--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dwt/dnd/DropTarget.d	Wed Feb 13 04:51:22 2008 +0100
@@ -0,0 +1,709 @@
+/*******************************************************************************
+ * 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 dwt.dnd.DropTarget;
+
+import dwt.DWT;
+import dwt.DWTError;
+import dwt.DWTException;
+import dwt.internal.ole.win32.COM;
+import dwt.internal.win32.OS;
+import dwt.widgets.Control;
+import dwt.widgets.Event;
+import dwt.widgets.Listener;
+import dwt.widgets.Table;
+import dwt.widgets.Tree;
+import dwt.widgets.Widget;
+
+/**
+ *
+ * Class <code>DropTarget</code> defines the target object for a drag and drop transfer.
+ *
+ * IMPORTANT: This class is <em>not</em> intended to be subclassed.
+ *
+ * <p>This class identifies the <code>Control</code> over which the user must position the cursor
+ * in order to drop the data being transferred.  It also specifies what data types can be dropped on
+ * this control and what operations can be performed.  You may have several DropTragets in an
+ * application but there can only be a one to one mapping between a <code>Control</code> and a <code>DropTarget</code>.
+ * The DropTarget can receive data from within the same application or from other applications
+ * (such as text dragged from a text editor like Word).</p>
+ *
+ * <code><pre>
+ *  int operations = DND.DROP_MOVE | DND.DROP_COPY | DND.DROP_LINK;
+ *  Transfer[] types = new Transfer[] {TextTransfer.getInstance()};
+ *  DropTarget target = new DropTarget(label, operations);
+ *  target.setTransfer(types);
+ * </code></pre>
+ *
+ * <p>The application is notified of data being dragged over this control and of when a drop occurs by
+ * implementing the interface <code>DropTargetListener</code> which uses the class
+ * <code>DropTargetEvent</code>.  The application can modify the type of drag being performed
+ * on this Control at any stage of the drag by modifying the <code>event.detail</code> field or the
+ * <code>event.currentDataType</code> field.  When the data is dropped, it is the responsibility of
+ * the application to copy this data for its own purposes.
+ *
+ * <code><pre>
+ *  target.addDropListener (new DropTargetListener() {
+ *      public void dragEnter(DropTargetEvent event) {};
+ *      public void dragOver(DropTargetEvent event) {};
+ *      public void dragLeave(DropTargetEvent event) {};
+ *      public void dragOperationChanged(DropTargetEvent event) {};
+ *      public void dropAccept(DropTargetEvent event) {}
+ *      public void drop(DropTargetEvent event) {
+ *          // A drop has occurred, copy over the data
+ *          if (event.data is null) { // no data to copy, indicate failure in event.detail
+ *              event.detail = DND.DROP_NONE;
+ *              return;
+ *          }
+ *          label.setText ((String) event.data); // data copied to label text
+ *      }
+ *  });
+ * </pre></code>
+ *
+ * <dl>
+ *  <dt><b>Styles</b></dt> <dd>DND.DROP_NONE, DND.DROP_COPY, DND.DROP_MOVE, DND.DROP_LINK</dd>
+ *  <dt><b>Events</b></dt> <dd>DND.DragEnter, DND.DragLeave, DND.DragOver, DND.DragOperationChanged,
+ *                             DND.DropAccept, DND.Drop </dd>
+ * </dl>
+ */
+public class DropTarget : Widget {
+
+    Control control;
+    Listener controlListener;
+    Transfer[] transferAgents = new Transfer[0];
+    DropTargetEffect dropEffect;
+
+    // Track application selections
+    TransferData selectedDataType;
+    int selectedOperation;
+
+    // workaround - There is no event for "operation changed" so track operation based on key state
+    int keyOperation = -1;
+
+    // workaround - The dataobject address is only passed as an argument in drag enter and drop.
+    // To allow applications to query the data values during the drag over operations,
+    // maintain a reference to it.
+    IDataObject iDataObject;
+
+    // interfaces
+    COMObject iDropTarget;
+    int refCount;
+
+    static final String DEFAULT_DROP_TARGET_EFFECT = "DEFAULT_DROP_TARGET_EFFECT"; //$NON-NLS-1$
+    static final String DROPTARGETID = "DropTarget"; //$NON-NLS-1$
+
+/**
+ * Creates a new <code>DropTarget</code> to allow data to be dropped on the specified
+ * <code>Control</code>.
+ * Creating an instance of a DropTarget may cause system resources to be allocated
+ * depending on the platform.  It is therefore mandatory that the DropTarget instance
+ * be disposed when no longer required.
