lisp/help.el

   1 ;;; help.el --- help commands for Emacs
   2
   3 ;; Copyright (C) 1985, 1986, 1993, 1994, 1998, 1999, 2000, 2001
   4 ;;   Free Software Foundation, Inc.
   5
   6 ;; Maintainer: FSF
   7 ;; Keywords: help, internal
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software; you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation; either version 2, or (at your option)
  14 ;; any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  23 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  24 ;; Boston, MA 02111-1307, USA.
  25
  26 ;;; Commentary:
  27
  28 ;; This code implements GNU Emacs' on-line help system, the one invoked by
  29 ;; `M-x help-for-help'.
  30
  31 ;;; Code:
  32
  33 ;; Get the macro make-help-screen when this is compiled,
  34 ;; or run interpreted, but not when the compiled code is loaded.
  35 (eval-when-compile (require 'help-macro))
  36 (eval-when-compile (require 'view))
  37
  38 (defvar help-map (make-sparse-keymap)
  39   "Keymap for characters following the Help key.")
  40
  41 (defvar help-mode-map (make-sparse-keymap)
  42   "Keymap for help mode.")
  43
  44 (define-key global-map (char-to-string help-char) 'help-command)
  45 (define-key global-map [help] 'help-command)
  46 (define-key global-map [f1] 'help-command)
  47 (fset 'help-command help-map)
  48
  49 (define-key help-map (char-to-string help-char) 'help-for-help)
  50 (define-key help-map [help] 'help-for-help)
  51 (define-key help-map [f1] 'help-for-help)
  52 (define-key help-map "?" 'help-for-help)
  53
  54 (define-key help-map "\C-c" 'describe-copying)
  55 (define-key help-map "\C-d" 'describe-distribution)
  56 (define-key help-map "\C-w" 'describe-no-warranty)
  57 (define-key help-map "\C-p" 'describe-project)
  58 (define-key help-map "a" 'apropos-command)
  59
  60 (define-key help-map "b" 'describe-bindings)
  61
  62 (define-key help-map "c" 'describe-key-briefly)
  63 (define-key help-map "k" 'describe-key)
  64
  65 (define-key help-map "d" 'describe-function)
  66 (define-key help-map "f" 'describe-function)
  67
  68 (define-key help-map "F" 'view-emacs-FAQ)
  69
  70 (define-key help-map "i" 'info)
  71 (define-key help-map "4i" 'info-other-window)
  72 (define-key help-map "\C-f" 'Info-goto-emacs-command-node)
  73 (define-key help-map "\C-k" 'Info-goto-emacs-key-command-node)
  74 (define-key help-map "\C-i" 'info-lookup-symbol)
  75
  76 (define-key help-map "l" 'view-lossage)
  77
  78 (define-key help-map "m" 'describe-mode)
  79 (define-key help-map "\C-m" 'view-order-manuals)
  80
  81 (define-key help-map "\C-n" 'view-emacs-news)
  82 (define-key help-map "n" 'view-emacs-news)
  83
  84 (define-key help-map "p" 'finder-by-keyword)
  85 (autoload 'finder-by-keyword "finder"
  86   "Find packages matching a given keyword." t)
  87
  88 (define-key help-map "P" 'view-emacs-problems)
  89
  90 (define-key help-map "s" 'describe-syntax)
  91
  92 (define-key help-map "t" 'help-with-tutorial)
  93
  94 (define-key help-map "w" 'where-is)
  95
  96 (define-key help-map "v" 'describe-variable)
  97
  98 (define-key help-map "q" 'help-quit)
  99
 100 (define-key help-mode-map [mouse-2] 'help-follow-mouse)
 101 (define-key help-mode-map "\C-c\C-b" 'help-go-back)
 102 (define-key help-mode-map "\C-c\C-c" 'help-follow)
 103 (define-key help-mode-map "\t" 'help-next-ref)
 104 (define-key help-mode-map [backtab] 'help-previous-ref)
 105 (define-key help-mode-map [(shift tab)] 'help-previous-ref)
 106 ;; Documentation only, since we use minor-mode-overriding-map-alist.
 107 (define-key help-mode-map "\r" 'help-follow)
 108
 109 (defvar help-xref-stack nil
 110   "A stack of ways by which to return to help buffers after following xrefs.
 111 Used by `help-follow' and `help-xref-go-back'.
 112 An element looks like (POSITION FUNCTION ARGS...), where POSITION is
 113 `(POINT . BUFFER-NAME)'.
 114 To use the element, do (apply FUNCTION ARGS) then goto the point in
 115 the named buffer.")
 116 (put 'help-xref-stack 'permanent-local t)
 117
 118 (defvar help-xref-stack-item nil
 119   "An item for `help-follow' in this buffer to push onto `help-xref-stack'.
 120 The format is (FUNCTION ARGS...).")
 121 (put 'help-xref-stack-item 'permanent-local t)
 122
 123 (setq-default help-xref-stack nil help-xref-stack-item nil)
 124
 125 (defcustom help-mode-hook nil
 126   "Hook run by `help-mode'."
 127   :type 'hook
 128   :group 'help)
 129
 130 (defun help-mode ()
 131   "Major mode for viewing help text and navigating references in it.
 132 Entry to this mode runs the normal hook `help-mode-hook'.
 133 Commands:
 134 \\{help-mode-map}"
 135   (interactive)
 136   (kill-all-local-variables)
 137   (use-local-map help-mode-map)
 138   (setq mode-name "Help")
 139   (setq major-mode 'help-mode)
 140   (make-local-variable 'font-lock-defaults)
 141   (setq font-lock-defaults nil)         ; font-lock would defeat xref
 142   (view-mode)
 143   (make-local-variable 'view-no-disable-on-exit)
 144   (setq view-no-disable-on-exit t)
 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 "THE-GNU-PROJECT" 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 "^ONEWS\\.[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-order-manuals ()
 454   "Display the Emacs ORDERS file."
 455   (interactive)
 456   (find-file-read-only (expand-file-name "ORDERS" data-directory))
 457   (goto-address))
 458
 459 (defun view-emacs-FAQ ()
 460   "Display the Emacs Frequently Asked Questions (FAQ) file."
 461   (interactive)
 462 ;;;  (find-file-read-only (expand-file-name "FAQ" data-directory))
 463   (info "(efaq)"))
 464
 465 (defun view-emacs-problems ()
 466   "Display info on known problems with Emacs and possible workarounds."
 467   (interactive)
 468   (view-file (expand-file-name "PROBLEMS" data-directory)))
 469
 470 (defun view-lossage ()
 471   "Display last 100 input keystrokes."
 472   (interactive)
 473   (with-output-to-temp-buffer "*Help*"
 474     (princ (mapconcat (function (lambda (key)
 475                                   (if (or (integerp key)
 476                                           (symbolp key)
 477                                           (listp key))
 478                                       (single-key-description key)
 479                                     (prin1-to-string key nil))))
 480                       (recent-keys)
 481                       " "))
 482     (save-excursion
 483       (set-buffer standard-output)
 484       (goto-char (point-min))
 485       (while (progn (move-to-column 50) (not (eobp)))
 486         (search-forward " " nil t)
 487         (insert "\n"))
 488       (setq help-xref-stack nil
 489             help-xref-stack-item nil))
 490     (print-help-return-message)))
 491
 492 (defalias 'help 'help-for-help)
 493 (make-help-screen help-for-help
 494   "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:"
 495   "You have typed %THIS-KEY%, the help character.  Type a Help option:
 496 \(Use SPC or DEL to scroll through this text.  Type \\<help-map>\\[help-quit] to exit the Help command.)
