Parent data structure used by parents of slivers that position their
children using layout offsets.
This data structure is optimized for fast layout. It is best used by parents
that expect to have many children whose relative positions don't change even
when the scroll offset does.
The hash code for this object.
The position of the child relative to the zero scroll offset.
read / write
A representation of the runtime type of the object.
Called when the RenderObject is removed from the tree.
Invoked when a non-existent method or property is accessed.
A string representation of this object.