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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, 1998-2014 Free Software
4 ;; Foundation, Inc.
6 ;; Maintainer: emacs-devel@gnu.org
7 ;; Keywords: help, internal
8 ;; Package: emacs
10 ;; This file is part of GNU Emacs.
12 ;; GNU Emacs is free software: you can redistribute it and/or modify
13 ;; it under the terms of the GNU General Public License as published by
14 ;; the Free Software Foundation, either version 3 of the License, or
15 ;; (at your option) any later version.
17 ;; GNU Emacs is distributed in the hope that it will be useful,
18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 ;; GNU General Public License for more details.
22 ;; You should have received a copy of the GNU General Public License
23 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
25 ;;; Commentary:
27 ;; Defines `help-mode', which is the mode used by *Help* buffers, and
28 ;; associated support machinery, such as adding hyperlinks, etc.,
30 ;;; Code:
32 (require 'button)
33 (eval-when-compile (require 'easymenu))
35 (defvar help-mode-map
36 (let ((map (make-sparse-keymap)))
37 (set-keymap-parent map (make-composed-keymap button-buffer-map
38 special-mode-map))
39 (define-key map [mouse-2] 'help-follow-mouse)
40 (define-key map "l" 'help-go-back)
41 (define-key map "r" 'help-go-forward)
42 (define-key map "\C-c\C-b" 'help-go-back)
43 (define-key map "\C-c\C-f" 'help-go-forward)
44 (define-key map [XF86Back] 'help-go-back)
45 (define-key map [XF86Forward] 'help-go-forward)
46 (define-key map "\C-c\C-c" 'help-follow-symbol)
47 (define-key map "\r" 'help-follow)
48 map)
49 "Keymap for help mode.")
51 (easy-menu-define help-mode-menu help-mode-map
52 "Menu for Help Mode."
53 '("Help-Mode"
54 ["Show Help for Symbol" help-follow-symbol
55 :help "Show the docs for the symbol at point"]
56 ["Previous Topic" help-go-back
57 :help "Go back to previous topic in this help buffer"]
58 ["Next Topic" help-go-forward
59 :help "Go back to next topic in this help buffer"]
60 ["Move to Previous Button" backward-button
61 :help "Move to the Next Button in the help buffer"]
62 ["Move to Next Button" forward-button
63 :help "Move to the Next Button in the help buffer"]))
65 (defvar help-xref-stack nil
66 "A stack of ways by which to return to help buffers after following xrefs.
67 Used by `help-follow' and `help-xref-go-back'.
68 An element looks like (POSITION FUNCTION ARGS...).
69 To use the element, do (apply FUNCTION ARGS) then goto the point.")
70 (put 'help-xref-stack 'permanent-local t)
71 (make-variable-buffer-local 'help-xref-stack)
73 (defvar help-xref-forward-stack nil
74 "A stack used to navigate help forwards after using the back button.
75 Used by `help-follow' and `help-xref-go-forward'.
76 An element looks like (POSITION FUNCTION ARGS...).
77 To use the element, do (apply FUNCTION ARGS) then goto the point.")
78 (put 'help-xref-forward-stack 'permanent-local t)
79 (make-variable-buffer-local 'help-xref-forward-stack)
81 (defvar help-xref-stack-item nil
82 "An item for `help-follow' in this buffer to push onto `help-xref-stack'.
83 The format is (FUNCTION ARGS...).")
84 (put 'help-xref-stack-item 'permanent-local t)
85 (make-variable-buffer-local 'help-xref-stack-item)
87 (defvar help-xref-stack-forward-item nil
88 "An item for `help-go-back' to push onto `help-xref-forward-stack'.
89 The format is (FUNCTION ARGS...).")
90 (put 'help-xref-stack-forward-item 'permanent-local t)
91 (make-variable-buffer-local 'help-xref-stack-forward-item)
93 (setq-default help-xref-stack nil help-xref-stack-item nil)
94 (setq-default help-xref-forward-stack nil help-xref-forward-stack-item nil)
96 (defcustom help-mode-hook nil
97 "Hook run by `help-mode'."
98 :type 'hook
99 :group 'help)
101 ;; Button types used by help
103 (define-button-type 'help-xref
104 'follow-link t
105 'action #'help-button-action)
107 (defun help-button-action (button)
108 "Call BUTTON's help function."
