title: Get ErrorWidget size for rebuild
body: <p>To get the size/position of a widget on screen, I can use GlobalKey to get its BuildContext and then find the RenderBox.</p>
  
  <p>But for ErrorWidget(Red Screen) when build() error happened I want to calculate the error area's size, and then decide whether to destroy the page or replace with other widget e.g. Container().</p>
  
  <p>I have already used ErrorWidget.builder create custom ErrorWidget, but need to be more precise, different sizes of ErrorWidget are treated differently. How to get ErrorWidget size for rebuild?</p>