# HG changeset patch
# User Frank Benoit <benoit@tionex.de>
# Date 1207243211 -7200
# Node ID 913f0fd3b3475351691d44e87a5cbb5f73e60d77
# Parent  f12d40e7da8ffba9327d17c23a77b0ff1f51a6af
util dnd

diff -r f12d40e7da8f -r 913f0fd3b347 dwtx/jface/util/DelegatingDragAdapter.d
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dwtx/jface/util/DelegatingDragAdapter.d	Thu Apr 03 19:20:11 2008 +0200
@@ -0,0 +1,290 @@
+/*******************************************************************************
+ * Copyright (c) 2000, 2006 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
+ * Port to the D programming language:
+ *     Frank Benoit <benoit@tionex.de>
+ *******************************************************************************/
+module dwtx.jface.util.DelegatingDragAdapter;
+
+import dwtx.jface.util.TransferDragSourceListener;
+import dwtx.jface.util.SafeRunnable;
+
+import tango.util.collection.ArraySeq;
+
+import dwt.dnd.DragSource;
+import dwt.dnd.DragSourceEvent;
+import dwt.dnd.DragSourceListener;
+import dwt.dnd.Transfer;
+import dwt.dnd.TransferData;
+
+import dwt.dwthelper.utils;
+
+/**
+ * A <code>DelegatingDragAdapter</code> is a <code>DragSourceListener</code> that
+ * maintains and delegates to a set of {@link TransferDragSourceListener}s. Each
+ * TransferDragSourceListener can then be implemented as if it were the
+ * <code>DragSource's</code> only DragSourceListener.
+ * <p>
+ * When a drag is started, a subset of all <code>TransferDragSourceListeners</code>
+ * is generated and stored in a list of <i>active</i> listeners. This subset is
+ * calculated by forwarding {@link DragSourceListener#dragStart(DragSourceEvent)} to
+ * every listener, and checking if the {@link DragSourceEvent#doit doit} field is left
+ * set to <code>true</code>.
+ * </p>
+ * The <code>DragSource</code>'s set of supported Transfer types ({@link
+ * DragSource#setTransfer(Transfer[])}) is updated to reflect the Transfer types
+ * corresponding to the active listener subset.
+ * <p>
+ * If and when {@link #dragSetData(DragSourceEvent)} is called, a single
+ * <code>TransferDragSourceListener</code> is chosen, and only it is allowed to set the
+ * drag data. The chosen listener is the first listener in the subset of active listeners
+ * whose Transfer supports ({@link Transfer#isSupportedType(TransferData)}) the
+ * <code>dataType</code> in the <code>DragSourceEvent</code>.
+ * </p>
+ * <p>
+ * The following example snippet shows a <code>DelegatingDragAdapter</code> with two
+ * <code>TransferDragSourceListeners</code>. One implements drag of text strings,
+ * the other supports file transfer and demonstrates how a listener can be disabled using
+ * the dragStart method.
+ * </p>
+ * <code><pre>
+ *      final TreeViewer viewer = new TreeViewer(shell, DWT.NONE);
+ *
+ *      DelegatingDragAdapter dragAdapter = new DelegatingDragAdapter();
+ *      dragAdapter.addDragSourceListener(new TransferDragSourceListener() {
+ *          public Transfer getTransfer() {
+ *              return TextTransfer.getInstance();
+ *          }
+ *          public void dragStart(DragSourceEvent event) {
+ *              // always enabled, can control enablement based on selection etc.
+ *          }
+ *          public void dragSetData(DragSourceEvent event) {
+ *              event.data = "Transfer data";
+ *          }
+ *          public void dragFinished(DragSourceEvent event) {
+ *              // no clean-up required
+ *          }
+ *      });
+ *      dragAdapter.addDragSourceListener(new TransferDragSourceListener() {
+ *          public Transfer getTransfer() {
+ *              return FileTransfer.getInstance();
+ *          }
+ *          public void dragStart(DragSourceEvent event) {
+ *              // enable drag listener if there is a viewer selection
+ *              event.doit = !viewer.getSelection().isEmpty();
+ *          }
+ *          public void dragSetData(DragSourceEvent event) {
+ *              File file1 = new File("C:/temp/file1");
+ *              File file2 = new File("C:/temp/file2");
+ *              event.data = new String[] {file1.getAbsolutePath(), file2.getAbsolutePath()};
+ *          }
+ *          public void dragFinished(DragSourceEvent event) {
+ *              // no clean-up required
+ *          }
+ *      });
+ *      viewer.addDragSupport(DND.DROP_COPY | DND.DROP_MOVE, dragAdapter.getTransfers(), dragAdapter);
+ * </pre></code>
+ * @since 3.0
+ */
+public class DelegatingDragAdapter : DragSourceListener {
+    private ArraySeq!(Object) listeners;
+
+    private ArraySeq!(Object) activeListeners;
+
+    private TransferDragSourceListener currentListener;
+
+    this(){
+        listeners = new ArraySeq!(Object);
+        activeListeners = new ArraySeq!(Object);
+    }
+
+    /**
+     * Adds the given <code>TransferDragSourceListener</code>.
