import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.ScrolledComposite;
import org.eclipse.swt.events.TreeEvent;
import org.eclipse.swt.events.TreeListener;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Tree;
import org.eclipse.swt.widgets.TreeItem;

public class Snippet8 implements TreeListener {

	private Composite composite;	

	public static void main(String[] args) {
		new Snippet8();
	}

	public Snippet8() {
		final Display display = new Display();
		final Shell shell = new Shell(display);
		shell.setText("Lazy Tree");
		shell.setLayout(new FillLayout());

		ScrolledComposite control = new ScrolledComposite(shell, SWT.H_SCROLL
				| SWT.V_SCROLL);
		control
				.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true, 1,
						1));
		
		control.setExpandHorizontal(true);
		control.setExpandVertical(true);

		GridLayout gridLayout = new GridLayout();
		gridLayout.numColumns = 1;
		GridData gridData = new GridData();
		gridData.horizontalAlignment = GridData.FILL;
		gridData.grabExcessHorizontalSpace = true;
		gridData.grabExcessVerticalSpace = true;
		gridData.verticalAlignment = GridData.CENTER;
		composite = new Composite(control, SWT.NONE);
		composite.setLayoutData(gridData);
		composite.setLayout(gridLayout);

		//dummy-tree a
		Tree treeA = new Tree(composite, SWT.BORDER);
		treeA.addTreeListener(this);
		for (int i = 1; i < 5; i++) {
			TreeItem root = new TreeItem(treeA, 0);
			root.setText("A" + String.valueOf(i));
			for (int j = 1; j < 5; j++) {
				TreeItem child = new TreeItem(root, 0);
				child.setText("A" + String.valueOf(i) + String.valueOf(j));
			}
		}
		//dummy-tree b
		Tree treeB = new Tree(composite, SWT.BORDER);
		for (int i = 1; i < 5; i++) {
			TreeItem root = new TreeItem(treeB, 0);
			root.setText("B" + String.valueOf(i));
			for (int j = 1; j < 5; j++) {
				TreeItem child = new TreeItem(root, 0);
				child.setText("B" + String.valueOf(i) + String.valueOf(j));
			}
		}

		control.setMinSize(composite.computeSize(SWT.DEFAULT, SWT.DEFAULT));
		control.setContent(composite);

		shell.setSize(500, 500);
		shell.open();
		while (!shell.isDisposed()) {
			if (!display.readAndDispatch())
				display.sleep();
		}
		display.dispose();
	}

	@Override
	public void treeCollapsed(TreeEvent e) {		
		composite.layout();
	}

	@Override
	public void treeExpanded(TreeEvent e) {		
		composite.layout();
	}
}