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[emacs.git] / lisp / flow-ctrl.el
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1 ;;; flow-ctrl.el --- help for lusers on cu(1) or ttys with wired-in ^S/^Q flow control
3 ;; Copyright (C) 1990, 1991, 1994, 2001, 2002, 2003, 2004, 2005, 2006,
4 ;; 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
6 ;; Author: Kevin Gallagher
7 ;; Maintainer: FSF
8 ;; Adapted-By: ESR
9 ;; Keywords: hardware
11 ;; This file is part of GNU Emacs.
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 3 of the License, or
16 ;; (at your option) any later version.
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.
23 ;; You should have received a copy of the GNU General Public License
24 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
26 ;;; Commentary:
28 ;; Terminals that use XON/XOFF flow control can cause problems with
29 ;; GNU Emacs users. This file contains Emacs Lisp code that makes it
30 ;; easy for a user to deal with this problem, when using such a
31 ;; terminal.
33 ;; To invoke these adjustments, a user need only invoke the function
34 ;; enable-flow-control-on with a list of terminal types in his/her own
35 ;; .emacs file. As arguments, give it the names of one or more terminal
36 ;; types in use by that user which require flow control adjustments.
37 ;; Here's an example:
39 ;; (enable-flow-control-on "vt200" "vt300" "vt101" "vt131")
41 ;; Portability note: This uses (getenv "TERM"), and therefore probably
42 ;; won't work outside of UNIX-like environments.
44 ;;; Code:
46 (defvar flow-control-c-s-replacement ?\034
47 "Character that replaces C-s, when flow control handling is enabled.")
48 (defvar flow-control-c-q-replacement ?\036
49 "Character that replaces C-q, when flow control handling is enabled.")
51 (put 'keyboard-translate-table 'char-table-extra-slots 0)
53 ;;;###autoload
54 (defun enable-flow-control (&optional argument)
55 "Toggle flow control handling.
56 When handling is enabled, user can type C-s as C-\\, and C-q as C-^.
57 With arg, enable flow control mode if arg is positive, otherwise disable."
58 (interactive "P")
59 (if (if argument
60 ;; Argument means enable if arg is positive.
61 (<= (prefix-numeric-value argument) 0)
62 ;; No arg means toggle.
63 (nth 1 (current-input-mode)))
64 (progn
65 ;; Turn flow control off, and stop exchanging chars.
66 (set-input-mode t nil (nth 2 (current-input-mode)))
67 (if keyboard-translate-table
68 (progn
69 (aset keyboard-translate-table flow-control-c-s-replacement nil)
70 (aset keyboard-translate-table ?\^s nil)
71 (aset keyboard-translate-table flow-control-c-q-replacement nil)
72 (aset keyboard-translate-table ?\^q nil))))
73 ;; Turn flow control on.
74 ;; Tell emacs to pass C-s and C-q to OS.
75 (set-input-mode nil t (nth 2 (current-input-mode)))
76 ;; Initialize translate table, saving previous mappings, if any.
77 (cond ((null keyboard-translate-table)
78 (setq keyboard-translate-table
79 (make-char-table 'keyboard-translate-table nil)))
80 ((char-table-p keyboard-translate-table)
81 (setq keyboard-translate-table
82 (copy-sequence keyboard-translate-table)))
84 (let ((the-table (make-char-table 'keyboard-translate-table nil)))
85 (let ((i 0)
86 (j (length keyboard-translate-table)))
87 (while (< i j)
88 (aset the-table i (elt keyboard-translate-table i))
89 (setq i (1+ i))))
90 (setq keyboard-translate-table the-table))))
91 ;; Swap C-s and C-\
92 (aset keyboard-translate-table flow-control-c-s-replacement ?\^s)
93 (aset keyboard-translate-table ?\^s flow-control-c-s-replacement)
94 ;; Swap C-q and C-^
95 (aset keyboard-translate-table flow-control-c-q-replacement ?\^q)
96 (aset keyboard-translate-table ?\^q flow-control-c-q-replacement)
97 (message "XON/XOFF adjustment for %s: use %s for C-s, and use %s for C-q"
98 (getenv "TERM")
99 (single-key-description flow-control-c-s-replacement)
100 (single-key-description flow-control-c-q-replacement))
101 (sleep-for 2))) ; Give user a chance to see message.
103 ;;;###autoload
104 (defun enable-flow-control-on (&rest losing-terminal-types)
105 "Enable flow control if using one of a specified set of terminal types.
106 Use `(enable-flow-control-on \"vt100\" \"h19\")' to enable flow control
107 on VT-100 and H19 terminals. When flow control is enabled,
108 you must type C-\\ to get the effect of a C-s, and type C-^
109 to get the effect of a C-q."
110 (let ((term (getenv "TERM"))
111 hyphend)
112 ;; Look for TERM in LOSING-TERMINAL-TYPES.
113 ;; If we don't find it literally, try stripping off words
114 ;; from the end, one by one.
115 (while (and term (not (member term losing-terminal-types)))
116 ;; Strip off last hyphen and what follows, then try again.
117 (if (setq hyphend (string-match "[-_][^-_]+$" term))
118 (setq term (substring term 0 hyphend))
119 (setq term nil)))
120 (if term
121 (enable-flow-control))))
123 (provide 'flow-ctrl)
125 ;; arch-tag: 0eb7b19e-0d93-4e0b-9ea2-72b574076a56
126 ;;; flow-ctrl.el ends here