package prefuse.action.layout.graph;
import prefuse.action.layout.Layout;
import prefuse.data.Graph;
import prefuse.data.Tree;
import prefuse.data.tuple.TupleSet;
import prefuse.visual.NodeItem;
/**
* Abstract base class providing convenience methods for tree layout algorithms.
*
* @version 1.0
* @author <a href="http://jheer.org">jeffrey heer</a>
*/
public abstract class TreeLayout extends Layout {
protected NodeItem m_root;
/**
* Create a new TreeLayout.
*/
public TreeLayout() {
super();
}
/**
* Create a new TreeLayout.
* @param group the data group to layout. This must resolve to a graph
* instance, otherwise an exception will result when subclasses attempt
* to retrieve the layout root.
*/
public TreeLayout(String group) {
super(group);
}
// ------------------------------------------------------------------------
/**
* Explicitly set the node to use as the layout root.
* @param root the node to use as the root. A null value is legal, and
* indicates that the root of the spanning tree of the backing graph will
* be used as the layout root. If the node is not a member of this layout's
* data group, an exception will be thrown.
* @throws IllegalArgumentException if the provided root is not a member of
* this layout's data group.
*/
public void setLayoutRoot(NodeItem root) {
if ( !root.isInGroup(m_group) )
throw new IllegalArgumentException("Input node is not a member "
+ "of this layout's data group");
m_root = root;
}
/**
* Return the NodeItem to use as the root for this tree layout.
* @return the root node to use for this tree layout.
* @throws IllegalStateException if the action's data group does not
* resolve to a {@link prefuse.data.Graph} instance.
*/
public NodeItem getLayoutRoot() {
if ( m_root != null )
return m_root;
TupleSet ts = m_vis.getGroup(m_group);
if ( ts instanceof Graph ) {
Tree tree = ((Graph)ts).getSpanningTree();
return (NodeItem)tree.getRoot();
} else {
throw new IllegalStateException("This action's data group does" +
"not resolve to a Graph instance.");
}
}
} // end of abstract class TreeLayout