help.el 47.6 KB
Newer Older
Eric S. Raymond's avatar
Eric S. Raymond committed
1 2
;;; help.el --- help commands for Emacs

3
;; Copyright (C) 1985, 1986, 1993, 1994, 1998, 1999 Free Software Foundation, Inc.
Eric S. Raymond's avatar
Eric S. Raymond committed
4

Eric S. Raymond's avatar
Eric S. Raymond committed
5
;; Maintainer: FSF
Eric S. Raymond's avatar
Eric S. Raymond committed
6
;; Keywords: help, internal
Eric S. Raymond's avatar
Eric S. Raymond committed
7

Richard M. Stallman's avatar
Richard M. Stallman committed
8 9 10 11
;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
Eric S. Raymond's avatar
Eric S. Raymond committed
12
;; the Free Software Foundation; either version 2, or (at your option)
Richard M. Stallman's avatar
Richard M. Stallman committed
13 14 15 16 17 18 19 20
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
Erik Naggum's avatar
Erik Naggum committed
21 22 23
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.
Richard M. Stallman's avatar
Richard M. Stallman committed
24

25 26
;;; Commentary:

27
;; This code implements GNU Emacs' on-line help system, the one invoked by
28
;; `M-x help-for-help'.
29

Eric S. Raymond's avatar
Eric S. Raymond committed
30 31
;;; Code:

32 33
;; Get the macro make-help-screen when this is compiled,
;; or run interpreted, but not when the compiled code is loaded.
34
(eval-when-compile (require 'help-macro))
35

Richard M. Stallman's avatar
Richard M. Stallman committed
36 37 38
(defvar help-map (make-sparse-keymap)
  "Keymap for characters following the Help key.")

Karl Heuer's avatar
Karl Heuer committed
39 40 41
(defvar help-mode-map (make-sparse-keymap)
  "Keymap for help mode.")

Eric S. Raymond's avatar
Eric S. Raymond committed
42
(define-key global-map (char-to-string help-char) 'help-command)
43 44
(define-key global-map [help] 'help-command)
(define-key global-map [f1] 'help-command)
Richard M. Stallman's avatar
Richard M. Stallman committed
45 46
(fset 'help-command help-map)

Eric S. Raymond's avatar
Eric S. Raymond committed
47
(define-key help-map (char-to-string help-char) 'help-for-help)
48 49
(define-key help-map [help] 'help-for-help)
(define-key help-map [f1] 'help-for-help)
Richard M. Stallman's avatar
Richard M. Stallman committed
50 51 52 53 54
(define-key help-map "?" 'help-for-help)

(define-key help-map "\C-c" 'describe-copying)
(define-key help-map "\C-d" 'describe-distribution)
(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)
Richard M. Stallman's avatar
Richard M. Stallman committed
57 58 59 60 61 62 63 64 65

(define-key help-map "b" 'describe-bindings)

(define-key help-map "c" 'describe-key-briefly)
(define-key help-map "k" 'describe-key)

(define-key help-map "d" 'describe-function)
(define-key help-map "f" 'describe-function)

66 67
(define-key help-map "F" 'view-emacs-FAQ)

Richard M. Stallman's avatar
Richard M. Stallman committed
68
(define-key help-map "i" 'info)
69
(define-key help-map "4i" 'info-other-window)
Jim Blandy's avatar
Jim Blandy committed
70 71
(define-key help-map "\C-f" 'Info-goto-emacs-command-node)
(define-key help-map "\C-k" 'Info-goto-emacs-key-command-node)
72
(define-key help-map "\C-i" 'info-lookup-symbol)
Richard M. Stallman's avatar
Richard M. Stallman committed
73 74 75 76 77 78 79 80

(define-key help-map "l" 'view-lossage)

(define-key help-map "m" 'describe-mode)

(define-key help-map "\C-n" 'view-emacs-news)
(define-key help-map "n" 'view-emacs-news)

81
(define-key help-map "p" 'finder-by-keyword)
82 83
(autoload 'finder-by-keyword "finder"
  "Find packages matching a given keyword." t)
84

Richard M. Stallman's avatar
Richard M. Stallman committed
85 86 87 88 89 90 91 92
(define-key help-map "s" 'describe-syntax)

(define-key help-map "t" 'help-with-tutorial)

(define-key help-map "w" 'where-is)

(define-key help-map "v" 'describe-variable)

Richard M. Stallman's avatar
Richard M. Stallman committed
93 94
(define-key help-map "q" 'help-quit)

95 96 97 98 99
(define-key help-mode-map [mouse-2] 'help-follow-mouse)
(define-key help-mode-map "\C-c\C-b" 'help-go-back)
(define-key help-mode-map "\C-c\C-c" 'help-follow)
(define-key help-mode-map "\t" 'help-next-ref)
(define-key help-mode-map [backtab] 'help-previous-ref)
100
(define-key help-mode-map [(shift tab)] 'help-previous-ref)
101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125
;; Documentation only, since we use minor-mode-overriding-map-alist.
(define-key help-mode-map "\r" 'help-follow)

;; Font-locking is incompatible with the new xref stuff.
;(defvar help-font-lock-keywords
;  (eval-when-compile
;    (let ((name-char "[-+a-zA-Z0-9_*]") (sym-char "[-+a-zA-Z0-9_:*]"))
;      (list
;       ;;
;       ;; The symbol itself.
;       (list (concat "\\`\\(" name-char "+\\)\\(\\(:\\)\\|\\('\\)\\)")
;	     '(1 (if (match-beginning 3)
;		     font-lock-function-name-face
;		   font-lock-variable-name-face)))
;       ;;
;       ;; Words inside `' which tend to be symbol names.
;       (list (concat "`\\(" sym-char sym-char "+\\)'")
;	     1 'font-lock-constant-face t)
;       ;;
;       ;; CLisp `:' keywords as references.
;       (list (concat "\\<:" sym-char "+\\>") 0 'font-lock-builtin-face t))))
;  "Default expressions to highlight in Help mode.")

