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;;; wid-edit.el --- Functions for creating and using widgets.
;;
;; Copyright (C) 1996, 1997 Free Software Foundation, Inc.
;;
;; Author: Per Abrahamsen <abraham@dina.kvl.dk>
;; Keywords: extensions
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;; Version: 1.9936
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;; X-URL: http://www.dina.kvl.dk/~abraham/custom/

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;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

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;;; Commentary:
;;
;; See `widget.el'.

;;; Code:

(require 'widget)
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(eval-when-compile (require 'cl))
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;;; Compatibility.

(eval-and-compile
  (autoload 'pp-to-string "pp")
  (autoload 'Info-goto-node "info")

  (when (string-match "XEmacs" emacs-version)
    (condition-case nil
	(require 'overlay)
      (error (load-library "x-overlay"))))
  
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  (if (string-match "XEmacs" emacs-version)
      (defun widget-event-point (event)
	"Character position of the end of event if that exists, or nil."
	(if (mouse-event-p event)
	    (event-point event)
	  nil))
    (defun widget-event-point (event)
      "Character position of the end of event if that exists, or nil."
      (posn-point (event-end event))))

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(defalias 'widget-read-event (if (string-match "XEmacs" emacs-version)
				   'next-event
				 'read-event))

  ;; The following should go away when bundled with Emacs.
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  (condition-case ()
      (require 'custom)
    (error nil))

  (unless (and (featurep 'custom) (fboundp 'custom-declare-variable))
    ;; We have the old custom-library, hack around it!
    (defmacro defgroup (&rest args) nil)
    (defmacro defcustom (var value doc &rest args) 
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      (` (defvar (, var) (, value) (, doc))))
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    (defmacro defface (&rest args) nil)
    (define-widget-keywords :prefix :tag :load :link :options :type :group)
    (when (fboundp 'copy-face)
      (copy-face 'default 'widget-documentation-face)
      (copy-face 'bold 'widget-button-face)
      (copy-face 'italic 'widget-field-face)))

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  (unless (fboundp 'button-release-event-p)
    ;; XEmacs function missing from Emacs.
    (defun button-release-event-p (event)
      "Non-nil if EVENT is a mouse-button-release event object."
      (and (eventp event)
	   (memq (event-basic-type event) '(mouse-1 mouse-2 mouse-3))
	   (or (memq 'click (event-modifiers event))
	       (memq  'drag (event-modifiers event))))))
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  (unless (fboundp 'error-message-string)
    ;; Emacs function missing in XEmacs.
    (defun error-message-string (obj)
      "Convert an error value to an error message."
      (let ((buf (get-buffer-create " *error-message*")))
	(erase-buffer buf)
	(display-error obj buf)
	(buffer-string buf)))))

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(when (let ((a "foo"))
	(put-text-property 1 2 'foo 1 a)
	(put-text-property 1 2 'bar 2 a)
	(set-text-properties 1 2 nil a)
	(text-properties-at 1 a))
  ;; XEmacs 20.2 and earlier had a buggy set-text-properties.
  (defun set-text-properties (start end props &optional buffer-or-string)
    "Completely replace properties of text from START to END.
The third argument PROPS is the new property list.
The optional fourth argument, BUFFER-OR-STRING,
is the string or buffer containing the text."
    (map-extents #'(lambda (extent ignored)
		     (remove-text-properties
		      start end
		      (list (extent-property extent 'text-prop)
			    nil)
		      buffer-or-string)
		     nil)
		 buffer-or-string start end nil nil 'text-prop)
    (add-text-properties start end props buffer-or-string)))

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;;; Customization.

(defgroup widgets nil
  "Customization support for the Widget Library."
  :link '(custom-manual "(widget)Top")
  :link '(url-link :tag "Development Page" 
		   "http://www.dina.kvl.dk/~abraham/custom/")
  :prefix "widget-"
  :group 'extensions
  :group 'hypermedia)

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(defgroup widget-documentation nil
  "Options controling the display of documentation strings."
  :group 'widgets)

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(defgroup widget-faces nil
  "Faces used by the widget library."
  :group 'widgets
  :group 'faces)

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(defvar widget-documentation-face 'widget-documentation-face
  "Face used for documentation strings in widges.
This exists as a variable so it can be set locally in certain buffers.")

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(defface widget-documentation-face '((((class color)
				       (background dark))
				      (:foreground "lime green"))
				     (((class color)
				       (background light))
				      (:foreground "dark green"))
				     (t nil))
  "Face used for documentation text."
  :group 'widget-documentation
  :group 'widget-faces)

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(defface widget-button-face '((t (:bold t)))
  "Face used for widget buttons."
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  :group 'widget-faces)
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(defcustom widget-mouse-face 'highlight
  "Face used for widget buttons when the mouse is above them."
  :type 'face
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  :group 'widget-faces)
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(defface widget-field-face '((((class grayscale color)
			       (background light))
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			      (:background "gray85"))
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			     (((class grayscale color)
			       (background dark))
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			      (:background "dim gray"))
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			     (t 
			      (:italic t)))
  "Face used for editable fields."
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  :group 'widget-faces)
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;;; Utility functions.
;;
;; These are not really widget specific.

(defsubst widget-plist-member (plist prop)
  ;; Return non-nil if PLIST has the property PROP.
  ;; PLIST is a property list, which is a list of the form
  ;; (PROP1 VALUE1 PROP2 VALUE2 ...).  PROP is a symbol.
  ;; Unlike `plist-get', this allows you to distinguish between a missing
  ;; property and a property with the value nil.
  ;; The value is actually the tail of PLIST whose car is PROP.
  (while (and plist (not (eq (car plist) prop)))
    (setq plist (cdr (cdr plist))))
  plist)

(defun widget-princ-to-string (object)
  ;; Return string representation of OBJECT, any Lisp object.
  ;; No quoting characters are used; no delimiters are printed around
  ;; the contents of strings.
  (save-excursion
    (set-buffer (get-buffer-create " *widget-tmp*"))
    (erase-buffer)
    (let ((standard-output (current-buffer)))
      (princ object))
    (buffer-string)))

(defun widget-clear-undo ()
  "Clear all undo information."
  (buffer-disable-undo (current-buffer))
  (buffer-enable-undo))

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(defcustom widget-menu-max-size 40
  "Largest number of items allowed in a popup-menu.
Larger menus are read through the minibuffer."
  :group 'widgets
  :type 'integer)

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(defcustom widget-menu-minibuffer-flag nil
  "*Control how to ask for a choice from the keyboard.
Non-nil means use the minibuffer;
nil means read a single character."
  :group 'widgets
  :type 'boolean)

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(defun widget-choose (title items &optional event)
  "Choose an item from a list.

