 'macro)
 410                     "a Lisp macro")
 411                    ((eq (car-safe def) 'mocklisp)
 412                     "a mocklisp function")
 413                    ((eq (car-safe def) 'autoload)
 414                     (format "%s autoloaded Lisp %s"
 415                             (if (commandp def) "an interactive" "an")
 416                             (if (nth 4 def) "macro" "function")
 417 ;;; Including the file name made this line too long.
 418 ;;;                         (nth 1 def)
 419                             ))
 420                    (t "")))
 421       (let ((file (describe-function-find-file function)))
 422         (if file
 423             (progn
 424               (princ " in `")
 425               (princ file)
 426               (princ ".el'"))))
 427       (princ ".")
 428       (terpri)
 429       (let ((arglist (cond ((byte-code-function-p def)
 430                             (car (append def nil)))
 431                            ((eq (car-safe def) 'lambda)
 432                             (nth 1 def))
 433                            (t t))))
 434         (if (listp arglist)
 435             (progn
 436               (princ (cons function
 437                            (mapcar (lambda (arg)
 438                                      (if (memq arg '(&optional &rest))
 439                                          arg
 440                                        (intern (upcase (symbol-name arg)))))
 441                                    arglist)))
 442               (terpri))))
 443       (if (documentation function)
 444           (progn (terpri)
 445                  (princ (documentation function)))
 446         (princ "not documented"))
 447       )
 448     (print-help-return-message)
 449     ;; Return the text we displayed.
 450     (save-excursion (set-buffer standard-output) (buffer-string))))
 451
 452 (defun variable-at-point ()
 453   (condition-case ()
 454       (save-excursion
 455         (forward-sexp -1)
 456         (skip-chars-forward "'")
 457         (let ((obj (read (current-buffer))))
 458           (and (symbolp obj) (boundp obj) obj)))
 459     (error nil)))
 460
 461 (defun describe-variable (variable)
 462   "Display the full documentation of VARIABLE (a symbol).
 463 Returns the documentation as a string, also."
 464   (interactive
 465    (let ((v (variable-at-point))
 466          (enable-recursive-minibuffers t)
 467          val)
 468      (setq val (completing-read (if v
 469                                     (format "Describe variable (default %s): " v)
 470                                   "Describe variable: ")
 471                                 obarray 'boundp t))
 472      (list (if (equal val "")
 473                v (intern val)))))
 474   (with-output-to-temp-buffer "*Help*"
 475     (prin1 variable)
 476     (princ "'s value is ")
 477     (if (not (boundp variable))
 478         (princ "void.")
 479       (prin1 (symbol-value variable)))
 480     (terpri)
 481     (let ((locals (buffer-local-variables))
 482           is-local)
 483       (while locals
 484         (if (or (eq variable (car locals))
 485                 (eq variable (car-safe (car locals))))
 486             (setq is-local t locals nil))
 487         (setq locals (cdr locals)))
 488       (if is-local
 489           (princ (format "Local in buffer %s\n" (buffer-name)))))
 490     (terpri)
 491     (princ "Documentation:")
 492     (terpri)
 493     (let ((doc (documentation-property variable 'variable-documentation)))
 494       (if doc
 495           (princ (substitute-command-keys doc))
 496         (princ "not documented as a variable.")))
 497     (print-help-return-message)
 498     ;; Return the text we displayed.
 499     (save-excursion (set-buffer standard-output) (buffer-string))))
 500
 501 (defun where-is (definition)
 502   "Print message listing key sequences that invoke specified command.
 503 Argument is a command definition, usually a symbol with a function definition."
 504   (interactive
 505    (let ((fn (function-called-at-point))
 506          (enable-recursive-minibuffers t)
 507          val)
 508      (setq val (completing-read (if fn
 509                                     (format "Where is command (default %s): " fn)
 510                                   "Where is command: ")
 511                                 obarray 'fboundp t))
 512      (list (if (equal val "")
 513                fn (intern val)))))
 514   (let* ((keys (where-is-internal definition overriding-local-map nil nil))
 515          (keys1 (mapconcat 'key-description keys ", ")))
 516     (if (> (length keys1) 0)
 517         (message "%s is on %s" definition keys1)
 518       (message "%s is not on any key" definition)))
 519   nil)
 520
 521 (defun command-apropos (string)
 522   "Like apropos but lists only symbols that are names of commands
 523 \(interactively callable functions).  Argument REGEXP is a regular expression
 524 that is matched against command symbol names.  Returns list of symbols and
 525 documentation found."
 526   (interactive "sCommand apropos (regexp): ")
 527   (let ((message
 528          (let ((standard-output (get-buffer-create "*Help*")))
 529            (print-help-return-message 'identity))))
 530     (if (apropos string t 'commandp t)
 531         (and message (message message)))))
 532
 533 (defun locate-library (library &optional nosuffix)
 534   "Show the full path name of Emacs library LIBRARY.
 535 This command searches the directories in `load-path' like `M-x load-library'
 536 to find the file that `M-x load-library RET LIBRARY RET' would load.
 537 Optional second arg NOSUFFIX non-nil means don't add suffixes `.elc' or `.el'
 538 to the specified name LIBRARY (a la calling `load' instead of `load-library')."
 539   (interactive "sLocate library: ")
 540   (catch 'answer
 541     (mapcar
 542      '(lambda (dir)
 543         (mapcar
 544          '(lambda (suf)
 545             (let ((try (expand-file-name (concat library suf) dir)))
 546               (and (file-readable-p try)
 547                    (null (file-directory-p try))
 548                    (progn
 549                      (message "Library is file %s" try)
 550                      (throw 'answer try)))))
 551          (if nosuffix '("") '(".elc" ".el" ""))))
 552      load-path)
 553     (message "No library %s in search path" library)
 554     nil))
 555
 556 ;;; help.el ends here