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 built-in 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-window-old-frame nil
  50   "Frame selected at the time `with-help-window' is invoked.")
  51
  52 (defvar help-map
  53   (let ((map (make-sparse-keymap)))
  54     (define-key map (char-to-string help-char) 'help-for-help)
  55     (define-key map [help] 'help-for-help)
  56     (define-key map [f1] 'help-for-help)
  57     (define-key map "." 'display-local-help)
  58     (define-key map "?" 'help-for-help)
  59
  60     (define-key map "\C-a" 'about-emacs)
  61     (define-key map "\C-c" 'describe-copying)
  62     (define-key map "\C-d" 'view-emacs-debugging)
  63     (define-key map "\C-e" 'view-external-packages)
  64     (define-key map "\C-f" 'view-emacs-FAQ)
  65     (define-key map "\C-m" 'view-order-manuals)
  66     (define-key map "\C-n" 'view-emacs-news)
  67     (define-key map "\C-o" 'describe-distribution)
  68     (define-key map "\C-p" 'view-emacs-problems)
  69     (define-key map "\C-t" 'view-emacs-todo)
  70     (define-key map "\C-w" 'describe-no-warranty)
  71
  72     ;; This does not fit the pattern, but it is natural given the C-\ command.
  73     (define-key map "\C-\\" 'describe-input-method)
  74
  75     (define-key map "C" 'describe-coding-system)
  76     (define-key map "F" 'Info-goto-emacs-command-node)
  77     (define-key map "I" 'describe-input-method)
  78     (define-key map "K" 'Info-goto-emacs-key-command-node)
  79     (define-key map "L" 'describe-language-environment)
  80     (define-key map "S" 'info-lookup-symbol)
  81
  82     (define-key map "a" 'apropos-command)
  83     (define-key map "b" 'describe-bindings)
  84     (define-key map "c" 'describe-key-briefly)
  85     (define-key map "d" 'apropos-documentation)
  86     (define-key map "e" 'view-echo-area-messages)
  87     (define-key map "f" 'describe-function)
  88     (define-key map "g" 'describe-gnu-project)
  89     (define-key map "h" 'view-hello-file)
  90
  91     (define-key map "i" 'info)
  92     (define-key map "4i" 'info-other-window)
  93
  94     (define-key map "k" 'describe-key)
  95     (define-key map "l" 'view-lossage)
  96     (define-key map "m" 'describe-mode)
  97     (define-key map "n" 'view-emacs-news)
  98     (define-key map "p" 'finder-by-keyword)
  99     (define-key map "P" 'describe-package)
 100     (define-key map "r" 'info-emacs-manual)
 101     (define-key map "s" 'describe-syntax)
 102     (define-key map "t" 'help-with-tutorial)
 103     (define-key map "w" 'where-is)
 104     (define-key map "v" 'describe-variable)
 105     (define-key map "q" 'help-quit)
 106     map)
 107   "Keymap for characters following the Help key.")
 108
 109 (define-key global-map (char-to-string help-char) 'help-command)
 110 (define-key global-map [help] 'help-command)
 111 (define-key global-map [f1] 'help-command)
 112 (fset 'help-command help-map)
 113
 114 ;; insert-button makes the action nil if it is not store somewhere
 115 (defvar help-button-cache nil)
 116
 117 \f
 118 (defun help-quit ()
 119   "Just exit from the Help command's command loop."
 120   (interactive)
 121   nil)
 122
 123 (defvar help-return-method nil
 124   "What to do to \"exit\" the help buffer.
 125 This is a list
 126  (WINDOW . t)              delete the selected window (and possibly its frame,
 127                            see `quit-window'), go to WINDOW.
 128  (WINDOW . quit-window)    do quit-window, then select WINDOW.
 129  (WINDOW BUF START POINT)  display BUF at START, POINT, then select WINDOW.")
 130
 131 (define-obsolete-function-alias 'print-help-return-message 'help-print-return-message "23.2")
 132 (defun help-print-return-message (&optional function)
 133   "Display or return message saying how to restore windows after help command.
 134 This function assumes that `standard-output' is the help buffer.
 135 It computes a message, and applies the optional argument FUNCTION to it.
 136 If FUNCTION is nil, it applies `message', thus displaying the message.
 137 In addition, this function sets up `help-return-method', which see, that
 138 specifies what to do when the user exits the help buffer.
 139
 140 Do not call this in the scope of `with-help-window'."
 141   (and (not (get-buffer-window standard-output))
 142        (let ((first-message
 143               (cond ((or
 144                       pop-up-frames
 145                       (special-display-p (buffer-name standard-output)))
 146                      (setq help-return-method (cons (selected-window) t))
 147                      ;; If the help output buffer is a special display buffer,
 148                      ;; don't say anything about how to get rid of it.
 149                      ;; First of all, the user will do that with the window
 150                      ;; manager, not with Emacs.
 151                      ;; Secondly, the buffer has not been displayed yet,
 152                      ;; so we don't know whether its frame will be selected.
 153                      nil)
 154                     ((not (one-window-p t))
 155                      (setq help-return-method
 156                            (cons (selected-window) 'quit-window))
 157                      "Type \\[display-buffer] RET to restore the other window.")
 158                     (pop-up-windows
 159                      (setq help-return-method (cons (selected-window) t))
 160                      "Type \\[delete-other-windows] to remove help window.")
 161                     (t
 162                      (setq help-return-method
 163                            (list (selected-window) (window-buffer)
 164                                  (window-start) (window-point)))
 165                      "Type \\[switch-to-buffer] RET to remove help window."))))
 166          (funcall (or function 'message)
 167                   (concat
 168                    (if first-message
 169                        (substitute-command-keys first-message))
 170                    (if first-message "  ")
 171                    ;; If the help buffer will go in a separate frame,
 172                    ;; it's no use mentioning a command to scroll, so don't.
 173                    (if (or pop-up-windows
 174                            (special-display-p (buffer-name standard-output)))
 175                        nil
 176                      (if (same-window-p (buffer-name standard-output))
 177                          ;; Say how to scroll this window.
 178                          (substitute-command-keys
 179                           "\\[scroll-up] to scroll the help.")
 180                        ;; Say how to scroll some other window.
 181                        (substitute-command-keys
 182                         "\\[scroll-other-window] to scroll the help."))))))))
 183
 184 ;; So keyboard macro definitions are documented correctly
 185 (fset 'defining-kbd-macro (symbol-function 'start-kbd-macro))
 186
 187 (defalias 'help 'help-for-help-internal)
 188 ;; find-function can find this.
 189 (defalias 'help-for-help 'help-for-help-internal)
 190 ;; It can't find this, but nobody will look.
 191 (make-help-screen help-for-help-internal
 192   (purecopy "Type a help option: [abcCdefFgiIkKlLmnprstvw.] C-[cdefmnoptw] or ?")
 193   ;; Don't purecopy this one, because it's not evaluated (it's
 194   ;; directly used as a docstring in a function definition, so it'll
 195   ;; be moved to the DOC file anyway: no need for purecopying it).
 196   "You have typed %THIS-KEY%, the help character.  Type a Help option:
 197 \(Use SPC or DEL to scroll through this text.  Type \\<help-map>\\[help-quit] to exit the Help command.)
 198
 199 a PATTERN   Show commands whose name matches the PATTERN (a list of words
 200               or a regexp).  See also the `apropos' command.
 201 b           Display all key bindings.
 202 c KEYS      Display the command name run by the given key sequence.
 203 C CODING    Describe the given coding system, or RET for current ones.
 204 d PATTERN   Show a list of functions, variables, and other items whose
 205               documentation matches the PATTERN (a list of words or a regexp).
 206 e           Go to the *Messages* buffer which logs echo-area messages.
 207 f FUNCTION  Display documentation for the given function.
 208 F COMMAND   Show the Emacs manual's section that describes the command.
 209 g           Display information about the GNU project.
 210 h           Display the HELLO file which illustrates various scripts.
 211 i           Start the Info documentation reader: read included manuals.
