/*******************************************************************************
* Copyright (c) 2000, 2011 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.swt.dnd;
import org.eclipse.swt.internal.ole.win32.*;
import org.eclipse.swt.internal.win32.*;
/**
* Transfer
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.
*
*
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.
* * @see ByteArrayTransfer * @see Drag and Drop snippets * @see SWT Example: DNDExample * @see Sample code and further information */ public abstract class Transfer { private static final int RETRY_LIMIT = 10; /* * Feature in Windows. When another application has control * of the clipboard, the clipboard is locked and it's not * possible to retrieve data until the other application is * finished. To allow other applications to get the * data, use PeekMessage() to enable cross thread * message sends. */ int getData(IDataObject dataObject, FORMATETC pFormatetc, STGMEDIUM pmedium) { if (dataObject.GetData(pFormatetc, pmedium) == COM.S_OK) return COM.S_OK; try {Thread.sleep(50);} catch (Throwable t) {} int result = dataObject.GetData(pFormatetc, pmedium); int retryCount = 0; while (result != COM.S_OK && retryCount++ < RETRY_LIMIT) { MSG msg = new MSG(); OS.PeekMessage(msg, 0, 0, 0, OS.PM_NOREMOVE | OS.PM_NOYIELD); try {Thread.sleep(50);} catch (Throwable t) {} result = dataObject.GetData(pFormatetc, pmedium); } return result; } /** * Returns a list of the platform specific data types that can be converted using * this transfer agent. * *Only the data type fields of the TransferData
objects are filled
* in.
TransferData
data type can be converted
* using this transfer agent, or false otherwise (including if transferData is
* null
).
*
* @param transferData a platform specific description of a data type; only the data
* type fields of the TransferData
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 specific ids of the data types that can be converted using
* this transfer agent.
*
* @return the platform specific ids of the data types that can be converted using
* this transfer agent
*/
abstract protected int[] getTypeIds();
/**
* Returns the platform specific names of the data types that can be converted
* using this transfer agent.
*
* @return the platform specific 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.
*
* On a successful conversion, the transferData.result field will be set as follows:
*If this transfer agent is unable to perform the conversion, the transferData.result * field will be set to a failure value as follows:
*Transfer
subclass.
*
* @param transferData an empty TransferData object; this object will be
* filled in on return with the platform specific representation of the data
*
* @exception org.eclipse.swt.SWTException null
null
then
* null
is returned. The type of Object that is returned is
* dependent on the Transfer
subclass.
*/
abstract protected Object nativeToJava(TransferData transferData);
/**
* Registers a name for a data type and returns the associated unique identifier.
*
* You may register the same type more than once, the same unique identifier * will be returned if the type has been previously registered.
* *Note: On windows, do not 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
* * @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 OS.RegisterClipboardFormat(chFormatName); } /** * Test that the object is of the correct format for this Transfer class. * * @param object a java representation of the data to be converted * * @return true if object is of the correct form for this transfer type * * @since 3.1 */ protected boolean validate(Object object) { return true; } }