lisp/help.el

   1 ;;; help.el --- help commands for Emacs
   2
   3 ;; Copyright (C) 1985-1986, 1993-1994, 1998-2014 Free Software Foundation, Inc.
   4
   5 ;; Maintainer: emacs-devel@gnu.org
   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 ;; `help-window-point-marker' is a marker you can move to a valid
  36 ;; position of the buffer shown in the help window in order to override
  37 ;; the standard positioning mechanism (`point-min') chosen by
  38 ;; `with-output-to-temp-buffer' and `with-temp-buffer-window'.
  39 ;; `with-help-window' has this point nowhere before exiting.  Currently
  40 ;; used by `view-lossage' to assert that the last keystrokes are always
  41 ;; visible.
  42 (defvar help-window-point-marker (make-marker)
  43   "Marker to override default `window-point' in help windows.")
  44
  45 (defvar help-map
  46   (let ((map (make-sparse-keymap)))
  47     (define-key map (char-to-string help-char) 'help-for-help)
  48     (define-key map [help] 'help-for-help)
  49     (define-key map [f1] 'help-for-help)
  50     (define-key map "." 'display-local-help)
  51     (define-key map "?" 'help-for-help)
  52
  53     (define-key map "\C-a" 'about-emacs)
  54     (define-key map "\C-c" 'describe-copying)
  55     (define-key map "\C-d" 'view-emacs-debugging)
  56     (define-key map "\C-e" 'view-external-packages)
  57     (define-key map "\C-f" 'view-emacs-FAQ)
  58     (define-key map "\C-m" 'view-order-manuals)
  59     (define-key map "\C-n" 'view-emacs-news)
  60     (define-key map "\C-o" 'describe-distribution)
  61     (define-key map "\C-p" 'view-emacs-problems)
  62     (define-key map "\C-t" 'view-emacs-todo)
  63     (define-key map "\C-w" 'describe-no-warranty)
  64
  65     ;; This does not fit the pattern, but it is natural given the C-\ command.
  66     (define-key map "\C-\\" 'describe-input-method)
  67
  68     (define-key map "C" 'describe-coding-system)
  69     (define-key map "F" 'Info-goto-emacs-command-node)
  70     (define-key map "I" 'describe-input-method)
  71     (define-key map "K" 'Info-goto-emacs-key-command-node)
  72     (define-key map "L" 'describe-language-environment)
  73     (define-key map "S" 'info-lookup-symbol)
  74
  75     (define-key map "a" 'apropos-command)
  76     (define-key map "b" 'describe-bindings)
  77     (define-key map "c" 'describe-key-briefly)
  78     (define-key map "d" 'apropos-documentation)
  79     (define-key map "e" 'view-echo-area-messages)
  80     (define-key map "f" 'describe-function)
  81     (define-key map "g" 'describe-gnu-project)
  82     (define-key map "h" 'view-hello-file)
  83
  84     (define-key map "i" 'info)
  85     (define-key map "4i" 'info-other-window)
  86
  87     (define-key map "k" 'describe-key)
  88     (define-key map "l" 'view-lossage)
  89     (define-key map "m" 'describe-mode)
  90     (define-key map "n" 'view-emacs-news)
  91     (define-key map "p" 'finder-by-keyword)
  92     (define-key map "P" 'describe-package)
  93     (define-key map "r" 'info-emacs-manual)
  94     (define-key map "s" 'describe-syntax)
  95     (define-key map "t" 'help-with-tutorial)
  96     (define-key map "w" 'where-is)
  97     (define-key map "v" 'describe-variable)
  98     (define-key map "q" 'help-quit)
  99     map)
 100   "Keymap for characters following the Help key.")
 101
 102 (define-key global-map (char-to-string help-char) 'help-command)
 103 (define-key global-map [help] 'help-command)
 104 (define-key global-map [f1] 'help-command)
 105 (fset 'help-command help-map)
 106
 107 ;; insert-button makes the action nil if it is not store somewhere
 108 (defvar help-button-cache nil)
 109
 110 \f
 111 ;; `with-help-window' is a wrapper for `with-temp-buffer-window'
 112 ;; providing the following additional twists:
 113
 114 ;; (1) It puts the buffer in `help-mode' (via `help-mode-setup') and
 115 ;;     adds cross references (via `help-mode-finish').
 116
 117 ;; (2) It issues a message telling how to scroll and quit the help
 118 ;;     window (via `help-window-setup').
 119
 120 ;; (3) An option (customizable via `help-window-select') to select the
 121 ;;     help window automatically.
 122
 123 ;; (4) A marker (`help-window-point-marker') to move point in the help
 124 ;;     window to an arbitrary buffer position.
 125 (defmacro with-help-window (buffer-name &rest body)
 126   "Display buffer named BUFFER-NAME in a help window.
 127 Evaluate the forms in BODY with standard output bound to a buffer
 128 called BUFFER-NAME (creating it if it does not exist), put that
 129 buffer in `help-mode', display the buffer in a window (see
 130 `with-temp-buffer-window' for details) and issue a message how to
 131 deal with that \"help\" window when it's no more needed.  Select
 132 the help window if the current value of the user option
 133 `help-window-select' says so.  Return last value in BODY."
 134   (declare (indent 1) (debug t))
 135   `(progn
 136      ;; Make `help-window-point-marker' point nowhere.  The only place
 137      ;; where this should be set to a buffer position is within BODY.
 138      (set-marker help-window-point-marker nil)
 139      (let ((temp-buffer-window-setup-hook
 140             (cons 'help-mode-setup temp-buffer-window-setup-hook))
 141            (temp-buffer-window-show-hook
 142             (cons 'help-mode-finish temp-buffer-window-show-hook)))
 143        (with-temp-buffer-window
 144         ,buffer-name nil 'help-window-setup (progn ,@body)))))
 145
 146 (defun help-quit ()
 147   "Just exit from the Help command's command loop."
 148   (interactive)
 149   nil)
 150
 151 (defvar help-return-method nil
 152   "What to do to \"exit\" the help buffer.
 153 This is a list
 154  (WINDOW . t)              delete the selected window (and possibly its frame,
 155                            see `quit-window'), go to WINDOW.
 156  (WINDOW . quit-window)    do quit-window, then select WINDOW.
 157  (WINDOW BUF START POINT)  display BUF at START, POINT, then select WINDOW.")
 158
 159 (define-obsolete-function-alias 'print-help-return-message 'help-print-return-message "23.2")
 160 (defun help-print-return-message (&optional function)
 161   "Display or return message saying how to restore windows after help command.
 162 This function assumes that `standard-output' is the help buffer.
 163 It computes a message, and applies the optional argument FUNCTION to it.
 164 If FUNCTION is nil, it applies `message', thus displaying the message.
 165 In addition, this function sets up `help-return-method', which see, that
 166 specifies what to do when the user exits the help buffer.
 167
 168 Do not call this in the scope of `with-help-window'."
 169   (and (not (get-buffer-window standard-output))
 170        (let ((first-message
 171               (cond ((or
 172                       pop-up-frames
 173                       (special-display-p (buffer-name standard-output)))
 174                      (setq help-return-method (cons (selected-window) t))
 175                      ;; If the help output buffer is a special display buffer,
 176                      ;; don't say anything about how to get rid of it.
 177                      ;; First of all, the user will do that with the window
 178                      ;; manager, not with Emacs.
 179                      ;; Secondly, the buffer has not been displayed yet,
 180                      ;; so we don't know whether its frame will be selected.
 181                      nil)
 182                     ((not (one-window-p t))
 183                      (setq help-return-method
 184                            (cons (selected-window) 'quit-window))
 185                      "Type \\[display-buffer] RET to restore the other window.")
 186                     (pop-up-windows
 187                      (setq help-return-method (cons (selected-window) t))
 188                      "Type \\[delete-other-windows] to remove help window.")
 189                     (t
 190                      (setq help-return-method
 191                            (list (selected-window) (window-buffer)
 192                                  (window-start) (window-point)))
 193                      "Type \\[switch-to-buffer] RET to remove help window."))))
