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diff --git a/lisp/minibuf-eldef.el b/lisp/minibuf-eldef.el
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+;;; minibuf-eldef.el --- Only show defaults in prompts when applicable
+;;
+;; Copyright (C) 2000 Free Software Foundation, Inc.
+;;
+;; Author: Miles Bader <miles@gnu.org>
+;; Keywords: convenience
+
+;; 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:
+;;
+;; Defines the mode `minibuffer-electric-default-mode'.
+;;
+;; When active, minibuffer prompts that show a default value only show
+;; the default when it's applicable -- that is, when hitting RET would
+;; yield the default value.  If the user modifies the input such that
+;; hitting RET would enter a non-default value, the prompt is modified
+;; to remove the default indication (which is restored if the input is
+;; ever restore to the match the initial input).
+
+;;; Code:
+
+(defvar minibuffer-default-in-prompt-regexps
+  '(("\\( (default\\>.*)\\):? \\'" . 1))
+  "*A list of regexps matching the parts of minibuffer prompts showing defaults.
+When `minibuffer-electric-default-mode' is active, these regexps are
+used to identify the portions of prompts to elide.
+
+Each entry is either a string, which should be a regexp matching the
+default portion of the prompt, or a cons cell, who's car is a regexp
+matching the default part of the prompt, and who's cdr indicates the
+regexp subexpression that matched.")
+
+
+;;; Internal variables
+
+;; A list of minibuffers to which we've added a post-command-hook.
+(defvar minibuf-eldef-frobbed-minibufs nil)
+      
+;;; The following are all local variables in the minibuffer
+
+;; Input pre-inserted into the minibuffer before the user can edit it.
+(defvar minibuf-eldef-initial-input)
+(make-variable-buffer-local 'minibuf-eldef-initial-input)
+;; and the length of the buffer with it inserted.
+(defvar minibuf-eldef-initial-buffer-length)
+(make-variable-buffer-local 'minibuf-eldef-initial-buffer-length)
+
+;; True if the current minibuffer prompt contains the default spec.
+(defvar minibuf-eldef-showing-default-in-prompt)
+(make-variable-buffer-local 'minibuf-eldef-showing-default-in-prompt)
+
+;; An overlay covering the default portion of the prompt
+(defvar minibuf-eldef-overlay)
+(make-variable-buffer-local 'minibuf-eldef-overlay)
+
+
+;;; Hook functions
+
+;; This function goes on minibuffer-setup-hook
+(defun minibuf-eldef-setup-minibuffer ()
+  "Set up a minibuffer for `minibuffer-electric-default-mode'.
+The prompt and initial input should already have been inserted."
+  (let ((prompt (field-string-no-properties (point-min)))
+	(regexps minibuffer-default-in-prompt-regexps)
+	(match nil)
+	(inhibit-point-motion-hooks t))
+    (save-excursion
+      (save-restriction
+	;; Narrow to only the prompt
+	(goto-char (point-min))
+	(narrow-to-region (point) (field-end))
+	;; See the prompt contains a default input indicator
+	(while regexps
+	  (setq match (pop regexps))
+	  (if (re-search-forward (if (stringp match) match (car match)) nil t)
+	      (setq regexps nil)
+	    (setq match nil)))))
+    (if (not match)
+	;; Nope, so just make sure our post-command-hook isn't left around.
+	(remove-hook 'post-command-hook #'minibuf-eldef-update-minibuffer t)
+      ;; Yup; set things up so we can frob the prompt as the state of
+      ;; the input string changes.
+      (setq match (if (consp match) (cdr match) 0))
+      (setq minibuf-eldef-overlay
+	    (make-overlay (match-beginning match) (match-end match)))
+      (setq minibuf-eldef-showing-default-in-prompt t)
+      (setq minibuf-eldef-initial-input
+	    (field-string-no-properties (point-max)))
+      (setq minibuf-eldef-initial-buffer-length (point-max))
+      (add-to-list 'minibuf-eldef-frobbed-minibufs (current-buffer))
+      (add-hook 'post-command-hook #'minibuf-eldef-update-minibuffer nil t))))
+
+;; post-command-hook to swap prompts when necessary
+(defun minibuf-eldef-update-minibuffer ()
+  "Update a minibuffer's prompt to include a default only when applicable.
+This is intended to be used as a minibuffer post-command-hook for
+`minibuffer-electric-default-mode'; the minibuffer should have already
+been set up by `minibuf-eldef-setup-minibuffer'."
+  (unless (eq minibuf-eldef-showing-default-in-prompt
+	      (and (= (point-max) minibuf-eldef-initial-buffer-length)
+		   (string-equal (field-string-no-properties (point-max))
+				 minibuf-eldef-initial-input)))
+    ;; swap state
+    (setq minibuf-eldef-showing-default-in-prompt
+	  (not minibuf-eldef-showing-default-in-prompt))
+    (cond (minibuf-eldef-showing-default-in-prompt
+	   (overlay-put minibuf-eldef-overlay 'invisible nil)
+	   (overlay-put minibuf-eldef-overlay 'intangible nil))
+	  (t
+	   (overlay-put minibuf-eldef-overlay 'invisible t)
+	   (overlay-put minibuf-eldef-overlay 'intangible t)))))
+
+
+;;; Note this definition must be at the end of the file, because
+;;; `define-minor-mode' actually calls the mode-function if the
+;;; associated variable is non-nil, which requires that all needed
+;;; functions be already defined.  [This is arguably a bug in d-m-m]
+;;;###autoload
+(define-minor-mode minibuffer-electric-default-mode
+  "Toggle Minibuffer Electric Default mode
+When active, minibuffer prompts that show a default value only show the
+default when it's applicable -- that is, when hitting RET would yield
+the default value.  If the user modifies the input such that hitting RET
+would enter a non-default value, the prompt is modified to remove the
+default indication.
+
+With prefix argument ARG, turn on if positive, otherwise off.
+Returns non-nil if the new state is enabled."
+  :global t
+  :group 'minibuffer
+  (if minibuffer-electric-default-mode
+      ;; Enable the mode
+      (add-hook 'minibuffer-setup-hook 'minibuf-eldef-setup-minibuffer)
+    ;; Disable the mode
+    (remove-hook 'minibuffer-setup-hook 'minibuf-eldef-setup-minibuffer)
+    ;; Remove our entry from any post-command-hook variable's it's still in
+    (dolist (minibuf minibuf-eldef-frobbed-minibufs)
+      (with-current-buffer minibuf
+	(remove-hook 'post-command-hook #'minibuf-eldef-update-minibuffer t)))
+    (setq minibuf-eldef-frobbed-minibufs nil)))
+
+
+(provide 'minibuf-eldef)
+
+;;; minibuf-eldef.el ends here