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| | ;;; flow-ctrl.el --- help for lusers on cu(1) or ttys with wired-in ^S/^Q flow control
;; Copyright (C) 1990-1991, 1994, 2001-2019 Free Software Foundation,
;; Inc.
;; Author: Kevin Gallagher
;; 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 <https://www.gnu.org/licenses/>.
;;; 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
|