 194          (funcall (or function 'message)
 195                   (concat
 196                    (if first-message
 197                        (substitute-command-keys first-message))
 198                    (if first-message "  ")
 199                    ;; If the help buffer will go in a separate frame,
 200                    ;; it's no use mentioning a command to scroll, so don't.
 201                    (if (or pop-up-windows
 202                            (special-display-p (buffer-name standard-output)))
 203                        nil
 204                      (if (same-window-p (buffer-name standard-output))
 205                          ;; Say how to scroll this window.
 206                          (substitute-command-keys
 207                           "\\[scroll-up] to scroll the help.")
 208                        ;; Say how to scroll some other window.
 209                        (substitute-command-keys
 210                         "\\[scroll-other-window] to scroll the help."))))))))
 211
 212 ;; So keyboard macro definitions are documented correctly
 213 (fset 'defining-kbd-macro (symbol-function 'start-kbd-macro))
 214
 215 (defalias 'help 'help-for-help-internal)
 216 ;; find-function can find this.
 217 (defalias 'help-for-help 'help-for-help-internal)
 218 ;; It can't find this, but nobody will look.
 219 (make-help-screen help-for-help-internal
 220   (purecopy "Type a help option: [abcCdefFgiIkKlLmnprstvw.] C-[cdefmnoptw] or ?")
 221   ;; Don't purecopy this one, because it's not evaluated (it's
 222   ;; directly used as a docstring in a function definition, so it'll
 223   ;; be moved to the DOC file anyway: no need for purecopying it).
 224   "You have typed %THIS-KEY%, the help character.  Type a Help option:
 225 \(Use SPC or DEL to scroll through this text.  Type \\<help-map>\\[help-quit] to exit the Help command.)
 226
 227 a PATTERN   Show commands whose name matches the PATTERN (a list of words
 228               or a regexp).  See also the `apropos' command.
 229 b           Display all key bindings.
 230 c KEYS      Display the command name run by the given key sequence.
 231 C CODING    Describe the given coding system, or RET for current ones.
 232 d PATTERN   Show a list of functions, variables, and other items whose
 233               documentation matches the PATTERN (a list of words or a regexp).
 234 e           Go to the *Messages* buffer which logs echo-area messages.
 235 f FUNCTION  Display documentation for the given function.
 236 F COMMAND   Show the on-line manual's section that describes the command.
 237 g           Display information about the GNU project.
 238 h           Display the HELLO file which illustrates various scripts.
 239 i           Start the Info documentation reader: read on-line manuals.
 240 I METHOD    Describe a specific input method, or RET for current.
 241 k KEYS      Display the full documentation for the key sequence.
 242 K KEYS      Show the on-line manual's section for the command bound to KEYS.
 243 l           Show last 300 input keystrokes (lossage).
 244 L LANG-ENV  Describes a specific language environment, or RET for current.
 245 m           Display documentation of current minor modes and current major mode,
 246               including their special commands.
 247 n           Display news of recent Emacs changes.
 248 p TOPIC     Find packages matching a given topic keyword.
 249 P PACKAGE   Describe the given Emacs Lisp package.
 250 r           Display the Emacs manual in Info mode.
 251 s           Display contents of current syntax table, plus explanations.
 252 S SYMBOL    Show the section for the given symbol in the on-line manual
 253               for the programming language used in this buffer.
 254 t           Start the Emacs learn-by-doing tutorial.
 255 v VARIABLE  Display the given variable's documentation and value.
 256 w COMMAND   Display which keystrokes invoke the given command (where-is).
 257 .           Display any available local help at point in the echo area.
 258
 259 C-a         Information about Emacs.
 260 C-c         Emacs copying permission (GNU General Public License).
 261 C-d         Instructions for debugging GNU Emacs.
 262 C-e         External packages and information about Emacs.
 263 C-f         Emacs FAQ.
 264 C-m         How to order printed Emacs manuals.
 265 C-n         News of recent Emacs changes.
 266 C-o         Emacs ordering and distribution information.
 267 C-p         Info about known Emacs problems.
 268 C-t         Emacs TODO list.
 269 C-w         Information on absence of warranty for GNU Emacs."
 270   help-map)
 271
 272 \f
 273
 274 (defun function-called-at-point ()
 275   "Return a function around point or else called by the list containing point.
 276 If that doesn't give a function, return nil."
 277   (with-syntax-table emacs-lisp-mode-syntax-table
 278     (or (condition-case ()
 279             (save-excursion
 280               (or (not (zerop (skip-syntax-backward "_w")))
 281                   (eq (char-syntax (following-char)) ?w)
 282                   (eq (char-syntax (following-char)) ?_)
 283                   (forward-sexp -1))
 284               (skip-chars-forward "'")
 285               (let ((obj (read (current-buffer))))
 286                 (and (symbolp obj) (fboundp obj) obj)))
 287           (error nil))
 288         (condition-case ()
 289             (save-excursion
 290               (save-restriction
 291                 (narrow-to-region (max (point-min)
 292                                        (- (point) 1000)) (point-max))
 293                 ;; Move up to surrounding paren, then after the open.
 294                 (backward-up-list 1)
 295                 (forward-char 1)
 296                 ;; If there is space here, this is probably something
 297                 ;; other than a real Lisp function call, so ignore it.
 298                 (if (looking-at "[ \t]")
 299                     (error "Probably not a Lisp function call"))
 300                 (let ((obj (read (current-buffer))))
 301                   (and (symbolp obj) (fboundp obj) obj))))
 302           (error nil))
 303         (let* ((str (find-tag-default))
 304                (sym (if str (intern-soft str))))
 305           (if (and sym (fboundp sym))
 306               sym
 307             (save-match-data
 308               (when (and str (string-match "\\`\\W*\\(.*?\\)\\W*\\'" str))
 309                 (setq sym (intern-soft (match-string 1 str)))
 310                 (and (fboundp sym) sym))))))))
 311
 312 \f
 313 ;;; `User' help functions
 314
 315 (defun view-help-file (file &optional dir)
 316   (view-file (expand-file-name file (or dir data-directory)))
 317   (goto-address-mode 1)
 318   (goto-char (point-min)))
 319
 320 (defun describe-distribution ()
 321   "Display info on how to obtain the latest version of GNU Emacs."
 322   (interactive)
 323   (view-help-file "DISTRIB"))
 324
 325 (defun describe-copying ()
 326   "Display info on how you may redistribute copies of GNU Emacs."
 327   (interactive)
 328   (view-help-file "COPYING"))
 329
 330 ;; Maybe this command should just be removed.
 331 (defun describe-gnu-project ()
 332   "Browse online information on the GNU project."
 333   (interactive)
 334   (browse-url "http://www.gnu.org/gnu/thegnuproject.html"))
 335
 336 (define-obsolete-function-alias 'describe-project 'describe-gnu-project "22.2")
 337
 338 (defun describe-no-warranty ()
 339   "Display info on all the kinds of warranty Emacs does NOT have."
 340   (interactive)
 341   (describe-copying)
 342   (let (case-fold-search)
 343     (search-forward "Disclaimer of Warranty")
 344     (forward-line 0)
 345     (recenter 0)))
 346
 347 (defun describe-prefix-bindings ()
 348   "Describe the bindings of the prefix used to reach this command.
 349 The prefix described consists of all but the last event
 350 of the key sequence that ran this command."
 351   (interactive)
 352   (let ((key (this-command-keys)))
 353     (describe-bindings
 354      (if (stringp key)
 355          (substring key 0 (1- (length key)))
 356        (let ((prefix (make-vector (1- (length key)) nil))
 357              (i 0))
 358          (while (< i (length prefix))
 359            (aset prefix i (aref key i))
 360            (setq i (1+ i)))
 361          prefix)))))
 362 ;; Make C-h after a prefix, when not specifically bound,
 363 ;; run describe-prefix-bindings.
