lisp/help.el

   1 ;;; help.el --- help commands for Emacs
   2
   3 ;; Copyright (C) 1985, 1986, 1993, 1994, 1998, 1999, 2000, 2001, 2002,
   4 ;;   2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
   5 ;;   Free Software Foundation, Inc.
   6
   7 ;; Maintainer: FSF
   8 ;; Keywords: help, internal
   9 ;; Package: emacs
  10
  11 ;; This file is part of GNU Emacs.
  12
  13 ;; GNU Emacs is free software: you can redistribute it and/or modify
  14 ;; it under the terms of the GNU General Public License as published by
  15 ;; the Free Software Foundation, either version 3 of the License, or
  16 ;; (at your option) any later version.
  17
  18 ;; GNU Emacs is distributed in the hope that it will be useful,
  19 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21 ;; GNU General Public License for more details.
  22
  23 ;; You should have received a copy of the GNU General Public License
  24 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  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
  37 ;; This makes `with-output-to-temp-buffer' buffers use `help-mode'.
  38 (add-hook 'temp-buffer-setup-hook 'help-mode-setup)
  39 (add-hook 'temp-buffer-show-hook 'help-mode-finish)
  40
  41 ;; `help-window-point-marker' is a marker you can move to a valid
  42 ;; position of the buffer shown in the help window in order to override
  43 ;; the standard positioning mechanism (`point-min') chosen by
  44 ;; `with-output-to-temp-buffer'.  `with-help-window' has this point
  45 ;; nowhere before exiting.  Currently used by `view-lossage' to assert
  46 ;; that the last keystrokes are always visible.
  47 (defvar help-window-point-marker (make-marker)
  48   "Marker to override default `window-point' in help windows.")
  49
  50 (defvar help-map
  51   (let ((map (make-sparse-keymap)))
  52     (define-key map (char-to-string help-char) 'help-for-help)
  53     (define-key map [help] 'help-for-help)
  54     (define-key map [f1] 'help-for-help)
  55     (define-key map "." 'display-local-help)
  56     (define-key map "?" 'help-for-help)
  57
  58     (define-key map "\C-a" 'about-emacs)
  59     (define-key map "\C-c" 'describe-copying)
  60     (define-key map "\C-d" 'view-emacs-debugging)
  61     (define-key map "\C-e" 'view-external-packages)
  62     (define-key map "\C-f" 'view-emacs-FAQ)
  63     (define-key map "\C-m" 'view-order-manuals)
  64     (define-key map "\C-n" 'view-emacs-news)
  65     (define-key map "\C-o" 'describe-distribution)
  66     (define-key map "\C-p" 'view-emacs-problems)
  67     (define-key map "\C-t" 'view-emacs-todo)
  68     (define-key map "\C-w" 'describe-no-warranty)
  69
  70     ;; This does not fit the pattern, but it is natural given the C-\ command.
  71     (define-key map "\C-\\" 'describe-input-method)
  72
  73     (define-key map "C" 'describe-coding-system)
  74     (define-key map "F" 'Info-goto-emacs-command-node)
  75     (define-key map "I" 'describe-input-method)
  76     (define-key map "K" 'Info-goto-emacs-key-command-node)
  77     (define-key map "L" 'describe-language-environment)
  78     (define-key map "S" 'info-lookup-symbol)
  79
  80     (define-key map "a" 'apropos-command)
  81     (define-key map "b" 'describe-bindings)
  82     (define-key map "c" 'describe-key-briefly)
  83     (define-key map "d" 'apropos-documentation)
  84     (define-key map "e" 'view-echo-area-messages)
  85     (define-key map "f" 'describe-function)
  86     (define-key map "g" 'describe-gnu-project)
  87     (define-key map "h" 'view-hello-file)
  88
  89     (define-key map "i" 'info)
  90     (define-key map "4i" 'info-other-window)
  91
  92     (define-key map "k" 'describe-key)
  93     (define-key map "l" 'view-lossage)
  94     (define-key map "m" 'describe-mode)
  95     (define-key map "n" 'view-emacs-news)
  96     (define-key map "p" 'finder-by-keyword)
  97     (define-key map "P" 'describe-package)
  98     (define-key map "r" 'info-emacs-manual)
  99     (define-key map "s" 'describe-syntax)
 100     (define-key map "t" 'help-with-tutorial)
 101     (define-key map "w" 'where-is)
 102     (define-key map "v" 'describe-variable)
 103     (define-key map "q" 'help-quit)
 104     map)
 105   "Keymap for characters following the Help key.")
 106
 107 (define-key global-map (char-to-string help-char) 'help-command)
 108 (define-key global-map [help] 'help-command)
 109 (define-key global-map [f1] 'help-command)
 110 (fset 'help-command help-map)
 111
 112 ;; insert-button makes the action nil if it is not store somewhere
 113 (defvar help-button-cache nil)
 114
 115 \f
 116 (defun help-quit ()
 117   "Just exit from the Help command's command loop."
 118   (interactive)
 119   nil)
 120
 121 (defvar help-return-method nil
 122   "What to do to \"exit\" the help buffer.
 123 This is a list
 124  (WINDOW . t)              delete the selected window (and possibly its frame,
 125                            see `quit-window' and `View-quit'), go to WINDOW.
 126  (WINDOW . quit-window)    do quit-window, then select WINDOW.
 127  (WINDOW BUF START POINT)  display BUF at START, POINT, then select WINDOW.")
 128
 129 (define-obsolete-function-alias 'print-help-return-message 'help-print-return-message "23.2")
 130 (defun help-print-return-message (&optional function)
 131   "Display or return message saying how to restore windows after help command.
 132 This function assumes that `standard-output' is the help buffer.
 133 It computes a message, and applies the optional argument FUNCTION to it.
 134 If FUNCTION is nil, it applies `message', thus displaying the message.
 135 In addition, this function sets up `help-return-method', which see, that
 136 specifies what to do when the user exits the help buffer."
 137   (and (not (get-buffer-window standard-output))
 138        (let ((first-message
 139               (cond ((or
 140                       pop-up-frames
 141                       (special-display-p (buffer-name standard-output)))
 142                      (setq help-return-method (cons (selected-window) t))
 143                      ;; If the help output buffer is a special display buffer,
 144                      ;; don't say anything about how to get rid of it.
 145                      ;; First of all, the user will do that with the window
 146                      ;; manager, not with Emacs.
