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+;;; fringe.el --- change fringes appearance in various ways
+
+;; Copyright (C) 2002 Free Software Foundation, Inc.
+
+;; Author: Simon Josefsson <simon@josefsson.org>
+;; Maintainer: FSF
+;; Keywords: frames
+
+;; 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.
+
+;;; Commentary:
+
+;; This file contains helpful functions for customizing the appearance
+;; of the fringe.
+
+;; The code is influenced by scroll-bar.el and avoid.el.  The author
+;; gratefully acknowledge comments and suggestions made by Miles
+;; Bader, Eli Zaretski, Richard Stallman, Pavel Janík and others which
+;; improved this package.
+
+;;; Code:
+
+(defvar fringe-mode)
+
+(defun set-fringe-mode-1 (ignore value)
+  "Call `set-fringe-mode' with VALUE.
+See `fringe-mode' for valid values and their effect.
+This is usually invoked when setting `fringe-mode' via customize."
+  (set-fringe-mode value))
+
+(defun set-fringe-mode (value)
+  "Set `fringe-mode' to VALUE and put the new value into effect.
+See `fringe-mode' for possible values and their effect."
+  (setq fringe-mode value)
+
+  ;; Apply it to default-frame-alist.
+  (let ((parameter (assq 'left-fringe default-frame-alist)))
+    (if (consp parameter)
+	(setcdr parameter fringe-mode)
+      (setq default-frame-alist
+	    (cons (cons 'left-fringe (if (consp fringe-mode)
+					 (car fringe-mode)
+				       fringe-mode))
+		  default-frame-alist))))
+  (let ((parameter (assq 'right-fringe default-frame-alist)))
+    (if (consp parameter)
+	(setcdr parameter fringe-mode)
+      (setq default-frame-alist
+	    (cons (cons 'right-fringe (if (consp fringe-mode)
+					  (cdr fringe-mode)
+					fringe-mode))
+		  default-frame-alist))))
+
+  ;; Apply it to existing frames.
+  (let ((frames (frame-list)))
+    (while frames
+      (modify-frame-parameters
+       (car frames)
+       (list (cons 'left-fringe (if (consp fringe-mode)
+				    (car fringe-mode)
+				  fringe-mode))
+	     (cons 'right-fringe (if (consp fringe-mode)
+				     (cdr fringe-mode)
+				   fringe-mode))))
+      (setq frames (cdr frames)))))
+
+(defcustom fringe-mode nil
+  "*Specify appearance of fringes on all frames.
+This variable can be nil (the default) meaning the fringes should have
+the default width (8 pixels), it can be an integer value specifying
+the width of both left and right fringe (where 0 means no fringe), or
+a cons cell where car indicates width of left fringe and cdr indicates
+width of right fringe (where again 0 can be used to indicate no
+fringe).
+To set this variable in a Lisp program, use `set-fringe-mode' to make
+it take real effect.
+Setting the variable with a customization buffer also takes effect.
+If you only want to modify the appearance of the fringe in one frame,
+you can use the interactive function `toggle-fringe'"
+  :type '(choice (const :tag "Default width" nil)
+		 (const :tag "No fringes" 0)
+		 (const :tag "Only right" (0 . nil))
+		 (const :tag "Only left" (nil . 0))
+		 (const :tag "Half width" (5 . 5))
+		 (integer :tag "Specific width")
+		 (cons :tag "Different left/right sizes"
+		       (integer :tag "Left width")
+		       (integer :tag "Right width")))
+  :group 'frames
+  :require 'fringe
+  :set 'set-fringe-mode-1)
+
+(defun fringe-query-style (&optional all-frames)
+  "Query user for fringe style.
+Returns values suitable for left-fringe and right-fringe frame parameters.
+If ALL-FRAMES, the negation of the fringe values in
+`default-frame-alist' is used when user enters the empty string.
+Otherwise the negation of the fringe value in the currently selected
+frame parameter is used."
+  (let ((mode (intern (completing-read
+		       "Select fringe mode for all frames (SPACE for list): "
+		       '(("none") ("default") ("left-only")
+			 ("right-only") ("half"))
+		       nil t))))
+    (cond ((eq mode 'none) 0)
+	  ((eq mode 'default) nil)
+	  ((eq mode 'left-only) '(nil . 0))
+	  ((eq mode 'right-only) '(0 . nil))
+	  ((eq mode 'half) '(5 . 5))
+	  ((eq mode (intern ""))
+	   (if (eq 0 (cdr (assq 'left-fringe
+				(if all-frames
+				    default-frame-alist
+				  (frame-parameters (selected-frame))))))
+	       nil
+	     0)))))
+
+;;;###autoload
+(defun fringe-mode (&optional mode)
+  "Toggle appearance of fringes on all frames.
+Valid values for MODE include `none', `default', `left-only',
+`right-only' and `half'.  MODE can also be a cons cell where the
+integer in car will be used as left fringe width and the integer in
+cdr will be used as right fringe width. If MODE is not specified, the
+user is queried.
+It applies to all frames that exist and frames to be created in the
+future.
+If you want to set appearance of fringes on the selected frame only,
+see `set-fringe-style'."
+  (interactive (list (fringe-query-style 'all-frames)))
+  (set-fringe-mode mode))
+
+;;;###autoload
+(defun set-fringe-style (&optional mode)
+  "Set appearance of fringes on selected frame.
+Valid values for MODE include `none', `default', `left-only',
+`right-only' and `half'.  MODE can also be a cons cell where the
+integer in car will be used as left fringe width and the integer in
+cdr will be used as right fringe width. If MODE is not specified, the
+user is queried.
+If you want to set appearance of fringes on all frames, see `fringe-mode'."
+  (interactive (list (fringe-query-style)))
+  (modify-frame-parameters
+   (selected-frame)
+   (list (cons 'left-fringe (if (consp mode) (car mode) mode))
+	 (cons 'right-fringe (if (consp mode) (cdr mode) mode)))))
+
+(provide 'fringe)
+
+;;; fringe.el ends here