lisp/help.el

   1 ;;; help.el --- help commands for Emacs
   2
   3 ;; Copyright (C) 1985, 1986, 1993, 1994, 1998 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
  36 (defvar help-map (make-sparse-keymap)
  37   "Keymap for characters following the Help key.")
  38
  39 (defvar help-mode-map (make-sparse-keymap)
  40   "Keymap for help mode.")
  41
  42 (define-key global-map (char-to-string help-char) 'help-command)
  43 (define-key global-map [help] 'help-command)
  44 (define-key global-map [f1] 'help-command)
  45 (fset 'help-command help-map)
  46
  47 (define-key help-map (char-to-string help-char) 'help-for-help)
  48 (define-key help-map [help] 'help-for-help)
  49 (define-key help-map [f1] 'help-for-help)
  50 (define-key help-map "?" 'help-for-help)
  51
  52 (define-key help-map "\C-c" 'describe-copying)
  53 (define-key help-map "\C-d" 'describe-distribution)
  54 (define-key help-map "\C-w" 'describe-no-warranty)
  55 (define-key help-map "\C-p" 'describe-project)
  56 (define-key help-map "a" 'apropos-command)
  57
  58 (define-key help-map "b" 'describe-bindings)
  59
  60 (define-key help-map "c" 'describe-key-briefly)
  61 (define-key help-map "k" 'describe-key)
  62
  63 (define-key help-map "d" 'describe-function)
  64 (define-key help-map "f" 'describe-function)
  65
  66 (define-key help-map "F" 'view-emacs-FAQ)
  67
  68 (define-key help-map "i" 'info)
  69 (define-key help-map "\C-f" 'Info-goto-emacs-command-node)
  70 (define-key help-map "\C-k" 'Info-goto-emacs-key-command-node)
  71 (define-key help-map "\C-i" 'info-lookup-symbol)
  72
  73 (define-key help-map "l" 'view-lossage)
  74
  75 (define-key help-map "m" 'describe-mode)
  76
  77 (define-key help-map "\C-n" 'view-emacs-news)
  78 (define-key help-map "n" 'view-emacs-news)
  79
  80 (define-key help-map "p" 'finder-by-keyword)
  81 (autoload 'finder-by-keyword "finder"
  82   "Find packages matching a given keyword." t)
  83
  84 (define-key help-map "s" 'describe-syntax)
  85
  86 (define-key help-map "t" 'help-with-tutorial)
  87
  88 (define-key help-map "w" 'where-is)
  89
  90 (define-key help-map "v" 'describe-variable)
  91
  92 (define-key help-map "q" 'help-quit)
  93
  94 (define-key help-mode-map [mouse-2] 'help-follow-mouse)
  95 (define-key help-mode-map "\C-c\C-b" 'help-go-back)
  96 (define-key help-mode-map "\C-c\C-c" 'help-follow)
  97 (define-key help-mode-map "\t" 'help-next-ref)
  98 (define-key help-mode-map [backtab] 'help-previous-ref)
  99 (define-key help-mode-map [(shift tab)] 'help-previous-ref)
 100 ;; Documentation only, since we use minor-mode-overriding-map-alist.
 101 (define-key help-mode-map "\r" 'help-follow)
 102
 103 ;; Font-locking is incompatible with the new xref stuff.
 104 ;(defvar help-font-lock-keywords
 105 ;  (eval-when-compile
 106 ;    (let ((name-char "[-+a-zA-Z0-9_*]") (sym-char "[-+a-zA-Z0-9_:*]"))
 107 ;      (list
 108 ;       ;;
 109 ;       ;; The symbol itself.
 110 ;       (list (concat "\\`\\(" name-char "+\\)\\(\\(:\\)\\|\\('\\)\\)")
 111 ;            '(1 (if (match-beginning 3)
 112 ;                    font-lock-function-name-face
 113 ;                  font-lock-variable-name-face)))
 114 ;       ;;
 115 ;       ;; Words inside `' which tend to be symbol names.
 116 ;       (list (concat "`\\(" sym-char sym-char "+\\)'")
 117 ;            1 'font-lock-constant-face t)
 118 ;       ;;
 119 ;       ;; CLisp `:' keywords as references.
 120 ;       (list (concat "\\<:" sym-char "+\\>") 0 'font-lock-builtin-face t))))
 121 ;  "Default expressions to highlight in Help mode.")
 122
 123 (defvar help-xref-stack nil
 124   "A stack of ways by which to return to help buffers after following xrefs.
 125 Used by `help-follow' and `help-xref-go-back'.")
 126 (put 'help-xref-stack 'permanent-local t)
 127
 128 (defvar help-xref-stack-item nil
 129   "An item for `help-follow' in this buffer to push onto `help-xref-stack'.")
 130 (put 'help-xref-stack-item 'permanent-local t)
 131
 132 (setq-default help-xref-stack nil help-xref-stack-item nil)
 133
 134 (defun help-mode ()
 135   "Major mode for viewing help text and navigating references in it.
 136 Entry to this mode runs the normal hook `help-mode-hook'.
 137 Commands:
 138 \\{help-mode-map}"
 139   (interactive)
 140   (kill-all-local-variables)
 141   (use-local-map help-mode-map)
 142   (setq mode-name "Help")
 143   (setq major-mode 'help-mode)
 144   (make-local-variable 'font-lock-defaults)
 145   (setq font-lock-defaults nil)         ; font-lock would defeat xref
 146   (view-mode)
 147   (make-local-variable 'view-no-disable-on-exit)
 148   (setq view-no-disable-on-exit t)
 149   ;; `help-make-xrefs' would be run here if not invoked from
 150   ;; `help-mode-maybe'.