109 (help-do-xref (button-start button)
110 (button-get button 'help-function)
111 (button-get button 'help-args)))
113 ;; These 6 calls to define-button-type were generated in a dolist
114 ;; loop, but that is bad because it means these button types don't
115 ;; have an easily found definition.
117 (define-button-type 'help-function
118 :supertype 'help-xref
119 'help-function 'describe-function
120 'help-echo (purecopy "mouse-2, RET: describe this function"))
122 (define-button-type 'help-variable
123 :supertype 'help-xref
124 'help-function 'describe-variable
125 'help-echo (purecopy "mouse-2, RET: describe this variable"))
127 (define-button-type 'help-face
128 :supertype 'help-xref
129 'help-function 'describe-face
130 'help-echo (purecopy "mouse-2, RET: describe this face"))
132 (define-button-type 'help-coding-system
133 :supertype 'help-xref
134 'help-function 'describe-coding-system
135 'help-echo (purecopy "mouse-2, RET: describe this coding system"))
137 (define-button-type 'help-input-method
138 :supertype 'help-xref
139 'help-function 'describe-input-method
140 'help-echo (purecopy "mouse-2, RET: describe this input method"))
142 (define-button-type 'help-character-set
143 :supertype 'help-xref
144 'help-function 'describe-character-set
145 'help-echo (purecopy "mouse-2, RET: describe this character set"))
147 ;; Make some more idiosyncratic button types.
149 (define-button-type 'help-symbol
150 :supertype 'help-xref
151 'help-function #'help-xref-interned
152 'help-echo (purecopy "mouse-2, RET: describe this symbol"))
154 (define-button-type 'help-back
155 :supertype 'help-xref
156 'help-function #'help-xref-go-back
157 'help-echo (purecopy "mouse-2, RET: go back to previous help buffer"))
159 (define-button-type 'help-forward
160 :supertype 'help-xref
161 'help-function #'help-xref-go-forward
162 'help-echo (purecopy "mouse-2, RET: move forward to next help buffer"))
164 (define-button-type 'help-info-variable
165 :supertype 'help-xref
166 ;; the name of the variable is put before the argument to Info
167 'help-function (lambda (_a v) (info v))
168 'help-echo (purecopy "mouse-2, RET: read this Info node"))
170 (define-button-type 'help-info
171 :supertype 'help-xref
172 'help-function #'info
173 'help-echo (purecopy "mouse-2, RET: read this Info node"))
175 (define-button-type 'help-url
176 :supertype 'help-xref
177 'help-function #'browse-url
178 'help-echo (purecopy "mouse-2, RET: view this URL in a browser"))
180 (define-button-type 'help-customize-variable
181 :supertype 'help-xref
182 'help-function (lambda (v)
183 (customize-variable v))
184 'help-echo (purecopy "mouse-2, RET: customize variable"))
186 (define-button-type 'help-customize-face
187 :supertype 'help-xref
188 'help-function (lambda (v)
189 (customize-face v))
190 'help-echo (purecopy "mouse-2, RET: customize face"))
192 (define-button-type 'help-function-def
193 :supertype 'help-xref
194 'help-function (lambda (fun file)
195 (require 'find-func)
196 (when (eq file 'C-source)
197 (setq file
198 (help-C-file-name (indirect-function fun) 'fun)))
199 ;; Don't use find-function-noselect because it follows
200 ;; aliases (which fails for built-in functions).
201 (let ((location
202 (find-function-search-for-symbol fun nil file)))
203 (pop-to-buffer (car location))
204 (if (cdr location)
205 (goto-char (cdr location))
206 (message "Unable to find location in file"))))
207 'help-echo (purecopy "mouse-2, RET: find function's definition"))
209 (define-button-type 'help-function-cmacro ; FIXME: Obsolete since 24.4.
