lisp/help.el

   1 ;;; help.el --- help commands for Emacs
   2
   3 ;; Copyright (C) 1985, 1986, 1993, 1994, 1998, 1999, 2000, 2001, 2002,
   4 ;;   2003, 2004, 2005 Free Software Foundation, Inc.
   5
   6 ;; Maintainer: FSF
   7 ;; Keywords: help, internal
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software; you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation; either version 2, or (at your option)
  14 ;; any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  23 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  24 ;; Boston, MA 02110-1301, USA.
  25
  26 ;;; Commentary:
  27
  28 ;; This code implements GNU Emacs' on-line help system, the one invoked by
  29 ;; `M-x help-for-help'.
  30
  31 ;;; Code:
  32
  33 ;; Get the macro make-help-screen when this is compiled,
  34 ;; or run interpreted, but not when the compiled code is loaded.
  35 (eval-when-compile (require 'help-macro))
  36
  37 ;; This makes `with-output-to-temp-buffer' buffers use `help-mode'.
  38 (add-hook 'temp-buffer-setup-hook 'help-mode-setup)
  39 (add-hook 'temp-buffer-show-hook 'help-mode-finish)
  40
  41 (defvar help-map
  42   (let ((map (make-sparse-keymap)))
  43     (define-key map (char-to-string help-char) 'help-for-help)
  44     (define-key map [help] 'help-for-help)
  45     (define-key map [f1] 'help-for-help)
  46     (define-key map "." 'display-local-help)
  47     (define-key map "?" 'help-for-help)
  48
  49     (define-key map "\C-c" 'describe-copying)
  50     (define-key map "\C-d" 'describe-distribution)
  51     (define-key map "\C-e" 'view-emacs-problems)
  52     (define-key map "\C-f" 'view-emacs-FAQ)
  53     (define-key map "\C-m" 'view-order-manuals)
  54     (define-key map "\C-n" 'view-emacs-news)
  55     (define-key map "\C-p" 'describe-project)
  56     (define-key map "\C-t" 'view-todo)
  57     (define-key map "\C-w" 'describe-no-warranty)
  58
  59     ;; This does not fit the pattern, but it is natural given the C-\ command.
  60     (define-key map "\C-\\" 'describe-input-method)
  61
  62     (define-key map "C" 'describe-coding-system)
  63     (define-key map "F" 'Info-goto-emacs-command-node)
  64     (define-key map "I" 'describe-input-method)
  65     (define-key map "K" 'Info-goto-emacs-key-command-node)
  66     (define-key map "L" 'describe-language-environment)
  67     (define-key map "S" 'info-lookup-symbol)
  68
  69     (define-key map "a" 'apropos-command)
  70     (define-key map "b" 'describe-bindings)
  71     (define-key map "c" 'describe-key-briefly)
  72     (define-key map "d" 'apropos-documentation)
  73     (define-key map "e" 'view-echo-area-messages)
  74     (define-key map "f" 'describe-function)
  75     (define-key map "h" 'view-hello-file)
  76
  77     (define-key map "i" 'info)
  78     (define-key map "4i" 'info-other-window)
  79
  80     (define-key map "k" 'describe-key)
  81     (define-key map "l" 'view-lossage)
  82     (define-key map "m" 'describe-mode)
  83     (define-key map "n" 'view-emacs-news)
  84     (define-key map "p" 'finder-by-keyword)
  85     (define-key map "r" 'info-emacs-manual)
  86     (define-key map "s" 'describe-syntax)
  87     (define-key map "t" 'help-with-tutorial)
  88     (define-key map "w" 'where-is)
  89     (define-key map "v" 'describe-variable)
  90     (define-key map "q" 'help-quit)
  91     map)
  92   "Keymap for characters following the Help key.")
  93
  94 (define-key global-map (char-to-string help-char) 'help-command)
  95 (define-key global-map [help] 'help-command)
  96 (define-key global-map [f1] 'help-command)
  97 (fset 'help-command help-map)
  98
  99 (autoload 'finder-by-keyword "finder"
 100   "Find packages matching a given keyword." t)
 101
 102 ;; insert-button makes the action nil if it is not store somewhere
 103 (defvar help-button-cache nil)
 104
 105 \f
 106 (defun help-quit ()
 107   "Just exit from the Help command's command loop."
 108   (interactive)
 109   nil)
 110
 111 (defvar help-return-method nil
 112   "What to do to \"exit\" the help buffer.
 113 This is a list
 114  (WINDOW . t)              delete the selected window (and possibly its frame,
 115                            see `quit-window' and `View-quit'), go to WINDOW.
 116  (WINDOW . quit-window)    do quit-window, then select WINDOW.
 117  (WINDOW BUF START POINT)  display BUF at START, POINT, then select WINDOW.")
 118
 119 (defun print-help-return-message (&optional function)
 120   "Display or return message saying how to restore windows after help command.
 121 This function assumes that `standard-output' is the help buffer.
 122 It computes a message, and applies the optional argument FUNCTION to it.
 123 If FUNCTION is nil, it applies `message', thus displaying the message.
 124 In addition, this function sets up `help-return-method', which see, that
 125 specifies what to do when the user exits the help buffer."
