code.delx.au - gnu-emacs/blob - lisp/help.el

   1 ;;; help.el --- help commands for Emacs
   2
   3 ;; Copyright (C) 1985, 1986, 1993, 1994, 1998, 1999, 2000 Free Software Foundation, Inc.
   4
   5 ;; Maintainer: FSF
   6 ;; Keywords: help, internal
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software; you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation; either version 2, or (at your option)
  13 ;; any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  22 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23 ;; Boston, MA 02111-1307, USA.
  24
  25 ;;; Commentary:
  26
  27 ;; This code implements GNU Emacs' on-line help system, the one invoked by
  28 ;; `M-x help-for-help'.
  29
  30 ;;; Code:
  31
  32 ;; Get the macro make-help-screen when this is compiled,
  33 ;; or run interpreted, but not when the compiled code is loaded.
  34 (eval-when-compile (require 'help-macro))
  35 (eval-when-compile (require 'view))
  36
  37 (defvar help-map (make-sparse-keymap)
  38   "Keymap for characters following the Help key.")
  39
  40 (defvar help-mode-map (make-sparse-keymap)
  41   "Keymap for help mode.")
  42
  43 (define-key global-map (char-to-string help-char) 'help-command)
  44 (define-key global-map [help] 'help-command)
  45 (define-key global-map [f1] 'help-command)
  46 (fset 'help-command help-map)
  47
  48 (define-key help-map (char-to-string help-char) 'help-for-help)
  49 (define-key help-map [help] 'help-for-help)
  50 (define-key help-map [f1] 'help-for-help)
  51 (define-key help-map "?" 'help-for-help)
  52
  53 (define-key help-map "\C-c" 'describe-copying)
  54 (define-key help-map "\C-d" 'describe-distribution)
  55 (define-key help-map "\C-w" 'describe-no-warranty)
  56 (define-key help-map "\C-p" 'describe-project)
  57 (define-key help-map "a" 'apropos-command)
  58
  59 (define-key help-map "b" 'describe-bindings)
  60
  61 (define-key help-map "c" 'describe-key-briefly)
  62 (define-key help-map "k" 'describe-key)
  63
  64 (define-key help-map "d" 'describe-function)
  65 (define-key help-map "f" 'describe-function)
  66
  67 (define-key help-map "F" 'view-emacs-FAQ)
  68
  69 (define-key help-map "i" 'info)
  70 (define-key help-map "4i" 'info-other-window)
  71 (define-key help-map "\C-f" 'Info-goto-emacs-command-node)
  72 (define-key help-map "\C-k" 'Info-goto-emacs-key-command-node)
  73 (define-key help-map "\C-i" 'info-lookup-symbol)
  74
  75 (define-key help-map "l" 'view-lossage)
  76
  77 (define-key help-map "m" 'describe-mode)
  78
  79 (define-key help-map "\C-n" 'view-emacs-news)
  80 (define-key help-map "n" 'view-emacs-news)
  81
  82 (define-key help-map "p" 'finder-by-keyword)
  83 (autoload 'finder-by-keyword "finder"
  84   "Find packages matching a given keyword." t)
  85
  86 (define-key help-map "P" 'view-emacs-problems)
  87
  88 (define-key help-map "s" 'describe-syntax)
  89
  90 (define-key help-map "t" 'help-with-tutorial)
  91
  92 (define-key help-map "w" 'where-is)
  93
  94 (define-key help-map "v" 'describe-variable)
  95
  96 (define-key help-map "q" 'help-quit)
  97
  98 (define-key help-mode-map [mouse-2] 'help-follow-mouse)
  99 (define-key help-mode-map "\C-c\C-b" 'help-go-back)
 100 (define-key help-mode-map "\C-c\C-c" 'help-follow)
 101 (define-key help-mode-map "\t" 'help-next-ref)
 102 (define-key help-mode-map [backtab] 'help-previous-ref)
 103 (define-key help-mode-map [(shift tab)] 'help-previous-ref)
 104 ;; Documentation only, since we use minor-mode-overriding-map-alist.
 105 (define-key help-mode-map "\r" 'help-follow)
 106
 107 (defvar help-xref-stack nil
 108   "A stack of ways by which to return to help buffers after following xrefs.
 109 Used by `help-follow' and `help-xref-go-back'.
 110 An element looks like (POSITION FUNCTION ARGS...), where POSITION is
 111 `(POINT . BUFFER-NAME)'.
 112 To use the element, do (apply FUNCTION ARGS) then goto the point in
 113 the named buffer.")
 114 (put 'help-xref-stack 'permanent-local t)
 115
 116 (defvar help-xref-stack-item nil
 117   "An item for `help-follow' in this buffer to push onto `help-xref-stack'.
 118 The format is (FUNCTION ARGS...).")
 119 (put 'help-xref-stack-item 'permanent-local t)
 120
 121 (setq-default help-xref-stack nil help-xref-stack-item nil)
 122
 123 (defcustom help-mode-hook nil
 124   "Hook run by `help-mode'."
 125   :type 'hook
 126   :group 'help)
 127
 128 (defun help-mode ()
 129   "Major mode for viewing help text and navigating references in it.
 130 Entry to this mode runs the normal hook `help-mode-hook'.
 131 Commands:
 132 \\{help-mode-map}"
 133   (interactive)
 134   (kill-all-local-variables)
 135   (use-local-map help-mode-map)
 136   (setq mode-name "Help")
 137   (setq major-mode 'help-mode)
 138   (make-local-variable 'font-lock-defaults)
 139   (setq font-lock-defaults nil)         ; font-lock would defeat xref
 140   (view-mode)
 141   (make-local-variable 'view-no-disable-on-exit)
 142   (setq view-no-disable-on-exit t)
 143   ;; `help-make-xrefs' would be run here if not invoked from
 144   ;; `help-mode-maybe'.
 145   (run-hooks 'help-mode-hook))
 146
 147 (defun help-mode-setup ()
 148   (help-mode)
 149   (setq buffer-read-only nil))
 150
 151 (add-hook 'temp-buffer-setup-hook 'help-mode-setup)
 152
 153 (defun help-mode-finish ()
 154   (when (eq major-mode 'help-mode)
 155     ;; View mode's read-only status of existing *Help* buffer is lost
 156     ;; by with-output-to-temp-buffer.
 157     (toggle-read-only 1)
 158     (help-make-xrefs (current-buffer)))
 159   (setq view-return-to-alist
 160         (list (cons (selected-window) help-return-method))))
 161
 162 (add-hook 'temp-buffer-show-hook 'help-mode-finish)
 163
 164 (defun help-quit ()
 165   "Just exit from the Help command's command loop."
 166   (interactive)
 167   nil)
 168
 169 (defun help-with-tutorial (&optional arg)
 170   "Select the Emacs learn-by-doing tutorial.
 171 If there is a tutorial version written in the language
 172 of the selected language environment, that version is used.
 173 If there's no tutorial in that language, `TUTORIAL' is selected.
 174 With arg, you are asked to choose which language."
 175   (interactive "P")
 176   (let ((lang (if arg
 177                   (read-language-name 'tutorial "Language: " "English")
 178                 (if (get-language-info current-language-environment 'tutorial)
 179                     current-language-environment
 180                   "English")))
 181         file filename)
 182     (setq filename (get-language-info lang 'tutorial))
 183     (setq file (expand-file-name (concat "~/" filename)))
 184     (delete-other-windows)
 185     (if (get-file-buffer file)
 186         (switch-to-buffer (get-file-buffer file))
 187       (switch-to-buffer (create-file-buffer file))
 188       (setq buffer-file-name file)
 189       (setq default-directory (expand-file-name "~/"))
 190       (setq buffer-auto-save-file-name nil)
 191       (insert-file-contents (expand-file-name filename data-directory))
 192       (goto-char (point-min))
 193       (search-forward "\n<<")
 194       (beginning-of-line)
 195       (delete-region (point) (progn (end-of-line) (point)))
 196       (let ((n (- (window-height (selected-window))
 197                   (count-lines (point-min) (point))
 198                   6)))
 199         (if (< n 12)
 200             (newline n)
 201           ;; Some people get confused by the large gap.
