lisp/help.el

   1 ;;; help.el --- help commands for Emacs
   2
   3 ;; Copyright (C) 1985-1986, 1993-1994, 1998-2012 Free Software Foundation, Inc.
   4
   5 ;; Maintainer: FSF
   6 ;; Keywords: help, internal
   7 ;; Package: emacs
   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 3 of the License, or
  14 ;; (at your option) 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.  If not, see <http://www.gnu.org/licenses/>.
  23
  24 ;;; Commentary:
  25
  26 ;; This code implements GNU Emacs's on-line help system, the one invoked by
  27 ;; `M-x help-for-help'.
  28
  29 ;;; Code:
  30
  31 ;; Get the macro make-help-screen when this is compiled,
  32 ;; or run interpreted, but not when the compiled code is loaded.
  33 (eval-when-compile (require 'help-macro))
  34
  35 ;; This makes `with-output-to-temp-buffer' buffers use `help-mode'.
  36 (add-hook 'temp-buffer-setup-hook 'help-mode-setup)
  37 (add-hook 'temp-buffer-show-hook 'help-mode-finish)
  38
  39 ;; `help-window-point-marker' is a marker you can move to a valid
  40 ;; position of the buffer shown in the help window in order to override
  41 ;; the standard positioning mechanism (`point-min') chosen by
  42 ;; `with-output-to-temp-buffer' and `with-temp-buffer-window'.
  43 ;; `with-help-window' has this point nowhere before exiting.  Currently
  44 ;; used by `view-lossage' to assert that the last keystrokes are always
  45 ;; visible.
  46 (defvar help-window-point-marker (make-marker)
  47   "Marker to override default `window-point' in help windows.")
  48
  49 (defvar help-map
  50   (let ((map (make-sparse-keymap)))
  51     (define-key map (char-to-string help-char) 'help-for-help)
  52     (define-key map [help] 'help-for-help)
  53     (define-key map [f1] 'help-for-help)
  54     (define-key map "." 'display-local-help)
  55     (define-key map "?" 'help-for-help)
  56
  57     (define-key map "\C-a" 'about-emacs)
  58     (define-key map "\C-c" 'describe-copying)
  59     (define-key map "\C-d" 'view-emacs-debugging)
  60     (define-key map "\C-e" 'view-external-packages)
  61     (define-key map "\C-f" 'view-emacs-FAQ)
  62     (define-key map "\C-m" 'view-order-manuals)
  63     (define-key map "\C-n" 'view-emacs-news)
  64     (define-key map "\C-o" 'describe-distribution)
  65     (define-key map "\C-p" 'view-emacs-problems)
  66     (define-key map "\C-t" 'view-emacs-todo)
  67     (define-key map "\C-w" 'describe-no-warranty)
  68
  69     ;; This does not fit the pattern, but it is natural given the C-\ command.
  70     (define-key map "\C-\\" 'describe-input-method)
  71
  72     (define-key map "C" 'describe-coding-system)
  73     (define-key map "F" 'Info-goto-emacs-command-node)
  74     (define-key map "I" 'describe-input-method)
  75     (define-key map "K" 'Info-goto-emacs-key-command-node)
  76     (define-key map "L" 'describe-language-environment)
  77     (define-key map "S" 'info-lookup-symbol)
  78
  79     (define-key map "a" 'apropos-command)
  80     (define-key map "b" 'describe-bindings)
  81     (define-key map "c" 'describe-key-briefly)
  82     (define-key map "d" 'apropos-documentation)
  83     (define-key map "e" 'view-echo-area-messages)
  84     (define-key map "f" 'describe-function)
  85     (define-key map "g" 'describe-gnu-project)
  86     (define-key map "h" 'view-hello-file)
  87
  88     (define-key map "i" 'info)
  89     (define-key map "4i" 'info-other-window)
  90
  91     (define-key map "k" 'describe-key)
  92     (define-key map "l" 'view-lossage)
  93     (define-key map "m" 'describe-mode)
  94     (define-key map "n" 'view-emacs-news)
  95     (define-key map "p" 'finder-by-keyword)
  96     (define-key map "P" 'describe-package)
  97     (define-key map "r" 'info-emacs-manual)
  98     (define-key map "s" 'describe-syntax)
  99     (define-key map "t" 'help-with-tutorial)
 100     (define-key map "w" 'where-is)
 101     (define-key map "v" 'describe-variable)
 102     (define-key map "q" 'help-quit)
 103     map)
 104   "Keymap for characters following the Help key.")
 105
 106 (define-key global-map (char-to-string help-char) 'help-command)
 107 (define-key global-map [help] 'help-command)
 108 (define-key global-map [f1] 'help-command)
 109 (fset 'help-command help-map)
 110
 111 ;; insert-button makes the action nil if it is not store somewhere
 112 (defvar help-button-cache nil)
 113
 114 \f
 115 (defun help-quit ()
 116   "Just exit from the Help command's command loop."
 117   (interactive)
 118   nil)
 119
 120 (defvar help-return-method nil
 121   "What to do to \"exit\" the help buffer.
 122 This is a list
 123  (WINDOW . t)              delete the selected window (and possibly its frame,
 124                            see `quit-window'), go to WINDOW.
 125  (WINDOW . quit-window)    do quit-window, then select WINDOW.
 126  (WINDOW BUF START POINT)  display BUF at START, POINT, then select WINDOW.")
 127
 128 (define-obsolete-function-alias 'print-help-return-message 'help-print-return-message "23.2")
 129 (defun help-print-return-message (&optional function)
 130   "Display or return message saying how to restore windows after help command.
 131 This function assumes that `standard-output' is the help buffer.
 132 It computes a message, and applies the optional argument FUNCTION to it.
 133 If FUNCTION is nil, it applies `message', thus displaying the message.
 134 In addition, this function sets up `help-return-method', which see, that
 135 specifies what to do when the user exits the help buffer."
 136   (and (not (get-buffer-window standard-output))
 137        (let ((first-message
 138               (cond ((or
 139                       pop-up-frames
 140                       (special-display-p (buffer-name standard-output)))
 141                      (setq help-return-method (cons (selected-window) t))
 142                      ;; If the help output buffer is a special display buffer,
 143                      ;; don't say anything about how to get rid of it.
 144                      ;; First of all, the user will do that with the window
 145                      ;; manager, not with Emacs.
 146                      ;; Secondly, the buffer has not been displayed yet,
 147                      ;; so we don't know whether its frame will be selected.
 148                      nil)
 149                     ((not (one-window-p t))
 150                      (setq help-return-method
 151                            (cons (selected-window) 'quit-window))
 152                      "Type \\[display-buffer] RET to restore the other window.")
