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/*******************************************************************************
* Copyright (c) 2000, 2012 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.cdt.internal.ui.dnd;
import java.util.ArrayList;
import java.util.List;
import org.eclipse.core.runtime.Assert;
import org.eclipse.swt.dnd.DragSource;
import org.eclipse.swt.dnd.DragSourceEvent;
import org.eclipse.swt.dnd.DragSourceListener;
import org.eclipse.swt.dnd.Transfer;
import org.eclipse.swt.dnd.TransferData;
/**
* A delegating drag adapter negotiates between a set of <code>TransferDragSourceListener</code>s
* On <code>dragStart</code> the adapter determines the listener to be used for any further
* <code>drag*</code> callbacks.
*/
public class DelegatingDragAdapter implements DragSourceListener {
private TransferDragSourceListener[] fPossibleListeners;
private List<TransferDragSourceListener> fActiveListeners;
private TransferDragSourceListener fFinishListener;
public DelegatingDragAdapter(TransferDragSourceListener[] listeners) {
setPossibleListeners(listeners);
}
protected void setPossibleListeners(TransferDragSourceListener[] listeners) {
Assert.isNotNull(listeners);
Assert.isTrue(fActiveListeners == null, "Can only set possible listeners before drag operation has started"); //$NON-NLS-1$
fPossibleListeners = listeners;
}
/* non Java-doc
* @see DragSourceListener
*/
@Override
public void dragStart(DragSourceEvent event) {
fFinishListener = null;
boolean saveDoit = event.doit;
Object saveData = event.data;
boolean doIt = false;
List<Transfer> transfers = new ArrayList<Transfer>(fPossibleListeners.length);
fActiveListeners = new ArrayList<TransferDragSourceListener>(fPossibleListeners.length);
for (TransferDragSourceListener listener : fPossibleListeners) {
event.doit = saveDoit;
listener.dragStart(event);
if (event.doit) {
transfers.add(listener.getTransfer());
fActiveListeners.add(listener);
}
doIt = doIt || event.doit;
}
if (doIt) {
((DragSource) event.widget).setTransfer(transfers.toArray(new Transfer[transfers.size()]));
}
event.data = saveData;
event.doit = doIt;
}
/* non Java-doc
* @see DragSourceListener
*/
@Override
public void dragSetData(DragSourceEvent event) {
fFinishListener = getListener(event.dataType);
if (fFinishListener != null) {
fFinishListener.dragSetData(event);
}
}
/* non Java-doc
* @see DragSourceListener
*/
@Override
public void dragFinished(DragSourceEvent event) {
try {
if (fFinishListener != null) {
fFinishListener.dragFinished(event);
} else {
// If the user presses Escape then we get a dragFinished without
// getting a dragSetData before.
fFinishListener = getListener(event.dataType);
if (fFinishListener != null) {
fFinishListener.dragFinished(event);
}
}
} finally {
fFinishListener = null;
fActiveListeners = null;
}
}
private TransferDragSourceListener getListener(TransferData type) {
if (type == null)
return null;
for (TransferDragSourceListener listener : fActiveListeners) {
if (listener.getTransfer().isSupportedType(type))
return listener;
}
return null;
}
}
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