/*******************************************************************************
* Copyright (c) 2000, 2007 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.wst.jsdt.internal.ui.dnd;
import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.SafeRunner;
import org.eclipse.jface.util.SafeRunnable;
import org.eclipse.jface.util.TransferDropTargetListener;
import org.eclipse.swt.dnd.DND;
import org.eclipse.swt.dnd.DropTargetEvent;
import org.eclipse.swt.dnd.DropTargetListener;
import org.eclipse.swt.dnd.Transfer;
import org.eclipse.swt.dnd.TransferData;
/**
* A delegating drop adapter negotiates between a set of
* <code>TransferDropTargetListener</code> s On <code>dragEnter</code> the
* adapter determines the listener to be used for any further <code>drag*</code>
* callback.
*/
public class DelegatingDropAdapter implements DropTargetListener {
private TransferDropTargetListener[] fListeners;
private TransferDropTargetListener fCurrentListener;
private int fOriginalDropType;
/**
* Creates a new delegating drop adapter.
*
* @param listeners an array of potential listeners
*/
public DelegatingDropAdapter(TransferDropTargetListener[] listeners) {
Assert.isNotNull(listeners);
fListeners= listeners;
}
/**
* The cursor has entered the drop target boundaries. The current listener
* is updated, and <code>#dragEnter()</code> is forwarded to the current
* listener.
*
* @param event the drop target event
* @see DropTargetListener#dragEnter(DropTargetEvent)
*/
public void dragEnter(DropTargetEvent event) {
fOriginalDropType= event.detail;
updateCurrentListener(event);
}
/**
* The cursor has left the drop target boundaries. The event is forwarded to
* the current listener.
*
* @param event the drop target event
* @see DropTargetListener#dragLeave(DropTargetEvent)
*/
public void dragLeave(final DropTargetEvent event) {
setCurrentListener(null, event);
}
/**
* The operation being performed has changed (usually due to the user
* changing a drag modifier key while dragging). Updates the current
* listener and forwards this event to that listener.
*
* @param event the drop target event
* @see DropTargetListener#dragOperationChanged(DropTargetEvent)
*/
public void dragOperationChanged(final DropTargetEvent event) {
fOriginalDropType= event.detail;
TransferDropTargetListener oldListener= getCurrentListener();
updateCurrentListener(event);
final TransferDropTargetListener newListener= getCurrentListener();
// only notify the current listener if it hasn't changed based on the
// operation change. otherwise the new listener would get a dragEnter
// followed by a dragOperationChanged with the exact same event.
if (newListener != null && newListener == oldListener) {
SafeRunner.run(new SafeRunnable() {
public void run() throws Exception {
newListener.dragOperationChanged(event);
}
});
}
}
/**
* The cursor is moving over the drop target. Updates the current listener
* and forwards this event to that listener. If no listener can handle the
* drag operation the <code>event.detail</code> field is set to
* <code>DND.DROP_NONE</code> to indicate an invalid drop.
*
* @param event the drop target event
* @see DropTargetListener#dragOver(DropTargetEvent)
*/
public void dragOver(final DropTargetEvent event) {
TransferDropTargetListener oldListener= getCurrentListener();
updateCurrentListener(event);
final TransferDropTargetListener newListener= getCurrentListener();
// only notify the current listener if it hasn't changed based on the
// drag over. otherwise the new listener would get a dragEnter
// followed by a dragOver with the exact same event.
if (newListener != null && newListener == oldListener) {
SafeRunner.run(new SafeRunnable() {
public void run() throws Exception {
newListener.dragOver(event);
}
});
}
}
/**
* Forwards this event to the current listener, if there is one. Sets the
* current listener to <code>null</code> afterwards.
