lisp/button.el

   1 ;;; button.el --- clickable buttons
   2 ;;
   3 ;; Copyright (C) 2001 Free Software Foundation, Inc.
   4 ;;
   5 ;; Author: Miles Bader <miles@gnu.org>
   6 ;; Keywords: extensions
   7 ;;
   8 ;; This file is part of GNU Emacs.
   9 ;;
  10 ;; GNU Emacs is free software; you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation; either version 2, or (at your option)
  13 ;; any later version.
  14 ;;
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19 ;;
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  22 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23 ;; Boston, MA 02111-1307, USA.
  24
  25 ;;; Commentary:
  26 ;;
  27 ;; This package defines functions for inserting and manipulating
  28 ;; clickable buttons in Emacs buffers, such as might be used for help
  29 ;; hyperlinks, etc.
  30 ;;
  31 ;; In some ways it duplicates functionality also offered by the
  32 ;; `widget' package, but the button package has the advantage that it
  33 ;; is (1) much faster, (2) much smaller, and (3) much, much, simpler
  34 ;; (the code, that is, not the interface).
  35 ;;
  36 ;; Buttons can either use overlays, in which case the button is
  37 ;; represented by the overlay itself, or text-properties, in which case
  38 ;; the button is represented by a marker or buffer-position pointing
  39 ;; somewhere in the button.  In the latter case, no markers into the
  40 ;; buffer are retained, which is important for speed if there are are
  41 ;; extremely large numbers of buttons.
  42 ;;
  43 ;; Using `define-button-type' to define default properties for buttons
  44 ;; is not necessary, but it is is encouraged, since doing so makes the
  45 ;; resulting code clearer and more efficient.
  46 ;;
  47
  48 ;;; Code:
  49
  50 \f
  51 ;; Globals
  52
  53 (defface button '((((type pc) (class color))
  54                    (:foreground "lightblue"))
  55                   (t :underline t))
  56   "Default face used for buttons."
  57   :group 'faces)
  58
  59 ;;;###autoload
  60 (defvar button-map
  61   (let ((map (make-sparse-keymap)))
  62     (define-key map "\r" 'push-button)
  63     (define-key map [mouse-2] 'push-button)
  64     map)
  65   "Keymap used by buttons.")
  66
  67 ;;;###autoload
  68 (defvar button-buffer-map
  69   (let ((map (make-sparse-keymap)))
  70     (define-key map [?\t] 'forward-button)
  71     (define-key map [backtab] 'backward-button)
  72     map)
  73   "Keymap useful for buffers containing buttons.
  74 Mode-specific keymaps may want to use this as their parent keymap.")
  75
  76 ;; Default properties for buttons
  77 (put 'default-button 'face 'button)
  78 (put 'default-button 'mouse-face 'highlight)
  79 (put 'default-button 'keymap button-map)
  80 (put 'default-button 'type 'button)
  81 (put 'default-button 'action 'ignore)
  82 (put 'default-button 'help-echo "mouse-2, RET: Push this button")
  83 ;; Make overlay buttons go away if their underlying text is deleted.
  84 (put 'default-button 'evaporate t)
  85 ;; Prevent insertions adjacent to the text-property buttons from
  86 ;; inheriting its properties.
  87 (put 'default-button 'rear-nonsticky t)
  88 ;; Text property buttons don't have a `button' property of their own, so
  89 ;; they inherit this.
  90 (put 'default-button 'button t)
  91
  92 ;; A `category-symbol' property for the default button type
  93 (put 'button 'button-category-symbol 'default-button)
  94
  95 \f
  96 ;; Button types (which can be used to hold default properties for buttons)
  97
  98 ;; Because button-type properties are inherited by buttons using the
  99 ;; special `category' property (implemented by both overlays and
 100 ;; text-properties), we need to store them on a symbol to which the
 101 ;; `category' properties can point.  Instead of using the symbol that's
 102 ;; the name of each button-type, however, we use a separate symbol (with
 103 ;; `-button' appended, and uninterned) to store the properties.  This is
 104 ;; to avoid name clashes.
 105
 106 ;; [this is an internal function]
 107 (defsubst button-category-symbol (type)
 108   "Return the symbol used by button-type TYPE to store properties.
 109 Buttons inherit them by setting their `category' property to that symbol."
 110   (or (get type 'button-category-symbol)
 111       (error "Unknown button type `%s'" type)))
 112
 113 ;;;###autoload
 114 (defun define-button-type (name &rest properties)
 115   "Define a `button type' called NAME.
