help.el 40.7 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 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 29
;;`M-x help-for-help'.

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
(defun help-mode-maybe ()
  (if (eq major-mode 'fundamental-mode)
159
      (help-mode))
160 161 162 163 164
  (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)))
165 166
  (setq view-return-to-alist
	(list (cons (selected-window) help-return-method))))
167 168 169

(add-hook 'temp-buffer-show-hook 'help-mode-maybe)

Richard M. Stallman's avatar
Richard M. Stallman committed
170 171 172 173
(defun help-quit ()
  (interactive)
  nil)

174 175
(defun help-with-tutorial (&optional arg)
  "Select the Emacs learn-by-doing tutorial.
176
If there is a tutorial version written in the language
177
of the selected language environment, that version is used.
178
If there's no tutorial in that language, `TUTORIAL' is selected.
179
With arg, you are asked to choose which language."
180
  (interactive "P")
181 182 183 184
  (let ((lang (if arg
		  (read-language-name 'tutorial "Language: " "English")
		(if (get-language-info current-language-environment 'tutorial)
		    current-language-environment
185 186
		  "English")))
	file filename)
187
    (setq filename (get-language-info lang 'tutorial))
188
    (setq file (expand-file-name (concat "~/" filename)))
Richard M. Stallman's avatar
Richard M. Stallman committed
189 190 191 192 193 194
    (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
195
      (setq buffer-auto-save-file-name nil)
196
      (insert-file-contents (expand-file-name filename data-directory))
Richard M. Stallman's avatar
Richard M. Stallman committed
197 198 199 200
      (goto-char (point-min))
      (search-forward "\n<<")
      (beginning-of-line)
      (delete-region (point) (progn (end-of-line) (point)))
201
      (let ((n (- (window-height (selected-window))
Richard M. Stallman's avatar
Richard M. Stallman committed
202
		  (count-lines (point-min) (point))
203
		  6)))
204
	(if (< n 12)
205 206 207 208 209 210
	    (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
211 212 213
      (goto-char (point-min))
      (set-buffer-modified-p nil))))

214 215 216 217
(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")
218 219
  (save-excursion
    (let ((modifiers (event-modifiers (aref key 0)))
220
	  (standard-output (if insert (current-buffer) t))
221 222 223 224 225 226 227 228 229 230 231 232 233
	  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.
234 235
      (let ((defn (key-binding key))
	    (key-desc (key-description key)))
236
	(if (or (null defn) (integerp defn))
237 238
	    (princ (format "%s is undefined" key-desc))
	  (princ (format (if insert
239
			     "`%s' (`%s')"
240 241 242 243 244
			   (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
245

246 247 248 249 250 251 252
(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
253 254 255 256 257
(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))
258
       (let ((first-message
259
	      (cond ((special-display-p (buffer-name standard-output))
260
		     (setq help-return-method (cons (selected-window) t))
261 262 263 264 265 266 267 268
		     ;; 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))
269 270
		     (setq help-return-method
			   (cons (selected-window) 'quit-window))
271 272
		     "Type \\[switch-to-buffer-other-window] RET to restore the other window.")
		    (pop-up-windows
273
		     (setq help-return-method (cons (selected-window) t))
274 275
		     "Type \\[delete-other-windows] to remove help window.")
		    (t
276 277 278
		     (setq help-return-method
			   (list (selected-window) (window-buffer)
				 (window-start) (window-point)))
279 280 281 282 283 284 285
		     "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 "  " "")
286 287
		   ;; If the help buffer will go in a separate frame,
		   ;; it's no use mentioning a command to scroll, so don't.
288
		   (if (special-display-p (buffer-name standard-output))
289
		       nil
290
		     (if (same-window-p (buffer-name standard-output))
291 292 293 294
			 ;; Say how to scroll this window.
			 (substitute-command-keys
			  "\\[scroll-up] to scroll the help.")
		       ;; Say how to scroll some other window.
295
		       (substitute-command-keys
296
			"\\[scroll-other-window] to scroll the help."))))))))
Richard M. Stallman's avatar
Richard M. Stallman committed
297 298 299 300

(defun describe-key (key)
  "Display documentation of the function invoked by KEY.  KEY is a string."
  (interactive "kDescribe key: ")
301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323
  (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)))
      (let ((defn (key-binding key)))
	(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)
324 325
	    (princ "\n   which is ")
	    (describe-function-1 defn nil)
326
	    (print-help-return-message)))))))
Richard M. Stallman's avatar
Richard M. Stallman committed
327