 202           (newline (/ n 2))
 203           (insert "[Middle of page left blank for didactic purposes.  "
 204                   "Text continues below]")
 205           (newline (- n (/ n 2)))))
 206       (goto-char (point-min))
 207       (set-buffer-modified-p nil))))
 208
 209 (defun mode-line-key-binding (key)
 210   "Value is the binding of KEY in the mode line or nil if none."
 211   (let (string-info defn)
 212     (when (and (eq 'mode-line (aref key 0))
 213                (consp (setq string-info (nth 4 (event-start (aref key 1))))))
 214     (let* ((string (car string-info))
 215            (pos (cdr string-info))
 216            (local-map (and (> pos 0)
 217                            (< pos (length string))
 218                            (get-text-property pos 'local-map string))))
 219       (setq defn (and local-map (lookup-key local-map key)))))
 220     defn))
 221
 222 (defun describe-key-briefly (key &optional insert)
 223   "Print the name of the function KEY invokes.  KEY is a string.
 224 If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
 225   (interactive "kDescribe key briefly: \nP")
 226   (save-excursion
 227     (let ((modifiers (event-modifiers (aref key 0)))
 228           (standard-output (if insert (current-buffer) t))
 229           window position)
 230       ;; For a mouse button event, go to the button it applies to
 231       ;; to get the right key bindings.  And go to the right place
 232       ;; in case the keymap depends on where you clicked.
 233       (if (or (memq 'click modifiers) (memq 'down modifiers)
 234               (memq 'drag modifiers))
 235           (setq window (posn-window (event-start (aref key 0)))
 236                 position (posn-point (event-start (aref key 0)))))
 237       (if (windowp window)
 238           (progn
 239             (set-buffer (window-buffer window))
 240             (goto-char position)))
 241       ;; Ok, now look up the key and name the command.
 242       (let ((defn (or (mode-line-key-binding key)
 243                       (key-binding key)))
 244             (key-desc (key-description key)))
 245         (if (or (null defn) (integerp defn))
 246             (princ (format "%s is undefined" key-desc))
 247           (princ (format (if insert
 248                              "`%s' (`%s')"
 249                            (if (windowp window)
 250                                "%s at that spot runs the command %s"
 251                              "%s runs the command %s"))
 252                          key-desc
 253                          (if (symbolp defn) defn (prin1-to-string defn)))))))))
 254
 255 (defvar help-return-method nil
 256   "What to do to \"exit\" the help buffer.
 257 This is a list
 258  (WINDOW . t)              delete the selected window, go to WINDOW.
 259  (WINDOW . quit-window)    do quit-window, then select WINDOW.
 260  (WINDOW BUF START POINT)  display BUF at START, POINT, then select WINDOW.")
 261
 262 (defun print-help-return-message (&optional function)
 263   "Display or return message saying how to restore windows after help command.
 264 Computes a message and applies the optional argument FUNCTION to it.
 265 If FUNCTION is nil, applies `message' to it, thus printing it."
 266   (and (not (get-buffer-window standard-output))
 267        (let ((first-message
 268               (cond ((special-display-p (buffer-name standard-output))
 269                      (setq help-return-method (cons (selected-window) t))
 270                      ;; If the help output buffer is a special display buffer,
 271                      ;; don't say anything about how to get rid of it.
 272                      ;; First of all, the user will do that with the window
 273                      ;; manager, not with Emacs.
 274                      ;; Secondly, the buffer has not been displayed yet,
 275                      ;; so we don't know whether its frame will be selected.
 276                      nil)
 277                     ((not (one-window-p t))
 278                      (setq help-return-method
 279                            (cons (selected-window) 'quit-window))
 280                      "Type \\[switch-to-buffer-other-window] RET to restore the other window.")
 281                     (pop-up-windows
 282                      (setq help-return-method (cons (selected-window) t))
 283                      "Type \\[delete-other-windows] to remove help window.")
 284                     (t
 285                      (setq help-return-method
 286                            (list (selected-window) (window-buffer)
 287                                  (window-start) (window-point)))
 288                      "Type \\[switch-to-buffer] RET to remove help window."))))
 289          (funcall (or function 'message)
 290                   (concat
 291                    (if first-message
 292                        (substitute-command-keys first-message))
 293                    (if first-message "  ")
 294                    ;; If the help buffer will go in a separate frame,
 295                    ;; it's no use mentioning a command to scroll, so don't.
 296                    (if (special-display-p (buffer-name standard-output))
 297                        nil
 298                      (if (same-window-p (buffer-name standard-output))
 299                          ;; Say how to scroll this window.
 300                          (substitute-command-keys
 301                           "\\[scroll-up] to scroll the help.")
 302                        ;; Say how to scroll some other window.
 303                        (substitute-command-keys
 304                         "\\[scroll-other-window] to scroll the help."))))))))
 305
 306 (defun describe-key (key)
 307   "Display documentation of the function invoked by KEY.  KEY is a string."
 308   (interactive "kDescribe key: ")
 309   (save-excursion
 310     (let ((modifiers (event-modifiers (aref key 0)))
 311           window position)
 312       ;; For a mouse button event, go to the button it applies to
 313       ;; to get the right key bindings.  And go to the right place
 314       ;; in case the keymap depends on where you clicked.
 315       (if (or (memq 'click modifiers) (memq 'down modifiers)
 316               (memq 'drag modifiers))
 317           (setq window (posn-window (event-start (aref key 0)))
 318                 position (posn-point (event-start (aref key 0)))))
 319       (if (windowp window)
 320           (progn
 321             (set-buffer (window-buffer window))
 322             (goto-char position)))
 323       (let ((defn (or (mode-line-key-binding key) (key-binding key))))
 324         (if (or (null defn) (integerp defn))
 325             (message "%s is undefined" (key-description key))
 326           (with-output-to-temp-buffer "*Help*"
 327             (princ (key-description key))
 328             (if (windowp window)
 329                 (princ " at that spot"))
 330             (princ " runs the command ")
 331             (prin1 defn)
 332             (princ "\n   which is ")
 333             (describe-function-1 defn nil (interactive-p))
 334             (print-help-return-message)))))))
 335
 336 (defun describe-mode ()
 337   "Display documentation of current major mode and minor modes.
 338 The major mode description comes first, followed by the minor modes,
 339 each on a separate page.
 340
 341 For this to work correctly for a minor mode, the mode's indicator variable
 342 \(listed in `minor-mode-alist') must also be a function whose documentation
 343 describes the minor mode."
 344   (interactive)
 345   (with-output-to-temp-buffer "*Help*"
 346     (when minor-mode-alist
 347       (princ "The major mode is described first.
 348 For minor modes, see following pages.\n\n"))
 349     (princ mode-name)
 350     (princ " mode:\n")
 351     (princ (documentation major-mode))
 352     (help-setup-xref (list #'help-xref-mode (current-buffer)) (interactive-p))
 353     (let ((minor-modes minor-mode-alist))
 354       (while minor-modes
 355         (let* ((minor-mode (car (car minor-modes)))
 356                (indicator (car (cdr (car minor-modes)))))
 357           ;; Document a minor mode if it is listed in minor-mode-alist,
 358           ;; bound locally in this buffer, non-nil, and has a function
 359           ;; definition.
 360           (if (and (symbol-value minor-mode)
 361                    (fboundp minor-mode))
 362               (let ((pretty-minor-mode minor-mode))
 363                 (if (string-match "-mode$" (symbol-name minor-mode))
 364                     (setq pretty-minor-mode
 365                           (capitalize
 366                            (substring (symbol-name minor-mode)
 367                                       0 (match-beginning 0)))))
 368                 (while (and indicator (symbolp indicator)
 369                             (boundp indicator)
 370                             (not (eq indicator (symbol-value indicator))))
 371                   (setq indicator (symbol-value indicator)))
 372                 (princ "\n\f\n")
 373                 (princ (format "%s minor mode (%s):\n"
 374                                pretty-minor-mode
 375                                (if indicator
 376                                    (format "indicator%s" indicator)
 377                                  "no indicator")))
 378                 (princ (documentation minor-mode)))))
 379         (setq minor-modes (cdr minor-modes))))
 380     (print-help-return-message)))
 381
 382 ;; So keyboard macro definitions are documented correctly
 383 (fset 'defining-kbd-macro (symbol-function 'start-kbd-macro))
 384
 385 (defun describe-distribution ()
 386   "Display info on how to obtain the latest version of GNU Emacs."
