1 ;;; button.el --- clickable buttons
3 ;; Copyright (C) 2001-2012 Free Software Foundation, Inc.
5 ;; Author: Miles Bader <miles@gnu.org>
6 ;; Keywords: extensions
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 3 of the License, or
14 ;; (at your option) 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. If not, see <http://www.gnu.org/licenses/>.
26 ;; This package defines functions for inserting and manipulating
27 ;; clickable buttons in Emacs buffers, such as might be used for help
30 ;; In some ways it duplicates functionality also offered by the
31 ;; `widget' package, but the button package has the advantage that it
32 ;; is (1) much faster, (2) much smaller, and (3) much, much, simpler
33 ;; (the code, that is, not the interface).
35 ;; Buttons can either use overlays, in which case the button is
36 ;; represented by the overlay itself, or text-properties, in which case
37 ;; the button is represented by a marker or buffer-position pointing
38 ;; somewhere in the button. In the latter case, no markers into the
39 ;; buffer are retained, which is important for speed if there are are
40 ;; extremely large numbers of buttons. Note however that if there is
41 ;; an existing face text-property at the site of the button, the
42 ;; button face may not be visible. Using overlays avoids this.
44 ;; Using `define-button-type' to define default properties for buttons
45 ;; is not necessary, but it is encouraged, since doing so makes the
46 ;; resulting code clearer and more efficient.
54 ;; Use color for the MS-DOS port because it doesn't support underline.
55 ;; FIXME if MS-DOS correctly answers the (supports) question, it need
56 ;; no longer be a special case.
57 (defface button '((t :inherit link))
58 "Default face used for buttons."
62 (let ((map (make-sparse-keymap)))
63 ;; The following definition needs to avoid using escape sequences that
64 ;; might get converted to ^M when building loaddefs.el
65 (define-key map [(control ?m)] 'push-button)
66 (define-key map [mouse-2] 'push-button)
67 ;; FIXME: You'd think that for keymaps coming from text-properties on the
68 ;; mode-line or header-line, the `mode-line' or `header-line' prefix
69 ;; shouldn't be necessary!
70 (define-key map [mode-line mouse-2] 'push-button)
71 (define-key map [header-line mouse-2] 'push-button)
73 "Keymap used by buttons.")
75 (defvar button-buffer-map
76 (let ((map (make-sparse-keymap)))
77 (define-key map [?\t] 'forward-button)
78 (define-key map "\e\t" 'backward-button)
79 (define-key map [backtab] 'backward-button)
81 "Keymap useful for buffers containing buttons.
82 Mode-specific keymaps may want to use this as their parent keymap.")
84 ;; Default properties for buttons
85 (put 'default-button 'face 'button)
86 (put 'default-button 'mouse-face 'highlight)
87 (put 'default-button 'keymap button-map)
88 (put 'default-button 'type 'button)
89 ;; action may be either a function to call, or a marker to go to
90 (put 'default-button 'action 'ignore)
91 (put 'default-button 'help-echo (purecopy "mouse-2, RET: Push this button"))
92 ;; Make overlay buttons go away if their underlying text is deleted.
93 (put 'default-button 'evaporate t)
94 ;; Prevent insertions adjacent to the text-property buttons from
95 ;; inheriting its properties.
96 (put 'default-button 'rear-nonsticky t)
98 ;; A `category-symbol' property for the default button type
99 (put 'button 'button-category-symbol 'default-button)
102 ;; Button types (which can be used to hold default properties for buttons)
104 ;; Because button-type properties are inherited by buttons using the
105 ;; special `category' property (implemented by both overlays and
106 ;; text-properties), we need to store them on a symbol to which the
107 ;; `category' properties can point. Instead of using the symbol that's
108 ;; the name of each button-type, however, we use a separate symbol (with
109 ;; `-button' appended, and uninterned) to store the properties. This is
110 ;; to avoid name clashes.
112 ;; [this is an internal function]
113 (defsubst button-category-symbol (type)
114 "Return the symbol used by button-type TYPE to store properties.
115 Buttons inherit them by setting their `category' property to that symbol."
116 (or (get type 'button-category-symbol)
117 (error "Unknown button type `%s'" type)))
119 (defun define-button-type (name &rest properties)
120 "Define a `button type' called NAME (a symbol).
121 The remaining arguments form a sequence of PROPERTY VALUE pairs,
122 specifying properties to use as defaults for buttons with this type
123 \(a button's type may be set by giving it a `type' property when
124 creating the button, using the :type keyword argument).