 126   (and (not (get-buffer-window standard-output))
 127        (let ((first-message
 128               (cond ((or
 129                       pop-up-frames
 130                       (special-display-p (buffer-name standard-output)))
 131                      (setq help-return-method (cons (selected-window) t))
 132                      ;; If the help output buffer is a special display buffer,
 133                      ;; don't say anything about how to get rid of it.
 134                      ;; First of all, the user will do that with the window
 135                      ;; manager, not with Emacs.
 136                      ;; Secondly, the buffer has not been displayed yet,
 137                      ;; so we don't know whether its frame will be selected.
 138                      nil)
 139                     (display-buffer-reuse-frames
 140                      (setq help-return-method (cons (selected-window)
 141                                                     'quit-window))
 142                      nil)
 143                     ((not (one-window-p t))
 144                      (setq help-return-method
 145                            (cons (selected-window) 'quit-window))
 146                      "Type \\[switch-to-buffer-other-window] RET to restore the other window.")
 147                     (pop-up-windows
 148                      (setq help-return-method (cons (selected-window) t))
 149                      "Type \\[delete-other-windows] to remove help window.")
 150                     (t
 151                      (setq help-return-method
 152                            (list (selected-window) (window-buffer)
 153                                  (window-start) (window-point)))
 154                      "Type \\[switch-to-buffer] RET to remove help window."))))
 155          (funcall (or function 'message)
 156                   (concat
 157                    (if first-message
 158                        (substitute-command-keys first-message))
 159                    (if first-message "  ")
 160                    ;; If the help buffer will go in a separate frame,
 161                    ;; it's no use mentioning a command to scroll, so don't.
 162                    (if (or pop-up-windows
 163                            (special-display-p (buffer-name standard-output)))
 164                        nil
 165                      (if (same-window-p (buffer-name standard-output))
 166                          ;; Say how to scroll this window.
 167                          (substitute-command-keys
 168                           "\\[scroll-up] to scroll the help.")
 169                        ;; Say how to scroll some other window.
 170                        (substitute-command-keys
 171                         "\\[scroll-other-window] to scroll the help."))))))))
 172
 173 ;; So keyboard macro definitions are documented correctly
 174 (fset 'defining-kbd-macro (symbol-function 'start-kbd-macro))
 175
 176 (defalias 'help 'help-for-help-internal)
 177 ;; find-function can find this.
 178 (defalias 'help-for-help 'help-for-help-internal)
 179 ;; It can't find this, but nobody will look.
 180 (make-help-screen help-for-help-internal
 181   "a b c C e f F i I k C-k l L m p s t v w C-c C-d C-f C-n C-p C-t C-w . or ? :"
 182   "You have typed %THIS-KEY%, the help character.  Type a Help option:
 183 \(Use SPC or DEL to scroll through this text.  Type \\<help-map>\\[help-quit] to exit the Help command.)
 184
 185 a  command-apropos.  Give a list of words or a regexp, to get a list of
 186         commands whose names match (they contain two or more of the words,
 187         or a match for the regexp).  See also the  apropos  command.
 188 b  describe-bindings.  Display table of all key bindings.
 189 c  describe-key-briefly.  Type a command key sequence;
 190         it prints the function name that sequence runs.
 191 C  describe-coding-system.  This describes either a specific coding system
 192         (if you type its name) or the coding systems currently in use
 193         (if you type just RET).
 194 d  apropos-documentation.  Give a pattern (a list or words or a regexp), and
 195         see a list of functions, variables, and other items whose built-in
 196         doucmentation string matches that pattern.  See also the apropos command.
 197 e  view-echo-area-messages.  Show the buffer where the echo-area messages
 198         are stored.
 199 f  describe-function.  Type a function name and get its documentation.
 200 F  Info-goto-emacs-command-node.  Type a function name;
 201         it takes you to the on-line manual's section that describes
 202         the command.
 203 h  Display the HELLO file which illustrates various scripts.
 204 i  info. The Info documentation reader: read on-line manuals.
 205 I  describe-input-method.  Describe a specific input method (if you type
 206         its name) or the current input method (if you type just RET).
 207 k  describe-key.  Type a command key sequence;
 208         it displays the full documentation for that key sequence.
 209 K Info-goto-emacs-key-command-node.  Type a command key sequence;
 210         it takes you to the on-line manual's section that describes
 211         the command bound to that key.
 212 l  view-lossage.  Show last 100 characters you typed.
 213 L  describe-language-environment.  This describes either a
 214         specific language environment (if you type its name)
 215         or the current language environment (if you type just RET).
 216 m  describe-mode.  Display documentation of current minor modes,
 217         and the current major mode, including their special commands.
 218 n  view-emacs-news.  Display news of recent Emacs changes.
 219 p  finder-by-keyword. Find packages matching a given topic keyword.
 220 s  describe-syntax.  Display contents of syntax table, plus explanations.
 221 S  info-lookup-symbol.  Display the definition of a specific symbol
 222         as found in the manual for the language this buffer is written in.
 223 t  help-with-tutorial.  Select the Emacs learn-by-doing tutorial.
 224 v  describe-variable.  Type name of a variable;
 225         it displays the variable's documentation and value.
 226 w  where-is.  Type command name; it prints which keystrokes
 227         invoke that command.
 228 .  display-local-help.  Display any available local help at point
 229         in the echo area.