210 :supertype 'help-xref
211 'help-function (lambda (fun file)
212 (setq file (locate-library file t))
213 (if (and file (file-readable-p file))
214 (progn
215 (pop-to-buffer (find-file-noselect file))
216 (goto-char (point-min))
217 (if (re-search-forward
218 (format "^[ \t]*(\\(cl-\\)?define-compiler-macro[ \t]+%s"
219 (regexp-quote (symbol-name fun))) nil t)
220 (forward-line 0)
221 (message "Unable to find location in file")))
222 (message "Unable to find file")))
223 'help-echo (purecopy "mouse-2, RET: find function's compiler macro"))
225 (define-button-type 'help-variable-def
226 :supertype 'help-xref
227 'help-function (lambda (var &optional file)
228 (when (eq file 'C-source)
229 (setq file (help-C-file-name var 'var)))
230 (let ((location (find-variable-noselect var file)))
231 (pop-to-buffer (car location))
232 (if (cdr location)
233 (goto-char (cdr location))
234 (message "Unable to find location in file"))))
235 'help-echo (purecopy "mouse-2, RET: find variable's definition"))
237 (define-button-type 'help-face-def
238 :supertype 'help-xref
239 'help-function (lambda (fun file)
240 (require 'find-func)
241 ;; Don't use find-function-noselect because it follows
242 ;; aliases (which fails for built-in functions).
243 (let ((location
244 (find-function-search-for-symbol fun 'defface file)))
245 (pop-to-buffer (car location))
246 (if (cdr location)
247 (goto-char (cdr location))
248 (message "Unable to find location in file"))))
249 'help-echo (purecopy "mouse-2, RET: find face's definition"))
251 (define-button-type 'help-package
252 :supertype 'help-xref
253 'help-function 'describe-package
254 'help-echo (purecopy "mouse-2, RET: Describe package"))
256 (define-button-type 'help-package-def
257 :supertype 'help-xref
258 'help-function (lambda (file) (dired file))
259 'help-echo (purecopy "mouse-2, RET: visit package directory"))
261 (define-button-type 'help-theme-def
262 :supertype 'help-xref
263 'help-function 'find-file
264 'help-echo (purecopy "mouse-2, RET: visit theme file"))
266 (define-button-type 'help-theme-edit
267 :supertype 'help-xref
268 'help-function 'customize-create-theme
269 'help-echo (purecopy "mouse-2, RET: edit this theme file"))
271 (define-button-type 'help-dir-local-var-def
272 :supertype 'help-xref
273 'help-function (lambda (_var &optional file)
274 ;; FIXME: this should go to the point where the
275 ;; local variable was defined.
276 (find-file file))
277 'help-echo (purecopy "mouse-2, RET: open directory-local variables file"))
280 (defvar bookmark-make-record-function)
282 ;;;###autoload
283 (define-derived-mode help-mode special-mode "Help"
284 "Major mode for viewing help text and navigating references in it.
285 Entry to this mode runs the normal hook `help-mode-hook'.
286 Commands:
287 \\{help-mode-map}"
288 (set (make-local-variable 'revert-buffer-function)
289 'help-mode-revert-buffer)
290 (set (make-local-variable 'bookmark-make-record-function)
291 'help-bookmark-make-record))
293 ;;;###autoload
294 (defun help-mode-setup ()
295 (help-mode)
296 (setq buffer-read-only nil))
298 ;;;###autoload
299 (defun help-mode-finish ()
300 (when (derived-mode-p 'help-mode)
301 (setq buffer-read-only t)
302 (help-make-xrefs (current-buffer))))
304 ;; Grokking cross-reference information in doc strings and
305 ;; hyperlinking it.
307 ;; This may have some scope for extension and the same or something
308 ;; similar should be done for widget doc strings, which currently use
309 ;; another mechanism.
311 (defvar help-back-label (purecopy "[back]")
312 "Label to use by `help-make-xrefs' for the go-back reference.")
314 (defvar help-forward-label (purecopy "[forward]")
315 "Label to use by `help-make-xrefs' for the go-forward reference.")
317 (defconst help-xref-symbol-regexp
318 (purecopy (concat "\\(\\<\\(\\(variable\\|option\\)\\|" ; Link to var
319 "\\(function\\|command\\|call\\)\\|" ; Link to function
320 "\\(face\\)\\|" ; Link to face
321 "\\(symbol\\|program\\|property\\)\\|" ; Don't link
322 "\\(source \\(?:code \\)?\\(?:of\\|for\\)\\)\\)"
323 "[ \t\n]+\\)?"
