lisp/button.el

   1 ;;; button.el --- clickable buttons
   2 ;;
   3 ;; Copyright (C) 2001-2012  Free Software Foundation, Inc.
   4 ;;
   5 ;; Author: Miles Bader <miles@gnu.org>
   6 ;; Keywords: extensions
   7 ;; Package: emacs
   8 ;;
   9 ;; This file is part of GNU Emacs.
  10 ;;
  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.
  15
  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.
  20
  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/>.
  23
  24 ;;; Commentary:
  25 ;;
  26 ;; This package defines functions for inserting and manipulating
  27 ;; clickable buttons in Emacs buffers, such as might be used for help
  28 ;; hyperlinks, etc.
  29 ;;
  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).
  34 ;;
  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.
  43 ;;
  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.
  47 ;;
  48
  49 ;;; Code:
  50
  51 \f
  52 ;; Globals
  53
  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."
  59   :group 'basic-faces)
  60
  61 (defvar button-map
  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     map)
  68   "Keymap used by buttons.")
  69
  70 (defvar button-buffer-map
  71   (let ((map (make-sparse-keymap)))
  72     (define-key map [?\t] 'forward-button)
  73     (define-key map "\e\t" 'backward-button)
  74     (define-key map [backtab] 'backward-button)
  75     map)
  76   "Keymap useful for buffers containing buttons.
  77 Mode-specific keymaps may want to use this as their parent keymap.")
  78
  79 ;; Default properties for buttons
  80 (put 'default-button 'face 'button)
  81 (put 'default-button 'mouse-face 'highlight)
  82 (put 'default-button 'keymap button-map)
  83 (put 'default-button 'type 'button)
  84 ;; action may be either a function to call, or a marker to go to
  85 (put 'default-button 'action 'ignore)
  86 (put 'default-button 'help-echo (purecopy "mouse-2, RET: Push this button"))
  87 ;; Make overlay buttons go away if their underlying text is deleted.
  88 (put 'default-button 'evaporate t)
  89 ;; Prevent insertions adjacent to the text-property buttons from
  90 ;; inheriting its properties.
  91 (put 'default-button 'rear-nonsticky t)
  92
  93 ;; A `category-symbol' property for the default button type
  94 (put 'button 'button-category-symbol 'default-button)
  95
  96 \f
  97 ;; Button types (which can be used to hold default properties for buttons)
  98
  99 ;; Because button-type properties are inherited by buttons using the
 100 ;; special `category' property (implemented by both overlays and
 101 ;; text-properties), we need to store them on a symbol to which the
 102 ;; `category' properties can point.  Instead of using the symbol that's
 103 ;; the name of each button-type, however, we use a separate symbol (with
 104 ;; `-button' appended, and uninterned) to store the properties.  This is
 105 ;; to avoid name clashes.
 106
 107 ;; [this is an internal function]
 108 (defsubst button-category-symbol (type)
 109   "Return the symbol used by button-type TYPE to store properties.
 110 Buttons inherit them by setting their `category' property to that symbol."
 111   (or (get type 'button-category-symbol)
 112       (error "Unknown button type `%s'" type)))
 113
 114 (defun define-button-type (name &rest properties)
 115   "Define a `button type' called NAME (a symbol).
 116 The remaining arguments form a sequence of PROPERTY VALUE pairs,
 117 specifying properties to use as defaults for buttons with this type
 118 \(a button's type may be set by giving it a `type' property when
 119 creating the button, using the :type keyword argument).
 120
 121 In addition, the keyword argument :supertype may be used to specify a
 122 button-type from which NAME inherits its default property values
 123 \(however, the inheritance happens only when NAME is defined; subsequent
 124 changes to a supertype are not reflected in its subtypes)."
 125   (let ((catsym (make-symbol (concat (symbol-name name) "-button")))
 126         (super-catsym
 127          (button-category-symbol
 128           (or (plist-get properties 'supertype)
 129               (plist-get properties :supertype)
 130               'button))))
 131     ;; Provide a link so that it's easy to find the real symbol.
 132     (put name 'button-category-symbol catsym)
 133     ;; Initialize NAME's properties using the global defaults.
 134     (let ((default-props (symbol-plist super-catsym)))
 135       (while default-props
 136         (put catsym (pop default-props) (pop default-props))))
 137     ;; Add NAME as the `type' property, which will then be returned as
 138     ;; the type property of individual buttons.
 139     (put catsym 'type name)
 140     ;; Add the properties in PROPERTIES to the real symbol.
