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[emacs.git] / lisp / help-mode.el
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1 ;;; help-mode.el --- `help-mode' used by *Help* buffers
3 ;; Copyright (C) 1985, 1986, 1993, 1994, 1998, 1999, 2000, 2001, 2002, 2004
4 ;; Free Software Foundation, Inc.
6 ;; Maintainer: FSF
7 ;; Keywords: help, internal
9 ;; This file is part of GNU Emacs.
11 ;; GNU Emacs is free software; you can redistribute it and/or modify
12 ;; it under the terms of the GNU General Public License as published by
13 ;; the Free Software Foundation; either version 2, or (at your option)
14 ;; any later version.
16 ;; GNU Emacs is distributed in the hope that it will be useful,
17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 ;; GNU General Public License for more details.
21 ;; You should have received a copy of the GNU General Public License
22 ;; along with GNU Emacs; see the file COPYING. If not, write to the
23 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
24 ;; Boston, MA 02111-1307, USA.
26 ;;; Commentary:
28 ;; Defines `help-mode', which is the mode used by *Help* buffers, and
29 ;; associated support machinery, such as adding hyperlinks, etc.,
31 ;;; Code:
33 (require 'button)
34 (require 'view)
36 (defvar help-mode-map (make-sparse-keymap)
37 "Keymap for help mode.")
39 (set-keymap-parent help-mode-map button-buffer-map)
41 (define-key help-mode-map [mouse-2] 'help-follow-mouse)
42 (define-key help-mode-map "\C-c\C-b" 'help-go-back)
43 (define-key help-mode-map "\C-c\C-c" 'help-follow)
44 ;; Documentation only, since we use minor-mode-overriding-map-alist.
45 (define-key help-mode-map "\r" 'help-follow)
47 (defvar help-xref-stack nil
48 "A stack of ways by which to return to help buffers after following xrefs.
49 Used by `help-follow' and `help-xref-go-back'.
50 An element looks like (POSITION FUNCTION ARGS...).
51 To use the element, do (apply FUNCTION ARGS) then goto the point.")
52 (put 'help-xref-stack 'permanent-local t)
53 (make-variable-buffer-local 'help-xref-stack)
55 (defvar help-xref-stack-item nil
56 "An item for `help-follow' in this buffer to push onto `help-xref-stack'.
57 The format is (FUNCTION ARGS...).")
58 (put 'help-xref-stack-item 'permanent-local t)
59 (make-variable-buffer-local 'help-xref-stack-item)
61 (setq-default help-xref-stack nil help-xref-stack-item nil)
63 (defcustom help-mode-hook nil
64 "Hook run by `help-mode'."
65 :type 'hook
66 :group 'help)
68 ;; Button types used by help
70 (define-button-type 'help-xref
71 'action #'help-button-action)
73 (defun help-button-action (button)
74 "Call BUTTON's help function."
75 (help-do-xref (button-start button)
76 (button-get button 'help-function)
77 (button-get button 'help-args)))
79 ;; These 6 calls to define-button-type were generated in a dolist
80 ;; loop, but that is bad because it means these button types don't
81 ;; have an easily found definition.