126 In addition, the keyword argument :supertype may be used to specify a
127 button-type from which NAME inherits its default property values
128 \(however, the inheritance happens only when NAME is defined; subsequent
129 changes to a supertype are not reflected in its subtypes)."
130 (let ((catsym (make-symbol (concat (symbol-name name) "-button")))
132 (button-category-symbol
133 (or (plist-get properties 'supertype)
134 (plist-get properties :supertype)
136 ;; Provide a link so that it's easy to find the real symbol.
137 (put name 'button-category-symbol catsym)
138 ;; Initialize NAME's properties using the global defaults.
139 (let ((default-props (symbol-plist super-catsym)))
141 (put catsym (pop default-props) (pop default-props))))
142 ;; Add NAME as the `type' property, which will then be returned as
143 ;; the type property of individual buttons.
144 (put catsym 'type name)
145 ;; Add the properties in PROPERTIES to the real symbol.
147 (let ((prop (pop properties)))
148 (when (eq prop :supertype)
149 (setq prop 'supertype))
150 (put catsym prop (pop properties))))
151 ;; Make sure there's a `supertype' property
152 (unless (get catsym 'supertype)
153 (put catsym 'supertype 'button))
156 (defun button-type-put (type prop val)
157 "Set the button-type TYPE's PROP property to VAL."
158 (put (button-category-symbol type) prop val))
160 (defun button-type-get (type prop)
161 "Get the property of button-type TYPE named PROP."
162 (get (button-category-symbol type) prop))
164 (defun button-type-subtype-p (type supertype)
165 "Return t if button-type TYPE is a subtype of SUPERTYPE."
166 (or (eq type supertype)
168 (button-type-subtype-p (button-type-get type 'supertype)
172 ;; Button properties and other attributes
174 (defun button-start (button)
175 "Return the position at which BUTTON starts."
176 (if (overlayp button)
177 (overlay-start button)
178 ;; Must be a text-property button.
179 (or (previous-single-property-change (1+ button) 'button)
182 (defun button-end (button)
183 "Return the position at which BUTTON ends."
184 (if (overlayp button)
186 ;; Must be a text-property button.
187 (or (next-single-property-change button 'button)
190 (defun button-get (button prop)
191 "Get the property of button BUTTON named PROP."
192 (cond ((overlayp button)
193 (overlay-get button prop))
194 ((button--area-button-p button)
195 (get-text-property 0 prop (button--area-button-string button)))
196 (t ; Must be a text-property button.
197 (get-text-property button prop))))
199 (defun button-put (button prop val)
200 "Set BUTTON's PROP property to VAL."
201 ;; Treat some properties specially.
202 (cond ((memq prop '(type :type))
203 ;; We translate a `type' property a `category' property, since
204 ;; that's what's actually used by overlays/text-properties for
205 ;; inheriting properties.
206 (setq prop 'category)
207 (setq val (button-category-symbol val)))
209 ;; Disallow updating the `category' property directly.
210 (error "Button `category' property may not be set directly")))
212 (cond ((overlayp button)
213 (overlay-put button prop val))
214 ((button--area-button-p button)
215 (setq button (button--area-button-string button))
216 (put-text-property 0 (length button) prop val button))
217 (t ; Must be a text-property button.
219 (or (previous-single-property-change (1+ button) 'button)
221 (or (next-single-property-change button 'button)
225 (defun button-activate (button &optional use-mouse-action)
226 "Call BUTTON's action property.
227 If USE-MOUSE-ACTION is non-nil, invoke the button's mouse-action
228 instead of its normal action; if the button has no mouse-action,
229 the normal action is used instead.
231 The action can either be a marker or a function. If it's a
232 marker then goto it. Otherwise it it is a function then it is
233 called with BUTTON as only argument. BUTTON is either an
234 overlay, a buffer position, or (for buttons in the mode-line or
235 header-line) a string."
236 (let ((action (or (and use-mouse-action (button-get button 'mouse-action))
237 (button-get button 'action))))
239 (save-selected-window
240 (select-window (display-buffer (marker-buffer action)))
243 (funcall action button))))
245 (defun button-label (button)
246 "Return BUTTON's text label."
247 (if (button--area-button-p button)
248 (substring-no-properties (button--area-button-string button))
249 (buffer-substring-no-properties (button-start button)
250 (button-end button))))
252 (defsubst button-type (button)
253 "Return BUTTON's button-type."
254 (button-get button 'type))
256 (defun button-has-type-p (button type)
257 "Return t if BUTTON has button-type TYPE, or one of TYPE's subtypes."