(defvar help-xref-stack nil
  "A stack of ways by which to return to help buffers after following xrefs.
126 127 128
Used by `help-follow' and `help-xref-go-back'.
An element looks like (POSITION FUNCTION ARGS...).
To use the element, do (apply FUNCTION ARGS) then (goto-char POSITION).")
129 130 131
(put 'help-xref-stack 'permanent-local t)

(defvar help-xref-stack-item nil
132 133
  "An item for `help-follow' in this buffer to push onto `help-xref-stack'.
The format is (FUNCTION ARGS...).")
134 135 136
(put 'help-xref-stack-item 'permanent-local t)

(setq-default help-xref-stack nil help-xref-stack-item nil)
Simon Marshall's avatar
Simon Marshall committed
137

Karl Heuer's avatar
Karl Heuer committed
138
(defun help-mode ()
139
  "Major mode for viewing help text and navigating references in it.
Karl Heuer's avatar
Karl Heuer committed
140 141 142 143 144 145 146 147
Entry to this mode runs the normal hook `help-mode-hook'.
Commands:
\\{help-mode-map}"
  (interactive)
  (kill-all-local-variables)
  (use-local-map help-mode-map)
  (setq mode-name "Help")
  (setq major-mode 'help-mode)
Simon Marshall's avatar
Simon Marshall committed
148
  (make-local-variable 'font-lock-defaults)
149
  (setq font-lock-defaults nil)         ; font-lock would defeat xref
150
  (view-mode)
151 152
  (make-local-variable 'view-no-disable-on-exit)
  (setq view-no-disable-on-exit t)
153 154
  ;; `help-make-xrefs' would be run here if not invoked from
  ;; `help-mode-maybe'.
Karl Heuer's avatar
Karl Heuer committed
155 156
  (run-hooks 'help-mode-hook))

157 158 159 160
(defun help-mode-setup ()
  (help-mode)
  (setq buffer-read-only nil))

161
(add-hook 'temp-buffer-setup-hook 'help-mode-setup)
162 163

(defun help-mode-finish ()
164 165 166 167 168
  (when (eq major-mode 'help-mode) 
    ;; View mode's read-only status of existing *Help* buffer is lost
    ;; by with-output-to-temp-buffer.
    (toggle-read-only 1)
    (help-make-xrefs (current-buffer)))
169 170
  (setq view-return-to-alist
	(list (cons (selected-window) help-return-method))))
171

172
(add-hook 'temp-buffer-show-hook 'help-mode-finish)
173

Richard M. Stallman's avatar
Richard M. Stallman committed
174
(defun help-quit ()
Richard M. Stallman's avatar
Richard M. Stallman committed
175
  "Just exit from the Help command's command loop."
Richard M. Stallman's avatar
Richard M. Stallman committed
176 177 178
  (interactive)
  nil)

179 180
(defun help-with-tutorial (&optional arg)
  "Select the Emacs learn-by-doing tutorial.
181
If there is a tutorial version written in the language
182
of the selected language environment, that version is used.
183
If there's no tutorial in that language, `TUTORIAL' is selected.
184
With arg, you are asked to choose which language."
185
  (interactive "P")
186 187 188 189
  (let ((lang (if arg
		  (read-language-name 'tutorial "Language: " "English")
		(if (get-language-info current-language-environment 'tutorial)
		    current-language-environment
190 191
		  "English")))
	file filename)
192
    (setq filename (get-language-info lang 'tutorial))
193
    (setq file (expand-file-name (concat "~/" filename)))
Richard M. Stallman's avatar
Richard M. Stallman committed
194 195 196 197 198 199
    (delete-other-windows)
    (if (get-file-buffer file)
	(switch-to-buffer (get-file-buffer file))
      (switch-to-buffer (create-file-buffer file))
      (setq buffer-file-name file)
      (setq default-directory (expand-file-name "~/"))
Jim Blandy's avatar
Jim Blandy committed
200
      (setq buffer-auto-save-file-name nil)
201
      (insert-file-contents (expand-file-name filename data-directory))
Richard M. Stallman's avatar
Richard M. Stallman committed
202 203 204 205
      (goto-char (point-min))
      (search-forward "\n<<")
      (beginning-of-line)
      (delete-region (point) (progn (end-of-line) (point)))
206
      (let ((n (- (window-height (selected-window))
Richard M. Stallman's avatar
Richard M. Stallman committed
207
		  (count-lines (point-min) (point))
208
		  6)))
209
	(if (< n 12)
210 211 212 213 214 215
	    (newline n)
	  ;; Some people get confused by the large gap.
	  (newline (/ n 2))
	  (insert "[Middle of page left blank for didactic purposes.  "
		  "Text continues below]")
	  (newline (- n (/ n 2)))))
Richard M. Stallman's avatar
Richard M. Stallman committed
216 217 218
      (goto-char (point-min))
      (set-buffer-modified-p nil))))

219 220 221 222 223 224 225 226 227 228 229 230 231
(defun mode-line-key-binding (key)
  "Value is the binding of KEY in the mode line or nil if none."
  (let (string-info defn)
    (when (and (eq 'mode-line (aref key 0))
	       (consp (setq string-info (nth 4 (event-start (aref key 1))))))
    (let* ((string (car string-info))
	   (pos (cdr string-info))
	   (local-map (and (> pos 0)
			   (< pos (length string))
			   (get-text-property pos 'local-map string))))
      (setq defn (and local-map (lookup-key local-map key)))))
    defn))

232 233 234 235
(defun describe-key-briefly (key &optional insert)
  "Print the name of the function KEY invokes.  KEY is a string.
If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
  (interactive "kDescribe key briefly: \nP")
236 237
  (save-excursion
    (let ((modifiers (event-modifiers (aref key 0)))
238
	  (standard-output (if insert (current-buffer) t))
239 240 241 242 243 244 245 246 247 248 249 250 251
	  window position)
      ;; For a mouse button event, go to the button it applies to
      ;; to get the right key bindings.  And go to the right place
      ;; in case the keymap depends on where you clicked.
      (if (or (memq 'click modifiers) (memq 'down modifiers)
	      (memq 'drag modifiers))
	  (setq window (posn-window (event-start (aref key 0)))
		position (posn-point (event-start (aref key 0)))))
      (if (windowp window)
	  (progn
	    (set-buffer (window-buffer window))
	    (goto-char position)))
      ;; Ok, now look up the key and name the command.
252 253
      (let ((defn (or (mode-line-key-binding key)
		      (key-binding key)))
254
	    (key-desc (key-description key)))
255
	(if (or (null defn) (integerp defn))
256 257
	    (princ (format "%s is undefined" key-desc))
	  (princ (format (if insert
258
			     "`%s' (`%s')"
259 260 261 262 263
			   (if (windowp window)
			       "%s at that spot runs the command %s"
			     "%s runs the command %s"))
			 key-desc
			 (if (symbolp defn) defn (prin1-to-string defn)))))))))
Richard M. Stallman's avatar
Richard M. Stallman committed
264

265 266 267 268 269 270 271
(defvar help-return-method nil
  "What to do to \"exit\" the help buffer.
This is a list
 (WINDOW . t)              delete the selected window, go to WINDOW.
 (WINDOW . quit-window)    do quit-window, then select WINDOW.
 (WINDOW BUF START POINT)  display BUF at START, POINT, then select WINDOW.")

