ChildTransformNode

A node that supplies an additional uniform transform for each placed direct child's effective subtree.

Measurement and ordinary integer placement remain owned by MeasureNode and LayoutNode. After layout, the retained runtime queries this capability on the owning tree thread, scales child-local coordinates, and then adds the transform offset and child's ordinary placement. Descendant portable painting, child clips, pointer hit testing and inverse local coordinates, focus visibility, and semantics bounds share that composed transform. Root-overlay commands remain in root coordinates, while their anchor reflects transformed descendant geometry. Opaque platform payloads remain unchanged, and the current core runtime rejects them during painting unless the composed transform is an exact integer translation. Implementations must invalidate layout when a returned transform can change without remeasurement.

Any failure escapes through the active layout or dependent pipeline operation and follows the owning tree's failure contract.