83 (define-button-type 'help-function
84 :supertype 'help-xref
85 'help-function 'describe-function
86 'help-echo (purecopy "mouse-2, RET: describe this function"))
88 (define-button-type 'help-variable
89 :supertype 'help-xref
90 'help-function 'describe-variable
91 'help-echo (purecopy "mouse-2, RET: describe this variable"))
93 (define-button-type 'help-face
94 :supertype 'help-xref
95 'help-function 'describe-face
96 'help-echo (purecopy "mouse-2, RET: describe this face"))
98 (define-button-type 'help-coding-system
99 :supertype 'help-xref
100 'help-function 'describe-coding-system
101 'help-echo (purecopy "mouse-2, RET: describe this coding system"))
103 (define-button-type 'help-input-method
104 :supertype 'help-xref
105 'help-function 'describe-input-method
106 'help-echo (purecopy "mouse-2, RET: describe this input method"))
108 (define-button-type 'help-character-set
109 :supertype 'help-xref
110 'help-function 'describe-character-set
111 'help-echo (purecopy "mouse-2, RET: describe this character set"))
113 ;; make some more ideosyncratic button types
115 (define-button-type 'help-symbol
116 :supertype 'help-xref
117 'help-function #'help-xref-interned
118 'help-echo (purecopy "mouse-2, RET: describe this symbol"))
120 (define-button-type 'help-back
121 :supertype 'help-xref
122 'help-function #'help-xref-go-back
123 'help-echo (purecopy "mouse-2, RET: go back to previous help buffer"))
125 (define-button-type 'help-info
126 :supertype 'help-xref
127 'help-function #'info
128 'help-echo (purecopy"mouse-2, RET: read this Info node"))
130 (define-button-type 'help-customize-variable
131 :supertype 'help-xref
132 'help-function (lambda (v)
133 (if help-xref-stack
134 (pop help-xref-stack))
135 (customize-variable v))
136 'help-echo (purecopy "mouse-2, RET: customize variable"))
138 (define-button-type 'help-customize-face
139 :supertype 'help-xref
140 'help-function (lambda (v)
141 (if help-xref-stack
142 (pop help-xref-stack))
143 (customize-face v))
144 'help-echo (purecopy "mouse-2, RET: customize face"))
146 (define-button-type 'help-function-def
147 :supertype 'help-xref
148 'help-function (lambda (fun file)
149 (require 'find-func)
150 (when (eq file 'C-source)
151 (setq file
152 (help-C-file-name (indirect-function fun) 'fun)))
153 ;; Don't use find-function-noselect because it follows
154 ;; aliases (which fails for built-in functions).
155 (let ((location
156 (find-function-search-for-symbol fun nil file)))
157 (pop-to-buffer (car location))
158 (goto-char (cdr location))))
159 'help-echo (purecopy "mouse-2, RET: find function's definition"))
161 (define-button-type 'help-variable-def
162 :supertype 'help-xref
163 'help-function (lambda (var &optional file)
164 (when (eq file 'C-source)
165 (setq file (help-C-file-name var 'var)))
166 (let ((location (find-variable-noselect var file)))
167 (pop-to-buffer (car location))
168 (goto-char (cdr location))))
169 'help-echo (purecopy"mouse-2, RET: find variable's definition"))
172 ;;;###autoload
173 (defun help-mode ()
174 "Major mode for viewing help text and navigating references in it.
175 Entry to this mode runs the normal hook `help-mode-hook'.
176 Commands:
177 \\{help-mode-map}"
178 (interactive)
179 (kill-all-local-variables)
180 (use-local-map help-mode-map)
181 (setq mode-name "Help")
182 (setq major-mode 'help-mode)
183 (view-mode)
184 (make-local-variable 'view-no-disable-on-exit)
185 (setq view-no-disable-on-exit t)
186 (run-hooks 'help-mode-hook))
188 ;;;###autoload
189 (defun help-mode-setup ()
190 (help-mode)
191 (setq buffer-read-only nil))
193 ;;;###autoload
194 (defun help-mode-finish ()
195 (let ((entry (assq (selected-window) view-return-to-alist)))
196 (if entry (setcdr entry (cons (selected-window)
197 help-return-method))
198 (setq view-return-to-alist
199 (cons (cons (selected-window) help-return-method)
200 view-return-to-alist))))
201 (when (eq major-mode 'help-mode)
202 ;; View mode's read-only status of existing *Help* buffer is lost
203 ;; by with-output-to-temp-buffer.
204 (toggle-read-only 1)
205 (help-make-xrefs (current-buffer))))
207 ;; Grokking cross-reference information in doc strings and
208 ;; hyperlinking it.
210 ;; This may have some scope for extension and the same or something
211 ;; similar should be done for widget doc strings, which currently use
212 ;; another mechanism.
214 (defvar help-back-label (purecopy "[back]")
215 "Label to use by `help-make-xrefs' for the go-back reference.")