 151   (run-hooks 'help-mode-hook))
 152
 153 (defun help-mode-maybe ()
 154   (if (eq major-mode 'fundamental-mode)
 155       (help-mode))
 156   (when (eq major-mode 'help-mode)
 157     ;; View mode's read-only status of existing *Help* buffer is lost
 158     ;; by with-output-to-temp-buffer.
 159     (toggle-read-only 1)
 160     (help-make-xrefs (current-buffer)))
 161   (setq view-return-to-alist
 162         (list (cons (selected-window) help-return-method))))
 163
 164 (add-hook 'temp-buffer-show-hook 'help-mode-maybe)
 165
 166 (defun help-quit ()
 167   (interactive)
 168   nil)
 169
 170 (defun help-with-tutorial (&optional arg)
 171   "Select the Emacs learn-by-doing tutorial.
 172 If there is a tutorial version written in the language
 173 of the selected language environment, that version is used.
 174 If there's no tutorial in that language, `TUTORIAL' is selected.
 175 With arg, you are asked to choose which language."
 176   (interactive "P")
 177   (let ((lang (if arg
 178                   (read-language-name 'tutorial "Language: " "English")
 179                 (if (get-language-info current-language-environment 'tutorial)
 180                     current-language-environment
 181                   "English")))
 182         file filename)
 183     (setq filename (get-language-info lang 'tutorial))
 184     (setq file (expand-file-name (concat "~/" filename)))
 185     (delete-other-windows)
 186     (if (get-file-buffer file)
 187         (switch-to-buffer (get-file-buffer file))
 188       (switch-to-buffer (create-file-buffer file))
 189       (setq buffer-file-name file)
 190       (setq default-directory (expand-file-name "~/"))
 191       (setq buffer-auto-save-file-name nil)
 192       (insert-file-contents (expand-file-name filename data-directory))
 193       (goto-char (point-min))
 194       (search-forward "\n<<")
 195       (beginning-of-line)
 196       (delete-region (point) (progn (end-of-line) (point)))
 197       (let ((n (- (window-height (selected-window))
 198                   (count-lines (point-min) (point))
 199                   6)))
 200         (if (< n 12)
 201             (newline n)
 202           ;; Some people get confused by the large gap.
 203           (newline (/ n 2))
 204           (insert "[Middle of page left blank for didactic purposes.  "
 205                   "Text continues below]")
 206           (newline (- n (/ n 2)))))
 207       (goto-char (point-min))
 208       (set-buffer-modified-p nil))))
 209
 210 (defun describe-key-briefly (key &optional insert)
 211   "Print the name of the function KEY invokes.  KEY is a string.
 212 If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
 213   (interactive "kDescribe key briefly: \nP")
 214   ;; If this key seq ends with a down event, discard the
 215   ;; following click or drag event.  Otherwise that would
 216   ;; erase the message.
 217   (let ((type (aref key (1- (length key)))))
 218     (if (listp type) (setq type (car type)))
 219     (and (symbolp type)
 220          (memq 'down (event-modifiers type))
 221          (read-event)))
 222   (save-excursion
 223     (let ((modifiers (event-modifiers (aref key 0)))
 224           (standard-output (if insert (current-buffer) t))
 225           window position)
 226       ;; For a mouse button event, go to the button it applies to
 227       ;; to get the right key bindings.  And go to the right place
 228       ;; in case the keymap depends on where you clicked.
 229       (if (or (memq 'click modifiers) (memq 'down modifiers)
 230               (memq 'drag modifiers))
 231           (setq window (posn-window (event-start (aref key 0)))
 232                 position (posn-point (event-start (aref key 0)))))
 233       (if (windowp window)
 234           (progn
 235             (set-buffer (window-buffer window))
 236             (goto-char position)))
 237       ;; Ok, now look up the key and name the command.
 238       (let ((defn (key-binding key))
 239             (key-desc (key-description key)))
 240         (if (or (null defn) (integerp defn))
 241             (princ (format "%s is undefined" key-desc))
 242           (princ (format (if insert
 243                              "`%s' (`%s')"
 244                            (if (windowp window)
 245                                "%s at that spot runs the command %s"
 246                              "%s runs the command %s"))
 247                          key-desc
 248                          (if (symbolp defn) defn (prin1-to-string defn)))))))))
 249
 250 (defvar help-return-method nil
 251   "What to do to \"exit\" the help buffer.
 252 This is a list
 253  (WINDOW . t)              delete the selected window, go to WINDOW.
 254  (WINDOW . quit-window)    do quit-window, then select WINDOW.
 255  (WINDOW BUF START POINT)  display BUF at START, POINT, then select WINDOW.")
 256
 257 (defun print-help-return-message (&optional function)
 258   "Display or return message saying how to restore windows after help command.
 259 Computes a message and applies the optional argument FUNCTION to it.
 260 If FUNCTION is nil, applies `message' to it, thus printing it."
 261   (and (not (get-buffer-window standard-output))
 262        (let ((first-message
 263               (cond ((special-display-p (buffer-name standard-output))
 264                      (setq help-return-method (cons (selected-window) t))
 265                      ;; If the help output buffer is a special display buffer,
 266                      ;; don't say anything about how to get rid of it.
 267                      ;; First of all, the user will do that with the window
 268                      ;; manager, not with Emacs.
 269                      ;; Secondly, the buffer has not been displayed yet,
 270                      ;; so we don't know whether its frame will be selected.
 271                      nil)
 272                     ((not (one-window-p t))
 273                      (setq help-return-method
 274                            (cons (selected-window) 'quit-window))
 275                      "Type \\[switch-to-buffer-other-window] RET to restore the other window.")
 276                     (pop-up-windows
 277                      (setq help-return-method (cons (selected-window) t))
 278                      "Type \\[delete-other-windows] to remove help window.")
 279                     (t
 280                      (setq help-return-method
 281                            (list (selected-window) (window-buffer)
 282                                  (window-start) (window-point)))
 283                      "Type \\[switch-to-buffer] RET to remove help window."))))