 364 (setq prefix-help-command 'describe-prefix-bindings)
 365
 366 (defun view-emacs-news (&optional version)
 367   "Display info on recent changes to Emacs.
 368 With argument, display info only for the selected version."
 369   (interactive "P")
 370   (unless version
 371     (setq version emacs-major-version))
 372   (when (consp version)
 373     (let* ((all-versions
 374             (let (res)
 375               (mapc
 376                (lambda (file)
 377                  (with-temp-buffer
 378                    (insert-file-contents
 379                     (expand-file-name file data-directory))
 380                    (while (re-search-forward
 381                            (if (member file '("NEWS.18" "NEWS.1-17"))
 382                                "Changes in \\(?:Emacs\\|version\\)?[ \t]*\\([0-9]+\\(?:\\.[0-9]+\\)?\\)"
 383                              "^\* [^0-9\n]*\\([0-9]+\\.[0-9]+\\)") nil t)
 384                      (setq res (cons (match-string-no-properties 1) res)))))
 385                (cons "NEWS"
 386                      (directory-files data-directory nil
 387                                       "^NEWS\\.[0-9][-0-9]*$" nil)))
 388               (sort (delete-dups res) (lambda (a b) (string< b a)))))
 389            (current (car all-versions)))
 390       (setq version (completing-read
 391                      (format "Read NEWS for the version (default %s): " current)
 392                      all-versions nil nil nil nil current))
 393       (if (integerp (string-to-number version))
 394           (setq version (string-to-number version))
 395         (unless (or (member version all-versions)
 396                     (<= (string-to-number version) (string-to-number current)))
 397           (error "No news about version %s" version)))))
 398   (when (integerp version)
 399     (cond ((<= version 12)
 400            (setq version (format "1.%d" version)))
 401           ((<= version 18)
 402            (setq version (format "%d" version)))
 403           ((> version emacs-major-version)
 404            (error "No news about Emacs %d (yet)" version))))
 405   (let* ((vn (if (stringp version)
 406                  (string-to-number version)
 407                version))
 408          (file (cond
 409                 ((>= vn emacs-major-version) "NEWS")
 410                 ((< vn 18) "NEWS.1-17")
 411                 (t (format "NEWS.%d" vn))))
 412          res)
 413     (view-file (expand-file-name file data-directory))
 414     (widen)
 415     (goto-char (point-min))
 416     (when (stringp version)
 417       (when (re-search-forward
 418              (concat (if (< vn 19)
 419                          "Changes in Emacs[ \t]*"
 420                        "^\* [^0-9\n]*") version "$")
 421              nil t)
 422         (beginning-of-line)
 423         (narrow-to-region
 424          (point)
 425          (save-excursion
 426            (while (and (setq res
 427                              (re-search-forward
 428                               (if (< vn 19)
 429                                   "Changes in \\(?:Emacs\\|version\\)?[ \t]*\\([0-9]+\\(?:\\.[0-9]+\\)?\\)"
 430                                 "^\* [^0-9\n]*\\([0-9]+\\.[0-9]+\\)") nil t))
 431                        (equal (match-string-no-properties 1) version)))
 432            (or res (goto-char (point-max)))
 433            (beginning-of-line)
 434            (point)))))))
 435
 436 (defun view-emacs-todo (&optional _arg)
 437   "Display the Emacs TODO list."
 438   (interactive "P")
 439   (view-help-file "TODO"))
 440
 441 (define-obsolete-function-alias 'view-todo 'view-emacs-todo "22.2")
 442
 443
 444 (defun view-echo-area-messages ()
 445   "View the log of recent echo-area messages: the `*Messages*' buffer.
 446 The number of messages retained in that buffer
 447 is specified by the variable `message-log-max'."
 448   (interactive)
 449   (with-current-buffer (messages-buffer)
 450     (goto-char (point-max))
 451     (display-buffer (current-buffer))))
 452
 453 (defun view-order-manuals ()
 454   "Display information on how to buy printed copies of Emacs manuals."
 455   (interactive)
 456 ;;  (view-help-file "ORDERS")
 457   (info "(emacs)Printed Books"))
 458
 459 (defun view-emacs-FAQ ()
 460   "Display the Emacs Frequently Asked Questions (FAQ) file."
 461   (interactive)
 462   ;; (find-file-read-only (expand-file-name "FAQ" data-directory))
 463   (info "(efaq)"))
 464
 465 (defun view-emacs-problems ()
 466   "Display info on known problems with Emacs and possible workarounds."
 467   (interactive)
 468   (view-help-file "PROBLEMS"))
 469
 470 (defun view-emacs-debugging ()
 471   "Display info on how to debug Emacs problems."
 472   (interactive)
 473   (view-help-file "DEBUG"))
 474
 475 ;; This used to visit MORE.STUFF; maybe it should just be removed.
 476 (defun view-external-packages ()
 477   "Display info on where to get more Emacs packages."
 478   (interactive)
 479   (info "(efaq)Packages that do not come with Emacs"))
 480
 481 (defun view-lossage ()
 482   "Display last 300 input keystrokes.
 483
 484 To record all your input, use `open-dribble-file'."
 485   (interactive)
 486   (help-setup-xref (list #'view-lossage)
 487                    (called-interactively-p 'interactive))
 488   (with-help-window (help-buffer)
 489     (princ (mapconcat (lambda (key)
 490                         (if (or (integerp key) (symbolp key) (listp key))
 491                             (single-key-description key)
 492                           (prin1-to-string key nil)))
 493                       (recent-keys)
 494                       " "))
 495     (with-current-buffer standard-output
 496       (goto-char (point-min))
 497       (while (progn (move-to-column 50) (not (eobp)))
 498         (when (search-forward " " nil t)
 499           (delete-char -1))
 500         (insert "\n"))
 501       ;; jidanni wants to see the last keystrokes immediately.
 502       (set-marker help-window-point-marker (point)))))
 503
 504 \f
 505 ;; Key bindings
 506
 507 (defun describe-bindings (&optional prefix buffer)
 508   "Display a buffer showing a list of all defined keys, and their definitions.
 509 The keys are displayed in order of precedence.
 510
 511 The optional argument PREFIX, if non-nil, should be a key sequence;
 512 then we display only bindings that start with that prefix.
 513 The optional argument BUFFER specifies which buffer's bindings
 514 to display (default, the current buffer).  BUFFER can be a buffer
 515 or a buffer name."
 516   (interactive)
 517   (or buffer (setq buffer (current-buffer)))
 518   (help-setup-xref (list #'describe-bindings prefix buffer)
 519                    (called-interactively-p 'interactive))
 520   (with-help-window (help-buffer)
 521     ;; Be aware that `describe-buffer-bindings' puts its output into
 522     ;; the current buffer.
 523     (with-current-buffer (help-buffer)
 524       (describe-buffer-bindings buffer prefix))))
 525
 526 ;; This function used to be in keymap.c.
 527 (defun describe-bindings-internal (&optional menus prefix)
 528   "Show a list of all defined keys, and their definitions.
 529 We put that list in a buffer, and display the buffer.
 530
 531 The optional argument MENUS, if non-nil, says to mention menu bindings.
 532 \(Ordinarily these are omitted from the output.)
 533 The optional argument PREFIX, if non-nil, should be a key sequence;
 534 then we display only bindings that start with that prefix."
 535   (declare (obsolete describe-buffer-bindings "24.4"))
 536   (let ((buf (current-buffer)))
 537     (with-help-window (help-buffer)
 538       ;; Be aware that `describe-buffer-bindings' puts its output into
 539       ;; the current buffer.
 540       (with-current-buffer (help-buffer)
 541         (describe-buffer-bindings buf prefix menus)))))
 542
 543 (defun where-is (definition &optional insert)
 544   "Print message listing key sequences that invoke the command DEFINITION.