+     *
+     * @param listener the new listener
+     */
+    public void addDragSourceListener(TransferDragSourceListener listener) {
+        listeners.append(cast(Object)listener);
+    }
+
+    /**
+     * The drop has successfully completed. This event is forwarded to the current
+     * drag listener.
+     * Doesn't update the current listener, since the current listener  is already the one
+     * that completed the drag operation.
+     *
+     * @param event the drag source event
+     * @see DragSourceListener#dragFinished(DragSourceEvent)
+     */
+    public void dragFinished(DragSourceEvent event) {
+        //      if (Policy.DEBUG_DRAG_DROP)
+        //          System.out.println("Drag Finished: " + toString()); //$NON-NLS-1$
+        SafeRunnable.run(new class SafeRunnable {
+            DragSourceEvent event_;
+            this(){
+                event_=event;
+            }
+            public void run() {
+                if (currentListener !is null) {
+                    // there is a listener that can handle the drop, delegate the event
+                    currentListener.dragFinished(event_);
+                } else {
+                    // The drag was canceled and currentListener was never set, so send the
+                    // dragFinished event to all the active listeners.
+                    foreach( e; activeListeners ){
+                        (cast(TransferDragSourceListener) e)
+                                .dragFinished(event);
+                    }
+                }
+            }
+        });
+        currentListener = null;
+        activeListeners.clear();
+    }
+
+    /**
+     * The drop data is requested.
+     * Updates the current listener and then forwards the event to it.
+     *
+     * @param event the drag source event
+     * @see DragSourceListener#dragSetData(DragSourceEvent)
+     */
+    public void dragSetData(DragSourceEvent event) {
+        //      if (Policy.DEBUG_DRAG_DROP)
+        //          System.out.println("Drag Set Data: " + toString()); //$NON-NLS-1$
+
+        updateCurrentListener(event); // find a listener that can provide the given data type
+        if (currentListener !is null) {
+            SafeRunnable.run(new class SafeRunnable {
+                DragSourceEvent event_;
+                this(){
+                    event_=event;
+                }
+                public void run() {
+                    currentListener.dragSetData(event_);
+                }
+            });
+        }
+    }
+
+    /**
+     * A drag operation has started.
+     * Forwards this event to each listener. A listener must set <code>event.doit</code>
+     * to <code>false</code> if it cannot handle the drag operation. If a listener can
+     * handle the drag, it is added to the list of active listeners.
+     * The drag is aborted if there are no listeners that can handle it.
+     *
+     * @param event the drag source event
+     * @see DragSourceListener#dragStart(DragSourceEvent)
+     */
+    public void dragStart(DragSourceEvent event) {
+        //      if (Policy.DEBUG_DRAG_DROP)
+        //          System.out.println("Drag Start: " + toString()); //$NON-NLS-1$
+        bool doit = false; // true if any one of the listeners can handle the drag
+        auto transfers = new ArraySeq!(Object);
+        transfers.capacity(listeners.size());
+
+        activeListeners.clear();
+        for (int i = 0; i < listeners.size(); i++) {
+            TransferDragSourceListener listener = cast(TransferDragSourceListener) listeners
+                    .get(i);
+            event.doit = true; // restore event.doit
+            SafeRunnable.run(new class SafeRunnable {
+                TransferDragSourceListener listener_;
+                DragSourceEvent event_;
+                this(){
+                    event_=event;
+                    listener_=listener;
+                }
+                public void run() {
+                    listener_.dragStart(event_);
+                }
+            });
+            if (event.doit) { // the listener can handle this drag
+                transfers.append(listener.getTransfer());
+                activeListeners.append(cast(Object)listener);
+            }
+            doit |= event.doit;
+        }
+
+        if (doit) {
+            (cast(DragSource) event.widget).setTransfer(arraycast!(Transfer)( transfers
+                    .toArray()));
+        }
+
+        event.doit = doit;
+    }
+
+    /**
+     * Returns the <code>Transfer<code>s from every <code>TransferDragSourceListener</code>.