 284          (funcall (or function 'message)
 285                   (concat
 286                    (if first-message
 287                        (substitute-command-keys first-message)
 288                      "")
 289                    (if first-message "  " "")
 290                    ;; If the help buffer will go in a separate frame,
 291                    ;; it's no use mentioning a command to scroll, so don't.
 292                    (if (special-display-p (buffer-name standard-output))
 293                        nil
 294                      (if (same-window-p (buffer-name standard-output))
 295                          ;; Say how to scroll this window.
 296                          (substitute-command-keys
 297                           "\\[scroll-up] to scroll the help.")
 298                        ;; Say how to scroll some other window.
 299                        (substitute-command-keys
 300                         "\\[scroll-other-window] to scroll the help."))))))))
 301
 302 (defun describe-key (key)
 303   "Display documentation of the function invoked by KEY.  KEY is a string."
 304   (interactive "kDescribe key: ")
 305   ;; If this key seq ends with a down event, discard the
 306   ;; following click or drag event.  Otherwise that would
 307   ;; erase the message.
 308   (let ((type (aref key (1- (length key)))))
 309     (if (listp type) (setq type (car type)))
 310     (and (symbolp type)
 311          (memq 'down (event-modifiers type))
 312          (read-event)))
 313   (save-excursion
 314     (let ((modifiers (event-modifiers (aref key 0)))
 315           window position)
 316       ;; For a mouse button event, go to the button it applies to
 317       ;; to get the right key bindings.  And go to the right place
 318       ;; in case the keymap depends on where you clicked.
 319       (if (or (memq 'click modifiers) (memq 'down modifiers)
 320               (memq 'drag modifiers))
 321           (setq window (posn-window (event-start (aref key 0)))
 322                 position (posn-point (event-start (aref key 0)))))
 323       (if (windowp window)
 324           (progn
 325             (set-buffer (window-buffer window))
 326             (goto-char position)))
 327       (let ((defn (key-binding key)))
 328         (if (or (null defn) (integerp defn))
 329             (message "%s is undefined" (key-description key))
 330           (with-output-to-temp-buffer "*Help*"
 331             (princ (key-description key))
 332             (if (windowp window)
 333                 (princ " at that spot"))
 334             (princ " runs the command ")
 335             (prin1 defn)
 336             (princ "\n   which is ")
 337             (describe-function-1 defn nil)
 338             (print-help-return-message)))))))
 339
 340 (defun describe-mode ()
 341   "Display documentation of current major mode and minor modes.
 342 For this to work correctly for a minor mode, the mode's indicator variable
 343 \(listed in `minor-mode-alist') must also be a function whose documentation
 344 describes the minor mode."
 345   (interactive)
 346   (with-output-to-temp-buffer "*Help*"
 347     (let ((minor-modes minor-mode-alist)
 348           (first t))
 349       (while minor-modes
 350         (let* ((minor-mode (car (car minor-modes)))
 351                (indicator (car (cdr (car minor-modes)))))
 352           ;; Document a minor mode if it is listed in minor-mode-alist,
 353           ;; bound locally in this buffer, non-nil, and has a function
 354           ;; definition.
 355           (if (and (symbol-value minor-mode)
 356                    (fboundp minor-mode))
 357               (let ((pretty-minor-mode minor-mode))
 358                 (if (string-match "-mode$" (symbol-name minor-mode))
 359                     (setq pretty-minor-mode
 360                           (capitalize
 361                            (substring (symbol-name minor-mode)
 362                                       0 (match-beginning 0)))))
 363                 (while (and indicator (symbolp indicator))
 364                   (setq indicator (symbol-value indicator)))
 365                 (if first
 366                     (princ "The minor modes are described first,
 367 followed by the major mode, which is described on the last page.\n\f\n"))
 368                 (setq first nil)
 369                 (princ (format "%s minor mode (%s):\n"
 370                                pretty-minor-mode
 371                                (if indicator
 372                                    (format "indicator%s" indicator)
 373                                  "no indicator")))
 374                 (princ (documentation minor-mode))
 375                 (princ "\n\f\n"))))
 376         (setq minor-modes (cdr minor-modes))))
 377     (princ mode-name)
 378     (princ " mode:\n")
 379     (princ (documentation major-mode))
 380     (help-setup-xref (cons #'help-xref-mode (current-buffer)) (interactive-p))
 381     (print-help-return-message)))
 382
 383 ;; So keyboard macro definitions are documented correctly
 384 (fset 'defining-kbd-macro (symbol-function 'start-kbd-macro))
 385
 386 (defun describe-distribution ()
 387   "Display info on how to obtain the latest version of GNU Emacs."
 388   (interactive)
 389   (find-file-read-only
 390    (expand-file-name "DISTRIB" data-directory)))
 391
 392 (defun describe-copying ()
 393   "Display info on how you may redistribute copies of GNU Emacs."
 394   (interactive)
 395   (find-file-read-only
 396    (expand-file-name "COPYING" data-directory))
 397   (goto-char (point-min)))
 398
 399 (defun describe-project ()
 400   "Display info on the GNU project."
 401   (interactive)
 402   (find-file-read-only
 403    (expand-file-name "GNU" data-directory))
 404   (goto-char (point-min)))
 405
 406 (defun describe-no-warranty ()
 407   "Display info on all the kinds of warranty Emacs does NOT have."
 408   (interactive)
 409   (describe-copying)
 410   (let (case-fold-search)
 411     (search-forward "NO WARRANTY")
 412     (recenter 0)))
 413
 414 (defun describe-prefix-bindings ()
 415   "Describe the bindings of the prefix used to reach this command.
 416 The prefix described consists of all but the last event
 417 of the key sequence that ran this command."