 212 I METHOD    Describe a specific input method, or RET for current.
 213 k KEYS      Display the full documentation for the key sequence.
 214 K KEYS      Show the Emacs manual's section for the command bound to KEYS.
 215 l           Show last 300 input keystrokes (lossage).
 216 L LANG-ENV  Describes a specific language environment, or RET for current.
 217 m           Display documentation of current minor modes and current major mode,
 218               including their special commands.
 219 n           Display news of recent Emacs changes.
 220 p TOPIC     Find packages matching a given topic keyword.
 221 P PACKAGE   Describe the given Emacs Lisp package.
 222 r           Display the Emacs manual in Info mode.
 223 s           Display contents of current syntax table, plus explanations.
 224 S SYMBOL    Show the section for the given symbol in the Info manual
 225               for the programming language used in this buffer.
 226 t           Start the Emacs learn-by-doing tutorial.
 227 v VARIABLE  Display the given variable's documentation and value.
 228 w COMMAND   Display which keystrokes invoke the given command (where-is).
 229 .           Display any available local help at point in the echo area.
 230
 231 C-a         Information about Emacs.
 232 C-c         Emacs copying permission (GNU General Public License).
 233 C-d         Instructions for debugging GNU Emacs.
 234 C-e         External packages and information about Emacs.
 235 C-f         Emacs FAQ.
 236 C-m         How to order printed Emacs manuals.
 237 C-n         News of recent Emacs changes.
 238 C-o         Emacs ordering and distribution information.
 239 C-p         Info about known Emacs problems.
 240 C-t         Emacs TODO list.
 241 C-w         Information on absence of warranty for GNU Emacs."
 242   help-map)
 243
 244 \f
 245
 246 (defun function-called-at-point ()
 247   "Return a function around point or else called by the list containing point.
 248 If that doesn't give a function, return nil."
 249   (with-syntax-table emacs-lisp-mode-syntax-table
 250     (or (condition-case ()
 251             (save-excursion
 252               (or (not (zerop (skip-syntax-backward "_w")))
 253                   (eq (char-syntax (following-char)) ?w)
 254                   (eq (char-syntax (following-char)) ?_)
 255                   (forward-sexp -1))
 256               (skip-chars-forward "'")
 257               (let ((obj (read (current-buffer))))
 258                 (and (symbolp obj) (fboundp obj) obj)))
 259           (error nil))
 260         (condition-case ()
 261             (save-excursion
 262               (save-restriction
 263                 (narrow-to-region (max (point-min)
 264                                        (- (point) 1000)) (point-max))
 265                 ;; Move up to surrounding paren, then after the open.
 266                 (backward-up-list 1)
 267                 (forward-char 1)
 268                 ;; If there is space here, this is probably something
 269                 ;; other than a real Lisp function call, so ignore it.
 270                 (if (looking-at "[ \t]")
 271                     (error "Probably not a Lisp function call"))
 272                 (let ((obj (read (current-buffer))))
 273                   (and (symbolp obj) (fboundp obj) obj))))
 274           (error nil))
 275         (let* ((str (find-tag-default))
 276                (sym (if str (intern-soft str))))
 277           (if (and sym (fboundp sym))
 278               sym
 279             (save-match-data
 280               (when (and str (string-match "\\`\\W*\\(.*?\\)\\W*\\'" str))
 281                 (setq sym (intern-soft (match-string 1 str)))
 282                 (and (fboundp sym) sym))))))))
 283
 284 \f
 285 ;;; `User' help functions
 286
 287 (defun view-help-file (file &optional dir)
 288   (view-file (expand-file-name file (or dir data-directory)))
 289   (goto-address-mode 1)
 290   (goto-char (point-min)))
 291
 292 (defun describe-distribution ()
 293   "Display info on how to obtain the latest version of GNU Emacs."
 294   (interactive)
 295   (view-help-file "DISTRIB"))
 296
 297 (defun describe-copying ()
 298   "Display info on how you may redistribute copies of GNU Emacs."
 299   (interactive)
 300   (view-help-file "COPYING"))
 301
 302 ;; Maybe this command should just be removed.
 303 (defun describe-gnu-project ()
 304   "Browse online information on the GNU project."
 305   (interactive)
 306   (browse-url "http://www.gnu.org/gnu/thegnuproject.html"))
 307
 308 (define-obsolete-function-alias 'describe-project 'describe-gnu-project "22.2")
 309
 310 (defun describe-no-warranty ()
 311   "Display info on all the kinds of warranty Emacs does NOT have."
 312   (interactive)
 313   (describe-copying)
 314   (let (case-fold-search)
 315     (search-forward "Disclaimer of Warranty")
 316     (forward-line 0)
 317     (recenter 0)))
 318
 319 (defun describe-prefix-bindings ()
 320   "Describe the bindings of the prefix used to reach this command.
 321 The prefix described consists of all but the last event
 322 of the key sequence that ran this command."
 323   (interactive)
 324   (let ((key (this-command-keys)))
 325     (describe-bindings
 326      (if (stringp key)
 327          (substring key 0 (1- (length key)))
 328        (let ((prefix (make-vector (1- (length key)) nil))
 329              (i 0))
 330          (while (< i (length prefix))
 331            (aset prefix i (aref key i))
 332            (setq i (1+ i)))
 333          prefix)))))
 334 ;; Make C-h after a prefix, when not specifically bound,
 335 ;; run describe-prefix-bindings.
 336 (setq prefix-help-command 'describe-prefix-bindings)
 337
 338 (defun view-emacs-news (&optional version)
 339   "Display info on recent changes to Emacs.
 340 With argument, display info only for the selected version."
 341   (interactive "P")
 342   (unless version
 343     (setq version emacs-major-version))
 344   (when (consp version)
 345     (let* ((all-versions
 346             (let (res)
 347               (mapc
 348                (lambda (file)
 349                  (with-temp-buffer
 350                    (insert-file-contents
 351                     (expand-file-name file data-directory))
 352                    (while (re-search-forward
 353                            (if (member file '("NEWS.18" "NEWS.1-17"))
 354                                "Changes in \\(?:Emacs\\|version\\)?[ \t]*\\([0-9]+\\(?:\\.[0-9]+\\)?\\)"
 355                              "^\* [^0-9\n]*\\([0-9]+\\.[0-9]+\\)") nil t)
 356                      (setq res (cons (match-string-no-properties 1) res)))))
 357                (cons "NEWS"
 358                      (directory-files data-directory nil
 359                                       "^NEWS\\.[0-9][-0-9]*$" nil)))
 360               (sort (delete-dups res) (lambda (a b) (string< b a)))))
 361            (current (car all-versions)))
 362       (setq version (completing-read
 363                      (format "Read NEWS for the version (default %s): " current)
 364                      all-versions nil nil nil nil current))
 365       (if (integerp (string-to-number version))
 366           (setq version (string-to-number version))
 367         (unless (or (member version all-versions)
 368                     (<= (string-to-number version) (string-to-number current)))
 369           (error "No news about version %s" version)))))
 370   (when (integerp version)
 371     (cond ((<= version 12)
 372            (setq version (format "1.%d" version)))
 373           ((<= version 18)
 374            (setq version (format "%d" version)))
 375           ((> version emacs-major-version)
 376            (error "No news about Emacs %d (yet)" version))))
 377   (let* ((vn (if (stringp version)
 378                  (string-to-number version)
 379                version))
 380          (file (cond
 381                 ((>= vn emacs-major-version) "NEWS")
 382                 ((< vn 18) "NEWS.1-17")
 383                 (t (format "NEWS.%d" vn))))
 384          res)
 385     (view-file (expand-file-name file data-directory))
 386     (widen)
 387     (goto-char (point-min))
 388     (when (stringp version)
 389       (when (re-search-forward
 390              (concat (if (< vn 19)
 391                          "Changes in Emacs[ \t]*"
 392                        "^\* [^0-9\n]*") version "$")
 393              nil t)
 394         (beginning-of-line)
 395         (narrow-to-region
 396          (point)
 397          (save-excursion
 398            (while (and (setq res
 399                              (re-search-forward
 400                               (if (< vn 19)
 401                                   "Changes in \\(?:Emacs\\|version\\)?[ \t]*\\([0-9]+\\(?:\\.[0-9]+\\)?\\)"
 402                                 "^\* [^0-9\n]*\\([0-9]+\\.[0-9]+\\)") nil t))
 403                        (equal (match-string-no-properties 1) version)))
 404            (or res (goto-char (point-max)))
 405            (beginning-of-line)
 406            (point)))))))
 407
 408 (defun view-emacs-todo (&optional _arg)
 409   "Display the Emacs TODO list."