*
* @param event the drop target event
* @see DropTargetListener#drop(DropTargetEvent)
*/
public void drop(final DropTargetEvent event) {
updateCurrentListener(event);
if (getCurrentListener() != null) {
SafeRunner.run(new SafeRunnable() {
public void run() throws Exception {
getCurrentListener().drop(event);
}
});
}
setCurrentListener(null, event);
}
/**
* Forwards this event to the current listener if there is one.
*
* @param event the drop target event
* @see DropTargetListener#dropAccept(DropTargetEvent)
*/
public void dropAccept(final DropTargetEvent event) {
if (getCurrentListener() != null) {
SafeRunner.run(new SafeRunnable() {
public void run() throws Exception {
getCurrentListener().dropAccept(event);
}
});
}
}
/**
* Returns the listener which currently handles drop events.
*
* @return the <code>TransferDropTargetListener</code> which currently
* handles drop events.
*/
private TransferDropTargetListener getCurrentListener() {
return fCurrentListener;
}
/**
* Returns the transfer data type supported by the given listener. Returns
* <code>null</code> if the listener does not support any of the specified
* data types.
*
* @param dataTypes available data types
* @param listener <code>TransferDropTargetListener</code> to use for
* testing supported data types.
* @return the transfer data type supported by the given listener or
* <code>null</code>.
*/
private TransferData getSupportedTransferType(TransferData[] dataTypes, TransferDropTargetListener listener) {
for (int i= 0; i < dataTypes.length; i++) {
if (listener.getTransfer().isSupportedType(dataTypes[i])) {
return dataTypes[i];
}
}
return null;
}
/**
* Returns the combined set of <code>Transfer</code> types of all
* <code>TransferDropTargetListeners</code>.
*
* @return the combined set of <code>Transfer</code> types
*/
public Transfer[] getTransfers() {
Transfer[] types= new Transfer[fListeners.length];
for (int i= 0; i < fListeners.length; i++) {
types[i]= fListeners[i].getTransfer();
}
return types;
}
/**
* Sets the current listener to <code>listener</code>. Sends the given
* <code>DropTargetEvent</code> if the current listener changes.
*
* @return <code>true</code> if the new listener is different than the
* previous <code>false</code> otherwise
*/
private boolean setCurrentListener(TransferDropTargetListener listener, final DropTargetEvent event) {
if (fCurrentListener == listener)
return false;
if (fCurrentListener != null) {
SafeRunner.run(new SafeRunnable() {
public void run() throws Exception {
fCurrentListener.dragLeave(event);
}
});
}
fCurrentListener= listener;
if (fCurrentListener != null) {
SafeRunner.run(new SafeRunnable() {
public void run() throws Exception {
fCurrentListener.dragEnter(event);
}
});
}
return true;
}
/**
* Updates the current listener to one that can handle the drop. There can
* be many listeners and each listener may be able to handle many
* <code>TransferData</code> types. The first listener found that can
* handle a drop of one of the given <code>TransferData</code> types will
* be selected. If no listener can handle the drag operation the
* <code>event.detail</code> field is set to <code>DND.DROP_NONE</code>
* to indicate an invalid drop.
*
* @param event the drop target event
*/
private void updateCurrentListener(DropTargetEvent event) {
int originalDetail= event.detail;
// Revert the detail to the "original" drop type that the User
// indicated. This is necessary because the previous listener
// may have changed the detail to something other than what the
// user indicated.
event.detail= fOriginalDropType;
for (int i= 0; i < fListeners.length; i++) {
TransferDropTargetListener listener= fListeners[i];
TransferData dataType= getSupportedTransferType(event.dataTypes, listener);
if (dataType != null) {
TransferData originalDataType= event.currentDataType;
// set the data type supported by the drop listener
event.currentDataType= dataType;
if (listener.isEnabled(event)) {
// if the listener stays the same, set its previously
// determined
// event detail
if (!setCurrentListener(listener, event))
event.detail= originalDetail;
return;
} else {
event.currentDataType= originalDataType;
}
}
}
setCurrentListener(null, event);
event.detail= DND.DROP_NONE;
}
}