backlighter

Linux laptop screen and kepboard brightness control

By Paul H Alfille 2021 MIT license

Summary

Simple controls for some laptop backlight and keyboard lights under linux

Background

Pixel 2013

Inspiration was a repurposed Google Chromebook Pixel 2013

See pixel2013 for the full story.

This program addresses screen and keyboard brightness for a number of devices where that capability is exposed in the /sys/class/ virtual file system

Backlighter

• This project is a fork of the pixel2013
  • Still supports the Google Pixel Chromebook 2013 version
  • Development work done here
  • Any improvements here will be back-ported

Install

• Download source git clone http://github.com/alfille/backlighter
• Compile make all
• Install sudo make install
• This wil; install
  • command line tools
  • graphics tools
  • menu entry
• Full script:

git clone http://github.com/alfille/backlighter
cd backlighter
make all
sudo make install

• The following python3 modules are required (but fortunately are part of the standard distribution)
  • sys
  • signal
  • tkinter tkinter.ttk tkinter.font
  • pathlib.Path

Usage

command line tool

brightness [-b|-k] number -- in percent

brightness -- set the screen or keyboard brightness level for the Google Pixel Chromebook (2013)

Writes to /sys/class -- needs root privileges
by Paul H Alfille 2021

	brightness -b -- show backlight percent
	brightness -b 43-- set backlight percent

	brightness -k -- show keylight percent
	brightness -k 43-- set keylight percent

	brightness -b (screen backlight) is assumed if k or b not specified

	brightness -h -- this help

graphical tool

• Program name is backlighter
  • installed in /usr/bin
  • setsuid (i.e. root privileges)
  • calls python3 program pybacklight.py in turn
• pybacklight.py is the actual program displayed
  • For problems, run sudo python3 ./pybacklight.py from a terminal to see error output
  • python3 program with tkinter graphics so should need very few additional libraries
• Desktop icon and menu support
  • backlighter.desktop is included
  • menu entry should be added automatically if window manager supports OpenDesktop protocols
• Controls for graphical application: key
• Setting shortcut keys for brightness levels
  • Shortcut works when mouse hovers over screen
  • Open shortcut menu -- right-click "+" and "-" buttons
  • Setting shortcut when menu is open
  • Click chosen key while hovering over menu
  • Clear key from same menu

Security

The controls require root access and so are setsuid programs (which is a possible security risk), but allow very circumscribed and sanitized input.

Uses the controls are exposed by the operating system in a virtual filesystem:

• /sys/class/backlight/xxxxx/backlight
• /sys/class/leds/xxxxx/backlight