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;;; server.el --- Lisp code for GNU Emacs running as server process
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;; Copyright (C) 1986,87,92,94,95,96,97,98,99,2000,01,02,2003
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;;	 Free Software Foundation, Inc.
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;; Author: William Sommerfeld <wesommer@athena.mit.edu>
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;; Maintainer: FSF
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;; Keywords: processes
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;; Changes by peck@sun.com and by rms.

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation; either version 2, or (at your option)
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;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.
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;;; Commentary:
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;; This Lisp code is run in Emacs when it is to operate as
;; a server for other processes.
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;; Load this library and do M-x server-edit to enable Emacs as a server.
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;; Emacs opens up a socket for communication with clients.  If there are no
;; client buffers to edit, server-edit acts like (switch-to-buffer
;; (other-buffer))
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;; When some other program runs "the editor" to edit a file,
;; "the editor" can be the Emacs client program ../lib-src/emacsclient.
;; This program transmits the file names to Emacs through
;; the server subprocess, and Emacs visits them and lets you edit them.
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;; Note that any number of clients may dispatch files to emacs to be edited.
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;; When you finish editing a Server buffer, again call server-edit
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;; to mark that buffer as done for the client and switch to the next
;; Server buffer.  When all the buffers for a client have been edited
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;; and exited with server-edit, the client "editor" will return
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;; to the program that invoked it.
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;; Your editing commands and Emacs's display output go to and from
;; the terminal in the usual way.  Thus, server operation is possible
;; only when Emacs can talk to the terminal at the time you invoke
;; the client.  This is possible in four cases:
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;; 1. On a window system, where Emacs runs in one window and the
;; program that wants to use "the editor" runs in another.
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;; 2. On a multi-terminal system, where Emacs runs on one terminal and the
;; program that wants to use "the editor" runs on another.
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;; 3. When the program that wants to use "the editor" is running
;; as a subprocess of Emacs.
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;; 4. On a system with job control, when Emacs is suspended, the program
;; that wants to use "the editor" will stop and display
;; "Waiting for Emacs...".  It can then be suspended, and Emacs can be
;; brought into the foreground for editing.  When done editing, Emacs is
;; suspended again, and the client program is brought into the foreground.
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;; The buffer local variable "server-buffer-clients" lists
;; the clients who are waiting for this buffer to be edited.
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;; The global variable "server-clients" lists all the waiting clients,
;; and which files are yet to be edited for each.
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;;; Code:
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(eval-when-compile (require 'cl))

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(defgroup server nil
  "Emacs running as a server process."
  :group 'external)

(defcustom server-visit-hook nil
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  "*Hook run when visiting a file for the Emacs server."
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  :group 'server
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  :type 'hook)
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(defcustom server-switch-hook nil
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  "*Hook run when switching to a buffer for the Emacs server."
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  :group 'server
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  :type 'hook)
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(defcustom server-done-hook nil
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  "*Hook run when done editing a buffer for the Emacs server."
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  :group 'server
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  :type 'hook)
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(defvar server-process nil
  "The current server process.")
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(defvar server-clients nil
  "List of current server clients.
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Each element is (CLIENTID BUFFERS...) where CLIENTID is a string
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that can be given to the server process to identify a client.
When a buffer is marked as \"done\", it is removed from this list.")

(defvar server-buffer-clients nil
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  "List of client ids for clients requesting editing of current buffer.")
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(make-variable-buffer-local 'server-buffer-clients)
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;; Changing major modes should not erase this local.
(put 'server-buffer-clients 'permanent-local t)

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(defcustom server-window nil
  "*Specification of the window to use for selecting Emacs server buffers.
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If nil, use the selected window.
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If it is a function, it should take one argument (a buffer) and
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display and select it.  A common value is `pop-to-buffer'.
If it is a window, use that.
If it is a frame, use the frame's selected window.

