jsf/plugins/org.eclipse.jst.pagedesigner/src/org/eclipse/jst/pagedesigner/dnd/internal/PDTemplateTransferDropTargetListener.java

/*******************************************************************************
 * Copyright (c) 2006 Sybase, Inc. 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:
 *     Sybase, Inc. - initial API and implementation
 *******************************************************************************/
package org.eclipse.jst.pagedesigner.dnd.internal;

import org.eclipse.gef.EditPartViewer;
import org.eclipse.gef.Request;
import org.eclipse.gef.dnd.AbstractTransferDropTargetListener;
import org.eclipse.gef.dnd.TemplateTransfer;
import org.eclipse.gef.requests.CreateRequest;
import org.eclipse.jst.pagedesigner.editors.palette.impl.PaletteItemDescriptor;
import org.eclipse.jst.pagedesigner.itemcreation.ItemCreationRequest;
import org.eclipse.swt.dnd.DND;
import org.eclipse.swt.dnd.DropTargetEvent;

/**
 * @author mengbo
 * @version 1.5
 */
public class PDTemplateTransferDropTargetListener extends
		AbstractTransferDropTargetListener {

	/**
	 * @param viewer
	 */
	public PDTemplateTransferDropTargetListener(EditPartViewer viewer) {
		super(viewer, TemplateTransfer.getInstance());
	}

	/**
	 * @see org.eclipse.gef.dnd.AbstractTransferDropTargetListener#createTargetRequest()
	 */
	protected Request createTargetRequest() {
		Request request = new ItemCreationRequest();
		return request;
	}

	/**
	 * A helper method that casts the target Request to a CreateRequest.
	 * 
	 * @return CreateRequest
	 */
	protected final Request getCreateRequest() {
		return getTargetRequest();
	}

	/**
	 * The purpose of a template is to be copied. Therefore, the drop operation
	 * can't be anything but <code>DND.DROP_COPY</code>.
	 * 
	 * @see AbstractTransferDropTargetListener#handleDragOperationChanged()
	 */
	protected void handleDragOperationChanged() {
		getCurrentEvent().detail = DND.DROP_COPY;
		super.handleDragOperationChanged();
	}

	/**
	 * The purpose of a template is to be copied. Therefore, the Drop operation
	 * is set to <code>DND.DROP_COPY</code> by default.
	 * 
	 * @see org.eclipse.gef.dnd.AbstractTransferDropTargetListener#handleDragOver()
	 */
	protected void handleDragOver() {
		getCurrentEvent().detail = DND.DROP_COPY;
		getCurrentEvent().feedback = DND.FEEDBACK_SCROLL | DND.FEEDBACK_EXPAND;
		super.handleDragOver();
	}

	/**
	 * Assumes that the target request is a {@link CreateRequest}.
	 */
	protected void updateTargetRequest() {
		// We should never see request that is not of ItemCreationRequest type,
		// but there is an error case that Eclipse send out other types
		// requests.
		// Add this test to avoid potential error.
		if (getCreateRequest() instanceof ItemCreationRequest) {
			ItemCreationRequest request = (ItemCreationRequest) getCreateRequest();
			PaletteItemDescriptor itemDescriptor = (PaletteItemDescriptor) TemplateTransfer
					.getInstance().getObject();
			request.setItemDescriptor(itemDescriptor);
			request.setLocation(getDropLocation());
		}
	}

	public void drop(DropTargetEvent event) {
		if (getCreateRequest() instanceof ItemCreationRequest) {
			getViewer().getControl().setFocus();
			super.drop(event);
		}
	}

}