content: /*******************************************************************************
   * Copyright (c) 2000, 2007 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
   *******************************************************************************/
  package org.eclipse.wst.jsdt.internal.ui.dnd;
  
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  
  import org.eclipse.core.runtime.Assert;
  import org.eclipse.jface.util.TransferDragSourceListener;
  import org.eclipse.swt.dnd.DragSource;
  import org.eclipse.swt.dnd.DragSourceEvent;
  import org.eclipse.swt.dnd.DragSourceListener;
  import org.eclipse.swt.dnd.Transfer;
  import org.eclipse.swt.dnd.TransferData;
  
  /**
   * A delegating drag adapter negotiates between a set of <code>TransferDragSourceListener</code>s
   * On <code>dragStart</code> the adapter determines the listener to be used for any further
   * <code>drag*</code> callback.
   */
  public class DelegatingDragAdapter implements DragSourceListener {
  
  	private TransferDragSourceListener[] fPossibleListeners;
  	private List fActiveListeners;
  	private TransferDragSourceListener fFinishListener;
  	
  	public DelegatingDragAdapter(TransferDragSourceListener[] listeners) {
  		setPossibleListeners(listeners);
  	}
  	
  	protected void setPossibleListeners(TransferDragSourceListener[] listeners) {
  		Assert.isNotNull(listeners);
  		Assert.isTrue(fActiveListeners == null, "Can only set possible listeners before drag operation has started"); //$NON-NLS-1$
  		fPossibleListeners= listeners;
  	}
  	
  	/* non Java-doc
  	 * @see DragSourceListener
  	 */
  	public void dragStart(DragSourceEvent event) {
  		fFinishListener= null;
  		boolean saveDoit= event.doit;
  		Object saveData= event.data;
  		boolean doIt= false;
  		List transfers= new ArrayList(fPossibleListeners.length);
  		fActiveListeners= new ArrayList(fPossibleListeners.length);
  		
  		for (int i= 0; i < fPossibleListeners.length; i++) {
  			TransferDragSourceListener listener= fPossibleListeners[i];
  			event.doit= saveDoit;
  			listener.dragStart(event);
  			if (event.doit) {
  				transfers.add(listener.getTransfer());
  				fActiveListeners.add(listener);
  			}
  			doIt= doIt || event.doit;
  		}
  		if (doIt) {
  			((DragSource)event.widget).setTransfer((Transfer[])transfers.toArray(new Transfer[transfers.size()]));
  		}
  		event.data= saveData;
  		event.doit= doIt;
  	}
  
  	/* non Java-doc
  	 * @see DragSourceListener
  	 */
  	public void dragSetData(DragSourceEvent event) {
  		fFinishListener= getListener(event.dataType);
  		if (fFinishListener != null)
  			fFinishListener.dragSetData(event);
  	}
  	
  	/* non Java-doc
  	 * @see DragSourceListener
  	 */
  	public void dragFinished(DragSourceEvent event) {
  		try{
  			if (fFinishListener != null) {
  				fFinishListener.dragFinished(event);
  			} else {
  				// If the user presses Escape then we get a dragFinished without
  				// getting a dragSetData before.
  				fFinishListener= getListener(event.dataType);
  				if (fFinishListener != null)
  					fFinishListener.dragFinished(event);
  			}
  		} finally{
  			fFinishListener= null;
  			fActiveListeners= null;
  		}	
  	}
  	
  	private TransferDragSourceListener getListener(TransferData type) {
  		if (type == null)
  			return null;
  			
  		for (Iterator iter= fActiveListeners.iterator(); iter.hasNext();) {
  			TransferDragSourceListener listener= (TransferDragSourceListener)iter.next();
  			if (listener.getTransfer().isSupportedType(type)) {
  				return listener;
  			}
  		}
  		return null;
  	}	
  }
  