 387   (interactive)
 388   (find-file-read-only
 389    (expand-file-name "DISTRIB" data-directory)))
 390
 391 (defun describe-copying ()
 392   "Display info on how you may redistribute copies of GNU Emacs."
 393   (interactive)
 394   (find-file-read-only
 395    (expand-file-name "COPYING" data-directory))
 396   (goto-char (point-min)))
 397
 398 (defun describe-project ()
 399   "Display info on the GNU project."
 400   (interactive)
 401   (find-file-read-only
 402    (expand-file-name "GNU" data-directory))
 403   (goto-char (point-min)))
 404
 405 (defun describe-no-warranty ()
 406   "Display info on all the kinds of warranty Emacs does NOT have."
 407   (interactive)
 408   (describe-copying)
 409   (let (case-fold-search)
 410     (search-forward "NO WARRANTY")
 411     (recenter 0)))
 412
 413 (defun describe-prefix-bindings ()
 414   "Describe the bindings of the prefix used to reach this command.
 415 The prefix described consists of all but the last event
 416 of the key sequence that ran this command."
 417   (interactive)
 418   (let* ((key (this-command-keys)))
 419     (describe-bindings
 420      (if (stringp key)
 421          (substring key 0 (1- (length key)))
 422        (let ((prefix (make-vector (1- (length key)) nil))
 423              (i 0))
 424          (while (< i (length prefix))
 425            (aset prefix i (aref key i))
 426            (setq i (1+ i)))
 427          prefix)))))
 428 ;; Make C-h after a prefix, when not specifically bound,
 429 ;; run describe-prefix-bindings.
 430 (setq prefix-help-command 'describe-prefix-bindings)
 431
 432 (defun view-emacs-news (&optional arg)
 433   "Display info on recent changes to Emacs.
 434 With numeric argument display information on correspondingly older changes."
 435   (interactive "P")
 436   (let* ((arg (if arg (prefix-numeric-value arg) 0)))
 437     (find-file-read-only
 438      (expand-file-name (concat (make-string arg ?O) "NEWS")
 439                        data-directory))))
 440
 441 (defun view-emacs-FAQ ()
 442   "Display the Emacs Frequently Asked Questions (FAQ) file."
 443   (interactive)
 444 ;;;  (find-file-read-only (expand-file-name "FAQ" data-directory))
 445   (info "(efaq)"))
 446
 447 (defun view-emacs-problems ()
 448   "Display info on known problems with Emacs and possible workarounds."
 449   (interactive)
 450   (view-file (expand-file-name "PROBLEMS" data-directory)))
 451
 452 (defun view-lossage ()
 453   "Display last 100 input keystrokes."
 454   (interactive)
 455   (with-output-to-temp-buffer "*Help*"
 456     (princ (mapconcat (function (lambda (key)
 457                                   (if (or (integerp key)
 458                                           (symbolp key)
 459                                           (listp key))
 460                                       (single-key-description key)
 461                                     (prin1-to-string key nil))))
 462                       (recent-keys)
 463                       " "))
 464     (save-excursion
 465       (set-buffer standard-output)
 466       (goto-char (point-min))
 467       (while (progn (move-to-column 50) (not (eobp)))
 468         (search-forward " " nil t)
 469         (insert "\n"))
 470       (setq help-xref-stack nil
 471             help-xref-stack-item nil))
 472     (print-help-return-message)))
 473
 474 (defalias 'help 'help-for-help)
 475 (make-help-screen help-for-help
 476   "a b c C f F C-f i I k C-k l L m n p s t v w C-c C-d C-n C-p C-w; ? for help:"
 477   "You have typed %THIS-KEY%, the help character.  Type a Help option:
 478 \(Use SPC or DEL to scroll through this text.  Type \\<help-map>\\[help-quit] to exit the Help command.)
 479
 480 a  command-apropos.  Give a substring, and see a list of commands
 481         (functions interactively callable) that contain
 482         that substring.  See also the  apropos  command.
 483 b  describe-bindings.  Display table of all key bindings.
 484 c  describe-key-briefly.  Type a command key sequence;
 485         it prints the function name that sequence runs.
 486 C  describe-coding-system.  This describes either a specific coding system
 487         (if you type its name) or the coding systems currently in use
 488         (if you type just RET).
 489 f  describe-function.  Type a function name and get documentation of it.
 490 C-f Info-goto-emacs-command-node.  Type a function name;
 491         it takes you to the Info node for that command.
 492 i  info. The  info  documentation reader.
 493 I  describe-input-method.  Describe a specific input method (if you type
 494         its name) or the current input method (if you type just RET).
 495 C-i  info-lookup-symbol.  Display the definition of a specific symbol
 496         as found in the manual for the language this buffer is written in.
 497 k  describe-key.  Type a command key sequence;
 498         it displays the full documentation.
 499 C-k Info-goto-emacs-key-command-node.  Type a command key sequence;
 500         it takes you to the Info node for the command bound to that key.
 501 l  view-lossage.  Show last 100 characters you typed.
 502 L  describe-language-environment.  This describes either the a
 503         specific language environment (if you type its name)
 504         or the current language environment (if you type just RET).
 505 m  describe-mode.  Print documentation of current minor modes,
 506         and the current major mode, including their special commands.
 507 n  view-emacs-news.  Display news of recent Emacs changes.
 508 p  finder-by-keyword. Find packages matching a given topic keyword.
 509 s  describe-syntax.  Display contents of syntax table, plus explanations
 510 t  help-with-tutorial.  Select the Emacs learn-by-doing tutorial.
 511 v  describe-variable.  Type name of a variable;
 512         it displays the variable's documentation and value.
 513 w  where-is.  Type command name; it prints which keystrokes
 514         invoke that command.
 515
 516 F  Display the frequently asked questions file.
 517 h  Display the HELLO file which illustrates various scripts.
 518 C-c Display Emacs copying permission (General Public License).
 519 C-d Display Emacs ordering information.
 520 C-n Display news of recent Emacs changes.
 521 C-p Display information about the GNU project.
 522 C-w Display information on absence of warranty for GNU Emacs."
 523   help-map)
 524
 525 (defun function-called-at-point ()
 526   "Return a function around point or else called by the list containing point.
 527 If that doesn't give a function, return nil."
 528   (let ((stab (syntax-table)))
 529     (set-syntax-table emacs-lisp-mode-syntax-table)
 530     (unwind-protect
 531         (or (condition-case ()
 532                 (save-excursion
 533                   (or (not (zerop (skip-syntax-backward "_w")))
 534                       (eq (char-syntax (following-char)) ?w)
 535                       (eq (char-syntax (following-char)) ?_)
 536                       (forward-sexp -1))
 537                   (skip-chars-forward "'")
 538                   (let ((obj (read (current-buffer))))
 539                     (and (symbolp obj) (fboundp obj) obj)))
 540               (error nil))
 541             (condition-case ()
 542                 (save-excursion
 543                   (save-restriction
 544                     (narrow-to-region (max (point-min) (- (point) 1000)) (point-max))
 545                     ;; Move up to surrounding paren, then after the open.
 546                     (backward-up-list 1)
 547                     (forward-char 1)
 548                     ;; If there is space here, this is probably something
 549                     ;; other than a real Lisp function call, so ignore it.
 550                     (if (looking-at "[ \t]")
 551                         (error "Probably not a Lisp function call"))
 552                     (let (obj)
 553                       (setq obj (read (current-buffer)))
 554                       (and (symbolp obj) (fboundp obj) obj))))
 555               (error nil)))
 556       (set-syntax-table stab))))
 557
 558 (defvar symbol-file-load-history-loaded nil
 559   "Non-nil means we have loaded the file `fns-VERSION.el' in `exec-directory'.
 560 That file records the part of `load-history' for preloaded files,
 561 which is cleared out before dumping to make Emacs smaller.")
 562
 563 (defun symbol-file (function)
 564   "Return the input source from which FUNCTION was loaded.
 565 The value is normally a string that was passed to `load':
 566 either an absolute file name, or a library name
 567 \(with no directory name and no `.el' or `.elc' at the end).
