lisp/help.el

   1 ;;; help.el --- help commands for Emacs
   2
   3 ;; Copyright (C) 1985, 1986, 1993, 1994, 1998 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 the
  22 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23 ;; Boston, MA 02111-1307, USA.
  24
  25 ;;; Commentary:
  26
  27 ;; This code implements GNU Emacs' on-line help system, the one invoked by
  28 ;;`M-x help-for-help'.
  29
  30 ;;; Code:
  31
  32 ;; Get the macro make-help-screen when this is compiled,
  33 ;; or run interpreted, but not when the compiled code is loaded.
  34 (eval-when-compile (require 'help-macro))
  35
  36 (defvar help-map (make-sparse-keymap)
  37   "Keymap for characters following the Help key.")
  38
  39 (defvar help-mode-map (make-sparse-keymap)
  40   "Keymap for help mode.")
  41
  42 (define-key global-map (char-to-string help-char) 'help-command)
  43 (define-key global-map [help] 'help-command)
  44 (define-key global-map [f1] 'help-command)
  45 (fset 'help-command help-map)
  46
  47 (define-key help-map (char-to-string help-char) 'help-for-help)
  48 (define-key help-map [help] 'help-for-help)
  49 (define-key help-map [f1] 'help-for-help)
  50 (define-key help-map "?" 'help-for-help)
  51
  52 (define-key help-map "\C-c" 'describe-copying)
  53 (define-key help-map "\C-d" 'describe-distribution)
  54 (define-key help-map "\C-w" 'describe-no-warranty)
  55 (define-key help-map "\C-p" 'describe-project)
  56 (define-key help-map "a" 'apropos-command)
  57
  58 (define-key help-map "b" 'describe-bindings)
  59
  60 (define-key help-map "c" 'describe-key-briefly)
  61 (define-key help-map "k" 'describe-key)
  62
  63 (define-key help-map "d" 'describe-function)
  64 (define-key help-map "f" 'describe-function)
  65
  66 (define-key help-map "F" 'view-emacs-FAQ)
  67
  68 (define-key help-map "i" 'info)
  69 (define-key help-map "\C-f" 'Info-goto-emacs-command-node)
  70 (define-key help-map "\C-k" 'Info-goto-emacs-key-command-node)
  71 (define-key help-map "\C-i" 'info-lookup-symbol)
  72
  73 (define-key help-map "l" 'view-lossage)
  74
  75 (define-key help-map "m" 'describe-mode)
  76
  77 (define-key help-map "\C-n" 'view-emacs-news)
  78 (define-key help-map "n" 'view-emacs-news)
  79
  80 (define-key help-map "p" 'finder-by-keyword)
  81 (autoload 'finder-by-keyword "finder"
  82   "Find packages matching a given keyword." t)
  83
  84 (define-key help-map "s" 'describe-syntax)
  85
  86 (define-key help-map "t" 'help-with-tutorial)
  87
  88 (define-key help-map "w" 'where-is)
  89
  90 (define-key help-map "v" 'describe-variable)
  91
  92 (define-key help-map "q" 'help-quit)
  93
  94 (define-key help-mode-map [mouse-2] 'help-follow-mouse)
  95 (define-key help-mode-map "\C-c\C-b" 'help-go-back)
  96 (define-key help-mode-map "\C-c\C-c" 'help-follow)
  97 (define-key help-mode-map "\t" 'help-next-ref)
  98 (define-key help-mode-map [backtab] 'help-previous-ref)
  99 ;; Documentation only, since we use minor-mode-overriding-map-alist.
 100 (define-key help-mode-map "\r" 'help-follow)
 101
 102 ;; Font-locking is incompatible with the new xref stuff.
 103 ;(defvar help-font-lock-keywords
 104 ;  (eval-when-compile
 105 ;    (let ((name-char "[-+a-zA-Z0-9_*]") (sym-char "[-+a-zA-Z0-9_:*]"))
 106 ;      (list
 107 ;       ;;
 108 ;       ;; The symbol itself.
 109 ;       (list (concat "\\`\\(" name-char "+\\)\\(\\(:\\)\\|\\('\\)\\)")
 110 ;            '(1 (if (match-beginning 3)
 111 ;                    font-lock-function-name-face
 112 ;                  font-lock-variable-name-face)))
 113 ;       ;;
 114 ;       ;; Words inside `' which tend to be symbol names.
 115 ;       (list (concat "`\\(" sym-char sym-char "+\\)'")
 116 ;            1 'font-lock-constant-face t)
 117 ;       ;;
 118 ;       ;; CLisp `:' keywords as references.
 119 ;       (list (concat "\\<:" sym-char "+\\>") 0 'font-lock-builtin-face t))))
 120 ;  "Default expressions to highlight in Help mode.")
 121
 122 (defvar help-xref-stack nil
 123   "A stack of ways by which to return to help buffers after following xrefs.
 124 Used by `help-follow' and `help-xref-go-back'.")
 125 (put 'help-xref-stack 'permanent-local t)
 126
 127 (defvar help-xref-stack-item nil
 128   "An item for `help-follow' in this buffer to push onto `help-xref-stack'.")
 129 (put 'help-xref-stack-item 'permanent-local t)
 130
 131 (setq-default help-xref-stack nil help-xref-stack-item nil)
 132
 133 (defun help-mode ()
 134   "Major mode for viewing help text and navigating references in it.
 135 Entry to this mode runs the normal hook `help-mode-hook'.
 136 Commands:
 137 \\{help-mode-map}"
 138   (interactive)
 139   (kill-all-local-variables)
 140   (use-local-map help-mode-map)
 141   (setq mode-name "Help")
 142   (setq major-mode 'help-mode)
 143   (make-local-variable 'font-lock-defaults)
 144   (setq font-lock-defaults nil)         ; font-lock would defeat xref
 145   (view-mode)
 146   (make-local-variable 'view-no-disable-on-exit)
 147   (setq view-no-disable-on-exit t)
 148   ;; `help-make-xrefs' would be run here if not invoked from
 149   ;; `help-mode-maybe'.