 230
 231 C-c Display Emacs copying permission (GNU General Public License).
 232 C-d Display Emacs ordering information.
 233 C-e Display info about Emacs problems.
 234 C-f Display the Emacs FAQ.
 235 C-m Display how to order printed Emacs manuals.
 236 C-n Display news of recent Emacs changes.
 237 C-p Display information about the GNU project.
 238 C-t Display the Emacs TODO list.
 239 C-w Display information on absence of warranty for GNU Emacs."
 240   help-map)
 241
 242 \f
 243
 244 (defun function-called-at-point ()
 245   "Return a function around point or else called by the list containing point.
 246 If that doesn't give a function, return nil."
 247   (or (with-syntax-table emacs-lisp-mode-syntax-table
 248         (or (condition-case ()
 249                 (save-excursion
 250                   (or (not (zerop (skip-syntax-backward "_w")))
 251                       (eq (char-syntax (following-char)) ?w)
 252                       (eq (char-syntax (following-char)) ?_)
 253                       (forward-sexp -1))
 254                   (skip-chars-forward "'")
 255                   (let ((obj (read (current-buffer))))
 256                     (and (symbolp obj) (fboundp obj) obj)))
 257               (error nil))
 258             (condition-case ()
 259                 (save-excursion
 260                   (save-restriction
 261                     (narrow-to-region (max (point-min)
 262                                            (- (point) 1000)) (point-max))
 263                     ;; Move up to surrounding paren, then after the open.
 264                     (backward-up-list 1)
 265                     (forward-char 1)
 266                     ;; If there is space here, this is probably something
 267                     ;; other than a real Lisp function call, so ignore it.
 268                     (if (looking-at "[ \t]")
 269                         (error "Probably not a Lisp function call"))
 270                     (let ((obj (read (current-buffer))))
 271                       (and (symbolp obj) (fboundp obj) obj))))
 272               (error nil))))
 273       (let* ((str (find-tag-default))
 274              (sym (if str (intern-soft str))))
 275         (if (and sym (fboundp sym))
 276             sym
 277           (save-match-data
 278             (when (and str (string-match "\\`\\W*\\(.*?\\)\\W*\\'" str))
 279               (setq sym (intern-soft (match-string 1 str)))
 280               (and (fboundp sym) sym)))))))
 281
 282 \f
 283 ;;; `User' help functions
 284
 285 (defun describe-distribution ()
 286   "Display info on how to obtain the latest version of GNU Emacs."
 287   (interactive)
 288   (view-file (expand-file-name "DISTRIB" data-directory)))
 289
 290 (defun describe-copying ()
 291   "Display info on how you may redistribute copies of GNU Emacs."
 292   (interactive)
 293   (view-file (expand-file-name "COPYING" data-directory))
 294   (goto-char (point-min)))
 295
 296 (defun describe-project ()
 297   "Display info on the GNU project."
 298   (interactive)
 299   (view-file (expand-file-name "THE-GNU-PROJECT" data-directory))
 300   (goto-char (point-min)))
 301
 302 (defun describe-no-warranty ()
 303   "Display info on all the kinds of warranty Emacs does NOT have."
 304   (interactive)
 305   (describe-copying)
 306   (let (case-fold-search)
 307     (search-forward "NO WARRANTY")
 308     (recenter 0)))
 309
 310 (defun describe-prefix-bindings ()
 311   "Describe the bindings of the prefix used to reach this command.
 312 The prefix described consists of all but the last event
 313 of the key sequence that ran this command."
 314   (interactive)
 315   (let* ((key (this-command-keys)))
 316     (describe-bindings
 317      (if (stringp key)
 318          (substring key 0 (1- (length key)))
 319        (let ((prefix (make-vector (1- (length key)) nil))
 320              (i 0))
 321          (while (< i (length prefix))
 322            (aset prefix i (aref key i))
 323            (setq i (1+ i)))
 324          prefix)))))
 325 ;; Make C-h after a prefix, when not specifically bound,
 326 ;; run describe-prefix-bindings.
 327 (setq prefix-help-command 'describe-prefix-bindings)
 328
 329 (defun view-emacs-news (&optional arg)
 330   "Display info on recent changes to Emacs.