Richard M. Stallman's avatar
Richard M. Stallman committed
272 273 274 275 276
(defun print-help-return-message (&optional function)
  "Display or return message saying how to restore windows after help command.
Computes a message and applies the optional argument FUNCTION to it.
If FUNCTION is nil, applies `message' to it, thus printing it."
  (and (not (get-buffer-window standard-output))
277
       (let ((first-message
278
	      (cond ((special-display-p (buffer-name standard-output))
279
		     (setq help-return-method (cons (selected-window) t))
280 281 282 283 284 285 286 287
		     ;; If the help output buffer is a special display buffer,
		     ;; don't say anything about how to get rid of it.
		     ;; First of all, the user will do that with the window
		     ;; manager, not with Emacs.
		     ;; Secondly, the buffer has not been displayed yet,
		     ;; so we don't know whether its frame will be selected.
		     nil)
		    ((not (one-window-p t))
288 289
		     (setq help-return-method
			   (cons (selected-window) 'quit-window))
290 291
		     "Type \\[switch-to-buffer-other-window] RET to restore the other window.")
		    (pop-up-windows
292
		     (setq help-return-method (cons (selected-window) t))
293 294
		     "Type \\[delete-other-windows] to remove help window.")
		    (t
295 296 297
		     (setq help-return-method
			   (list (selected-window) (window-buffer)
				 (window-start) (window-point)))
298 299 300 301 302 303 304
		     "Type \\[switch-to-buffer] RET to remove help window."))))
	 (funcall (or function 'message)
		  (concat
		   (if first-message
		       (substitute-command-keys first-message)
		     "")
		   (if first-message "  " "")
305 306
		   ;; If the help buffer will go in a separate frame,
		   ;; it's no use mentioning a command to scroll, so don't.
307
		   (if (special-display-p (buffer-name standard-output))
308
		       nil
309
		     (if (same-window-p (buffer-name standard-output))
310 311 312 313
			 ;; Say how to scroll this window.
			 (substitute-command-keys
			  "\\[scroll-up] to scroll the help.")
		       ;; Say how to scroll some other window.
314
		       (substitute-command-keys
315
			"\\[scroll-other-window] to scroll the help."))))))))
Richard M. Stallman's avatar
Richard M. Stallman committed
316 317 318 319

(defun describe-key (key)
  "Display documentation of the function invoked by KEY.  KEY is a string."
  (interactive "kDescribe key: ")
320 321 322 323 324 325 326 327 328 329 330 331 332 333
  (save-excursion
    (let ((modifiers (event-modifiers (aref key 0)))
	  window position)
      ;; For a mouse button event, go to the button it applies to
      ;; to get the right key bindings.  And go to the right place
      ;; in case the keymap depends on where you clicked.
      (if (or (memq 'click modifiers) (memq 'down modifiers)
	      (memq 'drag modifiers))
	  (setq window (posn-window (event-start (aref key 0)))
		position (posn-point (event-start (aref key 0)))))
      (if (windowp window)
	  (progn
	    (set-buffer (window-buffer window))
	    (goto-char position)))
334
      (let ((defn (or (mode-line-key-binding key) (key-binding key))))
335 336 337 338 339 340 341 342
	(if (or (null defn) (integerp defn))
	    (message "%s is undefined" (key-description key))
	  (with-output-to-temp-buffer "*Help*"
	    (princ (key-description key))
	    (if (windowp window)
		(princ " at that spot"))
	    (princ " runs the command ")
	    (prin1 defn)
343
	    (princ "\n   which is ")
344
	    (describe-function-1 defn nil (interactive-p))
345
	    (print-help-return-message)))))))
Richard M. Stallman's avatar
Richard M. Stallman committed
346

347 348
(defun describe-mode ()
  "Display documentation of current major mode and minor modes.
349 350 351
The major mode description comes first, followed by the minor modes,
each on a separate page.

Richard M. Stallman's avatar
Richard M. Stallman committed
352
For this to work correctly for a minor mode, the mode's indicator variable
353
\(listed in `minor-mode-alist') must also be a function whose documentation
Richard M. Stallman's avatar
Richard M. Stallman committed
354
describes the minor mode."
355
  (interactive)
Richard M. Stallman's avatar
Richard M. Stallman committed
356
  (with-output-to-temp-buffer "*Help*"
357 358 359 360 361 362 363 364
    (when minor-mode-alist
      (princ "The major mode is described first.
For minor modes, see following pages.\n\n"))
    (princ mode-name)
    (princ " mode:\n")
    (princ (documentation major-mode))
    (help-setup-xref (list #'help-xref-mode (current-buffer)) (interactive-p))
    (let ((minor-modes minor-mode-alist))
365 366
      (while minor-modes
	(let* ((minor-mode (car (car minor-modes)))
367
	       (indicator (car (cdr (car minor-modes)))))
368 369 370
	  ;; Document a minor mode if it is listed in minor-mode-alist,
	  ;; bound locally in this buffer, non-nil, and has a function
	  ;; definition.
371
	  (if (and (symbol-value minor-mode)
372 373 374 375 376 377 378
		   (fboundp minor-mode))
	      (let ((pretty-minor-mode minor-mode))
		(if (string-match "-mode$" (symbol-name minor-mode))
		    (setq pretty-minor-mode
			  (capitalize
			   (substring (symbol-name minor-mode)
				      0 (match-beginning 0)))))
379 380 381
		(while (and indicator (symbolp indicator)
			    (boundp indicator)
			    (not (eq indicator (symbol-value indicator))))
382
		  (setq indicator (symbol-value indicator)))
383
		(princ "\n\f\n")
384 385 386 387 388
		(princ (format "%s minor mode (%s):\n"
			       pretty-minor-mode
			       (if indicator
				   (format "indicator%s" indicator)
				 "no indicator")))
389
		(princ (documentation minor-mode)))))
390
	(setq minor-modes (cdr minor-modes))))
Richard M. Stallman's avatar
Richard M. Stallman committed
391 392 393 394 395 396 397 398 399
    (print-help-return-message)))

;; So keyboard macro definitions are documented correctly
(fset 'defining-kbd-macro (symbol-function 'start-kbd-macro))