 150   (run-hooks 'help-mode-hook))
 151
 152 (defun help-mode-maybe ()
 153   (if (eq major-mode 'fundamental-mode)
 154       (help-mode))
 155   (when (eq major-mode 'help-mode)
 156     ;; View mode's read-only status of existing *Help* buffer is lost
 157     ;; by with-output-to-temp-buffer.
 158     (toggle-read-only 1)
 159     (help-make-xrefs (current-buffer)))
 160   (setq view-return-to-alist
 161         (list (cons (selected-window) help-return-method))))
 162
 163 (add-hook 'temp-buffer-show-hook 'help-mode-maybe)
 164
 165 (defun help-quit ()
 166   (interactive)
 167   nil)
 168
 169 (defun help-with-tutorial (&optional arg)
 170   "Select the Emacs learn-by-doing tutorial.
 171 If there is a tutorial version written in the language
 172 of the selected language environment, that version is used.
 173 If there's no tutorial in that language, `TUTORIAL' is selected.
 174 With arg, you are asked to choose which language."
 175   (interactive "P")
 176   (let ((lang (if arg
 177                   (read-language-name 'tutorial "Language: " "English")
 178                 (if (get-language-info current-language-environment 'tutorial)
 179                     current-language-environment
 180                   "English")))
 181         file filename)
 182     (setq filename (get-language-info lang 'tutorial))
 183     (setq file (expand-file-name (concat "~/" filename)))
 184     (delete-other-windows)
 185     (if (get-file-buffer file)
 186         (switch-to-buffer (get-file-buffer file))
 187       (switch-to-buffer (create-file-buffer file))
 188       (setq buffer-file-name file)
 189       (setq default-directory (expand-file-name "~/"))
 190       (setq buffer-auto-save-file-name nil)
 191       (insert-file-contents (expand-file-name filename data-directory))
 192       (goto-char (point-min))
 193       (search-forward "\n<<")
 194       (beginning-of-line)
 195       (delete-region (point) (progn (end-of-line) (point)))
 196       (let ((n (- (window-height (selected-window))
 197                   (count-lines (point-min) (point))
 198                   6)))
 199         (if (< n 12)
 200             (newline n)
 201           ;; Some people get confused by the large gap.
 202           (newline (/ n 2))
 203           (insert "[Middle of page left blank for didactic purposes.  "
 204                   "Text continues below]")
 205           (newline (- n (/ n 2)))))
 206       (goto-char (point-min))
 207       (set-buffer-modified-p nil))))
 208
 209 (defun describe-key-briefly (key &optional insert)
 210   "Print the name of the function KEY invokes.  KEY is a string.
 211 If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
 212   (interactive "kDescribe key briefly: \nP")
 213   ;; If this key seq ends with a down event, discard the
 214   ;; following click or drag event.  Otherwise that would
 215   ;; erase the message.
 216   (let ((type (aref key (1- (length key)))))
 217     (if (listp type) (setq type (car type)))
 218     (and (symbolp type)
 219          (memq 'down (event-modifiers type))
 220          (read-event)))
 221   (save-excursion
 222     (let ((modifiers (event-modifiers (aref key 0)))
 223           (standard-output (if insert (current-buffer) t))
 224           window position)
 225       ;; For a mouse button event, go to the button it applies to
 226       ;; to get the right key bindings.  And go to the right place
 227       ;; in case the keymap depends on where you clicked.
 228       (if (or (memq 'click modifiers) (memq 'down modifiers)
 229               (memq 'drag modifiers))
 230           (setq window (posn-window (event-start (aref key 0)))
 231                 position (posn-point (event-start (aref key 0)))))
 232       (if (windowp window)
 233           (progn
 234             (set-buffer (window-buffer window))
 235             (goto-char position)))
 236       ;; Ok, now look up the key and name the command.
 237       (let ((defn (key-binding key))
 238             (key-desc (key-description key)))
 239         (if (or (null defn) (integerp defn))
 240             (princ (format "%s is undefined" key-desc))
 241           (princ (format (if insert
 242                              "%s (%s)"
 243                            (if (windowp window)
 244                                "%s at that spot runs the command %s"
 245                              "%s runs the command %s"))
 246                          key-desc
 247                          (if (symbolp defn) defn (prin1-to-string defn)))))))))
 248
 249 (defvar help-return-method nil
 250   "What to do to \"exit\" the help buffer.
 251 This is a list
 252  (WINDOW . t)              delete the selected window, go to WINDOW.
 253  (WINDOW . quit-window)    do quit-window, then select WINDOW.
 254  (WINDOW BUF START POINT)  display BUF at START, POINT, then select WINDOW.")
 255
 256 (defun print-help-return-message (&optional function)
 257   "Display or return message saying how to restore windows after help command.
 258 Computes a message and applies the optional argument FUNCTION to it.
 259 If FUNCTION is nil, applies `message' to it, thus printing it."
 260   (and (not (get-buffer-window standard-output))
 261        (let ((first-message
 262               (cond ((special-display-p (buffer-name standard-output))
 263                      (setq help-return-method (cons (selected-window) t))
 264                      ;; If the help output buffer is a special display buffer,
 265                      ;; don't say anything about how to get rid of it.
 266                      ;; First of all, the user will do that with the window
 267                      ;; manager, not with Emacs.
 268                      ;; Secondly, the buffer has not been displayed yet,
 269                      ;; so we don't know whether its frame will be selected.
