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| | ;;; gnus-undo.el --- minor mode for undoing in Gnus -*- lexical-binding: t; -*-
;; Copyright (C) 1996-2021 Free Software Foundation, Inc.
;; Author: Lars Magne Ingebrigtsen <larsi@gnus.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 3 of the License, 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. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;; 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.
;;; Code:
(require 'gnus-util)
(require 'gnus)
(defgroup gnus-undo nil
"Undoing in Gnus buffers."
:group 'gnus)
(defcustom gnus-undo-limit 2000
"The number of undoable actions recorded."
:type 'integer)
(defcustom gnus-undo-mode nil
;; FIXME: This is a buffer-local minor mode which requires running
;; code upon activation/deactivation, so defining it as a defcustom
;; doesn't seem very useful: setting it to non-nil via Customize
;; probably won't do the right thing.
"Minor mode for undoing in Gnus buffers."
:type 'boolean)
(defcustom gnus-undo-mode-hook nil
"Hook called in all `gnus-undo-mode' buffers."
:type 'hook)
;;; 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
(let ((map (make-sparse-keymap)))
(gnus-define-keys map
"\M-\C-_" gnus-undo
"\C-_" gnus-undo
"\C-xu" gnus-undo
;; many people are used to type `C-/' on X terminals and get `C-_'.
[(control /)] gnus-undo)
map))
(defun gnus-undo-make-menu-bar ()
;; This is disabled for the time being.
(when nil
(define-key-after (current-local-map) [menu-bar file gnus-undo]
(cons "Undo" 'gnus-undo-actions)
[menu-bar file whatever])))
(define-minor-mode gnus-undo-mode
"Minor mode for providing `undo' in Gnus buffers.
\\{gnus-undo-mode-map}"
:keymap gnus-undo-mode-map
(setq-local gnus-undo-actions nil)
(setq-local gnus-undo-boundary t)
(when gnus-undo-mode
;; Set up the menu.
(when (gnus-visual-p 'undo-menu 'menu)
(gnus-undo-make-menu-bar))
(add-hook 'post-command-hook #'gnus-undo-boundary nil t)))
;;; Interface functions.
(defun gnus-disable-undo (&optional buffer)
"Disable undoing in the current buffer."
(interactive)
(save-excursion
(when buffer
(set-buffer buffer))
(gnus-undo-mode -1)))
(defun gnus-undo-boundary ()
"Set Gnus undo boundary."
(if gnus-undo-boundary-inhibit
(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
gnus-undo-boundary t))
(defun gnus-undo-register (form)
"Register FORMS as something to be performed to undo a change."
(when gnus-undo-mode
(gnus-undo-register-1
`(lambda () ,form))))
(defun gnus-undo-register-1 (function)
"Register FUNCTION as something to be performed to undo a change."
(when gnus-undo-mode
(cond
;; We are on a boundary, so we create a new action.
(gnus-undo-boundary
(push (list function) gnus-undo-actions)
(setq gnus-undo-boundary nil))
;; Prepend the function to an old action.
(gnus-undo-actions
(setcar gnus-undo-actions (cons function (car gnus-undo-actions))))
;; Initialize list.
(t
(setq gnus-undo-actions (list (list function)))))
;; Limit the length of the undo list.
(let ((next (nthcdr gnus-undo-limit gnus-undo-actions)))
(when next
(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."
;; FIXME: A numeric argument should serve as a repeat count.
(interactive "p")
(unless gnus-undo-mode
(error "Undoing is not enabled in this buffer"))
(message "%s" last-command)
(unless (and (eq last-command 'gnus-undo)
gnus-undo-last)
(setq gnus-undo-last gnus-undo-actions))
(let ((action (pop gnus-undo-last)))
(unless action
(error "Nothing further to undo"))
(setq gnus-undo-actions (delq action gnus-undo-actions))
(setq gnus-undo-boundary t)
(mapc #'funcall action)))
(provide 'gnus-undo)
;;; gnus-undo.el ends here
|