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;;; vt100-led.el --- functions for LED control on VT-100 terminals & clones -*- lexical-binding:t -*-
;; Copyright (C) 1988, 2001-2021 Free Software Foundation, Inc.
;; Author: Howard Gayle
;; Maintainer: emacs-devel@gnu.org
;; 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:
;;; Code:
(defvar led-state (make-vector 5 nil)
"The internal state of the LEDs. Choices are nil, t, `flash'.
Element 0 is not used.")
(defun led-flash (l)
"Flash LED l."
(aset led-state l 'flash)
(led-update))
(defun led-off (&optional l)
"Turn off vt100 led number L. With no argument, turn them all off."
(interactive "P")
(if l
(aset led-state (prefix-numeric-value l) nil)
(fillarray led-state nil))
(led-update))
(defun led-on (l)
"Turn on LED L."
(aset led-state l t)
(led-update))
(defun led-update ()
"Update the terminal's LEDs to reflect the internal state."
(let ((f "\e[?0") ; String to flash.
(o "\e[0") ; String for steady on.
(l 1)) ; Current LED number.
(while (/= l 5)
(let ((s (aref led-state l)))
(cond
((eq s 'flash)
(setq f (concat f ";" (int-to-string l))))
(s
(setq o (concat o ";" (int-to-string l))))))
(setq l (1+ l)))
(setq o (concat o "q" f "t"))
(send-string-to-terminal o)))
(provide 'vt100-led)
;;; vt100-led.el ends here
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