 270                      nil)
 271                     ((not (one-window-p t))
 272                      (setq help-return-method
 273                            (cons (selected-window) 'quit-window))
 274                      "Type \\[switch-to-buffer-other-window] RET to restore the other window.")
 275                     (pop-up-windows
 276                      (setq help-return-method (cons (selected-window) t))
 277                      "Type \\[delete-other-windows] to remove help window.")
 278                     (t
 279                      (setq help-return-method
 280                            (list (selected-window) (window-buffer)
 281                                  (window-start) (window-point)))
 282                      "Type \\[switch-to-buffer] RET to remove help window."))))
 283          (funcall (or function 'message)
 284                   (concat
 285                    (if first-message
 286                        (substitute-command-keys first-message)
 287                      "")
 288                    (if first-message "  " "")
 289                    ;; If the help buffer will go in a separate frame,
 290                    ;; it's no use mentioning a command to scroll, so don't.
 291                    (if (special-display-p (buffer-name standard-output))
 292                        nil
 293                      (if (same-window-p (buffer-name standard-output))
 294                          ;; Say how to scroll this window.
 295                          (substitute-command-keys
 296                           "\\[scroll-up] to scroll the help.")
 297                        ;; Say how to scroll some other window.
 298                        (substitute-command-keys
 299                         "\\[scroll-other-window] to scroll the help."))))))))
 300
 301 (defun describe-key (key)
 302   "Display documentation of the function invoked by KEY.  KEY is a string."
 303   (interactive "kDescribe key: ")
 304   ;; If this key seq ends with a down event, discard the
 305   ;; following click or drag event.  Otherwise that would
 306   ;; erase the message.
 307   (let ((type (aref key (1- (length key)))))
 308     (if (listp type) (setq type (car type)))
 309     (and (symbolp type)
 310          (memq 'down (event-modifiers type))
 311          (read-event)))
 312   (save-excursion
 313     (let ((modifiers (event-modifiers (aref key 0)))
 314           window position)
 315       ;; For a mouse button event, go to the button it applies to
 316       ;; to get the right key bindings.  And go to the right place
 317       ;; in case the keymap depends on where you clicked.
 318       (if (or (memq 'click modifiers) (memq 'down modifiers)
 319               (memq 'drag modifiers))
 320           (setq window (posn-window (event-start (aref key 0)))
 321                 position (posn-point (event-start (aref key 0)))))
 322       (if (windowp window)
 323           (progn
 324             (set-buffer (window-buffer window))
 325             (goto-char position)))
 326       (let ((defn (key-binding key)))
 327         (if (or (null defn) (integerp defn))
 328             (message "%s is undefined" (key-description key))
 329           (with-output-to-temp-buffer "*Help*"
 330             (princ (key-description key))
 331             (if (windowp window)
 332                 (princ " at that spot"))
 333             (princ " runs the command ")
 334             (prin1 defn)
 335             (princ "\n   which is ")
 336             (describe-function-1 defn nil)
 337             (print-help-return-message)))))))
 338
 339 (defun describe-mode ()
 340   "Display documentation of current major mode and minor modes.
 341 For this to work correctly for a minor mode, the mode's indicator variable
 342 \(listed in `minor-mode-alist') must also be a function whose documentation
 343 describes the minor mode."
 344   (interactive)
 345   (with-output-to-temp-buffer "*Help*"
 346     (let ((minor-modes minor-mode-alist)
 347           (first t))
 348       (while minor-modes
 349         (let* ((minor-mode (car (car minor-modes)))
 350                (indicator (car (cdr (car minor-modes)))))
 351           ;; Document a minor mode if it is listed in minor-mode-alist,
 352           ;; bound locally in this buffer, non-nil, and has a function
 353           ;; definition.
 354           (if (and (symbol-value minor-mode)
 355                    (fboundp minor-mode))
 356               (let ((pretty-minor-mode minor-mode))
 357                 (if (string-match "-mode$" (symbol-name minor-mode))
 358                     (setq pretty-minor-mode
 359                           (capitalize
 360                            (substring (symbol-name minor-mode)
 361                                       0 (match-beginning 0)))))
 362                 (while (and indicator (symbolp indicator))
 363                   (setq indicator (symbol-value indicator)))
 364                 (if first
 365                     (princ "The minor modes are described first,
 366 followed by the major mode, which is described on the last page.\n\f\n"))
 367                 (setq first nil)
 368                 (princ (format "%s minor mode (%s):\n"
 369                                pretty-minor-mode
 370                                (if indicator
 371                                    (format "indicator%s" indicator)
 372                                  "no indicator")))
 373                 (princ (documentation minor-mode))
 374                 (princ "\n\f\n"))))
 375         (setq minor-modes (cdr minor-modes))))
 376     (princ mode-name)
 377     (princ " mode:\n")
 378     (princ (documentation major-mode))
 379     (help-setup-xref (cons #'help-xref-mode (current-buffer)) (interactive-p))
 380     (print-help-return-message)))
 381
 382 ;; So keyboard macro definitions are documented correctly
 383 (fset 'defining-kbd-macro (symbol-function 'start-kbd-macro))
 384
 385 (defun describe-distribution ()
 386   "Display info on how to obtain the latest version of GNU Emacs."
 387   (interactive)
 388   (find-file-read-only
 389    (expand-file-name "DISTRIB" data-directory)))
 390
 391 (defun describe-copying ()
 392   "Display info on how you may redistribute copies of GNU Emacs."
 393   (interactive)
 394   (find-file-read-only
 395    (expand-file-name "COPYING" data-directory))
 396   (goto-char (point-min)))
 397
 398 (defun describe-project ()
 399   "Display info on the GNU project."
 400   (interactive)
 401   (find-file-read-only
 402    (expand-file-name "GNU" data-directory))
 403   (goto-char (point-min)))
 404
 405 (defun describe-no-warranty ()
 406   "Display info on all the kinds of warranty Emacs does NOT have."
