This iterates over all of the TreeEdges in the network, finds the corresponding System.Windows.FrameworkElement, and assigns their FromSpot and/or ToSpot property if the SetsPortSpot and/or SetsChildPortSpot properties are true, and if the port's node only has a single port. The spot values are given by PortSpot and ChildPortSpot respectively, unless the value is Northwoods.GoXam.Spot.Default. In the latter case the actual spot is determined by the TreeVertex.Angle of the parent node (the GenericNetwork.Edge<V,E,Y>.FromVertex). For example, when the angle is zero, the tree grows deeper toward the right. So the FromSpot will be set to Spot.MiddleRight, and the ToSpot will be set to Spot.MiddleLeft.