It is not meaningful to set this to a specific frame or window with Custom.
Only programs can do so."
  :group 'server
  :version "21.4"
  :type '(choice (const :tag "Use selected window"
			:match (lambda (widget value)
				 (not (functionp value)))
			nil)
		 (function-item :tag "Use pop-to-buffer" pop-to-buffer)
		 (function :tag "Other function")))
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(defcustom server-temp-file-regexp "^/tmp/Re\\|/draft$"
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  "*Regexp matching names of temporary files.
These are deleted and reused after each edit by the programs that
invoke the Emacs server."
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  :group 'server
  :type 'regexp)
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(defcustom server-kill-new-buffers t
  "*Whether to kill buffers when done with them.
If non-nil, kill a buffer unless it already existed before editing
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it with Emacs server.  If nil, kill only buffers as specified by
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`server-temp-file-regexp'.
Please note that only buffers are killed that still have a client,
i.e. buffers visited which \"emacsclient --no-wait\" are never killed in
this way."
  :group 'server
  :type 'boolean
  :version "21.1")

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(or (assq 'server-buffer-clients minor-mode-alist)
    (setq minor-mode-alist (cons '(server-buffer-clients " Server") minor-mode-alist)))

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(defvar server-existing-buffer nil
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  "Non-nil means the buffer existed before the server was asked to visit it.
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This means that the server should not kill the buffer when you say you
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are done with it in the server.")
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(make-variable-buffer-local 'server-existing-buffer)

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(defvar server-socket-name
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  (format "/tmp/emacs%d-%s/server" (user-uid)
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	  (substring (system-name) 0 (string-match "\\." (system-name)))))
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(defun server-log (string &optional client)
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  "If a *server* buffer exists, write STRING to it for logging purposes."
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  (if (get-buffer "*server*")
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      (with-current-buffer "*server*"
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	(goto-char (point-max))
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	(insert (current-time-string)
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		(if client (format " %s:" client) " ")
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		string)
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	(or (bolp) (newline)))))
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(defun server-sentinel (proc msg)
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  (let ((client (assq proc server-clients)))
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    ;; Remove PROC from the list of clients.
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    (when client
      (setq server-clients (delq client server-clients))
      (dolist (buf (cdr client))
	(with-current-buffer buf
	  ;; Remove PROC from the clients of each buffer.
	  (setq server-buffer-clients (delq proc server-buffer-clients))
	  ;; Kill the buffer if necessary.
	  (when (and (null server-buffer-clients)
		     (or (and server-kill-new-buffers
			      (not server-existing-buffer))
			 (server-temp-file-p)))
	    (kill-buffer (current-buffer)))))))
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  (server-log (format "Status changed to %s" (process-status proc)) proc))

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(defun server-select-display (display)
  ;; If the current frame is on `display' we're all set.
  (unless (equal (frame-parameter (selected-frame) 'display) display)
    ;; Otherwise, look for an existing frame there and select it.
    (dolist (frame (frame-list))
      (when (equal (frame-parameter frame 'display) display)
	(select-frame frame)))
    ;; If there's no frame on that display yet, create a dummy one
    ;; and select it.
    (unless (equal (frame-parameter (selected-frame) 'display) display)
      (select-frame
       (make-frame-on-display
	display
	;; This frame is only there in place of an actual "current display"
	;; setting, so we want it to be as unobtrusive as possible.  That's
	;; what the invisibility is for.  The minibuffer setting is so that
	;; we don't end up displaying a buffer in it (which noone would
	;; notice).
	'((visibility . nil) (minibuffer . only)))))))

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(defun server-unquote-arg (arg)
  (replace-regexp-in-string
   "&." (lambda (s)
	  (case (aref s 1)
	    (?& "&")
	    (?- "-")
	    (?n "\n")
	    (t " ")))
   arg t t))
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(defun server-ensure-safe-dir (dir)
  "Make sure DIR is a directory with no race-condition issues.
Creates the directory if necessary and makes sure:
- there's no symlink involved
- it's owned by us
- it's not readable/writable by anybody else."
  (setq dir (directory-file-name dir))
  (let ((attrs (file-attributes dir)))
    (unless attrs
      (letf (((default-file-modes) ?\700)) (make-directory dir))
      (setq attrs (file-attributes dir)))
    ;; Check that it's safe for use.
    (unless (and (eq t (car attrs)) (eq (nth 2 attrs) (user-uid))
		 (zerop (logand ?\077 (file-modes dir))))
      (error "The directory %s is unsafe" dir))))

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;;;###autoload
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(defun server-start (&optional leave-dead)
  "Allow this Emacs process to be a server for client processes.
This starts a server communications subprocess through which
client \"editors\" can send your editing commands to this Emacs job.
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To use the server, set up the program `emacsclient' in the
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Emacs distribution as your standard \"editor\".