 545 Argument is a command definition, usually a symbol with a function definition.
 546 If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
 547   (interactive
 548    (let ((fn (function-called-at-point))
 549          (enable-recursive-minibuffers t)
 550          val)
 551      (setq val (completing-read
 552                 (if fn
 553                     (format "Where is command (default %s): " fn)
 554                   "Where is command: ")
 555                 obarray 'commandp t nil nil
 556                 (and fn (symbol-name fn))))
 557      (list (unless (equal val "") (intern val))
 558            current-prefix-arg)))
 559   (unless definition (error "No command"))
 560   (let ((func (indirect-function definition))
 561         (defs nil)
 562         (standard-output (if insert (current-buffer) standard-output)))
 563     ;; In DEFS, find all symbols that are aliases for DEFINITION.
 564     (mapatoms (lambda (symbol)
 565                 (and (fboundp symbol)
 566                      (not (eq symbol definition))
 567                      (eq func (condition-case ()
 568                                   (indirect-function symbol)
 569                                 (error symbol)))
 570                      (push symbol defs))))
 571     ;; Look at all the symbols--first DEFINITION,
 572     ;; then its aliases.
 573     (dolist (symbol (cons definition defs))
 574       (let* ((remapped (command-remapping symbol))
 575              (keys (where-is-internal
 576                     symbol overriding-local-map nil nil remapped))
 577              (keys (mapconcat 'key-description keys ", "))
 578              string)
 579         (setq string
 580               (if insert
 581                   (if (> (length keys) 0)
 582                       (if remapped
 583                           (format "%s (%s) (remapped from %s)"
 584                                   keys remapped symbol)
 585                         (format "%s (%s)" keys symbol))
 586                     (format "M-x %s RET" symbol))
 587                 (if (> (length keys) 0)
 588                     (if remapped
 589                         (format "%s is remapped to %s which is on %s"
 590                                 symbol remapped keys)
 591                       (format "%s is on %s" symbol keys))
 592                   ;; If this is the command the user asked about,
 593                   ;; and it is not on any key, say so.
 594                   ;; For other symbols, its aliases, say nothing
 595                   ;; about them unless they are on keys.
 596                   (if (eq symbol definition)
 597                       (format "%s is not on any key" symbol)))))
 598         (when string
 599           (unless (eq symbol definition)
 600             (princ ";\n its alias "))
 601           (princ string)))))
 602   nil)
 603
 604 (defun help-key-description (key untranslated)
 605   (let ((string (key-description key)))
 606     (if (or (not untranslated)
 607             (and (eq (aref untranslated 0) ?\e) (not (eq (aref key 0) ?\e))))
 608         string
 609       (let ((otherstring (key-description untranslated)))
 610         (if (equal string otherstring)
 611             string
 612           (format "%s (translated from %s)" string otherstring))))))
 613
 614 (defun describe-key-briefly (&optional key insert untranslated)
 615   "Print the name of the function KEY invokes.  KEY is a string.
 616 If INSERT (the prefix arg) is non-nil, insert the message in the buffer.
 617 If non-nil, UNTRANSLATED is a vector of the untranslated events.
 618 It can also be a number in which case the untranslated events from
 619 the last key hit are used.
 620
 621 If KEY is a menu item or a tool-bar button that is disabled, this command
 622 temporarily enables it to allow getting help on disabled items and buttons."
 623   (interactive
 624    (let ((enable-disabled-menus-and-buttons t)
 625          (cursor-in-echo-area t)
 626          saved-yank-menu)
 627      (unwind-protect
 628          (let (key)
 629            ;; If yank-menu is empty, populate it temporarily, so that
 630            ;; "Select and Paste" menu can generate a complete event.
 631            (when (null (cdr yank-menu))
 632              (setq saved-yank-menu (copy-sequence yank-menu))
 633              (menu-bar-update-yank-menu "(any string)" nil))
 634            (setq key (read-key-sequence "Describe key (or click or menu item): "))
 635            ;; Clear the echo area message (Bug#7014).
 636            (message nil)
 637            ;; If KEY is a down-event, read and discard the
 638            ;; corresponding up-event.  Note that there are also
 639            ;; down-events on scroll bars and mode lines: the actual
 640            ;; event then is in the second element of the vector.
 641            (and (vectorp key)
 642                 (let ((last-idx (1- (length key))))
 643                   (and (eventp (aref key last-idx))
 644                        (memq 'down (event-modifiers (aref key last-idx)))))
 645                 (read-event))
 646            (list
 647             key
 648             (if current-prefix-arg (prefix-numeric-value current-prefix-arg))
 649             1))
 650        ;; Put yank-menu back as it was, if we changed it.
 651        (when saved-yank-menu
 652          (setq yank-menu (copy-sequence saved-yank-menu))
 653          (fset 'yank-menu (cons 'keymap yank-menu))))))
 654   (if (numberp untranslated)
 655       (setq untranslated (this-single-command-raw-keys)))
 656   (let* ((event (if (and (symbolp (aref key 0))
 657                          (> (length key) 1)
 658                          (consp (aref key 1)))
 659                     (aref key 1)
 660                   (aref key 0)))
 661          (modifiers (event-modifiers event))
 662          (standard-output (if insert (current-buffer) standard-output))
 663          (mouse-msg (if (or (memq 'click modifiers) (memq 'down modifiers)
 664                             (memq 'drag modifiers)) " at that spot" ""))
 665          (defn (key-binding key t))
 666          key-desc)
 667     ;; Handle the case where we faked an entry in "Select and Paste" menu.
 668     (if (and (eq defn nil)
 669              (stringp (aref key (1- (length key))))
 670              (eq (key-binding (substring key 0 -1)) 'yank-menu))
 671         (setq defn 'menu-bar-select-yank))
 672     ;; Don't bother user with strings from (e.g.) the select-paste menu.
 673     (if (stringp (aref key (1- (length key))))
 674         (aset key (1- (length key)) "(any string)"))
 675     (if (and (> (length untranslated) 0)
 676              (stringp (aref untranslated (1- (length untranslated)))))
 677         (aset untranslated (1- (length untranslated)) "(any string)"))
 678     ;; Now describe the key, perhaps as changed.
 679     (setq key-desc (help-key-description key untranslated))
 680     (if (or (null defn) (integerp defn) (equal defn 'undefined))
 681         (princ (format "%s%s is undefined" key-desc mouse-msg))
 682       (princ (format "%s%s runs the command %S" key-desc mouse-msg defn)))))
 683
 684 (defun help--key-binding-keymap (key &optional accept-default no-remap position)
 685   "Return a keymap holding a binding for KEY within current keymaps.
 686 The effect of the arguments KEY, ACCEPT-DEFAULT, NO-REMAP and
 687 POSITION is as documented in the function `key-binding'."
 688   (let* ((active-maps (current-active-maps t position))
 689          map found)
 690     ;; We loop over active maps like key-binding does.
 691     (while (and
 692             (not found)
 693             (setq map (pop active-maps)))
 694       (setq found (lookup-key map key accept-default))
 695       (when (integerp found)
 696         ;; The first `found' characters of KEY were found but not the
 697         ;; whole sequence.
 698         (setq found nil)))
 699     (when found
 700       (if (and (symbolp found)
 701                (not no-remap)
 702                (command-remapping found))
 703           ;; The user might want to know in which map the binding is
 704           ;; found, or in which map the remapping is found.  The
 705           ;; default is to show the latter.
 706           (help--key-binding-keymap (vector 'remap found))
 707         map))))
 708
 709 (defun help--binding-locus (key position)
 710   "Describe in which keymap KEY is defined.
 711 Return a symbol pointing to that keymap if one exists ; otherwise
 712 return nil."
 713   (let ((map (help--key-binding-keymap key t nil position)))
 714     (when map
 715       (catch 'found
 716         (let ((advertised-syms (nconc
 717                                 (list 'overriding-terminal-local-map
 718                                       'overriding-local-map)
 719                                 (delq nil
 720                                       (mapcar
 721                                        (lambda (mode-and-map)
 722                                          (let ((mode (car mode-and-map)))
 723                                            (when (symbol-value mode)
 724                                              (intern-soft
 725                                               (format "%s-map" mode)))))
 726                                        minor-mode-map-alist))
 727                                 (list 'global-map
 728                                       (intern-soft (format "%s-map" major-mode)))))
 729               found)
 730           ;; Look into these advertised symbols first.