 147                      ;; Secondly, the buffer has not been displayed yet,
 148                      ;; so we don't know whether its frame will be selected.
 149                      nil)
 150                     (display-buffer-reuse-frames
 151                      (setq help-return-method (cons (selected-window)
 152                                                     'quit-window))
 153                      nil)
 154                     ((not (one-window-p t))
 155                      (setq help-return-method
 156                            (cons (selected-window) 'quit-window))
 157                      "Type \\[display-buffer] RET to restore the other window.")
 158                     (pop-up-windows
 159                      (setq help-return-method (cons (selected-window) t))
 160                      "Type \\[delete-other-windows] to remove help window.")
 161                     (t
 162                      (setq help-return-method
 163                            (list (selected-window) (window-buffer)
 164                                  (window-start) (window-point)))
 165                      "Type \\[switch-to-buffer] RET to remove help window."))))
 166          (funcall (or function 'message)
 167                   (concat
 168                    (if first-message
 169                        (substitute-command-keys first-message))
 170                    (if first-message "  ")
 171                    ;; If the help buffer will go in a separate frame,
 172                    ;; it's no use mentioning a command to scroll, so don't.
 173                    (if (or pop-up-windows
 174                            (special-display-p (buffer-name standard-output)))
 175                        nil
 176                      (if (same-window-p (buffer-name standard-output))
 177                          ;; Say how to scroll this window.
 178                          (substitute-command-keys
 179                           "\\[scroll-up] to scroll the help.")
 180                        ;; Say how to scroll some other window.
 181                        (substitute-command-keys
 182                         "\\[scroll-other-window] to scroll the help."))))))))
 183
 184 ;; So keyboard macro definitions are documented correctly
 185 (fset 'defining-kbd-macro (symbol-function 'start-kbd-macro))
 186
 187 (defalias 'help 'help-for-help-internal)
 188 ;; find-function can find this.
 189 (defalias 'help-for-help 'help-for-help-internal)
 190 ;; It can't find this, but nobody will look.
 191 (make-help-screen help-for-help-internal
 192   (purecopy "Type a help option: [abcCdefFgiIkKlLmnprstvw.] C-[cdefmnoptw] or ?")
 193   ;; Don't purecopy this one, because it's not evaluated (it's
 194   ;; directly used as a docstring in a function definition, so it'll
 195   ;; be moved to the DOC file anyway: no need for purecopying it).
 196   "You have typed %THIS-KEY%, the help character.  Type a Help option:
 197 \(Use SPC or DEL to scroll through this text.  Type \\<help-map>\\[help-quit] to exit the Help command.)
 198
 199 a PATTERN   Show commands whose name matches the PATTERN (a list of words
 200               or a regexp).  See also the `apropos' command.
 201 b           Display all key bindings.
 202 c KEYS      Display the command name run by the given key sequence.
 203 C CODING    Describe the given coding system, or RET for current ones.
 204 d PATTERN   Show a list of functions, variables, and other items whose
 205               documentation matches the PATTERN (a list of words or a regexp).
 206 e           Go to the *Messages* buffer which logs echo-area messages.
 207 f FUNCTION  Display documentation for the given function.
 208 F COMMAND   Show the on-line manual's section that describes the command.
 209 g           Display information about the GNU project.
 210 h           Display the HELLO file which illustrates various scripts.
 211 i           Start the Info documentation reader: read on-line manuals.
 212 I METHOD    Describe a specific input method, or RET for current.
 213 k KEYS      Display the full documentation for the key sequence.
 214 K KEYS      Show the on-line manual's section for the command bound to KEYS.
 215 l           Show last 300 input keystrokes (lossage).
 216 L LANG-ENV  Describes a specific language environment, or RET for current.
 217 m           Display documentation of current minor modes and current major mode,
 218               including their special commands.
 219 n           Display news of recent Emacs changes.
 220 p TOPIC     Find packages matching a given topic keyword.
 221 r           Display the Emacs manual in Info mode.
 222 s           Display contents of current syntax table, plus explanations.
 223 S SYMBOL    Show the section for the given symbol in the on-line manual
 224               for the programming language used in this buffer.
 225 t           Start the Emacs learn-by-doing tutorial.
 226 v VARIABLE  Display the given variable's documentation and value.
 227 w COMMAND   Display which keystrokes invoke the given command (where-is).
 228 .           Display any available local help at point in the echo area.
 229
 230 C-a         Information about Emacs.
 231 C-c         Emacs copying permission (GNU General Public License).
 232 C-d         Instructions for debugging GNU Emacs.
 233 C-e         External packages and information about Emacs.
 234 C-f         Emacs FAQ.
 235 C-m         How to order printed Emacs manuals.
 236 C-n         News of recent Emacs changes.
 237 C-o         Emacs ordering and distribution information.
 238 C-p         Info about known Emacs problems.
 239 C-t         Emacs TODO list.
 240 C-w         Information on absence of warranty for GNU Emacs."
 241   help-map)
 242
 243 \f
 244
 245 (defun function-called-at-point ()
 246   "Return a function around point or else called by the list containing point.
 247 If that doesn't give a function, return nil."
 248   (with-syntax-table emacs-lisp-mode-syntax-table
 249     (or (condition-case ()
 250             (save-excursion
 251               (or (not (zerop (skip-syntax-backward "_w")))
 252                   (eq (char-syntax (following-char)) ?w)
 253                   (eq (char-syntax (following-char)) ?_)
 254                   (forward-sexp -1))
 255               (skip-chars-forward "'")
 256               (let ((obj (read (current-buffer))))
 257                 (and (symbolp obj) (fboundp obj) obj)))
 258           (error nil))
 259         (condition-case ()
 260             (save-excursion
 261               (save-restriction
 262                 (narrow-to-region (max (point-min)
 263                                        (- (point) 1000)) (point-max))
 264                 ;; Move up to surrounding paren, then after the open.
 265                 (backward-up-list 1)
 266                 (forward-char 1)
 267                 ;; If there is space here, this is probably something
 268                 ;; other than a real Lisp function call, so ignore it.