First argument TITLE is the name of the list.
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Second argument ITEMS is an list whose members are either
 (NAME . VALUE), to indicate selectable items, or just strings to
 indicate unselectable items.
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Optional third argument EVENT is an input event.

The user is asked to choose between each NAME from the items alist,
and the VALUE of the chosen element will be returned.  If EVENT is a
mouse event, and the number of elements in items is less than
`widget-menu-max-size', a popup menu will be used, otherwise the
minibuffer."
  (cond ((and (< (length items) widget-menu-max-size)
	      event (fboundp 'x-popup-menu) window-system)
	 ;; We are in Emacs-19, pressed by the mouse
	 (x-popup-menu event
		       (list title (cons "" items))))
	((and (< (length items) widget-menu-max-size)
	      event (fboundp 'popup-menu) window-system)
	 ;; We are in XEmacs, pressed by the mouse
	 (let ((val (get-popup-menu-response
		     (cons title
			   (mapcar
			    (function
			     (lambda (x)
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			       (if (stringp x)
				   (vector x nil nil) 
				 (vector (car x) (list (car x)) t))))
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			    items)))))
	   (setq val (and val
			  (listp (event-object val))
			  (stringp (car-safe (event-object val)))
			  (car (event-object val))))
	   (cdr (assoc val items))))
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	(widget-menu-minibuffer-flag
	 ;; Read the choice of name from the minibuffer.
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	 (setq items (widget-remove-if 'stringp items))
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	 (let ((val (completing-read (concat title ": ") items nil t)))
	   (if (stringp val)
	       (let ((try (try-completion val items)))
		 (when (stringp try)
		   (setq val try))
		 (cdr (assoc val items)))
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	     nil)))
	(t
	 ;; Construct a menu of the choices
	 ;; and then use it for prompting for a single character.
	 (let* ((overriding-terminal-local-map
		 (make-sparse-keymap))
		map choice (next-digit ?0)
		value)
	   ;; Define SPC as a prefix char to get to this menu.
	   (define-key overriding-terminal-local-map " "
	     (setq map (make-sparse-keymap title)))
	   (while items
	     (setq choice (car items) items (cdr items))
	     (if (consp choice)
		 (let* ((name (car choice))
		       (function (cdr choice))
		       (character (aref name 0)))
		   ;; Pick a character for this choice;
		   ;; avoid duplication.
		   (when (lookup-key map (vector character))
		     (setq character (downcase character))
		     (when (lookup-key map (vector character))
		       (setq character next-digit
			     next-digit (1+ next-digit))))
		   (define-key map (vector character)
		     (cons (format "%c = %s" character name) function)))))
	   (define-key map [?\C-g] '("Quit" . keyboard-quit))
	   (define-key map [t] 'keyboard-quit)
	   (setcdr map (nreverse (cdr map)))
	   ;; Unread a SPC to lead to our new menu.
	   (setq unread-command-events (cons ?\ unread-command-events))
	   ;; Read a char with the menu, and return the result
	   ;; that corresponds to it.
	   (setq value
		 (lookup-key overriding-terminal-local-map
			     (read-key-sequence title) t))
	   (when (eq value 'keyboard-quit)
	     (error "Canceled"))
	   value))))
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(defun widget-remove-if (predictate list)
  (let (result (tail list))
    (while tail
      (or (funcall predictate (car tail))
	  (setq result (cons (car tail) result)))
      (setq tail (cdr tail)))
    (nreverse result)))

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;;; Widget text specifications.
;; 
;; These functions are for specifying text properties. 

(defun widget-specify-none (from to)
  ;; Clear all text properties between FROM and TO.
  (set-text-properties from to nil))

(defun widget-specify-text (from to)
  ;; Default properties.
  (add-text-properties from to (list 'read-only t
				     'front-sticky t
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				     'rear-nonsticky nil
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				     'start-open nil
				     'end-open nil)))
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(defcustom widget-field-add-space 
  (or (< emacs-major-version 20)
      (and (eq emacs-major-version 20)
	   (< emacs-minor-version 3))
      (not (string-match "XEmacs" emacs-version)))
  "Non-nil means add extra space at the end of editable text fields.

This is needed on all versions of Emacs, and on XEmacs before 20.3.  
If you don't add the space, it will become impossible to edit a zero
size field."
  :type 'boolean
  :group 'widgets)

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(defcustom widget-field-use-before-change
  (or (> emacs-minor-version 34)
      (> emacs-major-version 20)
      (string-match "XEmacs" emacs-version))
  "Non-nil means use `before-change-functions' to track editable fields.
This enables the use of undo, but doesn'f work on Emacs 19.34 and earlier. 
Using before hooks also means that the :notify function can't know the
new value."
  :type 'boolean
  :group 'widgets)

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(defun widget-specify-field (widget from to)
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  "Specify editable button for WIDGET between FROM and TO."
  (put-text-property from to 'read-only nil)
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  ;; Terminating space is not part of the field, but necessary in
  ;; order for local-map to work.  Remove next sexp if local-map works
  ;; at the end of the overlay.
  (save-excursion
    (goto-char to)
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    (when widget-field-add-space
      (insert-and-inherit " "))
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    (setq to (point)))
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  (if widget-field-add-space
      (add-text-properties (1- to) to
			   '(front-sticky nil start-open t read-only to))
    (add-text-properties to (1+ to) 
			 '(front-sticky nil start-open t read-only to)))
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  (add-text-properties (1- from) from 
		       '(rear-nonsticky t end-open t read-only from))
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  (let ((map (widget-get widget :keymap))
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	(face (or (widget-get widget :value-face) 'widget-field-face))
	(help-echo (widget-get widget :help-echo))
	(overlay (make-overlay from to nil nil t)))
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    (unless (or (stringp help-echo) (null help-echo))
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      (setq help-echo 'widget-mouse-help))    
    (widget-put widget :field-overlay overlay)
    (overlay-put overlay 'detachable nil)
    (overlay-put overlay 'field widget)
    (overlay-put overlay 'local-map map)
    (overlay-put overlay 'keymap map)
    (overlay-put overlay 'face face)
    (overlay-put overlay 'balloon-help help-echo)
    (overlay-put overlay 'help-echo help-echo)))
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(defun widget-specify-button (widget from to)
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  "Specify button for WIDGET between FROM and TO."
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  (let ((face (widget-apply widget :button-face-get))
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	(help-echo (widget-get widget :help-echo))
	(overlay (make-overlay from to nil t nil)))
    (widget-put widget :button-overlay overlay)
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    (unless (or (null help-echo) (stringp help-echo))
      (setq help-echo 'widget-mouse-help))
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    (overlay-put overlay 'button widget)
    (overlay-put overlay 'mouse-face widget-mouse-face)
    (overlay-put overlay 'balloon-help help-echo)
    (overlay-put overlay 'help-echo help-echo)
    (overlay-put overlay 'face face)))
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(defun widget-mouse-help (extent)
  "Find mouse help string for button in extent."
  (let* ((widget (widget-at (extent-start-position extent)))
	 (help-echo (and widget (widget-get widget :help-echo))))
    (cond ((stringp help-echo)
	   help-echo)
	  ((and (symbolp help-echo) (fboundp help-echo)
		(stringp (setq help-echo (funcall help-echo widget))))
	   help-echo)
	  (t
	   (format "(widget %S :help-echo %S)" widget help-echo)))))

