lisp/help.el

   1 ;;; help.el --- help commands for Emacs
   2
   3 ;; Copyright (C) 1985, 1986, 1993, 1994, 1998, 1999, 2000 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 (eval-when-compile (require 'view))
  36
  37 (defvar help-map (make-sparse-keymap)
  38   "Keymap for characters following the Help key.")
  39
  40 (defvar help-mode-map (make-sparse-keymap)
  41   "Keymap for help mode.")
  42
  43 (define-key global-map (char-to-string help-char) 'help-command)
  44 (define-key global-map [help] 'help-command)
  45 (define-key global-map [f1] 'help-command)
  46 (fset 'help-command help-map)
  47
  48 (define-key help-map (char-to-string help-char) 'help-for-help)
  49 (define-key help-map [help] 'help-for-help)
  50 (define-key help-map [f1] 'help-for-help)
  51 (define-key help-map "?" 'help-for-help)
  52
  53 (define-key help-map "\C-c" 'describe-copying)
  54 (define-key help-map "\C-d" 'describe-distribution)
  55 (define-key help-map "\C-w" 'describe-no-warranty)
  56 (define-key help-map "\C-p" 'describe-project)
  57 (define-key help-map "a" 'apropos-command)
  58
  59 (define-key help-map "b" 'describe-bindings)
  60
  61 (define-key help-map "c" 'describe-key-briefly)
  62 (define-key help-map "k" 'describe-key)
  63
  64 (define-key help-map "d" 'describe-function)
  65 (define-key help-map "f" 'describe-function)
  66
  67 (define-key help-map "F" 'view-emacs-FAQ)
  68
  69 (define-key help-map "i" 'info)
  70 (define-key help-map "4i" 'info-other-window)
  71 (define-key help-map "\C-f" 'Info-goto-emacs-command-node)
  72 (define-key help-map "\C-k" 'Info-goto-emacs-key-command-node)
  73 (define-key help-map "\C-i" 'info-lookup-symbol)
  74
  75 (define-key help-map "l" 'view-lossage)
  76
  77 (define-key help-map "m" 'describe-mode)
  78
  79 (define-key help-map "\C-n" 'view-emacs-news)
  80 (define-key help-map "n" 'view-emacs-news)
  81
  82 (define-key help-map "p" 'finder-by-keyword)
  83 (autoload 'finder-by-keyword "finder"
  84   "Find packages matching a given keyword." t)
  85
  86 (define-key help-map "P" 'view-emacs-problems)
  87
  88 (define-key help-map "s" 'describe-syntax)
  89
  90 (define-key help-map "t" 'help-with-tutorial)
  91
  92 (define-key help-map "w" 'where-is)
  93
  94 (define-key help-map "v" 'describe-variable)
  95
  96 (define-key help-map "q" 'help-quit)
  97
  98 (define-key help-mode-map [mouse-2] 'help-follow-mouse)
  99 (define-key help-mode-map "\C-c\C-b" 'help-go-back)
 100 (define-key help-mode-map "\C-c\C-c" 'help-follow)
 101 (define-key help-mode-map "\t" 'help-next-ref)
 102 (define-key help-mode-map [backtab] 'help-previous-ref)
 103 (define-key help-mode-map [(shift tab)] 'help-previous-ref)
 104 ;; Documentation only, since we use minor-mode-overriding-map-alist.
 105 (define-key help-mode-map "\r" 'help-follow)
 106
 107 (defvar help-xref-stack nil
 108   "A stack of ways by which to return to help buffers after following xrefs.
 109 Used by `help-follow' and `help-xref-go-back'.
 110 An element looks like (POSITION FUNCTION ARGS...), where POSITION is
 111 `(POINT . BUFFER-NAME)'.
 112 To use the element, do (apply FUNCTION ARGS) then goto the point in
 113 the named buffer.")
 114 (put 'help-xref-stack 'permanent-local t)
 115
 116 (defvar help-xref-stack-item nil
 117   "An item for `help-follow' in this buffer to push onto `help-xref-stack'.
 118 The format is (FUNCTION ARGS...).")
 119 (put 'help-xref-stack-item 'permanent-local t)
 120
 121 (setq-default help-xref-stack nil help-xref-stack-item nil)
 122
 123 (defcustom help-mode-hook nil
 124   "Hook run by `help-mode'."
 125   :type 'hook
 126   :group 'help)
 127
 128 (defun help-mode ()
 129   "Major mode for viewing help text and navigating references in it.
 130 Entry to this mode runs the normal hook `help-mode-hook'.
 131 Commands:
 132 \\{help-mode-map}"
 133   (interactive)
 134   (kill-all-local-variables)
 135   (use-local-map help-mode-map)
 136   (setq mode-name "Help")
 137   (setq major-mode 'help-mode)
 138   (make-local-variable 'font-lock-defaults)
 139   (setq font-lock-defaults nil)         ; font-lock would defeat xref
 140   (view-mode)
 141   (make-local-variable 'view-no-disable-on-exit)
 142   (setq view-no-disable-on-exit t)
 143   ;; `help-make-xrefs' would be run here if not invoked from
 144   ;; `help-mode-maybe'.
 145   (run-hooks 'help-mode-hook))
 146
 147 (defun help-mode-setup ()
 148   (help-mode)
 149   (setq buffer-read-only nil))
 150
 151 (add-hook 'temp-buffer-setup-hook 'help-mode-setup)
 152
 153 (defun help-mode-finish ()
 154   (when (eq major-mode 'help-mode)
 155     ;; View mode's read-only status of existing *Help* buffer is lost
 156     ;; by with-output-to-temp-buffer.
 157     (toggle-read-only 1)
 158     (help-make-xrefs (current-buffer)))
 159   (setq view-return-to-alist
 160         (list (cons (selected-window) help-return-method))))
 161
 162 (add-hook 'temp-buffer-show-hook 'help-mode-finish)
 163
 164 (defun help-quit ()
 165   "Just exit from the Help command's command loop."
 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 mode-line-key-binding (key)
 210   "Value is the binding of KEY in the mode line or nil if none."
 211   (let (string-info defn)
 212     (when (and (eq 'mode-line (aref key 0))
 213                (consp (setq string-info (nth 4 (event-start (aref key 1))))))
 214     (let* ((string (car string-info))
 215            (pos (cdr string-info))
 216            (local-map (and (> pos 0)
 217                            (< pos (length string))
 218                            (get-text-property pos 'local-map string))))
 219       (setq defn (and local-map (lookup-key local-map key)))))
 220     defn))
 221
 222 (defun describe-key-briefly (key &optional insert)
 223   "Print the name of the function KEY invokes.  KEY is a string.
 224 If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
 225   (interactive "kDescribe key briefly: \nP")
 226   (save-excursion
 227     (let ((modifiers (event-modifiers (aref key 0)))
 228           (standard-output (if insert (current-buffer) t))
 229           window position)
 230       ;; For a mouse button event, go to the button it applies to
 231       ;; to get the right key bindings.  And go to the right place
 232       ;; in case the keymap depends on where you clicked.
 233       (if (or (memq 'click modifiers) (memq 'down modifiers)
 234               (memq 'drag modifiers))
 235           (setq window (posn-window (event-start (aref key 0)))
 236                 position (posn-point (event-start (aref key 0)))))
 237       (if (windowp window)
 238           (progn
 239             (set-buffer (window-buffer window))
 240             (goto-char position)))
 241       ;; Ok, now look up the key and name the command.
 242       (let ((defn (or (mode-line-key-binding key)
 243                       (key-binding key)))
 244             (key-desc (key-description key)))
 245         (if (or (null defn) (integerp defn))
 246             (princ (format "%s is undefined" key-desc))
 247           (princ (format (if insert
 248                              "`%s' (`%s')"
 249                            (if (windowp window)
 250                                "%s at that spot runs the command %s"
 251                              "%s runs the command %s"))
 252                          key-desc
 253                          (if (symbolp defn) defn (prin1-to-string defn)))))))))
 254
 255 (defvar help-return-method nil
 256   "What to do to \"exit\" the help buffer.
