Create a new Eclipse RCP application "de.vogella.zest.first". Use the "Eclipse RCP with a view" as a template. Add "org.eclipse.zest.core" and "org.eclipse.zest.layouts" as dependencies to your MANIFEST.MF.

Change the coding of "View.java" to the following. This coding creates a simple graph and connects its elements.

				
package de.vogella.zest.first;

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.ui.part.ViewPart;
import org.eclipse.zest.core.widgets.Graph;
import org.eclipse.zest.core.widgets.GraphConnection;
import org.eclipse.zest.core.widgets.GraphNode;
import org.eclipse.zest.core.widgets.ZestStyles;
import org.eclipse.zest.layouts.LayoutStyles;
import org.eclipse.zest.layouts.algorithms.SpringLayoutAlgorithm;
import org.eclipse.zest.layouts.algorithms.TreeLayoutAlgorithm;

public class View extends ViewPart {
	public static final String ID = "de.vogella.zest.first.view";
	private Graph graph;
	private int layout = 1;

	public void createPartControl(Composite parent) {
		// Graph will hold all other objects
		graph = new Graph(parent, SWT.NONE);
		// Now a few nodes
		GraphNode node1 = new GraphNode(graph, SWT.NONE, "Jim");
		GraphNode node2 = new GraphNode(graph, SWT.NONE, "Jack");
		GraphNode node3 = new GraphNode(graph, SWT.NONE, "Joe");
		GraphNode node4 = new GraphNode(graph, SWT.NONE, "Bill");
		// Lets have a directed connection
		new GraphConnection(graph, ZestStyles.CONNECTIONS_DIRECTED, node1,
				node2);
		// Lets have a dotted graph connection
		new GraphConnection(graph, ZestStyles.CONNECTIONS_DOT, node2, node3);
		// Standard connection
		new GraphConnection(graph, SWT.NONE, node3, node1);
		// Change line color and line width
		GraphConnection graphConnection = new GraphConnection(graph, SWT.NONE,
				node1, node4);
		graphConnection.changeLineColor(parent.getDisplay().getSystemColor(
				SWT.COLOR_GREEN));
		// Also set a text
		graphConnection.setText("This is a text");
		graphConnection.setHighlightColor(parent.getDisplay().getSystemColor(
				SWT.COLOR_RED));
		graphConnection.setLineWidth(3);

		graph.setLayoutAlgorithm(new SpringLayoutAlgorithm(
				LayoutStyles.NO_LAYOUT_NODE_RESIZING), true);
		// Selection listener on graphConnect or GraphNode is not supported
		// see https://bugs.eclipse.org/bugs/show_bug.cgi?id=236528
		graph.addSelectionListener(new SelectionAdapter() {
			@Override
			public void widgetSelected(SelectionEvent e) {
				System.out.println(e);
			}

		});
	}

	public void setLayoutManager() {
		switch (layout) {
		case 1:
			graph.setLayoutAlgorithm(new TreeLayoutAlgorithm(
					LayoutStyles.NO_LAYOUT_NODE_RESIZING), true);
			layout++;
			break;
		case 2:
			graph.setLayoutAlgorithm(new SpringLayoutAlgorithm(
					LayoutStyles.NO_LAYOUT_NODE_RESIZING), true);
			layout = 1;
			break;

		}

	}

	/**
	 * Passing the focus request to the viewer's control.
	 */
	public void setFocus() {
	}
}

			

Run you application and you should see the graph.

Create a command with the following default handler "de.vogella.zest.first.handler.ChangeLayout" which will change the layout for the graph. Assign the command to the menu.

				
package de.vogella.zest.first.handler;

import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.ui.IViewPart;
import org.eclipse.ui.handlers.HandlerUtil;

import de.vogella.zest.first.View;

public class ChangeLayout extends AbstractHandler {

	@Override
	public Object execute(ExecutionEvent event) throws ExecutionException {
		IViewPart findView = HandlerUtil.getActiveWorkbenchWindow(event)
				.getActivePage().findView("de.vogella.zest.first.view");
		View view = (View) findView;
		view.setLayoutManager();
		return null;
	}

}

			

Run your application, if you select your command the layout of your view should change.