lisp/button.el

   1 ;;; button.el --- clickable buttons
   2 ;;
   3 ;; Copyright (C) 2001, 2002, 2003, 2004, 2005,
   4 ;;   2006, 2007, 2008 Free Software Foundation, Inc.
   5 ;;
   6 ;; Author: Miles Bader <miles@gnu.org>
   7 ;; Keywords: extensions
   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, or (at your option)
  14 ;; 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; see the file COPYING.  If not, write to the
  23 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  24 ;; Boston, MA 02110-1301, USA.
  25
  26 ;;; Commentary:
  27 ;;
  28 ;; This package defines functions for inserting and manipulating
  29 ;; clickable buttons in Emacs buffers, such as might be used for help
  30 ;; hyperlinks, etc.
  31 ;;
  32 ;; In some ways it duplicates functionality also offered by the
  33 ;; `widget' package, but the button package has the advantage that it
  34 ;; is (1) much faster, (2) much smaller, and (3) much, much, simpler
  35 ;; (the code, that is, not the interface).
  36 ;;
  37 ;; Buttons can either use overlays, in which case the button is
  38 ;; represented by the overlay itself, or text-properties, in which case
  39 ;; the button is represented by a marker or buffer-position pointing
  40 ;; somewhere in the button.  In the latter case, no markers into the
  41 ;; buffer are retained, which is important for speed if there are are
  42 ;; extremely large numbers of buttons.
  43 ;;
  44 ;; Using `define-button-type' to define default properties for buttons
  45 ;; is not necessary, but it is 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 '((((type pc) (class color))
  58                    (:foreground "lightblue"))
  59                   (((supports :underline t)) :underline t)
  60                   (t (:foreground "lightblue")))
  61   "Default face used for buttons."
  62   :group 'basic-faces)
  63
  64 ;;;###autoload
  65 (defvar button-map
  66   (let ((map (make-sparse-keymap)))
  67     (define-key map "\r" 'push-button)
  68     (define-key map [mouse-2] 'push-button)
  69     map)
  70   "Keymap used by buttons.")
  71
  72 ;;;###autoload
  73 (defvar button-buffer-map
  74   (let ((map (make-sparse-keymap)))
  75     (define-key map [?\t] 'forward-button)
  76     (define-key map "\e\t" 'backward-button)
  77     (define-key map [backtab] 'backward-button)
  78     map)
  79   "Keymap useful for buffers containing buttons.
  80 Mode-specific keymaps may want to use this as their parent keymap.")
  81
  82 ;; Default properties for buttons
  83 (put 'default-button 'face 'button)
  84 (put 'default-button 'mouse-face 'highlight)
  85 (put 'default-button 'keymap button-map)
  86 (put 'default-button 'type 'button)
  87 ;; action may be either a function to call, or a marker to go to
  88 (put 'default-button 'action 'ignore)
  89 (put 'default-button 'help-echo "mouse-2, RET: Push this button")
  90 ;; Make overlay buttons go away if their underlying text is deleted.
  91 (put 'default-button 'evaporate t)
  92 ;; Prevent insertions adjacent to the text-property buttons from
  93 ;; inheriting its properties.
  94 (put 'default-button 'rear-nonsticky t)
  95
  96 ;; A `category-symbol' property for the default button type
  97 (put 'button 'button-category-symbol 'default-button)
  98
  99 \f
 100 ;; Button types (which can be used to hold default properties for buttons)
 101
 102 ;; Because button-type properties are inherited by buttons using the
 103 ;; special `category' property (implemented by both overlays and
 104 ;; text-properties), we need to store them on a symbol to which the
 105 ;; `category' properties can point.  Instead of using the symbol that's
 106 ;; the name of each button-type, however, we use a separate symbol (with
 107 ;; `-button' appended, and uninterned) to store the properties.  This is
 108 ;; to avoid name clashes.
 109
 110 ;; [this is an internal function]
 111 (defsubst button-category-symbol (type)
 112   "Return the symbol used by button-type TYPE to store properties.
 113 Buttons inherit them by setting their `category' property to that symbol."
 114   (or (get type 'button-category-symbol)
 115       (error "Unknown button type `%s'" type)))
 116
 117 ;;;###autoload
 118 (defun define-button-type (name &rest properties)
 119   "Define a `button type' called NAME.
 120 The remaining arguments form a sequence of PROPERTY VALUE pairs,
 121 specifying properties to use as defaults for buttons with this type
 122 \(a button's type may be set by giving it a `type' property when
 123 creating the button, using the :type keyword argument).
 124
 125 In addition, the keyword argument :supertype may be used to specify a
 126 button-type from which NAME inherits its default property values
 127 \(however, the inheritance happens only when NAME is defined; subsequent
 128 changes to a supertype are not reflected in its subtypes)."