(defun widget-specify-sample (widget from to)
  ;; Specify sample for WIDGET between FROM and TO.
  (let ((face (widget-apply widget :sample-face-get)))
    (when face
      (add-text-properties from to (list 'start-open t
					 'end-open t
					 'face face)))))
(defun widget-specify-doc (widget from to)
  ;; Specify documentation for WIDGET between FROM and TO.
  (add-text-properties from to (list 'widget-doc widget
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				     'face widget-documentation-face)))
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(defmacro widget-specify-insert (&rest form)
  ;; Execute FORM without inheriting any text properties.
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  (`
   (save-restriction
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     (let ((inhibit-read-only t)
	   result
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	   before-change-functions
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	   after-change-functions)
       (insert "<>")
       (narrow-to-region (- (point) 2) (point))
       (widget-specify-none (point-min) (point-max))
       (goto-char (1+ (point-min)))
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       (setq result (progn (,@ form)))
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       (delete-region (point-min) (1+ (point-min)))
       (delete-region (1- (point-max)) (point-max))
       (goto-char (point-max))
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       result))))
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(defface widget-inactive-face '((((class grayscale color)
				  (background dark))
				 (:foreground "light gray"))
				(((class grayscale color)
				  (background light))
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				 (:foreground "dim gray"))
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				(t 
				 (:italic t)))
  "Face used for inactive widgets."
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  :group 'widget-faces)
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(defun widget-specify-inactive (widget from to)
  "Make WIDGET inactive for user modifications."
  (unless (widget-get widget :inactive)
    (let ((overlay (make-overlay from to nil t nil)))
      (overlay-put overlay 'face 'widget-inactive-face)
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      ;; This is disabled, as it makes the mouse cursor change shape.
      ;; (overlay-put overlay 'mouse-face 'widget-inactive-face)
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      (overlay-put overlay 'evaporate t)
      (overlay-put overlay 'priority 100)
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      (overlay-put overlay (if (string-match "XEmacs" emacs-version)
			       'read-only
			     'modification-hooks) '(widget-overlay-inactive))
      (widget-put widget :inactive overlay))))

(defun widget-overlay-inactive (&rest junk)
  "Ignoring the arguments, signal an error."
  (unless inhibit-read-only
    (error "Attempt to modify inactive widget")))


(defun widget-specify-active (widget)
  "Make WIDGET active for user modifications."
  (let ((inactive (widget-get widget :inactive)))
    (when inactive
      (delete-overlay inactive)
      (widget-put widget :inactive nil))))

;;; Widget Properties.

(defsubst widget-type (widget)
  "Return the type of WIDGET, a symbol."
  (car widget))

(defun widget-put (widget property value)
  "In WIDGET set PROPERTY to VALUE.
The value can later be retrived with `widget-get'."
  (setcdr widget (plist-put (cdr widget) property value)))

(defun widget-get (widget property)
  "In WIDGET, get the value of PROPERTY.
The value could either be specified when the widget was created, or
later with `widget-put'."
  (let ((missing t)
	value tmp)
    (while missing
      (cond ((setq tmp (widget-plist-member (cdr widget) property))
	     (setq value (car (cdr tmp))
		   missing nil))
	    ((setq tmp (car widget))
	     (setq widget (get tmp 'widget-type)))
	    (t 
	     (setq missing nil))))
    value))

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(defun widget-get-indirect (widget property)
  "In WIDGET, get the value of PROPERTY.
If the value is a symbol, return its binding.  
Otherwise, just return the value."
  (let ((value (widget-get widget property)))
    (if (symbolp value)
	(symbol-value value)
      value)))

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(defun widget-member (widget property)
  "Non-nil iff there is a definition in WIDGET for PROPERTY."
  (cond ((widget-plist-member (cdr widget) property)
	 t)
	((car widget)
	 (widget-member (get (car widget) 'widget-type) property))
	(t nil)))

;;;###autoload
(defun widget-apply (widget property &rest args)
  "Apply the value of WIDGET's PROPERTY to the widget itself.
ARGS are passed as extra arguments to the function."
  (apply (widget-get widget property) widget args))

(defun widget-value (widget)
  "Extract the current value of WIDGET."
  (widget-apply widget
		:value-to-external (widget-apply widget :value-get)))

(defun widget-value-set (widget value)
  "Set the current value of WIDGET to VALUE."
  (widget-apply widget
		:value-set (widget-apply widget
					 :value-to-internal value)))

(defun widget-match-inline (widget vals)
  ;; In WIDGET, match the start of VALS.
  (cond ((widget-get widget :inline)
	 (widget-apply widget :match-inline vals))
	((and vals
	      (widget-apply widget :match (car vals)))
	 (cons (list (car vals)) (cdr vals)))
	(t nil)))

(defun widget-apply-action (widget &optional event)
  "Apply :action in WIDGET in response to EVENT."
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  (if (widget-apply widget :active)
      (widget-apply widget :action event)
    (error "Attempt to perform action on inactive widget")))
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;;; Helper functions.
;;
;; These are widget specific.

;;;###autoload
(defun widget-prompt-value (widget prompt &optional value unbound)
  "Prompt for a value matching WIDGET, using PROMPT.
The current value is assumed to be VALUE, unless UNBOUND is non-nil."
  (unless (listp widget)
    (setq widget (list widget)))
  (setq prompt (format "[%s] %s" (widget-type widget) prompt))
  (setq widget (widget-convert widget))
  (let ((answer (widget-apply widget :prompt-value prompt value unbound)))
    (unless (widget-apply widget :match answer)
      (error "Value does not match %S type." (car widget)))
    answer))

(defun widget-get-sibling (widget)
  "Get the item WIDGET is assumed to toggle.
This is only meaningful for radio buttons or checkboxes in a list."
  (let* ((parent (widget-get widget :parent))
	 (children (widget-get parent :children))
	 child)
    (catch 'child
      (while children
	(setq child (car children)
	      children (cdr children))
	(when (eq (widget-get child :button) widget)
	  (throw 'child child)))
      nil)))

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(defun widget-map-buttons (function &optional buffer maparg)
  "Map FUNCTION over the buttons in BUFFER.
FUNCTION is called with the arguments WIDGET and MAPARG.