 269                 (if (looking-at "[ \t]")
 270                     (error "Probably not a Lisp function call"))
 271                 (let ((obj (read (current-buffer))))
 272                   (and (symbolp obj) (fboundp obj) obj))))
 273           (error nil))
 274         (let* ((str (find-tag-default))
 275                (sym (if str (intern-soft str))))
 276           (if (and sym (fboundp sym))
 277               sym
 278             (save-match-data
 279               (when (and str (string-match "\\`\\W*\\(.*?\\)\\W*\\'" str))
 280                 (setq sym (intern-soft (match-string 1 str)))
 281                 (and (fboundp sym) sym))))))))
 282
 283 \f
 284 ;;; `User' help functions
 285
 286 (defun view-help-file (file &optional dir)
 287   (view-file (expand-file-name file (or dir data-directory)))
 288   (goto-address-mode 1)
 289   (goto-char (point-min)))
 290
 291 (defun describe-distribution ()
 292   "Display info on how to obtain the latest version of GNU Emacs."
 293   (interactive)
 294   (view-help-file "DISTRIB"))
 295
 296 (defun describe-copying ()
 297   "Display info on how you may redistribute copies of GNU Emacs."
 298   (interactive)
 299   (view-help-file "COPYING"))
 300
 301 (defun describe-gnu-project ()
 302   "Display info on the GNU project."
 303   (interactive)
 304   (view-help-file "THE-GNU-PROJECT"))
 305
 306 (define-obsolete-function-alias 'describe-project 'describe-gnu-project "22.2")
 307
 308 (defun describe-no-warranty ()
 309   "Display info on all the kinds of warranty Emacs does NOT have."
 310   (interactive)
 311   (describe-copying)
 312   (let (case-fold-search)
 313     (search-forward "Disclaimer of Warranty")
 314     (forward-line 0)
 315     (recenter 0)))
 316
 317 (defun describe-prefix-bindings ()
 318   "Describe the bindings of the prefix used to reach this command.
 319 The prefix described consists of all but the last event
 320 of the key sequence that ran this command."
 321   (interactive)
 322   (let ((key (this-command-keys)))
 323     (describe-bindings
 324      (if (stringp key)
 325          (substring key 0 (1- (length key)))
 326        (let ((prefix (make-vector (1- (length key)) nil))
 327              (i 0))
 328          (while (< i (length prefix))
 329            (aset prefix i (aref key i))
 330            (setq i (1+ i)))
 331          prefix)))))
 332 ;; Make C-h after a prefix, when not specifically bound,
 333 ;; run describe-prefix-bindings.
 334 (setq prefix-help-command 'describe-prefix-bindings)
 335
 336 (defun view-emacs-news (&optional version)
 337   "Display info on recent changes to Emacs.
 338 With argument, display info only for the selected version."
 339   (interactive "P")
 340   (unless version
 341     (setq version emacs-major-version))
 342   (when (consp version)
 343     (let* ((all-versions
 344             (let (res)
 345               (mapc
 346                (lambda (file)
 347                  (with-temp-buffer
 348                    (insert-file-contents
 349                     (expand-file-name file data-directory))
 350                    (while (re-search-forward
 351                            (if (member file '("NEWS.18" "NEWS.1-17"))
 352                                "Changes in \\(?:Emacs\\|version\\)?[ \t]*\\([0-9]+\\(?:\\.[0-9]+\\)?\\)"
 353                              "^\* [^0-9\n]*\\([0-9]+\\.[0-9]+\\)") nil t)
 354                      (setq res (cons (match-string-no-properties 1) res)))))
 355                (cons "NEWS"
 356                      (directory-files data-directory nil
 357                                       "^NEWS\\.[0-9][-0-9]*$" nil)))
 358               (sort (delete-dups res) (lambda (a b) (string< b a)))))
 359            (current (car all-versions)))
 360       (setq version (completing-read
 361                      (format "Read NEWS for the version (default %s): " current)
 362                      all-versions nil nil nil nil current))
 363       (if (integerp (string-to-number version))
 364           (setq version (string-to-number version))
 365         (unless (or (member version all-versions)
 366                     (<= (string-to-number version) (string-to-number current)))
 367           (error "No news about version %s" version)))))
 368   (when (integerp version)
 369     (cond ((<= version 12)
 370            (setq version (format "1.%d" version)))
 371           ((<= version 18)
 372            (setq version (format "%d" version)))
 373           ((> version emacs-major-version)
 374            (error "No news about Emacs %d (yet)" version))))
 375   (let* ((vn (if (stringp version)
 376                  (string-to-number version)
 377                version))
 378          (file (cond
 379                 ((>= vn emacs-major-version) "NEWS")
 380                 ((< vn 18) "NEWS.1-17")
 381                 (t (format "NEWS.%d" vn))))
 382          res)
 383     (view-file (expand-file-name file data-directory))
 384     (widen)
 385     (goto-char (point-min))
 386     (when (stringp version)
 387       (when (re-search-forward
 388              (concat (if (< vn 19)
 389                          "Changes in Emacs[ \t]*"
 390                        "^\* [^0-9\n]*") version "$")
 391              nil t)
 392         (beginning-of-line)
 393         (narrow-to-region
 394          (point)
 395          (save-excursion
 396            (while (and (setq res
 397                              (re-search-forward
 398                               (if (< vn 19)
 399                                   "Changes in \\(?:Emacs\\|version\\)?[ \t]*\\([0-9]+\\(?:\\.[0-9]+\\)?\\)"
 400                                 "^\* [^0-9\n]*\\([0-9]+\\.[0-9]+\\)") nil t))
 401                        (equal (match-string-no-properties 1) version)))
 402            (or res (goto-char (point-max)))
 403            (beginning-of-line)
 404            (point)))))))
 405
 406 (defun view-emacs-todo (&optional arg)
 407   "Display the Emacs TODO list."
 408   (interactive "P")
 409   (view-help-file "TODO"))
 410
 411 (define-obsolete-function-alias 'view-todo 'view-emacs-todo "22.2")
 412
 413
 414 (defun view-echo-area-messages ()
 415   "View the log of recent echo-area messages: the `*Messages*' buffer.
 416 The number of messages retained in that buffer
 417 is specified by the variable `message-log-max'."
 418   (interactive)
 419   (switch-to-buffer (get-buffer-create "*Messages*")))
 420
 421 (defun view-order-manuals ()
 422   "Display the Emacs ORDERS file."
 423   (interactive)
 424   (view-help-file "ORDERS"))
 425
 426 (defun view-emacs-FAQ ()
 427   "Display the Emacs Frequently Asked Questions (FAQ) file."
