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