bundles/org.eclipse.ui.views/src/org/eclipse/ui/views/navigator/LocalSelectionTransfer.java

/************************************************************************
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 - Initial implementation
************************************************************************/
package org.eclipse.ui.views.navigator;

import org.eclipse.core.runtime.*;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.swt.dnd.ByteArrayTransfer;
import org.eclipse.swt.dnd.TransferData;
import org.eclipse.ui.internal.ViewsPlugin;

/**
 * A LocalSelectionTransfer may be used for drag and drop operations
 * within the same instance of Eclipse.
 * The selection is made available directly for use in the DropTargetListener.
 * dropAccept method. The DropTargetEvent passed to dropAccept does not contain
 * the drop data. The selection may be used for validation purposes so that the
 * drop can be aborted if appropriate.
 *
 * This class is not intended to be subclassed.
 * 
 * @since 2.1
 */
public class LocalSelectionTransfer extends ByteArrayTransfer {

	// First attempt to create a UUID for the type name to make sure that
	// different Eclipse applications use different "types" of
	// <code>LocalSelectionTransfer</code>
	private static final String TYPE_NAME= "local-selection-transfer-format" + (new Long(System.currentTimeMillis())).toString(); //$NON-NLS-1$;
	private static final int TYPEID= registerType(TYPE_NAME);
	
	private static final LocalSelectionTransfer INSTANCE= new LocalSelectionTransfer();
	
	private ISelection selection;
	
	/**
	 * Only the singleton instance of this class may be used. 
	 */
	private LocalSelectionTransfer() {
	}
	/**
	 * Returns the singleton.
	 */
	public static LocalSelectionTransfer getInstance() {
		return INSTANCE;
	}
	/**
	 * Returns the local transfer data.
	 * 
	 * @return the local transfer data
	 */
	public ISelection getSelection() {
		return selection;
	}
	/**
	 * Tests whether native drop data matches this transfer type.
	 * 
	 * @param result result of converting the native drop data to Java
	 * @return true if the native drop data does not match this transfer type.
	 * 	false otherwise.
	 */
	private boolean isInvalidNativeType(Object result) {
		return !(result instanceof byte[]) || !TYPE_NAME.equals(new String((byte[])result));
	}
	/**
	 * Returns the type id used to identify this transfer.
	 * 
	 * @return the type id used to identify this transfer.
	 */
	protected int[] getTypeIds() {
		return new int[] {TYPEID};
	}
	/**
	 * Returns the type name used to identify this transfer.
	 * 
	 * @return the type name used to identify this transfer.
	 */
	protected String[] getTypeNames(){
		return new String[] {TYPE_NAME};
	}	
	/**
	 * Overrides org.eclipse.swt.dnd.ByteArrayTransfer#javaToNative(Object,
	 * TransferData).
	 * Only encode the transfer type name since the selection is read and
	 * written in the same process.
	 * 
	 * @see org.eclipse.swt.dnd.ByteArrayTransfer#javaToNative(Object, TransferData)
	 */
	public void javaToNative(Object object, TransferData transferData) {
		byte[] check= TYPE_NAME.getBytes();
		super.javaToNative(check, transferData);
	}
	/**
	 * Overrides org.eclipse.swt.dnd.ByteArrayTransfer#nativeToJava(TransferData).
	 * Test if the native drop data matches this transfer type.
	 * 
	 * @see org.eclipse.swt.dnd.ByteArrayTransfer#nativeToJava(TransferData)
	 */
	public Object nativeToJava(TransferData transferData) {
		Object result= super.nativeToJava(transferData);
		if (isInvalidNativeType(result)) {
			ILog log = ViewsPlugin.getDefault().getLog();
			log.log(
				new Status(
					IStatus.ERROR, 
					ViewsPlugin.PLUGIN_ID, 
					IStatus.ERROR, 
					ResourceNavigatorMessages.getString("LocalSelectionTransfer.errorMessage"), null));	//$NON-NLS-1$
		}
		return selection;
	}
	/**
	 * Sets the transfer data for local use.
	 * 
	 * @param s the transfer data
	 */	
	public void setSelection(ISelection s) {
		selection = s;
	}
}