+     *
+     * @return the combined <code>Transfer</code>s
+     */
+    public Transfer[] getTransfers() {
+        Transfer[] types = new Transfer[listeners.size()];
+        for (int i = 0; i < listeners.size(); i++) {
+            TransferDragSourceListener listener = cast(TransferDragSourceListener) listeners
+                    .get(i);
+            types[i] = listener.getTransfer();
+        }
+        return types;
+    }
+
+    /**
+     * Returns <code>true</code> if there are no listeners to delegate drag events to.
+     *
+     * @return <code>true</code> if there are no <code>TransferDragSourceListeners</code>
+     *  <code>false</code> otherwise.
+     */
+    public bool isEmpty() {
+        return listeners.drained();
+    }
+
+    /**
+     * Removes the given <code>TransferDragSourceListener</code>.
+     * Listeners should not be removed while a drag and drop operation is in progress.
+     *
+     * @param listener the <code>TransferDragSourceListener</code> to remove
+     */
+    public void removeDragSourceListener(TransferDragSourceListener listener) {
+        listeners.remove(cast(Object)listener);
+        if (currentListener is listener) {
+            currentListener = null;
+        }
+        if (activeListeners.contains(cast(Object)listener)) {
+            activeListeners.remove(cast(Object)listener);
+        }
+    }
+
+    /**
+     * Updates the current listener to one that can handle the drag. There can
+     * be many listeners and each listener may be able to handle many <code>TransferData</code>
+     * types.  The first listener found that supports one of the <code>TransferData</ode>
+     * types specified in the <code>DragSourceEvent</code> will be selected.
+     *
+     * @param event the drag source event
+     */
+    private void updateCurrentListener(DragSourceEvent event) {
+        currentListener = null;
+        if (event.dataType is null) {
+            return;
+        }
+        foreach( e; activeListeners ){
+            TransferDragSourceListener listener = cast(TransferDragSourceListener)e;
+
+            if (listener.getTransfer().isSupportedType(event.dataType)) {
+                //              if (Policy.DEBUG_DRAG_DROP)
+                //                  System.out.println("Current drag listener: " + listener); //$NON-NLS-1$
+                currentListener = listener;
+                return;
+            }
+        }
+    }
+
+}
diff -r f12d40e7da8f -r 913f0fd3b347 dwtx/jface/util/DelegatingDropAdapter.d
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dwtx/jface/util/DelegatingDropAdapter.d	Thu Apr 03 19:20:11 2008 +0200
@@ -0,0 +1,411 @@
+/*******************************************************************************
+ * 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
+ * Port to the D programming language:
+ *     Frank Benoit <benoit@tionex.de>
+ *******************************************************************************/
+module dwtx.jface.util.DelegatingDropAdapter;
+
+import dwtx.jface.util.TransferDropTargetListener;
+import dwtx.jface.util.SafeRunnable;
+
+import tango.util.collection.ArraySeq;
+
+import dwt.dnd.DND;
+import dwt.dnd.DropTargetEvent;
+import dwt.dnd.DropTargetListener;
+import dwt.dnd.Transfer;
+import dwt.dnd.TransferData;
+
+import dwt.dwthelper.utils;
+
+/**
+ * A <code>DelegatingDropAdapter</code> is a <code>DropTargetListener</code> that
+ * maintains and delegates to a set of {@link TransferDropTargetListener}s. Each
+ * <code>TransferDropTargetListener</code> can then be implemented as if it were
+ * the DropTarget's only <code>DropTargetListener</code>.
+ * <p>
+ * On <code>dragEnter</code>, <code>dragOperationChanged</code>, <code>dragOver</code>
+ * and <code>drop</code>, a <i>current</i> listener is obtained from the set of all
+ * <code>TransferDropTargetListeners</code>. The current listener is the first listener
+ * to return <code>true</code> for
+ * {@link TransferDropTargetListener#isEnabled(DropTargetEvent)}.
