lisp/master.el

   1 ;;; master.el --- make a buffer the master over another buffer
   2
   3 ;; Copyright (C) 1999-2018 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 <https://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
  77 When Master mode is enabled, you can scroll the slave buffer
  78 using the following commands:
  79
  80 \\{master-mode-map}
  81
  82 The slave buffer is stored in the buffer-local variable `master-of'.
  83 You can set this variable using `master-set-slave'.  You can show
  84 yourself the value of `master-of' by calling `master-show-slave'."
  85   ;; Not global, so no effect.
  86 ;;;  :group 'master
  87   :keymap
  88   '(("\C-c\C-n" . master-says-scroll-up)
  89     ("\C-c\C-p" . master-says-scroll-down)
  90     ("\C-c<" . master-says-beginning-of-buffer)
  91     ("\C-c>" . master-says-end-of-buffer)
  92     ("\C-c\C-l" . master-says-recenter)))
  93
  94 ;; Initialize Master mode by setting a slave buffer.
  95
  96 (defun master-set-slave (buffer)
  97   "Makes BUFFER the slave of the current buffer.
  98 Use \\[master-mode] to toggle control of the slave buffer."
  99   (interactive "bSlave: ")
 100   (make-local-variable 'master-of)
 101   (setq master-of buffer)
 102   (run-hooks 'master-set-slave-hook))
 103
 104 (defun master-show-slave ()
 105   "Displays a message with the name of the slave buffer."
 106   (interactive)
 107   (message "This buffer is the master of %s.  Master-mode is %S."
 108            (or master-of "none")
 109            master-mode))
 110
 111 \f
 112
 113 ;;; Functions that the master buffer can call for the slave buffer.
 114
 115 (defun master-says-scroll-up (&optional arg)
 116   "Display and scroll the slave buffer up.
 117 See `scroll-up'."
 118   (interactive)
 119   (master-says 'scroll-up arg))
 120
 121 (defun master-says-scroll-down (&optional arg)
 122   "Display and scroll the slave buffer down.
 123 See `scroll-down'."
 124   (interactive)
 125   (master-says 'scroll-down arg))
 126
 127 (defun master-says-beginning-of-buffer (&optional arg)
 128   "Display and move to the beginning of the slave buffer.
 129 See `beginning-of-buffer'."
 130   (interactive)
 131   (master-says 'beginning-of-buffer arg))
 132
 133 (defun master-says-end-of-buffer (&optional arg)
 134   "Display and move to the end of the slave buffer.
 135 See `end-of-buffer'."
 136   (interactive)
 137   (master-says 'end-of-buffer arg))
 138
 139 (defun master-says-recenter (&optional arg)
 140   "Recenter the slave buffer.
 141 See `recenter'."
 142   (interactive)
 143   (master-says 'recenter arg))
 144
 145 ;; The master function doing the stuff.
 146
 147 (defun master-says (&optional command arg)
 148   "Display slave buffer and execute COMMAND with ARG in its window."
 149   (interactive)
 150   (if (null (buffer-live-p (get-buffer master-of)))
 151       (error "Slave buffer has disappeared")
 152     (let ((window  (selected-window)))
 153       (if (not (eq (window-buffer window) (get-buffer master-of)))
 154           (switch-to-buffer-other-window master-of))
 155       (if command (condition-case nil (apply command arg) (error nil)))
 156       (select-window window))))
 157
 158 (provide 'master)
 159
 160 ;;; master.el ends here