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, 2001-2012 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 3 of the License, or
  15 ;; (at your option) 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.  If not, see <http://www.gnu.org/licenses/>.
  24
  25 ;;; Commentary:
  26
  27 ;; Terminals that use XON/XOFF flow control can cause problems with
  28 ;; GNU Emacs users.  This file contains Emacs Lisp code that makes it
  29 ;; easy for a user to deal with this problem, when using such a
  30 ;; terminal.
  31 ;;
  32 ;; To invoke these adjustments, a user need only invoke the function
  33 ;; enable-flow-control-on with a list of terminal types in his/her own
  34 ;; init file.  As arguments, give it the names of one or more terminal
  35 ;; types in use by that user which require flow control adjustments.
  36 ;; Here's an example:
  37 ;;
  38 ;;      (enable-flow-control-on "vt200" "vt300" "vt101" "vt131")
  39
  40 ;; Portability note: This uses (getenv "TERM"), and therefore probably
  41 ;; won't work outside of UNIX-like environments.
  42
  43 ;;; Code:
  44
  45 (defvar flow-control-c-s-replacement ?\034
  46   "Character that replaces C-s, when flow control handling is enabled.")
  47 (defvar flow-control-c-q-replacement ?\036
  48   "Character that replaces C-q, when flow control handling is enabled.")
  49
  50 (put 'keyboard-translate-table 'char-table-extra-slots 0)
  51
  52 ;;;###autoload
  53 (defun enable-flow-control (&optional argument)
  54   "Toggle flow control handling.
  55 When handling is enabled, user can type C-s as C-\\, and C-q as C-^.
  56 With arg, enable flow control mode if arg is positive, otherwise disable."
  57   (interactive "P")
  58   (if (if argument
  59           ;; Argument means enable if arg is positive.
  60           (<= (prefix-numeric-value argument) 0)
  61         ;; No arg means toggle.
  62         (nth 1 (current-input-mode)))
  63       (progn
  64         ;; Turn flow control off, and stop exchanging chars.
  65         (set-input-mode t nil (nth 2 (current-input-mode)))
  66         (if keyboard-translate-table
  67             (progn
  68               (aset keyboard-translate-table flow-control-c-s-replacement nil)
  69               (aset keyboard-translate-table ?\^s nil)
  70               (aset keyboard-translate-table flow-control-c-q-replacement nil)
  71               (aset keyboard-translate-table ?\^q nil))))
  72     ;; Turn flow control on.
  73     ;; Tell emacs to pass C-s and C-q to OS.
  74     (set-input-mode nil t (nth 2 (current-input-mode)))
  75     ;; Initialize translate table, saving previous mappings, if any.
  76     (cond ((null keyboard-translate-table)
  77            (setq keyboard-translate-table
  78                  (make-char-table 'keyboard-translate-table nil)))
  79           ((char-table-p keyboard-translate-table)
  80            (setq keyboard-translate-table
  81                  (copy-sequence keyboard-translate-table)))
  82           (t
  83            (let ((the-table (make-char-table 'keyboard-translate-table nil)))
  84              (let ((i 0)
  85                    (j (length keyboard-translate-table)))
  86                (while (< i j)
  87                  (aset the-table i (elt keyboard-translate-table i))
  88                  (setq i (1+ i))))
  89              (setq keyboard-translate-table the-table))))
  90     ;; Swap C-s and C-\
  91     (aset keyboard-translate-table flow-control-c-s-replacement ?\^s)
  92     (aset keyboard-translate-table ?\^s flow-control-c-s-replacement)
  93     ;; Swap C-q and C-^
  94     (aset keyboard-translate-table flow-control-c-q-replacement ?\^q)
  95     (aset keyboard-translate-table ?\^q flow-control-c-q-replacement)
  96     (message "XON/XOFF adjustment for %s: use %s for C-s, and use %s for C-q"
  97              (getenv "TERM")
  98              (single-key-description flow-control-c-s-replacement)
  99              (single-key-description flow-control-c-q-replacement))
 100     (sleep-for 2)))                     ; Give user a chance to see message.
 101
 102 ;;;###autoload
 103 (defun enable-flow-control-on (&rest losing-terminal-types)
 104   "Enable flow control if using one of a specified set of terminal types.
 105 Use `(enable-flow-control-on \"vt100\" \"h19\")' to enable flow control
 106 on VT-100 and H19 terminals.  When flow control is enabled,
 107 you must type C-\\ to get the effect of a C-s, and type C-^
 108 to get the effect of a C-q."
 109   (let ((term (getenv "TERM"))
 110         hyphend)
 111     ;; Look for TERM in LOSING-TERMINAL-TYPES.
 112     ;; If we don't find it literally, try stripping off words
 113     ;; from the end, one by one.
 114     (while (and term (not (member term losing-terminal-types)))
 115       ;; Strip off last hyphen and what follows, then try again.
 116       (if (setq hyphend (string-match "[-_][^-_]+$" term))
 117           (setq term (substring term 0 hyphend))
 118         (setq term nil)))
 119     (if term
 120         (enable-flow-control))))
 121
 122 (provide 'flow-ctrl)
 123
 124 ;;; flow-ctrl.el ends here