324 ;; Note starting with word-syntax character:
325 "`\\(\\sw\\(\\sw\\|\\s_\\)+\\)'"))
326 "Regexp matching doc string references to symbols.
328 The words preceding the quoted symbol can be used in doc strings to
329 distinguish references to variables, functions and symbols.")
331 (defvar help-xref-mule-regexp nil
332 "Regexp matching doc string references to MULE-related keywords.
334 It is usually nil, and is temporarily bound to an appropriate regexp
335 when help commands related to multilingual environment (e.g.,
336 `describe-coding-system') are invoked.")
339 (defconst help-xref-info-regexp
340 (purecopy "\\<[Ii]nfo[ \t\n]+\\(node\\|anchor\\)[ \t\n]+`\\([^']+\\)'")
341 "Regexp matching doc string references to an Info node.")
343 (defconst help-xref-url-regexp
344 (purecopy "\\<[Uu][Rr][Ll][ \t\n]+`\\([^']+\\)'")
345 "Regexp matching doc string references to a URL.")
347 ;;;###autoload
348 (defun help-setup-xref (item interactive-p)
349 "Invoked from commands using the \"*Help*\" buffer to install some xref info.
351 ITEM is a (FUNCTION . ARGS) pair appropriate for recreating the help
352 buffer after following a reference. INTERACTIVE-P is non-nil if the
353 calling command was invoked interactively. In this case the stack of
354 items for help buffer \"back\" buttons is cleared.
356 This should be called very early, before the output buffer is cleared,
357 because we want to record the \"previous\" position of point so we can
358 restore it properly when going back."
359 (with-current-buffer (help-buffer)
360 (when help-xref-stack-item
361 (push (cons (point) help-xref-stack-item) help-xref-stack)
362 (setq help-xref-forward-stack nil))
363 (when interactive-p
364 (let ((tail (nthcdr 10 help-xref-stack)))
365 ;; Truncate the stack.
366 (if tail (setcdr tail nil))))
367 (setq help-xref-stack-item item)))
369 (defvar help-xref-following nil
370 "Non-nil when following a help cross-reference.")
372 ;;;###autoload
373 (defun help-buffer ()
374 "Return the name of a buffer for inserting help.
375 If `help-xref-following' is non-nil, this is the name of the
376 current buffer. Signal an error if this buffer is not derived
377 from `help-mode'.
378 Otherwise, return \"*Help*\", creating a buffer with that name if
379 it does not already exist."
380 (buffer-name ;for with-output-to-temp-buffer
381 (if (not help-xref-following)
382 (get-buffer-create "*Help*")
383 (unless (derived-mode-p 'help-mode)
384 (error "Current buffer is not in Help mode"))
385 (current-buffer))))
387 ;;;###autoload
388 (defun help-make-xrefs (&optional buffer)
389 "Parse and hyperlink documentation cross-references in the given BUFFER.
391 Find cross-reference information in a buffer and activate such cross
392 references for selection with `help-follow'. Cross-references have
393 the canonical form `...' and the type of reference may be
394 disambiguated by the preceding word(s) used in
395 `help-xref-symbol-regexp'. Faces only get cross-referenced if
396 preceded or followed by the word `face'. Variables without
397 variable documentation do not get cross-referenced, unless
398 preceded by the word `variable' or `option'.
400 If the variable `help-xref-mule-regexp' is non-nil, find also
401 cross-reference information related to multilingual environment
402 \(e.g., coding-systems). This variable is also used to disambiguate
403 the type of reference as the same way as `help-xref-symbol-regexp'.
405 A special reference `back' is made to return back through a stack of
406 help buffers. Variable `help-back-label' specifies the text for
407 that."
408 (interactive "b")
409 (with-current-buffer (or buffer (current-buffer))
410 (save-excursion
411 (goto-char (point-min))
412 ;; Skip the header-type info, though it might be useful to parse
413 ;; it at some stage (e.g. "function in `library'").
414 (forward-paragraph)
415 (let ((old-modified (buffer-modified-p)))
416 (let ((stab (syntax-table))
417 (case-fold-search t)
418 (inhibit-read-only t))
419 (set-syntax-table emacs-lisp-mode-syntax-table)
420 ;; The following should probably be abstracted out.