Prefix arg means just kill any existing server communications subprocess."
  (interactive "P")
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  ;; Make sure there is a safe directory in which to place the socket.
  (server-ensure-safe-dir (file-name-directory server-socket-name))
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  ;; kill it dead!
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  (condition-case () (delete-process server-process) (error nil))
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  ;; Delete the socket files made by previous server invocations.
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  (condition-case () (delete-file server-socket-name) (error nil))
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  ;; If this Emacs already had a server, clear out associated status.
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  (while server-clients
    (let ((buffer (nth 1 (car server-clients))))
      (server-buffer-done buffer)))
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  (unless leave-dead
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    (if server-process
	(server-log (message "Restarting server")))
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    (letf (((default-file-modes) ?\700))
      (setq server-process
	    (make-network-process
	     :name "server" :family 'local :server t :noquery t
	     :service server-socket-name
	     :sentinel 'server-sentinel :filter 'server-process-filter
	     ;; We must receive file names without being decoded.
	     ;; Those are decoded by server-process-filter according
	     ;; to file-name-coding-system.
	     :coding 'raw-text)))))
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;;;###autoload
(define-minor-mode server-mode
  "Toggle Server mode.
With ARG, turn Server mode on if ARG is positive, off otherwise.
Server mode runs a process that accepts commands from the
`emacsclient' program.  See `server-start' and Info node `Emacs server'."
  :global t
  :group 'server
  :version "21.4"
  ;; Fixme: Should this check for an existing server socket and do
  ;; nothing if there is one (for multiple Emacs sessions)?
  (server-start (not server-mode)))
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(defun server-process-filter (proc string)
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  "Process a request from the server to edit some files.
PROC is the server process.  Format of STRING is \"PATH PATH PATH... \\n\"."
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  (server-log string proc)
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  (let ((prev (process-get proc 'previous-string)))
    (when prev
      (setq string (concat prev string))
      (process-put proc 'previous-string nil)))
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  ;; If the input is multiple lines,
  ;; process each line individually.
  (while (string-match "\n" string)
    (let ((request (substring string 0 (match-beginning 0)))
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	  (coding-system (and default-enable-multibyte-characters
			      (or file-name-coding-system
				  default-file-name-coding-system)))
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	  client nowait eval
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	  (files nil)
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	  (lineno 1)
	  (columnno 0))
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      ;; Remove this line from STRING.
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      (setq string (substring string (match-end 0)))
      (setq client (cons proc nil))
      (while (string-match "[^ ]* " request)
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	(let ((arg (substring request (match-beginning 0) (1- (match-end 0)))))
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	  (setq request (substring request (match-end 0)))
	  (cond
	   ((equal "-nowait" arg) (setq nowait t))
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	   ((equal "-eval" arg) (setq eval t))
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	   ((and (equal "-display" arg) (string-match "\\([^ ]*\\) " request))
	    (let ((display (server-unquote-arg (match-string 1 request))))
	      (setq request (substring request (match-end 0)))
	      (condition-case err
		  (server-select-display display)
		(error (process-send-string proc (nth 1 err))
		       (setq request "")))))
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	   ;; ARG is a line number option.
	   ((string-match "\\`\\+[0-9]+\\'" arg)
	    (setq lineno (string-to-int (substring arg 1))))
	   ;; ARG is line number:column option.
	   ((string-match "\\`+\\([0-9]+\\):\\([0-9]+\\)\\'" arg)
	    (setq lineno (string-to-int (match-string 1 arg))
		  columnno (string-to-int (match-string 2 arg))))
	   (t
	    ;; Undo the quoting that emacsclient does
	    ;; for certain special characters.
	    (setq arg (server-unquote-arg arg))
	    ;; Now decode the file name if necessary.
	    (if coding-system
		(setq arg (decode-coding-string arg coding-system)))
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	    (if eval
		(let ((v (eval (car (read-from-string arg)))))
		  (when v
		    (with-temp-buffer
		      (let ((standard-output (current-buffer)))
			(pp v)
			(process-send-region proc (point-min) (point-max))))))
	      ;; ARG is a file name.
	      ;; Collapse multiple slashes to single slashes.
	      (setq arg (command-line-normalize-file-name arg))
	      (push (list arg lineno columnno) files))
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	    (setq lineno 1)
	    (setq columnno 0)))))
      (when files
	(run-hooks 'pre-command-hook)
	(server-visit-files files client nowait)
	(run-hooks 'post-command-hook))
      ;; CLIENT is now a list (CLIENTNUM BUFFERS...)
      (if (null (cdr client))
	  ;; This client is empty; get rid of it immediately.
	  (progn
	    (delete-process proc)
	    (server-log "Close empty client" proc))
	;; We visited some buffer for this client.
	(or nowait (push client server-clients))
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	(unless (or isearch-mode (minibufferp))
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	  (server-switch-buffer (nth 1 client))
	  (run-hooks 'server-switch-hook)
	  (unless nowait
	    (message (substitute-command-keys
		      "When done with a buffer, type \\[server-edit]")))))))
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  ;; Save for later any partial line that remains.
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  (when (> (length string) 0)
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    (process-put proc 'previous-string string)))
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(defun server-goto-line-column (file-line-col)
  (goto-line (nth 1 file-line-col))
  (let ((column-number (nth 2 file-line-col)))
    (if (> column-number 0)
	(move-to-column (1- column-number)))))