 331 With argument, display info only for the selected version."
 332   (interactive "P")
 333   (if (not arg)
 334       (view-file (expand-file-name "NEWS" data-directory))
 335     (let* ((map (sort
 336                  (delete-dups
 337                   (apply
 338                    'nconc
 339                    (mapcar
 340                     (lambda (file)
 341                       (with-temp-buffer
 342                         (insert-file-contents
 343                          (expand-file-name file data-directory))
 344                         (let (res)
 345                           (while (re-search-forward
 346                                   (if (string-match "^ONEWS\\.[0-9]+$" file)
 347                                       "Changes in \\(?:Emacs\\|version\\)?[ \t]*\\([0-9]+\\(?:\\.[0-9]+\\)?\\)"
 348                                     "^\* [^0-9\n]*\\([0-9]+\\.[0-9]+\\)") nil t)
 349                             (setq res (cons (list (match-string-no-properties 1)
 350                                                   file) res)))
 351                           res)))
 352                     (append '("NEWS" "ONEWS")
 353                             (directory-files data-directory nil
 354                                              "^ONEWS\\.[0-9]+$" nil)))))
 355                  (lambda (a b)
 356                    (string< (car b) (car a)))))
 357            (current (caar map))
 358            (version (completing-read
 359                      (format "Read NEWS for the version (default %s): " current)
 360                      (mapcar 'car map) nil nil nil nil current))
 361            (file (cadr (assoc version map)))
 362            res)
 363       (if (not file)
 364           (error "No news is good news")
 365         (view-file (expand-file-name file data-directory))
 366         (widen)
 367         (goto-char (point-min))
 368         (when (re-search-forward
 369                (concat (if (string-match "^ONEWS\\.[0-9]+$" file)
 370                            "Changes in \\(?:Emacs\\|version\\)?[ \t]*"
 371                          "^\* [^0-9\n]*") version)
 372                nil t)
 373           (beginning-of-line)
 374           (narrow-to-region
 375            (point)
 376            (save-excursion
 377              (while (and (setq res
 378                                (re-search-forward
 379                                 (if (string-match "^ONEWS\\.[0-9]+$" file)
 380                                     "Changes in \\(?:Emacs\\|version\\)?[ \t]*\\([0-9]+\\(?:\\.[0-9]+\\)?\\)"
 381                                   "^\* [^0-9\n]*\\([0-9]+\\.[0-9]+\\)") nil t))
 382                          (equal (match-string-no-properties 1) version)))
 383              (or res (goto-char (point-max)))
 384              (beginning-of-line)
 385              (point))))))))
 386
 387 (defun view-todo (&optional arg)
 388   "Display the Emacs TODO list."
 389   (interactive "P")
 390   (view-file (expand-file-name "TODO" data-directory)))
 391
 392 (defun view-echo-area-messages ()
 393   "View the log of recent echo-area messages: the `*Messages*' buffer.
 394 The number of messages retained in that buffer
 395 is specified by the variable `message-log-max'."
 396   (interactive)
 397   (switch-to-buffer (get-buffer-create "*Messages*")))
 398
 399 (defun view-order-manuals ()
 400   "Display the Emacs ORDERS file."
 401   (interactive)
 402   (view-file (expand-file-name "ORDERS" data-directory))
 403   (goto-address))
 404
 405 (defun view-emacs-FAQ ()
 406   "Display the Emacs Frequently Asked Questions (FAQ) file."
 407   (interactive)
 408   ;; (find-file-read-only (expand-file-name "FAQ" data-directory))
 409   (info "(efaq)"))
 410
 411 (defun view-emacs-problems ()
 412   "Display info on known problems with Emacs and possible workarounds."
 413   (interactive)
 414   (view-file (expand-file-name "PROBLEMS" data-directory)))
 415
 416 (defun view-lossage ()
 417   "Display last 100 input keystrokes.
 418
 419 To record all your input on a file, use `open-dribble-file'."
 420   (interactive)
 421   (help-setup-xref (list #'view-lossage) (interactive-p))
 422   (with-output-to-temp-buffer (help-buffer)
 423     (princ (mapconcat (lambda (key)
 424                         (if (or (integerp key) (symbolp key) (listp key))
 425                             (single-key-description key)
 426                           (prin1-to-string key nil)))
 427                       (recent-keys)
 428                       " "))
 429     (with-current-buffer standard-output
 430       (goto-char (point-min))
 431       (while (progn (move-to-column 50) (not (eobp)))
 432         (search-forward " " nil t)
 433         (insert "\n")))
 434     (print-help-return-message)))
 435
 436 \f
 437 ;; Key bindings
 438
 439 (defun describe-bindings (&optional prefix buffer)
 440   "Show a list of all defined keys, and their definitions.
 441 We put that list in a buffer, and display the buffer.
 442
 443 The optional argument PREFIX, if non-nil, should be a key sequence;
 444 then we display only bindings that start with that prefix.
 445 The optional argument BUFFER specifies which buffer's bindings
 446 to display (default, the current buffer).  BUFFER can be a buffer
 447 or a buffer name."
 448   (interactive)
 449   (or buffer (setq buffer (current-buffer)))
 450   (help-setup-xref (list #'describe-bindings prefix buffer) (interactive-p))
 451   (with-current-buffer buffer
 452     (describe-bindings-internal nil prefix)))
 453
 454 ;; This function used to be in keymap.c.
 455 (defun describe-bindings-internal (&optional menus prefix)
 456   "Show a list of all defined keys, and their definitions.
 457 We put that list in a buffer, and display the buffer.
 458
 459 The optional argument MENUS, if non-nil, says to mention menu bindings.
 460 \(Ordinarily these are omitted from the output.)
 461 The optional argument PREFIX, if non-nil, should be a key sequence;
 462 then we display only bindings that start with that prefix."
 463   (interactive)
 464   (let ((buf (current-buffer)))
 465     (with-output-to-temp-buffer "*Help*"
 466       (with-current-buffer standard-output
 467         (describe-buffer-bindings buf prefix menus)))))
 468
 469 (defun where-is (definition &optional insert)
 470   "Print message listing key sequences that invoke the command DEFINITION.
