overlayChildBuilder property

A WidgetBuilder used to build a widget below this widget in the tree, that renders on the closest Overlay.

The said widget will only be built and shown in the closest Overlay once OverlayPortalController.show is called on the associated controller. It will be painted in front of the OverlayEntry closest to this widget in the widget tree (which is usually the enclosing Route).

The built overlay child widget is inserted below this widget in the widget tree, allowing it to depend on InheritedWidgets above it, and be notified when the InheritedWidgets change.

Unlike child, the built overlay child can visually extend outside the bounds of this widget without being clipped, and receive hit-test events outside of this widget's bounds, as long as it does not extend outside of the Overlay on which it is rendered.