 418   (interactive)
 419   (let* ((key (this-command-keys)))
 420     (describe-bindings
 421      (if (stringp key)
 422          (substring key 0 (1- (length key)))
 423        (let ((prefix (make-vector (1- (length key)) nil))
 424              (i 0))
 425          (while (< i (length prefix))
 426            (aset prefix i (aref key i))
 427            (setq i (1+ i)))
 428          prefix)))))
 429 ;; Make C-h after a prefix, when not specifically bound,
 430 ;; run describe-prefix-bindings.
 431 (setq prefix-help-command 'describe-prefix-bindings)
 432
 433 (defun view-emacs-news (&optional arg)
 434   "Display info on recent changes to Emacs.
 435 With numeric argument display information on correspondingly older changes."
 436   (interactive "P")
 437   (let* ((arg (if arg (prefix-numeric-value arg) 0)))
 438     (find-file-read-only
 439      (expand-file-name (concat (make-string arg ?O) "NEWS")
 440                        data-directory))))
 441
 442 (defun view-emacs-FAQ ()
 443   "Display the Emacs Frequently Asked Questions (FAQ) file."
 444   (interactive)
 445   (find-file-read-only (expand-file-name "FAQ" data-directory)))
 446
 447 (defun view-lossage ()
 448   "Display last 100 input keystrokes."
 449   (interactive)
 450   (with-output-to-temp-buffer "*Help*"
 451     (princ (mapconcat (function (lambda (key)
 452                                   (if (or (integerp key)
 453                                           (symbolp key)
 454                                           (listp key))
 455                                       (single-key-description key)
 456                                     (prin1-to-string key nil))))
 457                       (recent-keys)
 458                       " "))
 459     (save-excursion
 460       (set-buffer standard-output)
 461       (goto-char (point-min))
 462       (while (progn (move-to-column 50) (not (eobp)))
 463         (search-forward " " nil t)
 464         (insert "\n"))
 465       (setq help-xref-stack nil
 466             help-xref-stack-item nil))
 467     (print-help-return-message)))
 468
 469 (defalias 'help 'help-for-help)
 470 (make-help-screen help-for-help
 471   "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:"
 472   "You have typed \\[help-command], the help character.  Type a Help option:
 473 \(Use SPC or DEL to scroll through this text.  Type \\<help-map>\\[help-quit] to exit the Help command.)
 474
 475 a  command-apropos.  Give a substring, and see a list of commands
 476         (functions interactively callable) that contain
 477         that substring.  See also the  apropos  command.
 478 b  describe-bindings.  Display table of all key bindings.
 479 c  describe-key-briefly.  Type a command key sequence;
 480         it prints the function name that sequence runs.
 481 C  describe-coding-system.  This describes either a specific coding system
 482         (if you type its name) or the coding systems currently in use
 483         (if you type just RET).
 484 f  describe-function.  Type a function name and get documentation of it.
 485 C-f Info-goto-emacs-command-node.  Type a function name;
 486         it takes you to the Info node for that command.
 487 i  info. The  info  documentation reader.
 488 I  describe-input-method.  Describe a specific input method (if you type
 489         its name) or the current input method (if you type just RET).
 490 k  describe-key.  Type a command key sequence;
 491         it displays the full documentation.
 492 C-k Info-goto-emacs-key-command-node.  Type a command key sequence;
 493         it takes you to the Info node for the command bound to that key.
 494 l  view-lossage.  Shows last 100 characters you typed.
 495 L  describe-language-environment.  This describes either the a
 496         specific language environment (if you type its name)
 497         or the current language environment (if you type just RET).
 498 m  describe-mode.  Print documentation of current minor modes,
 499         and the current major mode, including their special commands.
 500 n  view-emacs-news.  Shows emacs news file.
 501 p  finder-by-keyword. Find packages matching a given topic keyword.
 502 s  describe-syntax.  Display contents of syntax table, plus explanations
 503 t  help-with-tutorial.  Select the Emacs learn-by-doing tutorial.
 504 v  describe-variable.  Type name of a variable;
 505         it displays the variable's documentation and value.
 506 w  where-is.  Type command name; it prints which keystrokes
 507         invoke that command.
 508
 509 F  Display the frequently asked questions file.
 510 h  Display the HELLO file which illustrates various scripts.
 511 C-c Display Emacs copying permission (General Public License).
 512 C-d Display Emacs ordering information.
 513 C-n Display news of recent Emacs changes.
 514 C-p Display information about the GNU project.
 515 C-w Display information on absence of warranty for GNU Emacs."
 516   help-map)
 517
 518 ;; Return a function which is called by the list containing point.
 519 ;; If that gives no function, return a function whose name is around point.
 520 ;; If that doesn't give a function, return nil.
 521 (defun function-called-at-point ()
 522   (let ((stab (syntax-table)))
 523     (set-syntax-table emacs-lisp-mode-syntax-table)
 524     (unwind-protect
 525         (or (condition-case ()
 526                 (save-excursion
 527                   (save-restriction
 528                     (narrow-to-region (max (point-min) (- (point) 1000)) (point-max))
 529                     ;; Move up to surrounding paren, then after the open.
 530                     (backward-up-list 1)
 531                     (forward-char 1)
 532                     ;; If there is space here, this is probably something
 533                     ;; other than a real Lisp function call, so ignore it.