258 (button-type-subtype-p (button-get button 'type) type))
260 (defalias 'button--area-button-p 'stringp
261 "Return non-nil if BUTTON is an area button.
262 Such area buttons are used for buttons in the mode-line and header-line.")
264 (defalias 'button--area-button-string 'identity
265 "Return area button BUTTON's button-string.")
267 ;; Creating overlay buttons
269 (defun make-button (beg end &rest properties)
270 "Make a button from BEG to END in the current buffer.
271 The remaining arguments form a sequence of PROPERTY VALUE pairs,
272 specifying properties to add to the button.
273 In addition, the keyword argument :type may be used to specify a
274 button-type from which to inherit other properties; see
275 `define-button-type'.
277 Also see `make-text-button', `insert-button'."
278 (let ((overlay (make-overlay beg end nil t nil)))
280 (button-put overlay (pop properties) (pop properties)))
281 ;; Put a pointer to the button in the overlay, so it's easy to get
282 ;; when we don't actually have a reference to the overlay.
283 (overlay-put overlay 'button overlay)
284 ;; If the user didn't specify a type, use the default.
285 (unless (overlay-get overlay 'category)
286 (overlay-put overlay 'category 'default-button))
287 ;; OVERLAY is the button, so return it
290 (defun insert-button (label &rest properties)
291 "Insert a button with the label LABEL.
292 The remaining arguments form a sequence of PROPERTY VALUE pairs,
293 specifying properties to add to the button.
294 In addition, the keyword argument :type may be used to specify a
295 button-type from which to inherit other properties; see
296 `define-button-type'.
298 Also see `insert-text-button', `make-button'."
300 (prog1 (point) (insert label))
305 ;; Creating text-property buttons
307 (defun make-text-button (beg end &rest properties)
308 "Make a button from BEG to END in the current buffer.
309 The remaining arguments form a sequence of PROPERTY VALUE pairs,
310 specifying properties to add to the button.
311 In addition, the keyword argument :type may be used to specify a
312 button-type from which to inherit other properties; see
313 `define-button-type'.
315 This function is like `make-button', except that the button is actually
316 part of the text instead of being a property of the buffer. That is,
317 this function uses text properties, the other uses overlays.
318 Creating large numbers of buttons can also be somewhat faster
319 using `make-text-button'. Note, however, that if there is an existing
320 face property at the site of the button, the button face may not be visible.
321 You may want to use `make-button' in that case.
323 BEG can also be a string, in which case it is made into a button.
325 Also see `insert-text-button'."
328 (or (plist-member properties 'type)
329 (plist-member properties :type))))
331 (setq object beg beg 0 end (length object)))
332 ;; Disallow setting the `category' property directly.
333 (when (plist-get properties 'category)
334 (error "Button `category' property may not be set directly"))
335 (if (null type-entry)
336 ;; The user didn't specify a `type' property, use the default.
337 (setq properties (cons 'category (cons 'default-button properties)))
338 ;; The user did specify a `type' property. Translate it into a
339 ;; `category' property, which is what's actually used by
340 ;; text-properties for inheritance.
341 (setcar type-entry 'category)
342 (setcar (cdr type-entry)
343 (button-category-symbol (car (cdr type-entry)))))
344 ;; Now add all the text properties at once
345 (add-text-properties beg end
346 ;; Each button should have a non-eq `button'
347 ;; property so that next-single-property-change can
348 ;; detect boundaries reliably.
349 (cons 'button (cons (list t) properties))
351 ;; Return something that can be used to get at the button.
354 (defun insert-text-button (label &rest properties)
355 "Insert a button with the label LABEL.
356 The remaining arguments form a sequence of PROPERTY VALUE pairs,
357 specifying properties to add to the button.
358 In addition, the keyword argument :type may be used to specify a
359 button-type from which to inherit other properties; see
360 `define-button-type'.
362 This function is like `insert-button', except that the button is
363 actually part of the text instead of being a property of the buffer.
364 Creating large numbers of buttons can also be somewhat faster using
365 `insert-text-button'.
367 Also see `make-text-button'."
368 (apply #'make-text-button
369 (prog1 (point) (insert label))
374 ;; Finding buttons in a buffer
376 (defun button-at (pos)
377 "Return the button at position POS in the current buffer, or nil.
378 If the button at POS is a text property button, the return value
379 is a marker pointing to POS."