 410   (interactive "P")
 411   (view-help-file "TODO"))
 412
 413 (define-obsolete-function-alias 'view-todo 'view-emacs-todo "22.2")
 414
 415
 416 (defun view-echo-area-messages ()
 417   "View the log of recent echo-area messages: the `*Messages*' buffer.
 418 The number of messages retained in that buffer
 419 is specified by the variable `message-log-max'."
 420   (interactive)
 421   (with-current-buffer (messages-buffer)
 422     (goto-char (point-max))
 423     (display-buffer (current-buffer))))
 424
 425 (defun view-order-manuals ()
 426   "Display information on how to buy printed copies of Emacs manuals."
 427   (interactive)
 428 ;;  (view-help-file "ORDERS")
 429   (info "(emacs)Printed Books"))
 430
 431 (defun view-emacs-FAQ ()
 432   "Display the Emacs Frequently Asked Questions (FAQ) file."
 433   (interactive)
 434   ;; (find-file-read-only (expand-file-name "FAQ" data-directory))
 435   (info "(efaq)"))
 436
 437 (defun view-emacs-problems ()
 438   "Display info on known problems with Emacs and possible workarounds."
 439   (interactive)
 440   (view-help-file "PROBLEMS"))
 441
 442 (defun view-emacs-debugging ()
 443   "Display info on how to debug Emacs problems."
 444   (interactive)
 445   (view-help-file "DEBUG"))
 446
 447 ;; This used to visit MORE.STUFF; maybe it should just be removed.
 448 (defun view-external-packages ()
 449   "Display info on where to get more Emacs packages."
 450   (interactive)
 451   (info "(efaq)Packages that do not come with Emacs"))
 452
 453 (defun view-lossage ()
 454   "Display last few input keystrokes and the commands run.
 455
 456 To record all your input, use `open-dribble-file'."
 457   (interactive)
 458   (help-setup-xref (list #'view-lossage)
 459                    (called-interactively-p 'interactive))
 460   (with-help-window (help-buffer)
 461     (princ " ")
 462     (princ (mapconcat (lambda (key)
 463                         (cond
 464                          ((and (consp key) (null (car key)))
 465                           (format "[%s]\n" (if (symbolp (cdr key)) (cdr key)
 466                                            "anonymous-command")))
 467                          ((or (integerp key) (symbolp key) (listp key))
 468                           (single-key-description key))
 469                          (t
 470                           (prin1-to-string key nil))))
 471                       (recent-keys 'include-cmds)
 472                       " "))
 473     (with-current-buffer standard-output
 474       (goto-char (point-min))
 475       (while (not (eobp))
 476         (move-to-column 50)
 477         (unless (eolp)
 478           (fill-region (line-beginning-position) (line-end-position)))
 479         (forward-line 1))
 480       ;; jidanni wants to see the last keystrokes immediately.
 481       (set-marker help-window-point-marker (point)))))
 482
 483 \f
 484 ;; Key bindings
 485
 486 (defun describe-bindings (&optional prefix buffer)
 487   "Display a buffer showing a list of all defined keys, and their definitions.
 488 The keys are displayed in order of precedence.
 489
 490 The optional argument PREFIX, if non-nil, should be a key sequence;
 491 then we display only bindings that start with that prefix.
 492 The optional argument BUFFER specifies which buffer's bindings
 493 to display (default, the current buffer).  BUFFER can be a buffer
 494 or a buffer name."
 495   (interactive)
 496   (or buffer (setq buffer (current-buffer)))
 497   (help-setup-xref (list #'describe-bindings prefix buffer)
 498                    (called-interactively-p 'interactive))
 499   (with-help-window (help-buffer)
 500     ;; Be aware that `describe-buffer-bindings' puts its output into
 501     ;; the current buffer.
 502     (with-current-buffer (help-buffer)
 503       (describe-buffer-bindings buffer prefix))))
 504
 505 ;; This function used to be in keymap.c.
 506 (defun describe-bindings-internal (&optional menus prefix)
 507   "Show a list of all defined keys, and their definitions.
 508 We put that list in a buffer, and display the buffer.
 509
 510 The optional argument MENUS, if non-nil, says to mention menu bindings.
 511 \(Ordinarily these are omitted from the output.)
 512 The optional argument PREFIX, if non-nil, should be a key sequence;
 513 then we display only bindings that start with that prefix."
 514   (declare (obsolete describe-buffer-bindings "24.4"))
 515   (let ((buf (current-buffer)))
 516     (with-help-window (help-buffer)
 517       ;; Be aware that `describe-buffer-bindings' puts its output into
 518       ;; the current buffer.
 519       (with-current-buffer (help-buffer)
 520         (describe-buffer-bindings buf prefix menus)))))
 521
 522 (defun where-is (definition &optional insert)
 523   "Print message listing key sequences that invoke the command DEFINITION.
 524 Argument is a command definition, usually a symbol with a function definition.
 525 If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
 526   (interactive
 527    (let ((fn (function-called-at-point))
 528          (enable-recursive-minibuffers t)
 529          val)
 530      (setq val (completing-read
 531                 (if fn
 532                     (format "Where is command (default %s): " fn)
 533                   "Where is command: ")
 534                 obarray 'commandp t nil nil
 535                 (and fn (symbol-name fn))))
 536      (list (unless (equal val "") (intern val))
 537            current-prefix-arg)))
 538   (unless definition (error "No command"))
 539   (let ((func (indirect-function definition))
 540         (defs nil)
 541         (standard-output (if insert (current-buffer) standard-output)))
 542     ;; In DEFS, find all symbols that are aliases for DEFINITION.
 543     (mapatoms (lambda (symbol)
 544                 (and (fboundp symbol)
 545                      (not (eq symbol definition))
 546                      (eq func (condition-case ()
 547                                   (indirect-function symbol)
 548                                 (error symbol)))
 549                      (push symbol defs))))
 550     ;; Look at all the symbols--first DEFINITION,
 551     ;; then its aliases.
 552     (dolist (symbol (cons definition defs))
 553       (let* ((remapped (command-remapping symbol))
 554              (keys (where-is-internal
 555                     symbol overriding-local-map nil nil remapped))
 556              (keys (mapconcat 'key-description keys ", "))
 557              string)
 558         (setq string
 559               (if insert
 560                   (if (> (length keys) 0)
 561                       (if remapped
 562                           (format "%s (%s) (remapped from %s)"
 563                                   keys remapped symbol)
 564                         (format "%s (%s)" keys symbol))
 565                     (format "M-x %s RET" symbol))
 566                 (if (> (length keys) 0)
 567                     (if remapped
 568                         (format "%s is remapped to %s which is on %s"
 569                                 symbol remapped keys)
 570                       (format "%s is on %s" symbol keys))
 571                   ;; If this is the command the user asked about,
 572                   ;; and it is not on any key, say so.
 573                   ;; For other symbols, its aliases, say nothing
 574                   ;; about them unless they are on keys.
 575                   (if (eq symbol definition)
 576                       (format "%s is not on any key" symbol)))))
 577         (when string
 578           (unless (eq symbol definition)
 579             (princ ";\n its alias "))
 580           (princ string)))))
 581   nil)
 582
 583 (defun help-key-description (key untranslated)
 584   (let ((string (key-description key)))
 585     (if (or (not untranslated)
 586             (and (eq (aref untranslated 0) ?\e) (not (eq (aref key 0) ?\e))))
 587         string
 588       (let ((otherstring (key-description untranslated)))
 589         (if (equal string otherstring)
 590             string
 591           (format "%s (translated from %s)" string otherstring))))))
 592
 593 (defun describe-key-briefly (&optional key insert untranslated)
 594   "Print the name of the function KEY invokes.  KEY is a string.