 129   (let ((catsym (make-symbol (concat (symbol-name name) "-button")))
 130         (super-catsym
 131          (button-category-symbol
 132           (or (plist-get properties 'supertype)
 133               (plist-get properties :supertype)
 134               'button))))
 135     ;; Provide a link so that it's easy to find the real symbol.
 136     (put name 'button-category-symbol catsym)
 137     ;; Initialize NAME's properties using the global defaults.
 138     (let ((default-props (symbol-plist super-catsym)))
 139       (while default-props
 140         (put catsym (pop default-props) (pop default-props))))
 141     ;; Add NAME as the `type' property, which will then be returned as
 142     ;; the type property of individual buttons.
 143     (put catsym 'type name)
 144     ;; Add the properties in PROPERTIES to the real symbol.
 145     (while properties
 146       (let ((prop (pop properties)))
 147         (when (eq prop :supertype)
 148           (setq prop 'supertype))
 149         (put catsym prop (pop properties))))
 150     ;; Make sure there's a `supertype' property
 151     (unless (get catsym 'supertype)
 152       (put catsym 'supertype 'button))
 153     name))
 154
 155 (defun button-type-put (type prop val)
 156   "Set the button-type TYPE's PROP property to VAL."
 157   (put (button-category-symbol type) prop val))
 158
 159 (defun button-type-get (type prop)
 160   "Get the property of button-type TYPE named PROP."
 161   (get (button-category-symbol type) prop))
 162
 163 (defun button-type-subtype-p (type supertype)
 164   "Return t if button-type TYPE is a subtype of SUPERTYPE."
 165   (or (eq type supertype)
 166       (and type
 167            (button-type-subtype-p (button-type-get type 'supertype)
 168                                   supertype))))
 169
 170 \f
 171 ;; Button properties and other attributes
 172
 173 (defun button-start (button)
 174   "Return the position at which BUTTON starts."
 175   (if (overlayp button)
 176       (overlay-start button)
 177     ;; Must be a text-property button.
 178     (or (previous-single-property-change (1+ button) 'button)
 179         (point-min))))
 180
 181 (defun button-end (button)
 182   "Return the position at which BUTTON ends."
 183   (if (overlayp button)
 184       (overlay-end button)
 185     ;; Must be a text-property button.
 186     (or (next-single-property-change button 'button)
 187         (point-max))))
 188
 189 (defun button-get (button prop)
 190   "Get the property of button BUTTON named PROP."
 191   (if (overlayp button)
 192       (overlay-get button prop)
 193     ;; Must be a text-property button.
 194     (get-text-property button prop)))
 195
 196 (defun button-put (button prop val)
 197   "Set BUTTON's PROP property to VAL."
 198   ;; Treat some properties specially.
 199   (cond ((memq prop '(type :type))
 200          ;; We translate a `type' property a `category' property, since
 201          ;; that's what's actually used by overlays/text-properties for
 202          ;; inheriting properties.
 203          (setq prop 'category)
 204          (setq val (button-category-symbol val)))
 205         ((eq prop 'category)
 206          ;; Disallow updating the `category' property directly.
 207          (error "Button `category' property may not be set directly")))
 208   ;; Add the property.
 209   (if (overlayp button)
 210       (overlay-put button prop val)
 211     ;; Must be a text-property button.
 212     (put-text-property
 213      (or (previous-single-property-change (1+ button) 'button)
 214          (point-min))
 215      (or (next-single-property-change button 'button)
 216          (point-max))
 217      prop val)))
 218
 219 (defsubst button-activate (button &optional use-mouse-action)
 220   "Call BUTTON's action property.
 221 If USE-MOUSE-ACTION is non-nil, invoke the button's mouse-action
 222 instead of its normal action; if the button has no mouse-action,
 223 the normal action is used instead."
 224   (let ((action (or (and use-mouse-action (button-get button 'mouse-action))
 225                     (button-get button 'action))))
 226     (if (markerp action)
 227         (save-selected-window
 228           (select-window (display-buffer (marker-buffer action)))
 229           (goto-char action)
 230           (recenter 0))
 231       (funcall action button))))
 232
 233 (defun button-label (button)
 234   "Return BUTTON's text label."
 235   (buffer-substring-no-properties (button-start button) (button-end button)))
 236
 237 (defsubst button-type (button)
 238   "Return BUTTON's button-type."
 239   (button-get button 'type))
 240
 241 (defun button-has-type-p (button type)
 242   "Return t if BUTTON has button-type TYPE, or one of TYPE's subtypes."
 243   (button-type-subtype-p (button-get button 'type) type))
 244
 245 \f
 246 ;; Creating overlay buttons
 247
 248 ;;;###autoload
 249 (defun make-button (beg end &rest properties)
 250   "Make a button from BEG to END in the current buffer.