 141     (while properties
 142       (let ((prop (pop properties)))
 143         (when (eq prop :supertype)
 144           (setq prop 'supertype))
 145         (put catsym prop (pop properties))))
 146     ;; Make sure there's a `supertype' property
 147     (unless (get catsym 'supertype)
 148       (put catsym 'supertype 'button))
 149     name))
 150
 151 (defun button-type-put (type prop val)
 152   "Set the button-type TYPE's PROP property to VAL."
 153   (put (button-category-symbol type) prop val))
 154
 155 (defun button-type-get (type prop)
 156   "Get the property of button-type TYPE named PROP."
 157   (get (button-category-symbol type) prop))
 158
 159 (defun button-type-subtype-p (type supertype)
 160   "Return t if button-type TYPE is a subtype of SUPERTYPE."
 161   (or (eq type supertype)
 162       (and type
 163            (button-type-subtype-p (button-type-get type 'supertype)
 164                                   supertype))))
 165
 166 \f
 167 ;; Button properties and other attributes
 168
 169 (defun button-start (button)
 170   "Return the position at which BUTTON starts."
 171   (if (overlayp button)
 172       (overlay-start button)
 173     ;; Must be a text-property button.
 174     (or (previous-single-property-change (1+ button) 'button)
 175         (point-min))))
 176
 177 (defun button-end (button)
 178   "Return the position at which BUTTON ends."
 179   (if (overlayp button)
 180       (overlay-end button)
 181     ;; Must be a text-property button.
 182     (or (next-single-property-change button 'button)
 183         (point-max))))
 184
 185 (defun button-get (button prop)
 186   "Get the property of button BUTTON named PROP."
 187   (if (overlayp button)
 188       (overlay-get button prop)
 189     ;; Must be a text-property button.
 190     (get-text-property button prop)))
 191
 192 (defun button-put (button prop val)
 193   "Set BUTTON's PROP property to VAL."
 194   ;; Treat some properties specially.
 195   (cond ((memq prop '(type :type))
 196          ;; We translate a `type' property a `category' property, since
 197          ;; that's what's actually used by overlays/text-properties for
 198          ;; inheriting properties.
 199          (setq prop 'category)
 200          (setq val (button-category-symbol val)))
 201         ((eq prop 'category)
 202          ;; Disallow updating the `category' property directly.
 203          (error "Button `category' property may not be set directly")))
 204   ;; Add the property.
 205   (if (overlayp button)
 206       (overlay-put button prop val)
 207     ;; Must be a text-property button.
 208     (put-text-property
 209      (or (previous-single-property-change (1+ button) 'button)
 210          (point-min))
 211      (or (next-single-property-change button 'button)
 212          (point-max))
 213      prop val)))
 214
 215 (defsubst button-activate (button &optional use-mouse-action)
 216   "Call BUTTON's action property.
 217 If USE-MOUSE-ACTION is non-nil, invoke the button's mouse-action
 218 instead of its normal action; if the button has no mouse-action,
 219 the normal action is used instead."
 220   (let ((action (or (and use-mouse-action (button-get button 'mouse-action))
 221                     (button-get button 'action))))
 222     (if (markerp action)
 223         (save-selected-window
 224           (select-window (display-buffer (marker-buffer action)))
 225           (goto-char action)
 226           (recenter 0))
 227       (funcall action button))))
 228
 229 (defun button-label (button)
 230   "Return BUTTON's text label."
 231   (buffer-substring-no-properties (button-start button) (button-end button)))
 232
 233 (defsubst button-type (button)
 234   "Return BUTTON's button-type."
 235   (button-get button 'type))
 236
 237 (defun button-has-type-p (button type)
 238   "Return t if BUTTON has button-type TYPE, or one of TYPE's subtypes."
 239   (button-type-subtype-p (button-get button 'type) type))
 240
 241 \f
 242 ;; Creating overlay buttons
 243
 244 (defun make-button (beg end &rest properties)
 245   "Make a button from BEG to END in the current buffer.
 246 The remaining arguments form a sequence of PROPERTY VALUE pairs,
 247 specifying properties to add to the button.
 248 In addition, the keyword argument :type may be used to specify a
 249 button-type from which to inherit other properties; see
 250 `define-button-type'.
 251
 252 Also see `make-text-button', `insert-button'."
 253   (let ((overlay (make-overlay beg end nil t nil)))
 254     (while properties
 255       (button-put overlay (pop properties) (pop properties)))
 256     ;; Put a pointer to the button in the overlay, so it's easy to get
 257     ;; when we don't actually have a reference to the overlay.
 258     (overlay-put overlay 'button overlay)
 259     ;; If the user didn't specify a type, use the default.