421 (unwind-protect
422 (progn
423 ;; Info references
424 (save-excursion
425 (while (re-search-forward help-xref-info-regexp nil t)
426 (let ((data (match-string 2)))
427 (save-match-data
428 (unless (string-match "^([^)]+)" data)
429 (setq data (concat "(emacs)" data)))
430 (setq data ;; possible newlines if para filled
431 (replace-regexp-in-string "[ \t\n]+" " " data t t)))
432 (help-xref-button 2 'help-info data))))
433 ;; URLs
434 (save-excursion
435 (while (re-search-forward help-xref-url-regexp nil t)
436 (let ((data (match-string 1)))
437 (help-xref-button 1 'help-url data))))
438 ;; Mule related keywords. Do this before trying
439 ;; `help-xref-symbol-regexp' because some of Mule
440 ;; keywords have variable or function definitions.
441 (if help-xref-mule-regexp
442 (save-excursion
443 (while (re-search-forward help-xref-mule-regexp nil t)
444 (let* ((data (match-string 7))
445 (sym (intern-soft data)))
446 (cond
447 ((match-string 3) ; coding system
448 (and sym (coding-system-p sym)
449 (help-xref-button 6 'help-coding-system sym)))
450 ((match-string 4) ; input method
451 (and (assoc data input-method-alist)
452 (help-xref-button 7 'help-input-method data)))
453 ((or (match-string 5) (match-string 6)) ; charset
454 (and sym (charsetp sym)
455 (help-xref-button 7 'help-character-set sym)))
456 ((assoc data input-method-alist)
457 (help-xref-button 7 'help-character-set data))
458 ((and sym (coding-system-p sym))
459 (help-xref-button 7 'help-coding-system sym))
460 ((and sym (charsetp sym))
461 (help-xref-button 7 'help-character-set sym)))))))
462 ;; Quoted symbols
463 (save-excursion
464 (while (re-search-forward help-xref-symbol-regexp nil t)
465 (let* ((data (match-string 8))
466 (sym (intern-soft data)))
467 (if sym
468 (cond
469 ((match-string 3) ; `variable' &c
470 (and (or (boundp sym) ; `variable' doesn't ensure
471 ; it's actually bound
472 (get sym 'variable-documentation))
473 (help-xref-button 8 'help-variable sym)))
474 ((match-string 4) ; `function' &c
475 (and (fboundp sym) ; similarly
476 (help-xref-button 8 'help-function sym)))
477 ((match-string 5) ; `face'
478 (and (facep sym)
479 (help-xref-button 8 'help-face sym)))
480 ((match-string 6)) ; nothing for `symbol'
481 ((match-string 7)
482 ;; this used:
483 ;; #'(lambda (arg)
484 ;; (let ((location
485 ;; (find-function-noselect arg)))
486 ;; (pop-to-buffer (car location))
487 ;; (goto-char (cdr location))))
488 (help-xref-button 8 'help-function-def sym))
489 ((and
490 (facep sym)
491 (save-match-data (looking-at "[ \t\n]+face\\W")))
492 (help-xref-button 8 'help-face sym))
493 ((and (or (boundp sym)
494 (get sym 'variable-documentation))
495 (fboundp sym))
496 ;; We can't intuit whether to use the
497 ;; variable or function doc -- supply both.
498 (help-xref-button 8 'help-symbol sym))
499 ((and
500 (or (boundp sym)
501 (get sym 'variable-documentation))
503 (documentation-property
504 sym 'variable-documentation)
505 (documentation-property
506 (indirect-variable sym)
507 'variable-documentation)))
508 (help-xref-button 8 'help-variable sym))
509 ((fboundp sym)
510 (help-xref-button 8 'help-function sym)))))))
511 ;; An obvious case of a key substitution:
512 (save-excursion
513 (while (re-search-forward
514 ;; Assume command name is only word and symbol
515 ;; characters to get things like `use M-x foo->bar'.
516 ;; Command required to end with word constituent
517 ;; to avoid `.' at end of a sentence.
