根据 16.04 LTS 上的电源更新亮度级别

Question

我最近在东芝 L645 笔记本电脑上从 32 位 14.04 LTS 迁移到 64 位 16.04 LTS。在 14.04 LTS 系统中，我有一个脚本可以根据电源自动更新亮度级别。不幸的是，在覆盖系统之前我没有保存该脚本。目前，我正在使用以下脚本

#!/usr/bin/env bash
#
###########################################################
# Author: Serg Kolo , contact: 1047481448@qq.com 
# Date: February 26 2016 
# Purpose: Brightness control that polls for
#          ac adapter presence. Uses
# Dependencies: on_ac_power script, dbus, Unity/Gnome 
# Written for: http://askubuntu.com/q/739617/295286
# Tested on: Ubuntu 14.04 LTS
###########################################################
# Copyright: Serg Kolo , 2016
#    
#     Permission to use, copy, modify, and distribute this software is hereby granted
#     without fee, provided that  the copyright notice above and this permission statement
#     appear in all copies.
#
#     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
#     IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
#     FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
#     THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
#     LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
#     FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
#     DEALINGS IN THE SOFTWARE.

# uncomment the line bellow for debugging
#set -x

ARGV0="$0"
ARGC=$#


main()
{

  # defaults
  local DISPLAY=:0
  local DECREASE=30
  local INCREASE=75
  local RCFILE="$HOME/.auto-backlightrc"
  #---

  # Check the settings
  if [ -f $RCFILE ]
  then 
       source $RCFILE 
  else
       create_rcfile $DECREASE $INCREASE
  fi
  #---

  # now actually test if we're using ac adapter
  if ! on_ac_power 
  then 
        change_brightness $DECREASE
  # The two lines bellow are optional for 
  # setting brightness if on AC. remove # 
  # if you want to use these two

  # else 
       # change_brightness $INCREASE
  fi

}

change_brightness()
{
  dbus-send --session --print-reply\
    --dest=org.gnome.SettingsDaemon.Power\
    /org/gnome/SettingsDaemon/Power \
    org.gnome.SettingsDaemon.Power.Screen.SetPercentage uint32:"$1"
}

create_rcfile()
{
  echo "DECREASE="$1 >  "$RCFILE"
  echo "INCREASE="$2 >> "$RCFILE"
}


while true
do
   main
   sleep 0.25
done

但是，此脚本仅在电源从交流电切换到电池时有效，并且在交流电重新打开后不会恢复亮度级别。此外，一旦使用电池，此脚本始终会尝试将亮度设置为预定义级别，即使我尝试手动更改它也会重置它。即使在电池模式下，我也希望能够手动更改亮度级别。

Answer 1

塞尔格的剧本一开始似乎很有效。然而，一段时间后，该百分比的评估不正确，尤其是从冬眠回来后。可能存在一些问题，qdbus但亮度水平不会只是改变。因此，我决定使用文件中的值对亮度级别进行硬编码max_brightness。这是我的/usr/local/bin/auto-backlight.sh：

#!/usr/bin/env bash

read MAX_BRIGHTNESS < /sys/class/backlight/intel_backlight/max_brightness

declare -i -r BATT_PERCENTAGE=45 
declare -i -r AC_PERCENTAGE=90 
declare -i -r ON_BATT=$(($MAX_BRIGHTNESS*$BATT_PERCENTAGE/100)) 
declare -i -r ON_AC=$(($MAX_BRIGHTNESS*$AC_PERCENTAGE/100))

wait_ac_connect() {   while ! on_ac_power ; do : ; sleep 0.25 ; done   echo "Adapter plugged in. Brightness level at $ON_AC" }

wait_ac_disconnect() {   while on_ac_power ; do : ; sleep 1.25 ; done  echo "Running on battery. Brightness level at $ON_BATT" }

main() {  
    while true
    do

      if on_ac_power ; then
        wait_ac_disconnect
         echo $ON_BATT > /sys/class/backlight/intel_backlight/brightness
      else
        wait_ac_connect
         echo $ON_AC > /sys/class/backlight/intel_backlight/brightness
      fi

      sleep 0.25

    done

}

main "$@"

与 Serg 的脚本不同，该脚本需要 root 权限才能写入brightness文件。所以我创建了一个systemd serviceat /etc/systemd/system/auto-backlight.service：

[Unit]
Description=Change backlight on power source
ConditionFileIsExecutable=/usr/local/bin/auto-backlight.sh

[Service]
Type=simple
ExecStart=/usr/local/bin/auto-backlight.sh

[Install]
WantedBy=multi-user.target

最后使服务在启动时以 root 权限加载：

sudo systemctl enable auto-backlight.service