de.grogra.graph

Interface Visitor

All Known Implementing Classes:

DisplayVisitor, FluxLightVisitor, FluxSceneVisitor, GL20DisplayVisitor, GLDisplay.GLVisitor, GLSLUpdateCache, PickRayVisitor, SceneTree, SceneTreeWithShader, SceneVisitor, Tree, Visitor3D, VisitorImpl

public interface Visitor

A Visitor is a callback-instance which is informed about the structure of a graph via invocation of Graph.accept(Object, Visitor, ArrayPath). It follows the design pattern of hierarchical visitors: For every node and edge of the graph, the corresponding methods visitEnter and visitLeave are invoked. Invocations nested within such an invocation pair indicate the hierarchy. In any case, the invocation pairs are nested correctly. The path argument to the methods of this interface contain the path from the root to the current location, this path corresponds to the invocations of visitEnter-methods which have not yet been closed by invocations of visitLeave.

Author:

Ole Kniemeyer

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.Object	STOP Return value for visitEnter(de.grogra.graph.Path, boolean) and visitInstanceEnter() to indicate that the hierarchical traversal of the graph must not go more deeply in the hierarchy at the current location.

Method Summary

Methods

Modifier and Type	Method and Description
GraphState	getGraphState() Returns the graph state within which the visitor is operating.
java.lang.Object	visitEnter(Path path, boolean node) Informs this visitor about a node or edge in the graph.
java.lang.Object	visitInstanceEnter() Informs this visitor about the beginning of an instantiation.
boolean	visitInstanceLeave(java.lang.Object o) Informs this visitor that an instantiation has been processed completely.
boolean	visitLeave(java.lang.Object o, Path path, boolean node) Informs this visitor that a node or an edge has been processed completely.

Field Detail

STOP

static final java.lang.Object STOP

Return value for visitEnter(de.grogra.graph.Path, boolean) and visitInstanceEnter() to indicate that the hierarchical traversal of the graph must not go more deeply in the hierarchy at the current location.

Method Detail

getGraphState

GraphState getGraphState()

Returns the graph state within which the visitor is operating.

Returns:

graph state of visitor

visitEnter

java.lang.Object visitEnter(Path path,
                          boolean node)

Informs this visitor about a node or edge in the graph. path contains the path from the root up to and including the node or, in case an edge is visited, the edge and its terminal node. Later on, visitLeave(java.lang.Object, de.grogra.graph.Path, boolean) will be invoked with the returned value of this invocation, path and node as arguments. If this method returns STOP, the corresponding visitLeave-method will be invoked immediately after this method, i.e., the visitor does not dive more deeply in the hierarchy. Otherwise, if a node is visited and there are instantiations associated with or edges connected with it (regardless of their direction), their corresponding visitor methods will be invoked inbetween. Likewise, if an edge is visited, its indicent terminal node will be visited next.

Parameters:

path - current path

node - do we enter a node or an edge?

Returns:

value to pass to visitLeave, may be STOP

visitInstanceEnter

java.lang.Object visitInstanceEnter()

Informs this visitor about the beginning of an instantiation. This method invokation is nested immediately within visitEnter/visitLeave of a node. Later on, visitInstanceLeave(Object) will be invoked with the returned value of this invocation as argument. If this method returns STOP, the visitInstanceLeave-method will be invoked immediately after this method, i.e., the visitor does not dive into the instantiation. Otherwise, the instantiation is performed, starting with an edge.

Returns:

value to pass to visitInstanceLeave, may be STOP

visitInstanceLeave

boolean visitInstanceLeave(java.lang.Object o)

Informs this visitor that an instantiation has been processed completely. The value o is the return value of the corresponding invocation of visitInstanceEnter(). If this invocation returns false, no further instantiations or edges of the current level of hierarchy will be passed to this visitor, i.e., the visitLeave method for the enclosing node will be invoked immediately.

Parameters:

o - returned value of visitInstanceEnter

Returns:

true iff processing of current level shall be continued

visitLeave

boolean visitLeave(java.lang.Object o,
                 Path path,
                 boolean node)

Informs this visitor that a node or an edge has been processed completely. The value o is the return value of the corresponding invocation of visitEnter(de.grogra.graph.Path, boolean). In case of a node and if this invocation returns false, no further edges of the current level of hierarchy will be passed to this visitor, i.e., the visitLeave methods for the enclosing edge and node will be invoked immediately. Likewise, in case of an edge and a return value false, no further instantiations or edges of the current level of hierarchy will be passed to this visitor, i.e., the visitLeave method for the enclosing node will be invoked immediately.

Parameters:

o - returned value of visitEnter

path - current path to node

node - do we leave a node or an edge?

Returns:

true iff processing of current level shall be continued