 471 Argument is a command definition, usually a symbol with a function definition.
 472 If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
 473   (interactive
 474    (let ((fn (function-called-at-point))
 475          (enable-recursive-minibuffers t)
 476          val)
 477      (setq val (completing-read
 478                 (if fn
 479                     (format "Where is command (default %s): " fn)
 480                   "Where is command: ")
 481                 obarray 'commandp t))
 482      (list (if (equal val "") fn (intern val)) current-prefix-arg)))
 483   (let ((func (indirect-function definition))
 484         (defs nil)
 485         (standard-output (if insert (current-buffer) t)))
 486     ;; In DEFS, find all symbols that are aliases for DEFINITION.
 487     (mapatoms (lambda (symbol)
 488                 (and (fboundp symbol)
 489                      (not (eq symbol definition))
 490                      (eq func (condition-case ()
 491                                   (indirect-function symbol)
 492                                 (error symbol)))
 493                      (push symbol defs))))
 494     ;; Look at all the symbols--first DEFINITION,
 495     ;; then its aliases.
 496     (dolist (symbol (cons definition defs))
 497       (let* ((remapped (command-remapping symbol))
 498              (keys (where-is-internal
 499                     symbol overriding-local-map nil nil remapped))
 500              (keys (mapconcat 'key-description keys ", "))
 501              string)
 502         (setq string
 503               (if insert
 504                   (if (> (length keys) 0)
 505                       (if remapped
 506                           (format "%s (%s) (remapped from %s)"
 507                                   keys remapped symbol)
 508                         (format "%s (%s)" keys symbol))
 509                     (format "M-x %s RET" symbol))
 510                 (if (> (length keys) 0)
 511                     (if remapped
 512                         (format "%s is remapped to %s which is on %s"
 513                                 definition symbol keys)
 514                       (format "%s is on %s" symbol keys))
 515                   ;; If this is the command the user asked about,
 516                   ;; and it is not on any key, say so.
 517                   ;; For other symbols, its aliases, say nothing
 518                   ;; about them unless they are on keys.
 519                   (if (eq symbol definition)
 520                       (format "%s is not on any key" symbol)))))
 521         (when string
 522           (unless (eq symbol definition)
 523             (princ ";\n its alias "))
 524           (princ string)))))
 525   nil)
 526
 527 (defun string-key-binding (key)
 528   "Value is the binding of KEY in a string.
 529 If KEY is an event on a string, and that string has a `local-map'
 530 or `keymap' property, return the binding of KEY in the string's keymap."
 531   (let* ((defn nil)
 532          (start (when (vectorp key)
 533                   (if (memq (aref key 0)
 534                             '(mode-line header-line left-margin right-margin))
 535                       (event-start (aref key 1))
 536                     (and (consp (aref key 0))
 537                          (event-start (aref key 0))))))
 538          (string-info (and (consp start) (nth 4 start))))
 539     (when string-info
 540       (let* ((string (car string-info))
 541              (pos (cdr string-info))
 542              (local-map (and (>= pos 0)
 543                              (< pos (length string))
 544                              (or (get-text-property pos 'local-map string)
 545                                  (get-text-property pos 'keymap string)))))
 546         (setq defn (and local-map (lookup-key local-map key)))))
 547     defn))
 548
 549 (defun help-key-description (key untranslated)
 550   (let ((string (key-description key)))
 551     (if (or (not untranslated)
 552             (and (eq (aref untranslated 0) ?\e) (not (eq (aref key 0) ?\e))))
 553         string
 554       (let ((otherstring (key-description untranslated)))
 555         (if (equal string otherstring)
 556             string
 557           (format "%s (translated from %s)" string otherstring))))))
 558
 559 (defun describe-key-briefly (key &optional insert untranslated)
 560   "Print the name of the function KEY invokes.  KEY is a string.
 561 If INSERT (the prefix arg) is non-nil, insert the message in the buffer.
 562 If non-nil UNTRANSLATED is a vector of the untranslated events.
 563 It can also be a number in which case the untranslated events from
 564 the last key hit are used."
 565   (interactive "kDescribe key briefly: \nP\np")
 566   (if (numberp untranslated)
 567       (setq untranslated (this-single-command-raw-keys)))
 568   (save-excursion
 569     (let ((modifiers (event-modifiers (aref key 0)))
 570           (standard-output (if insert (current-buffer) t))
 571           window position)
 572       ;; For a mouse button event, go to the button it applies to
 573       ;; to get the right key bindings.  And go to the right place
 574       ;; in case the keymap depends on where you clicked.
 575       (if (or (memq 'click modifiers) (memq 'down modifiers)
 576               (memq 'drag modifiers))
 577           (setq window (posn-window (event-start (aref key 0)))
 578                 position (posn-point (event-start (aref key 0)))))
 579       (if (windowp window)
 580           (progn
 581             (set-buffer (window-buffer window))
 582             (goto-char position)))
 583       ;; Ok, now look up the key and name the command.
 584       (let ((defn (or (string-key-binding key)
 585                       (key-binding key t)))
 586             key-desc)
 587         ;; Don't bother user with strings from (e.g.) the select-paste menu.
 588         (if (stringp (aref key (1- (length key))))
 589             (aset key (1- (length key)) "(any string)"))
 590         (if (and (> (length untranslated) 0)
 591                  (stringp (aref untranslated (1- (length untranslated)))))
 592             (aset untranslated (1- (length untranslated))
 593                   "(any string)"))
 594         ;; Now describe the key, perhaps as changed.
