com.yworks.yfiles.layout.hierarchic

Class BFSLayerer

java.lang.Object

com.yworks.yfiles.layout.hierarchic.BFSLayerer

All Implemented Interfaces:

ILayerer

public class BFSLayerer
extends Object
implements ILayerer

BFSLayerer uses a breadth first search for assigning layers to the nodes.

The nodes of the first layer can be freely selected (see CORE_NODES_DPKEY). The nodes that belong to a subsequent layer are determined as follows: Add all yet unassigned nodes to the new layer that are connected to nodes already assigned. As a consequence, all connected nodes will be at most one layer apart. Also, edges between nodes that belong to the same layer are possible.

Field Summary

Fields

Modifier and Type	Field and Description
static NodeDpKey<Boolean>	CORE_NODES_DPKEY A DataProvider key for identifying the core nodes of the BFS layering.

Constructor Summary

Constructors

Constructor and Description
BFSLayerer() Creates an instance of BFSLayerer.

Method Summary

Modifier and Type	Method and Description
void	assignLayers(LayoutGraph graph, ILayers layers, ILayoutDataProvider ldp) Assigns all nodes of the graph to layers and adds them to the ILayers instance.
int	assignNodeLayer(LayoutGraph graph, INodeMap layerID, EdgeList reversedEdges) Assigns the nodes of the graph to layers.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

CORE_NODES_DPKEY

public static final NodeDpKey<Boolean> CORE_NODES_DPKEY

A DataProvider key for identifying the core nodes of the BFS layering.

The IDataProvider registered with this key should provide boolean values for the nodes of the graph. The boolean value determines whether or not a node is to be placed in the first layer. If there are no nodes marked as core nodes, then nodes with in-degree 0 are considered to be the core nodes.

Constructor Detail

BFSLayerer

public BFSLayerer()

Creates an instance of BFSLayerer.

Method Detail

assignLayers

public void assignLayers(LayoutGraph graph,
                         ILayers layers,
                         ILayoutDataProvider ldp)

Assigns all nodes of the graph to layers and adds them to the ILayers instance.

Specified by:

assignLayers in interface ILayerer

Parameters:

graph - the input graph

layers - the ILayers instance that will be filled with the results of the calculation

ldp - the ILayoutDataProvider used for query information about the nodes and edges

See Also:

ILayers.insert(com.yworks.yfiles.layout.hierarchic.LayerType, int), ILayer.add(com.yworks.yfiles.algorithms.Node)

assignNodeLayer

public int assignNodeLayer(LayoutGraph graph,
                           INodeMap layerID,
                           EdgeList reversedEdges)

Assigns the nodes of the graph to layers.

Postcondition:

For all (v,w) in E: layer(v) < layer(w).

Parameters:

graph - the given graph

layerID - the INodeMap that will be filled by the layout algorithm and returns the zero-based index of the layer to which each node belongs

reversedEdges - an EdgeList containing the edges which had been reversed

Returns:

the number of layers