If FUNCTION returns non-nil, the walk is cancelled.

The arguments MAPARG, and BUFFER default to nil and (current-buffer),
respectively."
  (let ((cur (point-min))
	(widget nil)
	(parent nil)
	(overlays (if buffer
		      (save-excursion (set-buffer buffer) (overlay-lists))
		    (overlay-lists))))
    (setq overlays (append (car overlays) (cdr overlays)))
    (while (setq cur (pop overlays))
      (setq widget (overlay-get cur 'button))
      (if (and widget (funcall function widget maparg))
	  (setq overlays nil)))))

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;;; Glyphs.

(defcustom widget-glyph-directory (concat data-directory "custom/")
  "Where widget glyphs are located.
If this variable is nil, widget will try to locate the directory
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automatically."
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  :group 'widgets
  :type 'directory)

(defcustom widget-glyph-enable t
  "If non nil, use glyphs in images when available."
  :group 'widgets
  :type 'boolean)

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(defcustom widget-image-conversion
  '((xpm ".xpm") (gif ".gif") (png ".png") (jpeg ".jpg" ".jpeg")
    (xbm ".xbm"))
  "Conversion alist from image formats to file name suffixes."
  :group 'widgets
  :type '(repeat (cons :format "%v"
		       (symbol :tag "Image Format" unknown)
		       (repeat :tag "Suffixes"
			       (string :format "%v")))))

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(defun widget-glyph-find (image tag)
  "Create a glyph corresponding to IMAGE with string TAG as fallback.
IMAGE should either already be a glyph, or be a file name sans
extension (xpm, xbm, gif, jpg, or png) located in
`widget-glyph-directory'." 
  (cond ((not (and image 
		   (string-match "XEmacs" emacs-version)
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		   widget-glyph-enable
		   (fboundp 'make-glyph)
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		   (fboundp 'locate-file)
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		   image))
	 ;; We don't want or can't use glyphs.
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	 nil)
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	((and (fboundp 'glyphp)
	      (glyphp image))
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	 ;; Already a glyph.  Use it.
	 image)
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	((stringp image)
	 ;; A string.  Look it up in relevant directories.
	 (let* ((dirlist (list (or widget-glyph-directory
				   (concat data-directory
					   "custom/"))
			       data-directory))
		(formats widget-image-conversion)
		file)
	   (while (and formats (not file))
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	     (when (valid-image-instantiator-format-p (car (car formats)))
	       (setq file (locate-file image dirlist
				       (mapconcat 'identity
						  (cdr (car formats))
						  ":"))))
	     (unless file
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	       (setq formats (cdr formats))))
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	   (and file
		;; We create a glyph with the file as the default image
		;; instantiator, and the TAG fallback
		(make-glyph (list (vector (car (car formats)) ':file file)
				  (vector 'string ':data tag))))))
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	((valid-instantiator-p image 'image)
	 ;; A valid image instantiator (e.g. [gif :file "somefile"] etc.)
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	 (make-glyph (list image
			   (vector 'string ':data tag))))
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	((consp image)
	 ;; This could be virtually anything.  Let `make-glyph' sort it out.
	 (make-glyph image))
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	(t
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	 ;; Oh well.
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	 nil)))

(defun widget-glyph-insert (widget tag image &optional down inactive)
  "In WIDGET, insert the text TAG or, if supported, IMAGE.
IMAGE should either be a glyph, an image instantiator, or an image file
name sans extension (xpm, xbm, gif, jpg, or png) located in
`widget-glyph-directory'.

Optional arguments DOWN and INACTIVE is used instead of IMAGE when the
glyph is pressed or inactive, respectively. 

WARNING: If you call this with a glyph, and you want the user to be
able to invoke the glyph, make sure it is unique.  If you use the
same glyph for multiple widgets, invoking any of the glyphs will
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cause the last created widget to be invoked.

Instead of an instantiator, you can also use a list of instantiators,
or whatever `make-glyph' will accept.  However, in that case you must
provide the fallback TAG as a part of the instantiator yourself."
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  (let ((glyph (widget-glyph-find image tag)))
    (if glyph 
	(widget-glyph-insert-glyph widget 
				   glyph
				   (widget-glyph-find down tag)
				   (widget-glyph-find inactive tag))
      (insert tag))))
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(defun widget-glyph-insert-glyph (widget glyph &optional down inactive)
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  "In WIDGET, insert GLYPH.
If optional arguments DOWN and INACTIVE are given, they should be
glyphs used when the widget is pushed and inactive, respectively."
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  (when widget
    (set-glyph-property glyph 'widget widget)
    (when down
      (set-glyph-property down 'widget widget))
    (when inactive
      (set-glyph-property inactive 'widget widget)))
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  (insert "*")
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  (let ((ext (make-extent (point) (1- (point))))
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	(help-echo (and widget (widget-get widget :help-echo))))
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    (set-extent-property ext 'invisible t)
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    (set-extent-property ext 'start-open t)
    (set-extent-property ext 'end-open t)
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    (set-extent-end-glyph ext glyph)
    (when help-echo
      (set-extent-property ext 'balloon-help help-echo)
      (set-extent-property ext 'help-echo help-echo)))
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  (when widget
    (widget-put widget :glyph-up glyph)
    (when down (widget-put widget :glyph-down down))
    (when inactive (widget-put widget :glyph-inactive inactive))))
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;;; Buttons.

(defgroup widget-button nil
  "The look of various kinds of buttons."
  :group 'widgets)

(defcustom widget-button-prefix ""
  "String used as prefix for buttons."
  :type 'string
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  :group 'widget-button)
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(defcustom widget-button-suffix ""
  "String used as suffix for buttons."
  :type 'string
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  :group 'widget-button)
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;;; Creating Widgets.

