Abstract class LayoutGraph implements interface GraphLayout, which defines the basis for layout information on graph elements. Class DefaultLayoutGraph, the default implementation for LayoutGraph, presents the main graph class of package y.layout that can be used for all graph layout tasks.

Figure 5.2, “Class hierarchy for class DefaultLayoutGraph” shows the class hierarchy for class DefaultLayoutGraph.

Figure 5.2. Class hierarchy for class DefaultLayoutGraph

The following method from abstract class LayoutGraph returns graph-level layout information:

Rectangle getBoundingBox()

Interface NodeLayout and its default implementation, class DefaultNodeLayout, are used to add the layout information to a node. This information consists of the coordinates for the upper left corner of the node, and its width and height.

Figure 5.3, “NodeLayout” shows the class hierarchy for interface NodeLayout. Note that abstract class NodeRealizer from package y.view also implements this interface to hold a node's layout information.

Figure 5.3. NodeLayout

The following convenience methods defined by abstract class LayoutGraph can be used to control the layout information for nodes:

YPoint getCenter(Node v)
YPoint getLocation(Node v)
double getHeight(Node v)
double getWidth(Node v)

void setCenter(Node v, YPoint position)
void setLocation(Node v, YPoint position)
void setSize(Node v, double w, double h)

Interface EdgeLayout and its default implementation, class DefaultEdgeLayout, are used to add the layout information to an edge. This information consists of the coordinates for both starting point and end point of the edge path, as well as the coordinates for the control points in-between these two.

Figure 5.4, “EdgeLayout” shows the class hierarchy for interface EdgeLayout. Note that abstract class EdgeRealizer from package y.view also implements this interface to hold an edge's layout information.

Figure 5.4. EdgeLayout

The following convenience methods defined by abstract class LayoutGraph can be used to control the layout information for edges. Note that the path list for an edge includes its source port, all control points, and also its target port. The point list, though, holds only the edge's control points.

YList getPathList(Edge edge)
YList getPointList(Edge edge)

YPoint getSourcePointAbs(Edge edge)
YPoint getTargetPointAbs(Edge edge)

void setPath(Edge edge, YList path)
void setPoints(Edge edge, YList points)

void setSourcePointAbs(Edge edge, YPoint point)
void setTargetPointAbs(Edge edge, YPoint point)

The generic mechanism for copying a graph structure as described in the section called “Copying a Graph” can also be used to copy implementations of abstract class LayoutGraph. Instead of a GraphCopyFactory instance, however, other copy factory implementations, which are capable of copying the information associated with the elements of a LayoutGraph, need to be used. Specifically, this means that node layout and edge layout data as well as node labels and edge labels need to be handled properly by such implementations.

Classes LayoutGraphCopyFactory and LayoutGraphCopyFactory.HierarchicGraphCopyFactory are predefined copy factories that handle both layout data as well as labels. The latter class is returned when calling the getGraphCopyFactory method on a DefaultLayoutGraph, the default LayoutGraph implementation. It is a hierarchy-aware graph copy factory that wraps a LayoutGraphCopyFactory instance and in addition to the services provided by its delegate also automatically copies the contents of all GroupingKeys data providers registered with the LayoutGraph.

Example 5.1, “Creating a GraphCopier for a "flat" LayoutGraph” shows how to create a GraphCopier that uses the graph copy factory for "flat" graphs instead of the default hierarchy-aware one.

// 'graph' is of type y.layout.DefaultLayoutGraph.

// Create a new GraphCopier that uses a graph copy factory for "flat" graphs.
GraphCopier gc = new GraphCopier(new LayoutGraphCopyFactory());