 568 It can also be nil, if the definition is not associated with any file."
 569   (unless symbol-file-load-history-loaded
 570     (load (expand-file-name
 571            ;; fns-XX.YY.ZZ.el does not work on DOS filesystem.
 572            (if (eq system-type 'ms-dos)
 573                "fns.el"
 574              (format "fns-%s.el" emacs-version))
 575            exec-directory)
 576           ;; The file name fns-%s.el already has a .el extension.
 577           nil nil t)
 578     (setq symbol-file-load-history-loaded t))
 579   (let ((files load-history)
 580         file functions)
 581     (while files
 582       (if (memq function (cdr (car files)))
 583           (setq file (car (car files)) files nil))
 584       (setq files (cdr files)))
 585     file))
 586
 587 (defun describe-function (function)
 588   "Display the full documentation of FUNCTION (a symbol)."
 589   (interactive
 590    (let ((fn (function-called-at-point))
 591          (enable-recursive-minibuffers t)
 592          val)
 593      (setq val (completing-read (if fn
 594                                     (format "Describe function (default %s): " fn)
 595                                   "Describe function: ")
 596                                 obarray 'fboundp t nil nil (symbol-name fn)))
 597      (list (if (equal val "")
 598                fn (intern val)))))
 599   (if function
 600       (with-output-to-temp-buffer "*Help*"
 601         (prin1 function)
 602         ;; Use " is " instead of a colon so that
 603         ;; it is easier to get out the function name using forward-sexp.
 604         (princ " is ")
 605         (describe-function-1 function nil (interactive-p))
 606         (print-help-return-message)
 607         (save-excursion
 608           (set-buffer standard-output)
 609           ;; Return the text we displayed.
 610           (buffer-string)))
 611     (message "You didn't specify a function")))
 612
 613 (defun describe-function-1 (function parens interactive-p)
 614   (let* ((def (if (symbolp function)
 615                   (symbol-function function)
 616                 function))
 617          file-name string need-close
 618          (beg (if (commandp def) "an interactive " "a ")))
 619     (setq string
 620           (cond ((or (stringp def)
 621                      (vectorp def))
 622                  "a keyboard macro")
 623                 ((subrp def)
 624                  (concat beg "built-in function"))
 625                 ((byte-code-function-p def)
 626                  (concat beg "compiled Lisp function"))
 627                 ((symbolp def)
 628                  (while (symbolp (symbol-function def))
 629                    (setq def (symbol-function def)))
 630                  (format "an alias for `%s'" def))
 631                 ((eq (car-safe def) 'lambda)
 632                  (concat beg "Lisp function"))
 633                 ((eq (car-safe def) 'macro)
 634                  "a Lisp macro")
 635                 ((eq (car-safe def) 'mocklisp)
 636                  "a mocklisp function")
 637                 ((eq (car-safe def) 'autoload)
 638                  (setq file-name (nth 1 def))
 639                  (format "%s autoloaded %s"
 640                          (if (commandp def) "an interactive" "an")
 641                          (if (eq (nth 4 def) 'keymap) "keymap"
 642                            (if (nth 4 def) "Lisp macro" "Lisp function"))
 643                          ))
 644                 ;; perhaps use keymapp here instead
 645                 ((eq (car-safe def) 'keymap)
 646                  (let ((is-full nil)
 647                        (elts (cdr-safe def)))
 648                    (while elts
 649                      (if (char-table-p (car-safe elts))
 650                          (setq is-full t
 651                                elts nil))
 652                      (setq elts (cdr-safe elts)))
 653                    (if is-full
 654                        "a full keymap"
 655                      "a sparse keymap")))
 656                 (t "")))
 657     (when (and parens (not (equal string "")))
 658       (setq need-close t)
 659       (princ "("))
 660     (princ string)
 661     (with-current-buffer "*Help*"
 662       (save-excursion
 663         (save-match-data
 664           (if (re-search-backward "alias for `\\([^`']+\\)'" nil t)
 665               (help-xref-button 1 #'describe-function def
 666                                 "mouse-2, RET: describe this function")))))
 667     (or file-name
 668         (setq file-name (symbol-file function)))
 669     (if file-name
 670         (progn
 671           (princ " in `")
 672           ;; We used to add .el to the file name,
 673           ;; but that's completely wrong when the user used load-file.
 674           (princ file-name)
 675           (princ "'")
 676           ;; Make a hyperlink to the library.
 677           (with-current-buffer "*Help*"
 678             (save-excursion
 679               (re-search-backward "`\\([^`']+\\)'" nil t)
 680               (help-xref-button 1 #'(lambda (arg)
 681                                       (let ((location
 682                                              (find-function-noselect arg)))
 683                                         (pop-to-buffer (car location))
 684                                         (goto-char (cdr location))))
 685                                 function
 686                                 "mouse-2, RET: find function's definition")))))
 687     (if need-close (princ ")"))
 688     (princ ".")
 689     (terpri)
 690     ;; Handle symbols aliased to other symbols.
 691     (setq def (indirect-function def))
 692     ;; If definition is a macro, find the function inside it.
 693     (if (eq (car-safe def) 'macro)
 694         (setq def (cdr def)))
 695     (let ((arglist (cond ((byte-code-function-p def)
 696                           (car (append def nil)))
 697                          ((eq (car-safe def) 'lambda)
 698                           (nth 1 def))
 699                          ((and (eq (car-safe def) 'autoload)
 700                                (not (eq (nth 4 def) 'keymap)))
 701                           (concat "[Arg list not available until "
 702                                   "function definition is loaded.]"))
 703                          (t t))))
 704       (cond ((listp arglist)
 705              (princ (cons (if (symbolp function) function "anonymous")
 706                           (mapcar (lambda (arg)
 707                                     (if (memq arg '(&optional &rest))
 708                                         arg
 709                                       (intern (upcase (symbol-name arg)))))
 710                                   arglist)))
 711              (terpri))
 712             ((stringp arglist)
 713              (princ arglist)
 714              (terpri))))
 715     (let ((doc (documentation function)))
 716       (if doc
 717           (progn (terpri)
 718                  (princ doc)
 719                  (with-current-buffer standard-output
 720                    (beginning-of-line)
 721                    ;; Builtins get the calling sequence at the end of
 722                    ;; the doc string.  Move it to the same place as
 723                    ;; for other functions.
 724                    (when (looking-at (format "(%S[ )]" function))
 725                      (let ((start (point-marker)))
 726                        (goto-char (point-min))
 727                        (forward-paragraph)
 728                        (insert-buffer-substring (current-buffer) start)
 729                        (insert ?\n)
 730                        (delete-region (1- start) (point-max))
 731                        (goto-char (point-max)))))
 732                  (help-setup-xref (list #'describe-function function)
 733                                   interactive-p))
 734         (princ "not documented")))))
 735
 736 (defun variable-at-point ()
 737   "Return the bound variable symbol found around point.
 738 Return 0 if there is no such symbol."
 739   (condition-case ()
 740       (let ((stab (syntax-table)))
 741         (unwind-protect
 742             (save-excursion
 743               (set-syntax-table emacs-lisp-mode-syntax-table)
 744               (or (not (zerop (skip-syntax-backward "_w")))
 745                   (eq (char-syntax (following-char)) ?w)
 746                   (eq (char-syntax (following-char)) ?_)
 747                   (forward-sexp -1))
 748               (skip-chars-forward "'")
 749               (let ((obj (read (current-buffer))))
 750                 (or (and (symbolp obj) (boundp obj) obj)
 751                     0)))
 752           (set-syntax-table stab)))
 753     (error 0)))
 754
 755 (defun help-xref-on-pp (from to)
 756   "Add xrefs for symbols in `pp's output between FROM and TO."