 153                     (pop-up-windows
 154                      (setq help-return-method (cons (selected-window) t))
 155                      "Type \\[delete-other-windows] to remove help window.")
 156                     (t
 157                      (setq help-return-method
 158                            (list (selected-window) (window-buffer)
 159                                  (window-start) (window-point)))
 160                      "Type \\[switch-to-buffer] RET to remove help window."))))
 161          (funcall (or function 'message)
 162                   (concat
 163                    (if first-message
 164                        (substitute-command-keys first-message))
 165                    (if first-message "  ")
 166                    ;; If the help buffer will go in a separate frame,
 167                    ;; it's no use mentioning a command to scroll, so don't.
 168                    (if (or pop-up-windows
 169                            (special-display-p (buffer-name standard-output)))
 170                        nil
 171                      (if (same-window-p (buffer-name standard-output))
 172                          ;; Say how to scroll this window.
 173                          (substitute-command-keys
 174                           "\\[scroll-up] to scroll the help.")
 175                        ;; Say how to scroll some other window.
 176                        (substitute-command-keys
 177                         "\\[scroll-other-window] to scroll the help."))))))))
 178
 179 ;; So keyboard macro definitions are documented correctly
 180 (fset 'defining-kbd-macro (symbol-function 'start-kbd-macro))
 181
 182 (defalias 'help 'help-for-help-internal)
 183 ;; find-function can find this.
 184 (defalias 'help-for-help 'help-for-help-internal)
 185 ;; It can't find this, but nobody will look.
 186 (make-help-screen help-for-help-internal
 187   (purecopy "Type a help option: [abcCdefFgiIkKlLmnprstvw.] C-[cdefmnoptw] or ?")
 188   ;; Don't purecopy this one, because it's not evaluated (it's
 189   ;; directly used as a docstring in a function definition, so it'll
 190   ;; be moved to the DOC file anyway: no need for purecopying it).
 191   "You have typed %THIS-KEY%, the help character.  Type a Help option:
 192 \(Use SPC or DEL to scroll through this text.  Type \\<help-map>\\[help-quit] to exit the Help command.)
 193
 194 a PATTERN   Show commands whose name matches the PATTERN (a list of words
 195               or a regexp).  See also the `apropos' command.
 196 b           Display all key bindings.
 197 c KEYS      Display the command name run by the given key sequence.
 198 C CODING    Describe the given coding system, or RET for current ones.
 199 d PATTERN   Show a list of functions, variables, and other items whose
 200               documentation matches the PATTERN (a list of words or a regexp).
 201 e           Go to the *Messages* buffer which logs echo-area messages.
 202 f FUNCTION  Display documentation for the given function.
 203 F COMMAND   Show the on-line manual's section that describes the command.
 204 g           Display information about the GNU project.
 205 h           Display the HELLO file which illustrates various scripts.
 206 i           Start the Info documentation reader: read on-line manuals.
 207 I METHOD    Describe a specific input method, or RET for current.
 208 k KEYS      Display the full documentation for the key sequence.
 209 K KEYS      Show the on-line manual's section for the command bound to KEYS.
 210 l           Show last 300 input keystrokes (lossage).
 211 L LANG-ENV  Describes a specific language environment, or RET for current.
 212 m           Display documentation of current minor modes and current major mode,
 213               including their special commands.
 214 n           Display news of recent Emacs changes.
 215 p TOPIC     Find packages matching a given topic keyword.
 216 r           Display the Emacs manual in Info mode.
 217 s           Display contents of current syntax table, plus explanations.
 218 S SYMBOL    Show the section for the given symbol in the on-line manual
 219               for the programming language used in this buffer.
 220 t           Start the Emacs learn-by-doing tutorial.
 221 v VARIABLE  Display the given variable's documentation and value.
 222 w COMMAND   Display which keystrokes invoke the given command (where-is).
 223 .           Display any available local help at point in the echo area.
 224
 225 C-a         Information about Emacs.
 226 C-c         Emacs copying permission (GNU General Public License).
 227 C-d         Instructions for debugging GNU Emacs.
 228 C-e         External packages and information about Emacs.
 229 C-f         Emacs FAQ.
 230 C-m         How to order printed Emacs manuals.
 231 C-n         News of recent Emacs changes.
 232 C-o         Emacs ordering and distribution information.
 233 C-p         Info about known Emacs problems.
 234 C-t         Emacs TODO list.
 235 C-w         Information on absence of warranty for GNU Emacs."
 236   help-map)
 237
 238 \f
 239
 240 (defun function-called-at-point ()
 241   "Return a function around point or else called by the list containing point.
 242 If that doesn't give a function, return nil."
 243   (with-syntax-table emacs-lisp-mode-syntax-table
 244     (or (condition-case ()
 245             (save-excursion
 246               (or (not (zerop (skip-syntax-backward "_w")))
 247                   (eq (char-syntax (following-char)) ?w)
 248                   (eq (char-syntax (following-char)) ?_)
 249                   (forward-sexp -1))
 250               (skip-chars-forward "'")
 251               (let ((obj (read (current-buffer))))
 252                 (and (symbolp obj) (fboundp obj) obj)))
 253           (error nil))
 254         (condition-case ()
 255             (save-excursion
 256               (save-restriction
 257                 (narrow-to-region (max (point-min)
 258                                        (- (point) 1000)) (point-max))
 259                 ;; Move up to surrounding paren, then after the open.
 260                 (backward-up-list 1)
 261                 (forward-char 1)
 262                 ;; If there is space here, this is probably something
 263                 ;; other than a real Lisp function call, so ignore it.
 264                 (if (looking-at "[ \t]")
 265                     (error "Probably not a Lisp function call"))
 266                 (let ((obj (read (current-buffer))))
 267                   (and (symbolp obj) (fboundp obj) obj))))
 268           (error nil))
 269         (let* ((str (find-tag-default))
 270                (sym (if str (intern-soft str))))
 271           (if (and sym (fboundp sym))
 272               sym
 273             (save-match-data
 274               (when (and str (string-match "\\`\\W*\\(.*?\\)\\W*\\'" str))
 275                 (setq sym (intern-soft (match-string 1 str)))
 276                 (and (fboundp sym) sym))))))))
 277
 278 \f
 279 ;;; `User' help functions
 280
 281 (defun view-help-file (file &optional dir)
 282   (view-file (expand-file-name file (or dir data-directory)))
 283   (goto-address-mode 1)
 284   (goto-char (point-min)))
 285
 286 (defun describe-distribution ()
 287   "Display info on how to obtain the latest version of GNU Emacs."
