lisp/flow-ctrl.el

   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 Free Software Foundation, Inc.
   4
   5 ;; Author Kevin Gallagher
   6 ;; Maintainer: FSF
   7 ;; Adapted-By: ESR
   8 ;; Keywords: hardware
   9
  10 ;; This file is part of GNU Emacs.
  11
  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)
  15 ;; any later version.
  16
  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.
  21
  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 the
  24 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  25 ;; Boston, MA 02111-1307, USA.
  26
  27 ;;; Commentary:
  28
  29 ;; Terminals that use XON/XOFF flow control can cause problems with
  30 ;; GNU Emacs users.  This file contains Emacs Lisp code that makes it
  31 ;; easy for a user to deal with this problem, when using such a
  32 ;; terminal.
  33 ;;
  34 ;; To invoke these adjustments, a user need only invoke the function
  35 ;; enable-flow-control-on with a list of terminal types in his/her own
  36 ;; .emacs file.  As arguments, give it the names of one or more terminal
  37 ;; types in use by that user which require flow control adjustments.
  38 ;; Here's an example:
  39 ;;
  40 ;;      (enable-flow-control-on "vt200" "vt300" "vt101" "vt131")
  41
  42 ;; Portability note: This uses (getenv "TERM"), and therefore probably
  43 ;; won't work outside of UNIX-like environments.
  44
  45 ;;; Code:
  46
  47 (defvar flow-control-c-s-replacement ?\034
  48   "Character that replaces C-s, when flow control handling is enabled.")
  49 (defvar flow-control-c-q-replacement ?\036
  50   "Character that replaces C-q, when flow control handling is enabled.")
  51
  52 (put 'keyboard-translate-table 'char-table-extra-slots 0)
  53
  54 ;;;###autoload
  55 (defun enable-flow-control (&optional argument)
  56   "Toggle flow control handling.
  57 When handling is enabled, user can type C-s as C-\\, and C-q as C-^.
  58 With arg, enable flow control mode if arg is positive, otherwise disable."
  59   (interactive "P")
  60   (if (if argument
  61           ;; Argument means enable if arg is positive.
  62           (<= (prefix-numeric-value argument) 0)
  63         ;; No arg means toggle.
  64         (nth 1 (current-input-mode)))
  65       (progn
  66         ;; Turn flow control off, and stop exchanging chars.
  67         (set-input-mode t nil (nth 2 (current-input-mode)))
  68         (if keyboard-translate-table
  69             (progn
  70               (aset keyboard-translate-table flow-control-c-s-replacement nil)
  71               (aset keyboard-translate-table ?\^s nil)
  72               (aset keyboard-translate-table flow-control-c-q-replacement nil)
  73               (aset keyboard-translate-table ?\^q nil))))
  74     ;; Turn flow control on.
  75     ;; Tell emacs to pass C-s and C-q to OS.
  76     (set-input-mode nil t (nth 2 (current-input-mode)))
  77     ;; Initialize translate table, saving previous mappings, if any.
  78     (cond ((null keyboard-translate-table)
  79            (setq keyboard-translate-table
  80                  (make-char-table 'keyboard-translate-table nil)))
  81           ((char-table-p keyboard-translate-table)
  82            (setq keyboard-translate-table
  83                  (copy-sequence keyboard-translate-table)))
  84           (t
  85            (let ((the-table (make-char-table 'keyboard-translate-table nil)))
  86              (let ((i 0)
  87                    (j (length keyboard-translate-table)))
  88                (while (< i j)
  89                  (aset the-table i (elt keyboard-translate-table i))
  90                  (setq i (1+ i))))
  91              (setq keyboard-translate-table the-table))))
  92     ;; Swap C-s and C-\
  93     (aset keyboard-translate-table flow-control-c-s-replacement ?\^s)
  94     (aset keyboard-translate-table ?\^s flow-control-c-s-replacement)
  95     ;; Swap C-q and C-^
  96     (aset keyboard-translate-table flow-control-c-q-replacement ?\^q)
  97     (aset keyboard-translate-table ?\^q flow-control-c-q-replacement)
  98     (message "XON/XOFF adjustment for %s: use %s for C-s, and use %s for C-q"
  99              (getenv "TERM")
 100              (single-key-description flow-control-c-s-replacement)
 101              (single-key-description flow-control-c-q-replacement))
 102     (sleep-for 2)))                     ; Give user a chance to see message.
 103
 104 ;;;###autoload
 105 (defun enable-flow-control-on (&rest losing-terminal-types)
 106   "Enable flow control if using one of a specified set of terminal types.
 107 Use `(enable-flow-control-on \"vt100\" \"h19\")' to enable flow control
 108 on VT-100 and H19 terminals.  When flow control is enabled,
 109 you must type C-\\ to get the effect of a C-s, and type C-^
 110 to get the effect of a C-q."
 111   (let ((term (getenv "TERM"))
 112         hyphend)
 113     ;; Look for TERM in LOSING-TERMINAL-TYPES.
 114     ;; If we don't find it literally, try stripping off words
 115     ;; from the end, one by one.
 116     (while (and term (not (member term losing-terminal-types)))
 117       ;; Strip off last hyphen and what follows, then try again.
 118       (if (setq hyphend (string-match "[-_][^-_]+$" term))
 119           (setq term (substring term 0 hyphend))
 120         (setq term nil)))
 121     (if term
 122         (enable-flow-control))))
 123
 124 (provide 'flow-ctrl)
 125
 126 ;;; flow-ctrl.el ends here