 497
 498 a  command-apropos.  Give a substring, and see a list of commands
 499         (functions interactively callable) that contain
 500         that substring.  See also the  apropos  command.
 501 b  describe-bindings.  Display table of all key bindings.
 502 c  describe-key-briefly.  Type a command key sequence;
 503         it prints the function name that sequence runs.
 504 C  describe-coding-system.  This describes either a specific coding system
 505         (if you type its name) or the coding systems currently in use
 506         (if you type just RET).
 507 f  describe-function.  Type a function name and get documentation of it.
 508 C-f Info-goto-emacs-command-node.  Type a function name;
 509         it takes you to the Info node for that command.
 510 i  info. The  info  documentation reader.
 511 I  describe-input-method.  Describe a specific input method (if you type
 512         its name) or the current input method (if you type just RET).
 513 C-i  info-lookup-symbol.  Display the definition of a specific symbol
 514         as found in the manual for the language this buffer is written in.
 515 k  describe-key.  Type a command key sequence;
 516         it displays the full documentation.
 517 C-k Info-goto-emacs-key-command-node.  Type a command key sequence;
 518         it takes you to the Info node for the command bound to that key.
 519 l  view-lossage.  Show last 100 characters you typed.
 520 L  describe-language-environment.  This describes either a
 521         specific language environment (if you type its name)
 522         or the current language environment (if you type just RET).
 523 m  describe-mode.  Print documentation of current minor modes,
 524         and the current major mode, including their special commands.
 525 n  view-emacs-news.  Display news of recent Emacs changes.
 526 p  finder-by-keyword. Find packages matching a given topic keyword.
 527 s  describe-syntax.  Display contents of syntax table, plus explanations
 528 t  help-with-tutorial.  Select the Emacs learn-by-doing tutorial.
 529 v  describe-variable.  Type name of a variable;
 530         it displays the variable's documentation and value.
 531 w  where-is.  Type command name; it prints which keystrokes
 532         invoke that command.
 533
 534 F  Display the frequently asked questions file.
 535 h  Display the HELLO file which illustrates various scripts.
 536 C-c Display Emacs copying permission (General Public License).
 537 C-d Display Emacs ordering information.
 538 C-n Display news of recent Emacs changes.
 539 C-p Display information about the GNU project.
 540 C-w Display information on absence of warranty for GNU Emacs."
 541   help-map)
 542
 543 (defun function-called-at-point ()
 544   "Return a function around point or else called by the list containing point.
 545 If that doesn't give a function, return nil."
 546   (with-syntax-table emacs-lisp-mode-syntax-table
 547     (or (condition-case ()
 548             (save-excursion
 549               (or (not (zerop (skip-syntax-backward "_w")))
 550                   (eq (char-syntax (following-char)) ?w)
 551                   (eq (char-syntax (following-char)) ?_)
 552                   (forward-sexp -1))
 553               (skip-chars-forward "'")
 554               (let ((obj (read (current-buffer))))
 555                 (and (symbolp obj) (fboundp obj) obj)))
 556           (error nil))
 557         (condition-case ()
 558             (save-excursion
 559               (save-restriction
 560                 (narrow-to-region (max (point-min)
 561                                        (- (point) 1000)) (point-max))
 562                 ;; Move up to surrounding paren, then after the open.
 563                 (backward-up-list 1)
 564                 (forward-char 1)
 565                 ;; If there is space here, this is probably something
 566                 ;; other than a real Lisp function call, so ignore it.
 567                 (if (looking-at "[ \t]")
 568                     (error "Probably not a Lisp function call"))
 569                 (let ((obj (read (current-buffer))))
 570                   (and (symbolp obj) (fboundp obj) obj))))
 571           (error nil)))))
 572
 573 (defvar symbol-file-load-history-loaded nil
 574   "Non-nil means we have loaded the file `fns-VERSION.el' in `exec-directory'.
 575 That file records the part of `load-history' for preloaded files,
 576 which is cleared out before dumping to make Emacs smaller.")
 577
 578 (defun load-symbol-file-load-history ()
 579   "Load the file `fns-VERSION.el' in `exec-directory' if not already done.
 580 That file records the part of `load-history' for preloaded files,
 581 which is cleared out before dumping to make Emacs smaller."
 582   (unless symbol-file-load-history-loaded
 583     (load (expand-file-name
 584            ;; fns-XX.YY.ZZ.el does not work on DOS filesystem.
 585            (if (eq system-type 'ms-dos)
 586                "fns.el"
 587              (format "fns-%s.el" emacs-version))
 588            exec-directory)
 589           ;; The file name fns-%s.el already has a .el extension.
 590           nil nil t)
 591     (setq symbol-file-load-history-loaded t)))
 592
 593 (defun symbol-file (function)
 594   "Return the input source from which FUNCTION was loaded.
 595 The value is normally a string that was passed to `load':
 596 either an absolute file name, or a library name
 597 \(with no directory name and no `.el' or `.elc' at the end).
 598 It can also be nil, if the definition is not associated with any file."
 599   (load-symbol-file-load-history)
 600   (let ((files load-history)
 601         file functions)
 602     (while files
 603       (if (memq function (cdr (car files)))
 604           (setq file (car (car files)) files nil))
 605       (setq files (cdr files)))
 606     file))
 607
 608 (defun describe-function (function)
 609   "Display the full documentation of FUNCTION (a symbol)."
 610   (interactive
 611    (let ((fn (function-called-at-point))
 612          (enable-recursive-minibuffers t)
 613          val)
 614      (setq val (completing-read (if fn
 615                                     (format "Describe function (default %s): " fn)
 616                                   "Describe function: ")
 617                                 obarray 'fboundp t nil nil (symbol-name fn)))
 618      (list (if (equal val "")
 619                fn (intern val)))))
 620   (if function
 621       (with-output-to-temp-buffer "*Help*"
 622         (prin1 function)
 623         ;; Use " is " instead of a colon so that
 624         ;; it is easier to get out the function name using forward-sexp.
 625         (princ " is ")
 626         (describe-function-1 function nil (interactive-p))
 627         (print-help-return-message)
 628         (save-excursion
 629           (set-buffer standard-output)
 630           ;; Return the text we displayed.