380 (let ((button (get-char-property pos 'button)))
381 (if (or (overlayp button) (null button))
383 ;; Must be a text-property button; return a marker pointing to it.
384 (copy-marker pos t))))
386 (defun next-button (pos &optional count-current)
387 "Return the next button after position POS in the current buffer.
388 If COUNT-CURRENT is non-nil, count any button at POS in the search,
389 instead of starting at the next button."
390 (unless count-current
391 ;; Search for the next button boundary.
392 (setq pos (next-single-char-property-change pos 'button)))
393 (and (< pos (point-max))
395 ;; We must have originally been on a button, and are now in
396 ;; the inter-button space. Recurse to find a button.
399 (defun previous-button (pos &optional count-current)
400 "Return the previous button before position POS in the current buffer.
401 If COUNT-CURRENT is non-nil, count any button at POS in the search,
402 instead of starting at the next button."
403 (let ((button (button-at pos)))
407 ;; We started out on a button, so move to its start and look
408 ;; for the previous button boundary.
409 (setq pos (previous-single-char-property-change
410 (button-start button) 'button))
411 (let ((new-button (button-at pos)))
413 ;; We are in a button again; this can happen if there
414 ;; are adjacent buttons (or at bob).
415 (unless (= pos (button-start button)) new-button)
416 ;; We are now in the space between buttons.
417 (previous-button pos))))
418 ;; We started out in the space between buttons.
419 (setq pos (previous-single-char-property-change pos 'button))
421 (and (> pos (point-min))
422 (button-at (1- pos)))))))
427 (defun push-button (&optional pos use-mouse-action)
428 "Perform the action specified by a button at location POS.
429 POS may be either a buffer position or a mouse-event. If
430 USE-MOUSE-ACTION is non-nil, invoke the button's mouse-action
431 instead of its normal action; if the button has no mouse-action,
432 the normal action is used instead. The action may be either a
433 function to call or a marker to display and is invoked using
434 `button-activate' (which see).
436 POS defaults to point, except when `push-button' is invoked
437 interactively as the result of a mouse-event, in which case, the
439 If there's no button at POS, do nothing and return nil, otherwise
442 (list (if (integerp last-command-event) (point) last-command-event)))
443 (if (and (not (integerp pos)) (eventp pos))
444 ;; POS is a mouse event; switch to the proper window/buffer
445 (let ((posn (event-start pos)))
446 (with-current-buffer (window-buffer (posn-window posn))
448 ;; mode-line or header-line event
449 (button-activate (car (posn-string posn)) t)
450 (push-button (posn-point posn)) t)))
451 ;; POS is just normal position
452 (let ((button (button-at (or pos (point)))))
454 (button-activate button use-mouse-action)
457 (defun forward-button (n &optional wrap display-message)
458 "Move to the Nth next button, or Nth previous button if N is negative.
459 If N is 0, move to the start of any button at point.
460 If WRAP is non-nil, moving past either end of the buffer continues from the
462 If DISPLAY-MESSAGE is non-nil, the button's help-echo string is displayed.
463 Any button with a non-nil `skip' property is skipped over.
464 Returns the button found."
465 (interactive "p\nd\nd")
468 ;; Move to start of current button
469 (if (setq button (button-at (point)))
470 (goto-char (button-start button)))
471 ;; Move to Nth next button
472 (let ((iterator (if (> n 0) #'next-button #'previous-button))
473 (wrap-start (if (> n 0) (point-min) (point-max)))
476 (setq button t) ; just to start the loop
477 (while (and (null fail) (> n 0) button)
478 (setq button (funcall iterator (point)))
479 (when (and (not button) wrap)
480 (setq button (funcall iterator wrap-start t)))
482 (goto-char (button-start button))
483 ;; Avoid looping forever (e.g., if all the buttons have
484 ;; the `skip' property).
486 (setq opoint (point)))
489 (unless (button-get button 'skip)
492 (error (if wrap "No buttons!" "No more buttons"))
493 (let ((msg (and display-message (button-get button 'help-echo))))
498 (defun backward-button (n &optional wrap display-message)
499 "Move to the Nth previous button, or Nth next button if N is negative.
500 If N is 0, move to the start of any button at point.
501 If WRAP is non-nil, moving past either end of the buffer continues from the
503 If DISPLAY-MESSAGE is non-nil, the button's help-echo string is displayed.
504 Any button with a non-nil `skip' property is skipped over.
505 Returns the button found."
506 (interactive "p\nd\nd")
507 (forward-button (- n) wrap display-message))
512 ;;; button.el ends here