 257 This is a list
 258  (WINDOW . t)              delete the selected window, go to WINDOW.
 259  (WINDOW . quit-window)    do quit-window, then select WINDOW.
 260  (WINDOW BUF START POINT)  display BUF at START, POINT, then select WINDOW.")
 261
 262 (defun print-help-return-message (&optional function)
 263   "Display or return message saying how to restore windows after help command.
 264 Computes a message and applies the optional argument FUNCTION to it.
 265 If FUNCTION is nil, applies `message' to it, thus printing it."
 266   (and (not (get-buffer-window standard-output))
 267        (let ((first-message
 268               (cond ((special-display-p (buffer-name standard-output))
 269                      (setq help-return-method (cons (selected-window) t))
 270                      ;; If the help output buffer is a special display buffer,
 271                      ;; don't say anything about how to get rid of it.
 272                      ;; First of all, the user will do that with the window
 273                      ;; manager, not with Emacs.
 274                      ;; Secondly, the buffer has not been displayed yet,
 275                      ;; so we don't know whether its frame will be selected.
 276                      nil)
 277                     (display-buffer-reuse-frames
 278                      (setq help-return-method (cons (selected-window)
 279                                                     'quit-window))
 280                      nil)
 281                     ((not (one-window-p t))
 282                      (setq help-return-method
 283                            (cons (selected-window) 'quit-window))
 284                      "Type \\[switch-to-buffer-other-window] RET to restore the other window.")
 285                     (pop-up-windows
 286                      (setq help-return-method (cons (selected-window) t))
 287                      "Type \\[delete-other-windows] to remove help window.")
 288                     (t
 289                      (setq help-return-method
 290                            (list (selected-window) (window-buffer)
 291                                  (window-start) (window-point)))
 292                      "Type \\[switch-to-buffer] RET to remove help window."))))
 293          (funcall (or function 'message)
 294                   (concat
 295                    (if first-message
 296                        (substitute-command-keys first-message))
 297                    (if first-message "  ")
 298                    ;; If the help buffer will go in a separate frame,
 299                    ;; it's no use mentioning a command to scroll, so don't.
 300                    (if (special-display-p (buffer-name standard-output))
 301                        nil
 302                      (if (same-window-p (buffer-name standard-output))
 303                          ;; Say how to scroll this window.
 304                          (substitute-command-keys
 305                           "\\[scroll-up] to scroll the help.")
 306                        ;; Say how to scroll some other window.
 307                        (substitute-command-keys
 308                         "\\[scroll-other-window] to scroll the help."))))))))
 309
 310 (defun describe-key (key)
 311   "Display documentation of the function invoked by KEY.  KEY is a string."
 312   (interactive "kDescribe key: ")
 313   (save-excursion
 314     (let ((modifiers (event-modifiers (aref key 0)))
 315           window position)
 316       ;; For a mouse button event, go to the button it applies to
 317       ;; to get the right key bindings.  And go to the right place
 318       ;; in case the keymap depends on where you clicked.
 319       (if (or (memq 'click modifiers) (memq 'down modifiers)
 320               (memq 'drag modifiers))
 321           (setq window (posn-window (event-start (aref key 0)))
 322                 position (posn-point (event-start (aref key 0)))))
 323       (if (windowp window)
 324           (progn
 325             (set-buffer (window-buffer window))
 326             (goto-char position)))
 327       (let ((defn (or (mode-line-key-binding key) (key-binding key))))
 328         (if (or (null defn) (integerp defn))
 329             (message "%s is undefined" (key-description key))
 330           (with-output-to-temp-buffer "*Help*"
 331             (princ (key-description key))
 332             (if (windowp window)
 333                 (princ " at that spot"))
 334             (princ " runs the command ")
 335             (prin1 defn)
 336             (princ "\n   which is ")
 337             (describe-function-1 defn nil (interactive-p))
 338             (print-help-return-message)))))))
 339
 340 (defun describe-mode ()
 341   "Display documentation of current major mode and minor modes.
 342 The major mode description comes first, followed by the minor modes,
 343 each on a separate page.
 344
 345 For this to work correctly for a minor mode, the mode's indicator variable
 346 \(listed in `minor-mode-alist') must also be a function whose documentation
 347 describes the minor mode."
 348   (interactive)
 349   (with-output-to-temp-buffer "*Help*"
 350     (when minor-mode-alist
 351       (princ "The major mode is described first.
 352 For minor modes, see following pages.\n\n"))
 353     (princ mode-name)
 354     (princ " mode:\n")
 355     (princ (documentation major-mode))
 356     (help-setup-xref (list #'help-xref-mode (current-buffer)) (interactive-p))
 357     (let ((minor-modes minor-mode-alist))
 358       (while minor-modes
 359         (let* ((minor-mode (car (car minor-modes)))
 360                (indicator (car (cdr (car minor-modes)))))
 361           ;; Document a minor mode if it is listed in minor-mode-alist,
 362           ;; bound locally in this buffer, non-nil, and has a function
 363           ;; definition.
 364           (if (and (boundp minor-mode)
 365                    (symbol-value minor-mode)
 366                    (fboundp minor-mode))
 367               (let ((pretty-minor-mode minor-mode))
 368                 (if (string-match "-mode$" (symbol-name minor-mode))
 369                     (setq pretty-minor-mode
 370                           (capitalize
 371                            (substring (symbol-name minor-mode)
 372                                       0 (match-beginning 0)))))
 373                 (while (and indicator (symbolp indicator)
 374                             (boundp indicator)
 375                             (not (eq indicator (symbol-value indicator))))
 376                   (setq indicator (symbol-value indicator)))
 377                 (princ "\n\f\n")
 378                 (princ (format "%s minor mode (%s):\n"
 379                                pretty-minor-mode
 380                                (if indicator
 381                                    (format "indicator%s" indicator)
 382                                  "no indicator")))
 383                 (princ (documentation minor-mode)))))
 384         (setq minor-modes (cdr minor-modes))))
 385     (print-help-return-message)))
 386
 387 ;; So keyboard macro definitions are documented correctly
 388 (fset 'defining-kbd-macro (symbol-function 'start-kbd-macro))
 389
 390 (defun describe-distribution ()
 391   "Display info on how to obtain the latest version of GNU Emacs."
 392   (interactive)
 393   (find-file-read-only
 394    (expand-file-name "DISTRIB" data-directory)))
 395
 396 (defun describe-copying ()
 397   "Display info on how you may redistribute copies of GNU Emacs."
 398   (interactive)
 399   (find-file-read-only
 400    (expand-file-name "COPYING" data-directory))
 401   (goto-char (point-min)))
 402
 403 (defun describe-project ()
 404   "Display info on the GNU project."
 405   (interactive)
 406   (find-file-read-only
 407    (expand-file-name "GNU" data-directory))
 408   (goto-char (point-min)))
 409
 410 (defun describe-no-warranty ()
 411   "Display info on all the kinds of warranty Emacs does NOT have."
 412   (interactive)
 413   (describe-copying)
 414   (let (case-fold-search)
 415     (search-forward "NO WARRANTY")
 416     (recenter 0)))
 417
 418 (defun describe-prefix-bindings ()
 419   "Describe the bindings of the prefix used to reach this command.
 420 The prefix described consists of all but the last event
 421 of the key sequence that ran this command."
 422   (interactive)
 423   (let* ((key (this-command-keys)))
 424     (describe-bindings
 425      (if (stringp key)
 426          (substring key 0 (1- (length key)))
 427        (let ((prefix (make-vector (1- (length key)) nil))
 428              (i 0))
 429          (while (< i (length prefix))
 430            (aset prefix i (aref key i))
 431            (setq i (1+ i)))
 432          prefix)))))
 433 ;; Make C-h after a prefix, when not specifically bound,
 434 ;; run describe-prefix-bindings.
 435 (setq prefix-help-command 'describe-prefix-bindings)
 436
 437 (defun view-emacs-news (&optional arg)
 438   "Display info on recent changes to Emacs.
