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;;; server.el --- Lisp code for GNU Emacs running as server process
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;; Copyright (C) 1986, 1987, 1992, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
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;;   2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
;;   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.
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;; Overhaul by Karoly Lorentey <lorentey@elte.hu> for multi-tty support.
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;; This file is part of GNU Emacs.

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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
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;; 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.  If not, see <http://www.gnu.org/licenses/>.
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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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;; Todo:

;; - handle command-line-args-left.
;; - move most of the args processing and decision making from emacsclient.c
;;   to here.
;; - fix up handling of the client's environment (place it in the terminal?).

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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)

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(defcustom server-use-tcp nil
  "If non-nil, use TCP sockets instead of local sockets."
  :set #'(lambda (sym val)
           (unless (featurep 'make-network-process '(:family local))
             (setq val t)
             (unless load-in-progress
               (message "Local sockets unsupported, using TCP sockets")))
           (when val (random t))
           (set-default sym val))
  :group 'server
  :type 'boolean
  :version "22.1")

(defcustom server-host nil
  "The name or IP address to use as host address of the server process.
If set, the server accepts remote connections; otherwise it is local."
  :group 'server
  :type '(choice
          (string :tag "Name or IP address")
          (const :tag "Local" nil))
  :version "22.1")
(put 'server-host 'risky-local-variable t)

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(defcustom server-auth-dir (locate-user-emacs-file "server/")
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  "Directory for server authentication files."
  :group 'server
  :type 'directory
  :version "22.1")
(put 'server-auth-dir 'risky-local-variable t)

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(defcustom server-raise-frame t
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  "If non-nil, raise frame when switching to a buffer."
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  :group 'server
  :type 'boolean
  :version "22.1")

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(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 a process.")
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(defvar server-buffer-clients nil
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  "List of client processes 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
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  "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
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  :version "22.1"
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  :type '(choice (const :tag "Use selected window"
			:match (lambda (widget value)
				 (not (functionp value)))
			nil)
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		 (function-item :tag "Display in new frame" switch-to-buffer-other-frame)
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		 (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.
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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
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  "Whether to kill buffers when done with them.
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If non-nil, kill a buffer unless it already existed before editing
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it with the Emacs server.  If nil, kill only buffers as specified by
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`server-temp-file-regexp'.
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Please note that only buffers that still have a client are killed,
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i.e. buffers visited with \"emacsclient --no-wait\" are never killed
in this way."
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  :group 'server
  :type 'boolean
  :version "21.1")

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(or (assq 'server-buffer-clients minor-mode-alist)
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    (push '(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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(defcustom server-name "server"
  "The name of the Emacs server, if this Emacs process creates one.
The command `server-start' makes use of this.  It should not be
changed while a server is running."
  :group 'server
  :type 'string
  :version "23.1")
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;; We do not use `temporary-file-directory' here, because emacsclient
;; does not read the init file.
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(defvar server-socket-dir
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  (and (featurep 'make-network-process '(:family local))
       (format "%s/emacs%d" (or (getenv "TMPDIR") "/tmp") (user-uid)))
  "The directory in which to place the server socket.
If local sockets are not supported, this is nil.")
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(defun server-clients-with (property value)
  "Return a list of clients with PROPERTY set to VALUE."
  (let (result)
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    (dolist (proc server-clients result)
      (when (equal value (process-get proc property))
	(push proc result)))))
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(defun server-add-client (proc)
  "Create a client for process PROC, if it doesn't already have one.
New clients have no properties."
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  (add-to-list 'server-clients proc))
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(defmacro server-with-environment (env vars &rest body)
  "Evaluate BODY with environment variables VARS set to those in ENV.
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The environment variables are then restored to their previous values.

