;;; gnus-undo.el --- minor mode for undoing in Gnus
;; Copyright (C) 1996, 1997, 1998, 1999, 2000, 2002, 2003, 2004,
;; 2005, 2006 Free Software Foundation, Inc.
;; Author: Lars Magne Ingebrigtsen <firstname.lastname@example.org>
;; Keywords: news
;; 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., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.
;; This package allows arbitrary undoing in Gnus buffers. As all the
;; Gnus buffers aren't very text-oriented (what is in the buffers is
;; just some arbitrary representation of the actual data), normal Emacs
;; undoing doesn't work at all for Gnus.
;; This package works by letting Gnus register functions for reversing
;; actions, and then calling these functions when the user pushes the
;; `undo' key. As with normal `undo', there it is possible to set
;; undo boundaries and so on.
;; Internally, the undo sequence is represented by the
;; `gnus-undo-actions' list, where each element is a list of functions
;; to be called, in sequence, to undo some action. (An "action" is a
;; collection of functions.)
;; For instance, a function for killing a group will call
;; `gnus-undo-register' with a function that un-kills the group. This
;; package will put that function into an action.
(eval-when-compile (require 'cl))
(defgroup gnus-undo nil
"Undoing in Gnus buffers."
(defcustom gnus-undo-limit 2000
"The number of undoable actions recorded."
(defcustom gnus-undo-mode nil
"Minor mode for undoing in Gnus buffers."
(defcustom gnus-undo-mode-hook nil
"Hook called in all `gnus-undo-mode' buffers."
;;; Internal variables.
(defvar gnus-undo-actions nil)
(defvar gnus-undo-boundary t)
(defvar gnus-undo-last nil)
(defvar gnus-undo-boundary-inhibit nil)
;;; Minor mode definition.
(defvar gnus-undo-mode-map nil)
(setq gnus-undo-mode-map (make-sparse-keymap))
;; many people are used to type `C-/' on X terminals and get `C-_'.
[(control /)] gnus-undo))
(defun gnus-undo-make-menu-bar ()
;; This is disabled for the time being.
(define-key-after (current-local-map) [menu-bar file gnus-undo]
(cons "Undo" 'gnus-undo-actions)
[menu-bar file whatever])))
(defun gnus-undo-mode (&optional arg)
"Minor mode for providing `undo' in Gnus buffers.
(set (make-local-variable 'gnus-undo-mode)
(if (null arg) (not gnus-undo-mode)
(> (prefix-numeric-value arg) 0)))
(set (make-local-variable 'gnus-undo-actions) nil)
(set (make-local-variable 'gnus-undo-boundary) t)
;; Set up the menu.
(when (gnus-visual-p 'undo-menu 'menu)
(gnus-add-minor-mode 'gnus-undo-mode "" gnus-undo-mode-map)
(add-hook 'post-command-hook 'gnus-undo-boundary nil t)
;;; Interface functions.
(defun gnus-disable-undo (&optional buffer)
"Disable undoing in the current buffer."
(defun gnus-undo-boundary ()
"Set Gnus undo boundary."
(setq gnus-undo-boundary-inhibit nil)
(setq gnus-undo-boundary t)))
(defun gnus-undo-force-boundary ()
"Set Gnus undo boundary."
(setq gnus-undo-boundary-inhibit nil
(defun gnus-undo-register (form)
"Register FORMS as something to be performed to undo a change.
FORMS may use backtick quote syntax."
(put 'gnus-undo-register 'lisp-indent-function 0)
(put 'gnus-undo-register 'edebug-form-spec '(body))
(defun gnus-undo-register-1 (function)
"Register FUNCTION as something to be performed to undo a change."
;; We are on a boundary, so we create a new action.
(push (list function) gnus-undo-actions)
(setq gnus-undo-boundary nil))
;; Prepend the function to an old action.
(setcar gnus-undo-actions (cons function (car gnus-undo-actions))))
;; Initialize list.
(setq gnus-undo-actions (list (list function)))))
;; Limit the length of the undo list.
(let ((next (nthcdr gnus-undo-limit gnus-undo-actions)))
(setcdr next nil)))
;; We are not at a boundary...
(setq gnus-undo-boundary-inhibit t)))
(defun gnus-undo (n)
"Undo some previous changes in Gnus buffers.
Repeat this command to undo more changes.
A numeric argument serves as a repeat count."
(error "Undoing is not enabled in this buffer"))
(message "%s" last-command)
(when (or (not (eq last-command 'gnus-undo))
(setq gnus-undo-last gnus-undo-actions))
(let ((action (pop gnus-undo-last)))
(error "Nothing further to undo"))
(setq gnus-undo-actions (delq action gnus-undo-actions))
(setq gnus-undo-boundary t)
(funcall (pop action)))))
;;; arch-tag: 0d787bc7-787d-499a-837f-211d2cb07f2e
;;; gnus-undo.el ends here