 428   (interactive)
 429   ;; (find-file-read-only (expand-file-name "FAQ" data-directory))
 430   (info "(efaq)"))
 431
 432 (defun view-emacs-problems ()
 433   "Display info on known problems with Emacs and possible workarounds."
 434   (interactive)
 435   (view-help-file "PROBLEMS"))
 436
 437 (defun view-emacs-debugging ()
 438   "Display info on how to debug Emacs problems."
 439   (interactive)
 440   (view-help-file "DEBUG"))
 441
 442 (defun view-external-packages ()
 443   "Display external packages and information about Emacs."
 444   (interactive)
 445   (view-help-file "MORE.STUFF"))
 446
 447 (defun view-lossage ()
 448   "Display last 300 input keystrokes.
 449
 450 To record all your input on a file, use `open-dribble-file'."
 451   (interactive)
 452   (help-setup-xref (list #'view-lossage)
 453                    (called-interactively-p 'interactive))
 454   (with-help-window (help-buffer)
 455     (princ (mapconcat (lambda (key)
 456                         (if (or (integerp key) (symbolp key) (listp key))
 457                             (single-key-description key)
 458                           (prin1-to-string key nil)))
 459                       (recent-keys)
 460                       " "))
 461     (with-current-buffer standard-output
 462       (goto-char (point-min))
 463       (while (progn (move-to-column 50) (not (eobp)))
 464         (when (search-forward " " nil t)
 465           (delete-char -1))
 466         (insert "\n"))
 467       ;; jidanni wants to see the last keystrokes immediately.
 468       (set-marker help-window-point-marker (point)))))
 469
 470 \f
 471 ;; Key bindings
 472
 473 (defun describe-bindings (&optional prefix buffer)
 474   "Show a list of all defined keys, and their definitions.
 475 We put that list in a buffer, and display the buffer.
 476
 477 The optional argument PREFIX, if non-nil, should be a key sequence;
 478 then we display only bindings that start with that prefix.
 479 The optional argument BUFFER specifies which buffer's bindings
 480 to display (default, the current buffer).  BUFFER can be a buffer
 481 or a buffer name."
 482   (interactive)
 483   (or buffer (setq buffer (current-buffer)))
 484   (help-setup-xref (list #'describe-bindings prefix buffer)
 485                    (called-interactively-p 'interactive))
 486   (with-current-buffer buffer
 487     (describe-bindings-internal nil prefix)))
 488
 489 ;; This function used to be in keymap.c.
 490 (defun describe-bindings-internal (&optional menus prefix)
 491   "Show a list of all defined keys, and their definitions.
 492 We put that list in a buffer, and display the buffer.
 493
 494 The optional argument MENUS, if non-nil, says to mention menu bindings.
 495 \(Ordinarily these are omitted from the output.)
 496 The optional argument PREFIX, if non-nil, should be a key sequence;
 497 then we display only bindings that start with that prefix."
 498   (let ((buf (current-buffer)))
 499     (with-help-window "*Help*"
 500       (with-current-buffer standard-output
 501         (describe-buffer-bindings buf prefix menus)))))
 502
 503 (defun where-is (definition &optional insert)
 504   "Print message listing key sequences that invoke the command DEFINITION.
 505 Argument is a command definition, usually a symbol with a function definition.
 506 If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
 507   (interactive
 508    (let ((fn (function-called-at-point))
 509          (enable-recursive-minibuffers t)
 510          val)
 511      (setq val (completing-read
 512                 (if fn
 513                     (format "Where is command (default %s): " fn)
 514                   "Where is command: ")
 515                 obarray 'commandp t))
 516      (list (if (equal val "") fn (intern val)) current-prefix-arg)))
 517   (unless definition (error "No command"))
 518   (let ((func (indirect-function definition))
 519         (defs nil)
 520         (standard-output (if insert (current-buffer) t)))
 521     ;; In DEFS, find all symbols that are aliases for DEFINITION.
 522     (mapatoms (lambda (symbol)
 523                 (and (fboundp symbol)
 524                      (not (eq symbol definition))
 525                      (eq func (condition-case ()
 526                                   (indirect-function symbol)
 527                                 (error symbol)))
 528                      (push symbol defs))))
 529     ;; Look at all the symbols--first DEFINITION,
 530     ;; then its aliases.
 531     (dolist (symbol (cons definition defs))
 532       (let* ((remapped (command-remapping symbol))
 533              (keys (where-is-internal
 534                     symbol overriding-local-map nil nil remapped))
 535              (keys (mapconcat 'key-description keys ", "))
 536              string)
 537         (setq string
 538               (if insert
 539                   (if (> (length keys) 0)
 540                       (if remapped
 541                           (format "%s (%s) (remapped from %s)"
 542                                   keys remapped symbol)
 543                         (format "%s (%s)" keys symbol))
 544                     (format "M-x %s RET" symbol))
 545                 (if (> (length keys) 0)
 546                     (if remapped
 547                         (format "%s is remapped to %s which is on %s"
 548                                 symbol remapped keys)
 549                       (format "%s is on %s" symbol keys))
 550                   ;; If this is the command the user asked about,
 551                   ;; and it is not on any key, say so.
 552                   ;; For other symbols, its aliases, say nothing
 553                   ;; about them unless they are on keys.
 554                   (if (eq symbol definition)
 555                       (format "%s is not on any key" symbol)))))
 556         (when string
 557           (unless (eq symbol definition)
 558             (princ ";\n its alias "))
 559           (princ string)))))
 560   nil)
 561
 562 (defun help-key-description (key untranslated)
 563   (let ((string (key-description key)))
 564     (if (or (not untranslated)
 565             (and (eq (aref untranslated 0) ?\e) (not (eq (aref key 0) ?\e))))
 566         string
 567       (let ((otherstring (key-description untranslated)))
 568         (if (equal string otherstring)
 569             string
 570           (format "%s (translated from %s)" string otherstring))))))
 571
 572 (defun describe-key-briefly (&optional key insert untranslated)
 573   "Print the name of the function KEY invokes.  KEY is a string.
 574 If INSERT (the prefix arg) is non-nil, insert the message in the buffer.
 575 If non-nil, UNTRANSLATED is a vector of the untranslated events.
 576 It can also be a number in which case the untranslated events from
 577 the last key hit are used.