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VARS should be a list of strings.
ENV should be in the same format as `process-environment'."
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  (declare (indent 2))
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  (let ((var (make-symbol "var"))
	(value (make-symbol "value")))
    `(let ((process-environment process-environment))
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       (dolist (,var ,vars)
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         (let ((,value (getenv-internal ,var ,env)))
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           (push (if (stringp ,value)
                     (concat ,var "=" ,value)
                   ,var)
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                 process-environment)))
       (progn ,@body))))
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(defun server-delete-client (proc &optional noframe)
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  "Delete PROC, including its buffers, terminals and frames.
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If NOFRAME is non-nil, let the frames live.
Updates `server-clients'."
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  (server-log (concat "server-delete-client" (if noframe " noframe")) proc)
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  ;; Force a new lookup of client (prevents infinite recursion).
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  (when (memq proc server-clients)
    (let ((buffers (process-get proc 'buffers)))
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      ;; Kill the client's buffers.
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      (dolist (buf buffers)
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	(when (buffer-live-p buf)
	  (with-current-buffer buf
	    ;; Kill the buffer if necessary.
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	    (when (and (equal server-buffer-clients
			      (list proc))
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		       (or (and server-kill-new-buffers
				(not server-existing-buffer))
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			   (server-temp-file-p))
		       (not (buffer-modified-p)))
	      (let (flag)
		(unwind-protect
		    (progn (setq server-buffer-clients nil)
			   (kill-buffer (current-buffer))
			   (setq flag t))
		  (unless flag
		    ;; Restore clients if user pressed C-g in `kill-buffer'.
		    (setq server-buffer-clients (list proc)))))))))
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      ;; Delete the client's frames.
      (unless noframe
	(dolist (frame (frame-list))
	  (when (and (frame-live-p frame)
		     (equal proc (frame-parameter frame 'client)))
	    ;; Prevent `server-handle-delete-frame' from calling us
	    ;; recursively.
	    (set-frame-parameter frame 'client nil)
	    (delete-frame frame))))

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      (setq server-clients (delq proc server-clients))
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      ;; Delete the client's tty.
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      (let ((terminal (process-get proc 'terminal)))
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	;; Only delete the terminal if it is non-nil.
	(when (and terminal (eq (terminal-live-p terminal) t))
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	  (delete-terminal terminal)))
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      ;; Delete the client's process.
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      (if (eq (process-status proc) 'open)
	  (delete-process proc))
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      (server-log "Deleted" proc))))

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(defvar server-log-time-function 'current-time-string
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  "Function to generate timestamps for `server-buffer'.")
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(defconst server-buffer " *server*"
  "Buffer used internally by Emacs's server.
One use is to log the I/O for debugging purposes (see `server-log'),
the other is to provide a current buffer in which the process filter can
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safely let-bind buffer-local variables like `default-directory'.")
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(defvar server-log nil
  "If non-nil, log the server's inputs and outputs in the `server-buffer'.")

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(defun server-log (string &optional client)
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  "If `server-log' is non-nil, log STRING to `server-buffer'.
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If CLIENT is non-nil, add a description of it to the logged message."
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  (when server-log
    (with-current-buffer (get-buffer-create server-buffer)
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      (goto-char (point-max))
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      (insert (funcall server-log-time-function)
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	      (cond
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		((null client) " ")
		((listp client) (format " %s: " (car client)))
		(t (format " %s: " client)))
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	      string)
      (or (bolp) (newline)))))
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(defun server-sentinel (proc msg)
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  "The process sentinel for Emacs server connections."
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  ;; If this is a new client process, set the query-on-exit flag to nil
  ;; for this process (it isn't inherited from the server process).
  (when (and (eq (process-status proc) 'open)
	     (process-query-on-exit-flag proc))
    (set-process-query-on-exit-flag proc nil))
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  ;; Delete the associated connection file, if applicable.
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  ;; Although there's no 100% guarantee that the file is owned by the
  ;; running Emacs instance, server-start uses server-running-p to check
  ;; for possible servers before doing anything, so it *should* be ours.
  (and (process-contact proc :server)
       (eq (process-status proc) 'closed)
       (ignore-errors (delete-file (process-get proc :server-file))))
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  (server-log (format "Status changed to %s: %s" (process-status proc) msg) proc)
  (server-delete-client proc))
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(defun server-select-display (display)
  ;; If the current frame is on `display' we're all set.
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  ;; Similarly if we are unable to open frames on other displays, there's
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  ;; nothing more we can do.
  (unless (or (not (fboundp 'make-frame-on-display))
              (equal (frame-parameter (selected-frame) 'display) display))
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    ;; 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 and select one.
    (unless (equal (frame-parameter (selected-frame) 'display) display)
      (let* ((buffer (generate-new-buffer " *server-dummy*"))
             (frame (make-frame-on-display
                     display
                     ;; Make it display (and remember) some dummy buffer, so
                     ;; we can detect later if the frame is in use or not.
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                     `((server-dummy-buffer . ,buffer)
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                       ;; This frame may be deleted later (see
                       ;; server-unselect-display) so we want it to be as
                       ;; unobtrusive as possible.
                       (visibility . nil)))))
        (select-frame frame)
        (set-window-buffer (selected-window) buffer)
        frame))))

