lisp/master.el

   1 ;;; master.el --- make a buffer the master over another buffer
   2
   3 ;; Copyright (C) 1999-2016 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 ;; Unused.
  57 ;;; (defgroup master nil
  58 ;;;   "Support for master/slave relationships between buffers."
  59 ;;;   :version "22.1"
  60 ;;;   :group 'convenience)
  61
  62 ;; Variables that don't need initialization.
  63
  64 (defvar master-of nil
  65   "Slave buffer of the current buffer.  See `master-mode'.
  66 You can set this variable using `master-set-slave'.")
  67
  68 (defvar master-set-slave-hook nil
  69   "Hook run after the slave is changed using \\[master-set-slave].")
  70
  71 ;;; Define master mode.
  72
  73 ;;;###autoload
  74 (define-minor-mode master-mode
  75   "Toggle Master mode.
  76 With a prefix argument ARG, enable Master mode if ARG is
  77 positive, and disable it otherwise.  If called from Lisp, enable
  78 the mode if ARG is omitted or nil.
  79
  80 When Master mode is enabled, you can scroll the slave buffer
  81 using the following commands:
  82
  83 \\{master-mode-map}
  84
  85 The slave buffer is stored in the buffer-local variable `master-of'.
  86 You can set this variable using `master-set-slave'.  You can show
  87 yourself the value of `master-of' by calling `master-show-slave'."
  88   ;; Not global, so no effect.
  89 ;;;  :group 'master
  90   :keymap
  91   '(("\C-c\C-n" . master-says-scroll-up)
  92     ("\C-c\C-p" . master-says-scroll-down)
  93     ("\C-c<" . master-says-beginning-of-buffer)
  94     ("\C-c>" . master-says-end-of-buffer)
  95     ("\C-c\C-l" . master-says-recenter)))
  96
  97 ;; Initialize Master mode by setting a slave buffer.
  98
  99 (defun master-set-slave (buffer)
 100   "Makes BUFFER the slave of the current buffer.
 101 Use \\[master-mode] to toggle control of the slave buffer."
 102   (interactive "bSlave: ")
 103   (make-local-variable 'master-of)
 104   (setq master-of buffer)
 105   (run-hooks 'master-set-slave-hook))
 106
 107 (defun master-show-slave ()
 108   "Displays a message with the name of the slave buffer."
 109   (interactive)
 110   (message "This buffer is the master of %s.  Master-mode is %S."
 111            (or master-of "none")
 112            master-mode))
 113
 114 \f
 115
 116 ;;; Functions that the master buffer can call for the slave buffer.
 117
 118 (defun master-says-scroll-up (&optional arg)
 119   "Display and scroll the slave buffer up.
 120 See `scroll-up'."
 121   (interactive)
 122   (master-says 'scroll-up arg))
 123
 124 (defun master-says-scroll-down (&optional arg)
 125   "Display and scroll the slave buffer down.
 126 See `scroll-down'."
 127   (interactive)
 128   (master-says 'scroll-down arg))
 129
 130 (defun master-says-beginning-of-buffer (&optional arg)
 131   "Display and move to the beginning of the slave buffer.
 132 See `beginning-of-buffer'."
 133   (interactive)
 134   (master-says 'beginning-of-buffer arg))
 135
 136 (defun master-says-end-of-buffer (&optional arg)
 137   "Display and move to the end of the slave buffer.
 138 See `end-of-buffer'."
 139   (interactive)
 140   (master-says 'end-of-buffer arg))
 141
 142 (defun master-says-recenter (&optional arg)
 143   "Recenter the slave buffer.
 144 See `recenter'."
 145   (interactive)
 146   (master-says 'recenter arg))
 147
 148 ;; The master function doing the stuff.
 149
 150 (defun master-says (&optional command arg)
 151   "Display slave buffer and execute COMMAND with ARG in its window."
 152   (interactive)
 153   (if (null (buffer-live-p (get-buffer master-of)))
 154       (error "Slave buffer has disappeared")
 155     (let ((window  (selected-window)))
 156       (if (not (eq (window-buffer window) (get-buffer master-of)))
 157           (switch-to-buffer-other-window master-of))
 158       (if command (condition-case nil (apply command arg) (error nil)))
 159       (select-window window))))
 160
 161 (provide 'master)
 162
 163 ;;; master.el ends here