217 (defconst help-xref-symbol-regexp
218 (purecopy (concat "\\(\\<\\(\\(variable\\|option\\)\\|"
219 "\\(function\\|command\\)\\|"
220 "\\(face\\)\\|"
221 "\\(symbol\\)\\|"
222 "\\(source \\(?:code \\)?\\(?:of\\|for\\)\\)\\)"
223 "[ \t\n]+\\)?"
224 ;; Note starting with word-syntax character:
225 "`\\(\\sw\\(\\sw\\|\\s_\\)+\\)'"))
226 "Regexp matching doc string references to symbols.
228 The words preceding the quoted symbol can be used in doc strings to
229 distinguish references to variables, functions and symbols.")
231 (defvar help-xref-mule-regexp nil
232 "Regexp matching doc string references to MULE-related keywords.
234 It is usually nil, and is temporarily bound to an appropriate regexp
235 when help commands related to multilingual environment (e.g.,
236 `describe-coding-system') are invoked.")
239 (defconst help-xref-info-regexp
240 (purecopy "\\<[Ii]nfo[ \t\n]+\\(node\\|anchor\\)[ \t\n]+`\\([^']+\\)'")
241 "Regexp matching doc string references to an Info node.")
243 ;;;###autoload
244 (defun help-setup-xref (item interactive-p)
245 "Invoked from commands using the \"*Help*\" buffer to install some xref info.
247 ITEM is a (FUNCTION . ARGS) pair appropriate for recreating the help
248 buffer after following a reference. INTERACTIVE-P is non-nil if the
249 calling command was invoked interactively. In this case the stack of
250 items for help buffer \"back\" buttons is cleared.
252 This should be called very early, before the output buffer is cleared,
253 because we want to record the \"previous\" position of point so we can
254 restore it properly when going back."
255 (with-current-buffer (help-buffer)
256 (when help-xref-stack-item
257 (push (cons (point) help-xref-stack-item) help-xref-stack))
258 (when interactive-p
259 (let ((tail (nthcdr 10 help-xref-stack)))
260 ;; Truncate the stack.
261 (if tail (setcdr tail nil))))
262 (setq help-xref-stack-item item)))
264 (defvar help-xref-following nil
265 "Non-nil when following a help cross-reference.")
267 (defun help-buffer ()
268 (buffer-name ;for with-output-to-temp-buffer
269 (if help-xref-following
270 (current-buffer)
271 (get-buffer-create "*Help*"))))
273 (defvar help-xref-override-view-map
274 (let ((map (make-sparse-keymap)))
275 (set-keymap-parent map view-mode-map)
276 (define-key map "\r" nil)
277 map)
278 "Replacement keymap for `view-mode' in help buffers.")
280 ;;;###autoload
281 (defun help-make-xrefs (&optional buffer)
282 "Parse and hyperlink documentation cross-references in the given BUFFER.
284 Find cross-reference information in a buffer and activate such cross
285 references for selection with `help-follow'. Cross-references have
286 the canonical form `...' and the type of reference may be
287 disambiguated by the preceding word(s) used in
288 `help-xref-symbol-regexp'. Faces only get cross-referenced if
289 preceded or followed by the word `face'. Variables without
290 variable documentation do not get cross-referenced, unless
291 preceded by the word `variable' or `option'.
293 If the variable `help-xref-mule-regexp' is non-nil, find also
294 cross-reference information related to multilingual environment
295 \(e.g., coding-systems). This variable is also used to disambiguate
296 the type of reference as the same way as `help-xref-symbol-regexp'.
298 A special reference `back' is made to return back through a stack of
299 help buffers. Variable `help-back-label' specifies the text for
300 that."
301 (interactive "b")
302 (save-excursion
303 (set-buffer (or buffer (current-buffer)))
304 (goto-char (point-min))
305 ;; Skip the header-type info, though it might be useful to parse
306 ;; it at some stage (e.g. "function in `library'").
307 (forward-paragraph)
308 (let ((old-modified (buffer-modified-p)))
309 (let ((stab (syntax-table))
310 (case-fold-search t)
311 (inhibit-read-only t))
312 (set-syntax-table emacs-lisp-mode-syntax-table)
313 ;; The following should probably be abstracted out.
