lisp/gnus-undo.el

   1 ;;; gnus-undo.el --- minor mode for undoing in Gnus
   2
   3 ;; Copyright (C) 1996-2013 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 (eval-when-compile
  48   (when (featurep 'xemacs)
  49     (require 'easy-mmode))) ; for `define-minor-mode'
  50
  51 (require 'gnus-util)
  52 (require 'gnus)
  53
  54 (defgroup gnus-undo nil
  55   "Undoing in Gnus buffers."
  56   :group 'gnus)
  57
  58 (defcustom gnus-undo-limit 2000
  59   "The number of undoable actions recorded."
  60   :type 'integer
  61   :group 'gnus-undo)
  62
  63 (defcustom gnus-undo-mode nil
  64   ;; FIXME: This is a buffer-local minor mode which requires running
  65   ;; code upon activation/deactivation, so defining it as a defcustom
  66   ;; doesn't seem very useful: setting it to non-nil via Customize
  67   ;; probably won't do the right thing.
  68   "Minor mode for undoing in Gnus buffers."
  69   :type 'boolean
  70   :group 'gnus-undo)
  71
  72 (defcustom gnus-undo-mode-hook nil
  73   "Hook called in all `gnus-undo-mode' buffers."
  74   :type 'hook
  75   :group 'gnus-undo)
  76
  77 ;;; Internal variables.
  78
  79 (defvar gnus-undo-actions nil)
  80 (defvar gnus-undo-boundary t)
  81 (defvar gnus-undo-last nil)
  82 (defvar gnus-undo-boundary-inhibit nil)
  83
  84 ;;; Minor mode definition.
  85
  86 (defvar gnus-undo-mode-map
  87   (let ((map (make-sparse-keymap)))
  88     (gnus-define-keys map
  89       "\M-\C-_"     gnus-undo
  90       "\C-_"        gnus-undo
  91       "\C-xu"       gnus-undo
  92       ;; many people are used to type `C-/' on X terminals and get `C-_'.
  93       [(control /)] gnus-undo)
  94     map))
  95
  96 (defun gnus-undo-make-menu-bar ()
  97   ;; This is disabled for the time being.
  98   (when nil
  99     (define-key-after (current-local-map) [menu-bar file gnus-undo]
 100       (cons "Undo" 'gnus-undo-actions)
 101       [menu-bar file whatever])))
 102
 103 (define-minor-mode gnus-undo-mode
 104   "Minor mode for providing `undo' in Gnus buffers.
 105
 106 \\{gnus-undo-mode-map}"
 107   :keymap gnus-undo-mode-map
 108   (set (make-local-variable 'gnus-undo-actions) nil)
 109   (set (make-local-variable 'gnus-undo-boundary) t)
 110   (when gnus-undo-mode
 111     ;; Set up the menu.
 112     (when (gnus-visual-p 'undo-menu 'menu)
 113       (gnus-undo-make-menu-bar))
 114     (gnus-make-local-hook 'post-command-hook)
 115     (add-hook 'post-command-hook 'gnus-undo-boundary nil t)))
 116
 117 ;;; Interface functions.
 118
 119 (defun gnus-disable-undo (&optional buffer)
 120   "Disable undoing in the current buffer."
 121   (interactive)
 122   (save-excursion
 123     (when buffer
 124       (set-buffer buffer))
 125     (gnus-undo-mode -1)))
 126
 127 (defun gnus-undo-boundary ()
 128   "Set Gnus undo boundary."
 129   (if gnus-undo-boundary-inhibit
 130       (setq gnus-undo-boundary-inhibit nil)
 131     (setq gnus-undo-boundary t)))
 132
 133 (defun gnus-undo-force-boundary ()
 134   "Set Gnus undo boundary."
 135   (setq gnus-undo-boundary-inhibit nil
 136         gnus-undo-boundary t))
 137
 138 (defun gnus-undo-register (form)
 139   "Register FORMS as something to be performed to undo a change.
 140 FORMS may use backtick quote syntax."
 141   (when gnus-undo-mode
 142     (gnus-undo-register-1
 143      `(lambda ()
 144         ,form))))
 145
 146 (put 'gnus-undo-register 'lisp-indent-function 0)
 147 (put 'gnus-undo-register 'edebug-form-spec '(body))
 148
 149 (defun gnus-undo-register-1 (function)
 150   "Register FUNCTION as something to be performed to undo a change."
 151   (when gnus-undo-mode
 152     (cond
 153      ;; We are on a boundary, so we create a new action.
 154      (gnus-undo-boundary
 155       (push (list function) gnus-undo-actions)
 156       (setq gnus-undo-boundary nil))
 157      ;; Prepend the function to an old action.
 158      (gnus-undo-actions
 159       (setcar gnus-undo-actions (cons function (car gnus-undo-actions))))
 160      ;; Initialize list.
 161      (t
 162       (setq gnus-undo-actions (list (list function)))))
 163     ;; Limit the length of the undo list.
 164     (let ((next (nthcdr gnus-undo-limit gnus-undo-actions)))
 165       (when next
 166         (setcdr next nil)))
 167     ;; We are not at a boundary...
 168     (setq gnus-undo-boundary-inhibit t)))
 169
 170 (defun gnus-undo (n)
 171   "Undo some previous changes in Gnus buffers.
 172 Repeat this command to undo more changes.
 173 A numeric argument serves as a repeat count."
 174   (interactive "p")
 175   (unless gnus-undo-mode
 176     (error "Undoing is not enabled in this buffer"))
 177   (message "%s" last-command)
 178   (when (or (not (eq last-command 'gnus-undo))
 179             (not gnus-undo-last))
 180     (setq gnus-undo-last gnus-undo-actions))
 181   (let ((action (pop gnus-undo-last)))
 182     (unless action
 183       (error "Nothing further to undo"))
 184     (setq gnus-undo-actions (delq action gnus-undo-actions))
 185     (setq gnus-undo-boundary t)
 186     (mapc 'funcall action)))
 187
 188 (provide 'gnus-undo)
 189
 190 ;;; gnus-undo.el ends here