(defun describe-distribution ()
  "Display info on how to obtain the latest version of GNU Emacs."
  (interactive)
  (find-file-read-only
Jim Blandy's avatar
Jim Blandy committed
400
   (expand-file-name "DISTRIB" data-directory)))
Richard M. Stallman's avatar
Richard M. Stallman committed
401 402 403 404 405

(defun describe-copying ()
  "Display info on how you may redistribute copies of GNU Emacs."
  (interactive)
  (find-file-read-only
Jim Blandy's avatar
Jim Blandy committed
406
   (expand-file-name "COPYING" data-directory))
Richard M. Stallman's avatar
Richard M. Stallman committed
407 408
  (goto-char (point-min)))

409 410 411 412 413 414 415
(defun describe-project ()
  "Display info on the GNU project."
  (interactive)
  (find-file-read-only
   (expand-file-name "GNU" data-directory))
  (goto-char (point-min)))

Richard M. Stallman's avatar
Richard M. Stallman committed
416 417 418 419 420 421 422 423
(defun describe-no-warranty ()
  "Display info on all the kinds of warranty Emacs does NOT have."
  (interactive)
  (describe-copying)
  (let (case-fold-search)
    (search-forward "NO WARRANTY")
    (recenter 0)))

424
(defun describe-prefix-bindings ()
425 426 427
  "Describe the bindings of the prefix used to reach this command.
The prefix described consists of all but the last event
of the key sequence that ran this command."
428
  (interactive)
429 430 431 432 433 434 435 436 437 438
  (let* ((key (this-command-keys)))
    (describe-bindings
     (if (stringp key)
	 (substring key 0 (1- (length key)))
       (let ((prefix (make-vector (1- (length key)) nil))
	     (i 0))
	 (while (< i (length prefix))
	   (aset prefix i (aref key i))
	   (setq i (1+ i)))
	 prefix)))))
439 440
;; Make C-h after a prefix, when not specifically bound, 
;; run describe-prefix-bindings.
441 442
(setq prefix-help-command 'describe-prefix-bindings)

443 444 445 446 447 448 449 450
(defun view-emacs-news (&optional arg)
  "Display info on recent changes to Emacs.
With numeric argument display information on correspondingly older changes."
  (interactive "P")
  (let* ((arg (if arg (prefix-numeric-value arg) 0)))
    (find-file-read-only
     (expand-file-name (concat (make-string arg ?O) "NEWS")
		       data-directory))))
Richard M. Stallman's avatar
Richard M. Stallman committed
451

452 453 454 455 456
(defun view-emacs-FAQ ()
  "Display the Emacs Frequently Asked Questions (FAQ) file."
  (interactive)
  (find-file-read-only (expand-file-name "FAQ" data-directory)))

Richard M. Stallman's avatar
Richard M. Stallman committed
457 458 459 460
(defun view-lossage ()
  "Display last 100 input keystrokes."
  (interactive)
  (with-output-to-temp-buffer "*Help*"
461 462 463 464 465 466 467 468
    (princ (mapconcat (function (lambda (key)
				  (if (or (integerp key)
					  (symbolp key)
					  (listp key))
				      (single-key-description key)
				    (prin1-to-string key nil))))
		      (recent-keys)
		      " "))
Richard M. Stallman's avatar
Richard M. Stallman committed
469 470 471 472 473
    (save-excursion
      (set-buffer standard-output)
      (goto-char (point-min))
      (while (progn (move-to-column 50) (not (eobp)))
	(search-forward " " nil t)
474 475 476
	(insert "\n"))
      (setq help-xref-stack nil
	    help-xref-stack-item nil))
Richard M. Stallman's avatar
Richard M. Stallman committed
477 478
    (print-help-return-message)))

Richard M. Stallman's avatar
Richard M. Stallman committed
479
(defalias 'help 'help-for-help)
480
(make-help-screen help-for-help
481
  "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:"
482
  "You have typed %THIS-KEY%, the help character.  Type a Help option:
483
\(Use SPC or DEL to scroll through this text.  Type \\<help-map>\\[help-quit] to exit the Help command.)
Richard M. Stallman's avatar
Richard M. Stallman committed
484

485 486 487
a  command-apropos.  Give a substring, and see a list of commands
	(functions interactively callable) that contain
	that substring.  See also the  apropos  command.
488 489
b  describe-bindings.  Display table of all key bindings.
c  describe-key-briefly.  Type a command key sequence;
490
	it prints the function name that sequence runs.
491 492 493
C  describe-coding-system.  This describes either a specific coding system
        (if you type its name) or the coding systems currently in use
	(if you type just RET).
494
f  describe-function.  Type a function name and get documentation of it.
495 496
C-f Info-goto-emacs-command-node.  Type a function name;
	it takes you to the Info node for that command.
497
i  info. The  info  documentation reader.
498 499
I  describe-input-method.  Describe a specific input method (if you type
	its name) or the current input method (if you type just RET).
500 501
C-i  info-lookup-symbol.  Display the definition of a specific symbol
        as found in the manual for the language this buffer is written in.
502
k  describe-key.  Type a command key sequence;
503 504 505
	it displays the full documentation.
C-k Info-goto-emacs-key-command-node.  Type a command key sequence;
	it takes you to the Info node for the command bound to that key.
506
l  view-lossage.  Show last 100 characters you typed.
507 508 509
L  describe-language-environment.  This describes either the a
	specific language environment (if you type its name)
	or the current language environment (if you type just RET).
510 511
m  describe-mode.  Print documentation of current minor modes,
	and the current major mode, including their special commands.
512
n  view-emacs-news.  Display news of recent Emacs changes.
513 514 515 516
p  finder-by-keyword. Find packages matching a given topic keyword.
s  describe-syntax.  Display contents of syntax table, plus explanations
t  help-with-tutorial.  Select the Emacs learn-by-doing tutorial.
v  describe-variable.  Type name of a variable;
517
	it displays the variable's documentation and value.
518
w  where-is.  Type command name; it prints which keystrokes
519
	invoke that command.
520 521 522 523 524 525 526 527

F  Display the frequently asked questions file.
h  Display the HELLO file which illustrates various scripts.
C-c Display Emacs copying permission (General Public License).
C-d Display Emacs ordering information.
C-n Display news of recent Emacs changes.
C-p Display information about the GNU project.
C-w Display information on absence of warranty for GNU Emacs."
528
  help-map)
Richard M. Stallman's avatar
Richard M. Stallman committed
529 530