314 (unwind-protect
315 (progn
316 ;; Info references
317 (save-excursion
318 (while (re-search-forward help-xref-info-regexp nil t)
319 (let ((data (match-string 2)))
320 (save-match-data
321 (unless (string-match "^([^)]+)" data)
322 (setq data (concat "(emacs)" data))))
323 (help-xref-button 2 'help-info data))))
324 ;; Mule related keywords. Do this before trying
325 ;; `help-xref-symbol-regexp' because some of Mule
326 ;; keywords have variable or function definitions.
327 (if help-xref-mule-regexp
328 (save-excursion
329 (while (re-search-forward help-xref-mule-regexp nil t)
330 (let* ((data (match-string 7))
331 (sym (intern-soft data)))
332 (cond
333 ((match-string 3) ; coding system
334 (and sym (coding-system-p sym)
335 (help-xref-button 6 'help-coding-system sym)))
336 ((match-string 4) ; input method
337 (and (assoc data input-method-alist)
338 (help-xref-button 7 'help-input-method data)))
339 ((or (match-string 5) (match-string 6)) ; charset
340 (and sym (charsetp sym)
341 (help-xref-button 7 'help-character-set sym)))
342 ((assoc data input-method-alist)
343 (help-xref-button 7 'help-character-set data))
344 ((and sym (coding-system-p sym))
345 (help-xref-button 7 'help-coding-system sym))
346 ((and sym (charsetp sym))
347 (help-xref-button 7 'help-character-set sym)))))))
348 ;; Quoted symbols
349 (save-excursion
350 (while (re-search-forward help-xref-symbol-regexp nil t)
351 (let* ((data (match-string 8))
352 (sym (intern-soft data)))
353 (if sym
354 (cond
355 ((match-string 3) ; `variable' &c
356 (and (boundp sym) ; `variable' doesn't ensure
357 ; it's actually bound
358 (help-xref-button 8 'help-variable sym)))
359 ((match-string 4) ; `function' &c
360 (and (fboundp sym) ; similarly
361 (help-xref-button 8 'help-function sym)))
362 ((match-string 5) ; `face'
363 (and (facep sym)
364 (help-xref-button 8 'help-face sym)))
365 ((match-string 6)) ; nothing for `symbol'
366 ((match-string 7)
367 ;;; this used:
368 ;;; #'(lambda (arg)
369 ;;; (let ((location
370 ;;; (find-function-noselect arg)))
371 ;;; (pop-to-buffer (car location))
372 ;;; (goto-char (cdr location))))
373 (help-xref-button 8 'help-function-def sym))
374 ((facep sym)
375 (if (save-match-data (looking-at "[ \t\n]+face\\W"))
376 (help-xref-button 8 'help-face sym)))
377 ((and (boundp sym) (fboundp sym))
378 ;; We can't intuit whether to use the
379 ;; variable or function doc -- supply both.
380 (help-xref-button 8 'help-symbol sym))
381 ((and
382 (boundp sym)
384 (documentation-property
385 sym 'variable-documentation)
386 (condition-case nil
387 (documentation-property
388 (indirect-variable sym)
389 'variable-documentation)
390 (cyclic-variable-indirection nil))))
391 (help-xref-button 8 'help-variable sym))
392 ((fboundp sym)
393 (help-xref-button 8 'help-function sym)))))))
394 ;; An obvious case of a key substitution:
395 (save-excursion
396 (while (re-search-forward
397 ;; Assume command name is only word characters
398 ;; and dashes to get things like `use M-x foo.'.
399 "\\<M-x\\s-+\\(\\sw\\(\\sw\\|-\\)+\\)" nil t)
400 (let ((sym (intern-soft (match-string 1))))
401 (if (fboundp sym)
402 (help-xref-button 1 'help-function sym)))))
403 ;; Look for commands in whole keymap substitutions:
404 (save-excursion
405 ;; Make sure to find the first keymap.
406 (goto-char (point-min))
407 ;; Find a header and the column at which the command
408 ;; name will be found.
410 ;; If the keymap substitution isn't the last thing in
411 ;; the doc string, and if there is anything on the
412 ;; same line after it, this code won't recognize the end of it.
