/******************************************************************************* * 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.ole.win32.COM;import org.eclipse.swt.internal.win32.TCHAR;/** * <code>Transfer</code> provides a mechanism for converting between a java  * representation of data and a platform specific representation of data and  * vice versa.  It is used in data transfer operations such as drag and drop and  * clipboard copy/paste. * * <p>You should only need to become familiar with this class if you are  * implementing a Transfer subclass and you are unable to subclass the  * ByteArrayTransfer class.</p> *  * @see ByteArrayTransfer */public abstract class Transfer {	/** * Returns a list of the platform specific data types that can be converted using  * this transfer agent. * * <p>Only the data type fields of the <code>TransferData</code> objects are filled  * in.</p> * * @return a list of the data types that can be converted using this transfer agent */abstract public TransferData[] getSupportedTypes();/** * Returns true if the <code>TransferData</code> data type can be converted  * using this transfer agent. * * @param transferData a platform specific description of a data type; only the data *  type fields of the <code>TransferData</code> object need to be filled in * * @return true if the transferData data type can be converted using this transfer  * agent */abstract public boolean isSupportedType(TransferData transferData);/** * Returns the platform specfic ids of the  data types that can be converted using  * this transfer agent. *  * @return the platform specfic ids of the data types that can be converted using  * this transfer agent */abstract protected int[] getTypeIds();/** * Returns the platform specfic names of the  data types that can be converted  * using this transfer agent. *  * @return the platform specfic names of the data types that can be converted  * using this transfer agent. */abstract protected String[] getTypeNames();/** * Converts a java representation of data to a platform specific representation of  * the data.  * * <p>On a successful conversion, the transferData.result field will be set as follows: * <ul> * <li>Windows: COM.S_OK * <li>Motif: 1 * <li>GTK: 1 * <li>Photon: 1 * </ul></p> *  * <p>If this transfer agent is unable to perform the conversion, the transferData.result  * field will be set to a failure value as follows: * <ul> * <li>Windows: COM.DV_E_TYMED or COM.E_FAIL * <li>Motif: 0 * <li>GTK: 0 * <li>Photon: 0 * </ul></p> * * @param object a java representation of the data to be converted; the type of * Object that is passed in is dependant on the <code>Transfer</code> subclass. * * @param transferData an empty TransferData object; this object will be  * filled in on return with the platform specific representation of the data */abstract protected void javaToNative (Object object, TransferData transferData);/** * Converts a platform specific representation of data to a java representation. *  * @param transferData the platform specific representation of the data to be  * converted * * @return a java representation of the converted data if the conversion was  * successful; otherwise null.  The type of Object that is returned is dependant  * on the <code>Transfer</code> subclass */abstract protected Object nativeToJava(TransferData transferData);/** * Registers a name for a data type and returns the associated unique identifier. * * <p>You may register the same type more than once, the same unique identifier  * will be returned if the type has been previously registered.</p> * * <p>Note: On windows, do <b>not</b> call this method with pre-defined  * Clipboard Format types such as CF_TEXT or CF_BITMAP because the  * pre-defined identifier will not be returned</p> * * @param formatName the name of a data type * * @return the unique identifier associated with this data type */public static int registerType(String formatName) {	// Look name up in the registry	// If name is not in registry, add it and return assigned value.	// If name already exists in registry, return its assigned value	TCHAR chFormatName = new TCHAR(0, formatName, true);	return COM.RegisterClipboardFormat(chFormatName);}}