 439 With numeric argument, display information on correspondingly older changes."
 440   (interactive "P")
 441   (let* ((arg (if arg (prefix-numeric-value arg) 0))
 442          (file (cond ((eq arg 0) "NEWS")
 443                      ((eq arg 1) "ONEWS")
 444                      (t
 445                       (nth (- arg 2)
 446                            (nreverse (directory-files data-directory
 447                                                       nil "^NEWS\\.[0-9]+$"
 448                                                       nil)))))))
 449     (if file
 450         (find-file-read-only (expand-file-name file data-directory))
 451       (error "No such old news"))))
 452
 453 (defun view-emacs-FAQ ()
 454   "Display the Emacs Frequently Asked Questions (FAQ) file."
 455   (interactive)
 456 ;;;  (find-file-read-only (expand-file-name "FAQ" data-directory))
 457   (info "(efaq)"))
 458
 459 (defun view-emacs-problems ()
 460   "Display info on known problems with Emacs and possible workarounds."
 461   (interactive)
 462   (view-file (expand-file-name "PROBLEMS" data-directory)))
 463
 464 (defun view-lossage ()
 465   "Display last 100 input keystrokes."
 466   (interactive)
 467   (with-output-to-temp-buffer "*Help*"
 468     (princ (mapconcat (function (lambda (key)
 469                                   (if (or (integerp key)
 470                                           (symbolp key)
 471                                           (listp key))
 472                                       (single-key-description key)
 473                                     (prin1-to-string key nil))))
 474                       (recent-keys)
 475                       " "))
 476     (save-excursion
 477       (set-buffer standard-output)
 478       (goto-char (point-min))
 479       (while (progn (move-to-column 50) (not (eobp)))
 480         (search-forward " " nil t)
 481         (insert "\n"))
 482       (setq help-xref-stack nil
 483             help-xref-stack-item nil))
 484     (print-help-return-message)))
 485
 486 (defalias 'help 'help-for-help)
 487 (make-help-screen help-for-help
 488   "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:"
 489   "You have typed %THIS-KEY%, the help character.  Type a Help option:
 490 \(Use SPC or DEL to scroll through this text.  Type \\<help-map>\\[help-quit] to exit the Help command.)
 491
 492 a  command-apropos.  Give a substring, and see a list of commands
 493         (functions interactively callable) that contain
 494         that substring.  See also the  apropos  command.
 495 b  describe-bindings.  Display table of all key bindings.
 496 c  describe-key-briefly.  Type a command key sequence;
 497         it prints the function name that sequence runs.
 498 C  describe-coding-system.  This describes either a specific coding system
 499         (if you type its name) or the coding systems currently in use
 500         (if you type just RET).
 501 f  describe-function.  Type a function name and get documentation of it.
 502 C-f Info-goto-emacs-command-node.  Type a function name;
 503         it takes you to the Info node for that command.
 504 i  info. The  info  documentation reader.
 505 I  describe-input-method.  Describe a specific input method (if you type
 506         its name) or the current input method (if you type just RET).
 507 C-i  info-lookup-symbol.  Display the definition of a specific symbol
 508         as found in the manual for the language this buffer is written in.
 509 k  describe-key.  Type a command key sequence;
 510         it displays the full documentation.
 511 C-k Info-goto-emacs-key-command-node.  Type a command key sequence;
 512         it takes you to the Info node for the command bound to that key.
 513 l  view-lossage.  Show last 100 characters you typed.
 514 L  describe-language-environment.  This describes either the a
 515         specific language environment (if you type its name)
 516         or the current language environment (if you type just RET).
 517 m  describe-mode.  Print documentation of current minor modes,
 518         and the current major mode, including their special commands.
 519 n  view-emacs-news.  Display news of recent Emacs changes.
 520 p  finder-by-keyword. Find packages matching a given topic keyword.
 521 s  describe-syntax.  Display contents of syntax table, plus explanations
 522 t  help-with-tutorial.  Select the Emacs learn-by-doing tutorial.
 523 v  describe-variable.  Type name of a variable;
 524         it displays the variable's documentation and value.
 525 w  where-is.  Type command name; it prints which keystrokes
 526         invoke that command.
 527
 528 F  Display the frequently asked questions file.
 529 h  Display the HELLO file which illustrates various scripts.
 530 C-c Display Emacs copying permission (General Public License).
 531 C-d Display Emacs ordering information.
 532 C-n Display news of recent Emacs changes.
 533 C-p Display information about the GNU project.
 534 C-w Display information on absence of warranty for GNU Emacs."
 535   help-map)
 536
 537 (defun function-called-at-point ()
 538   "Return a function around point or else called by the list containing point.
 539 If that doesn't give a function, return nil."
 540   (with-syntax-table emacs-lisp-mode-syntax-table
 541     (or (condition-case ()
 542             (save-excursion
 543               (or (not (zerop (skip-syntax-backward "_w")))
 544                   (eq (char-syntax (following-char)) ?w)
 545                   (eq (char-syntax (following-char)) ?_)
 546                   (forward-sexp -1))
 547               (skip-chars-forward "'")
 548               (let ((obj (read (current-buffer))))
 549                 (and (symbolp obj) (fboundp obj) obj)))
 550           (error nil))
 551         (condition-case ()
 552             (save-excursion
 553               (save-restriction
 554                 (narrow-to-region (max (point-min)
 555                                        (- (point) 1000)) (point-max))
 556                 ;; Move up to surrounding paren, then after the open.
 557                 (backward-up-list 1)
 558                 (forward-char 1)
 559                 ;; If there is space here, this is probably something
 560                 ;; other than a real Lisp function call, so ignore it.
 561                 (if (looking-at "[ \t]")
 562                     (error "Probably not a Lisp function call"))
 563                 (let ((obj (read (current-buffer))))
 564                   (and (symbolp obj) (fboundp obj) obj))))
 565           (error nil)))))
 566
 567 (defvar symbol-file-load-history-loaded nil
 568   "Non-nil means we have loaded the file `fns-VERSION.el' in `exec-directory'.
 569 That file records the part of `load-history' for preloaded files,
 570 which is cleared out before dumping to make Emacs smaller.")
 571
 572 (defun symbol-file (function)
 573   "Return the input source from which FUNCTION was loaded.
 574 The value is normally a string that was passed to `load':
 575 either an absolute file name, or a library name
 576 \(with no directory name and no `.el' or `.elc' at the end).
 577 It can also be nil, if the definition is not associated with any file."
 578   (unless symbol-file-load-history-loaded
 579     (load (expand-file-name
 580            ;; fns-XX.YY.ZZ.el does not work on DOS filesystem.
 581            (if (eq system-type 'ms-dos)
 582                "fns.el"
 583              (format "fns-%s.el" emacs-version))
 584            exec-directory)
 585           ;; The file name fns-%s.el already has a .el extension.
 586           nil nil t)
 587     (setq symbol-file-load-history-loaded t))
 588   (let ((files load-history)
 589         file functions)
 590     (while files
 591       (if (memq function (cdr (car files)))
 592           (setq file (car (car files)) files nil))
 593       (setq files (cdr files)))
 594     file))
 595
 596 (defun describe-function (function)
 597   "Display the full documentation of FUNCTION (a symbol)."
 598   (interactive
 599    (let ((fn (function-called-at-point))
 600          (enable-recursive-minibuffers t)
 601          val)
 602      (setq val (completing-read (if fn
 603                                     (format "Describe function (default %s): " fn)
 604                                   "Describe function: ")
 605                                 obarray 'fboundp t nil nil (symbol-name fn)))
 606      (list (if (equal val "")
 607                fn (intern val)))))
 608   (if function
 609       (with-output-to-temp-buffer "*Help*"
 610         (prin1 function)
 611         ;; Use " is " instead of a colon so that
 612         ;; it is easier to get out the function name using forward-sexp.
 613         (princ " is ")
 614         (describe-function-1 function nil (interactive-p))
 615         (print-help-return-message)
 616         (save-excursion
 617           (set-buffer standard-output)
 618           ;; Return the text we displayed.
