The semantic 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 be excluded from the semantics tree. Descendant SemanticsNodes that are overlapping with this rect, but are outside of parentPaintClipRect will be included in the tree, but they will be marked as hidden because they are assumed to be not visible on screen.