(defun server-unselect-display (frame)
  (when (frame-live-p frame)
    ;; If the temporary frame is in use (displays something real), make it
    ;; visible.  If not (which can happen if the user's customizations call
    ;; pop-to-buffer etc.), delete it to avoid preserving the connection after
    ;; the last real frame is deleted.
    (if (and (eq (frame-first-window frame)
                 (next-window (frame-first-window frame) 'nomini))
             (eq (window-buffer (frame-first-window frame))
                 (frame-parameter frame 'server-dummy-buffer)))
        ;; The temp frame still only shows one buffer, and that is the
        ;; internal temp buffer.
        (delete-frame frame)
      (set-frame-parameter frame 'visibility t))
    (kill-buffer (frame-parameter frame 'server-dummy-buffer))
    (set-frame-parameter frame 'server-dummy-buffer nil)))

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(defun server-handle-delete-frame (frame)
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  "Delete the client connection when the emacsclient frame is deleted.
\(To be used from `delete-frame-functions'.)"
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  (let ((proc (frame-parameter frame 'client)))
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    (when (and (frame-live-p frame)
	       proc
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	       ;; See if this is the last frame for this client.
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	       (>= 1 (let ((frame-num 0))
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		      (dolist (f (frame-list))
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			(when (eq proc (frame-parameter f 'client))
			  (setq frame-num (1+ frame-num))))
		      frame-num)))
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      (server-log (format "server-handle-delete-frame, frame %s" frame) proc)
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      (server-delete-client proc 'noframe)))) ; Let delete-frame delete the frame later.
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(defun server-handle-suspend-tty (terminal)
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  "Notify the emacsclient process to suspend itself when its tty device is suspended."
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  (dolist (proc (server-clients-with 'terminal terminal))
    (server-log (format "server-handle-suspend-tty, terminal %s" terminal) proc)
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    (condition-case err
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	(server-send-string proc "-suspend \n")
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      (file-error                       ;The pipe/socket was closed.
       (ignore-errors (server-delete-client proc))))))
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(defun server-unquote-arg (arg)
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  "Remove &-quotation from ARG.
See `server-quote-arg' and `server-process-filter'."
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  (replace-regexp-in-string
   "&." (lambda (s)
	  (case (aref s 1)
	    (?& "&")
	    (?- "-")
	    (?n "\n")
	    (t " ")))
   arg t t))
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(defun server-quote-arg (arg)
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  "In ARG, insert a & before each &, each space, each newline, and -.
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Change spaces to underscores, too, so that the return value never
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contains a space.

See `server-unquote-arg' and `server-process-filter'."
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  (replace-regexp-in-string
   "[-&\n ]" (lambda (s)
	       (case (aref s 0)
		 (?& "&&")
		 (?- "&-")
		 (?\n "&n")
		 (?\s "&_")))
   arg t t))

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(defun server-send-string (proc string)
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  "A wrapper around `process-send-string' for logging."
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  (server-log (concat "Sent " string) proc)
  (process-send-string proc string))

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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
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      (letf (((default-file-modes) ?\700)) (make-directory dir t))
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      (setq attrs (file-attributes dir)))
    ;; Check that it's safe for use.
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    (unless (and (eq t (car attrs)) (eql (nth 2 attrs) (user-uid))
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                 (or (eq system-type 'windows-nt)
                     (zerop (logand ?\077 (file-modes dir)))))
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      (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
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client \"editors\" can send your editing commands to this Emacs
job.  To use the server, set up the program `emacsclient' in the
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Emacs distribution as your standard \"editor\".

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Optional argument LEAVE-DEAD (interactively, a prefix arg) means just
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kill any existing server communications subprocess.