518 "\\<M-x\\s-+\\(\\sw\\(\\sw\\|\\s_\\)*\\sw\\)" nil t)
519 (let ((sym (intern-soft (match-string 1))))
520 (if (fboundp sym)
521 (help-xref-button 1 'help-function sym)))))
522 ;; Look for commands in whole keymap substitutions:
523 (save-excursion
524 ;; Make sure to find the first keymap.
525 (goto-char (point-min))
526 ;; Find a header and the column at which the command
527 ;; name will be found.
529 ;; If the keymap substitution isn't the last thing in
530 ;; the doc string, and if there is anything on the same
531 ;; line after it, this code won't recognize the end of it.
532 (while (re-search-forward "^key +binding\n\\(-+ +\\)-+\n\n"
533 nil t)
534 (let ((col (- (match-end 1) (match-beginning 1))))
535 (while
536 (and (not (eobp))
537 ;; Stop at a pair of blank lines.
538 (not (looking-at-p "\n\\s-*\n")))
539 ;; Skip a single blank line.
540 (and (eolp) (forward-line))
541 (end-of-line)
542 (skip-chars-backward "^ \t\n")
543 (if (and (>= (current-column) col)
544 (looking-at "\\(\\sw\\|\\s_\\)+$"))
545 (let ((sym (intern-soft (match-string 0))))
546 (if (fboundp sym)
547 (help-xref-button 0 'help-function sym))))
548 (forward-line))))))
549 (set-syntax-table stab))
550 ;; Delete extraneous newlines at the end of the docstring
551 (goto-char (point-max))
552 (while (and (not (bobp)) (bolp))
553 (delete-char -1))
554 (insert "\n")
555 (when (or help-xref-stack help-xref-forward-stack)
556 (insert "\n"))
557 ;; Make a back-reference in this buffer if appropriate.
558 (when help-xref-stack
559 (help-insert-xref-button help-back-label 'help-back
560 (current-buffer)))
561 ;; Make a forward-reference in this buffer if appropriate.
562 (when help-xref-forward-stack
563 (when help-xref-stack
564 (insert "\t"))
565 (help-insert-xref-button help-forward-label 'help-forward
566 (current-buffer)))
567 (when (or help-xref-stack help-xref-forward-stack)
568 (insert "\n")))
569 (set-buffer-modified-p old-modified)))))
571 ;;;###autoload
572 (defun help-xref-button (match-number type &rest args)
573 "Make a hyperlink for cross-reference text previously matched.
574 MATCH-NUMBER is the subexpression of interest in the last matched
575 regexp. TYPE is the type of button to use. Any remaining arguments are
576 passed to the button's help-function when it is invoked.
577 See `help-make-xrefs'."
578 ;; Don't mung properties we've added specially in some instances.
579 (unless (button-at (match-beginning match-number))
580 (make-text-button (match-beginning match-number)
581 (match-end match-number)
582 'type type 'help-args args)))
584 ;;;###autoload
585 (defun help-insert-xref-button (string type &rest args)
586 "Insert STRING and make a hyperlink from cross-reference text on it.
587 TYPE is the type of button to use. Any remaining arguments are passed
588 to the button's help-function when it is invoked.
589 See `help-make-xrefs'."
590 (unless (button-at (point))
591 (insert-text-button string 'type type 'help-args args)))
593 ;;;###autoload
594 (defun help-xref-on-pp (from to)
595 "Add xrefs for symbols in `pp's output between FROM and TO."
596 (if (> (- to from) 5000) nil
597 (with-syntax-table emacs-lisp-mode-syntax-table
598 (save-excursion
599 (save-restriction
600 (narrow-to-region from to)
601 (goto-char (point-min))
602 (ignore-errors
603 (while (not (eobp))
604 (cond
605 ((looking-at-p "\"") (forward-sexp 1))
606 ((looking-at-p "#<") (search-forward ">" nil 'move))
607 ((looking-at "\\(\\(\\sw\\|\\s_\\)+\\)")
608 (let* ((sym (intern-soft (match-string 1)))
609 (type (cond ((fboundp sym) 'help-function)
610 ((or (memq sym '(t nil))
611 (keywordp sym))
612 nil)
613 ((and sym
614 (or (boundp sym)
615 (get sym
616 'variable-documentation)))
617 'help-variable))))
618 (when type (help-xref-button 1 type sym)))
619 (goto-char (match-end 1)))
620 (t (forward-char 1))))))))))
623 ;; Additional functions for (re-)creating types of help buffers.