 288   (interactive)
 289   (view-help-file "DISTRIB"))
 290
 291 (defun describe-copying ()
 292   "Display info on how you may redistribute copies of GNU Emacs."
 293   (interactive)
 294   (view-help-file "COPYING"))
 295
 296 (defun describe-gnu-project ()
 297   "Display info on the GNU project."
 298   (interactive)
 299   (view-help-file "THE-GNU-PROJECT"))
 300
 301 (define-obsolete-function-alias 'describe-project 'describe-gnu-project "22.2")
 302
 303 (defun describe-no-warranty ()
 304   "Display info on all the kinds of warranty Emacs does NOT have."
 305   (interactive)
 306   (describe-copying)
 307   (let (case-fold-search)
 308     (search-forward "Disclaimer of Warranty")
 309     (forward-line 0)
 310     (recenter 0)))
 311
 312 (defun describe-prefix-bindings ()
 313   "Describe the bindings of the prefix used to reach this command.
 314 The prefix described consists of all but the last event
 315 of the key sequence that ran this command."
 316   (interactive)
 317   (let ((key (this-command-keys)))
 318     (describe-bindings
 319      (if (stringp key)
 320          (substring key 0 (1- (length key)))
 321        (let ((prefix (make-vector (1- (length key)) nil))
 322              (i 0))
 323          (while (< i (length prefix))
 324            (aset prefix i (aref key i))
 325            (setq i (1+ i)))
 326          prefix)))))
 327 ;; Make C-h after a prefix, when not specifically bound,
 328 ;; run describe-prefix-bindings.
 329 (setq prefix-help-command 'describe-prefix-bindings)
 330
 331 (defun view-emacs-news (&optional version)
 332   "Display info on recent changes to Emacs.
 333 With argument, display info only for the selected version."
 334   (interactive "P")
 335   (unless version
 336     (setq version emacs-major-version))
 337   (when (consp version)
 338     (let* ((all-versions
 339             (let (res)
 340               (mapc
 341                (lambda (file)
 342                  (with-temp-buffer
 343                    (insert-file-contents
 344                     (expand-file-name file data-directory))
 345                    (while (re-search-forward
 346                            (if (member file '("NEWS.18" "NEWS.1-17"))
 347                                "Changes in \\(?:Emacs\\|version\\)?[ \t]*\\([0-9]+\\(?:\\.[0-9]+\\)?\\)"
 348                              "^\* [^0-9\n]*\\([0-9]+\\.[0-9]+\\)") nil t)
 349                      (setq res (cons (match-string-no-properties 1) res)))))
 350                (cons "NEWS"
 351                      (directory-files data-directory nil
 352                                       "^NEWS\\.[0-9][-0-9]*$" nil)))
 353               (sort (delete-dups res) (lambda (a b) (string< b a)))))
 354            (current (car all-versions)))
 355       (setq version (completing-read
 356                      (format "Read NEWS for the version (default %s): " current)
 357                      all-versions nil nil nil nil current))
 358       (if (integerp (string-to-number version))
 359           (setq version (string-to-number version))
 360         (unless (or (member version all-versions)
 361                     (<= (string-to-number version) (string-to-number current)))
 362           (error "No news about version %s" version)))))
 363   (when (integerp version)
 364     (cond ((<= version 12)
 365            (setq version (format "1.%d" version)))
 366           ((<= version 18)
 367            (setq version (format "%d" version)))
 368           ((> version emacs-major-version)
 369            (error "No news about Emacs %d (yet)" version))))
 370   (let* ((vn (if (stringp version)
 371                  (string-to-number version)
 372                version))
 373          (file (cond
 374                 ((>= vn emacs-major-version) "NEWS")
 375                 ((< vn 18) "NEWS.1-17")
 376                 (t (format "NEWS.%d" vn))))
 377          res)
 378     (view-file (expand-file-name file data-directory))
 379     (widen)
 380     (goto-char (point-min))
 381     (when (stringp version)
 382       (when (re-search-forward
 383              (concat (if (< vn 19)
 384                          "Changes in Emacs[ \t]*"
 385                        "^\* [^0-9\n]*") version "$")
 386              nil t)
 387         (beginning-of-line)
 388         (narrow-to-region
 389          (point)
 390          (save-excursion
 391            (while (and (setq res
 392                              (re-search-forward
 393                               (if (< vn 19)
 394                                   "Changes in \\(?:Emacs\\|version\\)?[ \t]*\\([0-9]+\\(?:\\.[0-9]+\\)?\\)"
 395                                 "^\* [^0-9\n]*\\([0-9]+\\.[0-9]+\\)") nil t))
 396                        (equal (match-string-no-properties 1) version)))
 397            (or res (goto-char (point-max)))
 398            (beginning-of-line)
 399            (point)))))))
 400
 401 (defun view-emacs-todo (&optional _arg)
 402   "Display the Emacs TODO list."
 403   (interactive "P")
 404   (view-help-file "TODO"))
 405
 406 (define-obsolete-function-alias 'view-todo 'view-emacs-todo "22.2")
 407
 408
 409 (defun view-echo-area-messages ()
 410   "View the log of recent echo-area messages: the `*Messages*' buffer.
 411 The number of messages retained in that buffer
 412 is specified by the variable `message-log-max'."
 413   (interactive)
 414   (switch-to-buffer (get-buffer-create "*Messages*")))
 415
 416 (defun view-order-manuals ()
 417   "Display the Emacs ORDERS file."
 418   (interactive)
 419   (view-help-file "ORDERS"))
 420
 421 (defun view-emacs-FAQ ()
 422   "Display the Emacs Frequently Asked Questions (FAQ) file."
 423   (interactive)
 424   ;; (find-file-read-only (expand-file-name "FAQ" data-directory))
 425   (info "(efaq)"))
 426
 427 (defun view-emacs-problems ()
 428   "Display info on known problems with Emacs and possible workarounds."
 429   (interactive)
 430   (view-help-file "PROBLEMS"))
 431
 432 (defun view-emacs-debugging ()
 433   "Display info on how to debug Emacs problems."
 434   (interactive)
 435   (view-help-file "DEBUG"))
 436
 437 (defun view-external-packages ()
 438   "Display external packages and information about Emacs."
 439   (interactive)
 440   (view-help-file "MORE.STUFF"))
 441
 442 (defun view-lossage ()
 443   "Display last 300 input keystrokes.
