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, 2001-2016 Free Software Foundation,
   4 ;; Inc.
   5
   6 ;; Author: Kevin Gallagher
   7 ;; Maintainer: emacs-devel@gnu.org
   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 of the License, or
  16 ;; (at your option) 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.  If not, see <http://www.gnu.org/licenses/>.
  25
  26 ;;; Commentary:
  27
  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.
  32 ;;
  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 ;; init 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:
  38 ;;
  39 ;;      (enable-flow-control-on "vt200" "vt300" "vt101" "vt131")
  40
  41 ;; Portability note: This uses (getenv "TERM"), and therefore probably
  42 ;; won't work outside of UNIX-like environments.
  43
  44 ;;; Code:
  45
  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.")
  50
  51 (put 'keyboard-translate-table 'char-table-extra-slots 0)
  52
  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)))
  83           (t
  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.
 102
 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))))
 122
 123 (provide 'flow-ctrl)
 124
 125 ;;; flow-ctrl.el ends here