If a server is already running, the server is not started.
To force-start a server, do \\[server-force-delete] and then
\\[server-start]."
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  (interactive "P")
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  (when (or (not server-clients)
	    ;; Ask the user before deleting existing clients---except
	    ;; when we can't get user input, which may happen when
	    ;; doing emacsclient --eval "(kill-emacs)" in daemon mode.
	    (if (and (daemonp)
		     (null (cdr (frame-list)))
		     (eq (selected-frame) terminal-frame))
		leave-dead
	      (yes-or-no-p
	       "The current server still has clients; delete them? ")))
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    (let* ((server-dir (if server-use-tcp server-auth-dir server-socket-dir))
	   (server-file (expand-file-name server-name server-dir)))
      (when server-process
	;; kill it dead!
	(ignore-errors (delete-process server-process)))
      ;; Delete the socket files made by previous server invocations.
      (if (not (eq t (server-running-p server-name)))
	  ;; Remove any leftover socket or authentication file
	  (ignore-errors (delete-file server-file))
	(setq server-mode nil) ;; already set by the minor mode code
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	(display-warning
	 'server
	 (concat "Unable to start the Emacs server.\n"
		 (format "There is an existing Emacs server, named %S.\n"
			 server-name)
		 "To start the server in this Emacs process, stop the existing
server or call `M-x server-force-delete' to forcibly disconnect it.")
	 :warning)
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	(setq leave-dead t))
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      ;; If this Emacs already had a server, clear out associated status.
      (while server-clients
	(server-delete-client (car server-clients)))
      ;; Now any previous server is properly stopped.
      (if leave-dead
	  (progn
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	    (unless (eq t leave-dead) (server-log (message "Server stopped")))
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	    (setq server-process nil))
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	;; Make sure there is a safe directory in which to place the socket.
	(server-ensure-safe-dir server-dir)
	(when server-process
	  (server-log (message "Restarting server")))
	(letf (((default-file-modes) ?\700))
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	  (add-hook 'suspend-tty-functions 'server-handle-suspend-tty)
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	  (add-hook 'delete-frame-functions 'server-handle-delete-frame)
	  (add-hook 'kill-buffer-query-functions 'server-kill-buffer-query-function)
	  (add-hook 'kill-emacs-query-functions 'server-kill-emacs-query-function)
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	  (add-hook 'kill-emacs-hook (lambda () (server-mode -1))) ;Cleanup upon exit.
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	  (setq server-process
		(apply #'make-network-process
		       :name server-name
		       :server t
		       :noquery t
		       :sentinel 'server-sentinel
		       :filter 'server-process-filter
		       ;; We must receive file names without being decoded.
		       ;; Those are decoded by server-process-filter according
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		       ;; to file-name-coding-system.  Also don't get
		       ;; confused by CRs since we don't quote them.
		       :coding 'raw-text-unix
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		       ;; The other args depend on the kind of socket used.
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		       (if server-use-tcp
			   (list :family nil
				 :service t
				 :host (or server-host 'local)
				 :plist '(:authenticated nil))
			 (list :family 'local
			       :service server-file
			       :plist '(:authenticated t)))))
	  (unless server-process (error "Could not start server process"))
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	  (process-put server-process :server-file server-file)
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	  (when server-use-tcp
	    (let ((auth-key
		   (loop
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		      ;; The auth key is a 64-byte string of random chars in the
		      ;; range `!'..`~'.
		      for i below 64
		      collect (+ 33 (random 94)) into auth
		      finally return (concat auth))))
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	      (process-put server-process :auth-key auth-key)
	      (with-temp-file server-file
		(set-buffer-multibyte nil)
		(setq buffer-file-coding-system 'no-conversion)
		(insert (format-network-address
			 (process-contact server-process :local))
			" " (int-to-string (emacs-pid))
			"\n" auth-key)))))))))
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;;;###autoload
(defun server-force-delete (&optional name)
  "Unconditionally delete connection file for server NAME.
If server is running, it is first stopped.
NAME defaults to `server-name'.  With argument, ask for NAME."
  (interactive
   (list (if current-prefix-arg
	     (read-string "Server name: " nil nil server-name))))
  (when server-mode (with-temp-message nil (server-mode -1)))
  (let ((file (expand-file-name (or name server-name)
				(if server-use-tcp
				    server-auth-dir
				  server-socket-dir))))
    (condition-case nil
	(progn
	  (delete-file file)
	  (message "Connection file %S deleted" file))
      (file-error
       (message "No connection file %S" file)))))

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(defun server-running-p (&optional name)
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  "Test whether server NAME is running.

