I would like to debug something in my CSS, and the documentation I read always refers to the principal box. Is there a javascript property or function that prints the coordinates of an element's principal box?

The principal box is defined here: https://developer.mozilla.org/en-US/docs/Web/CSS/Visual_formatting_model#the_principal_box

I can print its visual rectangle with element.offsetTop and similar properties.

Is there such thing for the principal box?

Or does Chrome Developer Tools have something that shows it?