413 (while (re-search-forward "^key +binding\n\\(-+ +\\)-+\n\n"
414 nil t)
415 (let ((col (- (match-end 1) (match-beginning 1))))
416 (while
417 (and (not (eobp))
418 ;; Stop at a pair of blank lines.
419 (not (looking-at "\n\\s-*\n")))
420 ;; Skip a single blank line.
421 (and (eolp) (forward-line))
422 (end-of-line)
423 (skip-chars-backward "^\t\n")
424 (if (and (>= (current-column) col)
425 (looking-at "\\(\\sw\\|-\\)+$"))
426 (let ((sym (intern-soft (match-string 0))))
427 (if (fboundp sym)
428 (help-xref-button 0 'help-function sym))))
429 (forward-line))))))
430 (set-syntax-table stab))
431 ;; Delete extraneous newlines at the end of the docstring
432 (goto-char (point-max))
433 (while (and (not (bobp)) (bolp))
434 (delete-char -1))
435 (insert "\n")
436 ;; Make a back-reference in this buffer if appropriate.
437 (when help-xref-stack
438 (insert "\n")
439 (help-insert-xref-button help-back-label 'help-back
440 (current-buffer))
441 (insert "\n")))
442 ;; View mode steals RET from us.
443 (set (make-local-variable 'minor-mode-overriding-map-alist)
444 (list (cons 'view-mode help-xref-override-view-map)))
445 (set-buffer-modified-p old-modified))))
447 ;;;###autoload
448 (defun help-xref-button (match-number type &rest args)
449 "Make a hyperlink for cross-reference text previously matched.
450 MATCH-NUMBER is the subexpression of interest in the last matched
451 regexp. TYPE is the type of button to use. Any remaining arguments are
452 passed to the button's help-function when it is invoked.
453 See `help-make-xrefs'."
454 ;; Don't mung properties we've added specially in some instances.
455 (unless (button-at (match-beginning match-number))
456 (make-text-button (match-beginning match-number)
457 (match-end match-number)
458 'type type 'help-args args)))
460 ;;;###autoload
461 (defun help-insert-xref-button (string type &rest args)
462 "Insert STRING and make a hyperlink from cross-reference text on it.
463 TYPE is the type of button to use. Any remaining arguments are passed
464 to the button's help-function when it is invoked.
465 See `help-make-xrefs'."
466 (unless (button-at (point))
467 (insert-text-button string 'type type 'help-args args)))
469 ;;;###autoload
470 (defun help-xref-on-pp (from to)
471 "Add xrefs for symbols in `pp's output between FROM and TO."
472 (if (> (- to from) 5000) nil
473 (with-syntax-table emacs-lisp-mode-syntax-table
474 (save-excursion
475 (save-restriction
476 (narrow-to-region from to)
477 (goto-char (point-min))
478 (condition-case nil
479 (while (not (eobp))
480 (cond
481 ((looking-at "\"") (forward-sexp 1))
482 ((looking-at "#<") (search-forward ">" nil 'move))
483 ((looking-at "\\(\\(\\sw\\|\\s_\\)+\\)")
484 (let* ((sym (intern-soft (match-string 1)))
485 (type (cond ((fboundp sym) 'help-function)
486 ((or (memq sym '(t nil))
487 (keywordp sym))
488 nil)
489 ((and sym (boundp sym))
490 'help-variable))))
491 (when type (help-xref-button 1 type sym)))
492 (goto-char (match-end 1)))
493 (t (forward-char 1))))
494 (error nil)))))))
497 ;; Additional functions for (re-)creating types of help buffers.
498 (defun help-xref-interned (symbol)
499 "Follow a hyperlink which appeared to be an arbitrary interned SYMBOL.
500 Both variable, function and face documentation are extracted into a single
501 help buffer."
502 (with-current-buffer (help-buffer)
503 ;; Push the previous item on the stack before clobbering the output buffer.
504 (help-setup-xref nil nil)
505 (let ((facedoc (when (facep symbol)
506 ;; Don't record the current entry in the stack.
507 (setq help-xref-stack-item nil)
508 (describe-face symbol)))
509 (fdoc (when (fboundp symbol)
510 ;; Don't record the current entry in the stack.
