Launch App with Automator when system is idle

Question

My idea is to dim the display when the system is idle for 10 seconds, and with a keystroke or trackpad activity revert to original (I want to preserve battery automatically and not using a screen saver - I need to monitor some activity but with low display light). I could not find such application so I decided to make solution with Automator.

I found application Shady which can dim display when it start and if it is active (in front) with keystroke Q will quit.

So, how can I make a script in Automator to start Shady when the system is idle for 10 seconds and then wait for any keystroke or trackpad activity, then send keystroke q to quit Shady? The script should be active all the time, so when another 10 second idle time happens, start Shady again.

Answer 1

If you want to actually save energy, use brightness.c instead of Shady. Shady doesn't reduce the backlight levels of displays, and LCDs usually require a similar amount of energy to display dark and bright pixels.

You can see the time since the last human input device (keyboard or mouse) action with ioreg:

ioreg -c IOHIDSystem | awk '/HIDIdleTime/{print $NF/1000000000;exit}'

If you are for example wathing a video with VLC, pmset -g assertions will contain a line like this:

   PreventUserIdleSystemSleep     1

So you might use a script like this:

#!/bin/bash

while sleep 0.5; do
  idle=$(ioreg -c IOHIDSystem | awk '/HIDIdleTime/{printf "%i",$NF/1000000000;exit}')
  current=$(brightness -l | awk '/display 0: brightness/{print $NF}')
  if [[ $idle -ge 10 ]] && pmset -g assertions | grep -q 'PreventUserIdleDisplaySleep *0'; then
    [[ $current != 0.000000 ]] && old=$current
    brightness 0
  else
    [[ $old ]] && brightness $old
  fi
done

It doesn't make any sense to execute over ten new processes every second though.