 407   (interactive)
 408   (describe-copying)
 409   (let (case-fold-search)
 410     (search-forward "NO WARRANTY")
 411     (recenter 0)))
 412
 413 (defun describe-prefix-bindings ()
 414   "Describe the bindings of the prefix used to reach this command.
 415 The prefix described consists of all but the last event
 416 of the key sequence that ran this command."
 417   (interactive)
 418   (let* ((key (this-command-keys)))
 419     (describe-bindings
 420      (if (stringp key)
 421          (substring key 0 (1- (length key)))
 422        (let ((prefix (make-vector (1- (length key)) nil))
 423              (i 0))
 424          (while (< i (length prefix))
 425            (aset prefix i (aref key i))
 426            (setq i (1+ i)))
 427          prefix)))))
 428 ;; Make C-h after a prefix, when not specifically bound,
 429 ;; run describe-prefix-bindings.
 430 (setq prefix-help-command 'describe-prefix-bindings)
 431
 432 (defun view-emacs-news (&optional arg)
 433   "Display info on recent changes to Emacs.
 434 With numeric argument display information on correspondingly older changes."
 435   (interactive "P")
 436   (let* ((arg (if arg (prefix-numeric-value arg) 0)))
 437     (find-file-read-only
 438      (expand-file-name (concat (make-string arg ?O) "NEWS")
 439                        data-directory))))
 440
 441 (defun view-emacs-FAQ ()
 442   "Display the Emacs Frequently Asked Questions (FAQ) file."
 443   (interactive)
 444   (find-file-read-only (expand-file-name "FAQ" data-directory)))
 445
 446 (defun view-lossage ()
 447   "Display last 100 input keystrokes."
 448   (interactive)
 449   (with-output-to-temp-buffer "*Help*"
 450     (princ (mapconcat (function (lambda (key)
 451                                   (if (or (integerp key)
 452                                           (symbolp key)
 453                                           (listp key))
 454                                       (single-key-description key)
 455                                     (prin1-to-string key nil))))
 456                       (recent-keys)
 457                       " "))
 458     (save-excursion
 459       (set-buffer standard-output)
 460       (goto-char (point-min))
 461       (while (progn (move-to-column 50) (not (eobp)))
 462         (search-forward " " nil t)
 463         (insert "\n")))
 464     (setq help-xref-stack nil
 465           help-xref-stack-item nil)
 466     (print-help-return-message)))
 467
 468 (defalias 'help 'help-for-help)
 469 (make-help-screen help-for-help
 470   "a b c C f F C-f i I k C-k l L m n p s t v w C-c C-d C-n C-p C-w; ? for help:"
 471   "You have typed \\[help-command], the help character.  Type a Help option:
 472 \(Use SPC or DEL to scroll through this text.  Type \\<help-map>\\[help-quit] to exit the Help command.)
 473
 474 a  command-apropos.  Give a substring, and see a list of commands
 475         (functions interactively callable) that contain
 476         that substring.  See also the  apropos  command.
 477 b  describe-bindings.  Display table of all key bindings.
 478 c  describe-key-briefly.  Type a command key sequence;
 479         it prints the function name that sequence runs.
 480 C  describe-coding-system.  This describes either a specific coding system
 481         (if you type its name) or the coding systems currently in use
 482         (if you type just RET).
 483 f  describe-function.  Type a function name and get documentation of it.
 484 C-f Info-goto-emacs-command-node.  Type a function name;
 485         it takes you to the Info node for that command.
 486 i  info. The  info  documentation reader.
 487 I  describe-input-method.  Describe a specific input method (if you type
 488         its name) or the current input method (if you type just RET).
 489 k  describe-key.  Type a command key sequence;
 490         it displays the full documentation.
 491 C-k Info-goto-emacs-key-command-node.  Type a command key sequence;
 492         it takes you to the Info node for the command bound to that key.
 493 l  view-lossage.  Shows last 100 characters you typed.
 494 L  describe-language-environment.  This describes either the a
 495         specific language environment (if you type its name)
 496         or the current language environment (if you type just RET).
 497 m  describe-mode.  Print documentation of current minor modes,
 498         and the current major mode, including their special commands.
 499 n  view-emacs-news.  Shows emacs news file.
 500 p  finder-by-keyword. Find packages matching a given topic keyword.
 501 s  describe-syntax.  Display contents of syntax table, plus explanations
 502 t  help-with-tutorial.  Select the Emacs learn-by-doing tutorial.
 503 v  describe-variable.  Type name of a variable;
 504         it displays the variable's documentation and value.
 505 w  where-is.  Type command name; it prints which keystrokes
 506         invoke that command.
 507
 508 F  Display the frequently asked questions file.
 509 h  Display the HELLO file which illustrates various scripts.
 510 C-c Display Emacs copying permission (General Public License).
 511 C-d Display Emacs ordering information.
 512 C-n Display news of recent Emacs changes.
 513 C-p Display information about the GNU project.
 514 C-w Display information on absence of warranty for GNU Emacs."
 515   help-map)
 516
 517 ;; Return a function which is called by the list containing point.
 518 ;; If that gives no function, return a function whose name is around point.
 519 ;; If that doesn't give a function, return nil.
 520 (defun function-called-at-point ()
 521   (let ((stab (syntax-table)))
 522     (set-syntax-table emacs-lisp-mode-syntax-table)
 523     (unwind-protect
 524         (or (condition-case ()
 525                 (save-excursion
 526                   (save-restriction
 527                     (narrow-to-region (max (point-min) (- (point) 1000)) (point-max))
 528                     ;; Move up to surrounding paren, then after the open.
 529                     (backward-up-list 1)
 530                     (forward-char 1)
 531                     ;; If there is space here, this is probably something
 532                     ;; other than a real Lisp function call, so ignore it.