 578
 579 If KEY is a menu item or a tool-bar button that is disabled, this command
 580 temporarily enables it to allow getting help on disabled items and buttons."
 581   (interactive
 582    (let ((enable-disabled-menus-and-buttons t)
 583          (cursor-in-echo-area t)
 584          saved-yank-menu)
 585      (unwind-protect
 586          (let (key)
 587            ;; If yank-menu is empty, populate it temporarily, so that
 588            ;; "Select and Paste" menu can generate a complete event.
 589            (when (null (cdr yank-menu))
 590              (setq saved-yank-menu (copy-sequence yank-menu))
 591              (menu-bar-update-yank-menu "(any string)" nil))
 592            (setq key (read-key-sequence "Describe key (or click or menu item): "))
 593            ;; If KEY is a down-event, read and discard the
 594            ;; corresponding up-event.  Note that there are also
 595            ;; down-events on scroll bars and mode lines: the actual
 596            ;; event then is in the second element of the vector.
 597            (and (vectorp key)
 598                 (let ((last-idx (1- (length key))))
 599                   (and (eventp (aref key last-idx))
 600                        (memq 'down (event-modifiers (aref key last-idx)))))
 601                 (read-event))
 602            (list
 603             key
 604             (if current-prefix-arg (prefix-numeric-value current-prefix-arg))
 605             1))
 606        ;; Put yank-menu back as it was, if we changed it.
 607        (when saved-yank-menu
 608          (setq yank-menu (copy-sequence saved-yank-menu))
 609          (fset 'yank-menu (cons 'keymap yank-menu))))))
 610   (if (numberp untranslated)
 611       (setq untranslated (this-single-command-raw-keys)))
 612   (let* ((event (if (and (symbolp (aref key 0))
 613                          (> (length key) 1)
 614                          (consp (aref key 1)))
 615                     (aref key 1)
 616                   (aref key 0)))
 617          (modifiers (event-modifiers event))
 618          (standard-output (if insert (current-buffer) t))
 619          (mouse-msg (if (or (memq 'click modifiers) (memq 'down modifiers)
 620                             (memq 'drag modifiers)) " at that spot" ""))
 621          (defn (key-binding key t))
 622          key-desc)
 623     ;; Handle the case where we faked an entry in "Select and Paste" menu.
 624     (if (and (eq defn nil)
 625              (stringp (aref key (1- (length key))))
 626              (eq (key-binding (substring key 0 -1)) 'yank-menu))
 627         (setq defn 'menu-bar-select-yank))
 628     ;; Don't bother user with strings from (e.g.) the select-paste menu.
 629     (if (stringp (aref key (1- (length key))))
 630         (aset key (1- (length key)) "(any string)"))
 631     (if (and (> (length untranslated) 0)
 632              (stringp (aref untranslated (1- (length untranslated)))))
 633         (aset untranslated (1- (length untranslated)) "(any string)"))
 634     ;; Now describe the key, perhaps as changed.
 635     (setq key-desc (help-key-description key untranslated))
 636     (if (or (null defn) (integerp defn) (equal defn 'undefined))
 637         (princ (format "%s%s is undefined" key-desc mouse-msg))
 638       (princ (format "%s%s runs the command %S" key-desc mouse-msg defn)))))
 639
 640 (defun describe-key (&optional key untranslated up-event)
 641   "Display documentation of the function invoked by KEY.
 642 KEY can be any kind of a key sequence; it can include keyboard events,
 643 mouse events, and/or menu events.  When calling from a program,
 644 pass KEY as a string or a vector.
 645
 646 If non-nil, UNTRANSLATED is a vector of the corresponding untranslated events.
 647 It can also be a number, in which case the untranslated events from
 648 the last key sequence entered are used.
 649 UP-EVENT is the up-event that was discarded by reading KEY, or nil.
 650
 651 If KEY is a menu item or a tool-bar button that is disabled, this command
 652 temporarily enables it to allow getting help on disabled items and buttons."
 653   (interactive
 654    (let ((enable-disabled-menus-and-buttons t)
 655          (cursor-in-echo-area t)
 656          saved-yank-menu)
 657      (unwind-protect
 658          (let (key)
 659            ;; If yank-menu is empty, populate it temporarily, so that
 660            ;; "Select and Paste" menu can generate a complete event.
 661            (when (null (cdr yank-menu))
 662              (setq saved-yank-menu (copy-sequence yank-menu))
 663              (menu-bar-update-yank-menu "(any string)" nil))
 664            (setq key (read-key-sequence "Describe key (or click or menu item): "))
 665            (list
 666             key
 667             (prefix-numeric-value current-prefix-arg)
 668             ;; If KEY is a down-event, read and include the
 669             ;; corresponding up-event.  Note that there are also
 670             ;; down-events on scroll bars and mode lines: the actual
 671             ;; event then is in the second element of the vector.
 672             (and (vectorp key)
 673                  (let ((last-idx (1- (length key))))
 674                    (and (eventp (aref key last-idx))
 675                         (memq 'down (event-modifiers (aref key last-idx)))))
 676                  (or (and (eventp (aref key 0))
 677                           (memq 'down (event-modifiers (aref key 0)))
 678                           ;; However, for the C-down-mouse-2 popup
 679                           ;; menu, there is no subsequent up-event.  In
 680                           ;; this case, the up-event is the next
 681                           ;; element in the supplied vector.
 682                           (= (length key) 1))
 683                      (and (> (length key) 1)
 684                           (eventp (aref key 1))
 685                           (memq 'down (event-modifiers (aref key 1)))))
 686                  (read-event))))
 687        ;; Put yank-menu back as it was, if we changed it.
 688        (when saved-yank-menu
 689          (setq yank-menu (copy-sequence saved-yank-menu))
 690          (fset 'yank-menu (cons 'keymap yank-menu))))))
 691   (if (numberp untranslated)
 692       (setq untranslated (this-single-command-raw-keys)))
 693   (let* ((event (aref key (if (and (symbolp (aref key 0))
 694                                    (> (length key) 1)
 695                                    (consp (aref key 1)))
 696                               1
 697                             0)))
 698          (modifiers (event-modifiers event))
 699          (mouse-msg (if (or (memq 'click modifiers) (memq 'down modifiers)
 700                             (memq 'drag modifiers)) " at that spot" ""))
 701          (defn (key-binding key t))
 702          defn-up defn-up-tricky ev-type
 703          mouse-1-remapped mouse-1-tricky)
 704
 705     ;; Handle the case where we faked an entry in "Select and Paste" menu.