 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   (funcall (or (and use-mouse-action (button-get button 'mouse-action))
 221                (button-get button 'action))
 222            button))
 223
 224 (defun button-label (button)
 225   "Return BUTTON's text label."
 226   (buffer-substring-no-properties (button-start button) (button-end button)))
 227
 228 (defsubst button-type (button)
 229   "Return BUTTON's button-type."
 230   (button-get button 'type))
 231
 232 (defun button-has-type-p (button type)
 233   "Return t if BUTTON has button-type TYPE, or one of TYPE's subtypes."
 234   (button-type-subtype-p (button-get button 'type) type))
 235
 236 \f
 237 ;; Creating overlay buttons
 238
 239 ;;;###autoload
 240 (defun make-button (beg end &rest properties)
 241   "Make a button from BEG to END in the current buffer.
 242 The remaining arguments form a sequence of PROPERTY VALUE pairs,
 243 specifying properties to add to the button.
 244 In addition, the keyword argument :type may be used to specify a
 245 button-type from which to inherit other properties; see
 246 `define-button-type'.
 247
 248 Also see `make-text-button', `insert-button'."
 249   (let ((overlay (make-overlay beg end nil t nil)))
 250     (while properties
 251       (button-put overlay (pop properties) (pop properties)))
 252     ;; Put a pointer to the button in the overlay, so it's easy to get
 253     ;; when we don't actually have a reference to the overlay.
 254     (overlay-put overlay 'button overlay)
 255     ;; If the user didn't specify a type, use the default.
 256     (unless (overlay-get overlay 'category)
 257       (overlay-put overlay 'category 'default-button))
 258     ;; OVERLAY is the button, so return it
 259     overlay))
 260
 261 ;;;###autoload
 262 (defun insert-button (label &rest properties)
 263   "Insert a button with the label LABEL.
 264 The remaining arguments form a sequence of PROPERTY VALUE pairs,
 265 specifying properties to add to the button.
 266 In addition, the keyword argument :type may be used to specify a
 267 button-type from which to inherit other properties; see
 268 `define-button-type'.
 269
 270 Also see `insert-text-button', `make-button'."
 271   (apply #'make-button
 272          (prog1 (point) (insert label))
 273          (point)
 274          properties))
 275
 276 \f
 277 ;; Creating text-property buttons
 278
 279 ;;;###autoload
 280 (defun make-text-button (beg end &rest properties)
 281   "Make a button from BEG to END in the current buffer.
 282 The remaining arguments form a sequence of PROPERTY VALUE pairs,
 283 specifying properties to add to the button.
 284 In addition, the keyword argument :type may be used to specify a
 285 button-type from which to inherit other properties; see
 286 `define-button-type'.
 287
 288 This function is like `make-button', except that the button is actually
 289 part of the text instead of being a property of the buffer.  Creating
 290 large numbers of buttons can also be somewhat faster using
 291 `make-text-button'.
 292
 293 Also see `insert-text-button'."
 294   (let (prop val)
 295     (while properties
 296       (setq prop (pop properties))
 297       (setq val (pop properties))
 298       ;; Note that all the following code is basically equivalent to
 299       ;; `button-put', but we can do it much more efficiently since we
 300       ;; already have BEG and END.
 301       (cond ((memq prop '(type :type))
 302              ;; We translate a `type' property into a `category'
 303              ;; property, since that's what's actually used by
 304              ;; text-properties for inheritance.
 305              (setq prop 'category)
 306              (setq val (button-category-symbol val)))
 307             ((eq prop 'category)
 308              ;; Disallow setting the `category' property directly.
 309              (error "Button `category' property may not be set directly")))
 310       ;; Add the property.
 311       (put-text-property beg end prop val)))
 312   ;; Return something that can be used to get at the button.
 313   beg)
 314
 315 ;;;###autoload
 316 (defun insert-text-button (label &rest properties)
 317   "Insert a button with the label LABEL.
 318 The remaining arguments form a sequence of PROPERTY VALUE pairs,
 319 specifying properties to add to the button.
 320 In addition, the keyword argument :type may be used to specify a
 321 button-type from which to inherit other properties; see
 322 `define-button-type'.
 323
 324 This function is like `insert-button', except that the button is
 325 actually part of the text instead of being a property of the buffer.
 326 Creating large numbers of buttons can also be somewhat faster using
 327 `insert-text-button'.
 328
 329 Also see `make-text-button'."
 330   (apply #'make-text-button
 331          (prog1 (point) (insert label))
 332          (point)
 333          properties))
 334
 335 \f
 336 ;; Finding buttons in a buffer
 337
 338 (defun button-at (pos)
 339   "Return the button at position POS in the current buffer, or nil."
