--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dwtx/draw2d/graph/GraphUtilities.d	Sun Aug 03 00:52:14 2008 +0200
@@ -0,0 +1,158 @@
+/*******************************************************************************
+ * 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.GraphUtilities;
+
+import dwt.dwthelper.utils;
+import dwtx.draw2d.graph.Subgraph;
+import dwtx.draw2d.graph.Node;
+import dwtx.draw2d.graph.NodeList;
+import dwtx.draw2d.graph.DirectedGraph;
+import dwtx.draw2d.graph.Rank;
+import dwtx.draw2d.graph.Edge;
+import dwtx.draw2d.graph.EdgeList;
+
+/**
+ * Some utility methods for graphs.
+ * @author Eric Bordeau
+ * @since 2.1.2
+ */
+class GraphUtilities {
+
+static Subgraph getCommonAncestor(Node left, Node right) {
+    Subgraph parent;
+    if (auto p = cast(Subgraph)right )
+        parent = p;
+    else
+        parent = right.getParent();
+    while (parent !is null) {
+        if (parent.isNested(left))
+            return parent;
+        parent = parent.getParent();
+    }
+    return null;
+}
+
+/**
+ * Returns <code>true</code> if the given graph contains at least one cycle.
+ * @param graph the graph to test
+ * @return whether the graph is cyclic
+ */
+public static bool isCyclic(DirectedGraph graph) {
+    return isCyclic(new NodeList(graph.nodes));
+}
+
+/**
+ * Recursively removes leaf nodes from the list until there are no nodes remaining (acyclic)
+ * or there are no leaf nodes but the list is not empty (cyclic), then returns the result.
+ * @param nodes the list of nodes to test
+ * @return whether the graph is cyclic
+ */
+public static bool isCyclic(NodeList nodes) {
+    if (nodes.isEmpty())
+        return false;
+    int size = nodes.size();
+    // remove all the leaf nodes from the graph
+    for (int i = 0; i < nodes.size(); i++) {
+        Node node = nodes.getNode(i);
+        if (node.outgoing is null || node.outgoing.isEmpty()) { // this is a leaf node
+            nodes.remove(node);
+            for (int j = 0; j < node.incoming.size(); j++) {
+                Edge e = node.incoming.getEdge(j);
+                e.source.outgoing.remove(e);
+            }
+        }
+    }
+    //  if no nodes were removed, that means there are no leaf nodes and the graph is cyclic
+    if (nodes.size() is size)
+        return true;
+    // leaf nodes were removed, so recursively call this method with the new list
+    return isCyclic(nodes);
+}
+
+/**
+ * Counts the number of edge crossings in a DirectedGraph
+ * @param graph the graph whose crossed edges are counted
+ * @return the number of edge crossings in the graph
+ */
+public static int numberOfCrossingsInGraph(DirectedGraph graph) {
+    int crossings = 0;
+    for (int i = 0; i < graph.ranks.size(); i++) {
+        Rank rank = graph.ranks.getRank(i);
+        crossings += numberOfCrossingsInRank(rank);
+    }
+    return crossings;
+}
+
+/**
+ * Counts the number of edge crossings in a Rank
+ * @param rank the rank whose crossed edges are counted
+ * @return the number of edge crossings in the rank
+ */
+public static int numberOfCrossingsInRank(Rank rank) {
+    int crossings = 0;
+    for (int i = 0; i < rank.size() - 1; i++) {
+        Node currentNode = rank.getNode(i);
+        Node nextNode;
+        for (int j = i + 1; j < rank.size(); j++) {
+            nextNode = rank.getNode(j);
+            EdgeList currentOutgoing = currentNode.outgoing;
+            EdgeList nextOutgoing = nextNode.outgoing;
+            for (int k = 0; k < currentOutgoing.size(); k++) {
+                Edge currentEdge = currentOutgoing.getEdge(k);
+                for (int l = 0; l < nextOutgoing.size(); l++) {
+                    if (nextOutgoing.getEdge(l).getIndexForRank(currentNode.rank + 1)
+                        < currentEdge.getIndexForRank(currentNode.rank + 1))
+                        crossings++;
+                }
+            }
+        }
+    }
+    return crossings;
+}
+
+private static NodeList search(Node node, NodeList list) {
+    if (node.flag)
+        return list;
+    node.flag = true;
+    list.add(node);
+    for (int i = 0; i < node.outgoing.size(); i++)
+        search(node.outgoing.getEdge(i).target, list);
+    return list;
+}
+
+/**
+ * Returns <code>true</code> if adding an edge between the 2 given nodes will introduce a
+ * cycle in the containing graph.
+ * @param source the potential source node
+ * @param target the potential target node
+ * @return whether an edge between the 2 given nodes will introduce a cycle
+ */
+public static bool willCauseCycle(Node source, Node target) {
+    NodeList nodes = search(target, new NodeList());
+    nodes.resetFlags();
+    return nodes.contains(source);
+}
+
+static bool isConstrained(Node left, Node right) {
+    Subgraph common = left.getParent();
+    while (common !is null && !common.isNested(right)) {
+        left = left.getParent();
+        common = left.getParent();
+    }
+    while (right.getParent() !is common)
+        right = right.getParent();
+    return (left.rowOrder !is -1 && right.rowOrder !is -1)
+      && left.rowOrder !is right.rowOrder;
+}
+
+}