 706     (when (and (eq defn nil)
 707                (stringp (aref key (1- (length key))))
 708                (eq (key-binding (substring key 0 -1)) 'yank-menu))
 709       (setq defn 'menu-bar-select-yank))
 710     (if (or (null defn) (integerp defn) (equal defn 'undefined))
 711         (message "%s%s is undefined"
 712                  (help-key-description key untranslated) mouse-msg)
 713       (help-setup-xref (list #'describe-function defn)
 714                        (called-interactively-p 'interactive))
 715       ;; Don't bother user with strings from (e.g.) the select-paste menu.
 716       (when (stringp (aref key (1- (length key))))
 717         (aset key (1- (length key)) "(any string)"))
 718       (when (and untranslated
 719                  (stringp (aref untranslated (1- (length untranslated)))))
 720         (aset untranslated (1- (length untranslated))
 721               "(any string)"))
 722       ;; Need to do this before erasing *Help* buffer in case event
 723       ;; is a mouse click in an existing *Help* buffer.
 724       (when up-event
 725         (setq ev-type (event-basic-type up-event))
 726         (let ((sequence (vector up-event)))
 727           (when (and (eq ev-type 'mouse-1)
 728                      mouse-1-click-follows-link
 729                      (not (eq mouse-1-click-follows-link 'double))
 730                      (setq mouse-1-remapped
 731                            (mouse-on-link-p (event-start up-event))))
 732             (setq mouse-1-tricky (and (integerp mouse-1-click-follows-link)
 733                                       (> mouse-1-click-follows-link 0)))
 734             (cond ((stringp mouse-1-remapped)
 735                    (setq sequence mouse-1-remapped))
 736                   ((vectorp mouse-1-remapped)
 737                    (setcar up-event (elt mouse-1-remapped 0)))
 738                   (t (setcar up-event 'mouse-2))))
 739           (setq defn-up (key-binding sequence nil nil (event-start up-event)))
 740           (when mouse-1-tricky
 741             (setq sequence (vector up-event))
 742             (aset sequence 0 'mouse-1)
 743             (setq defn-up-tricky (key-binding sequence nil nil (event-start up-event))))))
 744       (with-help-window (help-buffer)
 745         (princ (help-key-description key untranslated))
 746         (princ (format "\
 747 %s runs the command %S, which is "
 748                        mouse-msg defn))
 749         (describe-function-1 defn)
 750         (when up-event
 751           (unless (or (null defn-up)
 752                       (integerp defn-up)
 753                       (equal defn-up 'undefined))
 754             (princ (format "
 755
 756 ----------------- up-event %s----------------
 757
 758 %s%s%s runs the command %S, which is "
 759                            (if mouse-1-tricky "(short click) " "")
 760                            (key-description (vector up-event))
 761                            mouse-msg
 762                            (if mouse-1-remapped
 763                                " is remapped to <mouse-2>, which" "")
 764                            defn-up))
 765             (describe-function-1 defn-up))
 766           (unless (or (null defn-up-tricky)
 767                       (integerp defn-up-tricky)
 768                       (eq defn-up-tricky 'undefined))
 769             (princ (format "
 770
 771 ----------------- up-event (long click) ----------------
 772
 773 Pressing <%S>%s for longer than %d milli-seconds
 774 runs the command %S, which is "
 775                            ev-type mouse-msg
 776                            mouse-1-click-follows-link
 777                            defn-up-tricky))
 778             (describe-function-1 defn-up-tricky)))))))
 779 \f
 780 (defun describe-mode (&optional buffer)
 781   "Display documentation of current major mode and minor modes.
 782 A brief summary of the minor modes comes first, followed by the
 783 major mode description.  This is followed by detailed
 784 descriptions of the minor modes, each on a separate page.
 785
 786 For this to work correctly for a minor mode, the mode's indicator
 787 variable \(listed in `minor-mode-alist') must also be a function
 788 whose documentation describes the minor mode."
 789   (interactive "@")
 790   (unless buffer (setq buffer (current-buffer)))
 791   (help-setup-xref (list #'describe-mode buffer)
 792                    (called-interactively-p 'interactive))
 793   ;; For the sake of help-do-xref and help-xref-go-back,
 794   ;; don't switch buffers before calling `help-buffer'.
 795   (with-help-window (help-buffer)
 796     (with-current-buffer buffer
 797       (let (minor-modes)
 798         ;; Older packages do not register in minor-mode-list but only in
 799         ;; minor-mode-alist.
 800         (dolist (x minor-mode-alist)
 801           (setq x (car x))
 802           (unless (memq x minor-mode-list)
 803             (push x minor-mode-list)))
 804         ;; Find enabled minor mode we will want to mention.
 805         (dolist (mode minor-mode-list)
 806           ;; Document a minor mode if it is listed in minor-mode-alist,
 807           ;; non-nil, and has a function definition.
 808           (let ((fmode (or (get mode :minor-mode-function) mode)))
 809             (and (boundp mode) (symbol-value mode)
 810                  (fboundp fmode)
 811                  (let ((pretty-minor-mode
 812                         (if (string-match "\\(\\(-minor\\)?-mode\\)?\\'"
 813                                           (symbol-name fmode))
 814                             (capitalize
 815                              (substring (symbol-name fmode)
 816                                         0 (match-beginning 0)))
 817                           fmode)))
 818                    (push (list fmode pretty-minor-mode
 819                                (format-mode-line (assq mode minor-mode-alist)))
 820                          minor-modes)))))
 821         (setq minor-modes
 822               (sort minor-modes
 823                     (lambda (a b) (string-lessp (cadr a) (cadr b)))))
 824         (when minor-modes
 825           (princ "Enabled minor modes:\n")
 826           (make-local-variable 'help-button-cache)
 827           (with-current-buffer standard-output
 828             (dolist (mode minor-modes)
 829               (let ((mode-function (nth 0 mode))
 830                     (pretty-minor-mode (nth 1 mode))
 831                     (indicator (nth 2 mode)))
 832                 (add-text-properties 0 (length pretty-minor-mode)
 833                                      '(face bold) pretty-minor-mode)
 834                 (save-excursion
 835                   (goto-char (point-max))
 836                   (princ "\n\f\n")
 837                   (push (point-marker) help-button-cache)
 838                   ;; Document the minor modes fully.