 340   (let ((button (get-char-property pos 'button)))
 341     (if (or (overlayp button) (null button))
 342         button
 343       ;; Must be a text-property button; return a marker pointing to it.
 344       (copy-marker pos t))))
 345
 346 (defun next-button (pos &optional count-current)
 347   "Return the next button after position POS in the current buffer.
 348 If COUNT-CURRENT is non-nil, count any button at POS in the search,
 349 instead of starting at the next button."
 350     (unless count-current
 351       ;; Search for the next button boundary.
 352       (setq pos (next-single-char-property-change pos 'button)))
 353     (and (< pos (point-max))
 354          (or (button-at pos)
 355              ;; We must have originally been on a button, and are now in
 356              ;; the inter-button space.  Recurse to find a button.
 357              (next-button pos))))
 358
 359 (defun previous-button (pos &optional count-current)
 360   "Return the Nth button before 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     (setq pos (previous-single-char-property-change pos 'button)))
 365   (and (> pos (point-min))
 366        (or (button-at (1- 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            (previous-button pos))))
 370
 371 \f
 372 ;; User commands
 373
 374 (defun push-button (&optional pos use-mouse-action)
 375   "Perform the action specified by a button at location POS.
 376 POS may be either a buffer position or a mouse-event.
 377 If USE-MOUSE-ACTION is non-nil, invoke the button's mouse-action
 378 instead of its normal action; if the button has no mouse-action,
 379 the normal action is used instead.
 380 POS defaults to point, except when `push-button' is invoked
 381 interactively as the result of a mouse-event, in which case, the
 382 mouse event is used.
 383 If there's no button at POS, do nothing and return nil, otherwise
 384 return t."
 385   (interactive
 386    (list (if (integerp last-command-event) (point) last-command-event)))
 387   (if (and (not (integerp pos)) (eventp pos))
 388       ;; POS is a mouse event; switch to the proper window/buffer
 389       (let ((posn (event-start pos)))
 390         (with-current-buffer (window-buffer (posn-window posn))
 391           (push-button (posn-point posn) t)))
 392     ;; POS is just normal position
 393     (let ((button (button-at (or pos (point)))))
 394       (if (not button)
 395           nil
 396         (button-activate button use-mouse-action)
 397         t))))
 398
 399 (defun forward-button (n &optional wrap display-message)
 400   "Move to the Nth next button, or Nth previous button if N is negative.
 401 If N is 0, move to the start of any button at point.
 402 If WRAP is non-nil, moving past either end of the buffer continues from the
 403 other end.
 404 If DISPLAY-MESSAGE is non-nil, the button's help-echo string is displayed.
 405 Any button with a non-nil `skip' property is skipped over.
 406 Returns the button found."
 407   (interactive "p\nd\nd")
 408   (let (button)
 409     (if (zerop n)
 410         ;; Move to start of current button
 411         (if (setq button (button-at (point)))
 412             (goto-char (button-start button)))
 413       ;; Move to Nth next button
 414       (let ((iterator (if (> n 0) #'next-button #'previous-button))
 415             (wrap-start (if (> n 0) (point-min) (point-max))))
 416         (setq n (abs n))
 417         (setq button t)                 ; just to start the loop
 418         (while (and (> n 0) button)
 419           (setq button (funcall iterator (point)))
 420           (when (and (not button) wrap)
 421             (setq button (funcall iterator wrap-start t)))
 422           (when button
 423             (goto-char (button-start button))
 424             (unless (button-get button 'skip)
 425               (setq n (1- n)))))))
 426     (if (null button)
 427         (error (if wrap "No buttons!" "No more buttons"))
 428       (let ((msg (and display-message (button-get button 'help-echo))))
 429         (when msg
 430           (message "%s" msg)))
 431       button)))
 432
 433 (defun backward-button (n &optional wrap display-message)
 434   "Move to the Nth previous button, or Nth next button if N is negative.
 435 If N is 0, move to the start of any button at point.
 436 If WRAP is non-nil, moving past either end of the buffer continues from the
 437 other end.
 438 If DISPLAY-MESSAGE is non-nil, the button's help-echo string is displayed.
 439 Any button with a non-nil `skip' property is skipped over.
 440 Returns the button found."
 441   (interactive "p\nd\nd")
 442   (forward-button (- n) wrap display-message))
 443
 444
 445 (provide 'button)
 446
 447 ;;; button.el ends here