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 Free Software Foundation, Inc.
5 ;; Author Kevin Gallagher
10 ;; This file is part of GNU Emacs.
12 ;; GNU Emacs is free software; you can redistribute it and/or modify
13 ;; it under the terms of the GNU General Public License as published by
14 ;; the Free Software Foundation; either version 2, or (at your option)
17 ;; GNU Emacs is distributed in the hope that it will be useful,
18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 ;; GNU General Public License for more details.
22 ;; You should have received a copy of the GNU General Public License
23 ;; along with GNU Emacs; see the file COPYING. If not, write to
24 ;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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
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.
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.")
52 (defun enable-flow-control (&optional argument)
53 "Toggle flow control handling.
54 When handling is enabled, user can type C-s as C-\\, and C-q as C-^.
55 With arg, enable flow control mode if arg is positive, otherwise disable."
58 ;; Argument means enable if arg is positive.
59 (<= (prefix-numeric-value argument) 0)
60 ;; No arg means toggle.
61 (nth 1 (current-input-mode)))
63 ;; Turn flow control off, and stop exchanging chars.
64 (set-input-mode t nil (nth 2 (current-input-mode)))
65 (if keyboard-translate-table
67 (aset keyboard-translate-table flow-control-c-s-replacement
68 flow-control-c-s-replacement)
69 (aset keyboard-translate-table ?\^s ?\^s)
70 (aset keyboard-translate-table flow-control-c-q-replacement
71 flow-control-c-q-replacement)
72 (aset keyboard-translate-table ?\^q ?\^q))))
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 (let ((the-table (make-string 128 0)))
79 (j (length keyboard-translate-table)))
81 (aset the-table i (elt keyboard-translate-table i))
86 (setq keyboard-translate-table the-table))
88 (aset keyboard-translate-table flow-control-c-s-replacement ?\^s)
89 (aset keyboard-translate-table ?\^s flow-control-c-s-replacement)
91 (aset keyboard-translate-table flow-control-c-q-replacement ?\^q)
92 (aset keyboard-translate-table ?\^q flow-control-c-q-replacement)
94 "XON/XOFF adjustment for "
96 ": use C-\\ for C-s and use C-^ for C-q."))
97 (sleep-for 2))) ; Give user a chance to see message.
100 (defun enable-flow-control-on (&rest losing-terminal-types)
101 "Enable flow control if using one of a specified set of terminal types.
102 Use `(enable-flow-control-on \"vt100\" \"h19\")' to enable flow control
103 on VT-100 and H19 terminals. When flow control is enabled,
104 you must type C-\\ to get the effect of a C-s, and type C-^
105 to get the effect of a C-q."
106 (let ((term (getenv "TERM"))
110 ;; Strip off hyphen and what follows
111 (while (setq hyphend (string-match "[-_][^-_]+$" term))
112 (setq term (substring term 0 hyphend)))
113 (and (member term losing-terminal-types)
114 (enable-flow-control))))))
118 ;;; flow-ctrl.el ends here