 595         (setq key-desc (help-key-description key untranslated))
 596         (if (or (null defn) (integerp defn) (equal defn 'undefined))
 597             (princ (format "%s is undefined" key-desc))
 598           (princ (format (if (windowp window)
 599                              "%s at that spot runs the command %s"
 600                            "%s runs the command %s")
 601                          key-desc
 602                          (if (symbolp defn) defn (prin1-to-string defn)))))))))
 603
 604 (defun describe-key (key &optional untranslated up-event)
 605   "Display documentation of the function invoked by KEY.
 606 KEY can be any kind of a key sequence; it can include keyboard events,
 607 mouse events, and/or menu events.  When calling from a program,
 608 pass KEY as a string or a vector.
 609
 610 If non-nil, UNTRANSLATED is a vector of the corresponding untranslated events.
 611 It can also be a number, in which case the untranslated events from
 612 the last key sequence entered are used."
 613   ;; UP-EVENT is the up-event that was discarded by reading KEY, or nil.
 614   (interactive "kDescribe key (or click or menu item): \np\nU")
 615   (if (numberp untranslated)
 616       (setq untranslated (this-single-command-raw-keys)))
 617   (save-excursion
 618     (let ((modifiers (event-modifiers (aref key 0)))
 619           window position)
 620       ;; For a mouse button event, go to the button it applies to
 621       ;; to get the right key bindings.  And go to the right place
 622       ;; in case the keymap depends on where you clicked.
 623       (if (or (memq 'click modifiers) (memq 'down modifiers)
 624               (memq 'drag modifiers))
 625           (setq window (posn-window (event-start (aref key 0)))
 626                 position (posn-point (event-start (aref key 0)))))
 627       (when (windowp window)
 628             (set-buffer (window-buffer window))
 629         (goto-char position))
 630       (let ((defn (or (string-key-binding key) (key-binding key t))))
 631         (if (or (null defn) (integerp defn) (equal defn 'undefined))
 632             (message "%s is undefined" (help-key-description key untranslated))
 633           (help-setup-xref (list #'describe-function defn) (interactive-p))
 634           ;; Don't bother user with strings from (e.g.) the select-paste menu.
 635           (if (stringp (aref key (1- (length key))))
 636               (aset key (1- (length key)) "(any string)"))
 637           (if (and untranslated
 638                    (stringp (aref untranslated (1- (length untranslated)))))
 639               (aset untranslated (1- (length untranslated))
 640                     "(any string)"))
 641           (with-output-to-temp-buffer (help-buffer)
 642             (princ (help-key-description key untranslated))
 643             (if (windowp window)
 644                 (princ " at that spot"))
 645             (princ " runs the command ")
 646             (prin1 defn)
 647             (princ "\n   which is ")
 648             (describe-function-1 defn)
 649             (when up-event
 650               (let ((ev (aref up-event 0))
 651                     (descr (key-description up-event))
 652                     (hdr "\n\n-------------- up event ---------------\n\n")
 653                     defn
 654                     mouse-1-tricky mouse-1-remapped)
 655                 (when (and (consp ev)
 656                            (eq (car ev) 'mouse-1)
 657                            (windowp window)
 658                            mouse-1-click-follows-link
 659                            (not (eq mouse-1-click-follows-link 'double))
 660                            (with-current-buffer (window-buffer window)
 661                              (mouse-on-link-p (posn-point (event-start ev)))))
 662                   (setq mouse-1-tricky (integerp mouse-1-click-follows-link)
 663                         mouse-1-remapped (or (not mouse-1-tricky)
 664                                              (> mouse-1-click-follows-link 0)))
 665                   (if mouse-1-remapped
 666                       (setcar ev 'mouse-2)))
 667                 (setq defn (or (string-key-binding up-event) (key-binding up-event)))
 668                 (unless (or (null defn) (integerp defn) (equal defn 'undefined))
 669                   (princ (if mouse-1-tricky
 670                              "\n\n----------------- up-event (short click) ----------------\n\n"
 671                            hdr))
 672                   (setq hdr nil)
 673                   (princ descr)
 674                   (if (windowp window)
 675                       (princ " at that spot"))
 676                   (if mouse-1-remapped
 677                       (princ " is remapped to <mouse-2>\n  which" ))
 678                   (princ " runs the command ")
 679                   (prin1 defn)
 680                   (princ "\n   which is ")
 681                   (describe-function-1 defn))
 682                 (when mouse-1-tricky
 683                   (setcar ev
 684                           (if (> mouse-1-click-follows-link 0) 'mouse-1 'mouse-2))
 685                   (setq defn (or (string-key-binding up-event) (key-binding up-event)))
 686                   (unless (or (null defn) (integerp defn) (equal defn 'undefined))
 687                     (princ (or hdr
 688                                "\n\n----------------- up-event (long click) ----------------\n\n"))
 689                     (princ "Pressing ")
 690                     (princ descr)
 691                     (if (windowp window)
 692                         (princ " at that spot"))
 693                     (princ (format " for longer than %d milli-seconds\n"
 694                                    (abs mouse-1-click-follows-link)))
 695                     (if (not mouse-1-remapped)
 696                         (princ " remaps it to <mouse-2> which" ))
 697                     (princ " runs the command ")
 698                     (prin1 defn)
 699                     (princ "\n   which is ")
 700                     (describe-function-1 defn)))))
 701             (print-help-return-message)))))))
 702
 703 \f
 704 (defun describe-mode (&optional buffer)
 705   "Display documentation of current major mode and minor modes.