 595 If INSERT (the prefix arg) is non-nil, insert the message in the buffer.
 596 If non-nil, UNTRANSLATED is a vector of the untranslated events.
 597 It can also be a number in which case the untranslated events from
 598 the last key hit are used.
 599
 600 If KEY is a menu item or a tool-bar button that is disabled, this command
 601 temporarily enables it to allow getting help on disabled items and buttons."
 602   (interactive
 603    (let ((enable-disabled-menus-and-buttons t)
 604          (cursor-in-echo-area t)
 605          saved-yank-menu)
 606      (unwind-protect
 607          (let (key)
 608            ;; If yank-menu is empty, populate it temporarily, so that
 609            ;; "Select and Paste" menu can generate a complete event.
 610            (when (null (cdr yank-menu))
 611              (setq saved-yank-menu (copy-sequence yank-menu))
 612              (menu-bar-update-yank-menu "(any string)" nil))
 613            (setq key (read-key-sequence "Describe key (or click or menu item): "))
 614            ;; Clear the echo area message (Bug#7014).
 615            (message nil)
 616            ;; If KEY is a down-event, read and discard the
 617            ;; corresponding up-event.  Note that there are also
 618            ;; down-events on scroll bars and mode lines: the actual
 619            ;; event then is in the second element of the vector.
 620            (and (vectorp key)
 621                 (let ((last-idx (1- (length key))))
 622                   (and (eventp (aref key last-idx))
 623                        (memq 'down (event-modifiers (aref key last-idx)))))
 624                 (read-event))
 625            (list
 626             key
 627             (if current-prefix-arg (prefix-numeric-value current-prefix-arg))
 628             1))
 629        ;; Put yank-menu back as it was, if we changed it.
 630        (when saved-yank-menu
 631          (setq yank-menu (copy-sequence saved-yank-menu))
 632          (fset 'yank-menu (cons 'keymap yank-menu))))))
 633   (if (numberp untranslated)
 634       (setq untranslated (this-single-command-raw-keys)))
 635   (let* ((event (if (and (symbolp (aref key 0))
 636                          (> (length key) 1)
 637                          (consp (aref key 1)))
 638                     (aref key 1)
 639                   (aref key 0)))
 640          (modifiers (event-modifiers event))
 641          (standard-output (if insert (current-buffer) standard-output))
 642          (mouse-msg (if (or (memq 'click modifiers) (memq 'down modifiers)
 643                             (memq 'drag modifiers)) " at that spot" ""))
 644          (defn (key-binding key t))
 645          key-desc)
 646     ;; Handle the case where we faked an entry in "Select and Paste" menu.
 647     (if (and (eq defn nil)
 648              (stringp (aref key (1- (length key))))
 649              (eq (key-binding (substring key 0 -1)) 'yank-menu))
 650         (setq defn 'menu-bar-select-yank))
 651     ;; Don't bother user with strings from (e.g.) the select-paste menu.
 652     (if (stringp (aref key (1- (length key))))
 653         (aset key (1- (length key)) "(any string)"))
 654     (if (and (> (length untranslated) 0)
 655              (stringp (aref untranslated (1- (length untranslated)))))
 656         (aset untranslated (1- (length untranslated)) "(any string)"))
 657     ;; Now describe the key, perhaps as changed.
 658     (setq key-desc (help-key-description key untranslated))
 659     (if (or (null defn) (integerp defn) (equal defn 'undefined))
 660         (princ (format "%s%s is undefined" key-desc mouse-msg))
 661       (princ (format "%s%s runs the command %S" key-desc mouse-msg defn)))))
 662
 663 (defun help--key-binding-keymap (key &optional accept-default no-remap position)
 664   "Return a keymap holding a binding for KEY within current keymaps.
 665 The effect of the arguments KEY, ACCEPT-DEFAULT, NO-REMAP and
 666 POSITION is as documented in the function `key-binding'."
 667   (let* ((active-maps (current-active-maps t position))
 668          map found)
 669     ;; We loop over active maps like key-binding does.
 670     (while (and
 671             (not found)
 672             (setq map (pop active-maps)))
 673       (setq found (lookup-key map key accept-default))
 674       (when (integerp found)
 675         ;; The first `found' characters of KEY were found but not the
 676         ;; whole sequence.
 677         (setq found nil)))
 678     (when found
 679       (if (and (symbolp found)
 680                (not no-remap)
 681                (command-remapping found))
 682           ;; The user might want to know in which map the binding is
 683           ;; found, or in which map the remapping is found.  The
 684           ;; default is to show the latter.
 685           (help--key-binding-keymap (vector 'remap found))
 686         map))))
 687
 688 (defun help--binding-locus (key position)
 689   "Describe in which keymap KEY is defined.
 690 Return a symbol pointing to that keymap if one exists ; otherwise
 691 return nil."
 692   (let ((map (help--key-binding-keymap key t nil position)))
 693     (when map
 694       (catch 'found
 695         (let ((advertised-syms (nconc
 696                                 (list 'overriding-terminal-local-map
 697                                       'overriding-local-map)
 698                                 (delq nil
 699                                       (mapcar
 700                                        (lambda (mode-and-map)
 701                                          (let ((mode (car mode-and-map)))
 702                                            (when (symbol-value mode)
 703                                              (intern-soft
 704                                               (format "%s-map" mode)))))
 705                                        minor-mode-map-alist))
 706                                 (list 'global-map
 707                                       (intern-soft (format "%s-map" major-mode)))))
 708               found)
 709           ;; Look into these advertised symbols first.
 710           (dolist (sym advertised-syms)
 711             (when (and
 712                    (boundp sym)
 713                    (eq map (symbol-value sym)))
 714               (throw 'found sym)))
 715           ;; Only look in other symbols otherwise.
 716           (mapatoms
 717            (lambda (x)
 718              (when (and (boundp x)
 719                         ;; Avoid let-bound symbols.
 720                         (special-variable-p x)
 721                         (eq (symbol-value x) map))
 722                (throw 'found x))))
 723           nil)))))
 724
 725 (defun describe-key (&optional key untranslated up-event)
 726   "Display documentation of the function invoked by KEY.
 727 KEY can be any kind of a key sequence; it can include keyboard events,
 728 mouse events, and/or menu events.  When calling from a program,
 729 pass KEY as a string or a vector.
 730
 731 If non-nil, UNTRANSLATED is a vector of the corresponding untranslated events.
 732 It can also be a number, in which case the untranslated events from
 733 the last key sequence entered are used.
 734 UP-EVENT is the up-event that was discarded by reading KEY, or nil.
 735
 736 If KEY is a menu item or a tool-bar button that is disabled, this command
 737 temporarily enables it to allow getting help on disabled items and buttons."
 738   (interactive
 739    (let ((enable-disabled-menus-and-buttons t)
 740          (cursor-in-echo-area t)
 741          saved-yank-menu)
 742      (unwind-protect
 743          (let (key)
 744            ;; If yank-menu is empty, populate it temporarily, so that
 745            ;; "Select and Paste" menu can generate a complete event.
 746            (when (null (cdr yank-menu))
 747              (setq saved-yank-menu (copy-sequence yank-menu))
 748              (menu-bar-update-yank-menu "(any string)" nil))
 749            (setq key (read-key-sequence "Describe key (or click or menu item): "))
 750            (list
 751             key
 752             (prefix-numeric-value current-prefix-arg)
 753             ;; If KEY is a down-event, read and include the
 754             ;; corresponding up-event.  Note that there are also
 755             ;; down-events on scroll bars and mode lines: the actual
 756             ;; event then is in the second element of the vector.
 757             (and (vectorp key)
 758                  (let ((last-idx (1- (length key))))
 759                    (and (eventp (aref key last-idx))
 760                         (memq 'down (event-modifiers (aref key last-idx)))))
 761                  (or (and (eventp (aref key 0))
 762                           (memq 'down (event-modifiers (aref key 0)))
 763                           ;; However, for the C-down-mouse-2 popup
 764                           ;; menu, there is no subsequent up-event.  In
 765                           ;; this case, the up-event is the next
 766                           ;; element in the supplied vector.