;;;###autoload
(defun widget-create (type &rest args)
  "Create widget of TYPE.  
The optional ARGS are additional keyword arguments."
  (let ((widget (apply 'widget-convert type args)))
    (widget-apply widget :create)
    widget))

(defun widget-create-child-and-convert (parent type &rest args)
  "As part of the widget PARENT, create a child widget TYPE.
The child is converted, using the keyword arguments ARGS."
  (let ((widget (apply 'widget-convert type args)))
    (widget-put widget :parent parent)
    (unless (widget-get widget :indent)
      (widget-put widget :indent (+ (or (widget-get parent :indent) 0)
				    (or (widget-get widget :extra-offset) 0)
				    (widget-get parent :offset))))
    (widget-apply widget :create)
    widget))

(defun widget-create-child (parent type)
  "Create widget of TYPE."
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  (let ((widget (copy-sequence type)))
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    (widget-put widget :parent parent)
    (unless (widget-get widget :indent)
      (widget-put widget :indent (+ (or (widget-get parent :indent) 0)
				    (or (widget-get widget :extra-offset) 0)
				    (widget-get parent :offset))))
    (widget-apply widget :create)
    widget))

(defun widget-create-child-value (parent type value)
  "Create widget of TYPE with value VALUE."
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  (let ((widget (copy-sequence type)))
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    (widget-put widget :value (widget-apply widget :value-to-internal value))
    (widget-put widget :parent parent)
    (unless (widget-get widget :indent)
      (widget-put widget :indent (+ (or (widget-get parent :indent) 0)
				    (or (widget-get widget :extra-offset) 0)
				    (widget-get parent :offset))))
    (widget-apply widget :create)
    widget))

;;;###autoload
(defun widget-delete (widget)
  "Delete WIDGET."
  (widget-apply widget :delete))

(defun widget-convert (type &rest args)
  "Convert TYPE to a widget without inserting it in the buffer. 
The optional ARGS are additional keyword arguments."
  ;; Don't touch the type.
  (let* ((widget (if (symbolp type) 
		     (list type)
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		   (copy-sequence type)))
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	 (current widget)
	 (keys args))
    ;; First set the :args keyword.
    (while (cdr current)		;Look in the type.
      (let ((next (car (cdr current))))
	(if (and (symbolp next) (eq (aref (symbol-name next) 0) ?:))
	    (setq current (cdr (cdr current)))
	  (setcdr current (list :args (cdr current)))
	  (setq current nil))))
    (while args				;Look in the args.
      (let ((next (nth 0 args)))
	(if (and (symbolp next) (eq (aref (symbol-name next) 0) ?:))
	    (setq args (nthcdr 2 args))
	  (widget-put widget :args args)
	  (setq args nil))))
    ;; Then Convert the widget.
    (setq type widget)
    (while type
      (let ((convert-widget (plist-get (cdr type) :convert-widget)))
	(if convert-widget
	    (setq widget (funcall convert-widget widget))))
      (setq type (get (car type) 'widget-type)))
    ;; Finally set the keyword args.
    (while keys 
      (let ((next (nth 0 keys)))
	(if (and (symbolp next) (eq (aref (symbol-name next) 0) ?:))
	    (progn 
	      (widget-put widget next (nth 1 keys))
	      (setq keys (nthcdr 2 keys)))
	  (setq keys nil))))
    ;; Convert the :value to internal format.
    (if (widget-member widget :value)
	(let ((value (widget-get widget :value)))
	  (widget-put widget
		      :value (widget-apply widget :value-to-internal value))))
    ;; Return the newly create widget.
    widget))

(defun widget-insert (&rest args)
  "Call `insert' with ARGS and make the text read only."
  (let ((inhibit-read-only t)
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	before-change-functions
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	after-change-functions
	(from (point)))
    (apply 'insert args)
    (widget-specify-text from (point))))

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(defun widget-convert-text (type from to
				 &optional button-from button-to
				 &rest args)
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  "Return a widget of type TYPE with endpoint FROM TO.
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Optional ARGS are extra keyword arguments for TYPE.
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and TO will be used as the widgets end points. If optional arguments
BUTTON-FROM and BUTTON-TO are given, these will be used as the widgets
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button end points.
Optional ARGS are extra keyword arguments for TYPE."
  (let ((widget (apply 'widget-convert type :delete 'widget-leave-text args))
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	(from (copy-marker from))
	(to (copy-marker to)))
    (widget-specify-text from to)
    (set-marker-insertion-type from t)
    (set-marker-insertion-type to nil)
    (widget-put widget :from from)
    (widget-put widget :to to)
    (when button-from
      (widget-specify-button widget button-from button-to))
    widget))

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(defun widget-convert-button (type from to &rest args)
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  "Return a widget of type TYPE with endpoint FROM TO.
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Optional ARGS are extra keyword arguments for TYPE.
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No text will be inserted to the buffer, instead the text between FROM
and TO will be used as the widgets end points, as well as the widgets
button end points."
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  (apply 'widget-convert-text type from to from to args))

(defun widget-leave-text (widget)
  "Remove markers and overlays from WIDGET and its children."
  (let ((from (widget-get widget :from))
	(to (widget-get widget :to))
	(button (widget-get widget :button-overlay))
	(field (widget-get widget :field-overlay))
	(children (widget-get widget :children)))
    (set-marker from nil)
    (set-marker to nil)
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    (when button
      (delete-overlay button))
    (when field
      (delete-overlay field))
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    (mapcar 'widget-leave-text children)))
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;;; Keymap and Commands.

(defvar widget-keymap nil
  "Keymap containing useful binding for buffers containing widgets.
Recommended as a parent keymap for modes using widgets.")

(unless widget-keymap 
  (setq widget-keymap (make-sparse-keymap))
  (define-key widget-keymap "\t" 'widget-forward)
  (define-key widget-keymap [(shift tab)] 'widget-backward)
  (define-key widget-keymap [backtab] 'widget-backward)
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  (if (string-match "XEmacs" emacs-version)
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      (progn 
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	;;Glyph support.
	(define-key widget-keymap [button1] 'widget-button1-click) 
	(define-key widget-keymap [button2] 'widget-button-click))
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    (define-key widget-keymap [down-mouse-2] 'widget-button-click))
  (define-key widget-keymap "\C-m" 'widget-button-press))

(defvar widget-global-map global-map
  "Keymap used for events the widget does not handle themselves.")
(make-variable-buffer-local 'widget-global-map)

(defvar widget-field-keymap nil
  "Keymap used inside an editable field.")

(unless widget-field-keymap 
  (setq widget-field-keymap (copy-keymap widget-keymap))
  (unless (string-match "XEmacs" (emacs-version))
    (define-key widget-field-keymap [menu-bar] 'nil))
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  (define-key widget-field-keymap "\C-k" 'widget-kill-line)
  (define-key widget-field-keymap "\M-\t" 'widget-complete)
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  (define-key widget-field-keymap "\C-m" 'widget-field-activate)
  (define-key widget-field-keymap "\C-a" 'widget-beginning-of-line)
  (define-key widget-field-keymap "\C-e" 'widget-end-of-line)
  (set-keymap-parent widget-field-keymap global-map))

(defvar widget-text-keymap nil
  "Keymap used inside a text field.")