 631           (buffer-string)))
 632     (message "You didn't specify a function")))
 633
 634 (defun describe-function-1 (function parens interactive-p)
 635   (let* ((def (if (symbolp function)
 636                   (symbol-function function)
 637                 function))
 638          file-name string need-close
 639          (beg (if (commandp def) "an interactive " "a ")))
 640     (setq string
 641           (cond ((or (stringp def)
 642                      (vectorp def))
 643                  "a keyboard macro")
 644                 ((subrp def)
 645                  (if (eq 'unevalled (cdr (subr-arity def)))
 646                      (concat beg "special form")
 647                    (concat beg "built-in function")))
 648                 ((byte-code-function-p def)
 649                  (concat beg "compiled Lisp function"))
 650                 ((symbolp def)
 651                  (while (symbolp (symbol-function def))
 652                    (setq def (symbol-function def)))
 653                  (format "an alias for `%s'" def))
 654                 ((eq (car-safe def) 'lambda)
 655                  (concat beg "Lisp function"))
 656                 ((eq (car-safe def) 'macro)
 657                  "a Lisp macro")
 658                 ((eq (car-safe def) 'mocklisp)
 659                  "a mocklisp function")
 660                 ((eq (car-safe def) 'autoload)
 661                  (setq file-name (nth 1 def))
 662                  (format "%s autoloaded %s"
 663                          (if (commandp def) "an interactive" "an")
 664                          (if (eq (nth 4 def) 'keymap) "keymap"
 665                            (if (nth 4 def) "Lisp macro" "Lisp function"))
 666                          ))
 667                 ;; perhaps use keymapp here instead
 668                 ((eq (car-safe def) 'keymap)
 669                  (let ((is-full nil)
 670                        (elts (cdr-safe def)))
 671                    (while elts
 672                      (if (char-table-p (car-safe elts))
 673                          (setq is-full t
 674                                elts nil))
 675                      (setq elts (cdr-safe elts)))
 676                    (if is-full
 677                        "a full keymap"
 678                      "a sparse keymap")))
 679                 (t "")))
 680     (when (and parens (not (equal string "")))
 681       (setq need-close t)
 682       (princ "("))
 683     (princ string)
 684     (with-current-buffer "*Help*"
 685       (save-excursion
 686         (save-match-data
 687           (if (re-search-backward "alias for `\\([^`']+\\)'" nil t)
 688               (help-xref-button 1 #'describe-function def
 689                                 "mouse-2, RET: describe this function")))))
 690     (or file-name
 691         (setq file-name (symbol-file function)))
 692     (if file-name
 693         (progn
 694           (princ " in `")
 695           ;; We used to add .el to the file name,
 696           ;; but that's completely wrong when the user used load-file.
 697           (princ file-name)
 698           (princ "'")
 699           ;; Make a hyperlink to the library.
 700           (with-current-buffer "*Help*"
 701             (save-excursion
 702               (re-search-backward "`\\([^`']+\\)'" nil t)
 703               (help-xref-button 1 #'(lambda (arg)
 704                                       (let ((location
 705                                              (find-function-noselect arg)))
 706                                         (pop-to-buffer (car location))
 707                                         (goto-char (cdr location))))
 708                                 function
 709                                 "mouse-2, RET: find function's definition")))))
 710     (if need-close (princ ")"))
 711     (princ ".")
 712     (terpri)
 713     ;; Handle symbols aliased to other symbols.
 714     (setq def (indirect-function def))
 715     ;; If definition is a macro, find the function inside it.
 716     (if (eq (car-safe def) 'macro)
 717         (setq def (cdr def)))
 718     (let ((arglist (cond ((byte-code-function-p def)
 719                           (car (append def nil)))
 720                          ((eq (car-safe def) 'lambda)
 721                           (nth 1 def))
 722                          ((and (eq (car-safe def) 'autoload)
 723                                (not (eq (nth 4 def) 'keymap)))
 724                           (concat "[Arg list not available until "
 725                                   "function definition is loaded.]"))
 726                          (t t))))
 727       (cond ((listp arglist)
 728              (princ (cons (if (symbolp function) function "anonymous")
 729                           (mapcar (lambda (arg)
 730                                     (if (memq arg '(&optional &rest))
 731                                         arg
 732                                       (intern (upcase (symbol-name arg)))))
 733                                   arglist)))
 734              (terpri))
 735             ((stringp arglist)
 736              (princ arglist)
 737              (terpri))))
 738     (let ((doc (documentation function)))
 739       (if doc
 740           (progn (terpri)
 741                  (princ doc)
 742                  (if (subrp (symbol-function function))
 743                      (with-current-buffer standard-output
 744                        (beginning-of-line)
 745                        ;; Builtins get the calling sequence at the end of
 746                        ;; the doc string.  Move it to the same place as
 747                        ;; for other functions.
 748
 749                        ;; In cases where `function' has been fset to a
 750                        ;; subr we can't search for function's name in
 751                        ;; the doc string.  Kluge round that using the
 752                        ;; printed representation.  The arg list then
 753                        ;; shows the wrong function name, but that
 754                        ;; might be a useful hint.
 755                        (let* ((rep (prin1-to-string def))
 756                               (name (progn
 757                                       (string-match " \\([^ ]+\\)>$" rep)
 758                                       (match-string 1 rep))))
 759                          (if (looking-at (format "(%s[ )]" (regexp-quote name)))
 760                              (let ((start (point-marker)))
 761                                (goto-char (point-min))
 762                                (forward-paragraph)
 763                                (insert-buffer-substring (current-buffer) start)
 764                                (insert ?\n)
 765                                (delete-region (1- start) (point-max)))
 766                            (goto-char (point-min))
 767                            (forward-paragraph)
 768                            (insert
 769                             "[Missing arglist.  Please make a bug report.]\n")))
 770                        (goto-char (point-max))))
 771                  (help-setup-xref (list #'describe-function function)
 772                                   interactive-p))
 773         (princ "not documented")))))
 774
 775 (defun variable-at-point ()
 776   "Return the bound variable symbol found around point.
 777 Return 0 if there is no such symbol."
 778   (condition-case ()
 779       (with-syntax-table emacs-lisp-mode-syntax-table
 780         (save-excursion
 781           (or (not (zerop (skip-syntax-backward "_w")))
 782               (eq (char-syntax (following-char)) ?w)
 783               (eq (char-syntax (following-char)) ?_)
 784               (forward-sexp -1))
 785           (skip-chars-forward "'")
 786           (let ((obj (read (current-buffer))))
 787             (or (and (symbolp obj) (boundp obj) obj)
 788                 0))))
 789     (error 0)))
 790
 791 (defun help-xref-on-pp (from to)
 792   "Add xrefs for symbols in `pp's output between FROM and TO."
 793   (let ((ost (syntax-table)))
 794     (unwind-protect
 795         (save-excursion
 796           (save-restriction
 797             (set-syntax-table emacs-lisp-mode-syntax-table)
 798             (narrow-to-region from to)
 799             (goto-char (point-min))
 800             (while (not (eobp))
 801               (cond
 802                ((looking-at "\"") (forward-sexp 1))
 803                ((looking-at "#<") (search-forward ">" nil 'move))
 804                ((looking-at "\\(\\(\\sw\\|\\s_\\)+\\)")
 805                 (let* ((sym (intern-soft (match-string 1)))
 806                        (fn (cond ((fboundp sym) #'describe-function)
 807                                  ((or (memq sym '(t nil))
 808                                       (keywordp sym))
 809                                   nil)
 810                                  ((and sym (boundp sym))
 811                                   #'describe-variable))))
 812                   (when fn (help-xref-button 1 fn sym)))
 813                 (goto-char (match-end 1)))
 814                (t (forward-char 1))))))
 815       (set-syntax-table ost))))
 816
 817 (defun describe-variable (variable &optional buffer)
 818   "Display the full documentation of VARIABLE (a symbol).
