;;; winner.el  --- Restore window configuration (or switch buffer)

;; Copyright (C) 1997, 1998 Free Software Foundation. Inc.

;; Author: Ivar Rummelhoff <ivarr@ifi.uio.no>
;; Maintainer: Ivar Rummelhoff <ivarr@ifi.uio.no>
;; Created: 27 Feb 1997
;; Keywords: extensions, windows

;; 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:

;; Winner mode is a global minor mode that when turned on records
;; changes in window configuration.  This way the changes can be
;; "undone" using the function `winner-undo'.  By default this one is
;; bound to the key sequence ctrl-x left.  If you change your mind
;; (while undoing), you can press ctrl-x right (calling
;; `winner-redo').  Unlike the normal undo, you may have to skip
;; through several identical window configurations in order to find
;; the one you want.  This is a bug due to some techical limitations
;; in Emacs and can maybe be fixed in the future.
;; 
;; In addition to this I have added `winner-switch' which is a program
;; that switches to other buffers without disturbing Winner mode.  If
;; you bind this command to a key sequence, you may step through all
;; your buffers (except the ones mentioned in `winner-skip-buffers' or
;; matched by `winner-skip-regexps').  With a numeric prefix argument
;; skip several buffers at a time.

;;; Code:

(require 'cl)
(require 'ring)

(defgroup winner nil
  "Restoring window configurations."
  :group 'windows)

(defcustom winner-mode nil
  "Toggle winner-mode.
You must modify via \\[customize] for this variable to have an effect."
  :set (lambda (symbol value)
	 (winner-mode (or value 0)))
  :initialize 'custom-initialize-default
  :type 'boolean
  :group 'winner
  :require 'winner)

(defcustom winner-dont-bind-my-keys nil
  "If non-nil: Do not use `winner-mode-map' in Winner mode."
  :type 'boolean
  :group 'winner)

(defvar winner-ring-size 100
  "Maximum number of stored window configurations per frame.")

(defcustom winner-skip-buffers
  '("*Messages*",
    "*Compile-Log*",
    ".newsrc-dribble",
    "*Completions*",
    "*Buffer list*")
  "Exclude these buffer names from any \(Winner switch\) list of buffers."
  :type '(repeat string)
  :group 'winner)

(defcustom winner-skip-regexps '("^ ")
  "Winner excludes buffers with names matching any of these regexps.
They are not included in any Winner mode list of buffers.

By default `winner-skip-regexps' is set to \(\"^ \"\),
which excludes \"invisible buffers\"."
  :type '(repeat regexp)
  :group 'winner)

(defvar winner-ring-alist nil)

(defsubst winner-ring (frame)
  (or (cdr (assq frame winner-ring-alist))
      (progn
	(push (cons frame (make-ring winner-ring-size))
	      winner-ring-alist)
	(cdar winner-ring-alist))))

(defvar winner-modified-list nil)

(defun winner-change-fun ()
  (or (memq (selected-frame) winner-modified-list)
      (push (selected-frame) winner-modified-list)))

(defun winner-save-new-configurations ()
  (while winner-modified-list
    (ring-insert
     (winner-ring (car winner-modified-list))
     (current-window-configuration (pop winner-modified-list)))))

(defun winner-set (conf)
  (set-window-configuration conf)
  (if (eq (selected-window) (minibuffer-window))
      (other-window 1)))


;;; Winner mode  (a minor mode)

(defcustom winner-mode-hook nil
  "Functions to run whenever Winner mode is turned on."
  :type 'hook
  :group winner)

(defvar winner-mode-leave-hook nil
  "Functions to run whenever Winner mode is turned off."
  :type 'hook
  :group winner)

(defvar winner-mode-map nil "Keymap for Winner mode.")