 251 The remaining arguments form a sequence of PROPERTY VALUE pairs,
 252 specifying properties to add to the button.
 253 In addition, the keyword argument :type may be used to specify a
 254 button-type from which to inherit other properties; see
 255 `define-button-type'.
 256
 257 Also see `make-text-button', `insert-button'."
 258   (let ((overlay (make-overlay beg end nil t nil)))
 259     (while properties
 260       (button-put overlay (pop properties) (pop properties)))
 261     ;; Put a pointer to the button in the overlay, so it's easy to get
 262     ;; when we don't actually have a reference to the overlay.
 263     (overlay-put overlay 'button overlay)
 264     ;; If the user didn't specify a type, use the default.
 265     (unless (overlay-get overlay 'category)
 266       (overlay-put overlay 'category 'default-button))
 267     ;; OVERLAY is the button, so return it
 268     overlay))
 269
 270 ;;;###autoload
 271 (defun insert-button (label &rest properties)
 272   "Insert a button with the label LABEL.
 273 The remaining arguments form a sequence of PROPERTY VALUE pairs,
 274 specifying properties to add to the button.
 275 In addition, the keyword argument :type may be used to specify a
 276 button-type from which to inherit other properties; see
 277 `define-button-type'.
 278
 279 Also see `insert-text-button', `make-button'."
 280   (apply #'make-button
 281          (prog1 (point) (insert label))
 282          (point)
 283          properties))
 284
 285 \f
 286 ;; Creating text-property buttons
 287
 288 ;;;###autoload
 289 (defun make-text-button (beg end &rest properties)
 290   "Make a button from BEG to END in the current buffer.
 291 The remaining arguments form a sequence of PROPERTY VALUE pairs,
 292 specifying properties to add to the button.
 293 In addition, the keyword argument :type may be used to specify a
 294 button-type from which to inherit other properties; see
 295 `define-button-type'.
 296
 297 This function is like `make-button', except that the button is actually
 298 part of the text instead of being a property of the buffer.  Creating
 299 large numbers of buttons can also be somewhat faster using
 300 `make-text-button'.
 301
 302 Also see `insert-text-button'."
 303   (let ((type-entry
 304          (or (plist-member properties 'type)
 305              (plist-member properties :type))))
 306     ;; Disallow setting the `category' property directly.
 307     (when (plist-get properties 'category)
 308       (error "Button `category' property may not be set directly"))
 309     (if (null type-entry)
 310         ;; The user didn't specify a `type' property, use the default.
 311         (setq properties (cons 'category (cons 'default-button properties)))
 312       ;; The user did specify a `type' property.  Translate it into a
 313       ;; `category' property, which is what's actually used by
 314       ;; text-properties for inheritance.
 315       (setcar type-entry 'category)
 316       (setcar (cdr type-entry)
 317               (button-category-symbol (car (cdr type-entry))))))
 318   ;; Now add all the text properties at once
 319   (add-text-properties beg end
 320                        ;; Each button should have a non-eq `button'
 321                        ;; property so that next-single-property-change can
 322                        ;; detect boundaries reliably.
 323                        (cons 'button (cons (list t) properties)))
 324   ;; Return something that can be used to get at the button.
 325   beg)
 326
 327 ;;;###autoload
 328 (defun insert-text-button (label &rest properties)
 329   "Insert a button with the label LABEL.
 330 The remaining arguments form a sequence of PROPERTY VALUE pairs,
 331 specifying properties to add to the button.
 332 In addition, the keyword argument :type may be used to specify a
 333 button-type from which to inherit other properties; see
 334 `define-button-type'.
 335
 336 This function is like `insert-button', except that the button is
 337 actually part of the text instead of being a property of the buffer.
 338 Creating large numbers of buttons can also be somewhat faster using
 339 `insert-text-button'.
 340
 341 Also see `make-text-button'."
 342   (apply #'make-text-button
 343          (prog1 (point) (insert label))
 344          (point)
 345          properties))
 346
 347 \f
 348 ;; Finding buttons in a buffer
 349
 350 (defun button-at (pos)
 351   "Return the button at position POS in the current buffer, or nil."
 352   (let ((button (get-char-property pos 'button)))
 353     (if (or (overlayp button) (null button))
 354         button
 355       ;; Must be a text-property button; return a marker pointing to it.
 356       (copy-marker pos t))))
 357
 358 (defun next-button (pos &optional count-current)
 359   "Return the next button after position POS in the current buffer.
 360 If COUNT-CURRENT is non-nil, count any button at POS in the search,
 361 instead of starting at the next button."
 362     (unless count-current
 363       ;; Search for the next button boundary.
