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/*******************************************************************************
 * Copyright (c) 2000, 2015 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.util;

import org.eclipse.swt.dnd.DropTargetEvent;
import org.eclipse.swt.dnd.DropTargetListener;
import org.eclipse.swt.dnd.Transfer;

/**
 * A TransferDropTargetListener is a DropTragetListener
 * that handles one type of SWT {@link Transfer}.
 * The purpose of a TransferDropTargetListener is to:
 * 
 *   Determine enablement for a drop operation. A TransferDropTargetListener
 * 		will not be used if isEnabled returns false.
 *   
When enabled, optionally show feedback on the DropTarget.
 *   
Perform the actual drop
 * 
 * A DelegatingDropAdapter allows these functions to be implemented
 * separately for unrelated types of drags. DelegatingDropAdapter then
 * combines the function of each TransferDropTargetListener, while
 * allowing them to be implemented as if they were the only DragSourceListener.
 * @since 3.0
 */
public interface TransferDropTargetListener extends DropTargetListener {
	/**
	 * Returns the Transfer type that this listener can
	 * accept a drop operation for.
	 *
	 * @return the Transfer for this listener
	 */
	Transfer getTransfer();

	/**
	 * Returns true if this listener can handle the drop
	 * based on the given DropTargetEvent.
	 * 
	 * This method is called by the DelegatingDropAdapter only
	 * if the DropTargetEvent contains a transfer data type
	 * supported by this listener. The Transfer returned by the
	 * #getTransfer() method is used for this purpose.
	 * 
	 *
	 * @param event the drop target event
	 * @return true if the listener is enabled for the given
	 * 	drop target event.
	 */
	boolean isEnabled(DropTargetEvent event);
}