(defun function-called-at-point ()
531 532
  "Return a function around point or else called by the list containing point.
If that doesn't give a function, return nil."
533 534 535 536
  (let ((stab (syntax-table)))
    (set-syntax-table emacs-lisp-mode-syntax-table)
    (unwind-protect
	(or (condition-case ()
537 538 539 540 541 542 543 544 545 546
		(save-excursion
		  (or (not (zerop (skip-syntax-backward "_w")))
		      (eq (char-syntax (following-char)) ?w)
		      (eq (char-syntax (following-char)) ?_)
		      (forward-sexp -1))
		  (skip-chars-forward "'")
		  (let ((obj (read (current-buffer))))
		    (and (symbolp obj) (fboundp obj) obj)))
	      (error nil))
	    (condition-case ()
547 548 549 550 551 552 553 554 555 556 557 558 559 560 561
		(save-excursion
		  (save-restriction
		    (narrow-to-region (max (point-min) (- (point) 1000)) (point-max))
		    ;; Move up to surrounding paren, then after the open.
		    (backward-up-list 1)
		    (forward-char 1)
		    ;; If there is space here, this is probably something
		    ;; other than a real Lisp function call, so ignore it.
		    (if (looking-at "[ \t]")
			(error "Probably not a Lisp function call"))
		    (let (obj)
		      (setq obj (read (current-buffer)))
		      (and (symbolp obj) (fboundp obj) obj))))
	      (error nil)))
      (set-syntax-table stab))))
Richard M. Stallman's avatar
Richard M. Stallman committed
562

563 564 565 566 567 568
(defvar symbol-file-load-history-loaded nil
  "Non-nil means we have loaded the file `fns-VERSION.el' in `exec-directory'.
That file records the part of `load-history' for preloaded files,
which is cleared out before dumping to make Emacs smaller.")

(defun symbol-file (function)
569
  "Return the input source from which FUNCTION was loaded.
570 571 572 573 574 575 576 577 578 579 580 581 582 583
The value is normally a string that was passed to `load':
either an absolute file name, or a library name
\(with no directory name and no `.el' or `.elc' at the end).
It can also be nil, if the definition is not associated with any file."
  (unless symbol-file-load-history-loaded
    (load (expand-file-name
	   ;; fns-XX.YY.ZZ.el does not work on DOS filesystem.
	   (if (eq system-type 'ms-dos)
	       "fns.el"
	     (format "fns-%s.el" emacs-version))
	   exec-directory)
	  ;; The file name fns-%s.el already has a .el extension.
	  nil nil t)
    (setq symbol-file-load-history-loaded t))
584 585 586 587 588 589 590 591
  (let ((files load-history)
	file functions)
    (while files
      (if (memq function (cdr (car files)))
	  (setq file (car (car files)) files nil))
      (setq files (cdr files)))
    file))

Richard M. Stallman's avatar
Richard M. Stallman committed
592 593 594 595 596 597 598 599 600
(defun describe-function (function)
  "Display the full documentation of FUNCTION (a symbol)."
  (interactive
   (let ((fn (function-called-at-point))
	 (enable-recursive-minibuffers t)	     
	 val)
     (setq val (completing-read (if fn
				    (format "Describe function (default %s): " fn)
				  "Describe function: ")
601
				obarray 'fboundp t nil nil (symbol-name fn)))
Richard M. Stallman's avatar
Richard M. Stallman committed
602 603
     (list (if (equal val "")
	       fn (intern val)))))
604 605 606
  (if function
      (with-output-to-temp-buffer "*Help*"
	(prin1 function)
607 608 609
	;; Use " is " instead of a colon so that
	;; it is easier to get out the function name using forward-sexp.
	(princ " is ")
610
	(describe-function-1 function nil (interactive-p))
611 612 613 614 615 616 617
	(print-help-return-message)
	(save-excursion
	  (set-buffer standard-output)
	  ;; Return the text we displayed.
	  (buffer-string)))
    (message "You didn't specify a function")))

618
(defun describe-function-1 (function parens interactive-p)
619 620 621
  (let* ((def (if (symbolp function)
		  (symbol-function function)
		function))
622 623 624 625 626 627 628 629 630 631 632
	 file-name string need-close
	 (beg (if (commandp def) "an interactive " "a ")))
    (setq string
	  (cond ((or (stringp def)
		     (vectorp def))
		 "a keyboard macro")
		((subrp def)
		 (concat beg "built-in function"))
		((byte-code-function-p def)
		 (concat beg "compiled Lisp function"))
		((symbolp def)
633 634
		 (while (symbolp (symbol-function def))
		   (setq def (symbol-function def)))
635
		 (format "an alias for `%s'" def))
636 637 638 639 640 641 642 643
		((eq (car-safe def) 'lambda)
		 (concat beg "Lisp function"))
		((eq (car-safe def) 'macro)
		 "a Lisp macro")
		((eq (car-safe def) 'mocklisp)
		 "a mocklisp function")
		((eq (car-safe def) 'autoload)
		 (setq file-name (nth 1 def))
644
		 (format "%s autoloaded %s"
645
			 (if (commandp def) "an interactive" "an")
646 647
			 (if (eq (nth 4 def) 'keymap) "keymap"
			   (if (nth 4 def) "Lisp macro" "Lisp function"))
648
			 ))
649 650 651 652 653 654 655 656 657 658 659 660
                ;; perhaps use keymapp here instead
                ((eq (car-safe def) 'keymap)
                 (let ((is-full nil)
                       (elts (cdr-safe def)))
                   (while elts
                     (if (char-table-p (car-safe elts))
                         (setq is-full t
                               elts nil))
                     (setq elts (cdr-safe elts)))
                   (if is-full
                       "a full keymap"
                     "a sparse keymap")))
661 662 663 664 665
		(t "")))
    (when (and parens (not (equal string "")))
      (setq need-close t)
      (princ "("))
    (princ string)
666 667 668 669 670
    (with-current-buffer "*Help*"
      (save-excursion
	(save-match-data
	  (if (re-search-backward "alias for `\\([^`']+\\)'" nil t)
	      (help-xref-button 1 #'describe-function def)))))
671
    (or file-name
672
	(setq file-name (symbol-file function)))
673 674 675 676 677 678
    (if file-name
	(progn
	  (princ " in `")
	  ;; We used to add .el to the file name,
	  ;; but that's completely wrong when the user used load-file.
	  (princ file-name)
679 680 681 682 683
	  (princ "'")
	  ;; Make a hyperlink to the library.
	  (with-current-buffer "*Help*"
	    (save-excursion
	      (re-search-backward "`\\([^`']+\\)'" nil t)
684 685 686
	      (help-xref-button 1 #'(lambda (arg)
				      (let ((location
					     (find-function-noselect arg)))
687 688
					(pop-to-buffer (car location))
					(goto-char (cdr location))))
689
				function)))))
690 691 692
    (if need-close (princ ")"))
    (princ ".")
    (terpri)
693 694 695 696 697 698 699 700 701 702
    ;; Handle symbols aliased to other symbols.
    (setq def (indirect-function def))
    ;; If definition is a macro, find the function inside it.
    (if (eq (car-safe def) 'macro)
	(setq def (cdr def)))
    (let ((arglist (cond ((byte-code-function-p def)
			  (car (append def nil)))
			 ((eq (car-safe def) 'lambda)
			  (nth 1 def))
			 (t t))))
703 704
      (if (listp arglist)
	  (progn
705
	    (princ (cons (if (symbolp function) function "anonymous")
706 707 708 709 710 711 712 713 714 715
			 (mapcar (lambda (arg)
				   (if (memq arg '(&optional &rest))
				       arg
				     (intern (upcase (symbol-name arg)))))
				 arglist)))
	    (terpri))))
    (let ((doc (documentation function)))
      (if doc
	  (progn (terpri)
		 (princ doc)
716
		 (help-setup-xref (list #'describe-function function) interactive-p))
717 718
	(princ "not documented")))))

