1;;; flow-ctrl.el --- help for lusers on cu(1) or ttys with wired-in ^S/^Q flow control
2
3;; Copyright (C) 1990, 1991, 1994, 2001, 2002, 2003, 2004,
4;;   2005, 2006, 2007 Free Software Foundation, Inc.
5
6;; Author Kevin Gallagher
7;; Maintainer: FSF
8;; Adapted-By: ESR
9;; Keywords: hardware
10
11;; This file is part of GNU Emacs.
12
13;; GNU Emacs is free software; you can redistribute it and/or modify
14;; it under the terms of the GNU General Public License as published by
15;; the Free Software Foundation; either version 2, or (at your option)
16;; any later version.
17
18;; GNU Emacs is distributed in the hope that it will be useful,
19;; but WITHOUT ANY WARRANTY; without even the implied warranty of
20;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
21;; GNU General Public License for more details.
22
23;; You should have received a copy of the GNU General Public License
24;; along with GNU Emacs; see the file COPYING.  If not, write to the
25;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
26;; Boston, MA 02110-1301, USA.
27
28;;; Commentary:
29
30;; Terminals that use XON/XOFF flow control can cause problems with
31;; GNU Emacs users.  This file contains Emacs Lisp code that makes it
32;; easy for a user to deal with this problem, when using such a
33;; terminal.
34;;
35;; To invoke these adjustments, a user need only invoke the function
36;; enable-flow-control-on with a list of terminal types in his/her own
37;; .emacs file.  As arguments, give it the names of one or more terminal
38;; types in use by that user which require flow control adjustments.
39;; Here's an example:
40;;
41;;	(enable-flow-control-on "vt200" "vt300" "vt101" "vt131")
42
43;; Portability note: This uses (getenv "TERM"), and therefore probably
44;; won't work outside of UNIX-like environments.
45
46;;; Code:
47
48(defvar flow-control-c-s-replacement ?\034
49  "Character that replaces C-s, when flow control handling is enabled.")
50(defvar flow-control-c-q-replacement ?\036
51  "Character that replaces C-q, when flow control handling is enabled.")
52
53(put 'keyboard-translate-table 'char-table-extra-slots 0)
54
55;;;###autoload
56(defun enable-flow-control (&optional argument)
57  "Toggle flow control handling.
58When handling is enabled, user can type C-s as C-\\, and C-q as C-^.
59With arg, enable flow control mode if arg is positive, otherwise disable."
60  (interactive "P")
61  (if (if argument
62	  ;; Argument means enable if arg is positive.
63	  (<= (prefix-numeric-value argument) 0)
64	;; No arg means toggle.
65	(nth 1 (current-input-mode)))
66      (progn
67	;; Turn flow control off, and stop exchanging chars.
68	(set-input-mode t nil (nth 2 (current-input-mode)))
69	(if keyboard-translate-table
70	    (progn
71	      (aset keyboard-translate-table flow-control-c-s-replacement nil)
72	      (aset keyboard-translate-table ?\^s nil)
73	      (aset keyboard-translate-table flow-control-c-q-replacement nil)
74	      (aset keyboard-translate-table ?\^q nil))))
75    ;; Turn flow control on.
76    ;; Tell emacs to pass C-s and C-q to OS.
77    (set-input-mode nil t (nth 2 (current-input-mode)))
78    ;; Initialize translate table, saving previous mappings, if any.
79    (cond ((null keyboard-translate-table)
80	   (setq keyboard-translate-table
81		 (make-char-table 'keyboard-translate-table nil)))
82	  ((char-table-p keyboard-translate-table)
83	   (setq keyboard-translate-table
84		 (copy-sequence keyboard-translate-table)))
85	  (t
86	   (let ((the-table (make-char-table 'keyboard-translate-table nil)))
87	     (let ((i 0)
88		   (j (length keyboard-translate-table)))
89	       (while (< i j)
90		 (aset the-table i (elt keyboard-translate-table i))
91		 (setq i (1+ i))))
92	     (setq keyboard-translate-table the-table))))
93    ;; Swap C-s and C-\
94    (aset keyboard-translate-table flow-control-c-s-replacement ?\^s)
95    (aset keyboard-translate-table ?\^s flow-control-c-s-replacement)
96    ;; Swap C-q and C-^
97    (aset keyboard-translate-table flow-control-c-q-replacement ?\^q)
98    (aset keyboard-translate-table ?\^q flow-control-c-q-replacement)
99    (message "XON/XOFF adjustment for %s: use %s for C-s, and use %s for C-q"
100	     (getenv "TERM")
101	     (single-key-description flow-control-c-s-replacement)
102	     (single-key-description flow-control-c-q-replacement))
103    (sleep-for 2)))			; Give user a chance to see message.
104
105;;;###autoload
106(defun enable-flow-control-on (&rest losing-terminal-types)
107  "Enable flow control if using one of a specified set of terminal types.
108Use `(enable-flow-control-on \"vt100\" \"h19\")' to enable flow control
109on VT-100 and H19 terminals.  When flow control is enabled,
110you must type C-\\ to get the effect of a C-s, and type C-^
111to get the effect of a C-q."
112  (let ((term (getenv "TERM"))
113	hyphend)
114    ;; Look for TERM in LOSING-TERMINAL-TYPES.
115    ;; If we don't find it literally, try stripping off words
116    ;; from the end, one by one.
117    (while (and term (not (member term losing-terminal-types)))
118      ;; Strip off last hyphen and what follows, then try again.
119      (if (setq hyphend (string-match "[-_][^-_]+$" term))
120	  (setq term (substring term 0 hyphend))
121	(setq term nil)))
122    (if term
123	(enable-flow-control))))
124
125(provide 'flow-ctrl)
126
127;;; arch-tag: 0eb7b19e-0d93-4e0b-9ea2-72b574076a56
128;;; flow-ctrl.el ends here
129