https://api.dart.dev/stable/2.10.4/dart-html/Element/offsetParent.html
offsetParent property - Element class - dart:html library - Dart API
API docs for the offsetParent property from the Element class, for the Dart programming language.
offsetparentpropertyelementclassdart
https://ofstack.com/javascript/41163/a-brief-talk-on-offsetleft--offsettop--and-offsetparent.html
A Brief Talk on offsetleft offsetTop and offsetParent
A Brief Talk on offsetleft offsetTop and offsetParent
brieftalkoffsetparent