(unless widget-text-keymap 
  (setq widget-text-keymap (copy-keymap widget-keymap))
  (unless (string-match "XEmacs" (emacs-version))
    (define-key widget-text-keymap [menu-bar] 'nil))
  (define-key widget-text-keymap "\C-a" 'widget-beginning-of-line)
  (define-key widget-text-keymap "\C-e" 'widget-end-of-line)
  (set-keymap-parent widget-text-keymap global-map))

(defun widget-field-activate (pos &optional event)
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  "Invoke the ediable field at point."
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  (interactive "@d")
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  (let ((field (get-char-property pos 'field)))
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    (if field
	(widget-apply-action field event)
      (call-interactively
       (lookup-key widget-global-map (this-command-keys))))))

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(defface widget-button-pressed-face 
  '((((class color))
     (:foreground "red"))
    (t
     (:bold t :underline t)))
  "Face used for pressed buttons."
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  :group 'widget-faces)
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(defun widget-button-click (event)
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  "Invoke button below mouse pointer."
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  (interactive "@e")
  (cond ((and (fboundp 'event-glyph)
	      (event-glyph event))
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	 (widget-glyph-click event))
	((widget-event-point event)
	 (let* ((pos (widget-event-point event))
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		(button (get-char-property pos 'button)))
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	   (if button
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	       (let* ((overlay (widget-get button :button-overlay))
		      (face (overlay-get overlay 'face))
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		      (mouse-face (overlay-get overlay 'mouse-face)))
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		 (unwind-protect
		     (let ((track-mouse t))
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		       (overlay-put overlay
				    'face 'widget-button-pressed-face)
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		       (overlay-put overlay 
				    'mouse-face 'widget-button-pressed-face)
		       (unless (widget-apply button :mouse-down-action event)
			 (while (not (button-release-event-p event))
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			   (setq event (widget-read-event)
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				 pos (widget-event-point event))
			   (if (and pos
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				    (eq (get-char-property pos 'button)
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					button))
			       (progn 
				 (overlay-put overlay 
					      'face
					      'widget-button-pressed-face)
				 (overlay-put overlay 
					      'mouse-face 
					      'widget-button-pressed-face))
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			     (overlay-put overlay 'face face)
			     (overlay-put overlay 'mouse-face mouse-face))))
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		       (when (and pos 
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				  (eq (get-char-property pos 'button) button))
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			 (widget-apply-action button event)))
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		   (overlay-put overlay 'face face)
		   (overlay-put overlay 'mouse-face mouse-face)))
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	     (let ((up t)
		   command)
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	       ;; Find the global command to run, and check whether it
	       ;; is bound to an up event.
	       (cond ((setq command	;down event
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			    (lookup-key widget-global-map [ button2 ]))
		      (setq up nil))
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		     ((setq command	;down event
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			    (lookup-key widget-global-map [ down-mouse-2 ]))
		      (setq up nil))
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		     ((setq command	;up event
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			    (lookup-key widget-global-map [ button2up ])))
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		     ((setq command	;up event
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			    (lookup-key widget-global-map [ mouse-2]))))
	       (when up
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		 ;; Don't execute up events twice.
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		 (while (not (button-release-event-p event))
		   (setq event (widget-read-event))))
	       (when command
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		 (call-interactively command))))))
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	(t
	 (message "You clicked somewhere weird."))))

(defun widget-button1-click (event)
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  "Invoke glyph below mouse pointer."
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  (interactive "@e")
  (if (and (fboundp 'event-glyph)
	   (event-glyph event))
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      (widget-glyph-click event)
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    (call-interactively (lookup-key widget-global-map (this-command-keys)))))

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(defun widget-glyph-click (event)
  "Handle click on a glyph."
  (let* ((glyph (event-glyph event))
	 (widget (glyph-property glyph 'widget))
	 (extent (event-glyph-extent event))
	 (down-glyph (or (and widget (widget-get widget :glyph-down)) glyph))
	 (up-glyph (or (and widget (widget-get widget :glyph-up)) glyph))
	 (last event))
    ;; Wait for the release.
    (while (not (button-release-event-p last))
      (if (eq extent (event-glyph-extent last))
	  (set-extent-property extent 'end-glyph down-glyph)
	(set-extent-property extent 'end-glyph up-glyph))
      (setq last (next-event event)))
    ;; Release glyph.
    (when down-glyph
      (set-extent-property extent 'end-glyph up-glyph))
    ;; Apply widget action.
    (when (eq extent (event-glyph-extent last))
      (let ((widget (glyph-property (event-glyph event) 'widget)))
	(cond ((null widget)
	       (message "You clicked on a glyph."))
	      ((not (widget-apply widget :active))
	       (message "This glyph is inactive."))
	      (t
	       (widget-apply-action widget event)))))))

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(defun widget-button-press (pos &optional event)
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  "Invoke button at POS."
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  (interactive "@d")
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  (let ((button (get-char-property pos 'button)))
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    (if button
	(widget-apply-action button event)
      (let ((command (lookup-key widget-global-map (this-command-keys))))
	(when (commandp command)
	  (call-interactively command))))))

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(defun widget-tabable-at (&optional pos)
  "Return the tabable widget at POS, or nil.
POS defaults to the value of (point)."
  (unless pos
    (setq pos (point)))
  (let ((widget (or (get-char-property (point) 'button)
		    (get-char-property (point) 'field))))
    (if widget
	(let ((order (widget-get widget :tab-order)))
	  (if order
	      (if (>= order 0)
		  widget
		nil)
	    widget))
      nil)))

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(defun widget-move (arg)
  "Move point to the ARG next field or button.
ARG may be negative to move backward."
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  (or (bobp) (> arg 0) (backward-char))
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  (let ((pos (point))
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	(number arg)
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	(old (widget-tabable-at))
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	new)
    ;; Forward.
    (while (> arg 0)
      (if (eobp)
	  (goto-char (point-min))
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	(forward-char 1))
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      (and (eq pos (point))
	   (eq arg number)
	   (error "No buttons or fields found"))
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      (let ((new (widget-tabable-at)))
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	(when new
	  (unless (eq new old)
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	    (setq arg (1- arg))
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	    (setq old new)))))
    ;; Backward.
    (while (< arg 0)
      (if (bobp)
	  (goto-char (point-max))
	(backward-char 1))
      (and (eq pos (point))
	   (eq arg number)
	   (error "No buttons or fields found"))
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      (let ((new (widget-tabable-at)))
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	(when new
	  (unless (eq new old)
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	    (setq arg (1+ arg))))))
    (let ((new (widget-tabable-at)))
      (while (eq (widget-tabable-at) new)
	(backward-char)))
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    (forward-char))
  (widget-echo-help (point))
  (run-hooks 'widget-move-hook))
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(defun widget-forward (arg)
  "Move point to the next field or button.
With optional ARG, move across that many fields."
  (interactive "p")
  (run-hooks 'widget-forward-hook)
  (widget-move arg))