+ * The current listener is forwarded all <code>DropTargetEvents</code> until some other
+ * listener becomes the current listener, or the drop terminates.
+ * </p>
+ * <p>
+ * After adding all <code>TransferDropTargetListeners</code> to the
+ * <code>DelegatingDropAdapter</code> the combined set of <code>Transfers</code> should
+ * be set in the DWT <code>DropTarget</code>. <code>#getTransfers()</code> provides the
+ * set of <code>Transfer</code> types of all <code>TransferDropTargetListeners</code>.
+ * </p>
+ * <p>
+ * The following example snippet shows a <code>DelegatingDropAdapter</code> with two
+ * <code>TransferDropTargetListeners</code>. One supports dropping resources and
+ * demonstrates how a listener can be disabled in the isEnabled method.
+ * The other listener supports text transfer.
+ * </p>
+ * <code><pre>
+ *      final TreeViewer viewer = new TreeViewer(shell, DWT.NONE);
+ *      DelegatingDropAdapter dropAdapter = new DelegatingDropAdapter();
+ *      dropAdapter.addDropTargetListener(new TransferDropTargetListener() {
+ *          public Transfer getTransfer() {
+ *              return ResourceTransfer.getInstance();
+ *          }
+ *          public bool isEnabled(DropTargetEvent event) {
+ *              // disable drop listener if there is no viewer selection
+ *              if (viewer.getSelection().isEmpty())
+ *                  return false;
+ *              return true;
+ *          }
+ *          public void dragEnter(DropTargetEvent event) {}
+ *          public void dragLeave(DropTargetEvent event) {}
+ *          public void dragOperationChanged(DropTargetEvent event) {}
+ *          public void dragOver(DropTargetEvent event) {}
+ *          public void drop(DropTargetEvent event) {
+ *              if (event.data is null)
+ *                  return;
+ *              IResource[] resources = (IResource[]) event.data;
+ *              if (event.detail is DND.DROP_COPY) {
+ *                  // copy resources
+ *              } else {
+ *                  // move resources
+ *              }
+ *
+ *          }
+ *          public void dropAccept(DropTargetEvent event) {}
+ *      });
+ *      dropAdapter.addDropTargetListener(new TransferDropTargetListener() {
+ *          public Transfer getTransfer() {
+ *              return TextTransfer.getInstance();
+ *          }
+ *          public bool isEnabled(DropTargetEvent event) {
+ *              return true;
+ *          }
+ *          public void dragEnter(DropTargetEvent event) {}
+ *          public void dragLeave(DropTargetEvent event) {}
+ *          public void dragOperationChanged(DropTargetEvent event) {}
+ *          public void dragOver(DropTargetEvent event) {}
+ *          public void drop(DropTargetEvent event) {
+ *              if (event.data is null)
+ *                  return;
+ *              System.out.println(event.data);
+ *          }
+ *          public void dropAccept(DropTargetEvent event) {}
+ *      });
+ *      viewer.addDropSupport(DND.DROP_COPY | DND.DROP_MOVE, dropAdapter.getTransfers(), dropAdapter);
+ * </pre></code>
+ * @since 3.0
+ */
+public class DelegatingDropAdapter : DropTargetListener {
+    private ArraySeq!(Object) listeners;
+
+    private TransferDropTargetListener currentListener;
+
+    private int originalDropType;
+
+    this(){
+        listeners = new ArraySeq!(Object);
+    }
+
+    /**
+     * Adds the given <code>TransferDropTargetListener</code>.