 767                           (= (length key) 1))
 768                      (and (> (length key) 1)
 769                           (eventp (aref key 1))
 770                           (memq 'down (event-modifiers (aref key 1)))))
 771                  (read-event))))
 772        ;; Put yank-menu back as it was, if we changed it.
 773        (when saved-yank-menu
 774          (setq yank-menu (copy-sequence saved-yank-menu))
 775          (fset 'yank-menu (cons 'keymap yank-menu))))))
 776   (if (numberp untranslated)
 777       (setq untranslated (this-single-command-raw-keys)))
 778   (let* ((event (aref key (if (and (symbolp (aref key 0))
 779                                    (> (length key) 1)
 780                                    (consp (aref key 1)))
 781                               1
 782                             0)))
 783          (modifiers (event-modifiers event))
 784          (mouse-msg (if (or (memq 'click modifiers) (memq 'down modifiers)
 785                             (memq 'drag modifiers)) " at that spot" ""))
 786          (defn (key-binding key t))
 787          key-locus key-locus-up key-locus-up-tricky
 788          defn-up defn-up-tricky ev-type
 789          mouse-1-remapped mouse-1-tricky)
 790
 791     ;; Handle the case where we faked an entry in "Select and Paste" menu.
 792     (when (and (eq defn nil)
 793                (stringp (aref key (1- (length key))))
 794                (eq (key-binding (substring key 0 -1)) 'yank-menu))
 795       (setq defn 'menu-bar-select-yank))
 796     (if (or (null defn) (integerp defn) (equal defn 'undefined))
 797         (message "%s%s is undefined"
 798                  (help-key-description key untranslated) mouse-msg)
 799       (help-setup-xref (list #'describe-function defn)
 800                        (called-interactively-p 'interactive))
 801       ;; Don't bother user with strings from (e.g.) the select-paste menu.
 802       (when (stringp (aref key (1- (length key))))
 803         (aset key (1- (length key)) "(any string)"))
 804       (when (and untranslated
 805                  (stringp (aref untranslated (1- (length untranslated)))))
 806         (aset untranslated (1- (length untranslated))
 807               "(any string)"))
 808       ;; Need to do this before erasing *Help* buffer in case event
 809       ;; is a mouse click in an existing *Help* buffer.
 810       (when up-event
 811         (setq ev-type (event-basic-type up-event))
 812         (let ((sequence (vector up-event)))
 813           (when (and (eq ev-type 'mouse-1)
 814                      mouse-1-click-follows-link
 815                      (not (eq mouse-1-click-follows-link 'double))
 816                      (setq mouse-1-remapped
 817                            (mouse-on-link-p (event-start up-event))))
 818             (setq mouse-1-tricky (and (integerp mouse-1-click-follows-link)
 819                                       (> mouse-1-click-follows-link 0)))
 820             (cond ((stringp mouse-1-remapped)
 821                    (setq sequence mouse-1-remapped))
 822                   ((vectorp mouse-1-remapped)
 823                    (setcar up-event (elt mouse-1-remapped 0)))
 824                   (t (setcar up-event 'mouse-2))))
 825           (setq defn-up (key-binding sequence nil nil (event-start up-event)))
 826           (setq key-locus-up (help--binding-locus sequence (event-start up-event)))
 827           (when mouse-1-tricky
 828             (setq sequence (vector up-event))
 829             (aset sequence 0 'mouse-1)
 830             (setq defn-up-tricky (key-binding sequence nil nil (event-start up-event)))
 831             (setq key-locus-up-tricky (help--binding-locus sequence (event-start up-event))))))
 832       (setq key-locus (help--binding-locus key (event-start event)))
 833       (with-help-window (help-buffer)
 834         (princ (help-key-description key untranslated))
 835         (princ (format "%s runs the command %S%s, which is "
 836                        mouse-msg defn (if key-locus
 837                                           (format " (found in %s)" key-locus)
 838                                         "")))
 839         (describe-function-1 defn)
 840         (when up-event
 841           (unless (or (null defn-up)
 842                       (integerp defn-up)
 843                       (equal defn-up 'undefined))
 844             (princ (format "
 845
 846 ----------------- up-event %s----------------
 847
 848 %s%s%s runs the command %S%s, which is "
 849                            (if mouse-1-tricky "(short click) " "")
 850                            (key-description (vector up-event))
 851                            mouse-msg
 852                            (if mouse-1-remapped
 853                                " is remapped to <mouse-2>, which" "")
 854                            defn-up (if key-locus-up
 855                                        (format " (found in %s)" key-locus-up)
 856                                      "")))
 857             (describe-function-1 defn-up))
 858           (unless (or (null defn-up-tricky)
 859                       (integerp defn-up-tricky)
 860                       (eq defn-up-tricky 'undefined))
 861             (princ (format "
 862
 863 ----------------- up-event (long click) ----------------
 864
 865 Pressing <%S>%s for longer than %d milli-seconds
 866 runs the command %S%s, which is "
 867                            ev-type mouse-msg
 868                            mouse-1-click-follows-link
 869                            defn-up-tricky (if key-locus-up-tricky
 870                                               (format " (found in %s)" key-locus-up-tricky)
 871                                             "")))
 872             (describe-function-1 defn-up-tricky)))))))
 873 \f
 874 (defun describe-mode (&optional buffer)
 875   "Display documentation of current major mode and minor modes.
 876 A brief summary of the minor modes comes first, followed by the
 877 major mode description.  This is followed by detailed
 878 descriptions of the minor modes, each on a separate page.
 879
 880 For this to work correctly for a minor mode, the mode's indicator
 881 variable \(listed in `minor-mode-alist') must also be a function
 882 whose documentation describes the minor mode.
 883
 884 If called from Lisp with a non-nil BUFFER argument, display
 885 documentation for the major and minor modes of that buffer."
 886   (interactive "@")
 887   (unless buffer (setq buffer (current-buffer)))
 888   (help-setup-xref (list #'describe-mode buffer)
 889                    (called-interactively-p 'interactive))
 890   ;; For the sake of help-do-xref and help-xref-go-back,
 891   ;; don't switch buffers before calling `help-buffer'.
 892   (with-help-window (help-buffer)
 893     (with-current-buffer buffer
 894       (let (minor-modes)
 895         ;; Older packages do not register in minor-mode-list but only in
 896         ;; minor-mode-alist.
 897         (dolist (x minor-mode-alist)
 898           (setq x (car x))
 899           (unless (memq x minor-mode-list)
 900             (push x minor-mode-list)))
 901         ;; Find enabled minor mode we will want to mention.
 902         (dolist (mode minor-mode-list)
 903           ;; Document a minor mode if it is listed in minor-mode-alist,
 904           ;; non-nil, and has a function definition.
 905           (let ((fmode (or (get mode :minor-mode-function) mode)))
 906             (and (boundp mode) (symbol-value mode)
 907                  (fboundp fmode)
 908                  (let ((pretty-minor-mode
 909                         (if (string-match "\\(\\(-minor\\)?-mode\\)?\\'"
 910                                           (symbol-name fmode))
 911                             (capitalize
 912                              (substring (symbol-name fmode)
 913                                         0 (match-beginning 0)))
 914                           fmode)))
 915                    (push (list fmode pretty-minor-mode
 916                                (format-mode-line (assq mode minor-mode-alist)))
 917                          minor-modes)))))
 918         (setq minor-modes
 919               (sort minor-modes
 920                     (lambda (a b) (string-lessp (cadr a) (cadr b)))))
 921         (when minor-modes
 922           (princ "Enabled minor modes:\n")
 923           (make-local-variable 'help-button-cache)
 924           (with-current-buffer standard-output
 925             (dolist (mode minor-modes)
 926               (let ((mode-function (nth 0 mode))
 927                     (pretty-minor-mode (nth 1 mode))
 928                     (indicator (nth 2 mode)))
 929                 (add-text-properties 0 (length pretty-minor-mode)
 930                                      '(face bold) pretty-minor-mode)
 931                 (save-excursion
 932                   (goto-char (point-max))
 933                   (princ "\n\f\n")
 934                   (push (point-marker) help-button-cache)
 935                   ;; Document the minor modes fully.