511 (setq help-xref-stack-item nil)
512 (describe-function symbol)))
513 (sdoc (when (boundp symbol)
514 ;; Don't record the current entry in the stack.
515 (setq help-xref-stack-item nil)
516 (describe-variable symbol))))
517 (cond
518 (sdoc
519 ;; We now have a help buffer on the variable.
520 ;; Insert the function and face text before it.
521 (when (or fdoc facedoc)
522 (goto-char (point-min))
523 (let ((inhibit-read-only t))
524 (when fdoc
525 (insert fdoc "\n\n")
526 (when facedoc
527 (insert (make-string 30 ?-) "\n\n" (symbol-name symbol)
528 " is also a " "face." "\n\n")))
529 (when facedoc
530 (insert facedoc "\n\n"))
531 (insert (make-string 30 ?-) "\n\n" (symbol-name symbol)
532 " is also a " "variable." "\n\n"))
533 ;; Don't record the `describe-variable' item in the stack.
534 (setq help-xref-stack-item nil)
535 (help-setup-xref (list #'help-xref-interned symbol) nil)))
536 (fdoc
537 ;; We now have a help buffer on the function.
538 ;; Insert face text before it.
539 (when facedoc
540 (goto-char (point-max))
541 (let ((inhibit-read-only t))
542 (insert "\n\n" (make-string 30 ?-) "\n\n" (symbol-name symbol)
543 " is also a " "face." "\n\n" facedoc))
544 ;; Don't record the `describe-function' item in the stack.
545 (setq help-xref-stack-item nil)
546 (help-setup-xref (list #'help-xref-interned symbol) nil)))))))
549 ;; Navigation/hyperlinking with xrefs
551 (defun help-follow-mouse (click)
552 "Follow the cross-reference that you CLICK on."
553 (interactive "e")
554 (let* ((start (event-start click))
555 (window (car start))
556 (pos (car (cdr start))))
557 (with-current-buffer (window-buffer window)
558 (help-follow pos))))
560 (defun help-xref-go-back (buffer)
561 "From BUFFER, go back to previous help buffer text using `help-xref-stack'."
562 (let (item position method args)
563 (with-current-buffer buffer
564 (when help-xref-stack
565 (setq item (pop help-xref-stack)
566 ;; Clear the current item so that it won't get pushed
567 ;; by the function we're about to call. TODO: We could also
568 ;; push it onto a "forward" stack and add a `forw' button.
569 help-xref-stack-item nil
570 position (car item)
571 method (cadr item)
572 args (cddr item))))
573 (apply method args)
574 (with-current-buffer buffer
575 (if (get-buffer-window buffer)
576 (set-window-point (get-buffer-window buffer) position)
577 (goto-char position)))))
579 (defun help-go-back ()
580 "Go back to previous topic in this help buffer."
581 (interactive)
582 (if help-xref-stack
583 (help-xref-go-back (current-buffer))
584 (error "No previous help buffer.")))
586 (defun help-do-xref (pos function args)
587 "Call the help cross-reference function FUNCTION with args ARGS.
588 Things are set up properly so that the resulting help-buffer has
589 a proper [back] button."
590 ;; There is a reference at point. Follow it.
591 (let ((help-xref-following t))
592 (apply function args)))
594 (defun help-follow (&optional pos)
595 "Follow cross-reference at POS, defaulting to point.
597 For the cross-reference format, see `help-make-xrefs'."
598 (interactive "d")
599 (unless pos
600 (setq pos (point)))
601 (unless (push-button pos)
602 ;; check if the symbol under point is a function or variable
603 (let ((sym
604 (intern
605 (save-excursion
606 (goto-char pos) (skip-syntax-backward "w_")
607 (buffer-substring (point)
608 (progn (skip-syntax-forward "w_")
609 (point)))))))
610 (when (or (boundp sym) (fboundp sym) (facep sym))
611 (help-do-xref pos #'help-xref-interned (list sym))))))
614 (provide 'help-mode)
616 ;;; arch-tag: 850954ae-3725-4cb4-8e91-0bf6d52d6b0b
617 ;;; help-mode.el ends here