 533                     (if (looking-at "[ \t]")
 534                         (error "Probably not a Lisp function call"))
 535                     (let (obj)
 536                       (setq obj (read (current-buffer)))
 537                       (and (symbolp obj) (fboundp obj) obj))))
 538               (error nil))
 539             (condition-case ()
 540                 (save-excursion
 541                   (or (not (zerop (skip-syntax-backward "_w")))
 542                       (eq (char-syntax (following-char)) ?w)
 543                       (eq (char-syntax (following-char)) ?_)
 544                       (forward-sexp -1))
 545                   (skip-chars-forward "'")
 546                   (let ((obj (read (current-buffer))))
 547                     (and (symbolp obj) (fboundp obj) obj)))
 548               (error nil)))
 549       (set-syntax-table stab))))
 550
 551 (defun describe-function-find-file (function)
 552   (let ((files load-history)
 553         file functions)
 554     (while files
 555       (if (memq function (cdr (car files)))
 556           (setq file (car (car files)) files nil))
 557       (setq files (cdr files)))
 558     file))
 559
 560 (defun describe-function (function)
 561   "Display the full documentation of FUNCTION (a symbol)."
 562   (interactive
 563    (let ((fn (function-called-at-point))
 564          (enable-recursive-minibuffers t)
 565          val)
 566      (setq val (completing-read (if fn
 567                                     (format "Describe function (default %s): " fn)
 568                                   "Describe function: ")
 569                                 obarray 'fboundp t nil nil (symbol-name fn)))
 570      (list (if (equal val "")
 571                fn (intern val)))))
 572   (if function
 573       (with-output-to-temp-buffer "*Help*"
 574         (prin1 function)
 575         ;; Use " is " instead of a colon so that
 576         ;; it is easier to get out the function name using forward-sexp.
 577         (princ " is ")
 578         (describe-function-1 function nil)
 579         (print-help-return-message)
 580         (save-excursion
 581           (set-buffer standard-output)
 582           ;; Return the text we displayed.
 583           (buffer-string)))
 584     (message "You didn't specify a function")))
 585
 586 (defun describe-function-1 (function parens)
 587   (let* ((def (symbol-function function))
 588          file-name string need-close
 589          (beg (if (commandp def) "an interactive " "a ")))
 590     (setq string
 591           (cond ((or (stringp def)
 592                      (vectorp def))
 593                  "a keyboard macro")
 594                 ((subrp def)
 595                  (concat beg "built-in function"))
 596                 ((byte-code-function-p def)
 597                  (concat beg "compiled Lisp function"))
 598                 ((symbolp def)
 599                  (format "alias for `%s'" def))
 600                 ((eq (car-safe def) 'lambda)
 601                  (concat beg "Lisp function"))
 602                 ((eq (car-safe def) 'macro)
 603                  "a Lisp macro")
 604                 ((eq (car-safe def) 'mocklisp)
 605                  "a mocklisp function")
 606                 ((eq (car-safe def) 'autoload)
 607                  (setq file-name (nth 1 def))
 608                  (format "%s autoloaded Lisp %s"
 609                          (if (commandp def) "an interactive" "an")
 610                          (if (nth 4 def) "macro" "function")
 611                          ))
 612                 (t "")))
 613     (when (and parens (not (equal string "")))
 614       (setq need-close t)
 615       (princ "("))
 616     (princ string)
 617     (or file-name
 618         (setq file-name (describe-function-find-file function)))
 619     (if file-name
 620         (progn
 621           (princ " in `")
 622           ;; We used to add .el to the file name,
 623           ;; but that's completely wrong when the user used load-file.
 624           (princ file-name)
 625           (princ "'")))
 626     (if need-close (princ ")"))
 627     (princ ".")
 628     (terpri)
 629     (let* ((inner-function (if (and (listp def) 'macro)
 630                                (cdr def)
 631                              def))
 632            (arglist (cond ((byte-code-function-p inner-function)
 633                            (car (append inner-function nil)))
 634                           ((eq (car-safe inner-function) 'lambda)
 635                            (nth 1 inner-function))
 636                           (t t))))
 637       (if (listp arglist)
 638           (progn
 639             (princ (cons function
 640                          (mapcar (lambda (arg)
 641                                    (if (memq arg '(&optional &rest))
 642                                        arg
 643                                      (intern (upcase (symbol-name arg)))))
 644                                  arglist)))
 645             (terpri))))
 646     (let ((doc (documentation function)))
 647       (if doc
 648           (progn (terpri)
 649                  (princ doc)
 650                  (help-setup-xref (cons #'describe-function function) (interactive-p)))
 651         (princ "not documented")))))
 652
 653 ;; We return 0 if we can't find a variable to return.
 654 (defun variable-at-point ()
 655   (condition-case ()
 656       (let ((stab (syntax-table)))
 657         (unwind-protect
 658             (save-excursion
 659               (set-syntax-table emacs-lisp-mode-syntax-table)
 660               (or (not (zerop (skip-syntax-backward "_w")))
 661                   (eq (char-syntax (following-char)) ?w)
 662                   (eq (char-syntax (following-char)) ?_)
 663                   (forward-sexp -1))
 664               (skip-chars-forward "'")
 665               (let ((obj (read (current-buffer))))
 666                 (or (and (symbolp obj) (boundp obj) obj)
 667                     0)))
 668           (set-syntax-table stab)))
 669     (error 0)))
 670
 671 (defun describe-variable (variable)
 672   "Display the full documentation of VARIABLE (a symbol).