 364       (setq pos (next-single-char-property-change pos 'button)))
 365     (and (< pos (point-max))
 366          (or (button-at pos)
 367              ;; We must have originally been on a button, and are now in
 368              ;; the inter-button space.  Recurse to find a button.
 369              (next-button pos))))
 370
 371 (defun previous-button (pos &optional count-current)
 372   "Return the previous button before position POS in the current buffer.
 373 If COUNT-CURRENT is non-nil, count any button at POS in the search,
 374 instead of starting at the next button."
 375   (let ((button (button-at pos)))
 376     (if button
 377         (if count-current
 378             button
 379           ;; We started out on a button, so move to its start and look
 380           ;; for the previous button boundary.
 381           (setq pos (previous-single-char-property-change
 382                      (button-start button) 'button))
 383           (let ((new-button (button-at pos)))
 384             (if new-button
 385                 ;; We are in a button again; this can happen if there
 386                 ;; are adjacent buttons (or at bob).
 387                 (unless (= pos (button-start button)) new-button)
 388               ;; We are now in the space between buttons.
 389               (previous-button pos))))
 390       ;; We started out in the space between buttons.
 391       (setq pos (previous-single-char-property-change pos 'button))
 392       (or (button-at pos)
 393           (and (> pos (point-min))
 394                (button-at (1- pos)))))))
 395
 396 \f
 397 ;; User commands
 398
 399 (defun push-button (&optional pos use-mouse-action)
 400   "Perform the action specified by a button at location POS.
 401 POS may be either a buffer position or a mouse-event.  If
 402 USE-MOUSE-ACTION is non-nil, invoke the button's mouse-action
 403 instead of its normal action; if the button has no mouse-action,
 404 the normal action is used instead.  The action may be either a
 405 function to call or a marker to display.
 406 POS defaults to point, except when `push-button' is invoked
 407 interactively as the result of a mouse-event, in which case, the
 408 mouse event is used.
 409 If there's no button at POS, do nothing and return nil, otherwise
 410 return t."
 411   (interactive
 412    (list (if (integerp last-command-event) (point) last-command-event)))
 413   (if (and (not (integerp pos)) (eventp pos))
 414       ;; POS is a mouse event; switch to the proper window/buffer
 415       (let ((posn (event-start pos)))
 416         (with-current-buffer (window-buffer (posn-window posn))
 417           (push-button (posn-point posn) t)))
 418     ;; POS is just normal position
 419     (let ((button (button-at (or pos (point)))))
 420       (if (not button)
 421           nil
 422         (button-activate button use-mouse-action)
 423         t))))
 424
 425 (defun forward-button (n &optional wrap display-message)
 426   "Move to the Nth next button, or Nth previous button if N is negative.
 427 If N is 0, move to the start of any button at point.
 428 If WRAP is non-nil, moving past either end of the buffer continues from the
 429 other end.
 430 If DISPLAY-MESSAGE is non-nil, the button's help-echo string is displayed.
 431 Any button with a non-nil `skip' property is skipped over.
 432 Returns the button found."
 433   (interactive "p\nd\nd")
 434   (let (button)
 435     (if (zerop n)
 436         ;; Move to start of current button
 437         (if (setq button (button-at (point)))
 438             (goto-char (button-start button)))
 439       ;; Move to Nth next button
 440       (let ((iterator (if (> n 0) #'next-button #'previous-button))
 441             (wrap-start (if (> n 0) (point-min) (point-max))))
 442         (setq n (abs n))
 443         (setq button t)                 ; just to start the loop
 444         (while (and (> n 0) button)
 445           (setq button (funcall iterator (point)))
 446           (when (and (not button) wrap)
 447             (setq button (funcall iterator wrap-start t)))
 448           (when button
 449             (goto-char (button-start button))
 450             (unless (button-get button 'skip)
 451               (setq n (1- n)))))))
 452     (if (null button)
 453         (error (if wrap "No buttons!" "No more buttons"))
 454       (let ((msg (and display-message (button-get button 'help-echo))))
 455         (when msg
 456           (message "%s" msg)))
 457       button)))
 458
 459 (defun backward-button (n &optional wrap display-message)
 460   "Move to the Nth previous button, or Nth next button if N is negative.
 461 If N is 0, move to the start of any button at point.
 462 If WRAP is non-nil, moving past either end of the buffer continues from the
 463 other end.
 464 If DISPLAY-MESSAGE is non-nil, the button's help-echo string is displayed.
 465 Any button with a non-nil `skip' property is skipped over.
 466 Returns the button found."
 467   (interactive "p\nd\nd")
 468   (forward-button (- n) wrap display-message))
 469
 470
 471 (provide 'button)
 472
 473 ;;; arch-tag: 5f2c7627-413b-4097-b282-630f89d9c5e9
 474 ;;; button.el ends here