328 329
(defun describe-mode ()
  "Display documentation of current major mode and minor modes.
Richard M. Stallman's avatar
Richard M. Stallman committed
330
For this to work correctly for a minor mode, the mode's indicator variable
331
\(listed in `minor-mode-alist') must also be a function whose documentation
Richard M. Stallman's avatar
Richard M. Stallman committed
332
describes the minor mode."
333
  (interactive)
Richard M. Stallman's avatar
Richard M. Stallman committed
334
  (with-output-to-temp-buffer "*Help*"
335
    (let ((minor-modes minor-mode-alist)
336
	  (first t))
337 338
      (while minor-modes
	(let* ((minor-mode (car (car minor-modes)))
339
	       (indicator (car (cdr (car minor-modes)))))
340 341 342
	  ;; Document a minor mode if it is listed in minor-mode-alist,
	  ;; bound locally in this buffer, non-nil, and has a function
	  ;; definition.
343
	  (if (and (symbol-value minor-mode)
344 345 346 347 348 349 350 351 352
		   (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)))))
		(while (and indicator (symbolp indicator))
		  (setq indicator (symbol-value indicator)))
353 354 355 356
		(if first
		    (princ "The minor modes are described first,
followed by the major mode, which is described on the last page.\n\f\n"))
		(setq first nil)
357 358 359 360 361
		(princ (format "%s minor mode (%s):\n"
			       pretty-minor-mode
			       (if indicator
				   (format "indicator%s" indicator)
				 "no indicator")))
362
		(princ (documentation minor-mode))
363
		(princ "\n\f\n"))))
364
	(setq minor-modes (cdr minor-modes))))
Richard M. Stallman's avatar
Richard M. Stallman committed
365
    (princ mode-name)
366
    (princ " mode:\n")
Richard M. Stallman's avatar
Richard M. Stallman committed
367
    (princ (documentation major-mode))
368
    (help-setup-xref (list #'help-xref-mode (current-buffer)) (interactive-p))
Richard M. Stallman's avatar
Richard M. Stallman committed
369 370 371 372 373 374 375 376 377
    (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
378
   (expand-file-name "DISTRIB" data-directory)))
Richard M. Stallman's avatar
Richard M. Stallman committed
379 380 381 382 383

(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
384
   (expand-file-name "COPYING" data-directory))
Richard M. Stallman's avatar
Richard M. Stallman committed
385 386
  (goto-char (point-min)))

387 388 389 390 391 392 393
(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
394 395 396 397 398 399 400 401
(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)))

402
(defun describe-prefix-bindings ()
403 404 405
  "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."
406
  (interactive)
407 408 409 410 411 412 413 414 415 416
  (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)))))
417 418
;; Make C-h after a prefix, when not specifically bound, 
;; run describe-prefix-bindings.
419 420
(setq prefix-help-command 'describe-prefix-bindings)

421 422 423 424 425 426 427 428
(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
429

430 431 432 433 434
(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
435 436 437 438
(defun view-lossage ()
  "Display last 100 input keystrokes."
  (interactive)
  (with-output-to-temp-buffer "*Help*"
439 440 441 442 443 444 445 446
    (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
447 448 449 450 451
    (save-excursion
      (set-buffer standard-output)
      (goto-char (point-min))
      (while (progn (move-to-column 50) (not (eobp)))
	(search-forward " " nil t)
452 453 454
	(insert "\n"))
      (setq help-xref-stack nil
	    help-xref-stack-item nil))
Richard M. Stallman's avatar
Richard M. Stallman committed
455 456
    (print-help-return-message)))

Richard M. Stallman's avatar
Richard M. Stallman committed
457
(defalias 'help 'help-for-help)
458
(make-help-screen help-for-help
459
  "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:"
460
  "You have typed \\[help-command], the help character.  Type a Help option:
461
\(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
462