 839                   (insert pretty-minor-mode)
 840                   (princ (format " minor mode (%s):\n"
 841                                  (if (zerop (length indicator))
 842                                      "no indicator"
 843                                    (format "indicator%s"
 844                                            indicator))))
 845                   (princ (documentation mode-function)))
 846                 (insert-button pretty-minor-mode
 847                                'action (car help-button-cache)
 848                                'follow-link t
 849                                'help-echo "mouse-2, RET: show full information")
 850                 (newline)))
 851             (forward-line -1)
 852             (fill-paragraph nil)
 853             (forward-line 1))
 854
 855           (princ "\n(Information about these minor modes follows the major mode info.)\n\n"))
 856         ;; Document the major mode.
 857         (let ((mode mode-name))
 858           (with-current-buffer standard-output
 859             (let ((start (point)))
 860               (insert (format-mode-line mode nil nil buffer))
 861               (add-text-properties start (point) '(face bold)))))
 862         (princ " mode:\n")
 863         (princ (documentation major-mode)))))
 864   ;; For the sake of IELM and maybe others
 865   nil)
 866
 867
 868 (defun describe-minor-mode (minor-mode)
 869   "Display documentation of a minor mode given as MINOR-MODE.
 870 MINOR-MODE can be a minor mode symbol or a minor mode indicator string
 871 appeared on the mode-line."
 872   (interactive (list (completing-read
 873                       "Minor mode: "
 874                               (nconc
 875                                (describe-minor-mode-completion-table-for-symbol)
 876                                (describe-minor-mode-completion-table-for-indicator)
 877                                ))))
 878   (if (symbolp minor-mode)
 879       (setq minor-mode (symbol-name minor-mode)))
 880   (let ((symbols (describe-minor-mode-completion-table-for-symbol))
 881         (indicators (describe-minor-mode-completion-table-for-indicator)))
 882     (cond
 883      ((member minor-mode symbols)
 884       (describe-minor-mode-from-symbol (intern minor-mode)))
 885      ((member minor-mode indicators)
 886       (describe-minor-mode-from-indicator minor-mode))
 887      (t
 888       (error "No such minor mode: %s" minor-mode)))))
 889
 890 ;; symbol
 891 (defun describe-minor-mode-completion-table-for-symbol ()
 892   ;; In order to list up all minor modes, minor-mode-list
 893   ;; is used here instead of minor-mode-alist.
 894   (delq nil (mapcar 'symbol-name minor-mode-list)))
 895
 896 (defun describe-minor-mode-from-symbol (symbol)
 897   "Display documentation of a minor mode given as a symbol, SYMBOL"
 898   (interactive (list (intern (completing-read
 899                               "Minor mode symbol: "
 900                               (describe-minor-mode-completion-table-for-symbol)))))
 901   (if (fboundp symbol)
 902       (describe-function symbol)
 903     (describe-variable symbol)))
 904
 905 ;; indicator
 906 (defun describe-minor-mode-completion-table-for-indicator ()
 907   (delq nil
 908         (mapcar (lambda (x)
 909                   (let ((i (format-mode-line x)))
 910                     ;; remove first space if existed
 911                     (cond
 912                      ((= 0 (length i))
 913                       nil)
 914                      ((eq (aref i 0) ?\s)
 915                       (substring i 1))
 916                      (t
 917                       i))))
 918                 minor-mode-alist)))
 919
 920 (defun describe-minor-mode-from-indicator (indicator)
 921   "Display documentation of a minor mode specified by INDICATOR.
 922 If you call this function interactively, you can give indicator which
 923 is currently activated with completion."
 924   (interactive (list
 925                 (completing-read
 926                  "Minor mode indicator: "
 927                  (describe-minor-mode-completion-table-for-indicator))))
 928   (let ((minor-mode (lookup-minor-mode-from-indicator indicator)))
 929     (if minor-mode
 930         (describe-minor-mode-from-symbol minor-mode)
 931       (error "Cannot find minor mode for `%s'" indicator))))
 932
 933 (defun lookup-minor-mode-from-indicator (indicator)
 934   "Return a minor mode symbol from its indicator on the modeline."
 935   ;; remove first space if existed
 936   (if (and (< 0 (length indicator))
 937            (eq (aref indicator 0) ?\s))
 938       (setq indicator (substring indicator 1)))
 939   (let ((minor-modes minor-mode-alist)
 940         result)
 941     (while minor-modes
 942       (let* ((minor-mode (car (car minor-modes)))
 943              (anindicator (format-mode-line
 944                            (car (cdr (car minor-modes))))))
 945         ;; remove first space if existed
 946         (if (and (stringp anindicator)
 947                  (> (length anindicator) 0)
 948                  (eq (aref anindicator 0) ?\s))
 949             (setq anindicator (substring anindicator 1)))
 950         (if (equal indicator anindicator)
 951             (setq result minor-mode
 952                   minor-modes nil)
 953           (setq minor-modes (cdr minor-modes)))))
 954     result))
 955 \f
 956 ;;; Automatic resizing of temporary buffers.
 957 (defcustom temp-buffer-max-height (lambda (buffer) (/ (- (frame-height) 2) 2))
 958   "Maximum height of a window displaying a temporary buffer.
 959 This is effective only when Temp Buffer Resize mode is enabled.
 960 The value is the maximum height (in lines) which
 961 `resize-temp-buffer-window' will give to a window displaying a
 962 temporary buffer.  It can also be a function to be called to
 963 choose the height for such a buffer.  It gets one argumemt, the
 964 buffer, and should return a positive integer.  At the time the
 965 function is called, the window to be resized is selected."
 966   :type '(choice integer function)
 967   :group 'help
 968   :version "20.4")
 969
 970 (define-minor-mode temp-buffer-resize-mode
 971   "Toggle mode which makes windows smaller for temporary buffers.
 972 With prefix argument ARG, turn the resizing of windows displaying
 973 temporary buffers on if ARG is positive or off otherwise.
 974
 975 This mode makes a window the right height for its contents, but
 976 never more than `temp-buffer-max-height' nor less than
 977 `window-min-height'.
 978
 979 This mode is used by `help', `apropos' and `completion' buffers,
 980 and some others."