 819 Returns the documentation as a string, also.
 820 If VARIABLE has a buffer-local value in BUFFER (default to the current buffer),
 821 it is displayed along with the global value."
 822   (interactive
 823    (let ((v (variable-at-point))
 824          (enable-recursive-minibuffers t)
 825          val)
 826      (setq val (completing-read (if (symbolp v)
 827                                     (format
 828                                      "Describe variable (default %s): " v)
 829                                   "Describe variable: ")
 830                                 obarray 'boundp t nil nil
 831                                 (if (symbolp v) (symbol-name v))))
 832      (list (if (equal val "")
 833                v (intern val)))))
 834   (unless (bufferp buffer) (setq buffer (current-buffer)))
 835   (if (not (symbolp variable))
 836       (message "You did not specify a variable")
 837     (let (valvoid)
 838       (with-current-buffer buffer
 839         (with-output-to-temp-buffer "*Help*"
 840           (prin1 variable)
 841           (if (not (boundp variable))
 842               (progn
 843                 (princ " is void")
 844                 (setq valvoid t))
 845             (let ((val (symbol-value variable)))
 846               (with-current-buffer standard-output
 847                 (princ "'s value is ")
 848                 (terpri)
 849                 (let ((from (point)))
 850                   (pp val)
 851                   (help-xref-on-pp from (point))))))
 852           (terpri)
 853           (if (local-variable-p variable)
 854               (progn
 855                 (princ (format "Local in buffer %s; " (buffer-name)))
 856                 (if (not (default-boundp variable))
 857                     (princ "globally void")
 858                   (let ((val (default-value variable)))
 859                     (with-current-buffer standard-output
 860                       (princ "global value is ")
 861                       (terpri)
 862                       ;; Fixme: pp can take an age if you happen to
 863                       ;; ask for a very large expression.  We should
 864                       ;; probably print it raw once and check it's a
 865                       ;; sensible size before prettyprinting.  -- fx
 866                       (let ((from (point)))
 867                         (pp val)
 868                         (help-xref-on-pp from (point))))))
 869                 (terpri)))
 870           (terpri)
 871           (with-current-buffer standard-output
 872             (if (> (count-lines (point-min) (point-max)) 10)
 873                 (progn
 874                   ;; Note that setting the syntax table like below
 875                   ;; makes forward-sexp move over a `'s' at the end
 876                   ;; of a symbol.
 877                   (set-syntax-table emacs-lisp-mode-syntax-table)
 878                   (goto-char (point-min))
 879                   (if valvoid
 880                       (forward-line 1)
 881                     (forward-sexp 1)
 882                     (delete-region (point) (progn (end-of-line) (point)))
 883                     (insert " value is shown below.\n\n")
 884                     (save-excursion
 885                       (insert "\n\nValue:"))))))
 886           (princ "Documentation:")
 887           (terpri)
 888           (let ((doc (documentation-property variable 'variable-documentation)))
 889             (princ (or doc "not documented as a variable.")))
 890           (help-setup-xref (list #'describe-variable variable (current-buffer))
 891                            (interactive-p))
 892
 893           ;; Make a link to customize if this variable can be customized.
 894           ;; Note, it is not reliable to test only for a custom-type property
 895           ;; because those are only present after the var's definition
 896           ;; has been loaded.
 897           (if (or (get variable 'custom-type) ; after defcustom
 898                   (get variable 'custom-loads) ; from loaddefs.el
 899                   (get variable 'standard-value)) ; from cus-start.el
 900               (let ((customize-label "customize"))
 901                 (terpri)
 902                 (terpri)
 903                 (princ (concat "You can " customize-label " this variable."))
 904                 (with-current-buffer "*Help*"
 905                   (save-excursion
 906                     (re-search-backward
 907                      (concat "\\(" customize-label "\\)") nil t)
 908                     (help-xref-button 1 (lambda (v)
 909                                           (if help-xref-stack
 910                                               (pop help-xref-stack))
 911                                           (customize-variable v))
 912                                       variable
 913                                       "mouse-2, RET: customize variable")))))
 914           ;; Make a hyperlink to the library if appropriate.  (Don't
 915           ;; change the format of the buffer's initial line in case
 916           ;; anything expects the current format.)
 917           (let ((file-name (symbol-file variable)))
 918             (when file-name
 919               (princ "\n\nDefined in `")
 920               (princ file-name)
 921               (princ "'.")
 922               (with-current-buffer "*Help*"
 923                 (save-excursion
 924                   (re-search-backward "`\\([^`']+\\)'" nil t)
 925                   (help-xref-button
 926                    1 (lambda (arg)
 927                        (let ((location
 928                               (find-variable-noselect arg)))
 929                          (pop-to-buffer (car location))
 930                          (goto-char (cdr location))))
 931                    variable "mouse-2, RET: find variable's definition")))))
 932
 933           (print-help-return-message)
 934           (save-excursion
 935             (set-buffer standard-output)
 936             ;; Return the text we displayed.
 937             (buffer-string)))))))
 938
 939 (defun describe-bindings (&optional prefix buffer)
 940   "Show a list of all defined keys, and their definitions.
 941 We put that list in a buffer, and display the buffer.
 942
 943 The optional argument PREFIX, if non-nil, should be a key sequence;
 944 then we display only bindings that start with that prefix.
 945 The optional argument BUFFER specifies which buffer's bindings
 946 to display (default, the current buffer)."
 947   (interactive "P")
 948   (or buffer (setq buffer (current-buffer)))
 949   (with-current-buffer buffer
 950     (describe-bindings-internal nil prefix))
 951   (with-current-buffer "*Help*"
 952     (help-setup-xref (list #'describe-bindings prefix buffer)
 953                      (interactive-p))))
 954
 955 (defun where-is (definition &optional insert)
 956   "Print message listing key sequences that invoke the command DEFINITION.
 957 Argument is a command definition, usually a symbol with a function definition.
 958 If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
 959   (interactive
 960    (let ((fn (function-called-at-point))
 961          (enable-recursive-minibuffers t)
 962          val)
 963      (setq val (completing-read (if fn
 964                                     (format "Where is command (default %s): " fn)
 965                                   "Where is command: ")
 966                                 obarray 'commandp t))
 967      (list (if (equal val "")
 968                fn (intern val))
 969            current-prefix-arg)))
 970   (let* ((keys (where-is-internal definition overriding-local-map nil nil))
 971          (keys1 (mapconcat 'key-description keys ", "))
 972          (standard-output (if insert (current-buffer) t)))
 973     (if insert
 974         (if (> (length keys1) 0)
 975             (princ (format "%s (%s)" keys1 definition))
 976           (princ (format "M-x %s RET" definition)))
 977       (if (> (length keys1) 0)
 978           (princ (format "%s is on %s" definition keys1))
 979         (princ (format "%s is not on any key" definition)))))
 980   nil)
 981
 982 (defun locate-library (library &optional nosuffix path interactive-call)
 983   "Show the precise file name of Emacs library LIBRARY.