;;;###autoload
(defun winner-mode (&optional arg)
  "Toggle Winner mode.
With arg, turn Winner mode on if and only if arg is positive."
  (interactive "P")
  (let ((on-p (if arg (> (prefix-numeric-value arg) 0)
		(not winner-mode))))
    (cond
     ;; Turn mode on
     (on-p 
      (setq winner-mode t)
      (add-hook 'window-configuration-change-hook 'winner-change-fun)
      (add-hook 'post-command-hook 'winner-save-new-configurations)
      (setq winner-modified-list (frame-list))
      (winner-save-new-configurations)
      (run-hooks 'winner-mode-hook))
     ;; Turn mode off
     (winner-mode
      (setq winner-mode nil)
      (run-hooks 'winner-mode-leave-hook)))
    (force-mode-line-update)))

;; Inspired by undo (simple.el)

(defvar winner-pending-undo-ring nil)

(defvar winner-undo-counter nil)

(defun winner-undo (arg)
  "Switch back to an earlier window configuration saved by Winner mode.
In other words, \"undo\" changes in window configuration.
With prefix arg, undo that many levels."
  (interactive "p")
  (cond
   ((not winner-mode) (error "Winner mode is turned off"))
   ((eq (selected-window) (minibuffer-window))
    (error "No winner undo from minibuffer."))
   (t (setq this-command t)
      (if (eq last-command 'winner-undo)
	  ;; This was no new window configuration after all.
	  (ring-remove winner-pending-undo-ring 0)
	(setq winner-pending-undo-ring (winner-ring (selected-frame)))
	(setq winner-undo-counter 0))
      (winner-undo-more (or arg 1))
      (message "Winner undo (%d)!" winner-undo-counter)
      (setq this-command 'winner-undo))))

(defun winner-undo-more (count)
  "Undo N window configuration changes beyond what was already undone.
Call `winner-undo-start' to get ready to undo recent changes,
then call `winner-undo-more' one or more times to undo them."
  (let ((len (ring-length winner-pending-undo-ring)))
    (incf winner-undo-counter count)
    (if (>= winner-undo-counter len)
	(error "No further window configuration undo information")
      (winner-set
       (ring-ref winner-pending-undo-ring
		 winner-undo-counter)))))

(defun winner-redo ()
  "Restore a more recent window configuration saved by Winner mode."
  (interactive)
  (cond
   ((eq last-command 'winner-undo)
    (ring-remove winner-pending-undo-ring 0)
    (winner-set
     (ring-remove winner-pending-undo-ring 0))
    (or (eq (selected-window) (minibuffer-window))
	(message "Winner undid undo!")))
   (t (error "Previous command was not a winner-undo"))))

;;; Winner switch

(defun winner-switch-buffer-list ()
  (loop for buf in (buffer-list)
	for name = (buffer-name buf)
	unless (or (eq (current-buffer) buf)
		   (member name winner-skip-buffers)
		   (loop for regexp in winner-skip-regexps
			 if (string-match regexp name) return t
			 finally return nil))
	collect name))
  
(defvar winner-switch-list nil)

(defun winner-switch (count)
  "Step through your buffers without disturbing `winner-mode'.
`winner-switch' does not consider buffers mentioned in the list
`winner-skip-buffers' or matched by `winner-skip-regexps'."
  (interactive "p")
  (decf count)
  (setq this-command t)
  (cond
   ((eq last-command 'winner-switch)
    (if winner-mode (ring-remove (winner-ring (selected-frame)) 0))
    (bury-buffer (current-buffer))
    (mapcar 'bury-buffer winner-switch-list))
   (t (setq winner-switch-list (winner-switch-buffer-list))))
  (setq winner-switch-list (nthcdr count winner-switch-list))
  (or winner-switch-list
      (setq winner-switch-list (winner-switch-buffer-list))
      (error "No more buffers"))
  (switch-to-buffer (pop winner-switch-list))
  (message (concat "Winner: [%s] "
		   (mapconcat 'identity winner-switch-list " "))
	   (buffer-name))
  (setq this-command 'winner-switch))

;;;; To be evaluated when the package is loaded:

(unless winner-mode-map
  (setq winner-mode-map (make-sparse-keymap))
  (define-key winner-mode-map [?\C-x left]  'winner-undo)
  (define-key winner-mode-map [?\C-x right] 'winner-redo))

(unless (or (assq 'winner-mode minor-mode-map-alist)
	    winner-dont-bind-my-keys)
  (push (cons 'winner-mode winner-mode-map)
	minor-mode-map-alist))

(unless (assq 'winner-mode minor-mode-alist)
  (push '(winner-mode " Win") minor-mode-alist))

(provide 'winner)

;;; winner.el ends here