 534                     (if (looking-at "[ \t]")
 535                         (error "Probably not a Lisp function call"))
 536                     (let (obj)
 537                       (setq obj (read (current-buffer)))
 538                       (and (symbolp obj) (fboundp obj) obj))))
 539               (error nil))
 540             (condition-case ()
 541                 (save-excursion
 542                   (or (not (zerop (skip-syntax-backward "_w")))
 543                       (eq (char-syntax (following-char)) ?w)
 544                       (eq (char-syntax (following-char)) ?_)
 545                       (forward-sexp -1))
 546                   (skip-chars-forward "'")
 547                   (let ((obj (read (current-buffer))))
 548                     (and (symbolp obj) (fboundp obj) obj)))
 549               (error nil)))
 550       (set-syntax-table stab))))
 551
 552 (defun describe-function-find-file (function)
 553   (let ((files load-history)
 554         file functions)
 555     (while files
 556       (if (memq function (cdr (car files)))
 557           (setq file (car (car files)) files nil))
 558       (setq files (cdr files)))
 559     file))
 560
 561 (defun describe-function (function)
 562   "Display the full documentation of FUNCTION (a symbol)."
 563   (interactive
 564    (let ((fn (function-called-at-point))
 565          (enable-recursive-minibuffers t)
 566          val)
 567      (setq val (completing-read (if fn
 568                                     (format "Describe function (default %s): " fn)
 569                                   "Describe function: ")
 570                                 obarray 'fboundp t nil nil (symbol-name fn)))
 571      (list (if (equal val "")
 572                fn (intern val)))))
 573   (if function
 574       (with-output-to-temp-buffer "*Help*"
 575         (prin1 function)
 576         ;; Use " is " instead of a colon so that
 577         ;; it is easier to get out the function name using forward-sexp.
 578         (princ " is ")
 579         (describe-function-1 function nil)
 580         (print-help-return-message)
 581         (save-excursion
 582           (set-buffer standard-output)
 583           ;; Return the text we displayed.
 584           (buffer-string)))
 585     (message "You didn't specify a function")))
 586
 587 (defun describe-function-1 (function parens)
 588   (let* ((def (symbol-function function))
 589          file-name string need-close
 590          (beg (if (commandp def) "an interactive " "a ")))
 591     (setq string
 592           (cond ((or (stringp def)
 593                      (vectorp def))
 594                  "a keyboard macro")
 595                 ((subrp def)
 596                  (concat beg "built-in function"))
 597                 ((byte-code-function-p def)
 598                  (concat beg "compiled Lisp function"))
 599                 ((symbolp def)
 600                  (format "alias for `%s'" def))
 601                 ((eq (car-safe def) 'lambda)
 602                  (concat beg "Lisp function"))
 603                 ((eq (car-safe def) 'macro)
 604                  "a Lisp macro")
 605                 ((eq (car-safe def) 'mocklisp)
 606                  "a mocklisp function")
 607                 ((eq (car-safe def) 'autoload)
 608                  (setq file-name (nth 1 def))
 609                  (format "%s autoloaded Lisp %s"
 610                          (if (commandp def) "an interactive" "an")
 611                          (if (nth 4 def) "macro" "function")
 612                          ))
 613                 (t "")))
 614     (when (and parens (not (equal string "")))
 615       (setq need-close t)
 616       (princ "("))
 617     (princ string)
 618     (or file-name
 619         (setq file-name (describe-function-find-file function)))
 620     (if file-name
 621         (progn
 622           (princ " in `")
 623           ;; We used to add .el to the file name,
 624           ;; but that's completely wrong when the user used load-file.
 625           (princ file-name)
 626           (princ "'")
 627           ;; Make a hyperlink to the library.
 628           (with-current-buffer "*Help*"
 629             (save-excursion
 630               (re-search-backward "`\\([^`']+\\)'" nil t)
 631               (help-xref-button 1 #'(lambda (arg)
 632                                       (let ((location
 633                                              (find-function-noselect arg)))
 634                                         (display-buffer (nth 0 location))
 635                                         (goto-char (nth 1 location))))
 636                                 function)))))
 637     (if need-close (princ ")"))
 638     (princ ".")
 639     (terpri)
 640     (let* ((inner-function (if (and (listp def) 'macro)
 641                                (cdr def)
 642                              def))
 643            (arglist (cond ((byte-code-function-p inner-function)
 644                            (car (append inner-function nil)))
 645                           ((eq (car-safe inner-function) 'lambda)
 646                            (nth 1 inner-function))
 647                           (t t))))
 648       (if (listp arglist)
 649           (progn
 650             (princ (cons function
 651                          (mapcar (lambda (arg)
 652                                    (if (memq arg '(&optional &rest))
 653                                        arg
 654                                      (intern (upcase (symbol-name arg)))))
 655                                  arglist)))
 656             (terpri))))
 657     (let ((doc (documentation function)))
 658       (if doc
 659           (progn (terpri)
 660                  (princ doc)
 661                  (help-setup-xref (cons #'describe-function function) (interactive-p)))
 662         (princ "not documented")))))
 663
 664 ;; We return 0 if we can't find a variable to return.
 665 (defun variable-at-point ()
 666   (condition-case ()
 667       (let ((stab (syntax-table)))
 668         (unwind-protect
 669             (save-excursion
 670               (set-syntax-table emacs-lisp-mode-syntax-table)
 671               (or (not (zerop (skip-syntax-backward "_w")))
 672                   (eq (char-syntax (following-char)) ?w)
 673                   (eq (char-syntax (following-char)) ?_)
 674                   (forward-sexp -1))
 675               (skip-chars-forward "'")
 676               (let ((obj (read (current-buffer))))
 677                 (or (and (symbolp obj) (boundp obj) obj)
 678                     0)))
 679           (set-syntax-table stab)))
 680     (error 0)))
 681
 682 (defun describe-variable (variable)
 683   "Display the full documentation of VARIABLE (a symbol).