 619           (buffer-string)))
 620     (message "You didn't specify a function")))
 621
 622 (defun describe-function-1 (function parens interactive-p)
 623   (let* ((def (if (symbolp function)
 624                   (symbol-function function)
 625                 function))
 626          file-name string need-close
 627          (beg (if (commandp def) "an interactive " "a ")))
 628     (setq string
 629           (cond ((or (stringp def)
 630                      (vectorp def))
 631                  "a keyboard macro")
 632                 ((subrp def)
 633                  (if (eq 'unevalled (cdr (subr-arity def)))
 634                      (concat beg "special form")
 635                    (concat beg "built-in function")))
 636                 ((byte-code-function-p def)
 637                  (concat beg "compiled Lisp function"))
 638                 ((symbolp def)
 639                  (while (symbolp (symbol-function def))
 640                    (setq def (symbol-function def)))
 641                  (format "an alias for `%s'" def))
 642                 ((eq (car-safe def) 'lambda)
 643                  (concat beg "Lisp function"))
 644                 ((eq (car-safe def) 'macro)
 645                  "a Lisp macro")
 646                 ((eq (car-safe def) 'mocklisp)
 647                  "a mocklisp function")
 648                 ((eq (car-safe def) 'autoload)
 649                  (setq file-name (nth 1 def))
 650                  (format "%s autoloaded %s"
 651                          (if (commandp def) "an interactive" "an")
 652                          (if (eq (nth 4 def) 'keymap) "keymap"
 653                            (if (nth 4 def) "Lisp macro" "Lisp function"))
 654                          ))
 655                 ;; perhaps use keymapp here instead
 656                 ((eq (car-safe def) 'keymap)
 657                  (let ((is-full nil)
 658                        (elts (cdr-safe def)))
 659                    (while elts
 660                      (if (char-table-p (car-safe elts))
 661                          (setq is-full t
 662                                elts nil))
 663                      (setq elts (cdr-safe elts)))
 664                    (if is-full
 665                        "a full keymap"
 666                      "a sparse keymap")))
 667                 (t "")))
 668     (when (and parens (not (equal string "")))
 669       (setq need-close t)
 670       (princ "("))
 671     (princ string)
 672     (with-current-buffer "*Help*"
 673       (save-excursion
 674         (save-match-data
 675           (if (re-search-backward "alias for `\\([^`']+\\)'" nil t)
 676               (help-xref-button 1 #'describe-function def
 677                                 "mouse-2, RET: describe this function")))))
 678     (or file-name
 679         (setq file-name (symbol-file function)))
 680     (if file-name
 681         (progn
 682           (princ " in `")
 683           ;; We used to add .el to the file name,
 684           ;; but that's completely wrong when the user used load-file.
 685           (princ file-name)
 686           (princ "'")
 687           ;; Make a hyperlink to the library.
 688           (with-current-buffer "*Help*"
 689             (save-excursion
 690               (re-search-backward "`\\([^`']+\\)'" nil t)
 691               (help-xref-button 1 #'(lambda (arg)
 692                                       (let ((location
 693                                              (find-function-noselect arg)))
 694                                         (pop-to-buffer (car location))
 695                                         (goto-char (cdr location))))
 696                                 function
 697                                 "mouse-2, RET: find function's definition")))))
 698     (if need-close (princ ")"))
 699     (princ ".")
 700     (terpri)
 701     ;; Handle symbols aliased to other symbols.
 702     (setq def (indirect-function def))
 703     ;; If definition is a macro, find the function inside it.
 704     (if (eq (car-safe def) 'macro)
 705         (setq def (cdr def)))
 706     (let ((arglist (cond ((byte-code-function-p def)
 707                           (car (append def nil)))
 708                          ((eq (car-safe def) 'lambda)
 709                           (nth 1 def))
 710                          ((and (eq (car-safe def) 'autoload)
 711                                (not (eq (nth 4 def) 'keymap)))
 712                           (concat "[Arg list not available until "
 713                                   "function definition is loaded.]"))
 714                          (t t))))
 715       (cond ((listp arglist)
 716              (princ (cons (if (symbolp function) function "anonymous")
 717                           (mapcar (lambda (arg)
 718                                     (if (memq arg '(&optional &rest))
 719                                         arg
 720                                       (intern (upcase (symbol-name arg)))))
 721                                   arglist)))
 722              (terpri))
 723             ((stringp arglist)
 724              (princ arglist)
 725              (terpri))))
 726     (let ((doc (documentation function)))
 727       (if doc
 728           (progn (terpri)
 729                  (princ doc)
 730                  (if (subrp (symbol-function function))
 731                      (with-current-buffer standard-output
 732                        (beginning-of-line)
 733                        ;; Builtins get the calling sequence at the end of
 734                        ;; the doc string.  Move it to the same place as
 735                        ;; for other functions.
 736
 737                        ;; In cases where `function' has been fset to a
 738                        ;; subr we can't search for function's name in
 739                        ;; the doc string.  Kluge round that using the
 740                        ;; printed representation.  The arg list then
 741                        ;; shows the wrong function name, but that
 742                        ;; might be a useful hint.
 743                        (let* ((rep (prin1-to-string def))
 744                               (name (progn
 745                                       (string-match " \\([^ ]+\\)>$" rep)
 746                                       (match-string 1 rep))))
 747                          (if (looking-at (format "(%s[ )]" name))
 748                              (let ((start (point-marker)))
 749                                (goto-char (point-min))
 750                                (forward-paragraph)
 751                                (insert-buffer-substring (current-buffer) start)
 752                                (insert ?\n)
 753                                (delete-region (1- start) (point-max)))
 754                            (goto-char (point-min))
 755                            (forward-paragraph)
 756                            (insert
 757                             "[Missing arglist.  Please make a bug report.]\n")))
 758                        (goto-char (point-max))))
 759                  (help-setup-xref (list #'describe-function function)
 760                                   interactive-p))
 761         (princ "not documented")))))
 762
 763 (defun variable-at-point ()
 764   "Return the bound variable symbol found around point.
 765 Return 0 if there is no such symbol."
 766   (condition-case ()
 767       (with-syntax-table emacs-lisp-mode-syntax-table
 768         (save-excursion
 769           (or (not (zerop (skip-syntax-backward "_w")))
 770               (eq (char-syntax (following-char)) ?w)
 771               (eq (char-syntax (following-char)) ?_)
 772               (forward-sexp -1))
 773           (skip-chars-forward "'")
 774           (let ((obj (read (current-buffer))))
 775             (or (and (symbolp obj) (boundp obj) obj)
 776                 0))))
 777     (error 0)))
 778
 779 (defun help-xref-on-pp (from to)
 780   "Add xrefs for symbols in `pp's output between FROM and TO."
 781   (let ((ost (syntax-table)))
 782     (unwind-protect
 783         (save-excursion
 784           (save-restriction
 785             (set-syntax-table emacs-lisp-mode-syntax-table)
 786             (narrow-to-region from to)
 787             (goto-char (point-min))
 788             (while (not (eobp))
 789               (cond
 790                ((looking-at "\"") (forward-sexp 1))
 791                ((looking-at "#<") (search-forward ">" nil 'move))
 792                ((looking-at "\\(\\(\\sw\\|\\s_\\)+\\)")
 793                 (let* ((sym (intern-soft
 794                              (buffer-substring (match-beginning 1)
 795                                                (match-end 1))))
 796                        (fn (cond ((fboundp sym) #'describe-function)
 797                                  ((or (memq sym '(t nil))
 798                                       (keywordp sym))
 799                                   nil)
 800                                  ((and sym (boundp sym))
 801                                   #'describe-variable))))
 802                   (when fn (help-xref-button 1 fn sym)))
 803                 (goto-char (match-end 1)))
 804                (t (forward-char 1))))))
 805       (set-syntax-table ost))))
 806
 807 (defun describe-variable (variable)
 808   "Display the full documentation of VARIABLE (a symbol).
