;;; pending-del.el --- pending delete selection

;;; Copyright (C) 1992 Free Software Foundation, Inc.

;; Author: Matthieu Devin <devin@lucid.com>
;; Created: 14 Jul 92
;; Last change  18-Feb-93, devin.

;;; 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, 675 Mass Ave, Cambridge, MA 02139, USA.

;;; Commentary:

;;; This file makes the active region be pending delete, meaning that
;;; text inserted while the region is active will replace the region contents.
;;; This is a popular behavior of personal computers text editors.

;;; Code:

(defvar pending-delete-mode t
  "*Non-nil means Pending Delete mode is enabled.
In Pending Delete mode, when a region is highlighted,
insertion commands first delete the region and then insert.")

(defun delete-active-region (&optional killp)
  (if killp
      (kill-region (point) (mark))
    (delete-region (point) (mark)))
  (setq mark-active nil)
  (run-hooks 'deactivate-mark-hook)
  t)

(defun pending-delete-pre-hook ()
  (if (and pending-delete-mode
	   (not buffer-read-only)
	   transient-mark-mode mark-active)
      (let ((type (and (symbolp this-command)
		       (get this-command 'pending-delete))))
	(cond ((eq type 'kill)
	       (delete-active-region t))
	      ((eq type 'supersede)
	       (if (delete-active-region ())
		   (setq this-command '(lambda () (interactive)))))
	      (type
	       (delete-active-region ()))))))

(add-hook 'pre-command-hook 'pending-delete-pre-hook)

(put 'self-insert-command 'pending-delete t)

(put 'yank 'pending-delete t)
(put 'x-yank-clipboard-selection 'pending-delete t)

(put 'delete-backward-char 'pending-delete 'supersede)
(put 'backward-delete-char-untabify 'pending-delete 'supersede)
(put 'delete-char 'pending-delete 'supersede)

(put 'newline-and-indent 'pending-delete 't)
(put 'newline 'pending-delete t)
(put 'open-line 'pending-delete t)

(defun pending-delete-mode (arg)
  "Toggle the state of pending-delete mode.
When ON, typed text replaces the selection if the selection is active.
When OFF, typed text is just inserted at point."
  (interactive "P")
  (setq pending-delete-mode
	(if (null arg) (not pending-delete-mode)
	  (> (prefix-numeric-value arg) 0)))
  (set-buffer-modified-p (buffer-modified-p))) ;No-op, but updates mode line.

;; This new definition of control-G makes the first control-G disown the 
;; selection and the second one signal a QUIT.
;; This is very useful for cancelling a selection in the minibuffer without 
;; aborting the minibuffer.
;; It has actually nothing to do with pending-delete but its more necessary
;; with pending delete because pending delete users use the selection more.
(defun keyboard-quit ()
  "Signal a `quit' condition.
During execution of Lisp code, this character causes a quit directly.
At top-level, as an editor command, this simply beeps.
In Transient Mark mode, if the mark is active, just deactivate it."
  (interactive)
  (if (and transient-mark-mode mark-active)
      (progn
	;; Don't beep if just deactivating the region.
	(setq mark-active nil)
	(run-hooks 'deactivate-mark-hook))
    (signal 'quit nil)))

(defun minibuffer-keyboard-quit ()
  "Abort recursive edit.
In Transient Mark mode, if the mark is active, just deactivate it."
  (interactive)
  (if (and transient-mark-mode mark-active)
      (progn
	;; Don't beep if just deactivating the region.
	(setq mark-active nil)
	(run-hooks 'deactivate-mark-hook))
    (abort-recursive-edit)))

(define-key minibuffer-local-map "\C-g" 'minibuffer-keyboard-quit) 

(provide 'pending-del)

;;; pending-del.el ends here