Return values:
  nil              the server is definitely not running.
  t                the server seems to be running.
  something else   we cannot determine whether it's running without using
                   commands which may have to wait for a long time."
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  (unless name (setq name server-name))
  (condition-case nil
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      (if server-use-tcp
	  (with-temp-buffer
	    (insert-file-contents-literally (expand-file-name name server-auth-dir))
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	    (or (and (looking-at "127\\.0\\.0\\.1:[0-9]+ \\([0-9]+\\)")
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		     (assq 'comm
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			   (process-attributes
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			    (string-to-number (match-string 1))))
		     t)
		:other))
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	(delete-process
	 (make-network-process
	  :name "server-client-test" :family 'local :server nil :noquery t
	  :service (expand-file-name name server-socket-dir)))
	t)
    (file-error nil)))

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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
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  :version "22.1"
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  ;; 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-eval-and-print (expr proc)
  "Eval EXPR and send the result back to client PROC."
  (let ((v (eval (car (read-from-string expr)))))
    (when (and v proc)
      (with-temp-buffer
        (let ((standard-output (current-buffer)))
          (pp v)
          (let ((text (buffer-substring-no-properties
                       (point-min) (point-max))))
            (server-send-string
             proc (format "-print %s\n"
                          (server-quote-arg text)))))))))

(defun server-create-tty-frame (tty type proc)
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  (unless tty
    (error "Invalid terminal device"))
  (unless type
    (error "Invalid terminal type"))
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  (add-to-list 'frame-inherited-parameters 'client)
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  (let ((frame
         (server-with-environment (process-get proc 'env)
             '("LANG" "LC_CTYPE" "LC_ALL"
               ;; For tgetent(3); list according to ncurses(3).
               "BAUDRATE" "COLUMNS" "ESCDELAY" "HOME" "LINES"
               "NCURSES_ASSUMED_COLORS" "NCURSES_NO_PADDING"
               "NCURSES_NO_SETBUF" "TERM" "TERMCAP" "TERMINFO"
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               "TERMINFO_DIRS" "TERMPATH"
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               ;; rxvt wants these
               "COLORFGBG" "COLORTERM")
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	     (make-frame `((window-system . nil)
			   (tty . ,tty)
			   (tty-type . ,type)
			   ;; Ignore nowait here; we always need to
			   ;; clean up opened ttys when the client dies.
			   (client . ,proc)
			   ;; This is a leftover from an earlier
			   ;; attempt at making it possible for process
			   ;; run in the server process to use the
			   ;; environment of the client process.
			   ;; It has no effect now and to make it work
			   ;; we'd need to decide how to make
			   ;; process-environment interact with client
			   ;; envvars, and then to change the
			   ;; C functions `child_setup' and
			   ;; `getenv_internal' accordingly.
			   (environment . ,(process-get proc 'env)))))))
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    ;; ttys don't use the `display' parameter, but callproc.c does to set
    ;; the DISPLAY environment on subprocesses.
    (set-frame-parameter frame 'display
                         (getenv-internal "DISPLAY" (process-get proc 'env)))
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    (select-frame frame)
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    (process-put proc 'frame frame)
    (process-put proc 'terminal (frame-terminal frame))
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    ;; Display *scratch* by default.
    (switch-to-buffer (get-buffer-create "*scratch*") 'norecord)

    ;; Reply with our pid.
    (server-send-string proc (concat "-emacs-pid "
                                     (number-to-string (emacs-pid)) "\n"))
    frame))

(defun server-create-window-system-frame (display nowait proc)
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  (add-to-list 'frame-inherited-parameters 'client)
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  (if (not (fboundp 'make-frame-on-display))
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      (progn
        ;; This emacs does not support X.
        (server-log "Window system unsupported" proc)
        (server-send-string proc "-window-system-unsupported \n")
        nil)
    ;; Flag frame as client-created, but use a dummy client.
    ;; This will prevent the frame from being deleted when
    ;; emacsclient quits while also preventing
    ;; `server-save-buffers-kill-terminal' from unexpectedly
    ;; killing emacs on that frame.
    (let* ((params `((client . ,(if nowait 'nowait proc))
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                     ;; This is a leftover, see above.
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                     (environment . ,(process-get proc 'env))))
           (frame (make-frame-on-display
                   (or display
                       (frame-parameter nil 'display)
                       (getenv "DISPLAY")
                       (error "Please specify display"))
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                   params)))
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      (server-log (format "%s created" frame) proc)
      (select-frame frame)
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      (process-put proc 'frame frame)
      (process-put proc 'terminal (frame-terminal frame))
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      ;; Display *scratch* by default.
      (switch-to-buffer (get-buffer-create "*scratch*") 'norecord)
      frame)))