 936                   (insert pretty-minor-mode)
 937                   (princ (format " minor mode (%s):\n"
 938                                  (if (zerop (length indicator))
 939                                      "no indicator"
 940                                    (format "indicator%s"
 941                                            indicator))))
 942                   (princ (documentation mode-function)))
 943                 (insert-button pretty-minor-mode
 944                                'action (car help-button-cache)
 945                                'follow-link t
 946                                'help-echo "mouse-2, RET: show full information")
 947                 (newline)))
 948             (forward-line -1)
 949             (fill-paragraph nil)
 950             (forward-line 1))
 951
 952           (princ "\n(Information about these minor modes follows the major mode info.)\n\n"))
 953         ;; Document the major mode.
 954         (let ((mode mode-name))
 955           (with-current-buffer standard-output
 956             (let ((start (point)))
 957               (insert (format-mode-line mode nil nil buffer))
 958               (add-text-properties start (point) '(face bold)))))
 959         (princ " mode")
 960         (let* ((mode major-mode)
 961                (file-name (find-lisp-object-file-name mode nil)))
 962           (when file-name
 963             (princ (concat " defined in `" (file-name-nondirectory file-name) "'"))
 964             ;; Make a hyperlink to the library.
 965             (with-current-buffer standard-output
 966               (save-excursion
 967                 (re-search-backward "`\\([^`']+\\)'" nil t)
 968                 (help-xref-button 1 'help-function-def mode file-name)))))
 969         (princ ":\n")
 970         (princ (documentation major-mode)))))
 971   ;; For the sake of IELM and maybe others
 972   nil)
 973
 974
 975 (defun describe-minor-mode (minor-mode)
 976   "Display documentation of a minor mode given as MINOR-MODE.
 977 MINOR-MODE can be a minor mode symbol or a minor mode indicator string
 978 appeared on the mode-line."
 979   (interactive (list (completing-read
 980                       "Minor mode: "
 981                               (nconc
 982                                (describe-minor-mode-completion-table-for-symbol)
 983                                (describe-minor-mode-completion-table-for-indicator)
 984                                ))))
 985   (if (symbolp minor-mode)
 986       (setq minor-mode (symbol-name minor-mode)))
 987   (let ((symbols (describe-minor-mode-completion-table-for-symbol))
 988         (indicators (describe-minor-mode-completion-table-for-indicator)))
 989     (cond
 990      ((member minor-mode symbols)
 991       (describe-minor-mode-from-symbol (intern minor-mode)))
 992      ((member minor-mode indicators)
 993       (describe-minor-mode-from-indicator minor-mode))
 994      (t
 995       (error "No such minor mode: %s" minor-mode)))))
 996
 997 ;; symbol
 998 (defun describe-minor-mode-completion-table-for-symbol ()
 999   ;; In order to list up all minor modes, minor-mode-list
1000   ;; is used here instead of minor-mode-alist.
1001   (delq nil (mapcar 'symbol-name minor-mode-list)))
1002
1003 (defun describe-minor-mode-from-symbol (symbol)
1004   "Display documentation of a minor mode given as a symbol, SYMBOL"
1005   (interactive (list (intern (completing-read
1006                               "Minor mode symbol: "
1007                               (describe-minor-mode-completion-table-for-symbol)))))
1008   (if (fboundp symbol)
1009       (describe-function symbol)
1010     (describe-variable symbol)))
1011
1012 ;; indicator
1013 (defun describe-minor-mode-completion-table-for-indicator ()
1014   (delq nil
1015         (mapcar (lambda (x)
1016                   (let ((i (format-mode-line x)))
1017                     ;; remove first space if existed
1018                     (cond
1019                      ((= 0 (length i))
1020                       nil)
1021                      ((eq (aref i 0) ?\s)
1022                       (substring i 1))
1023                      (t
1024                       i))))
1025                 minor-mode-alist)))
1026
1027 (defun describe-minor-mode-from-indicator (indicator)
1028   "Display documentation of a minor mode specified by INDICATOR.
1029 If you call this function interactively, you can give indicator which
1030 is currently activated with completion."
1031   (interactive (list
1032                 (completing-read
1033                  "Minor mode indicator: "
1034                  (describe-minor-mode-completion-table-for-indicator))))
1035   (let ((minor-mode (lookup-minor-mode-from-indicator indicator)))
1036     (if minor-mode
1037         (describe-minor-mode-from-symbol minor-mode)
1038       (error "Cannot find minor mode for `%s'" indicator))))
1039
1040 (defun lookup-minor-mode-from-indicator (indicator)
1041   "Return a minor mode symbol from its indicator on the mode line."
1042   ;; remove first space if existed
1043   (if (and (< 0 (length indicator))
1044            (eq (aref indicator 0) ?\s))
1045       (setq indicator (substring indicator 1)))
1046   (let ((minor-modes minor-mode-alist)
1047         result)
1048     (while minor-modes
1049       (let* ((minor-mode (car (car minor-modes)))
1050              (anindicator (format-mode-line
1051                            (car (cdr (car minor-modes))))))
1052         ;; remove first space if existed
1053         (if (and (stringp anindicator)
1054                  (> (length anindicator) 0)
1055                  (eq (aref anindicator 0) ?\s))
1056             (setq anindicator (substring anindicator 1)))
1057         (if (equal indicator anindicator)
1058             (setq result minor-mode
1059                   minor-modes nil)
1060           (setq minor-modes (cdr minor-modes)))))
1061     result))
1062 \f
1063 ;;; Automatic resizing of temporary buffers.
1064 (defcustom temp-buffer-max-height
1065   (lambda (buffer)
1066     (if (eq (selected-window) (frame-root-window))
1067         (/ (x-display-pixel-height) (frame-char-height) 2)
1068       (/ (- (frame-height) 2) 2)))
1069   "Maximum height of a window displaying a temporary buffer.
1070 This is effective only when Temp Buffer Resize mode is enabled.
1071 The value is the maximum height (in lines) which
1072 `resize-temp-buffer-window' will give to a window displaying a
1073 temporary buffer.  It can also be a function to be called to
1074 choose the height for such a buffer.  It gets one argument, the
1075 buffer, and should return a positive integer.  At the time the
1076 function is called, the window to be resized is selected."
1077   :type '(choice integer function)
1078   :group 'help
1079   :version "24.3")
1080
1081 (defcustom temp-buffer-max-width
1082   (lambda (buffer)
1083     (if (eq (selected-window) (frame-root-window))
1084         (/ (x-display-pixel-width) (frame-char-width) 2)
1085       (/ (- (frame-width) 2) 2)))
1086   "Maximum width of a window displaying a temporary buffer.
1087 This is effective only when Temp Buffer Resize mode is enabled.
1088 The value is the maximum width (in columns) which
1089 `resize-temp-buffer-window' will give to a window displaying a
1090 temporary buffer.  It can also be a function to be called to
1091 choose the width for such a buffer.  It gets one argument, the
1092 buffer, and should return a positive integer.  At the time the
1093 function is called, the window to be resized is selected."
1094   :type '(choice integer function)
1095   :group 'help
1096   :version "24.4")
1097
1098 (define-minor-mode temp-buffer-resize-mode
1099   "Toggle auto-resizing temporary buffer windows (Temp Buffer Resize Mode).
1100 With a prefix argument ARG, enable Temp Buffer Resize mode if ARG
1101 is positive, and disable it otherwise.  If called from Lisp,
1102 enable the mode if ARG is omitted or nil.
1103
1104 When Temp Buffer Resize mode is enabled, the windows in which we
1105 show a temporary buffer are automatically resized in height to
1106 fit the buffer's contents, but never more than
1107 `temp-buffer-max-height' nor less than `window-min-height'.