(defun widget-backward (arg)
  "Move point to the previous field or button.
With optional ARG, move across that many fields."
  (interactive "p")
  (run-hooks 'widget-backward-hook)
  (widget-move (- arg)))

(defun widget-beginning-of-line ()
  "Go to beginning of field or beginning of line, whichever is first."
  (interactive)
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  (let* ((field (widget-field-find (point)))
	 (start (and field (widget-field-start field))))
    (if (and start (not (eq start (point))))
	(goto-char start)
      (call-interactively 'beginning-of-line))))
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(defun widget-end-of-line ()
  "Go to end of field or end of line, whichever is first."
  (interactive)
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  (let* ((field (widget-field-find (point)))
	 (end (and field (widget-field-end field))))
    (if (and end (not (eq end (point))))
	(goto-char end)
      (call-interactively 'end-of-line))))
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(defun widget-kill-line ()
  "Kill to end of field or end of line, whichever is first."
  (interactive)
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  (let* ((field (widget-field-find (point)))
	 (newline (save-excursion (forward-line 1) (point)))
	 (end (and field (widget-field-end field))))
    (if (and field (> newline end))
	(kill-region (point) end)
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      (call-interactively 'kill-line))))

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(defcustom widget-complete-field (lookup-key global-map "\M-\t")
  "Default function to call for completion inside fields."
  :options '(ispell-complete-word complete-tag lisp-complete-symbol)
  :type 'function
  :group 'widgets)

(defun widget-complete ()
  "Complete content of editable field from point.
When not inside a field, move to the previous button or field."
  (interactive)
  (let ((field (widget-field-find (point))))
    (if field
	(widget-apply field :complete)
      (error "Not in an editable field"))))

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;;; Setting up the buffer.

(defvar widget-field-new nil)
;; List of all newly created editable fields in the buffer.
(make-variable-buffer-local 'widget-field-new)

(defvar widget-field-list nil)
;; List of all editable fields in the buffer.
(make-variable-buffer-local 'widget-field-list)

(defun widget-setup ()
  "Setup current buffer so editing string widgets works."
  (let ((inhibit-read-only t)
	(after-change-functions nil)
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	before-change-functions
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	field)
    (while widget-field-new
      (setq field (car widget-field-new)
	    widget-field-new (cdr widget-field-new)
	    widget-field-list (cons field widget-field-list))
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      (let ((from (car (widget-get field :field-overlay)))
	    (to (cdr (widget-get field :field-overlay))))
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	(widget-specify-field field 
			      (marker-position from) (marker-position to))
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	(set-marker from nil)
	(set-marker to nil))))
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  (widget-clear-undo)
  ;; We need to maintain text properties and size of the editing fields.
  (make-local-variable 'after-change-functions)
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  (setq after-change-functions
	(if widget-field-list '(widget-after-change) nil))
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  (when widget-field-use-before-change
    (make-local-variable 'before-change-functions)
    (setq before-change-functions
	  (if widget-field-list '(widget-before-change) nil))))
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(defvar widget-field-last nil)
;; Last field containing point.
(make-variable-buffer-local 'widget-field-last)

(defvar widget-field-was nil)
;; The widget data before the change.
(make-variable-buffer-local 'widget-field-was)

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(defun widget-field-buffer (widget)
  "Return the start of WIDGET's editing field."
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  (let ((overlay (widget-get widget :field-overlay)))
    (and overlay (overlay-buffer overlay))))
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(defun widget-field-start (widget)
  "Return the start of WIDGET's editing field."
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  (let ((overlay (widget-get widget :field-overlay)))
    (and overlay (overlay-start overlay))))
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(defun widget-field-end (widget)
  "Return the end of WIDGET's editing field."
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  (let ((overlay (widget-get widget :field-overlay)))
    ;; Don't subtract one if local-map works at the end of the overlay.
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    (and overlay (if widget-field-add-space
		     (1- (overlay-end overlay))
		   (overlay-end overlay)))))
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(defun widget-field-find (pos)
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  "Return the field at POS.
Unlike (get-char-property POS 'field) this, works with empty fields too."
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  (let ((fields widget-field-list)
	field found)
    (while fields
      (setq field (car fields)
	    fields (cdr fields))
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      (let ((start (widget-field-start field))
	    (end (widget-field-end field)))
	(when (and (<= start pos) (<= pos end))
	  (when found
	    (debug "Overlapping fields"))
	  (setq found field))))
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    found))

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(defun widget-before-change (from &rest ignore)
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  ;; This is how, for example, a variable changes its state to `modified'.
  ;; when it is being edited.
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  (condition-case nil
      (let ((field (widget-field-find from)))
	(widget-apply field :notify field))
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    (error (debug "Before Change"))))
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(defun widget-after-change (from to old)
  ;; Adjust field size and text properties.
  (condition-case nil
      (let ((field (widget-field-find from))
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	    (other (widget-field-find to)))
	(when field
	  (unless (eq field other)
	    (debug "Change in different fields"))
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	  (let ((size (widget-get field :size))
		(secret (widget-get field :secret)))
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	    (when size 
	      (let ((begin (widget-field-start field))
		    (end (widget-field-end field)))
		(cond ((< (- end begin) size)
		       ;; Field too small.
		       (save-excursion
			 (goto-char end)
			 (insert-char ?\  (- (+ begin size) end))))
		      ((> (- end begin) size)
		       ;; Field too large and
		       (if (or (< (point) (+ begin size))
			       (> (point) end))
			   ;; Point is outside extra space.
			   (setq begin (+ begin size))
			 ;; Point is within the extra space.
			 (setq begin (point)))
		       (save-excursion
			 (goto-char end)
			 (while (and (eq (preceding-char) ?\ )
				     (> (point) begin))
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			   (delete-backward-char 1)))))))
	    (when secret
	      (let ((begin (widget-field-start field))
		    (end (widget-field-end field)))
		(when size 
		  (while (and (> end begin)
			      (eq (char-after (1- end)) ?\ ))
		    (setq end (1- end))))
		(while (< begin end)
		  (let ((old (char-after begin)))
		    (unless (eq old secret)
		      (subst-char-in-region begin (1+ begin) old secret)
		      (put-text-property begin (1+ begin) 'secret old))
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		    (setq begin (1+ begin)))))))
	  (widget-apply field :notify field)))
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    (error (debug "After Change"))))
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;;; Widget Functions
;;
;; These functions are used in the definition of multiple widgets. 

