有向无环图的自动布局算法

//------------------------------------------------------------------------------
void
QNodesEditor::autoLayout()
{
	using namespace ogdf;
	Graph graph;
	// setup graph
	QMap<NodeElement*, QNEBlock*> nodeMap;
	foreach(QGraphicsItem * item, scene->items())
	{
		if (item->type() == QNEBlock::Type)
		{
			NodeElement* node = graph.newNode();
			item->setData(QNEBlock::Type, qVariantFromValue((void*)node));
			nodeMap[node] = (QNEBlock*)item;
		}
	}
	foreach(QGraphicsItem * item, scene->items())
	{
		if (item->type() == QNEConnection::Type)
		{
			QNEConnection* connection = (QNEConnection*)item;
			NodeElement* node1 = (NodeElement*)connection->port1()->block()->data(QNEBlock::Type).value<void*>();
			NodeElement* node2 = (NodeElement*)connection->port2()->block()->data(QNEBlock::Type).value<void*>();
			graph.newEdge(node1, node2);
		}
	}
	// node size
	GraphAttributes graphAttr(graph,
	                          GraphAttributes::nodeGraphics | GraphAttributes::edgeGraphics |
	                          GraphAttributes::nodeLabel | GraphAttributes::nodeColor |
	                          GraphAttributes::edgeColor | GraphAttributes::edgeStyle |
	                          GraphAttributes::nodeStyle | GraphAttributes::nodeTemplate);
	NodeElement* node;
	forall_nodes(node, graph)
	{
		QNEBlock* item = nodeMap[node];
		graphAttr.width(node) = item->getHeight();
		graphAttr.height(node) = item->getWidth();
	}

	// compute layout
	SugiyamaLayout layout;

	FastHierarchyLayout* ohl = new FastHierarchyLayout;
	ohl->layerDistance(30);
	ohl->nodeDistance(25);
	layout.setLayout(ohl);

	layout.call(graphAttr);

	// update node position
	forall_nodes(node, graph)
	{
		double x = graphAttr.x(node);
		double y = graphAttr.y(node);
		QNEBlock* item = nodeMap[node];
		item->setPos(y, x);
	}
}