The paint clip from an ancestor that was applied to this node.
Expressed in the coordinate system of the node. May be null if no clip has been applied.
Descendant SemanticsNodes that are positioned outside of this rect will either be excluded from the semantics tree (if they have no overlap with parentSemanticsClipRect) or they will be included and marked as hidden (if they are overlapping with parentSemanticsClipRect).
This rect is completely enclosed by parentSemanticsClipRect.
If this rect is null parentSemanticsClipRect also has to be null.