 684 Returns the documentation as a string, also."
 685   (interactive
 686    (let ((v (variable-at-point))
 687          (enable-recursive-minibuffers t)
 688          val)
 689      (setq val (completing-read (if (symbolp v)
 690                                     (format "Describe variable (default %s): " v)
 691                                   "Describe variable: ")
 692                                 obarray 'boundp t nil nil
 693                                 (if (symbolp v) (symbol-name v))))
 694      (list (if (equal val "")
 695                v (intern val)))))
 696   (if (symbolp variable)
 697       (let (valvoid)
 698         (with-output-to-temp-buffer "*Help*"
 699           (prin1 variable)
 700           (if (not (boundp variable))
 701               (progn
 702                 (princ " is void")
 703                 (terpri)
 704                 (setq valvoid t))
 705             (princ "'s value is ")
 706             (terpri)
 707             (pp (symbol-value variable))
 708             (terpri))
 709           (if (local-variable-p variable)
 710               (progn
 711                 (princ (format "Local in buffer %s; " (buffer-name)))
 712                 (if (not (default-boundp variable))
 713                     (princ "globally void")
 714                   (princ "global value is ")
 715                   (terpri)
 716                   (pp (default-value variable)))
 717                 (terpri)))
 718           (terpri)
 719           (save-current-buffer
 720             (set-buffer standard-output)
 721             (if (> (count-lines (point-min) (point-max)) 10)
 722                 (progn
 723                   (goto-char (point-min))
 724                   (if valvoid
 725                       (forward-line 1)
 726                     (forward-sexp 1)
 727                     (delete-region (point) (progn (end-of-line) (point)))
 728                     (insert "'s value is shown below.\n\n")
 729                     (save-excursion
 730                       (insert "\n\nValue:"))))))
 731           (princ "Documentation:")
 732           (terpri)
 733           (let ((doc (documentation-property variable 'variable-documentation)))
 734             (princ (or doc "not documented as a variable.")))
 735           (help-setup-xref (cons #'describe-variable variable) (interactive-p))
 736           (print-help-return-message)
 737           (save-excursion
 738             (set-buffer standard-output)
 739             ;; Return the text we displayed.
 740             (buffer-string))))
 741     (message "You did not specify a variable")))
 742
 743 (defun describe-bindings (&optional prefix)
 744   "Show a list of all defined keys, and their definitions.
 745 We put that list in a buffer, and display the buffer.
 746
 747 The optional argument PREFIX, if non-nil, should be a key sequence;
 748 then we display only bindings that start with that prefix."
 749   (interactive "P")
 750   (describe-bindings-internal nil prefix)
 751   (with-current-buffer "*Help*"
 752     (setq help-xref-stack nil
 753           help-xref-stack-item nil)))
 754
 755 (defun where-is (definition &optional insert)
 756   "Print message listing key sequences that invoke specified command.
 757 Argument is a command definition, usually a symbol with a function definition.
 758 If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
 759   (interactive
 760    (let ((fn (function-called-at-point))
 761          (enable-recursive-minibuffers t)
 762          val)
 763      (setq val (completing-read (if fn
 764                                     (format "Where is command (default %s): " fn)
 765                                   "Where is command: ")
 766                                 obarray 'fboundp t))
 767      (list (if (equal val "")
 768                fn (intern val))
 769            current-prefix-arg)))
 770   (let* ((keys (where-is-internal definition overriding-local-map nil nil))
 771          (keys1 (mapconcat 'key-description keys ", "))
 772          (standard-output (if insert (current-buffer) t)))
 773     (if insert
 774         (if (> (length keys1) 0)
 775             (princ (format "%s (%s)" keys1 definition))
 776           (princ (format "M-x %s RET" definition)))
 777       (if (> (length keys1) 0)
 778           (princ (format "%s is on %s" definition keys1))
 779         (princ (format "%s is not on any key" definition)))))
 780   nil)
 781
 782 (defun locate-library (library &optional nosuffix path interactive-call)
 783   "Show the precise file name of Emacs library LIBRARY.
 784 This command searches the directories in `load-path' like `M-x load-library'
 785 to find the file that `M-x load-library RET LIBRARY RET' would load.
 786 Optional second arg NOSUFFIX non-nil means don't add suffixes `.elc' or `.el'
 787 to the specified name LIBRARY.
 788
 789 If the optional third arg PATH is specified, that list of directories
 790 is used instead of `load-path'."
 791   (interactive (list (read-string "Locate library: ")
 792                      nil nil
 793                      t))
 794   (let (result)
 795     (catch 'answer
 796       (mapcar
 797        (lambda (dir)
 798          (mapcar
 799           (lambda (suf)
 800             (let ((try (expand-file-name (concat library suf) dir)))
 801               (and (file-readable-p try)
 802                    (null (file-directory-p try))
 803                    (progn
 804                      (setq result try)
 805                      (throw 'answer try)))))
 806           (if nosuffix
 807               '("")
 808             '(".elc" ".el" "")
 809 ;;; load doesn't handle this yet.
 810 ;;;         (let ((basic '(".elc" ".el" ""))
 811 ;;;               (compressed '(".Z" ".gz" "")))
 812 ;;;           ;; If autocompression mode is on,
 813 ;;;           ;; consider all combinations of library suffixes
 814 ;;;           ;; and compression suffixes.
 815 ;;;           (if (rassq 'jka-compr-handler file-name-handler-alist)
 816 ;;;               (apply 'nconc
 817 ;;;                      (mapcar (lambda (compelt)
 818 ;;;                                (mapcar (lambda (baselt)
 819 ;;;                                          (concat baselt compelt))
 820 ;;;                                        basic))
 821 ;;;                              compressed))
 822 ;;;             basic))
 823             )))
 824        (or path load-path)))
 825     (and interactive-call
 826          (if result
 827              (message "Library is file %s" result)
 828            (message "No library %s in search path" library)))
 829     result))
 830
 831 \f
 832 ;;; Grokking cross-reference information in doc strings and
 833 ;;; hyperlinking it.
 834
 835 ;; This may have some scope for extension and the same or something
 836 ;; similar should be done for widget doc strings, which currently use
 837 ;; another mechanism.