 984 This command searches the directories in `load-path' like `M-x load-library'
 985 to find the file that `M-x load-library RET LIBRARY RET' would load.
 986 Optional second arg NOSUFFIX non-nil means don't add suffixes `.elc' or `.el'
 987 to the specified name LIBRARY.
 988
 989 If the optional third arg PATH is specified, that list of directories
 990 is used instead of `load-path'.
 991
 992 When called from a program, the file name is normaly returned as a
 993 string.  When run interactively, the argument INTERACTIVE-CALL is t,
 994 and the file name is displayed in the echo area."
 995   (interactive (list (read-string "Locate library: ")
 996                      nil nil
 997                      t))
 998   (let (result)
 999     (catch 'answer
1000       (mapc
1001        (lambda (dir)
1002          (mapc
1003           (lambda (suf)
1004             (let ((try (expand-file-name (concat library suf) dir)))
1005               (and (file-readable-p try)
1006                    (null (file-directory-p try))
1007                    (progn
1008                      (setq result try)
1009                      (throw 'answer try)))))
1010           (if nosuffix
1011               '("")
1012             '(".elc" ".el" "")
1013 ;;; load doesn't handle this yet.
1014 ;;;         (let ((basic '(".elc" ".el" ""))
1015 ;;;               (compressed '(".Z" ".gz" "")))
1016 ;;;           ;; If autocompression mode is on,
1017 ;;;           ;; consider all combinations of library suffixes
1018 ;;;           ;; and compression suffixes.
1019 ;;;           (if (rassq 'jka-compr-handler file-name-handler-alist)
1020 ;;;               (apply 'nconc
1021 ;;;                      (mapcar (lambda (compelt)
1022 ;;;                                (mapcar (lambda (baselt)
1023 ;;;                                          (concat baselt compelt))
1024 ;;;                                        basic))
1025 ;;;                              compressed))
1026 ;;;             basic))
1027             )))
1028        (or path load-path)))
1029     (and interactive-call
1030          (if result
1031              (message "Library is file %s" result)
1032            (message "No library %s in search path" library)))
1033     result))
1034
1035 \f
1036 ;;; Grokking cross-reference information in doc strings and
1037 ;;; hyperlinking it.
1038
1039 ;; This may have some scope for extension and the same or something
1040 ;; similar should be done for widget doc strings, which currently use
1041 ;; another mechanism.
1042
1043 (defcustom help-highlight-p t
1044   "*If non-nil, `help-make-xrefs' highlight cross-references.
1045 Under a window system it highlights them with face defined by
1046 `help-highlight-face'."
1047  :group 'help
1048  :version "20.3"
1049  :type 'boolean)
1050
1051 (defcustom help-highlight-face 'underline
1052   "Face used by `help-make-xrefs' to highlight cross-references.
1053 Must be previously-defined."
1054   :group 'help
1055   :version "20.3"
1056   :type 'face)
1057
1058 (defvar help-back-label (purecopy "[back]")
1059   "Label to use by `help-make-xrefs' for the go-back reference.")
1060
1061 (defconst help-xref-symbol-regexp
1062   (purecopy (concat "\\(\\<\\(\\(variable\\|option\\)\\|"
1063                     "\\(function\\|command\\)\\|"
1064                     "\\(face\\)\\|"
1065                     "\\(symbol\\)\\)\\s-+\\)?"
1066                     ;; Note starting with word-syntax character:
1067                     "`\\(\\sw\\(\\sw\\|\\s_\\)+\\)'"))
1068   "Regexp matching doc string references to symbols.
1069
1070 The words preceding the quoted symbol can be used in doc strings to
1071 distinguish references to variables, functions and symbols.")
1072
1073 (defconst help-xref-mule-regexp nil
1074   "Regexp matching doc string references to MULE-related keywords.
1075
1076 It is usually nil, and is temporarily bound to an appropriate regexp
1077 when help commands related to multilingual environment (e.g.,
1078 `describe-coding-system') are invoked.")
1079
1080
1081 (defconst help-xref-info-regexp
1082   (purecopy "\\<[Ii]nfo[ \t\n]+node[ \t\n]+`\\([^']+\\)'")
1083   "Regexp matching doc string references to an Info node.")
1084
1085 (defun help-setup-xref (item interactive-p)
1086   "Invoked from commands using the \"*Help*\" buffer to install some xref info.
1087
1088 ITEM is a (FUNCTION . ARGS) pair appropriate for recreating the help
1089 buffer after following a reference.  INTERACTIVE-P is non-nil if the
1090 calling command was invoked interactively.  In this case the stack of
1091 items for help buffer \"back\" buttons is cleared."
1092   (if interactive-p
1093       (setq help-xref-stack nil))
1094   (setq help-xref-stack-item item))
1095
1096 (defvar help-xref-following nil
1097   "Non-nil when following a help cross-reference.")
1098
1099 (defun help-make-xrefs (&optional buffer)
1100   "Parse and hyperlink documentation cross-references in the given BUFFER.
1101
1102 Find cross-reference information in a buffer and, if
1103 `help-highlight-p' is non-nil, highlight it with face defined by
1104 `help-highlight-face'; activate such cross references for selection
1105 with `help-follow'.  Cross-references have the canonical form `...'
1106 and the type of reference may be disambiguated by the preceding
1107 word(s) used in `help-xref-symbol-regexp'.
1108
1109 If the variable `help-xref-mule-regexp' is non-nil, find also
1110 cross-reference information related to multilingual environment
1111 \(e.g., coding-systems).  This variable is also used to disambiguate
1112 the type of reference as the same way as `help-xref-symbol-regexp'.
1113
1114 A special reference `back' is made to return back through a stack of
1115 help buffers.  Variable `help-back-label' specifies the text for
1116 that."
1117   (interactive "b")
1118   (save-excursion
1119     (set-buffer (or buffer (current-buffer)))
1120     (goto-char (point-min))
1121     ;; Skip the header-type info, though it might be useful to parse
1122     ;; it at some stage (e.g. "function in `library'").
1123     (forward-paragraph)
1124     (let ((old-modified (buffer-modified-p)))
1125       (let ((stab (syntax-table))
1126             (case-fold-search t)
1127             (inhibit-read-only t))
1128         (set-syntax-table emacs-lisp-mode-syntax-table)
1129         ;; The following should probably be abstracted out.
1130         (unwind-protect
1131             (progn
1132               ;; Info references
1133               (save-excursion
1134                 (while (re-search-forward help-xref-info-regexp nil t)
1135                   (let ((data (match-string 1)))
1136                     (save-match-data
1137                       (unless (string-match "^([^)]+)" data)
1138                         (setq data (concat "(emacs)" data))))
1139                     (help-xref-button 1 #'info data
1140                                       "mouse-2, RET: read this Info node"))))
1141               ;; Mule related keywords.  Do this before trying
1142               ;; `help-xref-symbol-regexp' because some of Mule
1143               ;; keywords have variable or function definitions.
