lisp/flow-ctrl.el

   1 ;;; flow-ctrl.el --- help for lusers on cu(1) or terminals with wired-in ^S/^Q flow control
   2
   3 ;;; Copyright (C) 1990 Free Software Foundation, Inc.
   4 ;;; Copyright (C) 1991 Kevin Gallagher
   5 ;;; Adapted for Emacs 19 by Eric S. Raymond <eric@snark.thyrsus.com>
   6 ;;;
   7 ;;; GNU Emacs is distributed in the hope that it will be useful, but
   8 ;;; WITHOUT ANY WARRANTY.  No author or distributor accepts
   9 ;;; RESPONSIBILITY TO anyone for the consequences of using it or for
  10 ;;; whether it serves any particular purpose or works at all, unless
  11 ;;; he says so in writing.  Refer to the GNU Emacs General Public
  12 ;;; License for full details.
  13 ;;;
  14 ;;; Everyone is granted permission to copy, modify and redistribute
  15 ;;; GNU Emacs, but only under the conditions described in the GNU
  16 ;;; Emacs General Public License.  A copy of this license is supposed
  17 ;;; to have been given to you along with GNU Emacs so you can know
  18 ;;; your rights and responsibilities.  It should be in a file named
  19 ;;; COPYING.  Among other things, the Copyright notice and this notice
  20 ;;; must be preserved on all copies.
  21 ;;;
  22
  23 ;;;; Terminals that use XON/XOFF flow control can cause problems with
  24 ;;;; GNU Emacs users.  This file contains elisp code that makes it
  25 ;;;; easy for a user to deal with this problem, when using such a
  26 ;;;; terminal.
  27 ;;;;
  28 ;;;; To invoke these adjustments, a user need only invoke the function
  29 ;;;; evade-flow-control-on with a list of terminal types in his/her own
  30 ;;;; .emacs file.  As arguments, give it the names of one or more terminal
  31 ;;;; types in use by that user which require flow control adjustments.
  32 ;;;; Here's an example:
  33 ;;;;
  34 ;;;;    (evade-flow-control-on "vt200" "vt300" "vt101" "vt131")
  35
  36 ;;; Portability note: This uses (getenv "TERM"), and therefore probably
  37 ;;; won't work outside of UNIX-like environments.
  38
  39 (defun evade-flow-control ()
  40   "Replace C-s with C-\ and C-q with C-^ and tell emacs to pass C-s
  41 and C-q characters to OS."
  42   (interactive)
  43   ;; Tell emacs to pass C-s and C-q to OS.
  44   (set-input-mode nil t)
  45   ;; Initialize translate table, saving previous mappings, if any.
  46   (let ((the-table (make-string 128 0)))
  47     (let ((i 0)
  48           (j (length keyboard-translate-table)))
  49       (while (< i j)
  50         (aset the-table i (elt keyboard-translate-table i))
  51         (setq i (1+ i)))
  52       (while (< i 128)
  53         (aset the-table i i)
  54         (setq i (1+ i))))
  55     (setq keyboard-translate-table the-table))
  56   ;; Swap C-s and C-\
  57   (aset keyboard-translate-table ?\034 ?\^s)
  58   (aset keyboard-translate-table ?\^s ?\034)
  59   ;; Swap C-q and C-^
  60   (aset keyboard-translate-table ?\036 ?\^q)
  61   (aset keyboard-translate-table ?\^q ?\036)
  62   (message (concat
  63              "XON/XOFF adjustment for "
  64              (getenv "TERM")
  65              ":  use C-\\ for C-s  and  use C-^ for C-q."))
  66   (sleep-for 2)) ; Give user a chance to see message.
  67
  68 (defun memstr= (e s)
  69   (cond ((null s) nil)
  70         ((string= e (car s)) t)
  71         (t (memstr= e (cdr s)))))
  72
  73 ;;;###autoload
  74 (defun evade-flow-control-on (&rest losing-terminal-types)
  75   (let ((term (getenv "TERM"))
  76         hyphend)
  77     ;; Strip off hyphen and what follows
  78     (while (setq hyphend (string-match "[-_][^-_]+$" term))
  79       (setq term (substring term 0 hyphend)))
  80     (and (memstr= term losing-terminal-types) (evade-flow-control)))
  81   )
  82
  83 (provide 'flow-ctrl)
  84
  85 ;;; flow-ctrl.el ends here