 673 Returns the documentation as a string, also."
 674   (interactive
 675    (let ((v (variable-at-point))
 676          (enable-recursive-minibuffers t)
 677          val)
 678      (setq val (completing-read (if (symbolp v)
 679                                     (format "Describe variable (default %s): " v)
 680                                   "Describe variable: ")
 681                                 obarray 'boundp t nil nil
 682                                 (if (symbolp v) (symbol-name v))))
 683      (list (if (equal val "")
 684                v (intern val)))))
 685   (if (symbolp variable)
 686       (let (valvoid)
 687         (with-output-to-temp-buffer "*Help*"
 688           (prin1 variable)
 689           (if (not (boundp variable))
 690               (progn
 691                 (princ " is void")
 692                 (terpri)
 693                 (setq valvoid t))
 694             (princ "'s value is ")
 695             (terpri)
 696             (pp (symbol-value variable))
 697             (terpri))
 698           (if (local-variable-p variable)
 699               (progn
 700                 (princ (format "Local in buffer %s; " (buffer-name)))
 701                 (if (not (default-boundp variable))
 702                     (princ "globally void")
 703                   (princ "global value is ")
 704                   (terpri)
 705                   (pp (default-value variable)))
 706                 (terpri)))
 707           (terpri)
 708           (save-current-buffer
 709             (set-buffer standard-output)
 710             (if (> (count-lines (point-min) (point-max)) 10)
 711                 (progn
 712                   (goto-char (point-min))
 713                   (if valvoid
 714                       (forward-line 1)
 715                     (forward-sexp 1)
 716                     (delete-region (point) (progn (end-of-line) (point)))
 717                     (insert "'s value is shown below.\n\n")
 718                     (save-excursion
 719                       (insert "\n\nValue:"))))))
 720           (princ "Documentation:")
 721           (terpri)
 722           (let ((doc (documentation-property variable 'variable-documentation)))
 723             (princ (or doc "not documented as a variable.")))
 724           (help-setup-xref (cons #'describe-variable variable) (interactive-p))
 725           (print-help-return-message)
 726           (save-excursion
 727             (set-buffer standard-output)
 728             ;; Return the text we displayed.
 729             (buffer-string))))
 730     (message "You did not specify a variable")))
 731
 732 (defun describe-bindings (&optional prefix)
 733   "Show a list of all defined keys, and their definitions.
 734 We put that list in a buffer, and display the buffer.
 735
 736 The optional argument PREFIX, if non-nil, should be a key sequence;
 737 then we display only bindings that start with that prefix."
 738   (interactive "P")
 739   (setq help-xref-stack nil
 740         help-xref-stack-item nil)
 741   (describe-bindings-internal nil prefix))
 742
 743 (defun where-is (definition &optional insert)
 744   "Print message listing key sequences that invoke specified command.
 745 Argument is a command definition, usually a symbol with a function definition.
 746 If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
 747   (interactive
 748    (let ((fn (function-called-at-point))
 749          (enable-recursive-minibuffers t)
 750          val)
 751      (setq val (completing-read (if fn
 752                                     (format "Where is command (default %s): " fn)
 753                                   "Where is command: ")
 754                                 obarray 'fboundp t))
 755      (list (if (equal val "")
 756                fn (intern val))
 757            current-prefix-arg)))
 758   (let* ((keys (where-is-internal definition overriding-local-map nil nil))
 759          (keys1 (mapconcat 'key-description keys ", "))
 760          (standard-output (if insert (current-buffer) t)))
 761     (if insert
 762         (if (> (length keys1) 0)
 763             (princ (format "%s (%s)" keys1 definition))
 764           (princ (format "M-x %s RET" definition)))
 765       (if (> (length keys1) 0)
 766           (princ (format "%s is on %s" definition keys1))
 767         (princ (format "%s is not on any key" definition)))))
 768   nil)
 769
 770 (defun locate-library (library &optional nosuffix path interactive-call)
 771   "Show the precise file name of Emacs library LIBRARY.
 772 This command searches the directories in `load-path' like `M-x load-library'
 773 to find the file that `M-x load-library RET LIBRARY RET' would load.
 774 Optional second arg NOSUFFIX non-nil means don't add suffixes `.elc' or `.el'
 775 to the specified name LIBRARY.
 776
 777 If the optional third arg PATH is specified, that list of directories
 778 is used instead of `load-path'."
 779   (interactive (list (read-string "Locate library: ")
 780                      nil nil
 781                      t))
 782   (let (result)
 783     (catch 'answer
 784       (mapcar
 785        (lambda (dir)
 786          (mapcar
 787           (lambda (suf)
 788             (let ((try (expand-file-name (concat library suf) dir)))
 789               (and (file-readable-p try)
 790                    (null (file-directory-p try))
 791                    (progn
 792                      (setq result try)
 793                      (throw 'answer try)))))
 794           (if nosuffix
 795               '("")
 796             '(".elc" ".el" "")
 797 ;;; load doesn't handle this yet.
 798 ;;;         (let ((basic '(".elc" ".el" ""))
 799 ;;;               (compressed '(".Z" ".gz" "")))
 800 ;;;           ;; If autocompression mode is on,
 801 ;;;           ;; consider all combinations of library suffixes
 802 ;;;           ;; and compression suffixes.
 803 ;;;           (if (rassq 'jka-compr-handler file-name-handler-alist)
 804 ;;;               (apply 'nconc
 805 ;;;                      (mapcar (lambda (compelt)
 806 ;;;                                (mapcar (lambda (baselt)
 807 ;;;                                          (concat baselt compelt))
 808 ;;;                                        basic))
 809 ;;;                              compressed))
 810 ;;;             basic))
 811             )))
 812        (or path load-path)))
 813     (and interactive-call
 814          (if result
 815              (message "Library is file %s" result)
 816            (message "No library %s in search path" library)))
 817     result))
 818
 819 \f
 820 ;;; Grokking cross-reference information in doc strings and
 821 ;;; hyperlinking it.
