/*

 * Copyright 1997-2007 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

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 */

package java.awt.dnd;

import java.util.EventListener;

import java.awt.dnd.DropTargetDragEvent;

import java.awt.dnd.DropTargetDropEvent;

/**

 * The <code>DropTargetListener</code> interface

 * is the callback interface used by the

 * <code>DropTarget</code> class to provide

 * notification of DnD operations that involve

 * the subject <code>DropTarget</code>. Methods of

 * this interface may be implemented to provide

 * "drag under" visual feedback to the user throughout

 * the Drag and Drop operation.

 * <p>

 * Create a listener object by implementing the interface and then register it

 * with a <code>DropTarget</code>. When the drag enters, moves over, or exits

 * the operable part of the drop site for that <code>DropTarget</code>, when

 * the drop action changes, and when the drop occurs, the relevant method in

 * the listener object is invoked, and the <code>DropTargetEvent</code> is

 * passed to it.

 * <p>

 * The operable part of the drop site for the <code>DropTarget</code> is

 * the part of the associated <code>Component</code>'s geometry that is not

 * obscured by an overlapping top-level window or by another

 * <code>Component</code> higher in the Z-order that has an associated active

 * <code>DropTarget</code>.

 * <p>

 * During the drag, the data associated with the current drag operation can be

 * retrieved by calling <code>getTransferable()</code> on

 * <code>DropTargetDragEvent</code> instances passed to the listener's

 * methods.

 * <p>

 * Note that <code>getTransferable()</code> on the

 * <code>DropTargetDragEvent</code> instance should only be called within the

 * respective listener's method and all the necessary data should be retrieved

 * from the returned <code>Transferable</code> before that method returns.

 *

 * @since 1.2

 */

public interface DropTargetListener extends EventListener {

    /**

     * Called while a drag operation is ongoing, when the mouse pointer enters

     * the operable part of the drop site for the <code>DropTarget</code>

     * registered with this listener.

     *

     * @param dtde the <code>DropTargetDragEvent</code>

     */

    void dragEnter(DropTargetDragEvent dtde);

    /**

     * Called when a drag operation is ongoing, while the mouse pointer is still

     * over the operable part of the drop site for the <code>DropTarget</code>

     * registered with this listener.

     *

     * @param dtde the <code>DropTargetDragEvent</code>

     */

    void dragOver(DropTargetDragEvent dtde);

    /**

     * Called if the user has modified

     * the current drop gesture.

     * <P>

     * @param dtde the <code>DropTargetDragEvent</code>

     */

    void dropActionChanged(DropTargetDragEvent dtde);

    /**

     * Called while a drag operation is ongoing, when the mouse pointer has

     * exited the operable part of the drop site for the

     * <code>DropTarget</code> registered with this listener.

     *

     * @param dte the <code>DropTargetEvent</code>

     */

    void dragExit(DropTargetEvent dte);

    /**

     * Called when the drag operation has terminated with a drop on

     * the operable part of the drop site for the <code>DropTarget</code>

     * registered with this listener.

     * <p>

     * This method is responsible for undertaking

     * the transfer of the data associated with the

     * gesture. The <code>DropTargetDropEvent</code>

     * provides a means to obtain a <code>Transferable</code>

     * object that represents the data object(s) to

     * be transfered.<P>

     * From this method, the <code>DropTargetListener</code>

     * shall accept or reject the drop via the

     * acceptDrop(int dropAction) or rejectDrop() methods of the

     * <code>DropTargetDropEvent</code> parameter.

     * <P>

     * Subsequent to acceptDrop(), but not before,

     * <code>DropTargetDropEvent</code>'s getTransferable()

     * method may be invoked, and data transfer may be

     * performed via the returned <code>Transferable</code>'s

     * getTransferData() method.

     * <P>

     * At the completion of a drop, an implementation

     * of this method is required to signal the success/failure

     * of the drop by passing an appropriate

     * <code>boolean</code> to the <code>DropTargetDropEvent</code>'s

     * dropComplete(boolean success) method.

     * <P>

     * Note: The data transfer should be completed before the call  to the

     * <code>DropTargetDropEvent</code>'s dropComplete(boolean success) method.

     * After that, a call to the getTransferData() method of the

     * <code>Transferable</code> returned by

     * <code>DropTargetDropEvent.getTransferable()</code> is guaranteed to

     * succeed only if the data transfer is local; that is, only if

     * <code>DropTargetDropEvent.isLocalTransfer()</code> returns

     * <code>true</code>. Otherwise, the behavior of the call is

     * implementation-dependent.

     * <P>

     * @param dtde the <code>DropTargetDropEvent</code>

     */

    void drop(DropTargetDropEvent dtde);

}