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(defun server-visit-files (files client &optional nowait)
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  "Find FILES and return the list CLIENT with the buffers nconc'd.
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FILES is an alist whose elements are (FILENAME LINENUMBER COLUMNNUMBER).
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NOWAIT non-nil means this client is not waiting for the results,
so don't mark these buffers specially, just visit them normally."
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  ;; Bind last-nonmenu-event to force use of keyboard, not mouse, for queries.
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  (let ((last-nonmenu-event t) client-record)
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    ;; Restore the current buffer afterward, but not using save-excursion,
    ;; because we don't want to save point in this buffer
    ;; if it happens to be one of those specified by the server.
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    (save-current-buffer
      (dolist (file files)
	;; If there is an existing buffer modified or the file is
	;; modified, revert it.  If there is an existing buffer with
	;; deleted file, offer to write it.
	(let* ((filen (car file))
	       (obuf (get-file-buffer filen)))
	  (push filen file-name-history)
	  (if (and obuf (set-buffer obuf))
	      (progn
		(cond ((file-exists-p filen)
		       (if (not (verify-visited-file-modtime obuf))
			   (revert-buffer t nil)))
		      (t
		       (if (y-or-n-p
			    (concat "File no longer exists: "
				    filen
				    ", write buffer to file? "))
			   (write-file filen))))
		(setq server-existing-buffer t)
		(server-goto-line-column file))
	    (set-buffer (find-file-noselect filen))
	    (server-goto-line-column file)
	    (run-hooks 'server-visit-hook)))
	(unless nowait
	  ;; When the buffer is killed, inform the clients.
	  (add-hook 'kill-buffer-hook 'server-kill-buffer nil t)
	  (push (car client) server-buffer-clients))
	(push (current-buffer) client-record)))
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    (nconc client client-record)))

