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   1 ;;; gnus-undo.el --- minor mode for undoing in Gnus
   2
   3 ;; Copyright (C) 1996-2016 Free Software Foundation, Inc.
   4
   5 ;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
   6 ;; Keywords: news
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software: you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation, either version 3 of the License, or
  13 ;; (at your option) any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  22
  23 ;;; Commentary:
  24
  25 ;; This package allows arbitrary undoing in Gnus buffers.  As all the
  26 ;; Gnus buffers aren't very text-oriented (what is in the buffers is
  27 ;; just some arbitrary representation of the actual data), normal Emacs
  28 ;; undoing doesn't work at all for Gnus.
  29 ;;
  30 ;; This package works by letting Gnus register functions for reversing
  31 ;; actions, and then calling these functions when the user pushes the
  32 ;; `undo' key.  As with normal `undo', there it is possible to set
  33 ;; undo boundaries and so on.
  34 ;;
  35 ;; Internally, the undo sequence is represented by the
  36 ;; `gnus-undo-actions' list, where each element is a list of functions
  37 ;; to be called, in sequence, to undo some action.  (An "action" is a
  38 ;; collection of functions.)
  39 ;;
  40 ;; For instance, a function for killing a group will call
  41 ;; `gnus-undo-register' with a function that un-kills the group.  This
  42 ;; package will put that function into an action.
  43
  44 ;;; Code:
  45
  46 (eval-when-compile (require 'cl))
  47
  48 (require 'gnus-util)
  49 (require 'gnus)
  50
  51 (defgroup gnus-undo nil
  52   "Undoing in Gnus buffers."
  53   :group 'gnus)
  54
  55 (defcustom gnus-undo-limit 2000
  56   "The number of undoable actions recorded."
  57   :type 'integer
  58   :group 'gnus-undo)
  59
  60 (defcustom gnus-undo-mode nil
  61   ;; FIXME: This is a buffer-local minor mode which requires running
  62   ;; code upon activation/deactivation, so defining it as a defcustom
  63   ;; doesn't seem very useful: setting it to non-nil via Customize
  64   ;; probably won't do the right thing.
  65   "Minor mode for undoing in Gnus buffers."
  66   :type 'boolean
  67   :group 'gnus-undo)
  68
  69 (defcustom gnus-undo-mode-hook nil
  70   "Hook called in all `gnus-undo-mode' buffers."
  71   :type 'hook
  72   :group 'gnus-undo)
  73
  74 ;;; Internal variables.
  75
  76 (defvar gnus-undo-actions nil)
  77 (defvar gnus-undo-boundary t)
  78 (defvar gnus-undo-last nil)
  79 (defvar gnus-undo-boundary-inhibit nil)
  80
  81 ;;; Minor mode definition.
  82
  83 (defvar gnus-undo-mode-map
  84   (let ((map (make-sparse-keymap)))
  85     (gnus-define-keys map
  86       "\M-\C-_"     gnus-undo
  87       "\C-_"        gnus-undo
  88       "\C-xu"       gnus-undo
  89       ;; many people are used to type `C-/' on X terminals and get `C-_'.
  90       [(control /)] gnus-undo)
  91     map))
  92
  93 (defun gnus-undo-make-menu-bar ()
  94   ;; This is disabled for the time being.
  95   (when nil
  96     (define-key-after (current-local-map) [menu-bar file gnus-undo]
  97       (cons "Undo" 'gnus-undo-actions)
  98       [menu-bar file whatever])))
  99
 100 (define-minor-mode gnus-undo-mode
 101   "Minor mode for providing `undo' in Gnus buffers.
 102
 103 \\{gnus-undo-mode-map}"
 104   :keymap gnus-undo-mode-map
 105   (set (make-local-variable 'gnus-undo-actions) nil)
 106   (set (make-local-variable 'gnus-undo-boundary) t)
 107   (when gnus-undo-mode
 108     ;; Set up the menu.
 109     (when (gnus-visual-p 'undo-menu 'menu)
 110       (gnus-undo-make-menu-bar))
 111     (add-hook 'post-command-hook 'gnus-undo-boundary nil t)))
 112
 113 ;;; Interface functions.
 114
 115 (defun gnus-disable-undo (&optional buffer)
 116   "Disable undoing in the current buffer."
 117   (interactive)
 118   (save-excursion
 119     (when buffer
 120       (set-buffer buffer))
 121     (gnus-undo-mode -1)))
 122
 123 (defun gnus-undo-boundary ()
 124   "Set Gnus undo boundary."
 125   (if gnus-undo-boundary-inhibit
 126       (setq gnus-undo-boundary-inhibit nil)
 127     (setq gnus-undo-boundary t)))
 128
 129 (defun gnus-undo-force-boundary ()
 130   "Set Gnus undo boundary."
 131   (setq gnus-undo-boundary-inhibit nil
 132         gnus-undo-boundary t))
 133
 134 (defun gnus-undo-register (form)
 135   "Register FORMS as something to be performed to undo a change.
 136 FORMS may use backtick quote syntax."
 137   (when gnus-undo-mode
 138     (gnus-undo-register-1
 139      `(lambda ()
 140         ,form))))
 141
 142 (put 'gnus-undo-register 'lisp-indent-function 0)
 143 (put 'gnus-undo-register 'edebug-form-spec '(body))
 144
 145 (defun gnus-undo-register-1 (function)
 146   "Register FUNCTION as something to be performed to undo a change."
 147   (when gnus-undo-mode
 148     (cond
 149      ;; We are on a boundary, so we create a new action.
 150      (gnus-undo-boundary
 151       (push (list function) gnus-undo-actions)
 152       (setq gnus-undo-boundary nil))
 153      ;; Prepend the function to an old action.
 154      (gnus-undo-actions
 155       (setcar gnus-undo-actions (cons function (car gnus-undo-actions))))
 156      ;; Initialize list.
 157      (t
 158       (setq gnus-undo-actions (list (list function)))))
 159     ;; Limit the length of the undo list.
 160     (let ((next (nthcdr gnus-undo-limit gnus-undo-actions)))
 161       (when next
 162         (setcdr next nil)))
 163     ;; We are not at a boundary...
 164     (setq gnus-undo-boundary-inhibit t)))
 165
 166 (defun gnus-undo (n)
 167   "Undo some previous changes in Gnus buffers.
 168 Repeat this command to undo more changes.
 169 A numeric argument serves as a repeat count."
 170   (interactive "p")
 171   (unless gnus-undo-mode
 172     (error "Undoing is not enabled in this buffer"))
 173   (message "%s" last-command)
 174   (when (or (not (eq last-command 'gnus-undo))
 175             (not gnus-undo-last))
 176     (setq gnus-undo-last gnus-undo-actions))
 177   (let ((action (pop gnus-undo-last)))
 178     (unless action
 179       (error "Nothing further to undo"))
 180     (setq gnus-undo-actions (delq action gnus-undo-actions))
 181     (setq gnus-undo-boundary t)
 182     (mapc 'funcall action)))
 183
 184 (provide 'gnus-undo)
 185
 186 ;;; gnus-undo.el ends here