 706 A brief summary of the minor modes comes first, followed by the
 707 major mode description.  This is followed by detailed
 708 descriptions of the minor modes, each on a separate page.
 709
 710 For this to work correctly for a minor mode, the mode's indicator
 711 variable \(listed in `minor-mode-alist') must also be a function
 712 whose documentation describes the minor mode."
 713   (interactive)
 714   (unless buffer (setq buffer (current-buffer)))
 715   (help-setup-xref (list #'describe-mode buffer)
 716                    (interactive-p))
 717   ;; For the sake of help-do-xref and help-xref-go-back,
 718   ;; don't switch buffers before calling `help-buffer'.
 719   (with-output-to-temp-buffer (help-buffer)
 720     (with-current-buffer buffer
 721       (let (minor-modes)
 722         ;; Older packages do not register in minor-mode-list but only in
 723         ;; minor-mode-alist.
 724         (dolist (x minor-mode-alist)
 725           (setq x (car x))
 726           (unless (memq x minor-mode-list)
 727             (push x minor-mode-list)))
 728         ;; Find enabled minor mode we will want to mention.
 729         (dolist (mode minor-mode-list)
 730           ;; Document a minor mode if it is listed in minor-mode-alist,
 731           ;; non-nil, and has a function definition.
 732           (let ((fmode (or (get mode :minor-mode-function) mode)))
 733             (and (boundp mode) (symbol-value mode)
 734                  (fboundp fmode)
 735                  (let ((pretty-minor-mode
 736                         (if (string-match "\\(\\(-minor\\)?-mode\\)?\\'"
 737                                           (symbol-name fmode))
 738                             (capitalize
 739                              (substring (symbol-name fmode)
 740                                         0 (match-beginning 0)))
 741                           fmode)))
 742                    (push (list fmode pretty-minor-mode
 743                                (format-mode-line (assq mode minor-mode-alist)))
 744                          minor-modes)))))
 745         (setq minor-modes
 746               (sort minor-modes
 747                     (lambda (a b) (string-lessp (cadr a) (cadr b)))))
 748         (when minor-modes
 749           (princ "Summary of minor modes:\n")
 750           (make-local-variable 'help-button-cache)
 751           (with-current-buffer standard-output
 752             (dolist (mode minor-modes)
 753               (let ((mode-function (nth 0 mode))
 754                     (pretty-minor-mode (nth 1 mode))
 755                     (indicator (nth 2 mode)))
 756                 (setq indicator (if (zerop (length indicator))
 757                                     "no indicator"
 758                                   (format "indicator%s" indicator)))
 759                 (add-text-properties 0 (length pretty-minor-mode)
 760                                      '(face bold) pretty-minor-mode)
 761                 (save-excursion
 762                   (goto-char (point-max))
 763                   (princ "\n\f\n")
 764                   (push (point-marker) help-button-cache)
 765                   ;; Document the minor modes fully.
 766                   (insert pretty-minor-mode)
 767                   (princ (format " minor mode (%s):\n" indicator))
 768                   (princ (documentation mode-function)))
 769                 (princ "  ")
 770                 (insert-button pretty-minor-mode
 771                                'action (car help-button-cache)
 772                                'follow-link t
 773                                'help-echo "mouse-2, RET: show full information")
 774                 (princ (format " minor mode (%s):\n" indicator)))))
 775           (princ "\n(Full information about these minor modes
 776 follows the description of the major mode.)\n\n"))
 777         ;; Document the major mode.
 778         (let ((mode mode-name))
 779           (with-current-buffer standard-output
 780             (insert mode)
 781             (add-text-properties (- (point) (length mode)) (point) '(face bold))))
 782         (princ " mode:\n")
 783         (princ (documentation major-mode)))
 784       (print-help-return-message))))
 785
 786
 787 (defun describe-minor-mode (minor-mode)
 788   "Display documentation of a minor mode given as MINOR-MODE.
 789 MINOR-MODE can be a minor mode symbol or a minor mode indicator string
 790 appeared on the mode-line."
 791   (interactive (list (completing-read
 792                       "Minor mode: "
 793                               (nconc
 794                                (describe-minor-mode-completion-table-for-symbol)
 795                                (describe-minor-mode-completion-table-for-indicator)
 796                                ))))
 797   (if (symbolp minor-mode)
 798       (setq minor-mode (symbol-name minor-mode)))
 799   (let ((symbols (describe-minor-mode-completion-table-for-symbol))
 800         (indicators (describe-minor-mode-completion-table-for-indicator)))
 801     (cond
 802      ((member minor-mode symbols)
 803       (describe-minor-mode-from-symbol (intern minor-mode)))
 804      ((member minor-mode indicators)
 805       (describe-minor-mode-from-indicator minor-mode))
 806      (t
 807       (error "No such minor mode: %s" minor-mode)))))
 808
 809 ;; symbol
 810 (defun describe-minor-mode-completion-table-for-symbol ()
 811   ;; In order to list up all minor modes, minor-mode-list
 812   ;; is used here instead of minor-mode-alist.
