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;;; pointback.el --- Restore window points when returning to buffers
;; Copyright (C) 2009 Markus Triska
;; Author: Markus Triska <markus.triska@gmx.at>
;; Keywords: convenience
;; This program 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 3 of the License, or
;; (at your option) any later version.
;; This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
;; When you have two windows X and Y showing different sections of the
;; same buffer B, then switch to a different buffer in X, and then
;; show B in X again, the new point in X will be the same as in Y.
;; With pointback-mode, window points are preserved instead, and point
;; will be where it originally was in X for B when you return to B.
;; Use M-x pointback-mode RET to enable pointback-mode for a buffer.
;; Use M-x global-pointback-mode RET to enable it for all buffers.
;;; Code:
(require 'assoc)
(defconst pointback-version "0.2")
(defvar pointback-windows nil
"Association list of windows to buffers and window points.")
(defun pointback-store-point ()
"Save window point and start for the current buffer of the
selected window."
(sit-for 0) ; redisplay to update window-start
(let* ((buffers (cdr (assq (selected-window) pointback-windows)))
(b (assq (current-buffer) buffers))
(p (cons (point) (window-start))))
(if b
(setcdr b p)
(let ((current (cons (current-buffer) p)))
(aput 'pointback-windows (selected-window) (cons current buffers))))))
(defun pointback-restore ()
"Restore previously stored window point for the selected window."
(let* ((buffers (cdr (assq (selected-window) pointback-windows)))
(b (assq (current-buffer) buffers))
(p (cdr b)))
(when b
(goto-char (car p))
(set-window-start (selected-window) (cdr p) t)))
;; delete dead windows from pointback-windows
(dolist (w pointback-windows)
(unless (window-live-p (car w))
(adelete 'pointback-windows (car w))))
;; delete window points of dead buffers
(dolist (w pointback-windows)
(let (buffers)
(dolist (b (cdr w))
(when (buffer-live-p (car b))
(push b buffers)))
(aput 'pointback-windows (car w) buffers))))
;;;###autoload
(define-minor-mode pointback-mode
"Restore previous window point when switching back to a buffer."
:lighter ""
(if pointback-mode
(progn
(add-hook 'post-command-hook 'pointback-store-point nil t)
(add-hook 'window-configuration-change-hook
'pointback-restore nil t))
(remove-hook 'post-command-hook 'pointback-store-point t)
(remove-hook 'window-configuration-change-hook 'pointback-restore t)
(setq pointback-windows nil)))
;;;###autoload
(define-globalized-minor-mode global-pointback-mode pointback-mode pointback-on)
(defun pointback-on ()
(pointback-mode 1))
(provide 'pointback)
;;; pointback.el ends here
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