 838
 839 (defcustom help-highlight-p t
 840   "*If non-nil, `help-make-xrefs' highlight cross-references.
 841 Under a window system it highlights them with face defined by
 842 `help-highlight-face'.  On a character terminal highlighted
 843 references look like cross-references in info mode."
 844  :group 'help
 845  :version "20.3"
 846  :type 'boolean)
 847
 848 (defcustom help-highlight-face 'underline
 849   "Face used by `help-make-xrefs' to highlight cross-references.
 850 Must be previously-defined."
 851   :group 'help
 852   :version "20.3"
 853   :type 'face)
 854
 855 (defvar help-back-label "[back]"
 856   "Label to use by `help-make-xrefs' for the go-back reference.")
 857
 858 (defvar help-xref-symbol-regexp
 859   (concat "\\(\\<\\(\\(variable\\|option\\)\\|"
 860           "\\(function\\|command\\)\\|"
 861           "\\(symbol\\)\\)\\s-+\\)?"
 862           ;; Note starting with word-syntax character:
 863           "`\\(\\sw\\(\\sw\\|\\s_\\)+\\)'")
 864   "Regexp matching doc string references to symbols.
 865
 866 The words preceding the quoted symbol can be used in doc strings to
 867 distinguish references to variables, functions and symbols.")
 868
 869 (defvar help-xref-info-regexp
 870   "\\<info\\s-+node\\s-`\\([^']+\\)'"
 871   "Regexp matching doc string references to an Info node.")
 872
 873 (defun help-setup-xref (item interactive-p)
 874   "Invoked from commands using the \"*Help*\" buffer to install some xref info.
 875
 876 ITEM is a (function . args) pair appropriate for recreating the help
 877 buffer after following a reference.  INTERACTIVE-P is non-nil if the
 878 calling command was invoked interactively.  In this case the stack of
 879 items for help buffer \"back\" buttons is cleared."
 880   (if interactive-p
 881       (setq help-xref-stack nil))
 882   (setq help-xref-stack-item item))
 883
 884 (defun help-make-xrefs (&optional buffer)
 885   "Parse and hyperlink documentation cross-references in the given BUFFER.
 886
 887 Find cross-reference information in a buffer and, if
 888 `help-highlight-p' is non-nil, highlight it with face defined by
 889 `help-highlight-face'; activate such cross references for selection
 890 with `help-follow'.  Cross-references have the canonical form `...'
 891 and the type of reference may be disambiguated by the preceding
 892 word(s) used in `help-xref-symbol-regexp'.
 893
 894 A special reference `back' is made to return back through a stack of
 895 help buffers.  Variable `help-back-label' specifies the text for
 896 that."
 897   (interactive "b")
 898   (save-excursion
 899     (set-buffer (or buffer (current-buffer)))
 900     (goto-char (point-min))
 901     ;; Skip the header-type info, though it might be useful to parse
 902     ;; it at some stage (e.g. "function in `library'").
 903     (forward-paragraph)
 904     (let ((old-modified (buffer-modified-p)))
 905       (let ((stab (syntax-table))
 906             (case-fold-search t)
 907             (inhibit-read-only t))
 908         (set-syntax-table emacs-lisp-mode-syntax-table)
 909         ;; The following should probably be abstracted out.
 910         (unwind-protect
 911             (progn
 912               ;; Quoted symbols
 913               (save-excursion
 914                 (while (re-search-forward help-xref-symbol-regexp nil t)
 915                   (let* ((data (match-string 6))
 916                          (sym (intern-soft data)))
 917                     (if sym
 918                         (cond
 919                          ((match-string 3) ; `variable' &c
 920                           (and (boundp sym) ; `variable' doesn't ensure
 921                                         ; it's actually bound
 922                                (help-xref-button 6 #'describe-variable sym)))
 923                          ((match-string 4) ; `function' &c
 924                           (and (fboundp sym) ; similarly
 925                                (help-xref-button 6 #'describe-function sym)))
 926                          ((match-string 5)) ; nothing for symbol
 927                          ((and (boundp sym) (fboundp sym))
 928                           ;; We can't intuit whether to use the
 929                           ;; variable or function doc -- supply both.
 930                           (help-xref-button 6 #'help-xref-interned sym))
 931                          ((boundp sym)
 932                           (help-xref-button 6 #'describe-variable sym))
 933                          ((fboundp sym)
 934                           (help-xref-button 6 #'describe-function sym)))))))
 935               ;; Info references
 936               (save-excursion
 937                 (while (re-search-forward help-xref-info-regexp nil t)
 938                   (help-xref-button 1 #'Info-goto-node (list (match-data 1)))))
 939               ;; An obvious case of a key substitution:
 940               (save-excursion
 941                 (while (re-search-forward
 942                         "\\<M-x\\s-+\\(\\sw\\(\\sw\\|\\s_\\)+\\)" nil t)
 943                   (let ((sym (intern-soft (match-string 1))))
 944                     (if (fboundp sym)
 945                         (help-xref-button 1 #'describe-function sym)))))
 946               ;; Look for commands in whole keymap substitutions:
 947               (save-excursion
 948                 ;; Find a header and the column at which the command
 949                 ;; name will be found.
 950                 (while (re-search-forward "^key +binding\n\\(-+ +\\)-+\n\n"
 951                                           nil t)
 952                   (let ((col (- (match-end 1) (match-beginning 1))))
 953                     (while
 954                         ;; Ignore single blank lines in table, but not
 955                         ;; double ones, which should terminate it.