+     *
+     * @param listener the new listener
+     */
+    public void addDropTargetListener(TransferDropTargetListener listener) {
+        listeners.append(cast(Object)listener);
+    }
+
+    /**
+     * 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) {
+        //      if (Policy.DEBUG_DRAG_DROP)
+        //          System.out.println("Drag Enter: " + toString()); //$NON-NLS-1$
+        originalDropType = 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(DropTargetEvent event) {
+        //      if (Policy.DEBUG_DRAG_DROP)
+        //          System.out.println("Drag Leave: " + toString()); //$NON-NLS-1$
+        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(DropTargetEvent event) {
+        //      if (Policy.DEBUG_DRAG_DROP)
+        //          System.out.println("Drag Operation Changed to: " + event.detail); //$NON-NLS-1$
+        originalDropType = event.detail;
+        TransferDropTargetListener oldListener = getCurrentListener();
+        updateCurrentListener(event);
+        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 !is null && newListener is oldListener) {
+            SafeRunnable.run(new class SafeRunnable {
+                DropTargetEvent event_;
+                TransferDropTargetListener newListener_;
+                this(){
+                    event_=event;
+                    newListener_=newListener;
+                }
+                public void run() {
+                    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(DropTargetEvent event) {
+        TransferDropTargetListener oldListener = getCurrentListener();
+        updateCurrentListener(event);
+        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 !is null && newListener is oldListener) {
+            SafeRunnable.run(new class SafeRunnable {
+                DropTargetEvent event_;
+                TransferDropTargetListener newListener_;
+                this(){
+                    event_=event;
+                    newListener_=newListener;
+                }
+                public void run() {
+                    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(DropTargetEvent event) {
+        //      if (Policy.DEBUG_DRAG_DROP)
+        //          System.out.println("Drop: " + toString()); //$NON-NLS-1$
+        updateCurrentListener(event);
+        if (getCurrentListener() !is null) {
+            SafeRunnable.run(new class SafeRunnable {
+                DropTargetEvent event_;
+                this(){ event_=event;}
+                public void run() {
+                    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(DropTargetEvent event) {
+        //      if (Policy.DEBUG_DRAG_DROP)
+        //          System.out.println("Drop Accept: " + toString()); //$NON-NLS-1$
+        if (getCurrentListener() !is null) {
+            SafeRunnable.run(new class SafeRunnable {
+                DropTargetEvent event_;
+                this(){ event_=event;}
+                public void run() {
+                    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 currentListener;
+    }
+
+    /**
+     * 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[listeners.size()];
+        for (int i = 0; i < listeners.size(); i++) {
+            TransferDropTargetListener listener = cast(TransferDropTargetListener) listeners
+                    .get(i);
+            types[i] = listener.getTransfer();
+        }
+        return types;
+    }
+
+    /**
+     * Returns <code>true</code> if there are no listeners to delegate events to.
+     *
+     * @return <code>true</code> if there are no <code>TransferDropTargetListeners</code>
+     *  <code>false</code> otherwise
+     */
+    public bool isEmpty() {
+        return listeners.drained();
+    }
+
+    /**
+     * Removes the given <code>TransferDropTargetListener</code>.
+     * Listeners should not be removed while a drag and drop operation is in progress.
+     *
+     * @param listener the listener to remove
+     */
+    public void removeDropTargetListener(TransferDropTargetListener listener) {
+        if (currentListener is listener) {
+            currentListener = null;
+        }
+        listeners.remove(cast(Object)listener);
+    }
+
+    /**
+     * 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 bool setCurrentListener(TransferDropTargetListener listener,
+            DropTargetEvent event) {
+        if (currentListener is listener) {
+            return false;
+        }
+        if (currentListener !is null) {
+            SafeRunnable.run(new class SafeRunnable {
+                DropTargetEvent event_;
+                this(){ event_=event;}
+                public void run() {
+                    currentListener.dragLeave(event_);
+                }
+            });
+        }
+        currentListener = listener;
+        //      if (Policy.DEBUG_DRAG_DROP)
+        //          System.out.println("Current drop listener: " + listener); //$NON-NLS-1$
+        if (currentListener !is null) {
+            SafeRunnable.run(new class SafeRunnable {
+                DropTargetEvent event_;
+                this(){ event_=event;}
+                public void run() {
+                    currentListener.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 = originalDropType;
+
+        foreach( e; listeners ){
+            TransferDropTargetListener listener = cast(TransferDropTargetListener)e;
+            TransferData dataType = getSupportedTransferType(event.dataTypes,
+                    listener);
+            if (dataType !is 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;
+                }
+                event.currentDataType = originalDataType;
+            }
+        }
+        setCurrentListener(null, event);
+        event.detail = DND.DROP_NONE;
+
+        // -always- ensure that expand/scroll are on...otherwise
+        // if a valid drop target is a child of an invalid one
+        // you can't get there...
