1;;; master.el --- make a buffer the master over another buffer
2
3;; Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
4;;   Free Software Foundation, Inc.
5
6;; Author: Alex Schroeder <alex@gnu.org>
7;; Maintainer: Alex Schroeder <alex@gnu.org>
8;; Version: 1.0.2
9;; Keywords: comm
10
11;; This file is part of GNU Emacs.
12
13;; GNU Emacs is free software; you can redistribute it and/or modify
14;; it under the terms of the GNU General Public License as published by
15;; the Free Software Foundation; either version 2, or (at your option)
16;; any later version.
17
18;; GNU Emacs is distributed in the hope that it will be useful,
19;; but WITHOUT ANY WARRANTY; without even the implied warranty of
20;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
21;; GNU General Public License for more details.
22
23;; You should have received a copy of the GNU General Public License
24;; along with GNU Emacs; see the file COPYING.  If not, write to the
25;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
26;; Boston, MA 02110-1301, USA.
27
28;;; Commentary:
29
30;; master-mode is a minor mode which enables you to scroll another
31;; buffer (the slave) without leaving your current buffer (the master).
32
33;; It can be used by sql.el, for example: The SQL buffer is the master
34;; and its SQLi buffer is the slave.  This allows you to scroll the SQLi
35;; buffer containing the output from the SQL buffer containing the
36;; commands.
37;;
38;; This is how to use sql.el and master.el together: The variable
39;; sql-buffer contains the slave buffer.  It is a local variable in the
40;; SQL buffer.
41;;
42;; (add-hook 'sql-mode-hook
43;;	   (function (lambda ()
44;;		       (master-mode t)
45;;		       (master-set-slave sql-buffer))))
46;; (add-hook 'sql-set-sqli-hook
47;;	   (function (lambda ()
48;;		       (master-set-slave sql-buffer))))
49
50;;; Thanks to all the people who helped me out:
51;;
52;; Rob Riepel <networking.stanford.edu>
53
54;;; History:
55;;
56
57;;; Code:
58
59(defgroup master nil
60  "Support for master/slave relationships between buffers."
61  :version "22.1"
62  :group 'convenience)
63
64;; Variables that don't need initialization.
65
66(defvar master-of nil
67  "Slave buffer of the current buffer.  See `master-mode'.
68You can set this variable using `master-set-slave'.")
69
70(defvar master-set-slave-hook nil
71  "Hook run after the slave is changed using \\[master-set-slave].")
72
73;;; Define master mode.
74
75;;;###autoload
76(define-minor-mode master-mode
77  "Toggle Master mode.
78With no argument, this command toggles the mode.
79Non-null prefix argument turns on the mode.
80Null prefix argument turns off the mode.
81
82When Master mode is enabled, you can scroll the slave buffer using the
83following commands:
84
85\\{master-mode-map}
86
87The slave buffer is stored in the buffer-local variable `master-of'.
88You can set this variable using `master-set-slave'.  You can show
89yourself the value of `master-of' by calling `master-show-slave'."
90  :group 'master
91  :keymap
92  '(("\C-c\C-n" . master-says-scroll-up)
93    ("\C-c\C-p" . master-says-scroll-down)
94    ("\C-c<" . master-says-beginning-of-buffer)
95    ("\C-c>" . master-says-end-of-buffer)
96    ("\C-c\C-l" . master-says-recenter)))
97
98;; Initialize Master mode by setting a slave buffer.
99
100(defun master-set-slave (buffer)
101  "Makes BUFFER the slave of the current buffer.
102Use \\[master-mode] to toggle control of the slave buffer."
103  (interactive "bSlave: ")
104  (make-local-variable 'master-of)
105  (setq master-of buffer)
106  (run-hooks 'master-set-slave-hook))
107
108(defun master-show-slave ()
109  "Displays a message with the name of the slave buffer."
110  (interactive)
111  (message "This buffer is the master of %s.  Master-mode is %S."
112	   (or master-of "none")
113	   master-mode))
114
115
116
117;;; Functions that the master buffer can call for the slave buffer.
118
119(defun master-says-scroll-up (&optional arg)
120  "Display and scroll the slave buffer up.
121See `scroll-up'."
122  (interactive)
123  (master-says 'scroll-up arg))
124
125(defun master-says-scroll-down (&optional arg)
126  "Display and scroll the slave buffer down.
127See `scroll-down'."
128  (interactive)
129  (master-says 'scroll-down arg))
130
131(defun master-says-beginning-of-buffer (&optional arg)
132  "Display and move to the beginning of the slave buffer.
133See `beginning-of-buffer'."
134  (interactive)
135  (master-says 'beginning-of-buffer arg))
136
137(defun master-says-end-of-buffer (&optional arg)
138  "Display and move to the end of the slave buffer.
139See `end-of-buffer'."
140  (interactive)
141  (master-says 'end-of-buffer arg))
142
143(defun master-says-recenter (&optional arg)
144  "Recenter the slave buffer.
145See `recenter'."
146  (interactive)
147  (master-says 'recenter arg))
148
149;; The master function doing the stuff.
150
151(defun master-says (&optional command arg)
152  "Display slave buffer and execute COMMAND with ARG in its window."
153  (interactive)
154  (if (null (buffer-live-p (get-buffer master-of)))
155      (error "Slave buffer has disappeared")
156    (let ((window  (selected-window)))
157      (if (not (eq (window-buffer window) (get-buffer master-of)))
158	  (switch-to-buffer-other-window master-of))
159      (if command (condition-case nil (apply command arg) (error nil)))
160      (select-window window))))
161
162(provide 'master)
163
164;;; arch-tag: dca08daa-8127-45ae-b77e-b135160dce98
165;;; master.el ends here
166