 757   (let ((ost (syntax-table)))
 758     (unwind-protect
 759         (save-excursion
 760           (save-restriction
 761             (set-syntax-table emacs-lisp-mode-syntax-table)
 762             (narrow-to-region from to)
 763             (goto-char (point-min))
 764             (while (not (eobp))
 765               (cond
 766                ((looking-at "\"") (forward-sexp 1))
 767                ((looking-at "#<") (search-forward ">" nil 'move))
 768                ((looking-at "\\(\\(\\sw\\|\\s_\\)+\\)")
 769                 (let* ((sym (intern-soft
 770                              (buffer-substring (match-beginning 1)
 771                                                (match-end 1))))
 772                        (fn (cond ((fboundp sym) #'describe-function)
 773                                  ((or (memq sym '(t nil))
 774                                       (keywordp sym))
 775                                   nil)
 776                                  ((and sym (boundp sym))
 777                                   #'describe-variable))))
 778                   (when fn (help-xref-button 1 fn sym)))
 779                 (goto-char (match-end 1)))
 780                (t (forward-char 1))))))
 781       (set-syntax-table ost))))
 782
 783 (defun describe-variable (variable)
 784   "Display the full documentation of VARIABLE (a symbol).
 785 Returns the documentation as a string, also."
 786   (interactive
 787    (let ((v (variable-at-point))
 788          (enable-recursive-minibuffers t)
 789          val)
 790      (setq val (completing-read (if (symbolp v)
 791                                     (format
 792                                      "Describe variable (default %s): " v)
 793                                   "Describe variable: ")
 794                                 obarray 'boundp t nil nil
 795                                 (if (symbolp v) (symbol-name v))))
 796      (list (if (equal val "")
 797                v (intern val)))))
 798   (if (symbolp variable)
 799       (let (valvoid)
 800         (with-output-to-temp-buffer "*Help*"
 801           (prin1 variable)
 802           (if (not (boundp variable))
 803               (progn
 804                 (princ " is void")
 805                 (setq valvoid t))
 806             (let ((val (symbol-value variable)))
 807               (with-current-buffer standard-output
 808                 (princ "'s value is ")
 809                 (terpri)
 810                 (let ((from (point)))
 811                   (pp val)
 812                   (help-xref-on-pp from (point))))))
 813           (terpri)
 814           (if (local-variable-p variable)
 815               (progn
 816                 (princ (format "Local in buffer %s; " (buffer-name)))
 817                 (if (not (default-boundp variable))
 818                     (princ "globally void")
 819                   (let ((val (default-value variable)))
 820                     (with-current-buffer standard-output
 821                       (princ "global value is ")
 822                       (terpri)
 823                       (let ((from (point)))
 824                         (pp val)
 825                         (help-xref-on-pp from (point))))))
 826                 (terpri)))
 827           (terpri)
 828           (save-current-buffer
 829             (set-buffer standard-output)
 830             (if (> (count-lines (point-min) (point-max)) 10)
 831                 (progn
 832                   (set-syntax-table emacs-lisp-mode-syntax-table)
 833                   (goto-char (point-min))
 834                   (if valvoid
 835                       (forward-line 1)
 836                     (forward-sexp 1)
 837                     (delete-region (point) (progn (end-of-line) (point)))
 838                     (insert "'s value is shown below.\n\n")
 839                     (save-excursion
 840                       (insert "\n\nValue:"))))))
 841           (princ "Documentation:")
 842           (terpri)
 843           (let ((doc (documentation-property variable 'variable-documentation)))
 844             (princ (or doc "not documented as a variable.")))
 845           (help-setup-xref (list #'describe-variable variable) (interactive-p))
 846
 847           ;; Make a link to customize if this variable can be customized.
 848           ;; Note, it is not reliable to test only for a custom-type property
 849           ;; because those are only present after the var's definition
 850           ;; has been loaded.
 851           (if (or (get variable 'custom-type) ; after defcustom
 852                   (get variable 'custom-loads) ; from loaddefs.el
 853                   (get variable 'standard-value)) ; from cus-start.el
 854               (let ((customize-label "customize"))
 855                 (terpri)
 856                 (terpri)
 857                 (princ (concat "You can " customize-label " this variable."))
 858                 (with-current-buffer "*Help*"
 859                   (save-excursion
 860                     (re-search-backward
 861                      (concat "\\(" customize-label "\\)") nil t)
 862                     (help-xref-button 1 (lambda (v)
 863                                           (if help-xref-stack
 864                                               (pop help-xref-stack))
 865                                           (customize-variable v))
 866                                       variable
 867                                       "mouse-2, RET: customize variable")))))
 868           ;; Make a hyperlink to the library if appropriate.  (Don't
 869           ;; change the format of the buffer's initial line in case
 870           ;; anything expects the current format.)
 871           (let ((file-name (symbol-file variable)))
 872             (when file-name
 873               (princ "\n\nDefined in `")
 874               (princ file-name)
 875               (princ "'.")
 876               (with-current-buffer "*Help*"
 877                 (save-excursion
 878                   (re-search-backward "`\\([^`']+\\)'" nil t)
 879                   (help-xref-button
 880                    1 (lambda (arg)
 881                        (let ((location
 882                               (find-variable-noselect arg)))
 883                          (pop-to-buffer (car location))
 884                          (goto-char (cdr location))))
 885                    variable "mouse-2, RET: find variable's definition")))))
 886
 887           (print-help-return-message)
 888           (save-excursion
 889             (set-buffer standard-output)
 890             ;; Return the text we displayed.
 891             (buffer-string))))
 892     (message "You did not specify a variable")))
 893
 894 (defun describe-bindings (&optional prefix buffer)
 895   "Show a list of all defined keys, and their definitions.
 896 We put that list in a buffer, and display the buffer.
 897
 898 The optional argument PREFIX, if non-nil, should be a key sequence;
 899 then we display only bindings that start with that prefix.
 900 The optional argument BUFFER specifies which buffer's bindings
 901 to display (default, the current buffer)."
 902   (interactive "P")
 903   (or buffer (setq buffer (current-buffer)))
 904   (with-current-buffer buffer
 905     (describe-bindings-internal nil prefix))
 906   (with-current-buffer "*Help*"
 907     (help-setup-xref (list #'describe-bindings prefix buffer)
 908                      (interactive-p))))
 909
 910 (defun where-is (definition &optional insert)
 911   "Print message listing key sequences that invoke the command DEFINITION.
 912 Argument is a command definition, usually a symbol with a function definition.
 913 If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
 914   (interactive
 915    (let ((fn (function-called-at-point))
 916          (enable-recursive-minibuffers t)
 917          val)
 918      (setq val (completing-read (if fn
 919                                     (format "Where is command (default %s): " fn)
 920                                   "Where is command: ")
 921                                 obarray 'commandp t))
 922      (list (if (equal val "")
 923                fn (intern val))
 924            current-prefix-arg)))
 925   (let* ((keys (where-is-internal definition overriding-local-map nil nil))
 926          (keys1 (mapconcat 'key-description keys ", "))
 927          (standard-output (if insert (current-buffer) t)))
 928     (if insert
 929         (if (> (length keys1) 0)
 930             (princ (format "%s (%s)" keys1 definition))
 931           (princ (format "M-x %s RET" definition)))
 932       (if (> (length keys1) 0)
 933           (princ (format "%s is on %s" definition keys1))
 934         (princ (format "%s is not on any key" definition)))))
 935   nil)
 936
 937 (defun locate-library (library &optional nosuffix path interactive-call)
 938   "Show the precise file name of Emacs library LIBRARY.
 939 This command searches the directories in `load-path' like `M-x load-library'
 940 to find the file that `M-x load-library RET LIBRARY RET' would load.
 941 Optional second arg NOSUFFIX non-nil means don't add suffixes `.elc' or `.el'
 942 to the specified name LIBRARY.
 943
 944 If the optional third arg PATH is specified, that list of directories
 945 is used instead of `load-path'.
 946
 947 When called from a program, the file name is normaly returned as a
 948 string.  When run interactively, the argument INTERACTIVE-CALL is t,
 949 and the file name is displayed in the echo area."
 950   (interactive (list (read-string "Locate library: ")
 951                      nil nil
 952                      t))
 953   (let (result)
 954     (catch 'answer
 955       (mapc
 956        (lambda (dir)
 957          (mapc
 958           (lambda (suf)
 959             (let ((try (expand-file-name (concat library suf) dir)))
 960               (and (file-readable-p try)
 961                    (null (file-directory-p try))
 962                    (progn
 963                      (setq result try)
 964                      (throw 'answer try)))))
 965           (if nosuffix
 966               '("")
 967             '(".elc" ".el" "")
 968 ;;; load doesn't handle this yet.