 813   (delq nil (mapcar 'symbol-name minor-mode-list)))
 814 (defun describe-minor-mode-from-symbol (symbol)
 815   "Display documentation of a minor mode given as a symbol, SYMBOL"
 816   (interactive (list (intern (completing-read
 817                               "Minor mode symbol: "
 818                               (describe-minor-mode-completion-table-for-symbol)))))
 819   (if (fboundp symbol)
 820       (describe-function symbol)
 821     (describe-variable symbol)))
 822
 823 ;; indicator
 824 (defun describe-minor-mode-completion-table-for-indicator ()
 825   (delq nil
 826         (mapcar (lambda (x)
 827                   (let ((i (format-mode-line x)))
 828                     ;; remove first space if existed
 829                     (cond
 830                      ((= 0 (length i))
 831                       nil)
 832                      ((eq (aref i 0) ?\ )
 833                       (substring i 1))
 834                      (t
 835                       i))))
 836                 minor-mode-alist)))
 837 (defun describe-minor-mode-from-indicator (indicator)
 838   "Display documentation of a minor mode specified by INDICATOR.
 839 If you call this function interactively, you can give indicator which
 840 is currently activated with completion."
 841   (interactive (list
 842                 (completing-read
 843                  "Minor mode indicator: "
 844                  (describe-minor-mode-completion-table-for-indicator))))
 845   (let ((minor-mode (lookup-minor-mode-from-indicator indicator)))
 846     (if minor-mode
 847         (describe-minor-mode-from-symbol minor-mode)
 848       (error "Cannot find minor mode for `%s'" indicator))))
 849
 850 (defun lookup-minor-mode-from-indicator (indicator)
 851   "Return a minor mode symbol from its indicator on the modeline."
 852   ;; remove first space if existed
 853   (if (and (< 0 (length indicator))
 854            (eq (aref indicator 0) ?\ ))
 855       (setq indicator (substring indicator 1)))
 856   (let ((minor-modes minor-mode-alist)
 857         result)
 858     (while minor-modes
 859       (let* ((minor-mode (car (car minor-modes)))
 860              (anindicator (format-mode-line
 861                            (car (cdr (car minor-modes))))))
 862         ;; remove first space if existed
 863         (if (and (stringp anindicator)
 864                  (> (length anindicator) 0)
 865                  (eq (aref anindicator 0) ?\ ))
 866             (setq anindicator (substring anindicator 1)))
 867         (if (equal indicator anindicator)
 868             (setq result minor-mode
 869                   minor-modes nil)
 870           (setq minor-modes (cdr minor-modes)))))
 871     result))
 872
 873 \f
 874 ;;; Automatic resizing of temporary buffers.
 875
 876 (defcustom temp-buffer-max-height (lambda (buffer) (/ (- (frame-height) 2) 2))
 877   "*Maximum height of a window displaying a temporary buffer.
 878 This is the maximum height (in text lines) which `resize-temp-buffer-window'
 879 will give to a window displaying a temporary buffer.
 880 It can also be a function which will be called with the object corresponding
 881 to the buffer to be displayed as argument and should return an integer
 882 positive number."
 883   :type '(choice integer function)
 884   :group 'help
 885   :version "20.4")
 886
 887 (define-minor-mode temp-buffer-resize-mode
 888   "Toggle the mode which makes windows smaller for temporary buffers.
 889 With prefix argument ARG, turn the resizing of windows displaying temporary
 890 buffers on if ARG is positive or off otherwise.
 891 This makes the window the right height for its contents, but never
 892 more than `temp-buffer-max-height' nor less than `window-min-height'.
 893 This applies to `help', `apropos' and `completion' buffers, and some others."
 894   :global t :group 'help
 895   (if temp-buffer-resize-mode
 896       ;; `help-make-xrefs' may add a `back' button and thus increase the
 897       ;; text size, so `resize-temp-buffer-window' must be run *after* it.
 898       (add-hook 'temp-buffer-show-hook 'resize-temp-buffer-window 'append)
 899     (remove-hook 'temp-buffer-show-hook 'resize-temp-buffer-window)))
 900
 901 (defun resize-temp-buffer-window ()
 902   "Resize the current window to fit its contents.
 903 Will not make it higher than `temp-buffer-max-height' nor smaller than
 904 `window-min-height'.  Do nothing if it is the only window on its frame, if it
 905 is not as wide as the frame or if some of the window's contents are scrolled
 906 out of view."
 907   (unless (or (one-window-p 'nomini)
 908               (not (pos-visible-in-window-p (point-min)))
 909               (/=  (frame-width) (window-width)))
 910     (fit-window-to-buffer
 911      (selected-window)
 912      (if (functionp temp-buffer-max-height)
 913          (funcall temp-buffer-max-height (current-buffer))
 914        temp-buffer-max-height))))
 915
 916 ;; Provide this for the sake of define-minor-mode which generates
 917 ;; defcustoms which require 'help'.
 918 (provide 'help)
 919
 920 ;; arch-tag: cf427352-27e9-49b7-9a6f-741ebab02423
 921 ;;; help.el ends here