 444
 445 To record all your input on a file, use `open-dribble-file'."
 446   (interactive)
 447   (help-setup-xref (list #'view-lossage)
 448                    (called-interactively-p 'interactive))
 449   (with-help-window (help-buffer)
 450     (princ (mapconcat (lambda (key)
 451                         (if (or (integerp key) (symbolp key) (listp key))
 452                             (single-key-description key)
 453                           (prin1-to-string key nil)))
 454                       (recent-keys)
 455                       " "))
 456     (with-current-buffer standard-output
 457       (goto-char (point-min))
 458       (while (progn (move-to-column 50) (not (eobp)))
 459         (when (search-forward " " nil t)
 460           (delete-char -1))
 461         (insert "\n"))
 462       ;; jidanni wants to see the last keystrokes immediately.
 463       (set-marker help-window-point-marker (point)))))
 464
 465 \f
 466 ;; Key bindings
 467
 468 (defun describe-bindings (&optional prefix buffer)
 469   "Show a list of all defined keys, and their definitions.
 470 We put that list in a buffer, and display the buffer.
 471
 472 The optional argument PREFIX, if non-nil, should be a key sequence;
 473 then we display only bindings that start with that prefix.
 474 The optional argument BUFFER specifies which buffer's bindings
 475 to display (default, the current buffer).  BUFFER can be a buffer
 476 or a buffer name."
 477   (interactive)
 478   (or buffer (setq buffer (current-buffer)))
 479   (help-setup-xref (list #'describe-bindings prefix buffer)
 480                    (called-interactively-p 'interactive))
 481   (with-current-buffer buffer
 482     (describe-bindings-internal nil prefix)))
 483
 484 ;; This function used to be in keymap.c.
 485 (defun describe-bindings-internal (&optional menus prefix)
 486   "Show a list of all defined keys, and their definitions.
 487 We put that list in a buffer, and display the buffer.
 488
 489 The optional argument MENUS, if non-nil, says to mention menu bindings.
 490 \(Ordinarily these are omitted from the output.)
 491 The optional argument PREFIX, if non-nil, should be a key sequence;
 492 then we display only bindings that start with that prefix."
 493   (let ((buf (current-buffer)))
 494     (with-help-window "*Help*"
 495       (with-current-buffer standard-output
 496         (describe-buffer-bindings buf prefix menus)))))
 497
 498 (defun where-is (definition &optional insert)
 499   "Print message listing key sequences that invoke the command DEFINITION.
 500 Argument is a command definition, usually a symbol with a function definition.
 501 If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
 502   (interactive
 503    (let ((fn (function-called-at-point))
 504          (enable-recursive-minibuffers t)
 505          val)
 506      (setq val (completing-read
 507                 (if fn
 508                     (format "Where is command (default %s): " fn)
 509                   "Where is command: ")
 510                 obarray 'commandp t))
 511      (list (if (equal val "") fn (intern val)) current-prefix-arg)))
 512   (unless definition (error "No command"))
 513   (let ((func (indirect-function definition))
 514         (defs nil)
 515         (standard-output (if insert (current-buffer) standard-output)))
 516     ;; In DEFS, find all symbols that are aliases for DEFINITION.
 517     (mapatoms (lambda (symbol)
 518                 (and (fboundp symbol)
 519                      (not (eq symbol definition))
 520                      (eq func (condition-case ()
 521                                   (indirect-function symbol)
 522                                 (error symbol)))
 523                      (push symbol defs))))
 524     ;; Look at all the symbols--first DEFINITION,
 525     ;; then its aliases.
 526     (dolist (symbol (cons definition defs))
 527       (let* ((remapped (command-remapping symbol))
 528              (keys (where-is-internal
 529                     symbol overriding-local-map nil nil remapped))
 530              (keys (mapconcat 'key-description keys ", "))
 531              string)
 532         (setq string
 533               (if insert
 534                   (if (> (length keys) 0)
 535                       (if remapped
 536                           (format "%s (%s) (remapped from %s)"
 537                                   keys remapped symbol)
 538                         (format "%s (%s)" keys symbol))
 539                     (format "M-x %s RET" symbol))
 540                 (if (> (length keys) 0)
 541                     (if remapped
 542                         (format "%s is remapped to %s which is on %s"
 543                                 symbol remapped keys)
 544                       (format "%s is on %s" symbol keys))
 545                   ;; If this is the command the user asked about,
 546                   ;; and it is not on any key, say so.
 547                   ;; For other symbols, its aliases, say nothing
 548                   ;; about them unless they are on keys.
 549                   (if (eq symbol definition)
 550                       (format "%s is not on any key" symbol)))))
 551         (when string
 552           (unless (eq symbol definition)
 553             (princ ";\n its alias "))
 554           (princ string)))))
 555   nil)
 556
 557 (defun help-key-description (key untranslated)
 558   (let ((string (key-description key)))
 559     (if (or (not untranslated)
 560             (and (eq (aref untranslated 0) ?\e) (not (eq (aref key 0) ?\e))))
 561         string
 562       (let ((otherstring (key-description untranslated)))
 563         (if (equal string otherstring)
 564             string
 565           (format "%s (translated from %s)" string otherstring))))))
 566
 567 (defun describe-key-briefly (&optional key insert untranslated)
 568   "Print the name of the function KEY invokes.  KEY is a string.
 569 If INSERT (the prefix arg) is non-nil, insert the message in the buffer.
 570 If non-nil, UNTRANSLATED is a vector of the untranslated events.
 571 It can also be a number in which case the untranslated events from
 572 the last key hit are used.
 573
 574 If KEY is a menu item or a tool-bar button that is disabled, this command
 575 temporarily enables it to allow getting help on disabled items and buttons."
 576   (interactive
 577    (let ((enable-disabled-menus-and-buttons t)
 578          (cursor-in-echo-area t)
 579          saved-yank-menu)
 580      (unwind-protect
 581          (let (key)
 582            ;; If yank-menu is empty, populate it temporarily, so that
 583            ;; "Select and Paste" menu can generate a complete event.
 584            (when (null (cdr yank-menu))
 585              (setq saved-yank-menu (copy-sequence yank-menu))
 586              (menu-bar-update-yank-menu "(any string)" nil))
 587            (setq key (read-key-sequence "Describe key (or click or menu item): "))
 588            ;; If KEY is a down-event, read and discard the
 589            ;; corresponding up-event.  Note that there are also
 590            ;; down-events on scroll bars and mode lines: the actual
 591            ;; event then is in the second element of the vector.
 592            (and (vectorp key)
 593                 (let ((last-idx (1- (length key))))
 594                   (and (eventp (aref key last-idx))
 595                        (memq 'down (event-modifiers (aref key last-idx)))))
 596                 (read-event))
 597            (list
 598             key
 599             (if current-prefix-arg (prefix-numeric-value current-prefix-arg))
 600             1))
 601        ;; Put yank-menu back as it was, if we changed it.