 260     (unless (overlay-get overlay 'category)
 261       (overlay-put overlay 'category 'default-button))
 262     ;; OVERLAY is the button, so return it
 263     overlay))
 264
 265 (defun insert-button (label &rest properties)
 266   "Insert a button with the label LABEL.
 267 The remaining arguments form a sequence of PROPERTY VALUE pairs,
 268 specifying properties to add to the button.
 269 In addition, the keyword argument :type may be used to specify a
 270 button-type from which to inherit other properties; see
 271 `define-button-type'.
 272
 273 Also see `insert-text-button', `make-button'."
 274   (apply #'make-button
 275          (prog1 (point) (insert label))
 276          (point)
 277          properties))
 278
 279 \f
 280 ;; Creating text-property buttons
 281
 282 (defun make-text-button (beg end &rest properties)
 283   "Make a button from BEG to END in the current buffer.
 284 The remaining arguments form a sequence of PROPERTY VALUE pairs,
 285 specifying properties to add to the button.
 286 In addition, the keyword argument :type may be used to specify a
 287 button-type from which to inherit other properties; see
 288 `define-button-type'.
 289
 290 This function is like `make-button', except that the button is actually
 291 part of the text instead of being a property of the buffer.  That is,
 292 this function uses text properties, the other uses overlays.
 293 Creating large numbers of buttons can also be somewhat faster
 294 using `make-text-button'.  Note, however, that if there is an existing
 295 face property at the site of the button, the button face may not be visible.
 296 You may want to use `make-button' in that case.
 297
 298 BEG can also be a string, in which case it is made into a button.
 299
 300 Also see `insert-text-button'."
 301   (let ((object nil)
 302         (type-entry
 303          (or (plist-member properties 'type)
 304              (plist-member properties :type))))
 305     (when (stringp beg)
 306       (setq object beg beg 0 end (length object)))
 307     ;; Disallow setting the `category' property directly.
 308     (when (plist-get properties 'category)
 309       (error "Button `category' property may not be set directly"))
 310     (if (null type-entry)
 311         ;; The user didn't specify a `type' property, use the default.
 312         (setq properties (cons 'category (cons 'default-button properties)))
 313       ;; The user did specify a `type' property.  Translate it into a
 314       ;; `category' property, which is what's actually used by
 315       ;; text-properties for inheritance.
 316       (setcar type-entry 'category)
 317       (setcar (cdr type-entry)
 318               (button-category-symbol (car (cdr type-entry)))))
 319     ;; Now add all the text properties at once
 320     (add-text-properties beg end
 321                          ;; Each button should have a non-eq `button'
 322                          ;; property so that next-single-property-change can
 323                          ;; detect boundaries reliably.
 324                          (cons 'button (cons (list t) properties))
 325                          object)
 326     ;; Return something that can be used to get at the button.
 327     beg))
 328
 329 (defun insert-text-button (label &rest properties)
 330   "Insert a button with the label LABEL.
 331 The remaining arguments form a sequence of PROPERTY VALUE pairs,
 332 specifying properties to add to the button.
 333 In addition, the keyword argument :type may be used to specify a
 334 button-type from which to inherit other properties; see
 335 `define-button-type'.
 336
 337 This function is like `insert-button', except that the button is
 338 actually part of the text instead of being a property of the buffer.
 339 Creating large numbers of buttons can also be somewhat faster using
 340 `insert-text-button'.
 341
 342 Also see `make-text-button'."
 343   (apply #'make-text-button
 344          (prog1 (point) (insert label))
 345          (point)
 346          properties))
 347
 348 \f
 349 ;; Finding buttons in a buffer
 350
 351 (defun button-at (pos)
 352   "Return the button at position POS in the current buffer, or nil."
 353   (let ((button (get-char-property pos 'button)))
 354     (if (or (overlayp button) (null button))
 355         button
 356       ;; Must be a text-property button; return a marker pointing to it.
 357       (copy-marker pos t))))
 358
 359 (defun next-button (pos &optional count-current)
 360   "Return the next button after position POS in the current buffer.
 361 If COUNT-CURRENT is non-nil, count any button at POS in the search,
 362 instead of starting at the next button."
 363     (unless count-current
 364       ;; Search for the next button boundary.
 365       (setq pos (next-single-char-property-change pos 'button)))
 366     (and (< pos (point-max))
 367          (or (button-at pos)
 368              ;; We must have originally been on a button, and are now in
 369              ;; the inter-button space.  Recurse to find a button.
 370              (next-button pos))))
 371
 372 (defun previous-button (pos &optional count-current)
 373   "Return the previous button before position POS in the current buffer.