1144               (if help-xref-mule-regexp
1145                   (save-excursion
1146                     (while (re-search-forward help-xref-mule-regexp nil t)
1147                       (let* ((data (match-string 7))
1148                              (sym (intern-soft data)))
1149                         (cond
1150                          ((match-string 3) ; coding system
1151                           (and sym (coding-system-p sym)
1152                                (help-xref-button
1153                                 7 #'describe-coding-system sym
1154                                 "mouse-2, RET: describe this coding system")))
1155                          ((match-string 4) ; input method
1156                           (and (assoc data input-method-alist)
1157                                (help-xref-button
1158                                 7 #'describe-input-method data
1159                                 "mouse-2, RET: describe this input method")))
1160                          ((or (match-string 5) (match-string 6)) ; charset
1161                           (and sym (charsetp sym)
1162                                (help-xref-button
1163                                 7 #'describe-character-set sym
1164                                 "mouse-2, RET: describe this character set")))
1165                          ((assoc data input-method-alist)
1166                           (help-xref-button
1167                            7 #'describe-input-method data
1168                            "mouse-2, RET: describe this input method"))
1169                          ((and sym (coding-system-p sym))
1170                           (help-xref-button
1171                            7 #'describe-coding-system sym
1172                            "mouse-2, RET: describe this coding system"))
1173                          ((and sym (charsetp sym))
1174                           (help-xref-button
1175                            7 #'describe-character-set sym
1176                            "mouse-2, RET: describe this character set")))))))
1177               ;; Quoted symbols
1178               (save-excursion
1179                 (while (re-search-forward help-xref-symbol-regexp nil t)
1180                   (let* ((data (match-string 7))
1181                          (sym (intern-soft data)))
1182                     (if sym
1183                         (cond
1184                          ((match-string 3) ; `variable' &c
1185                           (and (boundp sym) ; `variable' doesn't ensure
1186                                         ; it's actually bound
1187                                (help-xref-button
1188                                 7 #'describe-variable sym
1189                                 "mouse-2, RET: describe this variable")))
1190                          ((match-string 4) ; `function' &c
1191                           (and (fboundp sym) ; similarly
1192                                (help-xref-button
1193                                 7 #'describe-function sym
1194                                 "mouse-2, RET: describe this function")))
1195                          ((match-string 5) ; `face'
1196                           (and (facep sym)
1197                                (help-xref-button 7 #'describe-face sym
1198                                 "mouse-2, RET: describe this face")))
1199                          ((match-string 6)) ; nothing for symbol
1200                          ((and (boundp sym) (fboundp sym))
1201                           ;; We can't intuit whether to use the
1202                           ;; variable or function doc -- supply both.
1203                           (help-xref-button
1204                            7 #'help-xref-interned sym
1205                            "mouse-2, RET: describe this symbol"))
1206                          ((boundp sym)
1207                           (help-xref-button
1208                            7 #'describe-variable sym
1209                            "mouse-2, RET: describe this variable"))
1210                          ((fboundp sym)
1211                           (help-xref-button
1212                            7 #'describe-function sym
1213                            "mouse-2, RET: describe this function"))
1214                          ((facep sym)
1215                           (help-xref-button
1216                            7 #'describe-face sym)))))))
1217               ;; An obvious case of a key substitution:
1218               (save-excursion
1219                 (while (re-search-forward
1220                         ;; Assume command name is only word characters
1221                         ;; and dashes to get things like `use M-x foo.'.
1222                         "\\<M-x\\s-+\\(\\sw\\(\\sw\\|-\\)+\\)" nil t)
1223                   (let ((sym (intern-soft (match-string 1))))
1224                     (if (fboundp sym)
1225                         (help-xref-button
1226                          1 #'describe-function sym
1227                          "mouse-2, RET: describe this command")))))
1228               ;; Look for commands in whole keymap substitutions:
1229               (save-excursion
1230                 ;; Make sure to find the first keymap.
1231                 (goto-char (point-min))
1232                 ;; Find a header and the column at which the command
1233                 ;; name will be found.
1234                 (while (re-search-forward "^key +binding\n\\(-+ +\\)-+\n\n"
1235                                           nil t)
1236                   (let ((col (- (match-end 1) (match-beginning 1))))
1237                     (while
1238                         ;; Ignore single blank lines in table, but not
1239                         ;; double ones, which should terminate it.
1240                         (and (not (looking-at "\n\\s-*\n"))
1241                              (progn
1242                                (and (eolp) (forward-line))
1243                                (end-of-line)
1244                                (skip-chars-backward "^\t\n")
1245                                (if (and (>= (current-column) col)
1246                                         (looking-at "\\(\\sw\\|-\\)+$"))
1247                                    (let ((sym (intern-soft (match-string 0))))
1248                                      (if (fboundp sym)
1249                                          (help-xref-button
1250                                           0 #'describe-function sym
1251                                           "mouse-2, RET: describe this function"))))
1252                                (zerop (forward-line)))))))))
1253           (set-syntax-table stab))
1254         ;; Delete extraneous newlines at the end of the docstring
1255         (goto-char (point-max))
1256         (while (and (not (bobp)) (bolp))
1257           (delete-char -1))
1258         ;; Make a back-reference in this buffer if appropriate.
1259         (when (and help-xref-following help-xref-stack)
1260           (save-excursion
1261             (insert "\n\n" help-back-label))
1262           ;; Just to provide the match data:
1263           (looking-at (concat "\n\n\\(" (regexp-quote help-back-label) "\\)"))
1264           (help-xref-button 1 #'help-xref-go-back (current-buffer))))
1265       ;; View mode steals RET from us.
1266       (set (make-local-variable 'minor-mode-overriding-map-alist)
1267            (list (cons 'view-mode
1268                        (let ((map (make-sparse-keymap)))
1269                          (set-keymap-parent map view-mode-map)
1270                          (define-key map "\r" 'help-follow)
1271                          map))))
1272       (set-buffer-modified-p old-modified))))
1273
1274 (defun help-xref-button (match-number function data &optional help-echo)
1275   "Make a hyperlink for cross-reference text previously matched.
1276
1277 MATCH-NUMBER is the subexpression of interest in the last matched
1278 regexp.  FUNCTION is a function to invoke when the button is
1279 activated, applied to DATA.  DATA may be a single value or a list.
1280 See `help-make-xrefs'.
1281 If optional arg HELP-ECHO is supplied, it is used as a help string."
1282   ;; Don't mung properties we've added specially in some instances.
1283   (unless (get-text-property (match-beginning match-number) 'help-xref)
1284     (add-text-properties (match-beginning match-number)
1285                          (match-end match-number)
1286                          (list 'mouse-face 'highlight
1287                                'help-xref (cons function
1288                                                 (if (listp data)
1289                                                     data
1290                                                   (list data)))))
1291     (if help-echo
1292         (put-text-property (match-beginning match-number)
1293                            (match-end match-number)
1294                            'help-echo help-echo))
1295     (if help-highlight-p
1296         (put-text-property (match-beginning match-number)
1297                            (match-end match-number)
1298                            'face help-highlight-face))))
1299
1300 (defun help-insert-xref-button (string function data &optional help-echo)
1301   "Insert STRING and make a hyperlink from cross-reference text on it.
1302
1303 FUNCTION is a function to invoke when the button is activated, applied
1304 to DATA.  DATA may be a single value or a list.  See `help-make-xrefs'.
