--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dwtx/draw2d/graph/SpanningTreeVisitor.d	Sun Aug 03 00:52:14 2008 +0200
@@ -0,0 +1,60 @@
+/*******************************************************************************
+ * Copyright (c) 2003, 2005 IBM Corporation and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     IBM Corporation - initial API and implementation
+ * Port to the D programming language:
+ *     Frank Benoit <benoit@tionex.de>
+ *******************************************************************************/
+module dwtx.draw2d.graph.SpanningTreeVisitor;
+
+import dwt.dwthelper.utils;
+import dwtx.draw2d.graph.GraphVisitor;
+import dwtx.draw2d.graph.Edge;
+import dwtx.draw2d.graph.Node;
+import dwtx.draw2d.graph.EdgeList;
+
+/**
+ * A base class for visitors which operate on the graphs spanning tree used to induce rank
+ * assignments.
+ * @author Randy Hudson
+ * @since 2.1.2
+ */
+abstract class SpanningTreeVisitor : GraphVisitor {
+
+Edge getParentEdge(Node node) {
+    return cast(Edge)node.workingData[1];
+}
+
+EdgeList getSpanningTreeChildren(Node node) {
+    return cast(EdgeList)node.workingData[0];
+}
+
+protected Node getTreeHead(Edge edge) {
+    if (getParentEdge(edge.source) is edge)
+        return edge.target;
+    return edge.source;
+}
+
+Node getTreeParent(Node node) {
+    Edge e = getParentEdge(node);
+    if (e is null)
+        return null;
+    return e.opposite(node);
+}
+
+protected Node getTreeTail(Edge edge) {
+    if (getParentEdge(edge.source) is edge)
+        return edge.source;
+    return edge.target;
+}
+
+void setParentEdge(Node node, Edge edge) {
+    node.workingData[1] = edge;
+}
+
+}