 809 Returns the documentation as a string, also."
 810   (interactive
 811    (let ((v (variable-at-point))
 812          (enable-recursive-minibuffers t)
 813          val)
 814      (setq val (completing-read (if (symbolp v)
 815                                     (format
 816                                      "Describe variable (default %s): " v)
 817                                   "Describe variable: ")
 818                                 obarray 'boundp t nil nil
 819                                 (if (symbolp v) (symbol-name v))))
 820      (list (if (equal val "")
 821                v (intern val)))))
 822   (if (symbolp variable)
 823       (let (valvoid)
 824         (with-output-to-temp-buffer "*Help*"
 825           (prin1 variable)
 826           (if (not (boundp variable))
 827               (progn
 828                 (princ " is void")
 829                 (setq valvoid t))
 830             (let ((val (symbol-value variable)))
 831               (with-current-buffer standard-output
 832                 (princ "'s value is ")
 833                 (terpri)
 834                 (let ((from (point)))
 835                   (pp val)
 836                   (help-xref-on-pp from (point))))))
 837           (terpri)
 838           (if (local-variable-p variable)
 839               (progn
 840                 (princ (format "Local in buffer %s; " (buffer-name)))
 841                 (if (not (default-boundp variable))
 842                     (princ "globally void")
 843                   (let ((val (default-value variable)))
 844                     (with-current-buffer standard-output
 845                       (princ "global value is ")
 846                       (terpri)
 847                       ;; Fixme: pp can take an age if you happen to
 848                       ;; ask for a very large expression.  We should
 849                       ;; probably print it raw once and check it's a
 850                       ;; sensible size before prettyprinting.  -- fx
 851                       (let ((from (point)))
 852                         (pp val)
 853                         (help-xref-on-pp from (point))))))
 854                 (terpri)))
 855           (terpri)
 856           (save-current-buffer
 857             (set-buffer standard-output)
 858             (if (> (count-lines (point-min) (point-max)) 10)
 859                 (progn
 860                   ;; Note that setting the syntax table like below
 861                   ;; makes forward-sexp move over a `'s' at the end
 862                   ;; of a symbol.
 863                   (set-syntax-table emacs-lisp-mode-syntax-table)
 864                   (goto-char (point-min))
 865                   (if valvoid
 866                       (forward-line 1)
 867                     (forward-sexp 1)
 868                     (delete-region (point) (progn (end-of-line) (point)))
 869                     (insert " value is shown below.\n\n")
 870                     (save-excursion
 871                       (insert "\n\nValue:"))))))
 872           (princ "Documentation:")
 873           (terpri)
 874           (let ((doc (documentation-property variable 'variable-documentation)))
 875             (princ (or doc "not documented as a variable.")))
 876           (help-setup-xref (list #'describe-variable variable) (interactive-p))
 877
 878           ;; Make a link to customize if this variable can be customized.
 879           ;; Note, it is not reliable to test only for a custom-type property
 880           ;; because those are only present after the var's definition
 881           ;; has been loaded.
 882           (if (or (get variable 'custom-type) ; after defcustom
 883                   (get variable 'custom-loads) ; from loaddefs.el
 884                   (get variable 'standard-value)) ; from cus-start.el
 885               (let ((customize-label "customize"))
 886                 (terpri)
 887                 (terpri)
 888                 (princ (concat "You can " customize-label " this variable."))
 889                 (with-current-buffer "*Help*"
 890                   (save-excursion
 891                     (re-search-backward
 892                      (concat "\\(" customize-label "\\)") nil t)
 893                     (help-xref-button 1 (lambda (v)
 894                                           (if help-xref-stack
 895                                               (pop help-xref-stack))
 896                                           (customize-variable v))
 897                                       variable
 898                                       "mouse-2, RET: customize variable")))))
 899           ;; Make a hyperlink to the library if appropriate.  (Don't
 900           ;; change the format of the buffer's initial line in case
 901           ;; anything expects the current format.)
 902           (let ((file-name (symbol-file variable)))
 903             (when file-name
 904               (princ "\n\nDefined in `")
 905               (princ file-name)
 906               (princ "'.")
 907               (with-current-buffer "*Help*"
 908                 (save-excursion
 909                   (re-search-backward "`\\([^`']+\\)'" nil t)
 910                   (help-xref-button
 911                    1 (lambda (arg)
 912                        (let ((location
 913                               (find-variable-noselect arg)))
 914                          (pop-to-buffer (car location))
 915                          (goto-char (cdr location))))
 916                    variable "mouse-2, RET: find variable's definition")))))
 917
 918           (print-help-return-message)
 919           (save-excursion
 920             (set-buffer standard-output)
 921             ;; Return the text we displayed.
 922             (buffer-string))))
 923     (message "You did not specify a variable")))
 924
 925 (defun describe-bindings (&optional prefix buffer)
 926   "Show a list of all defined keys, and their definitions.
 927 We put that list in a buffer, and display the buffer.
 928
 929 The optional argument PREFIX, if non-nil, should be a key sequence;
 930 then we display only bindings that start with that prefix.
 931 The optional argument BUFFER specifies which buffer's bindings
 932 to display (default, the current buffer)."
 933   (interactive "P")
 934   (or buffer (setq buffer (current-buffer)))
 935   (with-current-buffer buffer
 936     (describe-bindings-internal nil prefix))
 937   (with-current-buffer "*Help*"
 938     (help-setup-xref (list #'describe-bindings prefix buffer)
 939                      (interactive-p))))
 940
 941 (defun where-is (definition &optional insert)
 942   "Print message listing key sequences that invoke the command DEFINITION.
 943 Argument is a command definition, usually a symbol with a function definition.
 944 If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
 945   (interactive
 946    (let ((fn (function-called-at-point))
 947          (enable-recursive-minibuffers t)
 948          val)
 949      (setq val (completing-read (if fn
 950                                     (format "Where is command (default %s): " fn)
 951                                   "Where is command: ")
 952                                 obarray 'commandp t))
 953      (list (if (equal val "")
 954                fn (intern val))
 955            current-prefix-arg)))
 956   (let* ((keys (where-is-internal definition overriding-local-map nil nil))
 957          (keys1 (mapconcat 'key-description keys ", "))
 958          (standard-output (if insert (current-buffer) t)))
 959     (if insert
 960         (if (> (length keys1) 0)
 961             (princ (format "%s (%s)" keys1 definition))
 962           (princ (format "M-x %s RET" definition)))
 963       (if (> (length keys1) 0)
 964           (princ (format "%s is on %s" definition keys1))
 965         (princ (format "%s is not on any key" definition)))))
 966   nil)
 967
 968 (defun locate-library (library &optional nosuffix path interactive-call)
 969   "Show the precise file name of Emacs library LIBRARY.
 970 This command searches the directories in `load-path' like `M-x load-library'
 971 to find the file that `M-x load-library RET LIBRARY RET' would load.
 972 Optional second arg NOSUFFIX non-nil means don't add suffixes `.elc' or `.el'
 973 to the specified name LIBRARY.
 974
 975 If the optional third arg PATH is specified, that list of directories
 976 is used instead of `load-path'.
 977
 978 When called from a program, the file name is normaly returned as a
 979 string.  When run interactively, the argument INTERACTIVE-CALL is t,
 980 and the file name is displayed in the echo area."
 981   (interactive (list (read-string "Locate library: ")
 982                      nil nil
 983                      t))
 984   (let (result)
 985     (catch 'answer
 986       (mapc
 987        (lambda (dir)
 988          (mapc
 989           (lambda (suf)
 990             (let ((try (expand-file-name (concat library suf) dir)))
 991               (and (file-readable-p try)
 992                    (null (file-directory-p try))
 993                    (progn
 994                      (setq result try)
 995                      (throw 'answer try)))))
 996           (if nosuffix
 997               '("")
 998             '(".elc" ".el" "")
 999 ;;; load doesn't handle this yet.
1000 ;;;         (let ((basic '(".elc" ".el" ""))
1001 ;;;               (compressed '(".Z" ".gz" "")))
1002 ;;;           ;; If autocompression mode is on,
1003 ;;;           ;; consider all combinations of library suffixes
1004 ;;;           ;; and compression suffixes.
