/******************************************************************************* * Copyright (c) 2000, 2003 IBM Corporation and others. * All rights reserved. This program and the accompanying materials  * are made available under the terms of the Common Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/cpl-v10.html *  * Contributors: *     IBM Corporation - initial API and implementation *******************************************************************************/package org.eclipse.swt.dnd;import org.eclipse.swt.internal.SWTEventListener;/** * The <code>DropTargetListener</code> class provides event notification to the application  * for DropTarget events. * * <p>As the user moves the cursor into, over and out of a Control that has been designated  * as a DropTarget, events indicate what operation can be performed and what data can be  * transferred if a drop where to occur at that point. * The application can respond to these events and change the type of data that will  * be dropped by modifying event.currentDataType, or change the operation that will be performed  * by modifying the event.detail field or stop any drop from happening on the current target * by setting the event.detail field to DND_DROP_NONE.</p> * * <p>When the user causes a drop to happen by releasing the mouse over a valid drop target,  * the application has one last chance to change the data type of the drop through the  * DropAccept event.  If the drop is still allowed, the DropAccept event is immediately  * followed by the Drop event.  In the Drop event, the application can still change the * operation that is performed but the data type is fixed.</p> *  * @see DropTargetEvent * */public interface DropTargetListener extends SWTEventListener {	/** * The cursor has entered the drop target boundaries. * * <p>The following fields in the DropTargetEvent apply: * <ul> * <li>(in)widget * <li>(in)time * <li>(in)x * <li>(in)y * <li>(in)dataTypes * <li>(in,out)currentDataType * <li>(in)operations * <li>(in,out)detail * <li>(in,out)feedback * </ul></p> * * <p>The <code>operation</code> value is determined by the modifier keys pressed by the user.   * If no keys are pressed the <code>event.detail</code> field is set to DND.DROP_DEFAULT.   * If the application does not set the <code>event.detail</code> to something other  * than <code>DND.DROP_DEFAULT</code> the operation will be set to the platform defined standard  * default.</p> *  * <p>The <code>currentDataType</code> is determined by the first transfer agent specified in  * setTransfer() that matches a data type provided by the drag source.</p> *  * <p>It is possible to get a DragEnter event when the drag source does not provide any matching data. * In this case, the default operation is DND.DROP_NONE and the currentDataType is null.</p> *  * <p>The application can change the operation that will be performed by modifying the  * <code>detail</code> field but the choice must be one of the values in the <code>operations</code>  * field or DND.DROP_NONE.</p> *  * <p>The application can also change the type of data being requested by  * modifying the <code>currentDataTypes</code> field  but the value must be one of the values  * in the <code>dataTypes</code> list.</p> * * @param event  the information associated with the drag enter event *  * @see DropTargetEvent */public void dragEnter(DropTargetEvent event);/** * The cursor has left the drop target boundaries OR the drop has been cancelled OR the data  * is about to be dropped. * * <p>The following fields in the DropTargetEvent apply: * <ul> * <li>(in)widget * <li>(in)time * <li>(in)x * <li>(in)y * <li>(in)dataTypes * <li>(in)currentDataType * <li>(in)operations * <li>(in)detail * </ul></p> * * @param event  the information associated with the drag leave event * * @see DropTargetEvent */public void dragLeave(DropTargetEvent event);/** * The operation being performed has changed (usually due to the user changing the selected modifier key(s) * while dragging). * * <p>The following fields in the DropTargetEvent apply: * <ul> * <li>(in)widget * <li>(in)time * <li>(in)x * <li>(in)y * <li>(in)dataTypes * <li>(in,out)currentDataType * <li>(in)operations * <li>(in,out)detail * <li>(in,out)feedback * </ul></p> * * <p>The <code>operation</code> value is determined by the modifier keys pressed by the user.   * If no keys are pressed the <code>event.detail</code> field is set to DND.DROP_DEFAULT.   * If the application does not set the <code>event.detail</code> to something other than  * <code>DND.DROP_DEFAULT</code> the operation will be set to the platform defined standard default.</p> *  * <p>The <code>currentDataType</code> value is determined by the value assigned to  * <code>currentDataType</code> in previous dragEnter and dragOver calls.</p> *  * <p>The application can change the operation that will be performed by modifying the  * <code>detail</code> field but the choice must be one of the values in the <code>operations</code>  * field.</p> *  * <p>The application can also change the type of data being requested by modifying  * the <code>currentDataTypes</code> field  but the value must be one of the values in the  * <code>dataTypes</code> list.</p> * * @param event  the information associated with the drag operation changed event *  * @see DropTargetEvent */public void dragOperationChanged(DropTargetEvent event);/** * The cursor is moving over the drop target. * * <p>The following fields in the DropTargetEvent apply: * <ul> * <li>(in)widget * <li>(in)time * <li>(in)x * <li>(in)y * <li>(in)dataTypes * <li>(in,out)currentDataType * <li>(in)operations * <li>(in,out)detail * <li>(in,out)feedback * </ul></p> * * <p>The <code>operation</code> value is determined by the value assigned to  * <code>currentDataType</code> in previous dragEnter and dragOver calls.</p> *  * <p>The <code>currentDataType</code> value is determined by the value assigned to  * <code>currentDataType</code> in previous dragEnter and dragOver calls.</p> *  * <p>The application can change the operation that will be performed by modifying the  * <code>detail</code> field but the choice must be one of the values in the <code>operations</code>  * field.</p> *  * <p>The application can also change the type of data being requested by modifying the  * <code>currentDataTypes</code> field  but the value must be one of the values in the  * <code>dataTypes</code> list.</p> *  * <p>NOTE: At this point the <code>data</code> field is null.  On some platforms, it is possible  * to obtain the data being transferred before the transfer occurs but in most platforms this is  * not possible.  On those platforms where the data is available, the application can access the  * data as follows:</p> *  * <pre><code> * public void dragOver(DropTargetEvent event) { *       TextTransfer textTransfer = TextTransfer.getInstance(); *       String data = (String)textTransfer.nativeToJava(event.currentDataType); *       if (data != null) { *           System.out.println("Data to be dropped is (Text)"+data); *       } * }; * </code></pre> * * @param event  the information associated with the drag over event *  * @see DropTargetEvent */public void dragOver(DropTargetEvent event);/** * The data is being dropped.  The data field contains java format of the data being dropped.   * To determine the type of the data object, refer to the documentation for the Transfer subclass  * specified in event.currentDataType. * * <p>The following fields in DropTargetEvent apply: * <ul> * <li>(in)widget * <li>(in)time * <li>(in)x  * <li>(in)y * <li>(in,out)detail * <li>(in)currentDataType * <li>(in)data * </ul></p> * * <p>The application can refuse to perform the drop operation by setting the detail  * field to DND.DROP_NONE.</p> * * @param event the information associated with the drop event *  * @see DropTargetEvent */public void drop(DropTargetEvent event);/** * The drop is about to be performed.   * The drop target is given a last chance to change the nature of the drop. *  * <p>The following fields in the DropTargetEvent apply: * <ul> * <li>(in)widget * <li>(in)time * <li>(in)x * <li>(in)y * <li>(in)dataTypes * <li>(in,out)currentDataType * <li>(in)operations * <li>(in,out)detail * </ul></p> * * <p>The application can veto the drop by setting the <code>event.detail</code> field to  * <code>DND.DROP_NONE</code>.</p> * * <p>The application can change the operation that will be performed by modifying the  * <code>detail</code> field but the choice must be one of the values in the  * <code>operations</code> field.</p> *  * <p>The application can also change the type of data being requested by modifying the  * <code>currentDataTypes</code> field  but the value must be one of the values in the < * code>dataTypes</code> list.</p> * * @param event  the information associated with the drop accept event *  * @see DropTargetEvent */public void dropAccept(DropTargetEvent event);}