y.layout.hierarchic
Class TopologicalLayerer

java.lang.Object
  y.layout.hierarchic.TopologicalLayerer

All Implemented Interfaces:

Layerer

public class TopologicalLayerer
extends java.lang.Object
implements Layerer, Layerer

This class implements the layering phase of the IncrementalHierarchicLayouter (i.e., assignment of the nodes to layers).

It uses topological sorting to assign layers to the nodes.

This class can be used with IncrementalHierarchicLayouter as well as HierarchicLayouter and HierarchicGroupLayouter.

Field Summary

static byte	DOWN_SHIFT A ranking policy that specifies that nodes are re-ranked by an inexpensive downshift rule.
static byte	NO_RERANKING A ranking policy that specifies that nodes are not re-ranked after the initial topological layering step.
static byte	TIGHT_TREE A ranking policy that specifies that nodes are re-ranked by finding a spanning tree that contains only tight (length 1) edges.

Constructor Summary

TopologicalLayerer()
Creates a new instance of TopologicalLayerer with default settings.

Method Summary

void	assignLayers(LayoutGraph graph, Layers layers, LayoutDataProvider ldp) Assigns all nodes of the graph to layers and adds them to the Layers instance.
int	assignNodeLayer(LayoutGraph graph, NodeMap layerID, EdgeList reversedEdges) This method assigns the nodes in the graph to layers.
byte	getRankingPolicy() Returns the (re-)ranking policy used by this TopologicalLayerer instance.
void	setRankingPolicy(byte p) Specifies the (re-)ranking policy used by this TopologicalLayerer instance.

Methods inherited from class java.lang.Object

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

Field Detail

NO_RERANKING

public static final byte NO_RERANKING

A ranking policy that specifies that nodes are not re-ranked after the initial topological layering step.

See Also:

Constant Field Values

Sample Graph:

DOWN_SHIFT

public static final byte DOWN_SHIFT

A ranking policy that specifies that nodes are re-ranked by an inexpensive downshift rule.

See Also:

Constant Field Values

Sample Graph:

TIGHT_TREE

public static final byte TIGHT_TREE

A ranking policy that specifies that nodes are re-ranked by finding a spanning tree that contains only tight (length 1) edges.

See Also:

Constant Field Values

Sample Graph:

Constructor Detail

TopologicalLayerer

public TopologicalLayerer()

Creates a new instance of TopologicalLayerer with default settings.

Method Detail

setRankingPolicy

public void setRankingPolicy(byte p)

Specifies the (re-)ranking policy used by this TopologicalLayerer instance.

Default Value:

The default value is NO_RERANKING

Parameters:

p - one of the predefined ranking policies

Throws:

java.lang.IllegalArgumentException - if an unknown ranking policy is given

getRankingPolicy

public byte getRankingPolicy()

Returns the (re-)ranking policy used by this TopologicalLayerer instance.

Returns:

one of the predefined ranking policies

See Also:

setRankingPolicy(byte)

assignNodeLayer

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

This method assigns the nodes in the graph to layers.

Postcondition:

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

Parameters:

graph - the given graph

layerID - the NodeMap 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

assignLayers

public void assignLayers(LayoutGraph graph,
                         Layers layers,
                         LayoutDataProvider ldp)

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

Specified by:

assignLayers in interface Layerer

Parameters:

graph - the input graph

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

ldp - the LayoutDataProvider used for querying information about the nodes and edges

See Also:

Layers.insert(byte, int), Layer.add(y.base.Node)