1005 ;;;           (if (rassq 'jka-compr-handler file-name-handler-alist)
1006 ;;;               (apply 'nconc
1007 ;;;                      (mapcar (lambda (compelt)
1008 ;;;                                (mapcar (lambda (baselt)
1009 ;;;                                          (concat baselt compelt))
1010 ;;;                                        basic))
1011 ;;;                              compressed))
1012 ;;;             basic))
1013             )))
1014        (or path load-path)))
1015     (and interactive-call
1016          (if result
1017              (message "Library is file %s" result)
1018            (message "No library %s in search path" library)))
1019     result))
1020
1021 \f
1022 ;;; Grokking cross-reference information in doc strings and
1023 ;;; hyperlinking it.
1024
1025 ;; This may have some scope for extension and the same or something
1026 ;; similar should be done for widget doc strings, which currently use
1027 ;; another mechanism.
1028
1029 (defcustom help-highlight-p t
1030   "*If non-nil, `help-make-xrefs' highlight cross-references.
1031 Under a window system it highlights them with face defined by
1032 `help-highlight-face'."
1033  :group 'help
1034  :version "20.3"
1035  :type 'boolean)
1036
1037 (defcustom help-highlight-face 'underline
1038   "Face used by `help-make-xrefs' to highlight cross-references.
1039 Must be previously-defined."
1040   :group 'help
1041   :version "20.3"
1042   :type 'face)
1043
1044 (defvar help-back-label (purecopy "[back]")
1045   "Label to use by `help-make-xrefs' for the go-back reference.")
1046
1047 (defconst help-xref-symbol-regexp
1048   (purecopy (concat "\\(\\<\\(\\(variable\\|option\\)\\|"
1049                     "\\(function\\|command\\)\\|"
1050                     "\\(face\\)\\|"
1051                     "\\(symbol\\)\\)\\s-+\\)?"
1052                     ;; Note starting with word-syntax character:
1053                     "`\\(\\sw\\(\\sw\\|\\s_\\)+\\)'"))
1054   "Regexp matching doc string references to symbols.
1055
1056 The words preceding the quoted symbol can be used in doc strings to
1057 distinguish references to variables, functions and symbols.")
1058
1059 (defconst help-xref-info-regexp
1060   (purecopy "\\<[Ii]nfo[ \t\n]+node[ \t\n]+`\\([^']+\\)'")
1061   "Regexp matching doc string references to an Info node.")
1062
1063 (defun help-setup-xref (item interactive-p)
1064   "Invoked from commands using the \"*Help*\" buffer to install some xref info.
1065
1066 ITEM is a (FUNCTION . ARGS) pair appropriate for recreating the help
1067 buffer after following a reference.  INTERACTIVE-P is non-nil if the
1068 calling command was invoked interactively.  In this case the stack of
1069 items for help buffer \"back\" buttons is cleared."
1070   (if interactive-p
1071       (setq help-xref-stack nil))
1072   (setq help-xref-stack-item item))
1073
1074 (defvar help-xref-following nil
1075   "Non-nil when following a help cross-reference.")
1076
1077 (defun help-make-xrefs (&optional buffer)
1078   "Parse and hyperlink documentation cross-references in the given BUFFER.
1079
1080 Find cross-reference information in a buffer and, if
1081 `help-highlight-p' is non-nil, highlight it with face defined by
1082 `help-highlight-face'; activate such cross references for selection
1083 with `help-follow'.  Cross-references have the canonical form `...'
1084 and the type of reference may be disambiguated by the preceding
1085 word(s) used in `help-xref-symbol-regexp'.
1086
1087 A special reference `back' is made to return back through a stack of
1088 help buffers.  Variable `help-back-label' specifies the text for
1089 that."
1090   (interactive "b")
1091   (save-excursion
1092     (set-buffer (or buffer (current-buffer)))
1093     (goto-char (point-min))
1094     ;; Skip the header-type info, though it might be useful to parse
1095     ;; it at some stage (e.g. "function in `library'").
1096     (forward-paragraph)
1097     (let ((old-modified (buffer-modified-p)))
1098       (let ((stab (syntax-table))
1099             (case-fold-search t)
1100             (inhibit-read-only t))
1101         (set-syntax-table emacs-lisp-mode-syntax-table)
1102         ;; The following should probably be abstracted out.
1103         (unwind-protect
1104             (progn
1105               ;; Info references
1106               (save-excursion
1107                 (while (re-search-forward help-xref-info-regexp nil t)
1108                   (let ((data (match-string 1)))
1109                     (save-match-data
1110                       (unless (string-match "^([^)]+)" data)
1111                         (setq data (concat "(emacs)" data))))
1112                     (help-xref-button 1 #'info data
1113                                       "mouse-2, RET: read this Info node"))))
1114               ;; Quoted symbols
1115               (save-excursion
1116                 (while (re-search-forward help-xref-symbol-regexp nil t)
1117                   (let* ((data (match-string 7))
1118                          (sym (intern-soft data)))
1119                     (if sym
1120                         (cond
1121                          ((match-string 3) ; `variable' &c
1122                           (and (boundp sym) ; `variable' doesn't ensure
1123                                         ; it's actually bound
1124                                (help-xref-button
1125                                 7 #'describe-variable sym
1126                                 "mouse-2, RET: describe this variable")))
1127                          ((match-string 4) ; `function' &c
1128                           (and (fboundp sym) ; similarly
1129                                (help-xref-button
1130                                 7 #'describe-function sym
1131                                 "mouse-2, RET: describe this function")))
1132                          ((match-string 5) ; `face'
1133                           (and (facep sym)
1134                                (help-xref-button 7 #'describe-face sym
1135                                 "mouse-2, RET: describe this face")))
1136                          ((match-string 6)) ; nothing for symbol
1137                          ((and (boundp sym) (fboundp sym))
1138                           ;; We can't intuit whether to use the
1139                           ;; variable or function doc -- supply both.
1140                           (help-xref-button
1141                            7 #'help-xref-interned sym
1142                            "mouse-2, RET: describe this symbol"))
1143                          ((boundp sym)
1144                           (help-xref-button
1145                            7 #'describe-variable sym
1146                            "mouse-2, RET: describe this variable"))
1147                          ((fboundp sym)
1148                           (help-xref-button
1149                            7 #'describe-function sym
1150                            "mouse-2, RET: describe this function"))
1151                          ((facep sym)
1152                           (help-xref-button
1153                            7 #'describe-face sym)))))))
1154               ;; An obvious case of a key substitution:
1155               (save-excursion
1156                 (while (re-search-forward
1157                         ;; Assume command name is only word characters
1158                         ;; and dashes to get things like `use M-x foo.'.
1159                         "\\<M-x\\s-+\\(\\sw\\(\\sw\\|-\\)+\\)" nil t)
1160                   (let ((sym (intern-soft (match-string 1))))
1161                     (if (fboundp sym)
1162                         (help-xref-button
1163                          1 #'describe-function sym
1164                          "mouse-2, RET: describe this command")))))
1165               ;; Look for commands in whole keymap substitutions:
1166               (save-excursion
1167                 ;; Make sure to find the first keymap.
1168                 (goto-char (point-min))
1169                 ;; Find a header and the column at which the command
1170                 ;; name will be found.
1171                 (while (re-search-forward "^key +binding\n\\(-+ +\\)-+\n\n"
1172                                           nil t)
1173                   (let ((col (- (match-end 1) (match-beginning 1))))
1174                     (while
1175                         ;; Ignore single blank lines in table, but not
1176                         ;; double ones, which should terminate it.
1177                         (and (not (looking-at "\n\\s-*\n"))
1178                              (progn
1179                                (and (eolp) (forward-line))
1180                                (end-of-line)
1181                                (skip-chars-backward "^\t\n")
1182                                (if (and (>= (current-column) col)
1183                                         (looking-at "\\(\\sw\\|-\\)+$"))
1184                                    (let ((sym (intern-soft (match-string 0))))
1185                                      (if (fboundp sym)
1186                                          (help-xref-button
1187                                           0 #'describe-function sym
1188                                           "mouse-2, RET: describe this function"))))
1189                                (zerop (forward-line)))))))))
1190           (set-syntax-table stab))
1191         ;; Make a back-reference in this buffer if appropriate.