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(defun widget-parent-action (widget &optional event)
  "Tell :parent of WIDGET to handle the :action.
Optional EVENT is the event that triggered the action."
  (widget-apply (widget-get widget :parent) :action event))

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(defun widget-children-value-delete (widget)
  "Delete all :children and :buttons in WIDGET."
  (mapcar 'widget-delete (widget-get widget :children))
  (widget-put widget :children nil)
  (mapcar 'widget-delete (widget-get widget :buttons))
  (widget-put widget :buttons nil))

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(defun widget-children-validate (widget)
  "All the :children must be valid."
  (let ((children (widget-get widget :children))
	child found)
    (while (and children (not found))
      (setq child (car children)
	    children (cdr children)
	    found (widget-apply child :validate)))
    found))

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(defun widget-types-convert-widget (widget)
  "Convert :args as widget types in WIDGET."
  (widget-put widget :args (mapcar 'widget-convert (widget-get widget :args)))
  widget)

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(defun widget-value-convert-widget (widget)
  "Initialize :value from :args in WIDGET."
  (let ((args (widget-get widget :args)))
    (when args 
      (widget-put widget :value (car args))
      ;; Don't convert :value here, as this is done in `widget-convert'.
      ;; (widget-put widget :value (widget-apply widget
      ;;  				      :value-to-internal (car args)))
      (widget-put widget :args nil)))
  widget)

(defun widget-value-value-get (widget)
  "Return the :value property of WIDGET."
  (widget-get widget :value))

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;;; The `default' Widget.

(define-widget 'default nil
  "Basic widget other widgets are derived from."
  :value-to-internal (lambda (widget value) value)
  :value-to-external (lambda (widget value) value)
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  :button-prefix 'widget-button-prefix
  :button-suffix 'widget-button-suffix
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  :complete 'widget-default-complete				       
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  :create 'widget-default-create
  :indent nil
  :offset 0
  :format-handler 'widget-default-format-handler
  :button-face-get 'widget-default-button-face-get 
  :sample-face-get 'widget-default-sample-face-get 
  :delete 'widget-default-delete
  :value-set 'widget-default-value-set
  :value-inline 'widget-default-value-inline
  :menu-tag-get 'widget-default-menu-tag-get
  :validate (lambda (widget) nil)
  :active 'widget-default-active
  :activate 'widget-specify-active
  :deactivate 'widget-default-deactivate
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  :mouse-down-action (lambda (widget event) nil)
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  :action 'widget-default-action
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  :notify 'widget-default-notify
  :prompt-value 'widget-default-prompt-value)
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(defun widget-default-complete (widget)
  "Call the value of the :complete-function property of WIDGET.
If that does not exists, call the value of `widget-complete-field'."
  (let ((fun (widget-get widget :complete-function)))
    (call-interactively (or fun widget-complete-field))))

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(defun widget-default-create (widget)
  "Create WIDGET at point in the current buffer."
  (widget-specify-insert
   (let ((from (point))
	 button-begin button-end
	 sample-begin sample-end
	 doc-begin doc-end
	 value-pos)
     (insert (widget-get widget :format))
     (goto-char from)
     ;; Parse escapes in format.
     (while (re-search-forward "%\\(.\\)" nil t)
       (let ((escape (aref (match-string 1) 0)))
	 (replace-match "" t t)
	 (cond ((eq escape ?%)
		(insert "%"))
	       ((eq escape ?\[)
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		(setq button-begin (point))
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		(insert (widget-get-indirect widget :button-prefix)))
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	       ((eq escape ?\])
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		(insert (widget-get-indirect widget :button-suffix))
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		(setq button-end (point)))
	       ((eq escape ?\{)
		(setq sample-begin (point)))
	       ((eq escape ?\})
		(setq sample-end (point)))
	       ((eq escape ?n)
		(when (widget-get widget :indent)
		  (insert "\n")
		  (insert-char ?  (widget-get widget :indent))))
	       ((eq escape ?t)
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		(let ((glyph (widget-get widget :tag-glyph))
		      (tag (widget-get widget :tag)))
		  (cond (glyph 
			 (widget-glyph-insert widget (or tag "image") glyph))
			(tag
			 (insert tag))
			(t
			 (let ((standard-output (current-buffer)))
			   (princ (widget-get widget :value)))))))
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	       ((eq escape ?d)
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		(let ((doc (widget-get widget :doc)))
		  (when doc
		    (setq doc-begin (point))
		    (insert doc)
		    (while (eq (preceding-char) ?\n)
		      (delete-backward-char 1))
		    (insert "\n")
		    (setq doc-end (point)))))
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	       ((eq escape ?v)
		(if (and button-begin (not button-end))
		    (widget-apply widget :value-create)
		  (setq value-pos (point))))
	       (t 
		(widget-apply widget :format-handler escape)))))
     ;; Specify button, sample, and doc, and insert value.
     (and button-begin button-end
	  (widget-specify-button widget button-begin button-end))
     (and sample-begin sample-end
	  (widget-specify-sample widget sample-begin sample-end))
     (and doc-begin doc-end
	  (widget-specify-doc widget doc-begin doc-end))
     (when value-pos
       (goto-char value-pos)
       (widget-apply widget :value-create)))
   (let ((from (copy-marker (point-min)))
	 (to (copy-marker (point-max))))
     (widget-specify-text from to)
     (set-marker-insertion-type from t)
     (set-marker-insertion-type to nil)
     (widget-put widget :from from)
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     (widget-put widget :to to)))
  (widget-clear-undo))
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(defun widget-default-format-handler (widget escape)
  ;; We recognize the %h escape by default.
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  (let* ((buttons (widget-get widget :buttons)))
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    (cond ((eq escape ?h)
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	   (let* ((doc-property (widget-get widget :documentation-property))
		  (doc-try (cond ((widget-get widget :doc))
				 ((symbolp doc-property)
				  (documentation-property 
				   (widget-get widget :value)
				   doc-property))
				 (t
				  (funcall doc-property
					   (widget-get widget :value)))))
		  (doc-text (and (stringp doc-try)
				 (> (length doc-try) 1)
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				 doc-try))
		  (doc-indent (widget-get widget :documentation-indent)))
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	     (when doc-text
	       (and (eq (preceding-char) ?\n)
		    (widget-get widget :indent)
		    (insert-char ?  (widget-get widget :indent)))
	       ;; The `*' in the beginning is redundant.
	       (when (eq (aref doc-text  0) ?*)
		 (setq doc-text (substring doc-text 1)))
	       ;; Get rid of trailing newlines.
	       (when (string-match "\n+\\'" doc-text)
		 (setq doc-text (substring doc-text 0 (match-beginning 0))))
	       (push (widget-create-child-and-convert
		      widget 'documentation-string
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		      :indent (cond ((numberp doc-indent )
				     doc-indent)
				    ((null doc-indent)