 602        (when saved-yank-menu
 603          (setq yank-menu (copy-sequence saved-yank-menu))
 604          (fset 'yank-menu (cons 'keymap yank-menu))))))
 605   (if (numberp untranslated)
 606       (setq untranslated (this-single-command-raw-keys)))
 607   (let* ((event (if (and (symbolp (aref key 0))
 608                          (> (length key) 1)
 609                          (consp (aref key 1)))
 610                     (aref key 1)
 611                   (aref key 0)))
 612          (modifiers (event-modifiers event))
 613          (standard-output (if insert (current-buffer) standard-output))
 614          (mouse-msg (if (or (memq 'click modifiers) (memq 'down modifiers)
 615                             (memq 'drag modifiers)) " at that spot" ""))
 616          (defn (key-binding key t))
 617          key-desc)
 618     ;; Handle the case where we faked an entry in "Select and Paste" menu.
 619     (if (and (eq defn nil)
 620              (stringp (aref key (1- (length key))))
 621              (eq (key-binding (substring key 0 -1)) 'yank-menu))
 622         (setq defn 'menu-bar-select-yank))
 623     ;; Don't bother user with strings from (e.g.) the select-paste menu.
 624     (if (stringp (aref key (1- (length key))))
 625         (aset key (1- (length key)) "(any string)"))
 626     (if (and (> (length untranslated) 0)
 627              (stringp (aref untranslated (1- (length untranslated)))))
 628         (aset untranslated (1- (length untranslated)) "(any string)"))
 629     ;; Now describe the key, perhaps as changed.
 630     (setq key-desc (help-key-description key untranslated))
 631     (if (or (null defn) (integerp defn) (equal defn 'undefined))
 632         (princ (format "%s%s is undefined" key-desc mouse-msg))
 633       (princ (format "%s%s runs the command %S" key-desc mouse-msg defn)))))
 634
 635 (defun describe-key (&optional key untranslated up-event)
 636   "Display documentation of the function invoked by KEY.
 637 KEY can be any kind of a key sequence; it can include keyboard events,
 638 mouse events, and/or menu events.  When calling from a program,
 639 pass KEY as a string or a vector.
 640
 641 If non-nil, UNTRANSLATED is a vector of the corresponding untranslated events.
 642 It can also be a number, in which case the untranslated events from
 643 the last key sequence entered are used.
 644 UP-EVENT is the up-event that was discarded by reading KEY, or nil.
 645
 646 If KEY is a menu item or a tool-bar button that is disabled, this command
 647 temporarily enables it to allow getting help on disabled items and buttons."
 648   (interactive
 649    (let ((enable-disabled-menus-and-buttons t)
 650          (cursor-in-echo-area t)
 651          saved-yank-menu)
 652      (unwind-protect
 653          (let (key)
 654            ;; If yank-menu is empty, populate it temporarily, so that
 655            ;; "Select and Paste" menu can generate a complete event.
 656            (when (null (cdr yank-menu))
 657              (setq saved-yank-menu (copy-sequence yank-menu))
 658              (menu-bar-update-yank-menu "(any string)" nil))
 659            (setq key (read-key-sequence "Describe key (or click or menu item): "))
 660            (list
 661             key
 662             (prefix-numeric-value current-prefix-arg)
 663             ;; If KEY is a down-event, read and include the
 664             ;; corresponding up-event.  Note that there are also
 665             ;; down-events on scroll bars and mode lines: the actual
 666             ;; event then is in the second element of the vector.
 667             (and (vectorp key)
 668                  (let ((last-idx (1- (length key))))
 669                    (and (eventp (aref key last-idx))
 670                         (memq 'down (event-modifiers (aref key last-idx)))))
 671                  (or (and (eventp (aref key 0))
 672                           (memq 'down (event-modifiers (aref key 0)))
 673                           ;; However, for the C-down-mouse-2 popup
 674                           ;; menu, there is no subsequent up-event.  In
 675                           ;; this case, the up-event is the next
 676                           ;; element in the supplied vector.
 677                           (= (length key) 1))
 678                      (and (> (length key) 1)
 679                           (eventp (aref key 1))
 680                           (memq 'down (event-modifiers (aref key 1)))))
 681                  (read-event))))
 682        ;; Put yank-menu back as it was, if we changed it.
 683        (when saved-yank-menu
 684          (setq yank-menu (copy-sequence saved-yank-menu))
 685          (fset 'yank-menu (cons 'keymap yank-menu))))))
 686   (if (numberp untranslated)
 687       (setq untranslated (this-single-command-raw-keys)))
 688   (let* ((event (aref key (if (and (symbolp (aref key 0))
 689                                    (> (length key) 1)
 690                                    (consp (aref key 1)))
 691                               1
 692                             0)))
 693          (modifiers (event-modifiers event))
 694          (mouse-msg (if (or (memq 'click modifiers) (memq 'down modifiers)
 695                             (memq 'drag modifiers)) " at that spot" ""))
 696          (defn (key-binding key t))
 697          defn-up defn-up-tricky ev-type
 698          mouse-1-remapped mouse-1-tricky)
 699
 700     ;; Handle the case where we faked an entry in "Select and Paste" menu.
 701     (when (and (eq defn nil)
 702                (stringp (aref key (1- (length key))))
 703                (eq (key-binding (substring key 0 -1)) 'yank-menu))
 704       (setq defn 'menu-bar-select-yank))
 705     (if (or (null defn) (integerp defn) (equal defn 'undefined))
 706         (message "%s%s is undefined"
 707                  (help-key-description key untranslated) mouse-msg)
 708       (help-setup-xref (list #'describe-function defn)
 709                        (called-interactively-p 'interactive))
 710       ;; Don't bother user with strings from (e.g.) the select-paste menu.
 711       (when (stringp (aref key (1- (length key))))
 712         (aset key (1- (length key)) "(any string)"))
 713       (when (and untranslated
 714                  (stringp (aref untranslated (1- (length untranslated)))))
 715         (aset untranslated (1- (length untranslated))
 716               "(any string)"))
 717       ;; Need to do this before erasing *Help* buffer in case event
 718       ;; is a mouse click in an existing *Help* buffer.