 822
 823 ;; This may have some scope for extension and the same or something
 824 ;; similar should be done for widget doc strings, which currently use
 825 ;; another mechanism.
 826
 827 (defcustom help-highlight-p t
 828   "*If non-nil, `help-make-xrefs' highlight cross-references.
 829 Under a window system it highlights them with face defined by
 830 `help-highlight-face'.  On a character terminal highlighted
 831 references look like cross-references in info mode."
 832  :group 'help
 833  :version "20.3"
 834  :type 'boolean)
 835
 836 (defcustom help-highlight-face 'underline
 837   "Face used by `help-make-xrefs' to highlight cross-references.
 838 Must be previously-defined."
 839   :group 'help
 840   :version "20.3"
 841   :type 'symbol)
 842
 843 (defvar help-back-label "[back]"
 844   "Label to use by `help-make-xrefs' for the go-back reference.")
 845
 846 (defvar help-xref-symbol-regexp
 847   (concat "\\(\\<\\(\\(variable\\|option\\)\\|"
 848           "\\(function\\|command\\)\\|"
 849           "\\(symbol\\)\\)\\s-+\\)?"
 850           ;; Note starting with word-syntax character:
 851           "`\\(\\sw\\(\\sw\\|\\s_\\)+\\)'")
 852   "Regexp matching doc string references to symbols.
 853
 854 The words preceding the quoted symbol can be used in doc strings to
 855 distinguish references to variables, functions and symbols.")
 856
 857 (defvar help-xref-info-regexp
 858   "\\<info\\s-+node\\s-`\\([^']+\\)'"
 859   "Regexp matching doc string references to an Info node.")
 860
 861 (defun help-setup-xref (item interactive-p)
 862   "Invoked from commands using the \"*Help*\" buffer to install some xref info.
 863
 864 ITEM is a (function . args) pair appropriate for recreating the help
 865 buffer after following a reference.  INTERACTIVE-P is non-nil if the
 866 calling command was invoked interactively.  In this case the stack of
 867 items for help buffer \"back\" buttons is cleared."
 868   (if interactive-p
 869       (setq help-xref-stack nil))
 870   (setq help-xref-stack-item item))
 871
 872 (defun help-make-xrefs (&optional buffer)
 873   "Parse and hyperlink documentation cross-references in the given BUFFER.
 874
 875 Find cross-reference information in a buffer and, if
 876 `help-highlight-p' is non-nil, highlight it with face defined by
 877 `help-highlight-face'; activate such cross references for selection
 878 with `help-follow'.  Cross-references have the canonical form `...'
 879 and the type of reference may be disambiguated by the preceding
 880 word(s) used in `help-xref-symbol-regexp'.
 881
 882 A special reference `back' is made to return back through a stack of
 883 help buffers.  Variable `help-back-label' specifies the text for
 884 that."
 885   (interactive "b")
 886   (save-excursion
 887     (set-buffer (or buffer (current-buffer)))
 888     (goto-char (point-min))
 889     ;; Skip the header-type info, though it might be useful to parse
 890     ;; it at some stage (e.g. "function in `library'").
 891     (forward-paragraph)
 892     (let ((old-modified (buffer-modified-p)))
 893       (let ((stab (syntax-table))
 894             (case-fold-search t)
 895             (inhibit-read-only t))
 896         (set-syntax-table emacs-lisp-mode-syntax-table)
 897         ;; The following should probably be abstracted out.
 898         (unwind-protect
 899             (progn
 900               ;; Quoted symbols
 901               (save-excursion
 902                 (while (re-search-forward help-xref-symbol-regexp nil t)
 903                   (let* ((data (match-string 6))
 904                          (sym (intern-soft data)))
 905                     (if sym
 906                         (cond
 907                          ((match-string 3) ; `variable' &c
 908                           (and (boundp sym) ; `variable' doesn't ensure
 909                                         ; it's actually bound
 910                                (help-xref-button 6 #'describe-variable sym)))
 911                          ((match-string 4) ; `function' &c
 912                           (and (fboundp sym) ; similarly
 913                                (help-xref-button 6 #'describe-function sym)))
 914                          ((match-string 5)) ; nothing for symbol
 915                          ((and (boundp sym) (fboundp sym))
 916                           ;; We can't intuit whether to use the
 917                           ;; variable or function doc -- supply both.
 918                           (help-xref-button 6 #'help-xref-interned sym))
 919                          ((boundp sym)
 920                           (help-xref-button 6 #'describe-variable sym))
 921                          ((fboundp sym)
 922                           (help-xref-button 6 #'describe-function sym)))))))
 923               ;; Info references
 924               (save-excursion
 925                 (while (re-search-forward help-xref-info-regexp nil t)
 926                   (help-xref-button 1 #'Info-goto-node (list (match-data 1)))))
 927               ;; An obvious case of a key substitution:
 928               (save-excursion
 929                 (while (re-search-forward
 930                         "\\<M-x\\s-+\\(\\sw\\(\\sw\\|\\s_\\)+\\)" nil t)
 931                   (let ((sym (intern-soft (match-string 1))))
 932                     (if (fboundp sym)
 933                         (help-xref-button 1 #'describe-function sym)))))
 934               ;; Look for commands in whole keymap substitutions:
 935               (save-excursion
 936                 ;; Find a header and the column at which the command
 937                 ;; name will be found.
 938                 (while (re-search-forward "^key +binding\n\\(-+ +\\)-+\n\n"
 939                                           nil t)
 940                   (let ((col (- (match-end 1) (match-beginning 1))))
 941                     (while
 942                         ;; Ignore single blank lines in table, but not
 943                         ;; double ones, which should terminate it.