1305 If optional arg HELP-ECHO is supplied, it is used as a help string."
1306   (let ((pos (point)))
1307     (insert string)
1308     (goto-char pos)
1309     (search-forward string)
1310     (help-xref-button 0 function data help-echo)))
1311
1312
1313 \f
1314 ;; Additional functions for (re-)creating types of help buffers.
1315 (defun help-xref-interned (symbol)
1316   "Follow a hyperlink which appeared to be an arbitrary interned SYMBOL.
1317
1318 Both variable and function documentation are extracted into a single
1319 help buffer."
1320   (let ((fdoc (when (fboundp symbol) (describe-function symbol)))
1321         (facedoc (when (facep symbol) (describe-face symbol))))
1322     (when (or (boundp symbol) (not fdoc))
1323       (describe-variable symbol)
1324       ;; We now have a help buffer on the variable.  Insert the function
1325       ;; text before it.
1326       (when (or fdoc facedoc)
1327         (with-current-buffer "*Help*"
1328           (goto-char (point-min))
1329           (let ((inhibit-read-only t))
1330             (when fdoc
1331               (insert fdoc "\n\n"))
1332             (when facedoc
1333               (insert (make-string 30 ?-) "\n\n" (symbol-name symbol)
1334                       " is also a " "face." "\n\n" facedoc "\n\n"))
1335             (insert (make-string 30 ?-) "\n\n" (symbol-name symbol)
1336                     " is also a " "variable." "\n\n"))
1337           (help-setup-xref (list #'help-xref-interned symbol) nil))))))
1338
1339 (defun help-xref-mode (buffer)
1340   "Do a `describe-mode' for the specified BUFFER."
1341   (save-excursion
1342     (set-buffer buffer)
1343     (describe-mode)))
1344 \f
1345 ;;; Navigation/hyperlinking with xrefs
1346
1347 (defun help-follow-mouse (click)
1348   "Follow the cross-reference that you click on."
1349   (interactive "e")
1350   (let* ((start (event-start click))
1351          (window (car start))
1352          (pos (car (cdr start))))
1353     (with-current-buffer (window-buffer window)
1354       (help-follow pos))))
1355
1356 (defun help-xref-go-back (buffer)
1357   "From BUFFER, go back to previous help buffer text using `help-xref-stack'."
1358   (let (item position method args)
1359     (with-current-buffer buffer
1360       (when help-xref-stack
1361         (setq help-xref-stack (cdr help-xref-stack)) ; due to help-follow
1362         (setq item (pop help-xref-stack)
1363               position (car item)
1364               method (cadr item)
1365               args (cddr item))))
1366     (apply method args)
1367     ;; We assume that the buffer we just recreated has the saved name,
1368     ;; which might not always be true.
1369     (when (get-buffer (cdr position))
1370       (with-current-buffer (cdr position)
1371         (goto-char (car position))))))
1372
1373 (defun help-go-back ()
1374   "Invoke the [back] button (if any) in the Help mode buffer."
1375   (interactive)
1376   (help-follow (1- (point-max))))
1377
1378 (defun help-follow (&optional pos)
1379   "Follow cross-reference at POS, defaulting to point.
1380
1381 For the cross-reference format, see `help-make-xrefs'."
1382   (interactive "d")
1383   (unless pos
1384     (setq pos (point)))
1385   (let* ((help-data
1386           (or (and (not (= pos (point-max)))
1387                    (get-text-property pos 'help-xref))
1388               (and (not (= pos (point-min)))
1389                    (get-text-property (1- pos) 'help-xref))
1390               ;; check if the symbol under point is a function or variable
1391               (let ((sym
1392                      (intern
1393                       (save-excursion
1394                         (goto-char pos) (skip-syntax-backward "w_")
1395                         (buffer-substring (point)
1396                                           (progn (skip-syntax-forward "w_")
1397                                                  (point)))))))
1398                 (when (or (boundp sym) (fboundp sym))
1399                   (list #'help-xref-interned sym)))))
1400          (method (car help-data))
1401          (args (cdr help-data)))
1402     (when help-data
1403       (setq help-xref-stack (cons (cons (cons pos (buffer-name))
1404                                         help-xref-stack-item)
1405                                   help-xref-stack))
1406       (setq help-xref-stack-item nil)
1407       ;; There is a reference at point.  Follow it.
1408       (let ((help-xref-following t))
1409         (apply method args)))))
1410
1411 ;; For tabbing through buffer.
1412 (defun help-next-ref ()
1413   "Find the next help cross-reference in the buffer."
1414   (interactive)
1415   (let (pos)
1416     (while (not pos)
1417       (if (get-text-property (point) 'help-xref) ; move off reference
1418            (goto-char (or (next-single-property-change (point) 'help-xref)
1419                           (point))))
1420       (cond ((setq pos (next-single-property-change (point) 'help-xref))
1421              (if pos (goto-char pos)))
1422             ((bobp)
1423              (message "No cross references in the buffer.")
1424              (setq pos t))
1425             (t                          ; be circular
1426              (goto-char (point-min)))))))
1427
1428 (defun help-previous-ref ()
1429   "Find the previous help cross-reference in the buffer."
1430   (interactive)
1431   (let (pos)
1432     (while (not pos)
1433       (if (get-text-property (point) 'help-xref) ; move off reference
1434           (goto-char (or (previous-single-property-change (point) 'help-xref)
1435                          (point))))
1436       (cond ((setq pos (previous-single-property-change (point) 'help-xref))
1437              (if pos (goto-char pos)))
1438             ((bobp)
1439              (message "No cross references in the buffer.")
1440              (setq pos t))
1441             (t                          ; be circular
1442              (goto-char (point-max)))))))
1443
1444 \f
1445 ;;; Automatic resizing of temporary buffers.
1446
1447 (defcustom temp-buffer-max-height (lambda (buffer) (/ (- (frame-height) 2) 2))
1448   "*Maximum height of a window displaying a temporary buffer.
1449 This is the maximum height (in text lines) which `resize-temp-buffer-window'
1450 will give to a window displaying a temporary buffer.
1451 It can also be a function which will be called with the object corresponding
1452 to the buffer to be displayed as argument and should return an integer
1453 positive number."
1454   :type '(choice integer function)
1455   :group 'help
1456   :version "20.4")
1457
1458 (define-minor-mode temp-buffer-resize-mode
1459   "Toggle the mode which makes windows smaller for temporary buffers.
1460 With prefix argument ARG, turn the resizing of windows displaying temporary
1461 buffers on if ARG is positive or off otherwise.
1462 This makes the window the right height for its contents, but never
1463 more than `temp-buffer-max-height' nor less than `window-min-height'.
1464 This applies to `help', `apropos' and `completion' buffers, and some others."
1465   nil nil nil :global t :group 'help
1466   (if temp-buffer-resize-mode
1467       ;; `help-make-xrefs' may add a `back' button and thus increase the
1468       ;; text size, so `resize-temp-buffer-window' must be run *after* it.
1469       (add-hook 'temp-buffer-show-hook 'resize-temp-buffer-window 'append)
1470     (remove-hook 'temp-buffer-show-hook 'resize-temp-buffer-window)))
1471
1472 (defun resize-temp-buffer-window ()
1473   "Resize the current window to fit its contents.