 969 ;;;         (let ((basic '(".elc" ".el" ""))
 970 ;;;               (compressed '(".Z" ".gz" "")))
 971 ;;;           ;; If autocompression mode is on,
 972 ;;;           ;; consider all combinations of library suffixes
 973 ;;;           ;; and compression suffixes.
 974 ;;;           (if (rassq 'jka-compr-handler file-name-handler-alist)
 975 ;;;               (apply 'nconc
 976 ;;;                      (mapcar (lambda (compelt)
 977 ;;;                                (mapcar (lambda (baselt)
 978 ;;;                                          (concat baselt compelt))
 979 ;;;                                        basic))
 980 ;;;                              compressed))
 981 ;;;             basic))
 982             )))
 983        (or path load-path)))
 984     (and interactive-call
 985          (if result
 986              (message "Library is file %s" result)
 987            (message "No library %s in search path" library)))
 988     result))
 989
 990 \f
 991 ;;; Grokking cross-reference information in doc strings and
 992 ;;; hyperlinking it.
 993
 994 ;; This may have some scope for extension and the same or something
 995 ;; similar should be done for widget doc strings, which currently use
 996 ;; another mechanism.
 997
 998 (defcustom help-highlight-p t
 999   "*If non-nil, `help-make-xrefs' highlight cross-references.
1000 Under a window system it highlights them with face defined by
1001 `help-highlight-face'."
1002  :group 'help
1003  :version "20.3"
1004  :type 'boolean)
1005
1006 (defcustom help-highlight-face 'underline
1007   "Face used by `help-make-xrefs' to highlight cross-references.
1008 Must be previously-defined."
1009   :group 'help
1010   :version "20.3"
1011   :type 'face)
1012
1013 (defvar help-back-label (purecopy "[back]")
1014   "Label to use by `help-make-xrefs' for the go-back reference.")
1015
1016 (defconst help-xref-symbol-regexp
1017   (purecopy (concat "\\(\\<\\(\\(variable\\|option\\)\\|"
1018                     "\\(function\\|command\\)\\|"
1019                     "\\(face\\)\\|"
1020                     "\\(symbol\\)\\)\\s-+\\)?"
1021                     ;; Note starting with word-syntax character:
1022                     "`\\(\\sw\\(\\sw\\|\\s_\\)+\\)'"))
1023   "Regexp matching doc string references to symbols.
1024
1025 The words preceding the quoted symbol can be used in doc strings to
1026 distinguish references to variables, functions and symbols.")
1027
1028 (defconst help-xref-info-regexp
1029   (purecopy "\\<[Ii]nfo[ \t\n]+node[ \t\n]+`\\([^']+\\)'")
1030   "Regexp matching doc string references to an Info node.")
1031
1032 (defun help-setup-xref (item interactive-p)
1033   "Invoked from commands using the \"*Help*\" buffer to install some xref info.
1034
1035 ITEM is a (FUNCTION . ARGS) pair appropriate for recreating the help
1036 buffer after following a reference.  INTERACTIVE-P is non-nil if the
1037 calling command was invoked interactively.  In this case the stack of
1038 items for help buffer \"back\" buttons is cleared."
1039   (if interactive-p
1040       (setq help-xref-stack nil))
1041   (setq help-xref-stack-item item))
1042
1043 (defvar help-xref-following nil
1044   "Non-nil when following a help cross-reference.")
1045
1046 (defun help-make-xrefs (&optional buffer)
1047   "Parse and hyperlink documentation cross-references in the given BUFFER.
1048
1049 Find cross-reference information in a buffer and, if
1050 `help-highlight-p' is non-nil, highlight it with face defined by
1051 `help-highlight-face'; activate such cross references for selection
1052 with `help-follow'.  Cross-references have the canonical form `...'
1053 and the type of reference may be disambiguated by the preceding
1054 word(s) used in `help-xref-symbol-regexp'.
1055
1056 A special reference `back' is made to return back through a stack of
1057 help buffers.  Variable `help-back-label' specifies the text for
1058 that."
1059   (interactive "b")
1060   (save-excursion
1061     (set-buffer (or buffer (current-buffer)))
1062     (goto-char (point-min))
1063     ;; Skip the header-type info, though it might be useful to parse
1064     ;; it at some stage (e.g. "function in `library'").
1065     (forward-paragraph)
1066     (let ((old-modified (buffer-modified-p)))
1067       (let ((stab (syntax-table))
1068             (case-fold-search t)
1069             (inhibit-read-only t))
1070         (set-syntax-table emacs-lisp-mode-syntax-table)
1071         ;; The following should probably be abstracted out.
1072         (unwind-protect
1073             (progn
1074               ;; Info references
1075               (save-excursion
1076                 (while (re-search-forward help-xref-info-regexp nil t)
1077                   (let ((data (match-string 1)))
1078                     (save-match-data
1079                       (unless (string-match "^([^)]+)" data)
1080                         (setq data (concat "(emacs)" data))))
1081                     (help-xref-button 1 #'info data
1082                                       "mouse-2, RET: read this Info node"))))
1083               ;; Quoted symbols
1084               (save-excursion
1085                 (while (re-search-forward help-xref-symbol-regexp nil t)
1086                   (let* ((data (match-string 7))
1087                          (sym (intern-soft data)))
1088                     (if sym
1089                         (cond
1090                          ((match-string 3) ; `variable' &c
1091                           (and (boundp sym) ; `variable' doesn't ensure
1092                                         ; it's actually bound
1093                                (help-xref-button
1094                                 7 #'describe-variable sym
1095                                 "mouse-2, RET: describe this variable")))
1096                          ((match-string 4) ; `function' &c
1097                           (and (fboundp sym) ; similarly
1098                                (help-xref-button
1099                                 7 #'describe-function sym
1100                                 "mouse-2, RET: describe this function")))
1101                          ((match-string 5) ; `face'
1102                           (and (facep sym)
1103                                (help-xref-button 7 #'describe-face sym
1104                                 "mouse-2, RET: describe this face")))
1105                          ((match-string 6)) ; nothing for symbol
1106                          ((and (boundp sym) (fboundp sym))
1107                           ;; We can't intuit whether to use the
1108                           ;; variable or function doc -- supply both.
1109                           (help-xref-button
1110                            7 #'help-xref-interned sym
1111                            "mouse-2, RET: describe this symbol"))
1112                          ((boundp sym)
1113                           (help-xref-button
1114                            7 #'describe-variable sym
1115                            "mouse-2, RET: describe this variable"))
1116                          ((fboundp sym)
1117                           (help-xref-button
1118                            7 #'describe-function sym
1119                            "mouse-2, RET: describe this function"))
1120                          ((facep sym)
1121                           (help-xref-button
1122                            7 #'describe-face sym)))))))
1123               ;; An obvious case of a key substitution:
1124               (save-excursion
1125                 (while (re-search-forward
1126                         ;; Assume command name is only word characters
1127                         ;; and dashes to get things like `use M-x foo.'.
1128                         "\\<M-x\\s-+\\(\\sw\\(\\sw\\|-\\)+\\)" nil t)
1129                   (let ((sym (intern-soft (match-string 1))))
1130                     (if (fboundp sym)
1131                         (help-xref-button
1132                          1 #'describe-function sym
1133                          "mouse-2, RET: describe this command")))))
1134               ;; Look for commands in whole keymap substitutions:
1135               (save-excursion
1136                 ;; Make sure to find the first keymap.
1137                 (goto-char (point-min))
1138                 ;; Find a header and the column at which the command
1139                 ;; name will be found.
1140                 (while (re-search-forward "^key +binding\n\\(-+ +\\)-+\n\n"
1141                                           nil t)
1142                   (let ((col (- (match-end 1) (match-beginning 1))))
1143                     (while
1144                         ;; Ignore single blank lines in table, but not
1145                         ;; double ones, which should terminate it.
1146                         (and (not (looking-at "\n\\s-*\n"))
1147                              (progn
1148                                (and (eolp) (forward-line))
1149                                (end-of-line)
1150                                (skip-chars-backward "^\t\n")
1151                                (if (and (>= (current-column) col)
1152                                         (looking-at "\\(\\sw\\|-\\)+$"))
1153                                    (let ((sym (intern-soft (match-string 0))))
1154                                      (if (fboundp sym)
1155                                          (help-xref-button
1156                                           0 #'describe-function sym
1157                                           "mouse-2, RET: describe this function"))))
1158                                (zerop (forward-line)))))))))
1159           (set-syntax-table stab))
1160         ;; Make a back-reference in this buffer if appropriate.
