;;; flow-ctrl.el --- help for lusers on cu(1) or ttys with wired-in ^S/^Q flow control ;; Copyright (C) 1990-1991, 1994, 2001-2021 Free Software Foundation, ;; Inc. ;; Author: Kevin Gallagher ;; Maintainer: emacs-devel@gnu.org ;; Adapted-By: ESR ;; Keywords: hardware ;; This file is part of GNU Emacs. ;; GNU Emacs is free software: you can redistribute it and/or modify ;; it under the terms of the GNU General Public License as published by ;; the Free Software Foundation, either version 3 of the License, or ;; (at your option) any later version. ;; GNU Emacs is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;; GNU General Public License for more details. ;; You should have received a copy of the GNU General Public License ;; along with GNU Emacs. If not, see . ;;; Commentary: ;; Terminals that use XON/XOFF flow control can cause problems with ;; GNU Emacs users. This file contains Emacs Lisp code that makes it ;; easy for a user to deal with this problem, when using such a ;; terminal. ;; ;; To invoke these adjustments, a user need only invoke the function ;; enable-flow-control-on with a list of terminal types in his/her own ;; init file. As arguments, give it the names of one or more terminal ;; types in use by that user which require flow control adjustments. ;; Here's an example: ;; ;; (enable-flow-control-on "vt200" "vt300" "vt101" "vt131") ;; Portability note: This uses (getenv "TERM"), and therefore probably ;; won't work outside of UNIX-like environments. ;;; Code: (defvar flow-control-c-s-replacement ?\034 "Character that replaces C-s, when flow control handling is enabled.") (defvar flow-control-c-q-replacement ?\036 "Character that replaces C-q, when flow control handling is enabled.") (put 'keyboard-translate-table 'char-table-extra-slots 0) ;;;###autoload (defun enable-flow-control (&optional argument) "Toggle flow control handling. When handling is enabled, user can type C-s as C-\\, and C-q as C-^. With arg, enable flow control mode if arg is positive, otherwise disable." (interactive "P") (if (if argument ;; Argument means enable if arg is positive. (<= (prefix-numeric-value argument) 0) ;; No arg means toggle. (nth 1 (current-input-mode))) (progn ;; Turn flow control off, and stop exchanging chars. (set-input-mode t nil (nth 2 (current-input-mode))) (if keyboard-translate-table (progn (aset keyboard-translate-table flow-control-c-s-replacement nil) (aset keyboard-translate-table ?\^s nil) (aset keyboard-translate-table flow-control-c-q-replacement nil) (aset keyboard-translate-table ?\^q nil)))) ;; Turn flow control on. ;; Tell emacs to pass C-s and C-q to OS. (set-input-mode nil t (nth 2 (current-input-mode))) ;; Initialize translate table, saving previous mappings, if any. (cond ((null keyboard-translate-table) (setq keyboard-translate-table (make-char-table 'keyboard-translate-table nil))) ((char-table-p keyboard-translate-table) (setq keyboard-translate-table (copy-sequence keyboard-translate-table))) (t (let ((the-table (make-char-table 'keyboard-translate-table nil))) (let ((i 0) (j (length keyboard-translate-table))) (while (< i j) (aset the-table i (elt keyboard-translate-table i)) (setq i (1+ i)))) (setq keyboard-translate-table the-table)))) ;; Swap C-s and C-\ (aset keyboard-translate-table flow-control-c-s-replacement ?\^s) (aset keyboard-translate-table ?\^s flow-control-c-s-replacement) ;; Swap C-q and C-^ (aset keyboard-translate-table flow-control-c-q-replacement ?\^q) (aset keyboard-translate-table ?\^q flow-control-c-q-replacement) (message "XON/XOFF adjustment for %s: use %s for C-s, and use %s for C-q" (getenv "TERM") (single-key-description flow-control-c-s-replacement) (single-key-description flow-control-c-q-replacement)) (sleep-for 2))) ; Give user a chance to see message. ;;;###autoload (defun enable-flow-control-on (&rest losing-terminal-types) "Enable flow control if using one of a specified set of terminal types. Use `(enable-flow-control-on \"vt100\" \"h19\")' to enable flow control on VT-100 and H19 terminals. When flow control is enabled, you must type C-\\ to get the effect of a C-s, and type C-^ to get the effect of a C-q." (let ((term (getenv "TERM")) hyphend) ;; Look for TERM in LOSING-TERMINAL-TYPES. ;; If we don't find it literally, try stripping off words ;; from the end, one by one. (while (and term (not (member term losing-terminal-types))) ;; Strip off last hyphen and what follows, then try again. (if (setq hyphend (string-match "[-_][^-_]+$" term)) (setq term (substring term 0 hyphend)) (setq term nil))) (if term (enable-flow-control)))) (provide 'flow-ctrl) ;;; flow-ctrl.el ends here