463 464 465
a  command-apropos.  Give a substring, and see a list of commands
	(functions interactively callable) that contain
	that substring.  See also the  apropos  command.
466 467
b  describe-bindings.  Display table of all key bindings.
c  describe-key-briefly.  Type a command key sequence;
468
	it prints the function name that sequence runs.
469 470 471
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).
472
f  describe-function.  Type a function name and get documentation of it.
473 474
C-f Info-goto-emacs-command-node.  Type a function name;
	it takes you to the Info node for that command.
475
i  info. The  info  documentation reader.
476 477
I  describe-input-method.  Describe a specific input method (if you type
	its name) or the current input method (if you type just RET).
478
k  describe-key.  Type a command key sequence;
479 480 481
	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.
482
l  view-lossage.  Shows last 100 characters you typed.
483 484 485
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).
486 487
m  describe-mode.  Print documentation of current minor modes,
	and the current major mode, including their special commands.
488 489 490 491 492
n  view-emacs-news.  Shows emacs news file.
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;
493
	it displays the variable's documentation and value.
494
w  where-is.  Type command name; it prints which keystrokes
495
	invoke that command.
496 497 498 499 500 501 502 503

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."
504
  help-map)
Richard M. Stallman's avatar
Richard M. Stallman committed
505 506 507 508 509

;; Return a function which is called by the list containing point.
;; If that gives no function, return a function whose name is around point.
;; If that doesn't give a function, return nil.
(defun function-called-at-point ()
510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528
  (let ((stab (syntax-table)))
    (set-syntax-table emacs-lisp-mode-syntax-table)
    (unwind-protect
	(or (condition-case ()
		(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))
	    (condition-case ()
529 530 531 532 533 534 535 536
		(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)))
537 538
	      (error nil)))
      (set-syntax-table stab))))
Richard M. Stallman's avatar
Richard M. Stallman committed
539

540 541 542 543 544 545 546 547 548
(defun describe-function-find-file (function)
  (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
549 550 551 552 553 554 555 556 557
(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: ")
558
				obarray 'fboundp t nil nil (symbol-name fn)))
Richard M. Stallman's avatar
Richard M. Stallman committed
559 560
     (list (if (equal val "")
	       fn (intern val)))))
561 562 563
  (if function
      (with-output-to-temp-buffer "*Help*"
	(prin1 function)
564 565 566
	;; Use " is " instead of a colon so that
	;; it is easier to get out the function name using forward-sexp.
	(princ " is ")
567
	(describe-function-1 function nil)
568 569 570 571 572 573 574
	(print-help-return-message)
	(save-excursion
	  (set-buffer standard-output)
	  ;; Return the text we displayed.
	  (buffer-string)))
    (message "You didn't specify a function")))

575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613
(defun describe-function-1 (function parens)
  (let* ((def (symbol-function function))
	 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)
		 (format "alias for `%s'" def))
		((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))
		 (format "%s autoloaded Lisp %s"
			 (if (commandp def) "an interactive" "an")
			 (if (nth 4 def) "macro" "function")
			 ))
		(t "")))
    (when (and parens (not (equal string "")))
      (setq need-close t)
      (princ "("))
    (princ string)
    (or file-name
	(setq file-name (describe-function-find-file function)))
    (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)
614 615 616 617 618
	  (princ "'")
	  ;; Make a hyperlink to the library.
	  (with-current-buffer "*Help*"
	    (save-excursion
	      (re-search-backward "`\\([^`']+\\)'" nil t)
619 620 621
	      (help-xref-button 1 #'(lambda (arg)
				      (let ((location
					     (find-function-noselect arg)))
622 623
					(pop-to-buffer (car location))
					(goto-char (cdr location))))
624
				function)))))
625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648
    (if need-close (princ ")"))
    (princ ".")
    (terpri)
    (let* ((inner-function (if (and (listp def) 'macro)
			       (cdr def)
			     def))
	   (arglist (cond ((byte-code-function-p inner-function)
			   (car (append inner-function nil)))
			  ((eq (car-safe inner-function) 'lambda)
			   (nth 1 inner-function))
			  (t t))))
      (if (listp arglist)
	  (progn
	    (princ (cons function
			 (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)
649
		 (help-setup-xref (list #'describe-function function) (interactive-p)))
650 651
	(princ "not documented")))))

652
;; We return 0 if we can't find a variable to return.
Richard M. Stallman's avatar
Richard M. Stallman committed
653 654
(defun variable-at-point ()
  (condition-case ()
655 656 657 658 659 660 661 662 663 664
      (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))))
665 666
		(or (and (symbolp obj) (boundp obj) obj)
		    0)))
667
	  (set-syntax-table stab)))
668
    (error 0)))
Richard M. Stallman's avatar
Richard M. Stallman committed
669 670 671 672 673 674 675 676