 719       (when up-event
 720         (setq ev-type (event-basic-type up-event))
 721         (let ((sequence (vector up-event)))
 722           (when (and (eq ev-type 'mouse-1)
 723                      mouse-1-click-follows-link
 724                      (not (eq mouse-1-click-follows-link 'double))
 725                      (setq mouse-1-remapped
 726                            (mouse-on-link-p (event-start up-event))))
 727             (setq mouse-1-tricky (and (integerp mouse-1-click-follows-link)
 728                                       (> mouse-1-click-follows-link 0)))
 729             (cond ((stringp mouse-1-remapped)
 730                    (setq sequence mouse-1-remapped))
 731                   ((vectorp mouse-1-remapped)
 732                    (setcar up-event (elt mouse-1-remapped 0)))
 733                   (t (setcar up-event 'mouse-2))))
 734           (setq defn-up (key-binding sequence nil nil (event-start up-event)))
 735           (when mouse-1-tricky
 736             (setq sequence (vector up-event))
 737             (aset sequence 0 'mouse-1)
 738             (setq defn-up-tricky (key-binding sequence nil nil (event-start up-event))))))
 739       (with-help-window (help-buffer)
 740         (princ (help-key-description key untranslated))
 741         (princ (format "\
 742 %s runs the command %S, which is "
 743                        mouse-msg defn))
 744         (describe-function-1 defn)
 745         (when up-event
 746           (unless (or (null defn-up)
 747                       (integerp defn-up)
 748                       (equal defn-up 'undefined))
 749             (princ (format "
 750
 751 ----------------- up-event %s----------------
 752
 753 %s%s%s runs the command %S, which is "
 754                            (if mouse-1-tricky "(short click) " "")
 755                            (key-description (vector up-event))
 756                            mouse-msg
 757                            (if mouse-1-remapped
 758                                " is remapped to <mouse-2>, which" "")
 759                            defn-up))
 760             (describe-function-1 defn-up))
 761           (unless (or (null defn-up-tricky)
 762                       (integerp defn-up-tricky)
 763                       (eq defn-up-tricky 'undefined))
 764             (princ (format "
 765
 766 ----------------- up-event (long click) ----------------
 767
 768 Pressing <%S>%s for longer than %d milli-seconds
 769 runs the command %S, which is "
 770                            ev-type mouse-msg
 771                            mouse-1-click-follows-link
 772                            defn-up-tricky))
 773             (describe-function-1 defn-up-tricky)))))))
 774 \f
 775 (defun describe-mode (&optional buffer)
 776   "Display documentation of current major mode and minor modes.
 777 A brief summary of the minor modes comes first, followed by the
 778 major mode description.  This is followed by detailed
 779 descriptions of the minor modes, each on a separate page.
 780
 781 For this to work correctly for a minor mode, the mode's indicator
 782 variable \(listed in `minor-mode-alist') must also be a function
 783 whose documentation describes the minor mode.
 784
 785 If called from Lisp with a non-nil BUFFER argument, display
 786 documentation for the major and minor modes of that buffer."
 787   (interactive "@")
 788   (unless buffer (setq buffer (current-buffer)))
 789   (help-setup-xref (list #'describe-mode buffer)
 790                    (called-interactively-p 'interactive))
 791   ;; For the sake of help-do-xref and help-xref-go-back,
 792   ;; don't switch buffers before calling `help-buffer'.
 793   (with-help-window (help-buffer)
 794     (with-current-buffer buffer
 795       (let (minor-modes)
 796         ;; Older packages do not register in minor-mode-list but only in
 797         ;; minor-mode-alist.
 798         (dolist (x minor-mode-alist)
 799           (setq x (car x))
 800           (unless (memq x minor-mode-list)
 801             (push x minor-mode-list)))
 802         ;; Find enabled minor mode we will want to mention.
 803         (dolist (mode minor-mode-list)
 804           ;; Document a minor mode if it is listed in minor-mode-alist,
 805           ;; non-nil, and has a function definition.
 806           (let ((fmode (or (get mode :minor-mode-function) mode)))
 807             (and (boundp mode) (symbol-value mode)
 808                  (fboundp fmode)
 809                  (let ((pretty-minor-mode
 810                         (if (string-match "\\(\\(-minor\\)?-mode\\)?\\'"
 811                                           (symbol-name fmode))
 812                             (capitalize
 813                              (substring (symbol-name fmode)
 814                                         0 (match-beginning 0)))
 815                           fmode)))
 816                    (push (list fmode pretty-minor-mode
 817                                (format-mode-line (assq mode minor-mode-alist)))
 818                          minor-modes)))))
 819         (setq minor-modes
 820               (sort minor-modes
 821                     (lambda (a b) (string-lessp (cadr a) (cadr b)))))
 822         (when minor-modes
 823           (princ "Enabled minor modes:\n")
 824           (make-local-variable 'help-button-cache)
 825           (with-current-buffer standard-output
 826             (dolist (mode minor-modes)
 827               (let ((mode-function (nth 0 mode))
 828                     (pretty-minor-mode (nth 1 mode))
 829                     (indicator (nth 2 mode)))
 830                 (add-text-properties 0 (length pretty-minor-mode)
 831                                      '(face bold) pretty-minor-mode)
 832                 (save-excursion
 833                   (goto-char (point-max))
 834                   (princ "\n\f\n")
 835                   (push (point-marker) help-button-cache)
 836                   ;; Document the minor modes fully.
 837                   (insert pretty-minor-mode)
 838                   (princ (format " minor mode (%s):\n"
 839                                  (if (zerop (length indicator))
 840                                      "no indicator"
 841                                    (format "indicator%s"
 842                                            indicator))))
 843                   (princ (documentation mode-function)))
 844                 (insert-button pretty-minor-mode
 845                                'action (car help-button-cache)
 846                                'follow-link t
 847                                'help-echo "mouse-2, RET: show full information")
 848                 (newline)))
 849             (forward-line -1)
 850             (fill-paragraph nil)
 851             (forward-line 1))
 852
 853           (princ "\n(Information about these minor modes follows the major mode info.)\n\n"))
 854         ;; Document the major mode.
 855         (let ((mode mode-name))
 856           (with-current-buffer standard-output
 857             (let ((start (point)))
 858               (insert (format-mode-line mode nil nil buffer))
 859               (add-text-properties start (point) '(face bold)))))
 860         (princ " mode")
 861         (let* ((mode major-mode)
 862                (file-name (find-lisp-object-file-name mode nil)))
 863           (when file-name
 864             (princ (concat " defined in `" (file-name-nondirectory file-name) "'"))
 865             ;; Make a hyperlink to the library.