1192         (when (and help-xref-following help-xref-stack)
1193           (goto-char (point-max))
1194           (save-excursion
1195             (insert "\n\n" help-back-label))
1196           ;; Just to provide the match data:
1197           (looking-at (concat "\n\n\\(" (regexp-quote help-back-label) "\\)"))
1198           (help-xref-button 1 #'help-xref-go-back (current-buffer))))
1199       ;; View mode steals RET from us.
1200       (set (make-local-variable 'minor-mode-overriding-map-alist)
1201            (list (cons 'view-mode
1202                        (let ((map (make-sparse-keymap)))
1203                          (set-keymap-parent map view-mode-map)
1204                          (define-key map "\r" 'help-follow)
1205                          map))))
1206       (set-buffer-modified-p old-modified))))
1207
1208 (defun help-xref-button (match-number function data &optional help-echo)
1209   "Make a hyperlink for cross-reference text previously matched.
1210
1211 MATCH-NUMBER is the subexpression of interest in the last matched
1212 regexp.  FUNCTION is a function to invoke when the button is
1213 activated, applied to DATA.  DATA may be a single value or a list.
1214 See `help-make-xrefs'.
1215 If optional arg HELP-ECHO is supplied, it is used as a help string."
1216   ;; Don't mung properties we've added specially in some instances.
1217   (unless (get-text-property (match-beginning match-number) 'help-xref)
1218     (add-text-properties (match-beginning match-number)
1219                          (match-end match-number)
1220                          (list 'mouse-face 'highlight
1221                                'help-xref (cons function
1222                                                 (if (listp data)
1223                                                     data
1224                                                   (list data)))))
1225     (if help-echo
1226         (put-text-property (match-beginning match-number)
1227                            (match-end match-number)
1228                            'help-echo help-echo))
1229     (if help-highlight-p
1230         (put-text-property (match-beginning match-number)
1231                            (match-end match-number)
1232                            'face help-highlight-face))))
1233
1234 \f
1235 ;; Additional functions for (re-)creating types of help buffers.
1236 (defun help-xref-interned (symbol)
1237   "Follow a hyperlink which appeared to be an arbitrary interned SYMBOL.
1238
1239 Both variable and function documentation are extracted into a single
1240 help buffer."
1241   (let ((fdoc (when (fboundp symbol) (describe-function symbol)))
1242         (facedoc (when (facep symbol) (describe-face symbol))))
1243     (when (or (boundp symbol) (not fdoc))
1244       (describe-variable symbol)
1245       ;; We now have a help buffer on the variable.  Insert the function
1246       ;; text before it.
1247       (when (or fdoc facedoc)
1248         (with-current-buffer "*Help*"
1249           (goto-char (point-min))
1250           (let ((inhibit-read-only t))
1251             (when fdoc
1252               (insert fdoc "\n\n"))
1253             (when facedoc
1254               (insert (make-string 30 ?-) "\n\n" (symbol-name symbol)
1255                       " is also a " "face." "\n\n" facedoc "\n\n"))
1256             (insert (make-string 30 ?-) "\n\n" (symbol-name symbol)
1257                     " is also a " "variable." "\n\n"))
1258           (help-setup-xref (list #'help-xref-interned symbol) nil))))))
1259
1260 (defun help-xref-mode (buffer)
1261   "Do a `describe-mode' for the specified BUFFER."
1262   (save-excursion
1263     (set-buffer buffer)
1264     (describe-mode)))
1265 \f
1266 ;;; Navigation/hyperlinking with xrefs
1267
1268 (defun help-follow-mouse (click)
1269   "Follow the cross-reference that you click on."
1270   (interactive "e")
1271   (let* ((start (event-start click))
1272          (window (car start))
1273          (pos (car (cdr start))))
1274     (with-current-buffer (window-buffer window)
1275       (help-follow pos))))
1276
1277 (defun help-xref-go-back (buffer)
1278   "From BUFFER, go back to previous help buffer text using `help-xref-stack'."
1279   (let (item position method args)
1280     (with-current-buffer buffer
1281       (when help-xref-stack
1282         (setq help-xref-stack (cdr help-xref-stack)) ; due to help-follow
1283         (setq item (pop help-xref-stack)
1284               position (car item)
1285               method (cadr item)
1286               args (cddr item))))
1287     (apply method args)
1288     ;; We assume that the buffer we just recreated has the saved name,
1289     ;; which might not always be true.
1290     (when (get-buffer (cdr position))
1291       (with-current-buffer (cdr position)
1292         (goto-char (car position))))))
1293
1294 (defun help-go-back ()
1295   "Invoke the [back] button (if any) in the Help mode buffer."
1296   (interactive)
1297   (help-follow (1- (point-max))))
1298
1299 (defun help-follow (&optional pos)
1300   "Follow cross-reference at POS, defaulting to point.
1301
1302 For the cross-reference format, see `help-make-xrefs'."
1303   (interactive "d")
1304   (unless pos
1305     (setq pos (point)))
1306   (let* ((help-data
1307           (or (and (not (= pos (point-max)))
1308                    (get-text-property pos 'help-xref))
1309               (and (not (= pos (point-min)))
1310                    (get-text-property (1- pos) 'help-xref))
1311               ;; check if the symbol under point is a function or variable
1312               (let ((sym
1313                      (intern
1314                       (save-excursion
1315                         (goto-char pos) (skip-syntax-backward "w_")
1316                         (buffer-substring (point)
1317                                           (progn (skip-syntax-forward "w_")
1318                                                  (point)))))))
1319                 (when (or (boundp sym) (fboundp sym))
1320                   (list #'help-xref-interned sym)))))
1321          (method (car help-data))
1322          (args (cdr help-data)))
1323     (when help-data
1324       (setq help-xref-stack (cons (cons (cons pos (buffer-name))
1325                                         help-xref-stack-item)
1326                                   help-xref-stack))
1327       (setq help-xref-stack-item nil)
1328       ;; There is a reference at point.  Follow it.
1329       (let ((help-xref-following t))
1330         (apply method args)))))
1331
1332 ;; For tabbing through buffer.
1333 (defun help-next-ref ()
1334   "Find the next help cross-reference in the buffer."
1335   (interactive)
1336   (let (pos)
1337     (while (not pos)
1338       (if (get-text-property (point) 'help-xref) ; move off reference
1339            (goto-char (or (next-single-property-change (point) 'help-xref)
1340                           (point))))
1341       (cond ((setq pos (next-single-property-change (point) 'help-xref))
1342              (if pos (goto-char pos)))
1343             ((bobp)
1344              (message "No cross references in the buffer.")
1345              (setq pos t))
1346             (t                          ; be circular
1347              (goto-char (point-min)))))))
1348
1349 (defun help-previous-ref ()
1350   "Find the previous help cross-reference in the buffer."
1351   (interactive)
1352   (let (pos)
1353     (while (not pos)
1354       (if (get-text-property (point) 'help-xref) ; move off reference
1355           (goto-char (or (previous-single-property-change (point) 'help-xref)
1356                          (point))))
1357       (cond ((setq pos (previous-single-property-change (point) 'help-xref))
1358              (if pos (goto-char pos)))
1359             ((bobp)
1360              (message "No cross references in the buffer.")
1361              (setq pos t))
1362             (t                          ; be circular
1363              (goto-char (point-max)))))))
1364
1365 \f
1366 ;;; Automatic resizing of temporary buffers.
1367
1368 (defcustom temp-buffer-resize-mode nil
1369   "Non-nil means resize windows displaying temporary buffers.
1370 This makes the window the right height for its contents, but never
1371 more than `temp-buffer-max-height' nor less than `window-min-height'.
1372 This applies to `help', `apropos' and `completion' buffers, and some others.
1373
1374 Setting this variable directly does not take effect;
1375 use either \\[customize] or the function `temp-buffer-resize-mode'."
1376   :get (lambda (symbol)
1377          (and (memq 'resize-temp-buffer-window temp-buffer-show-hook) t))
1378   :set (lambda (symbol value)
1379          (temp-buffer-resize-mode (if value 1 -1)))
1380   :initialize 'custom-initialize-default
1381   :type 'boolean
1382   :group 'help
1383   :version "20.4")
1384
1385 (defcustom temp-buffer-max-height (lambda (buffer) (/ (- (frame-height) 2) 2))
1386   "*Maximum height of a window displaying a temporary buffer.
