(defgroup master nil
"Support for master/slave relationships between buffers."
:version "22.1"
:group 'convenience)
(defvar master-of nil
"Slave buffer of the current buffer. See `master-mode'.
You can set this variable using `master-set-slave'.")
(defvar master-set-slave-hook nil
"Hook run after the slave is changed using \\[master-set-slave].")
(define-minor-mode master-mode
"Toggle Master mode.
With no argument, this command toggles the mode.
Non-null prefix argument turns on the mode.
Null prefix argument turns off the mode.
When Master mode is enabled, you can scroll the slave buffer using the
following commands:
\\{master-mode-map}
The slave buffer is stored in the buffer-local variable `master-of'.
You can set this variable using `master-set-slave'. You can show
yourself the value of `master-of' by calling `master-show-slave'."
:group 'master
:keymap
'(("\C-c\C-n" . master-says-scroll-up)
("\C-c\C-p" . master-says-scroll-down)
("\C-c<" . master-says-beginning-of-buffer)
("\C-c>" . master-says-end-of-buffer)
("\C-c\C-l" . master-says-recenter)))
(defun master-set-slave (buffer)
"Makes BUFFER the slave of the current buffer.
Use \\[master-mode] to toggle control of the slave buffer."
(interactive "bSlave: ")
(make-local-variable 'master-of)
(setq master-of buffer)
(run-hooks 'master-set-slave-hook))
(defun master-show-slave ()
"Displays a message with the name of the slave buffer."
(interactive)
(message "This buffer is the master of %s. Master-mode is %S."
(or master-of "none")
master-mode))
(defun master-says-scroll-up (&optional arg)
"Display and scroll the slave buffer up.
See `scroll-up'."
(interactive)
(master-says 'scroll-up arg))
(defun master-says-scroll-down (&optional arg)
"Display and scroll the slave buffer down.
See `scroll-down'."
(interactive)
(master-says 'scroll-down arg))
(defun master-says-beginning-of-buffer (&optional arg)
"Display and move to the beginning of the slave buffer.
See `beginning-of-buffer'."
(interactive)
(master-says 'beginning-of-buffer arg))
(defun master-says-end-of-buffer (&optional arg)
"Display and move to the end of the slave buffer.
See `end-of-buffer'."
(interactive)
(master-says 'end-of-buffer arg))
(defun master-says-recenter (&optional arg)
"Recenter the slave buffer.
See `recenter'."
(interactive)
(master-says 'recenter arg))
(defun master-says (&optional command arg)
"Display slave buffer and execute COMMAND with ARG in its window."
(interactive)
(if (null (buffer-live-p (get-buffer master-of)))
(error "Slave buffer has disappeared")
(let ((window (selected-window)))
(if (not (eq (window-buffer window) (get-buffer master-of)))
(switch-to-buffer-other-window master-of))
(if command (condition-case nil (apply command arg) (error nil)))
(select-window window))))
(provide 'master)