Block computer for input, but remain graphical output as usual. Can be used for example to watch a movie on your laptop but forbid any input during that.
Not tested thouroughly yet, and only tested on Debian 9 probably won't work if you already use Compton
sudo apt install compton
Add (depending on what you want) the following lines to your i3 config at ~/.config/i3/config
bindsym $mod+m exec ~/.config/i3/lock_transparent.sh
Create file ~/.config/i3/lock_transparent.sh
with the following contents:
#!/bin/bash
compton --config ~/.config/compton/compton.conf -f &
i3lock_standard -n
pkill compton
execute chmod +x ~/.config/i3/lock_transparent.sh
to make the script executable
Create file ~/.config/compton/compton.conf
with the following contents:
mark-ovredir-focused = true;
inactive-opacity = 0.7;
opacity-rule = [ "0:name *= 'i3lock'" ];
might need to restart or login again, not sure