 866             (with-current-buffer standard-output
 867               (save-excursion
 868                 (re-search-backward "`\\([^`']+\\)'" nil t)
 869                 (help-xref-button 1 'help-function-def mode file-name)))))
 870         (princ ":\n")
 871         (princ (documentation major-mode)))))
 872   ;; For the sake of IELM and maybe others
 873   nil)
 874
 875
 876 (defun describe-minor-mode (minor-mode)
 877   "Display documentation of a minor mode given as MINOR-MODE.
 878 MINOR-MODE can be a minor mode symbol or a minor mode indicator string
 879 appeared on the mode-line."
 880   (interactive (list (completing-read
 881                       "Minor mode: "
 882                               (nconc
 883                                (describe-minor-mode-completion-table-for-symbol)
 884                                (describe-minor-mode-completion-table-for-indicator)
 885                                ))))
 886   (if (symbolp minor-mode)
 887       (setq minor-mode (symbol-name minor-mode)))
 888   (let ((symbols (describe-minor-mode-completion-table-for-symbol))
 889         (indicators (describe-minor-mode-completion-table-for-indicator)))
 890     (cond
 891      ((member minor-mode symbols)
 892       (describe-minor-mode-from-symbol (intern minor-mode)))
 893      ((member minor-mode indicators)
 894       (describe-minor-mode-from-indicator minor-mode))
 895      (t
 896       (error "No such minor mode: %s" minor-mode)))))
 897
 898 ;; symbol
 899 (defun describe-minor-mode-completion-table-for-symbol ()
 900   ;; In order to list up all minor modes, minor-mode-list
 901   ;; is used here instead of minor-mode-alist.
 902   (delq nil (mapcar 'symbol-name minor-mode-list)))
 903
 904 (defun describe-minor-mode-from-symbol (symbol)
 905   "Display documentation of a minor mode given as a symbol, SYMBOL"
 906   (interactive (list (intern (completing-read
 907                               "Minor mode symbol: "
 908                               (describe-minor-mode-completion-table-for-symbol)))))
 909   (if (fboundp symbol)
 910       (describe-function symbol)
 911     (describe-variable symbol)))
 912
 913 ;; indicator
 914 (defun describe-minor-mode-completion-table-for-indicator ()
 915   (delq nil
 916         (mapcar (lambda (x)
 917                   (let ((i (format-mode-line x)))
 918                     ;; remove first space if existed
 919                     (cond
 920                      ((= 0 (length i))
 921                       nil)
 922                      ((eq (aref i 0) ?\s)
 923                       (substring i 1))
 924                      (t
 925                       i))))
 926                 minor-mode-alist)))
 927
 928 (defun describe-minor-mode-from-indicator (indicator)
 929   "Display documentation of a minor mode specified by INDICATOR.
 930 If you call this function interactively, you can give indicator which
 931 is currently activated with completion."
 932   (interactive (list
 933                 (completing-read
 934                  "Minor mode indicator: "
 935                  (describe-minor-mode-completion-table-for-indicator))))
 936   (let ((minor-mode (lookup-minor-mode-from-indicator indicator)))
 937     (if minor-mode
 938         (describe-minor-mode-from-symbol minor-mode)
 939       (error "Cannot find minor mode for `%s'" indicator))))
 940
 941 (defun lookup-minor-mode-from-indicator (indicator)
 942   "Return a minor mode symbol from its indicator on the mode line."
 943   ;; remove first space if existed
 944   (if (and (< 0 (length indicator))
 945            (eq (aref indicator 0) ?\s))
 946       (setq indicator (substring indicator 1)))
 947   (let ((minor-modes minor-mode-alist)
 948         result)
 949     (while minor-modes
 950       (let* ((minor-mode (car (car minor-modes)))
 951              (anindicator (format-mode-line
 952                            (car (cdr (car minor-modes))))))
 953         ;; remove first space if existed
 954         (if (and (stringp anindicator)
 955                  (> (length anindicator) 0)
 956                  (eq (aref anindicator 0) ?\s))
 957             (setq anindicator (substring anindicator 1)))
 958         (if (equal indicator anindicator)
 959             (setq result minor-mode
 960                   minor-modes nil)
 961           (setq minor-modes (cdr minor-modes)))))
 962     result))
 963 \f
 964 ;;; Automatic resizing of temporary buffers.
 965 (defcustom temp-buffer-max-height (lambda (buffer) (/ (- (frame-height) 2) 2))
 966   "Maximum height of a window displaying a temporary buffer.
 967 This is effective only when Temp Buffer Resize mode is enabled.
 968 The value is the maximum height (in lines) which
 969 `resize-temp-buffer-window' will give to a window displaying a
 970 temporary buffer.  It can also be a function to be called to
 971 choose the height for such a buffer.  It gets one argument, the
 972 buffer, and should return a positive integer.  At the time the
 973 function is called, the window to be resized is selected."
 974   :type '(choice integer function)
 975   :group 'help
 976   :version "20.4")
 977
 978 (define-minor-mode temp-buffer-resize-mode
 979   "Toggle auto-resizing temporary buffer windows (Temp Buffer Resize Mode).
 980 With a prefix argument ARG, enable Temp Buffer Resize mode if ARG
 981 is positive, and disable it otherwise.  If called from Lisp,
 982 enable the mode if ARG is omitted or nil.
 983
 984 When Temp Buffer Resize mode is enabled, the windows in which we
 985 show a temporary buffer are automatically resized in height to
 986 fit the buffer's contents, but never more than
 987 `temp-buffer-max-height' nor less than `window-min-height'.
 988
 989 This mode is used by `help', `apropos' and `completion' buffers,
 990 and some others."
 991   :global t :group 'help
 992   (if temp-buffer-resize-mode
 993       ;; `help-make-xrefs' may add a `back' button and thus increase the
 994       ;; text size, so `resize-temp-buffer-window' must be run *after* it.
 995       (add-hook 'temp-buffer-show-hook 'resize-temp-buffer-window 'append)
 996     (remove-hook 'temp-buffer-show-hook 'resize-temp-buffer-window)))
 997
 998 (defun resize-temp-buffer-window (&optional window)
 999   "Resize WINDOW to fit its contents.
1000 WINDOW can be any live window and defaults to the selected one.
1001
1002 Do not make WINDOW higher than `temp-buffer-max-height' nor
1003 smaller than `window-min-height'.  Do nothing if WINDOW is not
1004 vertically combined or some of its contents are scrolled out of
1005 view."
1006   (setq window (window-normalize-window window t))
1007   (let ((height (if (functionp temp-buffer-max-height)
1008                     (with-selected-window window
1009                       (funcall temp-buffer-max-height (window-buffer)))
1010                   temp-buffer-max-height)))
1011     (when (and (pos-visible-in-window-p (point-min) window)
1012                (window-combined-p window))
1013       (fit-window-to-buffer window height))))
1014
1015 ;;; Help windows.