 374 If COUNT-CURRENT is non-nil, count any button at POS in the search,
 375 instead of starting at the next button."
 376   (let ((button (button-at pos)))
 377     (if button
 378         (if count-current
 379             button
 380           ;; We started out on a button, so move to its start and look
 381           ;; for the previous button boundary.
 382           (setq pos (previous-single-char-property-change
 383                      (button-start button) 'button))
 384           (let ((new-button (button-at pos)))
 385             (if new-button
 386                 ;; We are in a button again; this can happen if there
 387                 ;; are adjacent buttons (or at bob).
 388                 (unless (= pos (button-start button)) new-button)
 389               ;; We are now in the space between buttons.
 390               (previous-button pos))))
 391       ;; We started out in the space between buttons.
 392       (setq pos (previous-single-char-property-change pos 'button))
 393       (or (button-at pos)
 394           (and (> pos (point-min))
 395                (button-at (1- pos)))))))
 396
 397 \f
 398 ;; User commands
 399
 400 (defun push-button (&optional pos use-mouse-action)
 401   "Perform the action specified by a button at location POS.
 402 POS may be either a buffer position or a mouse-event.  If
 403 USE-MOUSE-ACTION is non-nil, invoke the button's mouse-action
 404 instead of its normal action; if the button has no mouse-action,
 405 the normal action is used instead.  The action may be either a
 406 function to call or a marker to display.
 407 POS defaults to point, except when `push-button' is invoked
 408 interactively as the result of a mouse-event, in which case, the
 409 mouse event is used.
 410 If there's no button at POS, do nothing and return nil, otherwise
 411 return t."
 412   (interactive
 413    (list (if (integerp last-command-event) (point) last-command-event)))
 414   (if (and (not (integerp pos)) (eventp pos))
 415       ;; POS is a mouse event; switch to the proper window/buffer
 416       (let ((posn (event-start pos)))
 417         (with-current-buffer (window-buffer (posn-window posn))
 418           (push-button (posn-point posn) t)))
 419     ;; POS is just normal position
 420     (let ((button (button-at (or pos (point)))))
 421       (if (not button)
 422           nil
 423         (button-activate button use-mouse-action)
 424         t))))
 425
 426 (defun forward-button (n &optional wrap display-message)
 427   "Move to the Nth next button, or Nth previous button if N is negative.
 428 If N is 0, move to the start of any button at point.
 429 If WRAP is non-nil, moving past either end of the buffer continues from the
 430 other end.
 431 If DISPLAY-MESSAGE is non-nil, the button's help-echo string is displayed.
 432 Any button with a non-nil `skip' property is skipped over.
 433 Returns the button found."
 434   (interactive "p\nd\nd")
 435   (let (button)
 436     (if (zerop n)
 437         ;; Move to start of current button
 438         (if (setq button (button-at (point)))
 439             (goto-char (button-start button)))
 440       ;; Move to Nth next button
 441       (let ((iterator (if (> n 0) #'next-button #'previous-button))
 442             (wrap-start (if (> n 0) (point-min) (point-max)))
 443             opoint fail)
 444         (setq n (abs n))
 445         (setq button t)                 ; just to start the loop
 446         (while (and (null fail) (> n 0) button)
 447           (setq button (funcall iterator (point)))
 448           (when (and (not button) wrap)
 449             (setq button (funcall iterator wrap-start t)))
 450           (when button
 451             (goto-char (button-start button))
 452             ;; Avoid looping forever (e.g., if all the buttons have
 453             ;; the `skip' property).
 454             (cond ((null opoint)
 455                    (setq opoint (point)))
 456                   ((= opoint (point))
 457                    (setq fail t)))
 458             (unless (button-get button 'skip)
 459               (setq n (1- n)))))))
 460     (if (null button)
 461         (error (if wrap "No buttons!" "No more buttons"))
 462       (let ((msg (and display-message (button-get button 'help-echo))))
 463         (when msg
 464           (message "%s" msg)))
 465       button)))
 466
 467 (defun backward-button (n &optional wrap display-message)
 468   "Move to the Nth previous button, or Nth next button if N is negative.
 469 If N is 0, move to the start of any button at point.
 470 If WRAP is non-nil, moving past either end of the buffer continues from the
 471 other end.
 472 If DISPLAY-MESSAGE is non-nil, the button's help-echo string is displayed.
 473 Any button with a non-nil `skip' property is skipped over.
 474 Returns the button found."
 475   (interactive "p\nd\nd")
 476   (forward-button (- n) wrap display-message))
 477
 478
 479 (provide 'button)
 480
 481 ;;; button.el ends here