y.layout.hierarchic
Class TopologicalLayerer

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

All Implemented Interfaces:

Layerer

public class TopologicalLayerer
extends Object
implements Layerer

This class implements the first phase of the Sugiyama algorithm. It uses topological sorting to assign layers to the nodes.

Field Summary

static byte	DOWN_SHIFT Ranking policy specifier.
static byte	NO_RERANKING Ranking policy specifier.
static byte	TIGHT_TREE Ranking policy specifier.

Constructor Summary

TopologicalLayerer()

Method Summary

int	assignNodeLayer(LayoutGraph g, NodeMap layer, EdgeList reversedEdges) This method assigns the nodes in the graph to layers.
byte	getRankingPolicy() Returns the currently active ranking policy within this layerer.
void	setRankingPolicy(byte p) Sets the (re)ranking policy used within this layerer.

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

Ranking policy specifier. Nodes do not get re-ranked after the initial topological layering step.

See Also:

Constant Field Values

DOWN_SHIFT

public static final byte DOWN_SHIFT

Ranking policy specifier. Nodes get re-ranked by an inexpensive downshift rule.

See Also:

Constant Field Values

TIGHT_TREE

public static final byte TIGHT_TREE

Ranking policy specifier. Nodes get re-ranked by finding a spanning tree that contains only tight (length 1) edges.

See Also:

Constant Field Values

Constructor Detail

TopologicalLayerer

public TopologicalLayerer()

Method Detail

setRankingPolicy

public void setRankingPolicy(byte p)

Sets the (re)ranking policy used within this layerer. By default NO_RERANKING is set.

Parameters:

p - one of NO_RERANKING, DOWN_SHIFT and TIGHT_TREE.

getRankingPolicy

public byte getRankingPolicy()

Returns the currently active ranking policy within this layerer.

See Also:

setRankingPolicy(byte)

assignNodeLayer

public int assignNodeLayer(LayoutGraph g,
                           NodeMap layer,
                           EdgeList reversedEdges)

This method assigns the nodes in the graph to layers.

Specified by:

assignNodeLayer in interface Layerer

Parameters:

g - the graph for which the layers are determined.

layer - here the layers are stored

reversedEdges - here the edges are stored which had been reversed.

Returns:

the number of layers

Postcondition:

Forall (v,w) in E: layer(v) < layer(w)