 731           (dolist (sym advertised-syms)
 732             (when (and
 733                    (boundp sym)
 734                    (eq map (symbol-value sym)))
 735               (throw 'found sym)))
 736           ;; Only look in other symbols otherwise.
 737           (mapatoms
 738            (lambda (x)
 739              (when (and (boundp x)
 740                         ;; Avoid let-bound symbols.
 741                         (special-variable-p x)
 742                         (eq (symbol-value x) map))
 743                (throw 'found x))))
 744           nil)))))
 745
 746 (defun describe-key (&optional key untranslated up-event)
 747   "Display documentation of the function invoked by KEY.
 748 KEY can be any kind of a key sequence; it can include keyboard events,
 749 mouse events, and/or menu events.  When calling from a program,
 750 pass KEY as a string or a vector.
 751
 752 If non-nil, UNTRANSLATED is a vector of the corresponding untranslated events.
 753 It can also be a number, in which case the untranslated events from
 754 the last key sequence entered are used.
 755 UP-EVENT is the up-event that was discarded by reading KEY, or nil.
 756
 757 If KEY is a menu item or a tool-bar button that is disabled, this command
 758 temporarily enables it to allow getting help on disabled items and buttons."
 759   (interactive
 760    (let ((enable-disabled-menus-and-buttons t)
 761          (cursor-in-echo-area t)
 762          saved-yank-menu)
 763      (unwind-protect
 764          (let (key)
 765            ;; If yank-menu is empty, populate it temporarily, so that
 766            ;; "Select and Paste" menu can generate a complete event.
 767            (when (null (cdr yank-menu))
 768              (setq saved-yank-menu (copy-sequence yank-menu))
 769              (menu-bar-update-yank-menu "(any string)" nil))
 770            (setq key (read-key-sequence "Describe key (or click or menu item): "))
 771            (list
 772             key
 773             (prefix-numeric-value current-prefix-arg)
 774             ;; If KEY is a down-event, read and include the
 775             ;; corresponding up-event.  Note that there are also
 776             ;; down-events on scroll bars and mode lines: the actual
 777             ;; event then is in the second element of the vector.
 778             (and (vectorp key)
 779                  (let ((last-idx (1- (length key))))
 780                    (and (eventp (aref key last-idx))
 781                         (memq 'down (event-modifiers (aref key last-idx)))))
 782                  (or (and (eventp (aref key 0))
 783                           (memq 'down (event-modifiers (aref key 0)))
 784                           ;; However, for the C-down-mouse-2 popup
 785                           ;; menu, there is no subsequent up-event.  In
 786                           ;; this case, the up-event is the next
 787                           ;; element in the supplied vector.
 788                           (= (length key) 1))
 789                      (and (> (length key) 1)
 790                           (eventp (aref key 1))
 791                           (memq 'down (event-modifiers (aref key 1)))))
 792                  (read-event))))
 793        ;; Put yank-menu back as it was, if we changed it.
 794        (when saved-yank-menu
 795          (setq yank-menu (copy-sequence saved-yank-menu))
 796          (fset 'yank-menu (cons 'keymap yank-menu))))))
 797   (if (numberp untranslated)
 798       (setq untranslated (this-single-command-raw-keys)))
 799   (let* ((event (aref key (if (and (symbolp (aref key 0))
 800                                    (> (length key) 1)
 801                                    (consp (aref key 1)))
 802                               1
 803                             0)))
 804          (modifiers (event-modifiers event))
 805          (mouse-msg (if (or (memq 'click modifiers) (memq 'down modifiers)
 806                             (memq 'drag modifiers)) " at that spot" ""))
 807          (defn (key-binding key t))
 808          key-locus key-locus-up key-locus-up-tricky
 809          defn-up defn-up-tricky ev-type
 810          mouse-1-remapped mouse-1-tricky)
 811
 812     ;; Handle the case where we faked an entry in "Select and Paste" menu.
 813     (when (and (eq defn nil)
 814                (stringp (aref key (1- (length key))))
 815                (eq (key-binding (substring key 0 -1)) 'yank-menu))
 816       (setq defn 'menu-bar-select-yank))
 817     (if (or (null defn) (integerp defn) (equal defn 'undefined))
 818         (message "%s%s is undefined"
 819                  (help-key-description key untranslated) mouse-msg)
 820       (help-setup-xref (list #'describe-function defn)
 821                        (called-interactively-p 'interactive))
 822       ;; Don't bother user with strings from (e.g.) the select-paste menu.
 823       (when (stringp (aref key (1- (length key))))
 824         (aset key (1- (length key)) "(any string)"))
 825       (when (and untranslated
 826                  (stringp (aref untranslated (1- (length untranslated)))))
 827         (aset untranslated (1- (length untranslated))
 828               "(any string)"))
 829       ;; Need to do this before erasing *Help* buffer in case event
 830       ;; is a mouse click in an existing *Help* buffer.
 831       (when up-event
 832         (setq ev-type (event-basic-type up-event))
 833         (let ((sequence (vector up-event)))
 834           (when (and (eq ev-type 'mouse-1)
 835                      mouse-1-click-follows-link
 836                      (not (eq mouse-1-click-follows-link 'double))
 837                      (setq mouse-1-remapped
 838                            (mouse-on-link-p (event-start up-event))))
 839             (setq mouse-1-tricky (and (integerp mouse-1-click-follows-link)
 840                                       (> mouse-1-click-follows-link 0)))
 841             (cond ((stringp mouse-1-remapped)
 842                    (setq sequence mouse-1-remapped))
 843                   ((vectorp mouse-1-remapped)
 844                    (setcar up-event (elt mouse-1-remapped 0)))
 845                   (t (setcar up-event 'mouse-2))))
 846           (setq defn-up (key-binding sequence nil nil (event-start up-event)))
 847           (setq key-locus-up (help--binding-locus sequence (event-start up-event)))
 848           (when mouse-1-tricky
 849             (setq sequence (vector up-event))
 850             (aset sequence 0 'mouse-1)
 851             (setq defn-up-tricky (key-binding sequence nil nil (event-start up-event)))
 852             (setq key-locus-up-tricky (help--binding-locus sequence (event-start up-event))))))
 853       (setq key-locus (help--binding-locus key (event-start event)))
 854       (with-help-window (help-buffer)
 855         (princ (help-key-description key untranslated))
 856         (princ (format "%s runs the command %S%s, which is "
 857                        mouse-msg defn (if key-locus
 858                                           (format " (found in %s)" key-locus)
 859                                         "")))
 860         (describe-function-1 defn)
 861         (when up-event
 862           (unless (or (null defn-up)
 863                       (integerp defn-up)
 864                       (equal defn-up 'undefined))
 865             (princ (format "
 866
 867 ----------------- up-event %s----------------
 868
 869 %s%s%s runs the command %S%s, which is "
 870                            (if mouse-1-tricky "(short click) " "")
 871                            (key-description (vector up-event))
 872                            mouse-msg
 873                            (if mouse-1-remapped
 874                                " is remapped to <mouse-2>, which" "")
 875                            defn-up (if key-locus-up
 876                                        (format " (found in %s)" key-locus-up)
 877                                      "")))
 878             (describe-function-1 defn-up))
 879           (unless (or (null defn-up-tricky)
 880                       (integerp defn-up-tricky)
 881                       (eq defn-up-tricky 'undefined))
 882             (princ (format "
 883
 884 ----------------- up-event (long click) ----------------
 885
 886 Pressing <%S>%s for longer than %d milli-seconds
 887 runs the command %S%s, which is "
 888                            ev-type mouse-msg
 889                            mouse-1-click-follows-link
 890                            defn-up-tricky (if key-locus-up-tricky
 891                                               (format " (found in %s)" key-locus-up-tricky)
 892                                             "")))
 893             (describe-function-1 defn-up-tricky)))))))
 894 \f
 895 (defun describe-mode (&optional buffer)
 896   "Display documentation of current major mode and minor modes.