 981   :global t :group 'help
 982   (if temp-buffer-resize-mode
 983       ;; `help-make-xrefs' may add a `back' button and thus increase the
 984       ;; text size, so `resize-temp-buffer-window' must be run *after* it.
 985       (add-hook 'temp-buffer-show-hook 'resize-temp-buffer-window 'append)
 986     (remove-hook 'temp-buffer-show-hook 'resize-temp-buffer-window)))
 987
 988 (defun resize-temp-buffer-window ()
 989   "Resize the selected window to fit its contents.
 990 Will not make it higher than `temp-buffer-max-height' nor smaller
 991 than `window-min-height'.  Do nothing if the selected window is
 992 not vertically combined or some of its contents are scrolled out
 993 of view."
 994   (when (and (pos-visible-in-window-p (point-min))
 995              (window-iso-combined-p))
 996     (fit-window-to-buffer
 997      nil
 998      (if (functionp temp-buffer-max-height)
 999          (funcall temp-buffer-max-height (window-buffer))
1000        temp-buffer-max-height))))
1001
1002 ;;; Help windows.
1003 (defcustom help-window-select 'other
1004     "Non-nil means select help window for viewing.
1005 Choices are:
1006  never (nil) Select help window only if there is no other window
1007              on its frame.
1008  other       Select help window unless the selected window is the
1009              only other window on the help window's frame.
1010  always (t)  Always select the help window.
1011
1012 This option has effect if and only if the help window was created
1013 by `with-help-window'"
1014   :type '(choice (const :tag "never (nil)" nil)
1015                  (const :tag "other" other)
1016                  (const :tag "always (t)" t))
1017   :group 'help
1018   :version "23.1")
1019
1020 (defun help-window-display-message (quit-part window &optional scroll)
1021   "Display message telling how to quit and scroll help window.
1022 QUIT-PART is a string telling how to quit the help window WINDOW.
1023 Optional argument SCROLL non-nil means tell how to scroll WINDOW.
1024 SCROLL equal `other' means tell how to scroll the \"other\"
1025 window."
1026   (let ((scroll-part
1027          (cond
1028           ((pos-visible-in-window-p
1029             (with-current-buffer (window-buffer window)
1030               (point-max)) window)
1031            ;; Buffer end is visible.
1032            ".")
1033           ((eq scroll 'other)
1034            ", \\[scroll-other-window] to scroll help.")
1035           (scroll ", \\[scroll-up] to scroll help."))))
1036     (message "%s"
1037      (substitute-command-keys (concat quit-part scroll-part)))))
1038
1039 (defun help-window-setup ()
1040   "Set up help window for `with-help-window'.
1041 This relies on `display-buffer-window' being correctly set up by
1042 `display-buffer'."
1043   (let* ((help-window (car-safe display-buffer-window))
1044          (help-buffer (when (window-live-p help-window)
1045                         (window-buffer help-window)))
1046          (help-value (cdr-safe display-buffer-window)))
1047     (when help-buffer
1048       ;; Handle `help-window-point-marker'.
1049       (when (eq (marker-buffer help-window-point-marker) help-buffer)
1050         (set-window-point help-window help-window-point-marker)
1051         ;; Reset `help-window-point-marker'.
1052         (set-marker help-window-point-marker nil))
1053
1054       (cond
1055        ((or (eq help-window (selected-window))
1056             (and (or (eq help-window-select t)
1057                      (and (eq help-window-select 'other)
1058                           (eq (window-frame help-window) (selected-frame))
1059                           (= (length (window-list nil 'no-mini)) 2)))
1060                  (select-window help-window)))
1061         ;; The help window is or gets selected ...
1062         (help-window-display-message
1063          (cond
1064           ((eq help-value 'new-window)
1065            ;; ... and is new, ...
1066            "Type \"q\" to delete this window")
1067           ((eq help-value 'new-frame)
1068            ;; ... is on a new frame ...
1069            "Type \"q\" to delete this frame")
1070           ((eq help-value 'reuse-other-window)
1071            ;; ... or displayed some other buffer before.
1072            "Type \"q\" to restore previous buffer"))
1073          help-window t))
1074        ((and (eq (window-frame help-window) (selected-frame))
1075              (= (length (window-list nil 'no-mini)) 2))
1076         ;; There are two windows on the help window's frame and the
1077         ;; other one is the selected one.
1078         (help-window-display-message
1079          (cond
1080           ((eq help-value 'new-window)
1081            "Type \\[delete-other-windows] to delete the help window")
1082           ((eq help-value 'reuse-other-window)
1083            "Type \\[switch-to-prev-buffer] RET to restore previous buffer"))
1084          help-window 'other))
1085        (t
1086         ;; Not much to say here.
1087         (help-window-display-message
1088          "Type \"q\" in help window to quit" help-window))))))
1089
1090 ;; `with-help-window' is a wrapper for `with-output-to-temp-buffer'
1091 ;; providing the following additional twists:
1092
1093 ;; (1) Issue more accurate messages telling how to scroll and quit the
1094 ;; help window.
1095
1096 ;; (2) An option (customizable via `help-window-select') to select the
1097 ;; help window automatically.
1098
1099 ;; (3) A marker (`help-window-point-marker') to move point in the help
1100 ;; window to an arbitrary buffer position.
1101
1102 ;; Note: It's usually always wrong to use `help-print-return-message' in
1103 ;; the body of `with-help-window'.
1104 (defmacro with-help-window (buffer-name &rest body)
1105   "Display buffer with name BUFFER-NAME in a help window evaluating BODY.
1106 Select help window if the actual value of the user option
1107 `help-window-select' says so.  Return last value in BODY."
1108   (declare (indent 1) (debug t))
1109   `(progn
1110      ;; Reset `display-buffer-window': `display-buffer' is
1111      ;; supposed to set this to the window displaying the buffer plus
1112      ;; some additional information.
1113      (setq display-buffer-window nil)
1114      ;; Make `help-window-point-marker' point nowhere.  The only place
1115      ;; where this should be set to a buffer position is within BODY.
1116      (set-marker help-window-point-marker nil)
1117      (prog1
1118          ;; Return value returned by `with-output-to-temp-buffer'.
1119          (with-output-to-temp-buffer ,buffer-name
1120            (progn ,@body))
1121        (when display-buffer-window (help-window-setup)))))
1122 \f
1123 (provide 'help)
1124
1125 ;;; help.el ends here