+        event.feedback = DND.FEEDBACK_EXPAND | DND.FEEDBACK_SCROLL;
+    }
+}
diff -r f12d40e7da8f -r 913f0fd3b347 dwtx/jface/util/TransferDragSourceListener.d
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dwtx/jface/util/TransferDragSourceListener.d	Thu Apr 03 19:20:11 2008 +0200
@@ -0,0 +1,45 @@
+/*******************************************************************************
+ * Copyright (c) 2000, 2005 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
+ * Port to the D programming language:
+ *     Frank Benoit <benoit@tionex.de>
+ *******************************************************************************/
+module dwtx.jface.util.TransferDragSourceListener;
+
+import dwt.dnd.DragSourceListener;
+import dwt.dnd.Transfer;
+
+import dwt.dwthelper.utils;
+
+/**
+ * A <code>TransferDragSourceListener</code> is a <code>DragSourceListener</code>
+ * that can handle one type of DWT {@link Transfer}.
+ * The purpose of a <code>TransferDragSourceListener</code> is to:
+ * <ul>
+ *   <li>Determine enablement for a drag operation. A <code>TransferDragSourceListener</code>
+ *  will not be used in a drag operation if the <code>DragSourceEvent#doit</code> field
+ *  is set to false in <code>DragSourceListener#dragStart(DragSourceEvent)</code>.
+ *   <li>Set data for a single type of drag and <code>Transfer</code> type.
+ * </ul>
+ * <p>
+ * A <code>DelegatingDragAdapter</code> allows these functions to be implemented
+ * separately for unrelated types of drags. <code>DelegatingDragAdapter</code> then
+ * combines the function of each <code>TransferDragSourceListener</code>, while
+ * allowing them to be implemented as if they were the only <code>DragSourceListener</code>.
+ * </p>
+ * @since 3.0
+ */
+public interface TransferDragSourceListener : DragSourceListener {
+    /**
+     * Returns the <code>Transfer</code> type that this listener can provide data for.
+     *
+     * @return the <code>Transfer</code> associated with this listener
+     */
+    Transfer getTransfer();
+}
diff -r f12d40e7da8f -r 913f0fd3b347 dwtx/jface/util/TransferDropTargetListener.d
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dwtx/jface/util/TransferDropTargetListener.d	Thu Apr 03 19:20:11 2008 +0200
@@ -0,0 +1,61 @@
+/*******************************************************************************
+ * Copyright (c) 2000, 2005 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
+ * Port to the D programming language:
+ *     Frank Benoit <benoit@tionex.de>
+ *******************************************************************************/
+module dwtx.jface.util.TransferDropTargetListener;
+
+import dwt.dnd.DropTargetEvent;
+import dwt.dnd.DropTargetListener;
+import dwt.dnd.Transfer;
+
+import dwt.dwthelper.utils;
+
+/**
+ * A <code>TransferDropTargetListener</code> is a <code>DropTragetListener</code>
+ * that handles one type of DWT {@link Transfer}.
+ * The purpose of a <code>TransferDropTargetListener</code> is to:
+ * <ul>
+ *   <li>Determine enablement for a drop operation. A <code>TransferDropTargetListener</code>
+ *      will not be used if <code>isEnabled</code> returns false.
+ *   <li>When enabled, optionally show feedback on the <code>DropTarget</code>.
+ *   <li>Perform the actual drop
+ * </ul>
+ * A <code>DelegatingDropAdapter</code> allows these functions to be implemented
+ * separately for unrelated types of drags. <code>DelegatingDropAdapter</code> then
+ * combines the function of each <code>TransferDropTargetListener</code>, while
+ * allowing them to be implemented as if they were the only <code>DragSourceListener</code>.
+ * @since 3.0
+ */
+public interface TransferDropTargetListener : DropTargetListener {
+    /**
+     * Returns the <code>Transfer</code> type that this listener can
+     * accept a drop operation for.
+     *
+     * @return the <code>Transfer</code> for this listener
+     */
+    Transfer getTransfer();
+
+    /**
+     * Returns <code>true</code> if this listener can handle the drop
+     * based on the given <code>DropTargetEvent</code>.
+     * <p>
+     * This method is called by the <code>DelegatingDropAdapter</code> only
+     * if the <code>DropTargetEvent</code> contains a transfer data type
+     * supported by this listener. The <code>Transfer</code> returned by the
+     * <code>#getTransfer()</code> method is used for this purpose.
+     * </p>
+     *
+     * @param event the drop target event
+     * @return <code>true</code> if the listener is enabled for the given
+     *  drop target event.
+     */
+    bool isEnabled(DropTargetEvent event);
+}