1108
1109 A window is resized only if it has been specially created for the
1110 buffer.  Windows that have shown another buffer before are not
1111 resized.  A frame is resized only if `fit-frame-to-buffer' is
1112 non-nil.
1113
1114 This mode is used by `help', `apropos' and `completion' buffers,
1115 and some others."
1116   :global t :group 'help
1117   (if temp-buffer-resize-mode
1118       ;; `help-make-xrefs' may add a `back' button and thus increase the
1119       ;; text size, so `resize-temp-buffer-window' must be run *after* it.
1120       (add-hook 'temp-buffer-show-hook 'resize-temp-buffer-window 'append)
1121     (remove-hook 'temp-buffer-show-hook 'resize-temp-buffer-window)))
1122
1123 (defun resize-temp-buffer-window (&optional window)
1124   "Resize WINDOW to fit its contents.
1125 WINDOW must be a live window and defaults to the selected one.
1126 Do not resize if WINDOW was not created by `display-buffer'.
1127
1128 If WINDOW is part of a vertical combination, restrain its new
1129 size by `temp-buffer-max-height' and do not resize if its minimum
1130 accessible position is scrolled out of view.  If WINDOW is part
1131 of a horizontal combination, restrain its new size by
1132 `temp-buffer-max-width'.  In both cases, the value of the option
1133 `fit-window-to-buffer-horizontally' can inhibit resizing.
1134
1135 If WINDOW is the root window of its frame, resize the frame
1136 provided `fit-frame-to-buffer' is non-nil.
1137
1138 This function may call `preserve-window-size' to preserve the
1139 size of WINDOW."
1140   (setq window (window-normalize-window window t))
1141   (let ((height (if (functionp temp-buffer-max-height)
1142                     (with-selected-window window
1143                       (funcall temp-buffer-max-height (window-buffer)))
1144                   temp-buffer-max-height))
1145         (width (if (functionp temp-buffer-max-width)
1146                    (with-selected-window window
1147                      (funcall temp-buffer-max-width (window-buffer)))
1148                  temp-buffer-max-width))
1149         (quit-cadr (cadr (window-parameter window 'quit-restore))))
1150     ;; Resize WINDOW iff it was made by `display-buffer'.
1151     (when (or (and (eq quit-cadr 'window)
1152                    (or (and (window-combined-p window)
1153                             (not (eq fit-window-to-buffer-horizontally
1154                                      'only))
1155                             (pos-visible-in-window-p (point-min) window))
1156                        (and (window-combined-p window t)
1157                             fit-window-to-buffer-horizontally)))
1158               (and (eq quit-cadr 'frame)
1159                      fit-frame-to-buffer
1160                      (eq window (frame-root-window window))))
1161         (fit-window-to-buffer window height nil width nil t))))
1162
1163 ;;; Help windows.
1164 (defcustom help-window-select nil
1165   "Non-nil means select help window for viewing.
1166 Choices are:
1167
1168  never (nil) Select help window only if there is no other window
1169              on its frame.
1170
1171  other       Select help window if and only if it appears on the
1172              previously selected frame, that frame contains at
1173              least two other windows and the help window is
1174              either new or showed a different buffer before.
1175
1176  always (t)  Always select the help window.
1177
1178 If this option is non-nil and the help window appears on another
1179 frame, then give that frame input focus too.  Note also that if
1180 the help window appears on another frame, it may get selected and
1181 its frame get input focus even if this option is nil.
1182
1183 This option has effect if and only if the help window was created
1184 by `with-help-window'."
1185   :type '(choice (const :tag "never (nil)" nil)
1186                  (const :tag "other" other)
1187                  (const :tag "always (t)" t))
1188   :group 'help
1189   :version "23.1")
1190
1191 (defcustom help-enable-auto-load t
1192   "Whether Help commands can perform autoloading.
1193 If non-nil, whenever \\[describe-function] is called for an
1194 autoloaded function whose docstring contains any key substitution
1195 construct (see `substitute-command-keys'), the library is loaded,
1196 so that the documentation can show the right key bindings."
1197   :type 'boolean
1198   :group 'help
1199   :version "24.3")
1200
1201 (defun help-window-display-message (quit-part window &optional scroll)
1202   "Display message telling how to quit and scroll help window.
1203 QUIT-PART is a string telling how to quit the help window WINDOW.
1204 Optional argument SCROLL non-nil means tell how to scroll WINDOW.
1205 SCROLL equal `other' means tell how to scroll the \"other\"
1206 window."
1207   (let ((scroll-part
1208          (cond
1209           ;; If we don't have QUIT-PART we probably reuse a window
1210           ;; showing the same buffer so we don't show any message.
1211           ((not quit-part) nil)
1212           ((pos-visible-in-window-p
1213             (with-current-buffer (window-buffer window)
1214               (point-max)) window t)
1215            ;; Buffer end is at least partially visible, no need to talk
1216            ;; about scrolling.
1217            ".")
1218           ((eq scroll 'other)
1219            ", \\[scroll-other-window] to scroll help.")
1220           (scroll ", \\[scroll-up] to scroll help."))))
1221     (message "%s"
1222      (substitute-command-keys (concat quit-part scroll-part)))))
1223
1224 (defun help-window-setup (window &optional value)
1225   "Set up help window WINDOW for `with-help-window'.
1226 WINDOW is the window used for displaying the help buffer.
1227 Return VALUE."
1228   (let* ((help-buffer (when (window-live-p window)
1229                         (window-buffer window)))
1230          (help-setup (when (window-live-p window)
1231                        (car (window-parameter window 'quit-restore))))
1232          (frame (window-frame window)))
1233
1234     (when help-buffer
1235       ;; Handle `help-window-point-marker'.
1236       (when (eq (marker-buffer help-window-point-marker) help-buffer)
1237         (set-window-point window help-window-point-marker)
1238         ;; Reset `help-window-point-marker'.
1239         (set-marker help-window-point-marker nil))
1240
1241       ;; If the help window appears on another frame, select it if
1242       ;; `help-window-select' is non-nil and give that frame input focus
1243       ;; too.  See also Bug#19012.
1244       (when (and help-window-select
1245                  (frame-live-p help-window-old-frame)
1246                  (not (eq frame help-window-old-frame)))
1247         (select-window window)
1248         (select-frame-set-input-focus frame))
1249
1250       (cond
1251        ((or (eq window (selected-window))
1252             ;; If the help window is on the selected frame, select
1253             ;; it if `help-window-select' is t or `help-window-select'
1254             ;; is 'other, the frame contains at least three windows, and
1255             ;; the help window did show another buffer before.  See also
1256             ;; Bug#11039.
1257             (and (eq frame (selected-frame))
1258                  (or (eq help-window-select t)
1259                      (and (eq help-window-select 'other)
1260                           (> (length (window-list nil 'no-mini)) 2)
1261                           (not (eq help-setup 'same))))
1262                  (select-window window)))
1263         ;; The help window is or gets selected ...
1264         (help-window-display-message
1265          (cond
1266           ((eq help-setup 'window)
1267            ;; ... and is new, ...
1268            "Type \"q\" to delete help window")
1269           ((eq help-setup 'frame)
1270            ;; ... on a new frame, ...
1271            "Type \"q\" to quit the help frame")
1272           ((eq help-setup 'other)
1273            ;; ... or displayed some other buffer before.
1274            "Type \"q\" to restore previous buffer"))
1275          window t))
1276        ((and (eq (window-frame window) help-window-old-frame)
1277              (= (length (window-list nil 'no-mini)) 2))
1278         ;; There are two windows on the help window's frame and the
1279         ;; other one is the selected one.
1280         (help-window-display-message
1281          (cond
1282           ((eq help-setup 'window)
1283            "Type \\[delete-other-windows] to delete the help window")
1284           ((eq help-setup 'other)
1285            "Type \"q\" in help window to restore its previous buffer"))
1286          window 'other))
1287        (t
1288         ;; The help window is not selected ...
1289         (help-window-display-message
1290          (cond
1291           ((eq help-setup 'window)
1292            ;; ... and is new, ...
