anchor.diff:            CreationTimeStamp : int64
             Xtension : Xtension
             Dispatcher : LayerDispatcher
  +          Depth : single
  +          Visible : bool
  +          Persistent : bool
             ScriptOpt : Symbol AssetTag option
             Script : Scripting.Expr array
             ScriptFrame : Scripting.DeclarationFrame
  
positive.code:               OnUnregister = Scripting.Unit
                OnUpdate = Scripting.Unit
                OnPostUpdate = Scripting.Unit
                OnSignal = Scripting.Unit
                TransitionState = IdlingState
                TransitionTicks = 0L // TODO: roll this field into Incoming/OutgoingState values
                Incoming = Transition.make Incoming
                Outgoing = Transition.make Outgoing
                Persistent = true }
  
          /// Try to get an xtension property and its type information.
          static member tryGetProperty propertyName screenState =
  
negative.code:               OnUnregister = Scripting.Unit
                OnUpdate = Scripting.Unit
                OnPostUpdate = Scripting.Unit
                OnSignal = Scripting.Unit }
  
          /// Try to get an xtension property and its type information.
          static member tryGetProperty propertyName layerState =
  