OptionalanchorFor resize chrome: which corner stays pinned. Mirrors the kit's
ResizeAnchor, spelled inline so affordances/ doesn't take a type
dependency on the gesture layer for one field.
Rotation pivot in world coords — the AABB (or union AABB) center.
Id of the rotation target — single selection id, or
MULTI_RESIZE_TARGET_ID for multi-selection.
The fields
buildAffordanceAtlifts out of a region'sinitialScratchwhen it turns a region hit into anAffordanceHit.Scratch is otherwise opaque — whatever the affordance wants to hand the action that picks up the drag. These few names are the exception: they mean the same thing to every affordance, and the actions that consume them (
resizeAction,rotateAction) read them offAffordanceHitrather than out of scratch. An affordance that doesn't set them simply produces a hit without those fields.