624 (defun help-xref-interned (symbol)
625 "Follow a hyperlink which appeared to be an arbitrary interned SYMBOL.
626 Both variable, function and face documentation are extracted into a single
627 help buffer."
628 (with-current-buffer (help-buffer)
629 ;; Push the previous item on the stack before clobbering the output buffer.
630 (help-setup-xref nil nil)
631 (let ((facedoc (when (facep symbol)
632 ;; Don't record the current entry in the stack.
633 (setq help-xref-stack-item nil)
634 (describe-face symbol)))
635 (fdoc (when (fboundp symbol)
636 ;; Don't record the current entry in the stack.
637 (setq help-xref-stack-item nil)
638 (describe-function symbol)))
639 (sdoc (when (or (boundp symbol)
640 (get symbol 'variable-documentation))
641 ;; Don't record the current entry in the stack.
642 (setq help-xref-stack-item nil)
643 (describe-variable symbol))))
644 (cond
645 (sdoc
646 ;; We now have a help buffer on the variable.
647 ;; Insert the function and face text before it.
648 (when (or fdoc facedoc)
649 (goto-char (point-min))
650 (let ((inhibit-read-only t))
651 (when fdoc
652 (insert fdoc "\n\n")
653 (when facedoc
654 (insert (make-string 30 ?-) "\n\n" (symbol-name symbol)
655 " is also a " "face." "\n\n")))
656 (when facedoc
657 (insert facedoc "\n\n"))
658 (insert (make-string 30 ?-) "\n\n" (symbol-name symbol)
659 " is also a " "variable." "\n\n"))
660 ;; Don't record the `describe-variable' item in the stack.
661 (setq help-xref-stack-item nil)
662 (help-setup-xref (list #'help-xref-interned symbol) nil)))
663 (fdoc
664 ;; We now have a help buffer on the function.
665 ;; Insert face text before it.
666 (when facedoc
667 (goto-char (point-max))
668 (let ((inhibit-read-only t))
669 (insert "\n\n" (make-string 30 ?-) "\n\n" (symbol-name symbol)
670 " is also a " "face." "\n\n" facedoc))
671 ;; Don't record the `describe-function' item in the stack.
672 (setq help-xref-stack-item nil)
673 (help-setup-xref (list #'help-xref-interned symbol) nil))))
674 (goto-char (point-min)))))
677 ;; Navigation/hyperlinking with xrefs
679 (defun help-xref-go-back (buffer)
680 "From BUFFER, go back to previous help buffer text using `help-xref-stack'."
681 (let (item position method args)
682 (with-current-buffer buffer
683 (push (cons (point) help-xref-stack-item) help-xref-forward-stack)
684 (when help-xref-stack
685 (setq item (pop help-xref-stack)
686 ;; Clear the current item so that it won't get pushed
687 ;; by the function we're about to call. TODO: We could also
688 ;; push it onto a "forward" stack and add a `forw' button.
689 help-xref-stack-item nil
690 position (car item)
691 method (cadr item)
692 args (cddr item))))
693 (apply method args)
694 (with-current-buffer buffer
695 (if (get-buffer-window buffer)
696 (set-window-point (get-buffer-window buffer) position)
697 (goto-char position)))))
699 (defun help-xref-go-forward (buffer)
700 "From BUFFER, go forward to next help buffer."
701 (let (item position method args)
702 (with-current-buffer buffer
703 (push (cons (point) help-xref-stack-item) help-xref-stack)
704 (when help-xref-forward-stack
705 (setq item (pop help-xref-forward-stack)
706 ;; Clear the current item so that it won't get pushed
707 ;; by the function we're about to call. TODO: We could also
708 ;; push it onto a "forward" stack and add a `forw' button.
709 help-xref-stack-item nil
710 position (car item)
711 method (cadr item)
712 args (cddr item))))
713 (apply method args)
714 (with-current-buffer buffer
715 (if (get-buffer-window buffer)
716 (set-window-point (get-buffer-window buffer) position)
717 (goto-char position)))))
719 (defun help-go-back ()
720 "Go back to previous topic in this help buffer."
