lisp/vt100-led.el

   1 ;;; vt100-led.el --- functions for LED control on VT-100 terminals & clones
   2
   3 ;; Copyright (C) 1988, 2001-2017 Free Software Foundation, Inc.
   4
   5 ;; Author: Howard Gayle
   6 ;; Maintainer: emacs-devel@gnu.org
   7 ;; Keywords: hardware
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software: you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation, either version 3 of the License, or
  14 ;; (at your option) any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
  23
  24 ;;; Commentary:
  25
  26 ;;; Code:
  27
  28 (defvar led-state (make-vector 5 nil)
  29    "The internal state of the LEDs.  Choices are nil, t, `flash'.
  30 Element 0 is not used.")
  31
  32 (defun led-flash (l)
  33   "Flash LED l."
  34   (aset led-state l 'flash)
  35   (led-update))
  36
  37 (defun led-off (&optional l)
  38   "Turn off vt100 led number L.  With no argument, turn them all off."
  39   (interactive "P")
  40   (if l
  41       (aset led-state (prefix-numeric-value l) nil)
  42     (fillarray led-state nil))
  43   (led-update))
  44
  45 (defun led-on (l)
  46   "Turn on LED L."
  47   (aset led-state l t)
  48   (led-update))
  49
  50 (defun led-update ()
  51   "Update the terminal's LEDs to reflect the internal state."
  52   (let ((f "\e[?0")                     ; String to flash.
  53         (o "\e[0")                      ; String for steady on.
  54         (l 1))                          ; Current LED number.
  55     (while (/= l 5)
  56       (let ((s (aref led-state l)))
  57         (cond
  58          ((eq s 'flash)
  59           (setq f (concat f ";" (int-to-string l))))
  60          (s
  61           (setq o (concat o ";" (int-to-string l))))))
  62       (setq l (1+ l)))
  63     (setq o (concat o "q" f "t"))
  64     (send-string-to-terminal o)))
  65
  66 (provide 'vt100-led)
  67
  68 ;;; vt100-led.el ends here