1161         (when (and help-xref-following help-xref-stack)
1162           (goto-char (point-max))
1163           (save-excursion
1164             (insert "\n\n" help-back-label))
1165           ;; Just to provide the match data:
1166           (looking-at (concat "\n\n\\(" (regexp-quote help-back-label) "\\)"))
1167           (help-xref-button 1 #'help-xref-go-back (current-buffer))))
1168       ;; View mode steals RET from us.
1169       (set (make-local-variable 'minor-mode-overriding-map-alist)
1170            (list (cons 'view-mode
1171                        (let ((map (make-sparse-keymap)))
1172                          (set-keymap-parent map view-mode-map)
1173                          (define-key map "\r" 'help-follow)
1174                          map))))
1175       (set-buffer-modified-p old-modified))))
1176
1177 (defun help-xref-button (match-number function data &optional help-echo)
1178   "Make a hyperlink for cross-reference text previously matched.
1179
1180 MATCH-NUMBER is the subexpression of interest in the last matched
1181 regexp.  FUNCTION is a function to invoke when the button is
1182 activated, applied to DATA.  DATA may be a single value or a list.
1183 See `help-make-xrefs'.
1184 If optional arg HELP-ECHO is supplied, it is used as a help string."
1185   ;; Don't mung properties we've added specially in some instances.
1186   (unless (get-text-property (match-beginning match-number) 'help-xref)
1187     (add-text-properties (match-beginning match-number)
1188                          (match-end match-number)
1189                          (list 'mouse-face 'highlight
1190                                'help-xref (cons function
1191                                                 (if (listp data)
1192                                                     data
1193                                                   (list data)))))
1194     (if help-echo
1195         (put-text-property (match-beginning match-number)
1196                            (match-end match-number)
1197                            'help-echo help-echo))
1198     (if help-highlight-p
1199         (put-text-property (match-beginning match-number)
1200                            (match-end match-number)
1201                            'face help-highlight-face))))
1202
1203 \f
1204 ;; Additional functions for (re-)creating types of help buffers.
1205 (defun help-xref-interned (symbol)
1206   "Follow a hyperlink which appeared to be an arbitrary interned SYMBOL.
1207
1208 Both variable and function documentation are extracted into a single
1209 help buffer."
1210   (let ((fdoc (when (fboundp symbol) (describe-function symbol)))
1211         (facedoc (when (facep symbol) (describe-face symbol))))
1212     (when (or (boundp symbol) (not fdoc))
1213       (describe-variable symbol)
1214       ;; We now have a help buffer on the variable.  Insert the function
1215       ;; text before it.
1216       (when (or fdoc facedoc)
1217         (with-current-buffer "*Help*"
1218           (goto-char (point-min))
1219           (let ((inhibit-read-only t))
1220             (when fdoc
1221               (insert fdoc "\n\n"))
1222             (when facedoc
1223               (insert (make-string 30 ?-) "\n\n" (symbol-name symbol)
1224                       " is also a " "face." "\n\n" facedoc "\n\n"))
1225             (insert (make-string 30 ?-) "\n\n" (symbol-name symbol)
1226                     " is also a " "variable." "\n\n"))
1227           (help-setup-xref (list #'help-xref-interned symbol) nil))))))
1228
1229 (defun help-xref-mode (buffer)
1230   "Do a `describe-mode' for the specified BUFFER."
1231   (save-excursion
1232     (set-buffer buffer)
1233     (describe-mode)))
1234 \f
1235 ;;; Navigation/hyperlinking with xrefs
1236
1237 (defun help-follow-mouse (click)
1238   "Follow the cross-reference that you click on."
1239   (interactive "e")
1240   (let* ((start (event-start click))
1241          (window (car start))
1242          (pos (car (cdr start))))
1243     (with-current-buffer (window-buffer window)
1244       (help-follow pos))))
1245
1246 (defun help-xref-go-back (buffer)
1247   "From BUFFER, go back to previous help buffer text using `help-xref-stack'."
1248   (let (item position method args)
1249     (with-current-buffer buffer
1250       (when help-xref-stack
1251         (setq help-xref-stack (cdr help-xref-stack)) ; due to help-follow
1252         (setq item (pop help-xref-stack)
1253               position (car item)
1254               method (cadr item)
1255               args (cddr item))))
1256     (apply method args)
1257     ;; We assume that the buffer we just recreated has the saved name,
1258     ;; which might not always be true.
1259     (when (get-buffer (cdr position))
1260       (with-current-buffer (cdr position)
1261         (goto-char (car position))))))
1262
1263 (defun help-go-back ()
1264   "Invoke the [back] button (if any) in the Help mode buffer."
1265   (interactive)
1266   (help-follow (1- (point-max))))
1267
1268 (defun help-follow (&optional pos)
1269   "Follow cross-reference at POS, defaulting to point.
1270
1271 For the cross-reference format, see `help-make-xrefs'."
1272   (interactive "d")
1273   (unless pos
1274     (setq pos (point)))
1275   (let* ((help-data
1276           (or (and (not (= pos (point-max)))
1277                    (get-text-property pos 'help-xref))
1278               (and (not (= pos (point-min)))
1279                    (get-text-property (1- pos) 'help-xref))
1280               ;; check if the symbol under point is a function or variable
1281               (let ((sym
1282                      (intern
1283                       (save-excursion
1284                         (goto-char pos) (skip-syntax-backward "w_")
1285                         (buffer-substring (point)
1286                                           (progn (skip-syntax-forward "w_")
1287                                                  (point)))))))
1288                 (when (or (boundp sym) (fboundp sym))
1289                   (list #'help-xref-interned sym)))))
1290          (method (car help-data))
1291          (args (cdr help-data)))
1292     (when help-data
1293       (setq help-xref-stack (cons (cons (cons pos (buffer-name))
1294                                         help-xref-stack-item)
1295                                   help-xref-stack))
1296       (setq help-xref-stack-item nil)
1297       ;; There is a reference at point.  Follow it.
1298       (let ((help-xref-following t))
1299         (apply method args)))))
1300
1301 ;; For tabbing through buffer.
1302 (defun help-next-ref ()
1303   "Find the next help cross-reference in the buffer."
1304   (interactive)
1305   (let (pos)
1306     (while (not pos)
1307       (if (get-text-property (point) 'help-xref) ; move off reference
1308            (goto-char (or (next-single-property-change (point) 'help-xref)
1309                           (point))))
1310       (cond ((setq pos (next-single-property-change (point) 'help-xref))
1311              (if pos (goto-char pos)))
1312             ((bobp)
1313              (message "No cross references in the buffer.")
1314              (setq pos t))
1315             (t                          ; be circular
1316              (goto-char (point-min)))))))
1317
1318 (defun help-previous-ref ()
1319   "Find the previous help cross-reference in the buffer."
1320   (interactive)
1321   (let (pos)
1322     (while (not pos)
1323       (if (get-text-property (point) 'help-xref) ; move off reference
1324           (goto-char (or (previous-single-property-change (point) 'help-xref)
1325                          (point))))
1326       (cond ((setq pos (previous-single-property-change (point) 'help-xref))
1327              (if pos (goto-char pos)))
1328             ((bobp)
1329              (message "No cross references in the buffer.")
1330              (setq pos t))
1331             (t                          ; be circular
1332              (goto-char (point-max)))))))
1333
1334 \f
1335 ;;; Automatic resizing of temporary buffers.
1336
1337 (defcustom temp-buffer-resize-mode nil
1338   "Non-nil means resize windows displaying temporary buffers.
1339 This makes the window the right height for its contents, but never
1340 more than `temp-buffer-max-height' nor less than `window-min-height'.
1341 This applies to `help', `apropos' and `completion' buffers, and some others.
1342
1343 Setting this variable directly does not take effect;
1344 use either \\[customize] or the function `temp-buffer-resize-mode'."