 897 A brief summary of the minor modes comes first, followed by the
 898 major mode description.  This is followed by detailed
 899 descriptions of the minor modes, each on a separate page.
 900
 901 For this to work correctly for a minor mode, the mode's indicator
 902 variable \(listed in `minor-mode-alist') must also be a function
 903 whose documentation describes the minor mode.
 904
 905 If called from Lisp with a non-nil BUFFER argument, display
 906 documentation for the major and minor modes of that buffer."
 907   (interactive "@")
 908   (unless buffer (setq buffer (current-buffer)))
 909   (help-setup-xref (list #'describe-mode buffer)
 910                    (called-interactively-p 'interactive))
 911   ;; For the sake of help-do-xref and help-xref-go-back,
 912   ;; don't switch buffers before calling `help-buffer'.
 913   (with-help-window (help-buffer)
 914     (with-current-buffer buffer
 915       (let (minor-modes)
 916         ;; Older packages do not register in minor-mode-list but only in
 917         ;; minor-mode-alist.
 918         (dolist (x minor-mode-alist)
 919           (setq x (car x))
 920           (unless (memq x minor-mode-list)
 921             (push x minor-mode-list)))
 922         ;; Find enabled minor mode we will want to mention.
 923         (dolist (mode minor-mode-list)
 924           ;; Document a minor mode if it is listed in minor-mode-alist,
 925           ;; non-nil, and has a function definition.
 926           (let ((fmode (or (get mode :minor-mode-function) mode)))
 927             (and (boundp mode) (symbol-value mode)
 928                  (fboundp fmode)
 929                  (let ((pretty-minor-mode
 930                         (if (string-match "\\(\\(-minor\\)?-mode\\)?\\'"
 931                                           (symbol-name fmode))
 932                             (capitalize
 933                              (substring (symbol-name fmode)
 934                                         0 (match-beginning 0)))
 935                           fmode)))
 936                    (push (list fmode pretty-minor-mode
 937                                (format-mode-line (assq mode minor-mode-alist)))
 938                          minor-modes)))))
 939         (setq minor-modes
 940               (sort minor-modes
 941                     (lambda (a b) (string-lessp (cadr a) (cadr b)))))
 942         (when minor-modes
 943           (princ "Enabled minor modes:\n")
 944           (make-local-variable 'help-button-cache)
 945           (with-current-buffer standard-output
 946             (dolist (mode minor-modes)
 947               (let ((mode-function (nth 0 mode))
 948                     (pretty-minor-mode (nth 1 mode))
 949                     (indicator (nth 2 mode)))
 950                 (add-text-properties 0 (length pretty-minor-mode)
 951                                      '(face bold) pretty-minor-mode)
 952                 (save-excursion
 953                   (goto-char (point-max))
 954                   (princ "\n\f\n")
 955                   (push (point-marker) help-button-cache)
 956                   ;; Document the minor modes fully.
 957                   (insert pretty-minor-mode)
 958                   (princ (format " minor mode (%s):\n"
 959                                  (if (zerop (length indicator))
 960                                      "no indicator"
 961                                    (format "indicator%s"
 962                                            indicator))))
 963                   (princ (documentation mode-function)))
 964                 (insert-button pretty-minor-mode
 965                                'action (car help-button-cache)
 966                                'follow-link t
 967                                'help-echo "mouse-2, RET: show full information")
 968                 (newline)))
 969             (forward-line -1)
 970             (fill-paragraph nil)
 971             (forward-line 1))
 972
 973           (princ "\n(Information about these minor modes follows the major mode info.)\n\n"))
 974         ;; Document the major mode.
 975         (let ((mode mode-name))
 976           (with-current-buffer standard-output
 977             (let ((start (point)))
 978               (insert (format-mode-line mode nil nil buffer))
 979               (add-text-properties start (point) '(face bold)))))
 980         (princ " mode")
 981         (let* ((mode major-mode)
 982                (file-name (find-lisp-object-file-name mode nil)))
 983           (when file-name
 984             (princ (concat " defined in `" (file-name-nondirectory file-name) "'"))
 985             ;; Make a hyperlink to the library.
 986             (with-current-buffer standard-output
 987               (save-excursion
 988                 (re-search-backward "`\\([^`']+\\)'" nil t)
 989                 (help-xref-button 1 'help-function-def mode file-name)))))
 990         (princ ":\n")
 991         (princ (documentation major-mode)))))
 992   ;; For the sake of IELM and maybe others
 993   nil)
 994
 995
 996 (defun describe-minor-mode (minor-mode)
 997   "Display documentation of a minor mode given as MINOR-MODE.
 998 MINOR-MODE can be a minor mode symbol or a minor mode indicator string
 999 appeared on the mode-line."
1000   (interactive (list (completing-read
1001                       "Minor mode: "
1002                               (nconc
1003                                (describe-minor-mode-completion-table-for-symbol)
1004                                (describe-minor-mode-completion-table-for-indicator)
1005                                ))))
1006   (if (symbolp minor-mode)
1007       (setq minor-mode (symbol-name minor-mode)))
1008   (let ((symbols (describe-minor-mode-completion-table-for-symbol))
1009         (indicators (describe-minor-mode-completion-table-for-indicator)))
1010     (cond
1011      ((member minor-mode symbols)
1012       (describe-minor-mode-from-symbol (intern minor-mode)))
1013      ((member minor-mode indicators)
1014       (describe-minor-mode-from-indicator minor-mode))
1015      (t
1016       (error "No such minor mode: %s" minor-mode)))))
1017
1018 ;; symbol
1019 (defun describe-minor-mode-completion-table-for-symbol ()
1020   ;; In order to list up all minor modes, minor-mode-list
1021   ;; is used here instead of minor-mode-alist.
1022   (delq nil (mapcar 'symbol-name minor-mode-list)))
1023
1024 (defun describe-minor-mode-from-symbol (symbol)
1025   "Display documentation of a minor mode given as a symbol, SYMBOL"
1026   (interactive (list (intern (completing-read
1027                               "Minor mode symbol: "
1028                               (describe-minor-mode-completion-table-for-symbol)))))
1029   (if (fboundp symbol)
1030       (describe-function symbol)
1031     (describe-variable symbol)))
1032
1033 ;; indicator
1034 (defun describe-minor-mode-completion-table-for-indicator ()
1035   (delq nil
1036         (mapcar (lambda (x)
1037                   (let ((i (format-mode-line x)))
1038                     ;; remove first space if existed
1039                     (cond
1040                      ((= 0 (length i))
1041                       nil)
1042                      ((eq (aref i 0) ?\s)
1043                       (substring i 1))
1044                      (t
1045                       i))))
1046                 minor-mode-alist)))
1047
1048 (defun describe-minor-mode-from-indicator (indicator)
1049   "Display documentation of a minor mode specified by INDICATOR.
1050 If you call this function interactively, you can give indicator which
1051 is currently activated with completion."
1052   (interactive (list
1053                 (completing-read
1054                  "Minor mode indicator: "
1055                  (describe-minor-mode-completion-table-for-indicator))))
1056   (let ((minor-mode (lookup-minor-mode-from-indicator indicator)))
1057     (if minor-mode
1058         (describe-minor-mode-from-symbol minor-mode)
1059       (error "Cannot find minor mode for `%s'" indicator))))
1060
1061 (defun lookup-minor-mode-from-indicator (indicator)
1062   "Return a minor mode symbol from its indicator on the mode line."