Richard M. Stallman's avatar
Richard M. Stallman committed
719
(defun variable-at-point ()
720 721
  "Return the bound variable symbol found around point.
Return 0 if there is no such symbol."
Richard M. Stallman's avatar
Richard M. Stallman committed
722
  (condition-case ()
723 724 725 726 727 728 729 730 731 732
      (let ((stab (syntax-table)))
	(unwind-protect
	    (save-excursion
	      (set-syntax-table emacs-lisp-mode-syntax-table)
	      (or (not (zerop (skip-syntax-backward "_w")))
		  (eq (char-syntax (following-char)) ?w)
		  (eq (char-syntax (following-char)) ?_)
		  (forward-sexp -1))
	      (skip-chars-forward "'")
	      (let ((obj (read (current-buffer))))
733 734
		(or (and (symbolp obj) (boundp obj) obj)
		    0)))
735
	  (set-syntax-table stab)))
736
    (error 0)))
Richard M. Stallman's avatar
Richard M. Stallman committed
737 738 739 740 741 742 743 744

(defun describe-variable (variable)
  "Display the full documentation of VARIABLE (a symbol).
Returns the documentation as a string, also."
  (interactive 
   (let ((v (variable-at-point))
	 (enable-recursive-minibuffers t)
	 val)
745
     (setq val (completing-read (if (symbolp v)
Richard M. Stallman's avatar
Richard M. Stallman committed
746 747
				    (format "Describe variable (default %s): " v)
				  "Describe variable: ")
748 749
				obarray 'boundp t nil nil
				(if (symbolp v) (symbol-name v))))
Richard M. Stallman's avatar
Richard M. Stallman committed
750 751
     (list (if (equal val "")
	       v (intern val)))))
752
  (if (symbolp variable)
753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790
      (let (valvoid)
	(with-output-to-temp-buffer "*Help*"
	  (prin1 variable)
	  (if (not (boundp variable))
	      (progn
		(princ " is void")
		(terpri)
		(setq valvoid t))
	    (princ "'s value is ")
	    (terpri)
	    (pp (symbol-value variable))
	    (terpri))
	  (if (local-variable-p variable)
	      (progn
		(princ (format "Local in buffer %s; " (buffer-name)))
		(if (not (default-boundp variable))
		    (princ "globally void")
		  (princ "global value is ")
		  (terpri)
		  (pp (default-value variable)))
		(terpri)))
	  (terpri)
	  (save-current-buffer
	    (set-buffer standard-output)
	    (if (> (count-lines (point-min) (point-max)) 10)
		(progn
		  (goto-char (point-min))
		  (if valvoid
		      (forward-line 1)
		    (forward-sexp 1)
		    (delete-region (point) (progn (end-of-line) (point)))
		    (insert "'s value is shown below.\n\n")
		    (save-excursion
		      (insert "\n\nValue:"))))))
	  (princ "Documentation:")
	  (terpri)
	  (let ((doc (documentation-property variable 'variable-documentation)))
	    (princ (or doc "not documented as a variable.")))
791
          (help-setup-xref (list #'describe-variable variable) (interactive-p))
792 793

	  ;; Make a link to customize if this variable can be customized.
794
	  ;; Note, it is not reliable to test only for a custom-type property
Richard M. Stallman's avatar
Richard M. Stallman committed
795 796
	  ;; because those are only present after the var's definition
	  ;; has been loaded.
797 798 799
	  (if (or (get variable 'custom-type) ; after defcustom
		  (get variable 'custom-loads) ; from loaddefs.el
		  (get variable 'standard-value)) ; from cus-start.el
800 801 802 803 804 805 806 807 808 809 810
	      (let ((customize-label "customize"))
		(terpri)
		(terpri)
		(princ (concat "You can " customize-label " this variable."))
		(with-current-buffer "*Help*"
		  (save-excursion
		    (re-search-backward 
		     (concat "\\(" customize-label "\\)") nil t)
		    (help-xref-button 1 #'(lambda (v)
					    (customize-variable v)) variable)
		    ))))
811 812 813
	  ;; Make a hyperlink to the library if appropriate.  (Don't
	  ;; change the format of the buffer's initial line in case
	  ;; anything expects the current format.)
814
	  (let ((file-name (symbol-file variable)))
815
	    (when file-name
816
	      (princ "\n\nDefined in `")
817
	      (princ file-name)
818
	      (princ "'.")
819 820
	      (with-current-buffer "*Help*"
		(save-excursion
821
		  (re-search-backward "`\\([^`']+\\)'" nil t)
822 823 824 825 826 827
		  (help-xref-button 1 (lambda (arg)
					(let ((location
					       (find-variable-noselect arg)))
					  (pop-to-buffer (car location))
					  (goto-char (cdr location))))
				    variable)))))
828

829 830 831 832 833
	  (print-help-return-message)
	  (save-excursion
	    (set-buffer standard-output)
	    ;; Return the text we displayed.
	    (buffer-string))))
834
    (message "You did not specify a variable")))
Richard M. Stallman's avatar
Richard M. Stallman committed
835

836
(defun describe-bindings (&optional prefix buffer)
837 838 839 840
  "Show a list of all defined keys, and their definitions.
We put that list in a buffer, and display the buffer.