1293            "Type \"q\" in help window to delete it")
1294           ((eq help-setup 'other)
1295            ;; ... or displayed some other buffer before.
1296            "Type \"q\" in help window to restore previous buffer"))
1297          window))))
1298     ;; Return VALUE.
1299     value))
1300
1301 ;; `with-help-window' is a wrapper for `with-temp-buffer-window'
1302 ;; providing the following additional twists:
1303
1304 ;; (1) It puts the buffer in `help-mode' (via `help-mode-setup') and
1305 ;;     adds cross references (via `help-mode-finish').
1306
1307 ;; (2) It issues a message telling how to scroll and quit the help
1308 ;;     window (via `help-window-setup').
1309
1310 ;; (3) An option (customizable via `help-window-select') to select the
1311 ;;     help window automatically.
1312
1313 ;; (4) A marker (`help-window-point-marker') to move point in the help
1314 ;;     window to an arbitrary buffer position.
1315 (defmacro with-help-window (buffer-name &rest body)
1316   "Display buffer named BUFFER-NAME in a help window.
1317 Evaluate the forms in BODY with standard output bound to a buffer
1318 called BUFFER-NAME (creating it if it does not exist), put that
1319 buffer in `help-mode', display the buffer in a window (see
1320 `with-temp-buffer-window' for details) and issue a message how to
1321 deal with that \"help\" window when it's no more needed.  Select
1322 the help window if the current value of the user option
1323 `help-window-select' says so.  Return last value in BODY."
1324   (declare (indent 1) (debug t))
1325   `(progn
1326      ;; Make `help-window-point-marker' point nowhere.  The only place
1327      ;; where this should be set to a buffer position is within BODY.
1328      (set-marker help-window-point-marker nil)
1329      (let ((temp-buffer-window-setup-hook
1330             (cons 'help-mode-setup temp-buffer-window-setup-hook))
1331            (temp-buffer-window-show-hook
1332             (cons 'help-mode-finish temp-buffer-window-show-hook)))
1333        (setq help-window-old-frame (selected-frame))
1334        (with-temp-buffer-window
1335         ,buffer-name nil 'help-window-setup (progn ,@body)))))
1336
1337 ;; Called from C, on encountering `help-char' when reading a char.
1338 ;; Don't print to *Help*; that would clobber Help history.
1339 (defun help-form-show ()
1340   "Display the output of a non-nil `help-form'."
1341   (let ((msg (eval help-form)))
1342     (if (stringp msg)
1343         (with-output-to-temp-buffer " *Char Help*"
1344           (princ msg)))))
1345
1346 \f
1347 ;; The following functions used to be in help-fns.el, which is not preloaded.
1348 ;; But for various reasons, they are more widely needed, so they were
1349 ;; moved to this file, which is preloaded.  http://debbugs.gnu.org/17001
1350
1351 (defun help-split-fundoc (docstring def)
1352   "Split a function DOCSTRING into the actual doc and the usage info.
1353 Return (USAGE . DOC) or nil if there's no usage info, where USAGE info
1354 is a string describing the argument list of DEF, such as
1355 \"(apply FUNCTION &rest ARGUMENTS)\".
1356 DEF is the function whose usage we're looking for in DOCSTRING."
1357   ;; Functions can get the calling sequence at the end of the doc string.
1358   ;; In cases where `function' has been fset to a subr we can't search for
1359   ;; function's name in the doc string so we use `fn' as the anonymous
1360   ;; function name instead.
1361   (when (and docstring (string-match "\n\n(fn\\(\\( .*\\)?)\\)\\'" docstring))
1362     (cons (format "(%s%s"
1363                   ;; Replace `fn' with the actual function name.
1364                   (if (symbolp def) def "anonymous")
1365                   (match-string 1 docstring))
1366           (unless (zerop (match-beginning 0))
1367             (substring docstring 0 (match-beginning 0))))))
1368
1369 (defun help-add-fundoc-usage (docstring arglist)
1370   "Add the usage info to DOCSTRING.
1371 If DOCSTRING already has a usage info, then just return it unchanged.
1372 The usage info is built from ARGLIST.  DOCSTRING can be nil.
1373 ARGLIST can also be t or a string of the form \"(FUN ARG1 ARG2 ...)\"."
1374   (unless (stringp docstring) (setq docstring ""))
1375   (if (or (string-match "\n\n(fn\\(\\( .*\\)?)\\)\\'" docstring)
1376           (eq arglist t))
1377       docstring
1378     (concat docstring
1379             (if (string-match "\n?\n\\'" docstring)
1380                 (if (< (- (match-end 0) (match-beginning 0)) 2) "\n" "")
1381               "\n\n")
1382             (if (and (stringp arglist)
1383                      (string-match "\\`([^ ]+\\(.*\\))\\'" arglist))
1384                 (concat "(fn" (match-string 1 arglist) ")")
1385               (format "%S" (help-make-usage 'fn arglist))))))
1386
1387 (defun help-function-arglist (def &optional preserve-names)
1388   "Return a formal argument list for the function DEF.
1389 IF PRESERVE-NAMES is non-nil, return a formal arglist that uses
1390 the same names as used in the original source code, when possible."
1391   ;; Handle symbols aliased to other symbols.
1392   (if (and (symbolp def) (fboundp def)) (setq def (indirect-function def)))
1393   ;; If definition is a macro, find the function inside it.
1394   (if (eq (car-safe def) 'macro) (setq def (cdr def)))
1395   (cond
1396    ((and (byte-code-function-p def) (listp (aref def 0))) (aref def 0))
1397    ((eq (car-safe def) 'lambda) (nth 1 def))
1398    ((eq (car-safe def) 'closure) (nth 2 def))
1399    ((or (and (byte-code-function-p def) (integerp (aref def 0)))
1400         (subrp def))
1401     (or (when preserve-names
1402           (let* ((doc (condition-case nil (documentation def) (error nil)))
1403                  (docargs (if doc (car (help-split-fundoc doc nil))))
1404                  (arglist (if docargs
1405                               (cdar (read-from-string (downcase docargs)))))
1406                  (valid t))
1407             ;; Check validity.
1408             (dolist (arg arglist)
1409               (unless (and (symbolp arg)
1410                            (let ((name (symbol-name arg)))
1411                              (if (eq (aref name 0) ?&)
1412                                  (memq arg '(&rest &optional))
1413                                (not (string-match "\\." name)))))
1414                 (setq valid nil)))
1415             (when valid arglist)))
1416         (let* ((args-desc (if (not (subrp def))
1417                               (aref def 0)
1418                             (let ((a (subr-arity def)))
1419                               (logior (car a)
1420                                       (if (numberp (cdr a))
1421                                           (lsh (cdr a) 8)
1422                                         (lsh 1 7))))))
1423                (max (lsh args-desc -8))
1424                (min (logand args-desc 127))
1425                (rest (logand args-desc 128))
1426                (arglist ()))
1427           (dotimes (i min)
1428             (push (intern (concat "arg" (number-to-string (1+ i)))) arglist))
1429           (when (> max min)
1430             (push '&optional arglist)
1431             (dotimes (i (- max min))
1432               (push (intern (concat "arg" (number-to-string (+ 1 i min))))
1433                     arglist)))
1434           (unless (zerop rest) (push '&rest arglist) (push 'rest arglist))
1435           (nreverse arglist))))
1436    ((and (autoloadp def) (not (eq (nth 4 def) 'keymap)))
1437     "[Arg list not available until function definition is loaded.]")
1438    (t t)))
1439
1440 (defun help-make-usage (function arglist)
1441   (cons (if (symbolp function) function 'anonymous)
1442         (mapcar (lambda (arg)
1443                   (if (not (symbolp arg)) arg
1444                     (let ((name (symbol-name arg)))
1445                       (cond
1446                        ((string-match "\\`&" name) arg)
1447                        ((string-match "\\`_" name)
1448                         (intern (upcase (substring name 1))))
1449                        (t (intern (upcase name)))))))
1450                 arglist)))
1451
1452 \f
1453 (provide 'help)
1454
1455 ;;; help.el ends here