Event listener when printing in silent mode.

I have an application using printJS, and I have the following call:

printJS({
printable: printableContent,
type: 'raw-html',
onPrintDialogClose: myMethod,
title: 'My Title'
});

I need to print silently (ex. print.always_print_silent on Firefox). Which I have configured in my client browser successfully.

I have also added the following event listeners for "focus" and "afterprint"...

window.addEventListener("afterprint", function(event)
{
myMethod();
});

window.addEventListener("focus", function(event)
{
myMethod();
});

However, none of these event listeners get triggered when I'm in silent print mode. The onPrintDialogClose feature does not get triggered either.

How do I determine when the print job finishes if I'm in silent print mode?