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 ;; Author Kevin Gallagher
   4 ;; Maintainer: FSF
   5 ;; Last-Modified: 03 Jun 1992
   6 ;; Adapted-By: ESR
   7 ;; Keywords: hardware
   8
   9 ;;; Copyright (C) 1990 Free Software Foundation, Inc.
  10 ;;; Copyright (C) 1991 Kevin Gallagher
  11 ;;;
  12 ;;; GNU Emacs is distributed in the hope that it will be useful, but
  13 ;;; WITHOUT ANY WARRANTY.  No author or distributor accepts
  14 ;;; RESPONSIBILITY TO anyone for the consequences of using it or for
  15 ;;; whether it serves any particular purpose or works at all, unless
  16 ;;; he says so in writing.  Refer to the GNU Emacs General Public
  17 ;;; License for full details.
  18 ;;;
  19 ;;; Everyone is granted permission to copy, modify and redistribute
  20 ;;; GNU Emacs, but only under the conditions described in the GNU
  21 ;;; Emacs General Public License.  A copy of this license is supposed
  22 ;;; to have been given to you along with GNU Emacs so you can know
  23 ;;; your rights and responsibilities.  It should be in a file named
  24 ;;; COPYING.  Among other things, the Copyright notice and this notice
  25 ;;; must be preserved on all copies.
  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 ;;;; evade-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 ;;;;    (evade-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 (defun evade-flow-control ()
  48   "Enable use of flow control; let user type C-s as C-\ and C-q as C-^."
  49   (interactive)
  50   ;; Tell emacs to pass C-s and C-q to OS.
  51   (set-input-mode nil t)
  52   ;; Initialize translate table, saving previous mappings, if any.
  53   (let ((the-table (make-string 128 0)))
  54     (let ((i 0)
  55           (j (length keyboard-translate-table)))
  56       (while (< i j)
  57         (aset the-table i (elt keyboard-translate-table i))
  58         (setq i (1+ i)))
  59       (while (< i 128)
  60         (aset the-table i i)
  61         (setq i (1+ i))))
  62     (setq keyboard-translate-table the-table))
  63   ;; Swap C-s and C-\
  64   (aset keyboard-translate-table ?\034 ?\^s)
  65   (aset keyboard-translate-table ?\^s ?\034)
  66   ;; Swap C-q and C-^
  67   (aset keyboard-translate-table ?\036 ?\^q)
  68   (aset keyboard-translate-table ?\^q ?\036)
  69   (message (concat
  70              "XON/XOFF adjustment for "
  71              (getenv "TERM")
  72              ":  use C-\\ for C-s  and  use C-^ for C-q."))
  73   (sleep-for 2)) ; Give user a chance to see message.
  74
  75 (defun evade-flow-control-memstr= (e s)
  76   (cond ((null s) nil)
  77         ((string= e (car s)) t)
  78         (t (evade-flow-control-memstr= e (cdr s)))))
  79
  80 ;;;###autoload
  81 (defun evade-flow-control-on (&rest losing-terminal-types)
  82   "Enable flow control if using one of a specified set of terminal types.
  83 Use `(evade-flow-control-on \"vt100\" \"h19\")' to enable flow control
  84 on VT-100 and H19 terminals.  When flow control is enabled,
  85 you must type C-\\ to get the effect of a C-s, and type C-^
  86 to get the effect of a C-q."
  87   (let ((term (getenv "TERM"))
  88         hyphend)
  89     ;; Strip off hyphen and what follows
  90     (while (setq hyphend (string-match "[-_][^-_]+$" term))
  91       (setq term (substring term 0 hyphend)))
  92     (and (evade-flow-control-memstr= term losing-terminal-types) (evade-flow-control)))
  93   )
  94
  95 (provide 'flow-ctrl)
  96
  97 ;;; flow-ctrl.el ends here