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(defun server-buffer-done (buffer &optional for-killing)
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  "Mark BUFFER as \"done\" for its client(s).
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This buries the buffer, then returns a list of the form (NEXT-BUFFER KILLED).
NEXT-BUFFER is another server buffer, as a suggestion for what to select next,
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or nil.  KILLED is t if we killed BUFFER (typically, because it was visiting
a temp file).
FOR-KILLING if non-nil indicates that we are called from `kill-buffer'."
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  (let ((next-buffer nil)
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	(killed nil)
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	(old-clients server-clients))
    (while old-clients
      (let ((client (car old-clients)))
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	(or next-buffer
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	    (setq next-buffer (nth 1 (memq buffer client))))
	(delq buffer client)
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	;; Delete all dead buffers from CLIENT.
	(let ((tail client))
	  (while tail
	    (and (bufferp (car tail))
		 (null (buffer-name (car tail)))
		 (delq (car tail) client))
	    (setq tail (cdr tail))))
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	;; If client now has no pending buffers,
	;; tell it that it is done, and forget it entirely.
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	(unless (cdr client)
	  (delete-process (car client))
	  (server-log "Close" (car client))
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	  (setq server-clients (delq client server-clients))))
      (setq old-clients (cdr old-clients)))
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    (if (and (bufferp buffer) (buffer-name buffer))
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	;; We may or may not kill this buffer;
	;; if we do, do not call server-buffer-done recursively
	;; from kill-buffer-hook.
	(let ((server-kill-buffer-running t))
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	  (with-current-buffer buffer
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	    (setq server-buffer-clients nil)
	    (run-hooks 'server-done-hook))
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	  ;; Notice whether server-done-hook killed the buffer.
	  (if (null (buffer-name buffer))
	      (setq killed t)
	    ;; Don't bother killing or burying the buffer
	    ;; when we are called from kill-buffer.
	    (unless for-killing
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	      (when (and (not killed)
			 server-kill-new-buffers
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			 (with-current-buffer buffer
			   (not server-existing-buffer)))
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		(setq killed t)
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		(bury-buffer buffer)
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		(kill-buffer buffer))
	      (unless killed
		(if (server-temp-file-p buffer)
		    (progn
		      (kill-buffer buffer)
		      (setq killed t))
		  (bury-buffer buffer)))))))
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    (list next-buffer killed)))
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(defun server-temp-file-p (&optional buffer)
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  "Return non-nil if BUFFER contains a file considered temporary.
These are files whose names suggest they are repeatedly
reused to pass information to another program.

The variable `server-temp-file-regexp' controls which filenames
are considered temporary."
  (and (buffer-file-name buffer)
       (string-match server-temp-file-regexp (buffer-file-name buffer))))

(defun server-done ()
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  "Offer to save current buffer, mark it as \"done\" for clients.
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This kills or buries the buffer, then returns a list
of the form (NEXT-BUFFER KILLED).  NEXT-BUFFER is another server buffer,
as a suggestion for what to select next, or nil.
KILLED is t if we killed BUFFER, which happens if it was created
specifically for the clients and did not exist before their request for it."
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  (when server-buffer-clients
    (if (server-temp-file-p)
	;; For a temp file, save, and do make a non-numeric backup
	;; (unless make-backup-files is nil).
	(let ((version-control nil)
	      (buffer-backed-up nil))
	  (save-buffer))
      (if (and (buffer-modified-p)
	       buffer-file-name
	       (y-or-n-p (concat "Save file " buffer-file-name "? ")))
	  (save-buffer)))
    (server-buffer-done (current-buffer))))
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;; Ask before killing a server buffer.
;; It was suggested to release its client instead,
;; but I think that is dangerous--the client would proceed
;; using whatever is on disk in that file. -- rms.
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(defun server-kill-buffer-query-function ()
  (or (not server-buffer-clients)
      (yes-or-no-p (format "Buffer `%s' still has clients; kill it? "
			   (buffer-name (current-buffer))))))

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(add-hook 'kill-buffer-query-functions
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 	  'server-kill-buffer-query-function)

(defun server-kill-emacs-query-function ()
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  (let (live-client
	(tail server-clients))
    ;; See if any clients have any buffers that are still alive.
    (while tail
      (if (memq t (mapcar 'stringp (mapcar 'buffer-name (cdr (car tail)))))
	  (setq live-client t))
      (setq tail (cdr tail)))
    (or (not live-client)
	(yes-or-no-p "Server buffers still have clients; exit anyway? "))))
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(add-hook 'kill-emacs-query-functions 'server-kill-emacs-query-function)
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(defvar server-kill-buffer-running nil
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  "Non-nil while `server-kill-buffer' or `server-buffer-done' is running.")
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(defun server-kill-buffer ()
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  ;; Prevent infinite recursion if user has made server-done-hook
  ;; call kill-buffer.
  (or server-kill-buffer-running
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      (and server-buffer-clients
	   (let ((server-kill-buffer-running t))
	     (when server-process
	       (server-buffer-done (current-buffer) t))))))
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(defun server-edit (&optional arg)
  "Switch to next server editing buffer; say \"Done\" for current buffer.
If a server buffer is current, it is marked \"done\" and optionally saved.
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The buffer is also killed if it did not exist before the clients asked for it.
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When all of a client's buffers are marked as \"done\", the client is notified.