(defun server-goto-toplevel (proc)
  (condition-case nil
      ;; If we're running isearch, we must abort it to allow Emacs to
      ;; display the buffer and switch to it.
      (dolist (buffer (buffer-list))
        (with-current-buffer buffer
          (when (bound-and-true-p isearch-mode)
            (isearch-cancel))))
    ;; Signaled by isearch-cancel.
    (quit (message nil)))
  (when (> (recursion-depth) 0)
    ;; We're inside a minibuffer already, so if the emacs-client is trying
    ;; to open a frame on a new display, we might end up with an unusable
    ;; frame because input from that display will be blocked (until exiting
    ;; the minibuffer).  Better exit this minibuffer right away.
    ;; Similarly with recursive-edits such as the splash screen.
    (run-with-timer 0 nil (lexical-let ((proc proc))
			    (lambda () (server-execute-continuation proc))))
    (top-level)))

;; We use various special properties on process objects:
;; - `env' stores the info about the environment of the emacsclient process.
;; - `continuation' is a no-arg function that we need to execute.  It contains
;;   commands we wanted to execute in some earlier invocation of the process
;;   filter but that we somehow were unable to process at that time
;;   (e.g. because we first need to throw to the toplevel).

(defun server-execute-continuation (proc)
  (let ((continuation (process-get proc 'continuation)))
    (process-put proc 'continuation nil)
    (if continuation (ignore-errors (funcall continuation)))))

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(defun* server-process-filter (proc string)
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  "Process a request from the server to edit some files.
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PROC is the server process.  STRING consists of a sequence of
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commands prefixed by a dash.  Some commands have arguments;
these are &-quoted and need to be decoded by `server-unquote-arg'.
The filter parses and executes these commands.
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To illustrate the protocol, here is an example command that
emacsclient sends to create a new X frame (note that the whole
sequence is sent on a single line):

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	-env HOME=/home/lorentey
	-env DISPLAY=:0.0
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	... lots of other -env commands
	-display :0.0
	-window-system

The following commands are accepted by the server:

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`-auth AUTH-STRING'
  Authenticate the client using the secret authentication string
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  AUTH-STRING.
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`-env NAME=VALUE'
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  An environment variable on the client side.

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`-dir DIRNAME'
  The current working directory of the client process.

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`-current-frame'
  Forbid the creation of new frames.

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`-nowait'
  Request that the next frame created should not be
  associated with this client.

`-display DISPLAY'
  Set the display name to open X frames on.

`-position LINE[:COLUMN]'
  Go to the given line and column number
  in the next file opened.

`-file FILENAME'
  Load the given file in the current frame.

`-eval EXPR'
  Evaluate EXPR as a Lisp expression and return the
  result in -print commands.

`-window-system'
  Open a new X frame.

`-tty DEVICENAME TYPE'
  Open a new tty frame at the client.

`-suspend'
  Suspend this tty frame.  The client sends this string in
  response to SIGTSTP and SIGTTOU.  The server must cease all I/O
  on this tty until it gets a -resume command.

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`-resume'
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  Resume this tty frame.  The client sends this string when it
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  gets the SIGCONT signal and it is the foreground process on its
  controlling tty.

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`-ignore COMMENT'
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  Do nothing, but put the comment in the server log.
  Useful for debugging.
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The following commands are accepted by the client:

`-emacs-pid PID'
  Describes the process id of the Emacs process;
  used to forward window change signals to it.

`-window-system-unsupported'
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  Signals that the server does not support creating X frames;
  the client must try again with a tty frame.
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`-print STRING'
  Print STRING on stdout.  Used to send values
  returned by -eval.

`-error DESCRIPTION'
  Signal an error (but continue processing).