 956                         (and (looking-at "^\n?[^\n]")
 957                              (progn
 958                                (if (and (> (move-to-column col) 0)
 959                                         (looking-at "\\(\\sw\\|\\s_\\)+$"))
 960                                    ;;
 961                                    (let ((sym (intern-soft (match-string 0))))
 962                                      (if (fboundp sym)
 963                                          (help-xref-button
 964                                           0 #'describe-function sym))))
 965                                t)
 966                              (zerop (forward-line))
 967                              (move-to-column 0)))))))
 968           (set-syntax-table stab))
 969         ;; Make a back-reference in this buffer if appropriate.
 970         (when help-xref-stack
 971           (goto-char (point-max))
 972           (save-excursion
 973             (insert "\n\n" help-back-label))
 974           ;; Just to provide the match data:
 975           (looking-at (concat "\n\n\\(" (regexp-quote help-back-label) "\\)"))
 976           (help-xref-button 1 #'help-xref-go-back (current-buffer))))
 977       ;; View mode steals RET from us.
 978       (set (make-local-variable 'minor-mode-overriding-map-alist)
 979            (list (cons 'view-mode
 980                        (let ((map (make-sparse-keymap)))
 981                          (set-keymap-parent map view-mode-map)
 982                          (define-key map "\r" 'help-follow)
 983                          map))))
 984       (set-buffer-modified-p old-modified))))
 985
 986 (defun help-xref-button (match-number function data)
 987   "Make a hyperlink for cross-reference text previously matched.
 988
 989 MATCH-NUMBER is the subexpression of interest in the last matched
 990 regexp.  FUNCTION is a function to invoke when the button is
 991 activated, applied to DATA.  DATA may be a single value or a list.
 992 See `help-make-xrefs'."
 993   (add-text-properties (match-beginning match-number)
 994                      (match-end match-number)
 995                        (list 'mouse-face 'highlight
 996                      'help-xref (cons function
 997                                       (if (listp data)
 998                                           data
 999                                         (list data)))))
1000   (if help-highlight-p
1001       (put-text-property (match-beginning match-number)
1002                          (match-end match-number)
1003                          'face help-highlight-face)))
1004
1005 \f
1006 ;; Additional functions for (re-)creating types of help buffers.
1007 (defun help-xref-interned (symbol)
1008   "Follow a hyperlink which appeared to be an arbitrary interned SYMBOL.
1009
1010 Both variable and function documentation are extracted into a single
1011 help buffer."
1012   (let ((fdoc (describe-function symbol)))
1013     (describe-variable symbol)
1014     ;; We now have a help buffer on the variable.  Insert the function
1015     ;; text after it.
1016     (goto-char (point-max))
1017     (insert "\n\n" fdoc))
1018   (goto-char (point-min))
1019   (help-setup-xref (cons #'help-xref-interned symbol) nil))
1020
1021 (defun help-xref-mode (buffer)
1022   "Do a `describe-mode' for the specified BUFFER."
1023   (save-excursion
1024     (set-buffer buffer)
1025     (describe-mode)))
1026 \f
1027 ;;; Navigation/hyperlinking with xrefs
1028
1029 (defun help-follow-mouse (click)
1030   "Follow the cross-reference that you click on."
1031   (interactive "e")
1032   (save-excursion
1033     (let* ((start (event-start click))
1034            (window (car start))
1035            (pos (car (cdr start))))
1036       (set-buffer (window-buffer window))
1037       (help-follow pos))))
1038
1039 (defun help-xref-go-back (buffer)
1040   "Go back to the previous help buffer text using info on `help-xref-stack'."
1041   (interactive)
1042   (let (item method args)
1043     (with-current-buffer buffer
1044       (when help-xref-stack
1045         (setq help-xref-stack (cdr help-xref-stack)) ; due to help-follow
1046         (setq item (car help-xref-stack)
1047               method (car item)
1048               args (cdr item))
1049         (setq help-xref-stack (cdr help-xref-stack))))
1050     (if (listp args)
1051         (apply method args)
1052       (funcall method args))))
1053
1054 (defun help-go-back ()
1055   (interactive)
1056   (help-follow (1- (point-max))))
1057
1058 (defun help-follow (&optional pos)
1059   "Follow cross-reference at POS, defaulting to point.
1060
1061 For the cross-reference format, see `help-make-xrefs'."
1062   (interactive "d")
1063   (let* ((help-data (get-text-property pos 'help-xref))
1064          (method (car help-data))
1065          (args (cdr help-data)))
1066     (setq help-xref-stack (cons help-xref-stack-item help-xref-stack))
1067     (setq help-xref-stack-item nil)
1068     (when help-data
1069       ;; There is a reference at point.  Follow it.
1070       (apply method args))))
1071
1072 ;; For tabbing through buffer.
1073 (defun help-next-ref ()
1074   "Find the next help cross-reference in the buffer."
1075   (interactive)
1076   (let (pos)
1077     (while (not pos)
1078       (if (get-text-property (point) 'help-xref) ; move off reference
1079            (goto-char (or (next-single-property-change (point) 'help-xref)
1080                           (point))))
1081       (cond ((setq pos (next-single-property-change (point) 'help-xref))
1082              (if pos (goto-char pos)))
1083             ((bobp)
1084              (message "No cross references in the buffer.")
1085              (setq pos t))
1086             (t                          ; be circular
1087              (goto-char (point-min)))))))
1088
1089 (defun help-previous-ref ()
1090   "Find the previous help cross-reference in the buffer."
1091   (interactive)
1092   (let (pos)
1093     (while (not pos)
1094       (if (get-text-property (point) 'help-xref) ; move off reference
1095           (goto-char (or (previous-single-property-change (point) 'help-xref)
1096                          (point))))
1097       (cond ((setq pos (previous-single-property-change (point) 'help-xref))
1098              (if pos (goto-char pos)))
1099             ((bobp)
1100              (message "No cross references in the buffer.")
1101              (setq pos t))
1102             (t                          ; be circular
1103              (goto-char (point-max)))))))
1104
1105 ;;; help.el ends here