1387 This is the maximum height (in text lines) which `resize-temp-buffer-window'
1388 will give to a window displaying a temporary buffer.
1389 It can also be a function which will be called with the object corresponding
1390 to the buffer to be displayed as argument and should return an integer
1391 positive number."
1392   :type '(choice integer function)
1393   :group 'help
1394   :version "20.4")
1395
1396 (defun temp-buffer-resize-mode (arg)
1397   "Toggle the mode which that makes windows smaller for temporary buffers.
1398 With prefix argument ARG, turn the resizing of windows displaying temporary
1399 buffers on if ARG is positive or off otherwise.
1400 See the documentation of the variable `temp-buffer-resize-mode' for
1401 more information."
1402   (interactive "P")
1403   (let ((turn-it-on
1404          (if (null arg)
1405              (not (memq 'resize-temp-buffer-window temp-buffer-show-hook))
1406            (> (prefix-numeric-value arg) 0))))
1407     (if turn-it-on
1408         (progn
1409           ;; `help-mode-maybe' may add a `back' button and thus increase the
1410           ;; text size, so `resize-temp-buffer-window' must be run *after* it.
1411           (add-hook 'temp-buffer-show-hook 'resize-temp-buffer-window 'append)
1412           (setq temp-buffer-resize-mode t))
1413       (remove-hook 'temp-buffer-show-hook 'resize-temp-buffer-window)
1414       (setq temp-buffer-resize-mode nil))))
1415
1416 (defun resize-temp-buffer-window ()
1417   "Resize the current window to fit its contents.
1418 Will not make it higher than `temp-buffer-max-height' nor smaller than
1419 `window-min-height'.  Do nothing if it is the only window on its frame, if it
1420 is not as wide as the frame or if some of the window's contents are scrolled
1421 out of view."
1422   (unless (or (one-window-p 'nomini)
1423               (not (pos-visible-in-window-p (point-min)))
1424               (/=  (frame-width) (window-width)))
1425     (let* ((max-height (if (functionp temp-buffer-max-height)
1426                            (funcall temp-buffer-max-height (current-buffer))
1427                          temp-buffer-max-height))
1428            (win-height (1- (window-height)))
1429            (min-height (1- window-min-height))
1430            (text-height (count-screen-lines))
1431            (new-height (max (min text-height max-height) min-height)))
1432       (enlarge-window (- new-height win-height)))))
1433
1434 ;; `help-manyarg-func-alist' is defined primitively (in doc.c).
1435 ;; New primitives with `MANY' or `UNEVALLED' arglists should be added
1436 ;; to this alist.
1437 ;; The parens and function name are redundant, but it's messy to add
1438 ;; them in `documentation'.
1439 (defconst help-manyarg-func-alist
1440   (purecopy
1441    '((list . "(list &rest OBJECTS)")
1442      (vector . "(vector &rest OBJECTS)")
1443      (make-byte-code . "(make-byte-code &rest ELEMENTS)")
1444      (call-process
1445       . "(call-process PROGRAM &optional INFILE BUFFER DISPLAY &rest ARGS)")
1446      (call-process-region
1447       . "(call-process-region START END PROGRAM &optional DELETE BUFFER DISPLAY &rest ARGS)")
1448      (string . "(string &rest CHARACTERS)")
1449      (+ . "(+ &rest NUMBERS-OR-MARKERS)")
1450      (- . "(- &optional NUMBER-OR-MARKER &rest MORE-NUMBERS-OR-MARKERS)")
1451      (* . "(* &rest NUMBERS-OR-MARKERS)")
1452      (/ . "(/ DIVIDEND DIVISOR &rest DIVISORS)")
1453      (max . "(max NUMBER-OR-MARKER &rest NUMBERS-OR-MARKERS)")
1454      (min . "(min NUMBER-OR-MARKER &rest NUMBERS-OR-MARKERS)")
1455      (logand . "(logand &rest INTS-OR-MARKERS)")
1456      (logior . "(logior &rest INTS-OR-MARKERS)")
1457      (logxor . "(logxor &rest INTS-OR-MARKERS)")
1458      (encode-time
1459       . "(encode-time SECOND MINUTE HOUR DAY MONTH YEAR &optional ZONE)")
1460      (insert . "(insert &rest ARGS)")
1461      (insert-and-inherit . "(insert-and-inherit &rest ARGS)")
1462      (insert-before-markers . "(insert-before-markers &rest ARGS)")
1463      (message . "(message STRING &rest ARGUMENTS)")
1464      (message-box . "(message-box STRING &rest ARGUMENTS)")
1465      (message-or-box . "(message-or-box STRING &rest ARGUMENTS)")
1466      (propertize . "(propertize STRING &rest PROPERTIES)")
1467      (format . "(format STRING &rest OBJECTS)")
1468      (apply . "(apply FUNCTION &rest ARGUMENTS)")
1469      (run-hooks . "(run-hooks &rest HOOKS)")
1470      (run-hook-with-args . "(run-hook-with-args HOOK &rest ARGS)")
1471      (run-hook-with-args-until-failure
1472       . "(run-hook-with-args-until-failure HOOK &rest ARGS)")
1473      (run-hook-with-args-until-success
1474       . "(run-hook-with-args-until-success HOOK &rest ARGS)")
1475      (funcall . "(funcall FUNCTION &rest ARGUMENTS)")
1476      (append . "(append &rest SEQUENCES)")
1477      (concat . "(concat &rest SEQUENCES)")
1478      (vconcat . "(vconcat vconcat)")
1479      (nconc . "(nconc &rest LISTS)")
1480      (widget-apply . "(widget-apply WIDGET PROPERTY &rest ARGS)")
1481      (make-hash-table . "(make-hash-table &rest KEYWORD-ARGS)")
1482      (insert-string . "(insert-string &rest ARGS)")
1483      (start-process . "(start-process NAME BUFFER PROGRAM &rest PROGRAM-ARGS)")
1484      (setq-default . "(setq-default SYMBOL VALUE [SYMBOL VALUE...])")
1485      (save-excursion . "(save-excursion &rest BODY)")
1486      (save-current-buffer . "(save-current-buffer &rest BODY)")
1487      (save-restriction . "(save-restriction &rest BODY)")
1488      (or . "(or CONDITIONS ...)")
1489      (and . "(and CONDITIONS ...)")
1490      (if . "(if COND THEN ELSE...)")
1491      (cond . "(cond CLAUSES...)")
1492      (progn . "(progn BODY ...)")
1493      (prog1 . "(prog1 FIRST BODY...)")
1494      (prog2 . "(prog2 X Y BODY...)")
1495      (setq . "(setq SYM VAL SYM VAL ...)")
1496      (quote . "(quote ARG)")
1497      (function . "(function ARG)")
1498      (defun . "(defun NAME ARGLIST [DOCSTRING] BODY...)")
1499      (defmacro . "(defmacro NAME ARGLIST [DOCSTRING] BODY...)")
1500      (defvar . "(defvar SYMBOL [INITVALUE DOCSTRING])")
1501      (defconst . "(defconst SYMBOL INITVALUE [DOCSTRING])")
1502      (let* . "(let* VARLIST BODY...)")
1503      (let . "(let VARLIST BODY...)")
1504      (while . "(while TEST BODY...)")
1505      (catch . "(catch TAG BODY...)")
1506      (unwind-protect . "(unwind-protect BODYFORM UNWINDFORMS...)")
1507      (condition-case . "(condition-case VAR BODYFORM HANDLERS...)")
1508      (track-mouse . "(track-mouse BODY ...)")
1509      (ml-if . "(ml-if COND THEN ELSE...)")
1510      (ml-provide-prefix-argument . "(ml-provide-prefix-argument ARG1 ARG2)")
1511      (with-output-to-temp-buffer
1512          . "(with-output-to-temp-buffer BUFFNAME BODY ...)")
1513      (save-window-excursion . "(save-window-excursion BODY ...)"))))
1514
1515 ;;; help.el ends here