1345   :get (lambda (symbol)
1346          (and (memq 'resize-temp-buffer-window temp-buffer-show-hook) t))
1347   :set (lambda (symbol value)
1348          (temp-buffer-resize-mode (if value 1 -1)))
1349   :initialize 'custom-initialize-default
1350   :type 'boolean
1351   :group 'help
1352   :version "20.4")
1353
1354 (defcustom temp-buffer-max-height (lambda (buffer) (/ (- (frame-height) 2) 2))
1355   "*Maximum height of a window displaying a temporary buffer.
1356 This is the maximum height (in text lines) which `resize-temp-buffer-window'
1357 will give to a window displaying a temporary buffer.
1358 It can also be a function which will be called with the object corresponding
1359 to the buffer to be displayed as argument and should return an integer
1360 positive number."
1361   :type '(choice integer function)
1362   :group 'help
1363   :version "20.4")
1364
1365 (defun temp-buffer-resize-mode (arg)
1366   "Toggle the mode which that makes windows smaller for temporary buffers.
1367 With prefix argument ARG, turn the resizing of windows displaying temporary
1368 buffers on if ARG is positive or off otherwise.
1369 See the documentation of the variable `temp-buffer-resize-mode' for
1370 more information."
1371   (interactive "P")
1372   (let ((turn-it-on
1373          (if (null arg)
1374              (not (memq 'resize-temp-buffer-window temp-buffer-show-hook))
1375            (> (prefix-numeric-value arg) 0))))
1376     (if turn-it-on
1377         (progn
1378           ;; `help-mode-maybe' may add a `back' button and thus increase the
1379           ;; text size, so `resize-temp-buffer-window' must be run *after* it.
1380           (add-hook 'temp-buffer-show-hook 'resize-temp-buffer-window 'append)
1381           (setq temp-buffer-resize-mode t))
1382       (remove-hook 'temp-buffer-show-hook 'resize-temp-buffer-window)
1383       (setq temp-buffer-resize-mode nil))))
1384
1385 (defun resize-temp-buffer-window ()
1386   "Resize the current window to fit its contents.
1387 Will not make it higher than `temp-buffer-max-height' nor smaller than
1388 `window-min-height'.  Do nothing if it is the only window on its frame, if it
1389 is not as wide as the frame or if some of the window's contents are scrolled
1390 out of view."
1391   (unless (or (one-window-p 'nomini)
1392               (not (pos-visible-in-window-p (point-min)))
1393               (/=  (frame-width) (window-width)))
1394     (let* ((max-height (if (functionp temp-buffer-max-height)
1395                            (funcall temp-buffer-max-height (current-buffer))
1396                          temp-buffer-max-height))
1397            (win-height (1- (window-height)))
1398            (min-height (1- window-min-height))
1399            (text-height (count-screen-lines))
1400            (new-height (max (min text-height max-height) min-height)))
1401       (enlarge-window (- new-height win-height)))))
1402
1403 ;; `help-manyarg-func-alist' is defined primitively (in doc.c).
1404 ;; New primitives with `MANY' or `UNEVALLED' arglists should be added
1405 ;; to this alist.
1406 ;; The parens and function name are redundant, but it's messy to add
1407 ;; them in `documentation'.
1408 (defconst help-manyarg-func-alist
1409   (purecopy
1410    '((list . "(list &rest OBJECTS)")
1411      (vector . "(vector &rest OBJECTS)")
1412      (make-byte-code . "(make-byte-code &rest ELEMENTS)")
1413      (call-process
1414       . "(call-process PROGRAM &optional INFILE BUFFER DISPLAY &rest ARGS)")
1415      (call-process-region
1416       . "(call-process-region START END PROGRAM &optional DELETE BUFFER DISPLAY &rest ARGS)")
1417      (string . "(string &rest CHARACTERS)")
1418      (+ . "(+ &rest NUMBERS-OR-MARKERS)")
1419      (- . "(- &optional NUMBER-OR-MARKER &rest MORE-NUMBERS-OR-MARKERS)")
1420      (* . "(* &rest NUMBERS-OR-MARKERS)")
1421      (/ . "(/ DIVIDEND DIVISOR &rest DIVISORS)")
1422      (max . "(max NUMBER-OR-MARKER &rest NUMBERS-OR-MARKERS)")
1423      (min . "(min NUMBER-OR-MARKER &rest NUMBERS-OR-MARKERS)")
1424      (logand . "(logand &rest INTS-OR-MARKERS)")
1425      (logior . "(logior &rest INTS-OR-MARKERS)")
1426      (logxor . "(logxor &rest INTS-OR-MARKERS)")
1427      (encode-time
1428       . "(encode-time SECOND MINUTE HOUR DAY MONTH YEAR &optional ZONE)")
1429      (insert . "(insert &rest ARGS)")
1430      (insert-before-markers . "(insert-before-markers &rest ARGS)")
1431      (message . "(message STRING &rest ARGUMENTS)")
1432      (message-box . "(message-box STRING &rest ARGUMENTS)")
1433      (message-or-box . "(message-or-box STRING &rest ARGUMENTS)")
1434      (propertize . "(propertize STRING &rest PROPERTIES)")
1435      (format . "(format STRING &rest OBJECTS)")
1436      (apply . "(apply FUNCTION &rest ARGUMENTS)")
1437      (run-hooks . "(run-hooks &rest HOOKS)")
1438      (run-hook-with-args . "(run-hook-with-args HOOK &rest ARGS)")
1439      (run-hook-with-args-until-failure
1440       . "(run-hook-with-args-until-failure HOOK &rest ARGS)")
1441      (run-hook-with-args-until-success
1442       . "(run-hook-with-args-until-success HOOK &rest ARGS)")
1443      (funcall . "(funcall FUNCTION &rest ARGUMENTS)")
1444      (append . "(append &rest SEQUENCES)")
1445      (concat . "(concat &rest SEQUENCES)")
1446      (vconcat . "(vconcat vconcat)")
1447      (nconc . "(nconc &rest LISTS)")
1448      (widget-apply . "(widget-apply WIDGET PROPERTY &rest ARGS)")
1449      (make-hash-table . "(make-hash-table &rest KEYWORD-ARGS)")
1450      (insert-string . "(insert-string &rest ARGS)")
1451      (start-process . "(start-process NAME BUFFER PROGRAM &rest PROGRAM-ARGS)")
1452      (setq-default . "(setq-default SYMBOL VALUE [SYMBOL VALUE...])")
1453      (save-excursion . "(save-excursion &rest BODY)")
1454      (save-current-buffer . "(save-current-buffer &rest BODY)")
1455      (save-restriction . "(save-restriction &rest BODY)")
1456      (or . "(or CONDITIONS ...)")
1457      (and . "(and CONDITIONS ...)")
1458      (if . "(if COND THEN ELSE...)")
1459      (cond . "(cond CLAUSES...)")
1460      (progn . "(progn BODY ...)")
1461      (prog1 . "(prog1 FIRST BODY...)")
1462      (prog2 . "(prog2 X Y BODY...)")
1463      (setq . "(setq SYM VAL SYM VAL ...)")
1464      (quote . "(quote ARG)")
1465      (function . "(function ARG)")
1466      (defun . "(defun NAME ARGLIST [DOCSTRING] BODY...)")
1467      (defmacro . "(defmacro NAME ARGLIST [DOCSTRING] BODY...)")
1468      (defvar . "(defvar SYMBOL [INITVALUE DOCSTRING])")
1469      (defconst . "(defconst SYMBOL INITVALUE [DOCSTRING])")
1470      (let* . "(let* VARLIST BODY...)")
1471      (let . "(let VARLIST BODY...)")
1472      (while . "(while TEST BODY...)")
1473      (catch . "(catch TAG BODY...)")
1474      (unwind-protect . "(unwind-protect BODYFORM UNWINDFORMS...)")
1475      (condition-case . "(condition-case VAR BODYFORM HANDLERS...)")
1476      (track-mouse . "(track-mouse BOFY ...)")
1477      (ml-if . "(ml-if COND THEN ELSE...)")
1478      (ml-provide-prefix-argument . "(ml-provide-prefix-argument ARG1 ARG2)")
1479      (with-output-to-temp-buffer
1480          . "(with-output-to-temp-buffer BUFFNAME BODY ...)")
1481      (save-window-excursion . "(save-window-excursion BODY ...)"))))
1482
1483 ;;; help.el ends here