1063   ;; remove first space if existed
1064   (if (and (< 0 (length indicator))
1065            (eq (aref indicator 0) ?\s))
1066       (setq indicator (substring indicator 1)))
1067   (let ((minor-modes minor-mode-alist)
1068         result)
1069     (while minor-modes
1070       (let* ((minor-mode (car (car minor-modes)))
1071              (anindicator (format-mode-line
1072                            (car (cdr (car minor-modes))))))
1073         ;; remove first space if existed
1074         (if (and (stringp anindicator)
1075                  (> (length anindicator) 0)
1076                  (eq (aref anindicator 0) ?\s))
1077             (setq anindicator (substring anindicator 1)))
1078         (if (equal indicator anindicator)
1079             (setq result minor-mode
1080                   minor-modes nil)
1081           (setq minor-modes (cdr minor-modes)))))
1082     result))
1083 \f
1084 ;;; Automatic resizing of temporary buffers.
1085 (defcustom temp-buffer-max-height
1086   (lambda (buffer)
1087     (if (eq (selected-window) (frame-root-window))
1088         (/ (x-display-pixel-height) (frame-char-height) 2)
1089       (/ (- (frame-height) 2) 2)))
1090   "Maximum height of a window displaying a temporary buffer.
1091 This is effective only when Temp Buffer Resize mode is enabled.
1092 The value is the maximum height (in lines) which
1093 `resize-temp-buffer-window' will give to a window displaying a
1094 temporary buffer.  It can also be a function to be called to
1095 choose the height for such a buffer.  It gets one argument, the
1096 buffer, and should return a positive integer.  At the time the
1097 function is called, the window to be resized is selected."
1098   :type '(choice integer function)
1099   :group 'help
1100   :version "24.3")
1101
1102 (defcustom temp-buffer-max-width
1103   (lambda (buffer)
1104     (if (eq (selected-window) (frame-root-window))
1105         (/ (x-display-pixel-width) (frame-char-width) 2)
1106       (/ (- (frame-width) 2) 2)))
1107   "Maximum width of a window displaying a temporary buffer.
1108 This is effective only when Temp Buffer Resize mode is enabled.
1109 The value is the maximum width (in columns) which
1110 `resize-temp-buffer-window' will give to a window displaying a
1111 temporary buffer.  It can also be a function to be called to
1112 choose the width for such a buffer.  It gets one argument, the
1113 buffer, and should return a positive integer.  At the time the
1114 function is called, the window to be resized is selected."
1115   :type '(choice integer function)
1116   :group 'help
1117   :version "24.4")
1118
1119 (define-minor-mode temp-buffer-resize-mode
1120   "Toggle auto-resizing temporary buffer windows (Temp Buffer Resize Mode).
1121 With a prefix argument ARG, enable Temp Buffer Resize mode if ARG
1122 is positive, and disable it otherwise.  If called from Lisp,
1123 enable the mode if ARG is omitted or nil.
1124
1125 When Temp Buffer Resize mode is enabled, the windows in which we
1126 show a temporary buffer are automatically resized in height to
1127 fit the buffer's contents, but never more than
1128 `temp-buffer-max-height' nor less than `window-min-height'.
1129
1130 A window is resized only if it has been specially created for the
1131 buffer.  Windows that have shown another buffer before are not
1132 resized.  A frame is resized only if `fit-frame-to-buffer' is
1133 non-nil.
1134
1135 This mode is used by `help', `apropos' and `completion' buffers,
1136 and some others."
1137   :global t :group 'help
1138   (if temp-buffer-resize-mode
1139       ;; `help-make-xrefs' may add a `back' button and thus increase the
1140       ;; text size, so `resize-temp-buffer-window' must be run *after* it.
1141       (add-hook 'temp-buffer-show-hook 'resize-temp-buffer-window 'append)
1142     (remove-hook 'temp-buffer-show-hook 'resize-temp-buffer-window)))
1143
1144 (defun resize-temp-buffer-window (&optional window)
1145   "Resize WINDOW to fit its contents.
1146 WINDOW must be a live window and defaults to the selected one.
1147 Do not resize if WINDOW was not created by `display-buffer'.
1148
1149 If WINDOW is part of a vertical combination, restrain its new
1150 size by `temp-buffer-max-height' and do not resize if its minimum
1151 accessible position is scrolled out of view.  If WINDOW is part
1152 of a horizontal combination, restrain its new size by
1153 `temp-buffer-max-width'.  In both cases, the value of the option
1154 `fit-window-to-buffer-horizontally' can inhibit resizing.
1155
1156 If WINDOW is the root window of its frame, resize the frame
1157 provided `fit-frame-to-buffer' is non-nil."
1158   (setq window (window-normalize-window window t))
1159   (let ((height (if (functionp temp-buffer-max-height)
1160                     (with-selected-window window
1161                       (funcall temp-buffer-max-height (window-buffer)))
1162                   temp-buffer-max-height))
1163         (width (if (functionp temp-buffer-max-width)
1164                    (with-selected-window window
1165                      (funcall temp-buffer-max-width (window-buffer)))
1166                  temp-buffer-max-width))
1167         (quit-cadr (cadr (window-parameter window 'quit-restore))))
1168     ;; Resize WINDOW iff it was made by `display-buffer'.
1169     (when (or (and (eq quit-cadr 'window)
1170                    (or (and (window-combined-p window)
1171                             (not (eq fit-window-to-buffer-horizontally
1172                                      'only))
1173                             (pos-visible-in-window-p (point-min) window))
1174                        (and (window-combined-p window t)
1175                             fit-window-to-buffer-horizontally)))
1176               (and (eq quit-cadr 'frame)
1177                      fit-frame-to-buffer
1178                      (eq window (frame-root-window window))))
1179         (fit-window-to-buffer window height nil width))))
1180
1181 ;;; Help windows.
1182 (defcustom help-window-select 'other
1183     "Non-nil means select help window for viewing.
1184 Choices are:
1185  never (nil) Select help window only if there is no other window
1186              on its frame.
1187  other       Select help window unless the selected window is the
1188              only other window on the help window's frame.
1189  always (t)  Always select the help window.
1190
1191 This option has effect if and only if the help window was created
1192 by `with-help-window'"
1193   :type '(choice (const :tag "never (nil)" nil)
1194                  (const :tag "other" other)
1195                  (const :tag "always (t)" t))
1196   :group 'help
1197   :version "23.1")
1198
1199 (defcustom help-enable-auto-load t
1200   "Whether Help commands can perform autoloading.
1201 If non-nil, whenever \\[describe-function] is called for an
1202 autoloaded function whose docstring contains any key substitution
1203 construct (see `substitute-command-keys'), the library is loaded,
1204 so that the documentation can show the right key bindings."
1205   :type 'boolean
1206   :group 'help
1207   :version "24.3")
1208
1209 (defun help-window-display-message (quit-part window &optional scroll)
1210   "Display message telling how to quit and scroll help window.
1211 QUIT-PART is a string telling how to quit the help window WINDOW.
1212 Optional argument SCROLL non-nil means tell how to scroll WINDOW.
1213 SCROLL equal `other' means tell how to scroll the \"other\"
1214 window."
1215   (let ((scroll-part
1216          (cond
1217           ;; If we don't have QUIT-PART we probably reuse a window
1218           ;; showing the same buffer so we don't show any message.
1219           ((not quit-part) nil)
1220           ((pos-visible-in-window-p
1221             (with-current-buffer (window-buffer window)
1222               (point-max)) window t)
1223            ;; Buffer end is at least partially visible, no need to talk
1224            ;; about scrolling.
1225            ".")
1226           ((eq scroll 'other)
1227            ", \\[scroll-other-window] to scroll help.")
1228           (scroll ", \\[scroll-up] to scroll help."))))
1229     (message "%s"
1230      (substitute-command-keys (concat quit-part scroll-part)))))
1231
1232 (defun help-window-setup (window &optional value)
1233   "Set up help window WINDOW for `with-help-window'.
1234 WINDOW is the window used for displaying the help buffer.
1235 Return VALUE."
1236   (let* ((help-buffer (when (window-live-p window)
1237                         (window-buffer window)))
1238          (help-setup (when (window-live-p window)
1239                        (car (window-parameter window 'quit-restore)))))
1240     (when help-buffer
1241       ;; Handle `help-window-point-marker'.