(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)
677
     (setq val (completing-read (if (symbolp v)
Richard M. Stallman's avatar
Richard M. Stallman committed
678 679
				    (format "Describe variable (default %s): " v)
				  "Describe variable: ")
680 681
				obarray 'boundp t nil nil
				(if (symbolp v) (symbol-name v))))
Richard M. Stallman's avatar
Richard M. Stallman committed
682 683
     (list (if (equal val "")
	       v (intern val)))))
684
  (if (symbolp variable)
685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722
      (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.")))
723
          (help-setup-xref (list #'describe-variable variable) (interactive-p))
724 725

	  ;; Make a link to customize if this variable can be customized.
Richard M. Stallman's avatar
Richard M. Stallman committed
726 727 728 729
	  ;; Note, it is not reliable to test for a custom-type property
	  ;; because those are only present after the var's definition
	  ;; has been loaded.
	  (if (user-variable-p variable)
730 731 732 733 734 735 736 737 738 739 740 741
	      (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)
		    ))))

742 743 744 745 746
	  (print-help-return-message)
	  (save-excursion
	    (set-buffer standard-output)
	    ;; Return the text we displayed.
	    (buffer-string))))
747
    (message "You did not specify a variable")))
Richard M. Stallman's avatar
Richard M. Stallman committed
748

749
(defun describe-bindings (&optional prefix buffer)
750 751 752 753
  "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;
754 755 756
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)."
757
  (interactive "P")
758 759 760
  (or buffer (setq buffer (current-buffer)))
  (with-current-buffer buffer
    (describe-bindings-internal nil prefix))
761
  (with-current-buffer "*Help*"
762 763
    (help-setup-xref (list #'describe-bindings prefix buffer)
		     (interactive-p))))
764

765
(defun where-is (definition &optional insert)
766
  "Print message listing key sequences that invoke specified command.
767 768
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."
769 770 771 772 773 774 775 776 777
  (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 "")
778 779
	       fn (intern val))
	   current-prefix-arg)))
780
  (let* ((keys (where-is-internal definition overriding-local-map nil nil))
781 782 783 784 785 786 787 788 789
	 (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)))))
790 791
  nil)

792
(defun locate-library (library &optional nosuffix path interactive-call)
793
  "Show the precise file name of Emacs library LIBRARY.
Richard M. Stallman's avatar
Richard M. Stallman committed
794 795 796
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'
797 798 799 800
to the specified name LIBRARY.

If the optional third arg PATH is specified, that list of directories
is used instead of `load-path'."
801 802 803
  (interactive (list (read-string "Locate library: ")
		     nil nil
		     t))
804
  (let (result)
805 806
    (catch 'answer
      (mapcar
807 808 809 810 811 812 813 814 815 816 817
       (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
	      '("")
818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833
	    '(".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))
	    )))
834 835 836 837 838 839
       (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
840

841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862

;;; 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
`help-highlight-face'.  On a character terminal highlighted
references look like cross-references in info mode."
 :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"
863
  :type 'face)
864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885

(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
  "\\<info\\s-+node\\s-`\\([^']+\\)'"
  "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.

886
ITEM is a (FUNCTION . ARGS) pair appropriate for recreating the help
887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954
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
              ;; 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)))))))
              ;; Info references
              (save-excursion
                (while (re-search-forward help-xref-info-regexp nil t)
                  (help-xref-button 1 #'Info-goto-node (list (match-data 1)))))
              ;; An obvious case of a key substitution:
              (save-excursion              
                (while (re-search-forward 
                        "\\<M-x\\s-+\\(\\sw\\(\\sw\\|\\s_\\)+\\)" nil t)
                  (let ((sym (intern-soft (match-string 1))))
                    (if (fboundp sym)
955 956 957
                        (help-xref-button 1 #'describe-function sym)))))
              ;; Look for commands in whole keymap substitutions:
              (save-excursion
958 959
		;; Make sure to find the first keymap.
		(goto-char (point-min))
960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979
                ;; 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.
                        (and (looking-at "^\n?[^\n]")
                             (progn
                               (if (and (> (move-to-column col) 0)
                                        (looking-at "\\(\\sw\\|\\s_\\)+$"))
                                   ;; 
                                   (let ((sym (intern-soft (match-string 0))))
                                     (if (fboundp sym)
                                         (help-xref-button 
                                          0 #'describe-function sym))))
                               t)
                             (zerop (forward-line))
                             (move-to-column 0)))))))
980 981 982 983 984 985 986 987
          (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) "\\)"))
988
          (help-xref-button 1 #'help-xref-go-back (current-buffer))))
989 990 991 992
      ;; View mode steals RET from us.
      (set (make-local-variable 'minor-mode-overriding-map-alist)
           (list (cons 'view-mode
                       (let ((map (make-sparse-keymap)))
993
                         (set-keymap-parent map view-mode-map)
994 995 996 997 998 999 1000 1001 1002 1003 1004
                         (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'."
1005
  (add-text-properties (match-beginning match-number)
1006
                     (match-end match-number)
1007
                       (list 'mouse-face 'highlight  
1008 1009 1010 1011
                     'help-xref (cons function
                                      (if (listp data)
                                          data
                                        (list data)))))
1012 1013 1014 1015
  (if help-highlight-p
      (put-text-property (match-beginning match-number)
                         (match-end match-number)
                         'face help-highlight-face)))
1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030


