--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/org.eclipse.jface/src/org/eclipse/jface/util/DelegatingDropAdapter.d	Sat Mar 14 18:23:29 2009 +0100
@@ -0,0 +1,416 @@
+/*******************************************************************************
+ * 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 org.eclipse.jface.util.DelegatingDropAdapter;
+
+import org.eclipse.jface.util.TransferDropTargetListener;
+import org.eclipse.jface.util.SafeRunnable;
+
+
+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;
+
+import java.lang.all;
+import java.util.List;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.Set;
+
+/**
+ * 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 SWT <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, SWT.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 List listeners;
+
+    private TransferDropTargetListener currentListener;
+
+    private int originalDropType;
+
+    this(){
+        listeners = new ArrayList();
+    }
+
+    /**
+     * Adds the given <code>TransferDropTargetListener</code>.
+     *
+     * @param listener the new listener
+     */
+    public void addDropTargetListener(TransferDropTargetListener listener) {
+        listeners.add(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(event,newListener) SafeRunnable {
+                DropTargetEvent event_;
+                TransferDropTargetListener newListener_;
+                this(DropTargetEvent a,TransferDropTargetListener b){
+                    event_=a;
+                    newListener_=b;
+                }
+                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(event,newListener) SafeRunnable {
+                DropTargetEvent event_;
+                TransferDropTargetListener newListener_;
+                this(DropTargetEvent a,TransferDropTargetListener b){
+                    event_=a;
+                    newListener_=b;
+                }
+                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(event) SafeRunnable {
+                DropTargetEvent event_;
+                this(DropTargetEvent a){ event_=a;}
+                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(event) SafeRunnable {
+                DropTargetEvent event_;
+                this(DropTargetEvent a){ event_=a;}
+                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.isEmpty();
+    }
+
+    /**
+     * 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(event) SafeRunnable {
+                DropTargetEvent event_;
+                this(DropTargetEvent a){ event_=a;}
+                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(event) SafeRunnable {
+                DropTargetEvent event_;
+                this(DropTargetEvent a){ event_=a;}
+                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;
+
+        Iterator iter = listeners.iterator();
+        while (iter.hasNext()) {
+            TransferDropTargetListener listener = cast(TransferDropTargetListener) iter
+                    .next();
+            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;
+    }
+}