content: /*******************************************************************************
   * Copyright (c) 2000, 2008 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.typehierarchy;
  
  import org.eclipse.jface.viewers.AbstractTreeViewer;
  import org.eclipse.jface.viewers.ISelection;
  import org.eclipse.swt.dnd.DND;
  import org.eclipse.swt.dnd.DropTargetEvent;
  import org.eclipse.wst.jsdt.core.IJavaScriptElement;
  import org.eclipse.wst.jsdt.internal.ui.packageview.SelectionTransferDropAdapter;
  import org.eclipse.wst.jsdt.internal.ui.util.OpenTypeHierarchyUtil;
  import org.eclipse.wst.jsdt.internal.ui.util.SelectionUtil;
  
  public class TypeHierarchyTransferDropAdapter extends SelectionTransferDropAdapter {
  
  	private static final int OPERATION = DND.DROP_LINK;
  	private TypeHierarchyViewPart fTypeHierarchyViewPart;
  
  	public TypeHierarchyTransferDropAdapter(TypeHierarchyViewPart viewPart, AbstractTreeViewer viewer) {
  		super(viewer);
  		setFullWidthMatchesItem(false);
  		fTypeHierarchyViewPart= viewPart;
  	}
  
  	public void validateDrop(Object target, DropTargetEvent event, int operation) {
  		event.detail= DND.DROP_NONE;
  		initializeSelection();
  		if (target != null){
  			super.validateDrop(target, event, operation);
  			return;
  		}	
  		if (getInputElement(getSelection()) != null) 
  			event.detail= TypeHierarchyTransferDropAdapter.OPERATION;
  	}
  		
  	/* (non-Javadoc)
  	 * @see org.eclipse.wst.jsdt.internal.ui.packageview.SelectionTransferDropAdapter#isEnabled(org.eclipse.swt.dnd.DropTargetEvent)
  	 */
  	public boolean isEnabled(DropTargetEvent event) {
  		return true;
  	}	
  
  	public void drop(Object target, DropTargetEvent event) {
  		if (target != null || event.detail != TypeHierarchyTransferDropAdapter.OPERATION){
  			super.drop(target, event);
  			return;
  		}	
  		IJavaScriptElement input= getInputElement(getSelection());
  		fTypeHierarchyViewPart.setInputElement(input);
  	}
  	
  	private static IJavaScriptElement getInputElement(ISelection selection) {
  		Object single= SelectionUtil.getSingleElement(selection);
  		if (single == null)
  			return null;
  		IJavaScriptElement[] candidates= OpenTypeHierarchyUtil.getCandidates(single);
  		if (candidates != null && candidates.length > 0) 
  			return candidates[0];
  		return null;
  	}
  }
  