`-suspend'
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  Suspend this terminal, i.e., stop the client process.
  Sent when the user presses C-z."
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  (server-log (concat "Received " string) proc)
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  ;; First things first: let's check the authentication
  (unless (process-get proc :authenticated)
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    (if (and (string-match "-auth \\([!-~]+\\)\n?" string)
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	     (equal (match-string 1 string) (process-get proc :auth-key)))
	(progn
	  (setq string (substring string (match-end 0)))
	  (process-put proc :authenticated t)
	  (server-log "Authentication successful" proc))
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      (server-log "Authentication failed" proc)
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      (server-send-string
       proc (concat "-error " (server-quote-arg "Authentication failed")))
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      (delete-process proc)
      ;; We return immediately
      (return-from server-process-filter)))
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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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  (condition-case err
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      (progn
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	(server-add-client proc)
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	(if (not (string-match "\n" string))
            ;; Save for later any partial line that remains.
            (when (> (length string) 0)
              (process-put proc 'previous-string string))
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          ;; In earlier versions of server.el (where we used an `emacsserver'
          ;; process), there could be multiple lines.  Nowadays this is not
          ;; supported any more.
          (assert (eq (match-end 0) (length string)))
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	  (let ((request (substring string 0 (match-beginning 0)))
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		(coding-system (and (default-value 'enable-multibyte-characters)
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				    (or file-name-coding-system
					default-file-name-coding-system)))
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		nowait ; t if emacsclient does not want to wait for us.
		frame ; The frame that was opened for the client (if any).
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		display		     ; Open the frame on this display.
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		dontkill       ; t if the client should not be killed.
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		commands
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		dir
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		use-current-frame
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		tty-name       ;nil, `window-system', or the tty name.
		tty-type             ;string.
		files
		filepos
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		command-line-args-left
		arg)
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	    ;; Remove this line from STRING.
	    (setq string (substring string (match-end 0)))
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	    (setq command-line-args-left
		  (mapcar 'server-unquote-arg (split-string request " " t)))
	    (while (setq arg (pop command-line-args-left))
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		(cond
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		 ;; -version CLIENT-VERSION: obsolete at birth.
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		 ((and (equal "-version" arg) command-line-args-left)
		  (pop command-line-args-left))
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		 ;; -nowait:  Emacsclient won't wait for a result.
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		 ((equal "-nowait" arg) (setq nowait t))

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		 ;; -current-frame:  Don't create frames.
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		 ((equal "-current-frame" arg) (setq use-current-frame t))
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		 ;; -display DISPLAY:
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		 ;; Open X frames on the given display instead of the default.
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		 ((and (equal "-display" arg) command-line-args-left)
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		  (setq display (pop command-line-args-left))
                  (if (zerop (length display)) (setq display nil)))
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		 ;; -window-system:  Open a new X frame.
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		 ((equal "-window-system" arg)
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                  (setq dontkill t)
                  (setq tty-name 'window-system))
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		 ;; -resume:  Resume a suspended tty frame.
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		 ((equal "-resume" arg)
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		  (lexical-let ((terminal (process-get proc 'terminal)))
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		    (setq dontkill t)
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                    (push (lambda ()
                            (when (eq (terminal-live-p terminal) t)
                              (resume-tty terminal)))
                          commands)))
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		 ;; -suspend:  Suspend the client's frame.  (In case we
		 ;; get out of sync, and a C-z sends a SIGTSTP to
		 ;; emacsclient.)
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		 ((equal "-suspend" arg)
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		  (lexical-let ((terminal (process-get proc 'terminal)))
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		    (setq dontkill t)
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                    (push (lambda ()
                            (when (eq (terminal-live-p terminal) t)
                              (suspend-tty terminal)))
                          commands)))
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		 ;; -ignore COMMENT:  Noop; useful for debugging emacsclient.
		 ;; (The given comment appears in the server log.)
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		 ((and (equal "-ignore" arg) command-line-args-left
		  (setq dontkill t)
		  (pop command-line-args-left)))
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		 ;; -tty DEVICE-NAME TYPE:  Open a new tty frame at the client.
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		 ((and (equal "-tty" arg)
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                       (cdr command-line-args-left))
                  (setq tty-name (pop command-line-args-left)
			tty-type (pop command-line-args-left)
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			dontkill (or dontkill
				     (not use-current-frame))))
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		 ;; -position LINE[:COLUMN]:  Set point to the given
		 ;;  position in the next file.
		 ((and (equal "-position" arg)
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		       command-line-args-left
                       (string-match "\\+\\([0-9]+\\)\\(?::\\([0-9]+\\)\\)?"
                                     (car command-line-args-left)))
		  (setq arg (pop command-line-args-left))
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		  (setq filepos
                        (cons (string-to-number (match-string 1 arg))
                              (string-to-number (or (match-string 2 arg) "")))))