1016 (defcustom help-window-select 'other
1017     "Non-nil means select help window for viewing.
1018 Choices are:
1019  never (nil) Select help window only if there is no other window
1020              on its frame.
1021  other       Select help window unless the selected window is the
1022              only other window on the help window's frame.
1023  always (t)  Always select the help window.
1024
1025 This option has effect if and only if the help window was created
1026 by `with-help-window'"
1027   :type '(choice (const :tag "never (nil)" nil)
1028                  (const :tag "other" other)
1029                  (const :tag "always (t)" t))
1030   :group 'help
1031   :version "23.1")
1032
1033 (defcustom help-enable-auto-load t
1034   "Whether Help commands can perform autoloading.
1035 If non-nil, whenever \\[describe-function] is called for an
1036 autoloaded function whose docstring contains any key substitution
1037 construct (see `substitute-command-keys'), the library is loaded,
1038 so that the documentation can show the right key bindings."
1039   :type 'boolean
1040   :group 'help
1041   :version "24.3")
1042
1043 (defun help-window-display-message (quit-part window &optional scroll)
1044   "Display message telling how to quit and scroll help window.
1045 QUIT-PART is a string telling how to quit the help window WINDOW.
1046 Optional argument SCROLL non-nil means tell how to scroll WINDOW.
1047 SCROLL equal `other' means tell how to scroll the \"other\"
1048 window."
1049   (let ((scroll-part
1050          (cond
1051           ;; If we don't have QUIT-PART we probably reuse a window
1052           ;; showing the same buffer so we don't show any message.
1053           ((not quit-part) nil)
1054           ((pos-visible-in-window-p
1055             (with-current-buffer (window-buffer window)
1056               (point-max)) window t)
1057            ;; Buffer end is at least partially visible, no need to talk
1058            ;; about scrolling.
1059            ".")
1060           ((eq scroll 'other)
1061            ", \\[scroll-other-window] to scroll help.")
1062           (scroll ", \\[scroll-up] to scroll help."))))
1063     (message "%s"
1064      (substitute-command-keys (concat quit-part scroll-part)))))
1065
1066 (defun help-window-setup (help-window)
1067   "Set up help window for `with-help-window'.
1068 HELP-WINDOW is the window used for displaying the help buffer."
1069   (let* ((help-buffer (when (window-live-p help-window)
1070                         (window-buffer help-window)))
1071          (help-setup (when (window-live-p help-window)
1072                        (car (window-parameter help-window 'quit-restore)))))
1073     (when help-buffer
1074       ;; Handle `help-window-point-marker'.
1075       (when (eq (marker-buffer help-window-point-marker) help-buffer)
1076         (set-window-point help-window help-window-point-marker)
1077         ;; Reset `help-window-point-marker'.
1078         (set-marker help-window-point-marker nil))
1079
1080       (cond
1081        ((or (eq help-window (selected-window))
1082             (and (or (eq help-window-select t)
1083                      (eq help-setup 'frame)
1084                      (and (eq help-window-select 'other)
1085                           (eq (window-frame help-window) (selected-frame))
1086                           (> (length (window-list nil 'no-mini)) 2)))
1087                  (select-window help-window)))
1088         ;; The help window is or gets selected ...
1089         (help-window-display-message
1090          (cond
1091           ((eq help-setup 'window)
1092            ;; ... and is new, ...
1093            "Type \"q\" to delete help window")
1094           ((eq help-setup 'frame)
1095            "Type \"q\" to delete help frame")
1096           ((eq help-setup 'other)
1097            ;; ... or displayed some other buffer before.
1098            "Type \"q\" to restore previous buffer"))
1099          help-window t))
1100        ((and (eq (window-frame help-window) (selected-frame))
1101              (= (length (window-list nil 'no-mini)) 2))
1102         ;; There are two windows on the help window's frame and the
1103         ;; other one is the selected one.
1104         (help-window-display-message
1105          (cond
1106           ((eq help-setup 'window)
1107            "Type \\[delete-other-windows] to delete the help window")
1108           ((eq help-setup 'other)
1109            "Type \"q\" in help window to restore its previous buffer"))
1110          help-window 'other))
1111        (t
1112         ;; The help window is not selected ...
1113         (help-window-display-message
1114          (cond
1115           ((eq help-setup 'window)
1116            ;; ... and is new, ...
1117            "Type \"q\" in help window to delete it")
1118           ((eq help-setup 'other)
1119            ;; ... or displayed some other buffer before.
1120            "Type \"q\" in help window to restore previous buffer"))
1121          help-window))))))
1122
1123 ;; `with-help-window' is a wrapper for `with-output-to-temp-buffer'
1124 ;; providing the following additional twists:
1125
1126 ;; (1) Issue more accurate messages telling how to scroll and quit the
1127 ;; help window.
1128
1129 ;; (2) An option (customizable via `help-window-select') to select the
1130 ;; help window automatically.
1131
1132 ;; (3) A marker (`help-window-point-marker') to move point in the help
1133 ;; window to an arbitrary buffer position.
1134
1135 ;; Note: It's usually always wrong to use `help-print-return-message' in
1136 ;; the body of `with-help-window'.
1137 (defmacro with-help-window (buffer-name &rest body)
1138   "Display buffer with name BUFFER-NAME in a help window evaluating BODY.
1139 Select help window if the actual value of the user option
1140 `help-window-select' says so.  Return last value in BODY."
1141   (declare (indent 1) (debug t))
1142   `(progn
1143      ;; Make `help-window-point-marker' point nowhere.  The only place
1144      ;; where this should be set to a buffer position is within BODY.
1145      (set-marker help-window-point-marker nil)
1146      (let* (help-window
1147             (temp-buffer-show-hook
1148              (cons (lambda () (setq help-window (selected-window)))
1149                    temp-buffer-show-hook)))
1150        ;; Return value returned by `with-output-to-temp-buffer'.
1151        (prog1
1152            (with-output-to-temp-buffer ,buffer-name
1153              (progn ,@body))
1154          (help-window-setup help-window)))))
1155
1156 ;; Called from C, on encountering `help-char' when reading a char.
1157 ;; Don't print to *Help*; that would clobber Help history.
1158 (defun help-form-show ()
1159   "Display the output of a non-nil `help-form'."
1160   (let ((msg (eval help-form)))
1161     (if (stringp msg)
1162         (with-output-to-temp-buffer " *Char Help*"
1163           (princ msg)))))
1164 \f
1165 (provide 'help)
1166
1167 ;;; help.el ends here