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, 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 3, 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.
  58 When handling is enabled, user can type C-s as C-\\, and C-q as C-^.
  59 With 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.
 108 Use `(enable-flow-control-on \"vt100\" \"h19\")' to enable flow control
 109 on VT-100 and H19 terminals.  When flow control is enabled,
 110 you must type C-\\ to get the effect of a C-s, and type C-^
 111 to 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