1242       (when (eq (marker-buffer help-window-point-marker) help-buffer)
1243         (set-window-point window help-window-point-marker)
1244         ;; Reset `help-window-point-marker'.
1245         (set-marker help-window-point-marker nil))
1246
1247       (cond
1248        ((or (eq window (selected-window))
1249             (and (or (eq help-window-select t)
1250                      (eq help-setup 'frame)
1251                      (and (eq help-window-select 'other)
1252                           (eq (window-frame window) (selected-frame))
1253                           (> (length (window-list nil 'no-mini)) 2)))
1254                  (select-window window)))
1255         ;; The help window is or gets selected ...
1256         (help-window-display-message
1257          (cond
1258           ((eq help-setup 'window)
1259            ;; ... and is new, ...
1260            "Type \"q\" to delete help window")
1261           ((eq help-setup 'frame)
1262            "Type \"q\" to quit the help frame")
1263           ((eq help-setup 'other)
1264            ;; ... or displayed some other buffer before.
1265            "Type \"q\" to restore previous buffer"))
1266          window t))
1267        ((and (eq (window-frame window) (selected-frame))
1268              (= (length (window-list nil 'no-mini)) 2))
1269         ;; There are two windows on the help window's frame and the
1270         ;; other one is the selected one.
1271         (help-window-display-message
1272          (cond
1273           ((eq help-setup 'window)
1274            "Type \\[delete-other-windows] to delete the help window")
1275           ((eq help-setup 'other)
1276            "Type \"q\" in help window to restore its previous buffer"))
1277          window 'other))
1278        (t
1279         ;; The help window is not selected ...
1280         (help-window-display-message
1281          (cond
1282           ((eq help-setup 'window)
1283            ;; ... and is new, ...
1284            "Type \"q\" in help window to delete it")
1285           ((eq help-setup 'other)
1286            ;; ... or displayed some other buffer before.
1287            "Type \"q\" in help window to restore previous buffer"))
1288          window))))
1289     ;; Return VALUE.
1290     value))
1291
1292 ;; Called from C, on encountering `help-char' when reading a char.
1293 ;; Don't print to *Help*; that would clobber Help history.
1294 (defun help-form-show ()
1295   "Display the output of a non-nil `help-form'."
1296   (let ((msg (eval help-form)))
1297     (if (stringp msg)
1298         (with-output-to-temp-buffer " *Char Help*"
1299           (princ msg)))))
1300
1301 \f
1302 ;; The following functions used to be in help-fns.el, which is not preloaded.
1303 ;; But for various reasons, they are more widely needed, so they were
1304 ;; moved to this file, which is preloaded.  http://debbugs.gnu.org/17001
1305
1306 (defun help-split-fundoc (docstring def)
1307   "Split a function DOCSTRING into the actual doc and the usage info.
1308 Return (USAGE . DOC) or nil if there's no usage info, where USAGE info
1309 is a string describing the argument list of DEF, such as
1310 \"(apply FUNCTION &rest ARGUMENTS)\".
1311 DEF is the function whose usage we're looking for in DOCSTRING."
1312   ;; Functions can get the calling sequence at the end of the doc string.
1313   ;; In cases where `function' has been fset to a subr we can't search for
1314   ;; function's name in the doc string so we use `fn' as the anonymous
1315   ;; function name instead.
1316   (when (and docstring (string-match "\n\n(fn\\(\\( .*\\)?)\\)\\'" docstring))
1317     (cons (format "(%s%s"
1318                   ;; Replace `fn' with the actual function name.
1319                   (if (symbolp def) def "anonymous")
1320                   (match-string 1 docstring))
1321           (unless (zerop (match-beginning 0))
1322             (substring docstring 0 (match-beginning 0))))))
1323
1324 (defun help-add-fundoc-usage (docstring arglist)
1325   "Add the usage info to DOCSTRING.
1326 If DOCSTRING already has a usage info, then just return it unchanged.
1327 The usage info is built from ARGLIST.  DOCSTRING can be nil.
1328 ARGLIST can also be t or a string of the form \"(FUN ARG1 ARG2 ...)\"."
1329   (unless (stringp docstring) (setq docstring ""))
1330   (if (or (string-match "\n\n(fn\\(\\( .*\\)?)\\)\\'" docstring)
1331           (eq arglist t))
1332       docstring
1333     (concat docstring
1334             (if (string-match "\n?\n\\'" docstring)
1335                 (if (< (- (match-end 0) (match-beginning 0)) 2) "\n" "")
1336               "\n\n")
1337             (if (and (stringp arglist)
1338                      (string-match "\\`([^ ]+\\(.*\\))\\'" arglist))
1339                 (concat "(fn" (match-string 1 arglist) ")")
1340               (format "%S" (help-make-usage 'fn arglist))))))
1341
1342 (defun help-function-arglist (def &optional preserve-names)
1343   "Return a formal argument list for the function DEF.
1344 IF PRESERVE-NAMES is non-nil, return a formal arglist that uses
1345 the same names as used in the original source code, when possible."
1346   ;; Handle symbols aliased to other symbols.
1347   (if (and (symbolp def) (fboundp def)) (setq def (indirect-function def)))
1348   ;; If definition is a macro, find the function inside it.
1349   (if (eq (car-safe def) 'macro) (setq def (cdr def)))
1350   (cond
1351    ((and (byte-code-function-p def) (listp (aref def 0))) (aref def 0))
1352    ((eq (car-safe def) 'lambda) (nth 1 def))
1353    ((eq (car-safe def) 'closure) (nth 2 def))
1354    ((or (and (byte-code-function-p def) (integerp (aref def 0)))
1355         (subrp def))
1356     (or (when preserve-names
1357           (let* ((doc (condition-case nil (documentation def) (error nil)))
1358                  (docargs (if doc (car (help-split-fundoc doc nil))))
1359                  (arglist (if docargs
1360                               (cdar (read-from-string (downcase docargs)))))
1361                  (valid t))
1362             ;; Check validity.
1363             (dolist (arg arglist)
1364               (unless (and (symbolp arg)
1365                            (let ((name (symbol-name arg)))
1366                              (if (eq (aref name 0) ?&)
1367                                  (memq arg '(&rest &optional))
1368                                (not (string-match "\\." name)))))
1369                 (setq valid nil)))
1370             (when valid arglist)))
1371         (let* ((args-desc (if (not (subrp def))
1372                               (aref def 0)
1373                             (let ((a (subr-arity def)))
1374                               (logior (car a)
1375                                       (if (numberp (cdr a))
1376                                           (lsh (cdr a) 8)
1377                                         (lsh 1 7))))))
1378                (max (lsh args-desc -8))
1379                (min (logand args-desc 127))
1380                (rest (logand args-desc 128))
1381                (arglist ()))
1382           (dotimes (i min)
1383             (push (intern (concat "arg" (number-to-string (1+ i)))) arglist))
1384           (when (> max min)
1385             (push '&optional arglist)
1386             (dotimes (i (- max min))
1387               (push (intern (concat "arg" (number-to-string (+ 1 i min))))
1388                     arglist)))
1389           (unless (zerop rest) (push '&rest arglist) (push 'rest arglist))
1390           (nreverse arglist))))
1391    ((and (autoloadp def) (not (eq (nth 4 def) 'keymap)))
1392     "[Arg list not available until function definition is loaded.]")
1393    (t t)))
1394
1395 (defun help-make-usage (function arglist)
1396   (cons (if (symbolp function) function 'anonymous)
1397         (mapcar (lambda (arg)
1398                   (if (not (symbolp arg)) arg
1399                     (let ((name (symbol-name arg)))
1400                       (cond
1401                        ((string-match "\\`&" name) arg)
1402                        ((string-match "\\`_" name)
1403                         (intern (upcase (substring name 1))))
1404                        (t (intern (upcase name)))))))
1405                 arglist)))
1406
1407 \f
1408 (provide 'help)
1409
1410 ;;; help.el ends here