721 (interactive)
722 (if help-xref-stack
723 (help-xref-go-back (current-buffer))
724 (error "No previous help buffer")))
726 (defun help-go-forward ()
727 "Go back to next topic in this help buffer."
728 (interactive)
729 (if help-xref-forward-stack
730 (help-xref-go-forward (current-buffer))
731 (error "No next help buffer")))
733 (defun help-do-xref (_pos function args)
734 "Call the help cross-reference function FUNCTION with args ARGS.
735 Things are set up properly so that the resulting help-buffer has
736 a proper [back] button."
737 ;; There is a reference at point. Follow it.
738 (let ((help-xref-following t))
739 (apply function args)))
741 ;; The doc string is meant to explain what buttons do.
742 (defun help-follow-mouse ()
743 "Follow the cross-reference that you click on."
744 (interactive)
745 (error "No cross-reference here"))
747 ;; The doc string is meant to explain what buttons do.
748 (defun help-follow ()
749 "Follow cross-reference at point.
751 For the cross-reference format, see `help-make-xrefs'."
752 (interactive)
753 (error "No cross-reference here"))
755 (defun help-follow-symbol (&optional pos)
756 "In help buffer, show docs for symbol at POS, defaulting to point.
757 Show all docs for that symbol as either a variable, function or face."
758 (interactive "d")
759 (unless pos
760 (setq pos (point)))
761 ;; check if the symbol under point is a function, variable or face
762 (let ((sym
763 (intern
764 (save-excursion
765 (goto-char pos) (skip-syntax-backward "w_")
766 (buffer-substring (point)
767 (progn (skip-syntax-forward "w_")
768 (point)))))))
769 (when (or (boundp sym)
770 (get sym 'variable-documentation)
771 (fboundp sym) (facep sym))
772 (help-do-xref pos #'help-xref-interned (list sym)))))
774 (defun help-mode-revert-buffer (_ignore-auto noconfirm)
775 (when (or noconfirm (yes-or-no-p "Revert help buffer? "))
776 (let ((pos (point))
777 (item help-xref-stack-item)
778 ;; Pretend there is no current item to add to the history.
779 (help-xref-stack-item nil)
780 ;; Use the current buffer.
781 (help-xref-following t))
782 (apply (car item) (cdr item))
783 (goto-char pos))))
785 (defun help-insert-string (string)
786 "Insert STRING to the help buffer and install xref info for it.
787 This function can be used to restore the old contents of the help buffer
788 when going back to the previous topic in the xref stack. It is needed
789 in case when it is impossible to recompute the old contents of the
790 help buffer by other means."
791 (setq help-xref-stack-item (list #'help-insert-string string))
792 (with-output-to-temp-buffer (help-buffer)
793 (insert string)))
796 ;; Bookmark support
798 (declare-function bookmark-prop-get "bookmark" (bookmark prop))
799 (declare-function bookmark-make-record-default "bookmark"
800 (&optional no-file no-context posn))
802 (defun help-bookmark-make-record ()
803 "Create and return a help-mode bookmark record.
804 Implements `bookmark-make-record-function' for help-mode buffers."
805 (unless (car help-xref-stack-item)
806 (error "Cannot create bookmark - help command not known"))
807 `(,@(bookmark-make-record-default 'NO-FILE 'NO-CONTEXT)
808 (help-fn . ,(car help-xref-stack-item))
809 (help-args . ,(cdr help-xref-stack-item))
810 (position . ,(point))
811 (handler . help-bookmark-jump)))
813 ;;;###autoload
814 (defun help-bookmark-jump (bookmark)
815 "Jump to help-mode bookmark BOOKMARK.
816 Handler function for record returned by `help-bookmark-make-record'.
817 BOOKMARK is a bookmark name or a bookmark record."
818 (let ((help-fn (bookmark-prop-get bookmark 'help-fn))
819 (help-args (bookmark-prop-get bookmark 'help-args))
820 (position (bookmark-prop-get bookmark 'position)))
821 (apply help-fn help-args)
822 (pop-to-buffer "*Help*")
823 (goto-char position)))
826 (provide 'help-mode)
828 ;;; help-mode.el ends here