Temporary files such as MH <draft> files are always saved and backed up,
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no questions asked.  (The variable `make-backup-files', if nil, still
inhibits a backup; you can set it locally in a particular buffer to
prevent a backup for it.)  The variable `server-temp-file-regexp' controls
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which filenames are considered temporary.

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If invoked with a prefix argument, or if there is no server process running,
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starts server process and that is all.  Invoked by \\[server-edit]."
  (interactive "P")
  (if (or arg
	  (not server-process)
	  (memq (process-status server-process) '(signal exit)))
      (server-start nil)
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    (apply 'server-switch-buffer (server-done))))
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(defun server-switch-buffer (&optional next-buffer killed-one)
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  "Switch to another buffer, preferably one that has a client.
Arg NEXT-BUFFER is a suggestion; if it is a live buffer, use it."
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  ;; KILLED-ONE is t in a recursive call
  ;; if we have already killed one temp-file server buffer.
  ;; This means we should avoid the final "switch to some other buffer"
  ;; since we've already effectively done that.
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  (if (null next-buffer)
      (if server-clients
	  (server-switch-buffer (nth 1 (car server-clients)) killed-one)
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	(unless (or killed-one (window-dedicated-p (selected-window)))
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	  (switch-to-buffer (other-buffer))
	  (message "No server buffers remain to edit")))
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    (if (not (buffer-name next-buffer))
	;; If NEXT-BUFFER is a dead buffer, remove the server records for it
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	;; and try the next surviving server buffer.
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	(apply 'server-switch-buffer (server-buffer-done next-buffer))
      ;; OK, we know next-buffer is live, let's display and select it.
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      (if (functionp server-window)
	  (funcall server-window next-buffer)
	(let ((win (get-buffer-window next-buffer 0)))
	  (if (and win (not server-window))
	      ;; The buffer is already displayed: just reuse the window.
	      (let ((frame (window-frame win)))
		(if (eq (frame-visible-p frame) 'icon)
		    (raise-frame frame))
		(select-window win)
		(set-buffer next-buffer))
	    ;; Otherwise, let's find an appropriate window.
	    (cond ((and (windowp server-window)
			(window-live-p server-window))
		   (select-window server-window))
		  ((framep server-window)
		   (if (not (frame-live-p server-window))
		       (setq server-window (make-frame)))
		   (select-window (frame-selected-window server-window))))
	    (if (window-minibuffer-p (selected-window))
		(select-window (next-window nil 'nomini 0)))
	    ;; Move to a non-dedicated window, if we have one.
	    (when (window-dedicated-p (selected-window))
	      (select-window
	       (get-window-with-predicate
		(lambda (w)
		  (and (not (window-dedicated-p w))
		       (equal (frame-parameter (window-frame w) 'display)
			      (frame-parameter (selected-frame) 'display))))
		'nomini 'visible (selected-window))))
	    (condition-case nil
		(switch-to-buffer next-buffer)
	      ;; After all the above, we might still have ended up with
	      ;; a minibuffer/dedicated-window (if there's no other).
	      (error (pop-to-buffer next-buffer)))))))))
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(global-set-key "\C-x#" 'server-edit)
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(defun server-unload-hook ()
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  (server-start t)
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  (remove-hook 'kill-buffer-query-functions 'server-kill-buffer-query-function)
  (remove-hook 'kill-emacs-query-functions 'server-kill-emacs-query-function)
  (remove-hook 'kill-buffer-hook 'server-kill-buffer))
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(provide 'server)
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;;; server.el ends here