The optional argument PREFIX, if non-nil, should be a key sequence;
841 842 843
then we display only bindings that start with that prefix.
The optional argument BUFFER specifies which buffer's bindings
to display (default, the current buffer)."
844
  (interactive "P")
845 846 847
  (or buffer (setq buffer (current-buffer)))
  (with-current-buffer buffer
    (describe-bindings-internal nil prefix))
848
  (with-current-buffer "*Help*"
849 850
    (help-setup-xref (list #'describe-bindings prefix buffer)
		     (interactive-p))))
851

852
(defun where-is (definition &optional insert)
853
  "Print message listing key sequences that invoke the command DEFINITION.
854 855
Argument is a command definition, usually a symbol with a function definition.
If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
856 857 858 859 860 861 862 863 864
  (interactive
   (let ((fn (function-called-at-point))
	 (enable-recursive-minibuffers t)	     
	 val)
     (setq val (completing-read (if fn
				    (format "Where is command (default %s): " fn)
				  "Where is command: ")
				obarray 'fboundp t))
     (list (if (equal val "")
865 866
	       fn (intern val))
	   current-prefix-arg)))
867
  (let* ((keys (where-is-internal definition overriding-local-map nil nil))
868 869 870 871 872 873 874 875 876
	 (keys1 (mapconcat 'key-description keys ", "))
	 (standard-output (if insert (current-buffer) t)))
    (if insert
	(if (> (length keys1) 0)
	    (princ (format "%s (%s)" keys1 definition))
	  (princ (format "M-x %s RET" definition)))
      (if (> (length keys1) 0)
	  (princ (format "%s is on %s" definition keys1))
	(princ (format "%s is not on any key" definition)))))
877 878
  nil)

879
(defun locate-library (library &optional nosuffix path interactive-call)
880
  "Show the precise file name of Emacs library LIBRARY.
Richard M. Stallman's avatar
Richard M. Stallman committed
881 882 883
This command searches the directories in `load-path' like `M-x load-library'
to find the file that `M-x load-library RET LIBRARY RET' would load.
Optional second arg NOSUFFIX non-nil means don't add suffixes `.elc' or `.el'
884 885 886
to the specified name LIBRARY.

If the optional third arg PATH is specified, that list of directories
887 888 889 890 891
is used instead of `load-path'.

When called from a program, the file name is normaly returned as a
string.  When run interactively, the argument INTERACTIVE-CALL is t,
and the file name is displayed in the echo area."
892 893 894
  (interactive (list (read-string "Locate library: ")
		     nil nil
		     t))
895
  (let (result)
896 897
    (catch 'answer
      (mapcar
898 899 900 901 902 903 904 905 906 907 908
       (lambda (dir)
	 (mapcar
	  (lambda (suf)
	    (let ((try (expand-file-name (concat library suf) dir)))
	      (and (file-readable-p try)
		   (null (file-directory-p try))
		   (progn
		     (setq result try)
		     (throw 'answer try)))))
	  (if nosuffix
	      '("")
909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924
	    '(".elc" ".el" "")
;;; load doesn't handle this yet.
;;;	    (let ((basic '(".elc" ".el" ""))
;;;		  (compressed '(".Z" ".gz" "")))
;;;	      ;; If autocompression mode is on,
;;;	      ;; consider all combinations of library suffixes
;;;	      ;; and compression suffixes.
;;;	      (if (rassq 'jka-compr-handler file-name-handler-alist)
;;;		  (apply 'nconc
;;;			 (mapcar (lambda (compelt)
;;;				   (mapcar (lambda (baselt)
;;;					     (concat baselt compelt))
;;;					   basic))
;;;				 compressed))
;;;		basic))
	    )))
925 926 927 928 929 930
       (or path load-path)))
    (and interactive-call
	 (if result
	     (message "Library is file %s" result)
	   (message "No library %s in search path" library)))
    result))
Eric S. Raymond's avatar
Eric S. Raymond committed
931

932 933 934 935 936 937 938 939 940 941 942

;;; Grokking cross-reference information in doc strings and
;;; hyperlinking it.

;; This may have some scope for extension and the same or something
;; similar should be done for widget doc strings, which currently use
;; another mechanism.

(defcustom help-highlight-p t
  "*If non-nil, `help-make-xrefs' highlight cross-references.
Under a window system it highlights them with face defined by
Dave Love's avatar
Dave Love committed
943
`help-highlight-face'."
944 945 946 947 948 949 950 951 952
 :group 'help
 :version "20.3"
 :type 'boolean)

(defcustom help-highlight-face 'underline
  "Face used by `help-make-xrefs' to highlight cross-references.
Must be previously-defined."
  :group 'help
  :version "20.3"
953
  :type 'face)
954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969

(defvar help-back-label "[back]"
  "Label to use by `help-make-xrefs' for the go-back reference.")

(defvar help-xref-symbol-regexp
  (concat "\\(\\<\\(\\(variable\\|option\\)\\|"
          "\\(function\\|command\\)\\|"
          "\\(symbol\\)\\)\\s-+\\)?"
          ;; Note starting with word-syntax character:
          "`\\(\\sw\\(\\sw\\|\\s_\\)+\\)'")
  "Regexp matching doc string references to symbols.

The words preceding the quoted symbol can be used in doc strings to
distinguish references to variables, functions and symbols.")

(defvar help-xref-info-regexp
970
  "\\<[Ii]nfo[ \t\n]+node[ \t\n]+`\\([^']+\\)'"
971 972 973 974 975
  "Regexp matching doc string references to an Info node.")

(defun help-setup-xref (item interactive-p)
  "Invoked from commands using the \"*Help*\" buffer to install some xref info.

976
ITEM is a (FUNCTION . ARGS) pair appropriate for recreating the help
977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011
buffer after following a reference.  INTERACTIVE-P is non-nil if the
calling command was invoked interactively.  In this case the stack of
items for help buffer \"back\" buttons is cleared."
  (if interactive-p
      (setq help-xref-stack nil))
  (setq help-xref-stack-item item))

(defun help-make-xrefs (&optional buffer)
  "Parse and hyperlink documentation cross-references in the given BUFFER.

Find cross-reference information in a buffer and, if
`help-highlight-p' is non-nil, highlight it with face defined by
`help-highlight-face'; activate such cross references for selection
with `help-follow'.  Cross-references have the canonical form `...'
and the type of reference may be disambiguated by the preceding
word(s) used in `help-xref-symbol-regexp'.