1474 Will not make it higher than `temp-buffer-max-height' nor smaller than
1475 `window-min-height'.  Do nothing if it is the only window on its frame, if it
1476 is not as wide as the frame or if some of the window's contents are scrolled
1477 out of view."
1478   (unless (or (one-window-p 'nomini)
1479               (not (pos-visible-in-window-p (point-min)))
1480               (/=  (frame-width) (window-width)))
1481     (fit-window-to-buffer
1482      (selected-window)
1483      (if (functionp temp-buffer-max-height)
1484          (funcall temp-buffer-max-height (current-buffer))
1485        temp-buffer-max-height))))
1486
1487 ;; `help-manyarg-func-alist' is defined primitively (in doc.c).
1488 ;; New primitives with `MANY' or `UNEVALLED' arglists should be added
1489 ;; to this alist.
1490 ;; The parens and function name are redundant, but it's messy to add
1491 ;; them in `documentation'.
1492
1493 ;; This will find any missing items:
1494 ;; (let (l)
1495 ;;   (mapatoms (lambda (x)
1496 ;;            (if (and (fboundp x)
1497 ;;                     (subrp (symbol-function x))
1498 ;;                     (not (numberp (cdr (subr-arity (symbol-function x)))))
1499 ;;                     (not (assq x help-manyarg-func-alist)))
1500 ;;                (push x l))))
1501 ;;   l)
1502 (defconst help-manyarg-func-alist
1503   (purecopy
1504    '((list . "(list &rest OBJECTS)")
1505      (vector . "(vector &rest OBJECTS)")
1506      (make-byte-code . "(make-byte-code &rest ELEMENTS)")
1507      (call-process
1508       . "(call-process PROGRAM &optional INFILE BUFFER DISPLAY &rest ARGS)")
1509      (call-process-region
1510       . "(call-process-region START END PROGRAM &optional DELETE BUFFER DISPLAY &rest ARGS)")
1511      (string . "(string &rest CHARACTERS)")
1512      (+ . "(+ &rest NUMBERS-OR-MARKERS)")
1513      (- . "(- &optional NUMBER-OR-MARKER &rest MORE-NUMBERS-OR-MARKERS)")
1514      (* . "(* &rest NUMBERS-OR-MARKERS)")
1515      (/ . "(/ DIVIDEND DIVISOR &rest DIVISORS)")
1516      (max . "(max NUMBER-OR-MARKER &rest NUMBERS-OR-MARKERS)")
1517      (min . "(min NUMBER-OR-MARKER &rest NUMBERS-OR-MARKERS)")
1518      (logand . "(logand &rest INTS-OR-MARKERS)")
1519      (logior . "(logior &rest INTS-OR-MARKERS)")
1520      (logxor . "(logxor &rest INTS-OR-MARKERS)")
1521      (encode-time
1522       . "(encode-time SECOND MINUTE HOUR DAY MONTH YEAR &optional ZONE)")
1523      (insert . "(insert &rest ARGS)")
1524      (insert-and-inherit . "(insert-and-inherit &rest ARGS)")
1525      (insert-before-markers . "(insert-before-markers &rest ARGS)")
1526      (message . "(message STRING &rest ARGUMENTS)")
1527      (message-box . "(message-box STRING &rest ARGUMENTS)")
1528      (message-or-box . "(message-or-box STRING &rest ARGUMENTS)")
1529      (propertize . "(propertize STRING &rest PROPERTIES)")
1530      (format . "(format STRING &rest OBJECTS)")
1531      (apply . "(apply FUNCTION &rest ARGUMENTS)")
1532      (run-hooks . "(run-hooks &rest HOOKS)")
1533      (run-hook-with-args . "(run-hook-with-args HOOK &rest ARGS)")
1534      (run-hook-with-args-until-failure
1535       . "(run-hook-with-args-until-failure HOOK &rest ARGS)")
1536      (run-hook-with-args-until-success
1537       . "(run-hook-with-args-until-success HOOK &rest ARGS)")
1538      (funcall . "(funcall FUNCTION &rest ARGUMENTS)")
1539      (append . "(append &rest SEQUENCES)")
1540      (concat . "(concat &rest SEQUENCES)")
1541      (vconcat . "(vconcat &rest SEQUENCES)")
1542      (nconc . "(nconc &rest LISTS)")
1543      (widget-apply . "(widget-apply WIDGET PROPERTY &rest ARGS)")
1544      (make-hash-table . "(make-hash-table &rest KEYWORD-ARGS)")
1545      (insert-string . "(insert-string &rest ARGS)")
1546      (start-process . "(start-process NAME BUFFER PROGRAM &rest PROGRAM-ARGS)")
1547      (setq-default . "(setq-default SYMBOL VALUE [SYMBOL VALUE...])")
1548      (save-excursion . "(save-excursion &rest BODY)")
1549      (save-current-buffer . "(save-current-buffer &rest BODY)")
1550      (save-restriction . "(save-restriction &rest BODY)")
1551      (or . "(or CONDITIONS ...)")
1552      (and . "(and CONDITIONS ...)")
1553      (if . "(if COND THEN ELSE...)")
1554      (cond . "(cond CLAUSES...)")
1555      (progn . "(progn BODY ...)")
1556      (prog1 . "(prog1 FIRST BODY...)")
1557      (prog2 . "(prog2 X Y BODY...)")
1558      (setq . "(setq SYM VAL SYM VAL ...)")
1559      (quote . "(quote ARG)")
1560      (function . "(function ARG)")
1561      (defun . "(defun NAME ARGLIST [DOCSTRING] BODY...)")
1562      (defmacro . "(defmacro NAME ARGLIST [DOCSTRING] BODY...)")
1563      (defvar . "(defvar SYMBOL [INITVALUE DOCSTRING])")
1564      (defconst . "(defconst SYMBOL INITVALUE [DOCSTRING])")
1565      (let* . "(let* VARLIST BODY...)")
1566      (let . "(let VARLIST BODY...)")
1567      (while . "(while TEST BODY...)")
1568      (catch . "(catch TAG BODY...)")
1569      (unwind-protect . "(unwind-protect BODYFORM UNWINDFORMS...)")
1570      (condition-case . "(condition-case VAR BODYFORM HANDLERS...)")
1571      (track-mouse . "(track-mouse BODY ...)")
1572      (ml-if . "(ml-if COND THEN ELSE...)")
1573      (ml-provide-prefix-argument . "(ml-provide-prefix-argument ARG1 ARG2)")
1574      (ml-prefix-argument-loop . "(ml-prefix-argument-loop ...)")
1575      (with-output-to-temp-buffer
1576          . "(with-output-to-temp-buffer BUFFNAME BODY ...)")
1577      (save-window-excursion . "(save-window-excursion BODY ...)")
1578      (find-operation-coding-system
1579       . "(find-operation-coding-system OPERATION ARGUMENTS ...)")
1580      (insert-before-markers-and-inherit
1581       . "(insert-before-markers-and-inherit &rest ARGS)"))))
1582
1583 ;; Provide this for the sake of define-minor-mode which generates
1584 ;; defcustoms which require 'help'.
1585
1586 (provide 'help)
1587
1588 ;;; help.el ends here