 944                         (and (looking-at "^\n?[^\n]")
 945                              (progn
 946                                (if (and (> (move-to-column col) 0)
 947                                         (looking-at "\\(\\sw\\|\\s_\\)+$"))
 948                                    ;;
 949                                    (let ((sym (intern-soft (match-string 0))))
 950                                      (if (fboundp sym)
 951                                          (help-xref-button
 952                                           0 #'describe-function sym))))
 953                                t)
 954                              (zerop (forward-line))
 955                              (move-to-column 0)))))))
 956           (set-syntax-table stab))
 957         ;; Make a back-reference in this buffer if appropriate.
 958         (when help-xref-stack
 959           (goto-char (point-max))
 960           (save-excursion
 961             (insert "\n\n" help-back-label))
 962           ;; Just to provide the match data:
 963           (looking-at (concat "\n\n\\(" (regexp-quote help-back-label) "\\)"))
 964           (help-xref-button 1 #'help-xref-go-back nil)))
 965       ;; View mode steals RET from us.
 966       (set (make-local-variable 'minor-mode-overriding-map-alist)
 967            (list (cons 'view-mode
 968                        (let ((map (make-sparse-keymap)))
 969                          (set-keymap-parent map view-mode-map)
 970                          (define-key map "\r" 'help-follow)
 971                          map))))
 972       (set-buffer-modified-p old-modified))))
 973
 974 (defun help-xref-button (match-number function data)
 975   "Make a hyperlink for cross-reference text previously matched.
 976
 977 MATCH-NUMBER is the subexpression of interest in the last matched
 978 regexp.  FUNCTION is a function to invoke when the button is
 979 activated, applied to DATA.  DATA may be a single value or a list.
 980 See `help-make-xrefs'."
 981   (add-text-properties (match-beginning match-number)
 982                      (match-end match-number)
 983                        (list 'mouse-face 'highlight
 984                      'help-xref (cons function
 985                                       (if (listp data)
 986                                           data
 987                                         (list data)))))
 988   (if help-highlight-p
 989       (put-text-property (match-beginning match-number)
 990                          (match-end match-number)
 991                          'face help-highlight-face)))
 992
 993 \f
 994 ;; Additional functions for (re-)creating types of help buffers.
 995 (defun help-xref-interned (symbol)
 996   "Follow a hyperlink which appeared to be an arbitrary interned SYMBOL.
 997
 998 Both variable and function documentation are extracted into a single
 999 help buffer."
1000   (let ((fdoc (describe-function symbol)))
1001     (describe-variable symbol)
1002     ;; We now have a help buffer on the variable.  Insert the function
1003     ;; text after it.
1004     (goto-char (point-max))
1005     (insert "\n\n" fdoc))
1006   (goto-char (point-min))
1007   (help-setup-xref (cons #'help-xref-interned symbol) nil))
1008
1009 (defun help-xref-mode (buffer)
1010   "Do a `describe-mode' for the specified BUFFER."
1011   (save-excursion
1012     (set-buffer buffer)
1013     (describe-mode)))
1014 \f
1015 ;;; Navigation/hyperlinking with xrefs
1016
1017 (defun help-follow-mouse (click)
1018   "Follow the cross-reference that you click on."
1019   (interactive "e")
1020   (save-excursion
1021     (let* ((start (event-start click))
1022            (window (car start))
1023            (pos (car (cdr start))))
1024       (set-buffer (window-buffer window))
1025       (help-follow pos))))
1026
1027 (defun help-xref-go-back ()
1028   "Go back to the previous help buffer using info on `help-xref-stack'."
1029   (interactive)
1030   (when help-xref-stack
1031     (setq help-xref-stack (cdr help-xref-stack)) ; due to help-follow
1032     (let* ((item (car help-xref-stack))
1033            (method (car item))
1034            (args (cdr item)))
1035       (setq help-xref-stack (cdr help-xref-stack))
1036       (if (listp args)
1037           (apply method args)
1038         (funcall method args)))))
1039
1040 (defun help-go-back ()
1041   (interactive)
1042   (help-follow (1- (point-max))))
1043
1044 (defun help-follow (&optional pos)
1045   "Follow cross-reference at POS, defaulting to point.
1046
1047 For the cross-reference format, see `help-make-xrefs'."
1048   (interactive "d")
1049   (let* ((help-data (get-text-property pos 'help-xref))
1050          (method (car help-data))
1051          (args (cdr help-data)))
1052     (setq help-xref-stack (cons help-xref-stack-item help-xref-stack))
1053     (setq help-xref-stack-item nil)
1054     (when help-data
1055       ;; There is a reference at point.  Follow it.
1056       (apply method args))))
1057
1058 ;; For tabbing through buffer.
1059 (defun help-next-ref ()
1060   "Find the next help cross-reference in the buffer."
1061   (interactive)
1062   (let (pos)
1063     (while (not pos)
1064       (if (get-text-property (point) 'help-xref) ; move off reference
1065            (goto-char (or (next-single-property-change (point) 'help-xref)
1066                           (point))))
1067       (cond ((setq pos (next-single-property-change (point) 'help-xref))
1068              (if pos (goto-char pos)))
1069             ((bobp)
1070              (message "No cross references in the buffer.")
1071              (setq pos t))
1072             (t                          ; be circular
1073              (goto-char (point-min)))))))
1074
1075 (defun help-previous-ref ()
1076   "Find the previous help cross-reference in the buffer."
1077   (interactive)
1078   (let (pos)
1079     (while (not pos)
1080       (if (get-text-property (point) 'help-xref) ; move off reference
1081           (goto-char (or (previous-single-property-change (point) 'help-xref)
1082                          (point))))
1083       (cond ((setq pos (previous-single-property-change (point) 'help-xref))
1084              (if pos (goto-char pos)))
1085             ((bobp)
1086              (message "No cross references in the buffer.")
1087              (setq pos t))
1088             (t                          ; be circular
1089              (goto-char (point-max)))))))
1090
1091 ;;; help.el ends here