;; 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
    ;; text after it.
    (goto-char (point-max))
    (insert "\n\n" fdoc))
  (goto-char (point-min))
1031
  (help-setup-xref (list #'help-xref-interned symbol) nil))
1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043

(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")
1044 1045 1046 1047
  (let* ((start (event-start click))
	 (window (car start))
	 (pos (car (cdr start))))
    (with-current-buffer (window-buffer window)
1048 1049
      (help-follow pos))))

1050 1051
(defun help-xref-go-back (buffer)
  "Go back to the previous help buffer text using info on `help-xref-stack'."
1052
  (interactive)
1053
  (let (item position method args)
1054 1055 1056 1057
    (with-current-buffer buffer
      (when help-xref-stack
	(setq help-xref-stack (cdr help-xref-stack)) ; due to help-follow
	(setq item (car help-xref-stack)
1058 1059 1060
	      position (car item)
	      method (cadr item)
	      args (cddr item))
1061
	(setq help-xref-stack (cdr help-xref-stack))))
1062 1063
    (apply method args)
    (goto-char position)))
1064 1065 1066 1067 1068 1069 1070 1071 1072 1073

(defun help-go-back ()
  (interactive)
  (help-follow (1- (point-max))))

(defun help-follow (&optional pos)
  "Follow cross-reference at POS, defaulting to point.

For the cross-reference format, see `help-make-xrefs'."
  (interactive "d")
1074 1075 1076 1077
  (let* ((help-data (or (and (not (= pos (point-max)))
			     (get-text-property pos 'help-xref))
			(and (not (= pos (point-min)))
			     (get-text-property (1- pos) 'help-xref))))
1078 1079
         (method (car help-data))
         (args (cdr help-data)))
1080 1081
    (setq help-xref-stack (cons (cons (point) help-xref-stack-item)
				help-xref-stack))
1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093
    (setq help-xref-stack-item nil)
    (when help-data
      ;; There is a reference at point.  Follow it.
      (apply method args))))

;; For tabbing through buffer.
(defun help-next-ref ()
  "Find the next help cross-reference in the buffer."
  (interactive)
  (let (pos)
    (while (not pos) 
      (if (get-text-property (point) 'help-xref) ; move off reference
1094 1095
	   (goto-char (or (next-single-property-change (point) 'help-xref)
                          (point))))
1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119
      (cond ((setq pos (next-single-property-change (point) 'help-xref))
	     (if pos (goto-char pos)))
	    ((bobp)
	     (message "No cross references in the buffer.")
	     (setq pos t))
	    (t				; be circular
	     (goto-char (point-min)))))))

(defun help-previous-ref ()
  "Find the previous help cross-reference in the buffer."
  (interactive)
  (let (pos)
    (while (not pos) 
      (if (get-text-property (point) 'help-xref) ; move off reference
	  (goto-char (or (previous-single-property-change (point) 'help-xref)
                         (point))))
      (cond ((setq pos (previous-single-property-change (point) 'help-xref))
	     (if pos (goto-char pos)))
	    ((bobp)
	     (message "No cross references in the buffer.")
	     (setq pos t))
	    (t				; be circular
	     (goto-char (point-max)))))))

Eric S. Raymond's avatar
Eric S. Raymond committed
1120
;;; help.el ends here