Semi-intelligent screensaver

A couple of days ago, I described a couple of interesting ways to interact with KDE using the D-Bus message bus. Today I will show how to set up a semi-intelligent screensaver to just wait during YouTube video playback.

Let’s start and create a simple shell script

This simple shell script will simulate user activity if session idle time is greater than 50 seconds and Google Chrome uses more than 5% CPU. It will prevent the screensaver from kicking in when I am watching YouTube videos.

#!/bin/sh
# Simple script to demonstrate D-Bus usage

while true
do
  # read google chrome cpu usage
  ret=`top -b -n1 -u $(whoami) | awk '$12 ~ /chrome/ {SUM += $9} END {print SUM}'`

  if [ -n "$ret" ] && [ "$ret" -gt 5 ]; then
    idle_time=`qdbus org.kde.screensaver /ScreenSaver GetSessionIdleTime`
    if [ "$idle_time" -gt 50 ]; then
      qdbus org.kde.screensaver /ScreenSaver SimulateUserActivity
    fi
  fi

  sleep 50
done

This script is designed to run in the background. The easiest way to execute it on KDE startup is to open System Settings > Startup and Shutdown > Autostart and add it there.

Try a different approach

You can try a different approach and use xautolock utility as it provides a couple of nice features (exciting possibilities to extend screensaver behavior).

Install xautolock.

$ sudo apt-get install xautolock

The previously created script can be simplified because xautolock will monitor user activity.

#!/bin/sh
# Simple script to demonstrate xautolock usage

# read google chrome cpu usage
ret=`top -n1 | awk '$12 ~ /chrome/ {SUM += $9} END {print SUM}'`

if [ -n "$ret" ] && [ "$ret" -gt 5 ]; then
  qdbus org.kde.screensaver /ScreenSaver SimulateUserActivity
fi

To execute the above script, use a similar command.

$ xautolock -time 1 -locker /home/milosz/bin/suppress_screensaver_xautolock.sh

This utility is designed to activate the screensaver, but it doesn’t mean that it cannot be used otherwise 😉

Let’s extend the idea and write a Ruby script

This is a more advanced solution as it uses Inhibit and UnInhibit methods to suppress screensaver. Just remember that you don’t need to call UnInhibit on exit as the cookie will be dropped automatically.

#!/usr/bin/env ruby

require 'dbus'

session_bus  = DBus::SessionBus.instance
screen_saver = session_bus.service("org.freedesktop.ScreenSaver").object("/ScreenSaver");
screen_saver.introspect
screen_saver.default_iface="org.freedesktop.ScreenSaver";

chrome_check="top -n1 | awk \'$12 ~ /chrome/ {SUM += $9} END {print SUM}\'"
play_sound="play -q /usr/share/sounds/KDE-Window-All-Desktops-Not.ogg"
cookie = nil

loop do
  # read google chrome cpu usage
  ret=%x[#{chrome_check}]

  if ret.to_i > 5 then
    # google chrome cpu usage is greater than 5 so suspend screensaver
    if cookie == nil then
      cookie = screen_saver.Inhibit("google-chrome", "playing video").first
    end
  else
    # google chrome cpu usage is less than 6 so resume normal screensaver behaviour
    if cookie != nil
      screen_saver.UnInhibit(cookie)
      cookie = nil
      %x[#{play_sound}]
    end
  end

  # repeat loop every 1 minute
  sleep 60
end

Execute the above script at the KDE session startup in the same way as the first script.

Notes

You can extend scripts mentioned here to perform different actions depending on the time of the day or running applications.

For a reason unknown to me HasInhibit method will return false if power management is enabled, but it doesn’t prevent the ruby script from working.

$ qdbus org.freedesktop.PowerManagement /org/freedesktop/PowerManagement/Inhibit HasInhibit

To read more about D-Bus actions, look at my previous post How to automate KDE using D-Bus.