lisp/master.el

   1 ;;; master.el --- make a buffer the master over another buffer
   2
   3 ;; Copyright (C) 1999-2013 Free Software Foundation, Inc.
   4
   5 ;; Author: Alex Schroeder <alex@gnu.org>
   6 ;; Maintainer: Alex Schroeder <alex@gnu.org>
   7 ;; Version: 1.0.2
   8 ;; Keywords: comm
   9
  10 ;; This file is part of GNU Emacs.
  11
  12 ;; GNU Emacs is free software: you can redistribute it and/or modify
  13 ;; it under the terms of the GNU General Public License as published by
  14 ;; the Free Software Foundation, either version 3 of the License, or
  15 ;; (at your option) any later version.
  16
  17 ;; GNU Emacs is distributed in the hope that it will be useful,
  18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;; GNU General Public License for more details.
  21
  22 ;; You should have received a copy of the GNU General Public License
  23 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  24
  25 ;;; Commentary:
  26
  27 ;; master-mode is a minor mode which enables you to scroll another
  28 ;; buffer (the slave) without leaving your current buffer (the master).
  29
  30 ;; It can be used by sql.el, for example: The SQL buffer is the master
  31 ;; and its SQLi buffer is the slave.  This allows you to scroll the SQLi
  32 ;; buffer containing the output from the SQL buffer containing the
  33 ;; commands.
  34 ;;
  35 ;; This is how to use sql.el and master.el together: The variable
  36 ;; sql-buffer contains the slave buffer.  It is a local variable in the
  37 ;; SQL buffer.
  38 ;;
  39 ;; (add-hook 'sql-mode-hook
  40 ;;         (function (lambda ()
  41 ;;                     (master-mode t)
  42 ;;                     (master-set-slave sql-buffer))))
  43 ;; (add-hook 'sql-set-sqli-hook
  44 ;;         (function (lambda ()
  45 ;;                     (master-set-slave sql-buffer))))
  46
  47 ;;; Thanks to all the people who helped me out:
  48 ;;
  49 ;; Rob Riepel <networking.stanford.edu>
  50
  51 ;;; History:
  52 ;;
  53
  54 ;;; Code:
  55
  56 (defgroup master nil
  57   "Support for master/slave relationships between buffers."
  58   :version "22.1"
  59   :group 'convenience)
  60
  61 ;; Variables that don't need initialization.
  62
  63 (defvar master-of nil
  64   "Slave buffer of the current buffer.  See `master-mode'.
  65 You can set this variable using `master-set-slave'.")
  66
  67 (defvar master-set-slave-hook nil
  68   "Hook run after the slave is changed using \\[master-set-slave].")
  69
  70 ;;; Define master mode.
  71
  72 ;;;###autoload
  73 (define-minor-mode master-mode
  74   "Toggle Master mode.
  75 With a prefix argument ARG, enable Master mode if ARG is
  76 positive, and disable it otherwise.  If called from Lisp, enable
  77 the mode if ARG is omitted or nil.
  78
  79 When Master mode is enabled, you can scroll the slave buffer
  80 using the following commands:
  81
  82 \\{master-mode-map}
  83
  84 The slave buffer is stored in the buffer-local variable `master-of'.
  85 You can set this variable using `master-set-slave'.  You can show
  86 yourself the value of `master-of' by calling `master-show-slave'."
  87   :group 'master
  88   :keymap
  89   '(("\C-c\C-n" . master-says-scroll-up)
  90     ("\C-c\C-p" . master-says-scroll-down)
  91     ("\C-c<" . master-says-beginning-of-buffer)
  92     ("\C-c>" . master-says-end-of-buffer)
  93     ("\C-c\C-l" . master-says-recenter)))
  94
  95 ;; Initialize Master mode by setting a slave buffer.
  96
  97 (defun master-set-slave (buffer)
  98   "Makes BUFFER the slave of the current buffer.
  99 Use \\[master-mode] to toggle control of the slave buffer."
 100   (interactive "bSlave: ")
 101   (make-local-variable 'master-of)
 102   (setq master-of buffer)
 103   (run-hooks 'master-set-slave-hook))
 104
 105 (defun master-show-slave ()
 106   "Displays a message with the name of the slave buffer."
 107   (interactive)
 108   (message "This buffer is the master of %s.  Master-mode is %S."
 109            (or master-of "none")
 110            master-mode))
 111
 112 \f
 113
 114 ;;; Functions that the master buffer can call for the slave buffer.
 115
 116 (defun master-says-scroll-up (&optional arg)
 117   "Display and scroll the slave buffer up.
 118 See `scroll-up'."
 119   (interactive)
 120   (master-says 'scroll-up arg))
 121
 122 (defun master-says-scroll-down (&optional arg)
 123   "Display and scroll the slave buffer down.
 124 See `scroll-down'."
 125   (interactive)
 126   (master-says 'scroll-down arg))
 127
 128 (defun master-says-beginning-of-buffer (&optional arg)
 129   "Display and move to the beginning of the slave buffer.
 130 See `beginning-of-buffer'."
 131   (interactive)
 132   (master-says 'beginning-of-buffer arg))
 133
 134 (defun master-says-end-of-buffer (&optional arg)
 135   "Display and move to the end of the slave buffer.
 136 See `end-of-buffer'."
 137   (interactive)
 138   (master-says 'end-of-buffer arg))
 139
 140 (defun master-says-recenter (&optional arg)
 141   "Recenter the slave buffer.
 142 See `recenter'."
 143   (interactive)
 144   (master-says 'recenter arg))
 145
 146 ;; The master function doing the stuff.
 147
 148 (defun master-says (&optional command arg)
 149   "Display slave buffer and execute COMMAND with ARG in its window."
 150   (interactive)
 151   (if (null (buffer-live-p (get-buffer master-of)))
 152       (error "Slave buffer has disappeared")
 153     (let ((window  (selected-window)))
 154       (if (not (eq (window-buffer window) (get-buffer master-of)))
 155           (switch-to-buffer-other-window master-of))
 156       (if command (condition-case nil (apply command arg) (error nil)))
 157       (select-window window))))
 158
 159 (provide 'master)
 160
 161 ;;; master.el ends here