A special reference `back' is made to return back through a stack of
help buffers.  Variable `help-back-label' specifies the text for
that."
  (interactive "b")
  (save-excursion
    (set-buffer (or buffer (current-buffer)))
    (goto-char (point-min))
    ;; Skip the header-type info, though it might be useful to parse
    ;; it at some stage (e.g. "function in `library'").
    (forward-paragraph)
    (let ((old-modified (buffer-modified-p)))
      (let ((stab (syntax-table))
            (case-fold-search t)
            (inhibit-read-only t))
        (set-syntax-table emacs-lisp-mode-syntax-table)
        ;; The following should probably be abstracted out.
        (unwind-protect
            (progn
1012 1013 1014 1015 1016 1017 1018 1019
              ;; Info references
              (save-excursion
                (while (re-search-forward help-xref-info-regexp nil t)
                  (let ((data (match-string 1)))
		    (save-match-data
		      (unless (string-match "^([^)]+)" data)
			(setq data (concat "(emacs)" data))))
		    (help-xref-button 1 #'info data))))
1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044
              ;; Quoted symbols
              (save-excursion
                (while (re-search-forward help-xref-symbol-regexp nil t)
                  (let* ((data (match-string 6))
                         (sym (intern-soft data)))
                    (if sym
                        (cond
                         ((match-string 3) ; `variable' &c
                          (and (boundp sym) ; `variable' doesn't ensure
                                        ; it's actually bound
                               (help-xref-button 6 #'describe-variable sym)))
                         ((match-string 4) ; `function' &c
                          (and (fboundp sym) ; similarly
                               (help-xref-button 6 #'describe-function sym)))
                         ((match-string 5)) ; nothing for symbol
                         ((and (boundp sym) (fboundp sym))
                          ;; We can't intuit whether to use the
                          ;; variable or function doc -- supply both.
                          (help-xref-button 6 #'help-xref-interned sym))
                         ((boundp sym)
                          (help-xref-button 6 #'describe-variable sym))
                         ((fboundp sym)
                          (help-xref-button 6 #'describe-function sym)))))))
              ;; An obvious case of a key substitution:
              (save-excursion              
1045 1046 1047 1048
                (while (re-search-forward
			;; Assume command name is only word characters
			;; and dashes to get things like `use M-x foo.'.
                        "\\<M-x\\s-+\\(\\sw\\(\\sw\\|-\\)+\\)" nil t)
1049 1050
                  (let ((sym (intern-soft (match-string 1))))
                    (if (fboundp sym)
1051 1052 1053
                        (help-xref-button 1 #'describe-function sym)))))
              ;; Look for commands in whole keymap substitutions:
              (save-excursion
1054 1055
		;; Make sure to find the first keymap.
		(goto-char (point-min))
1056 1057 1058 1059 1060 1061 1062 1063
                ;; Find a header and the column at which the command
                ;; name will be found.
                (while (re-search-forward "^key +binding\n\\(-+ +\\)-+\n\n" 
                                          nil t)
                  (let ((col (- (match-end 1) (match-beginning 1))))
                    (while
                        ;; Ignore single blank lines in table, but not
                        ;; double ones, which should terminate it.
1064
                        (and (not (looking-at "\n\\s-*\n"))
1065
                             (progn
1066 1067 1068 1069
			       (and (eolp) (forward-line))
			       (end-of-line)
			       (skip-chars-backward "^\t\n")
                               (if (and (>= (current-column) col)
Dave Love's avatar
Dave Love committed
1070
					(looking-at "\\(\\sw\\|-\\)+$"))
1071 1072 1073 1074
                                   (let ((sym (intern-soft (match-string 0))))
                                     (if (fboundp sym)
                                         (help-xref-button 
                                          0 #'describe-function sym))))
1075
			       (zerop (forward-line)))))))))
1076 1077 1078 1079 1080 1081 1082 1083
          (set-syntax-table stab))
        ;; Make a back-reference in this buffer if appropriate.
        (when help-xref-stack
          (goto-char (point-max))
          (save-excursion
            (insert "\n\n" help-back-label))
          ;; Just to provide the match data:
          (looking-at (concat "\n\n\\(" (regexp-quote help-back-label) "\\)"))
1084
          (help-xref-button 1 #'help-xref-go-back (current-buffer))))
1085 1086 1087 1088
      ;; View mode steals RET from us.
      (set (make-local-variable 'minor-mode-overriding-map-alist)
           (list (cons 'view-mode
                       (let ((map (make-sparse-keymap)))
1089
                         (set-keymap-parent map view-mode-map)
1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100
                         (define-key map "\r" 'help-follow)
                         map))))
      (set-buffer-modified-p old-modified))))

(defun help-xref-button (match-number function data)
  "Make a hyperlink for cross-reference text previously matched.

MATCH-NUMBER is the subexpression of interest in the last matched
regexp.  FUNCTION is a function to invoke when the button is
activated, applied to DATA.  DATA may be a single value or a list.
See `help-make-xrefs'."
1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113
  ;; Don't mung properties we've added specially in some instances.
  (unless (get-text-property (match-beginning match-number) 'help-xref)
    (add-text-properties (match-beginning match-number)
			 (match-end match-number)
			 (list 'mouse-face 'highlight  
			       'help-xref (cons function
						(if (listp data)
						    data
						  (list data)))))
    (if help-highlight-p
	(put-text-property (match-beginning match-number)
			   (match-end match-number)
			   'face help-highlight-face))))
1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124


;; Additional functions for (re-)creating types of help buffers.
(defun help-xref-interned (symbol)
  "Follow a hyperlink which appeared to be an arbitrary interned SYMBOL.

Both variable and function documentation are extracted into a single
help buffer."
  (let ((fdoc (describe-function symbol)))
    (describe-variable symbol)
    ;; We now have a help buffer on the variable.  Insert the function
1125 1126 1127 1128 1129 1130
    ;; text before it.
    (with-current-buffer "*Help*"
      (goto-char (point-min))
      (let ((inhibit-read-only t))
	(insert fdoc "\n\n" (symbol-name symbol) " is also a variable.\n\n"))
      (help-setup-xref (list #'help-xref-interned symbol) nil))))
1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142

(defun help-xref-mode (buffer)
  "Do a `describe-mode' for the specified BUFFER."
  (save-excursion
    (set-buffer buffer)
    (describe-mode)))

;;; Navigation/hyperlinking with xrefs

(defun help-follow-mouse (click)
  "Follow the cross-reference that you click on."
  (interactive "e")
1143 1144 1145 1146
  (let* ((start (event-start click))
	 (window (car start))
	 (pos (car (cdr start))))
    (with-current-buffer (window-buffer window)
1147 1148
      (help-follow pos))))

1149
(defun help-xref-go-back (buffer)
1150
  "From BUFFER, go back to previous help buffer text using `help-xref-stack'."