+ *
+ * @param control the <code>Control</code> over which the user positions the cursor to drop the data
+ * @param style the bitwise OR'ing of allowed operations; this may be a combination of any of
+ *         DND.DROP_NONE, DND.DROP_COPY, DND.DROP_MOVE, DND.DROP_LINK
+ *
+ * @exception DWTException <ul>
+ *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li>
+ *    <li>ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass</li>
+ * </ul>
+ * @exception DWTError <ul>
+ *    <li>ERROR_CANNOT_INIT_DROP - unable to initiate drop target; this will occur if more than one
+ *        drop target is created for a control or if the operating system will not allow the creation
+ *        of the drop target</li>
+ * </ul>
+ *
+ * <p>NOTE: ERROR_CANNOT_INIT_DROP should be an DWTException, since it is a
+ * recoverable error, but can not be changed due to backward compatibility.</p>
+ *
+ * @see Widget#dispose
+ * @see DropTarget#checkSubclass
+ * @see DND#DROP_NONE
+ * @see DND#DROP_COPY
+ * @see DND#DROP_MOVE
+ * @see DND#DROP_LINK
+ */
+public this(Control control, int style) {
+    super (control, checkStyle(style));
+    this.control = control;
+    if (control.getData(DROPTARGETID) !is null) {
+        DND.error(DND.ERROR_CANNOT_INIT_DROP);
+    }
+    control.setData(DROPTARGETID, this);
+    createCOMInterfaces();
+    this.AddRef();
+
+    if (COM.CoLockObjectExternal(iDropTarget.getAddress(), true, true) !is COM.S_OK)
+        DND.error(DND.ERROR_CANNOT_INIT_DROP);
+    if (COM.RegisterDragDrop( control.handle, iDropTarget.getAddress()) !is COM.S_OK)
+        DND.error(DND.ERROR_CANNOT_INIT_DROP);
+
+    controlListener = new Listener () {
+        public void handleEvent (Event event) {
+            if (!DropTarget.this.isDisposed()){
+                DropTarget.this.dispose();
+            }
+        }
+    };
+    control.addListener (DWT.Dispose, controlListener);
+
+    this.addListener(DWT.Dispose, new Listener () {
+        public void handleEvent (Event event) {
+            onDispose();
+        }
+    });
+
+    Object effect = control.getData(DEFAULT_DROP_TARGET_EFFECT);
+    if (effect instanceof DropTargetEffect) {
+        dropEffect = (DropTargetEffect) effect;
+    } else if (control instanceof Table) {
+        dropEffect = new TableDropTargetEffect((Table) control);
+    } else if (control instanceof Tree) {
+        dropEffect = new TreeDropTargetEffect((Tree) control);
+    }
+}
+
+static int checkStyle (int style) {
+    if (style is DWT.NONE) return DND.DROP_MOVE;
+    return style;
+}
+
+/**
+ * Adds the listener to the collection of listeners who will
+ * be notified when a drag and drop operation is in progress, by sending
+ * it one of the messages defined in the <code>DropTargetListener</code>
+ * interface.
+ *
+ * <p><ul>
+ * <li><code>dragEnter</code> is called when the cursor has entered the drop target boundaries
+ * <li><code>dragLeave</code> is called when the cursor has left the drop target boundaries and just before
+ * the drop occurs or is cancelled.
+ * <li><code>dragOperationChanged</code> is called when the operation being performed has changed
+ * (usually due to the user changing the selected modifier key(s) while dragging)
+ * <li><code>dragOver</code> is called when the cursor is moving over the drop target
+ * <li><code>dropAccept</code> is called just before the drop is performed.  The drop target is given
+ * the chance to change the nature of the drop or veto the drop by setting the <code>event.detail</code> field
+ * <li><code>drop</code> is called when the data is being dropped
+ * </ul></p>
+ *
+ * @param listener the listener which should be notified
+ *
+ * @exception IllegalArgumentException <ul>
+ *    <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
+ * </ul>
+ * @exception DWTException <ul>
+ *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
+ *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
+ * </ul>
+ *
+ * @see DropTargetListener
+ * @see #removeDropListener
+ * @see DropTargetEvent
+ */
+public void addDropListener(DropTargetListener listener) {
+    if (listener is null) DND.error (DWT.ERROR_NULL_ARGUMENT);
+    DNDListener typedListener = new DNDListener (listener);
+    typedListener.dndWidget = this;
+    addListener (DND.DragEnter, typedListener);
+    addListener (DND.DragLeave, typedListener);
+    addListener (DND.DragOver, typedListener);
+    addListener (DND.DragOperationChanged, typedListener);
+    addListener (DND.Drop, typedListener);
+    addListener (DND.DropAccept, typedListener);
+}
+
+int AddRef() {
+    refCount++;
+    return refCount;
+}
+
+protected void checkSubclass () {
+    String name = getClass().getName ();
+    String validName = DropTarget.class.getName();
+    if (!validName.equals(name)) {
+        DND.error (DWT.ERROR_INVALID_SUBCLASS);
+    }
+}
+
+void createCOMInterfaces() {
+    // register each of the interfaces that this object implements
+    iDropTarget = new COMObject(new int[]{2, 0, 0, 5, 4, 0, 5}){
+        public int method0(int[] args) {return QueryInterface(args[0], args[1]);}
+        public int method1(int[] args) {return AddRef();}
+        public int method2(int[] args) {return Release();}
+        public int method3(int[] args) {return DragEnter(args[0], args[1], args[2], args[3], args[4]);}
+        public int method4(int[] args) {return DragOver(args[0], args[1], args[2], args[3]);}
+        public int method5(int[] args) {return DragLeave();}
+        public int method6(int[] args) {return Drop(args[0], args[1], args[2], args[3], args[4]);}
+    };
+
+}
+
+void disposeCOMInterfaces() {
+    if (iDropTarget !is null)
+        iDropTarget.dispose();
+    iDropTarget = null;
+}
+
+int DragEnter(int pDataObject, int grfKeyState, int pt_x, int pt_y, int pdwEffect) {
+    selectedDataType = null;
+    selectedOperation = DND.DROP_NONE;
+    if (iDataObject !is null) iDataObject.Release();
+    iDataObject = null;
+
+    DNDEvent event = new DNDEvent();
+    if (!setEventData(event, pDataObject, grfKeyState, pt_x, pt_y, pdwEffect)) {
+        OS.MoveMemory(pdwEffect, new int[] {COM.DROPEFFECT_NONE}, 4);
+        return COM.S_FALSE;
+    }
+
+    // Remember the iDataObject because it is not passed into the DragOver callback
+    iDataObject = new IDataObject(pDataObject);
+    iDataObject.AddRef();
+
+    int allowedOperations = event.operations;
+    TransferData[] allowedDataTypes = new TransferData[event.dataTypes.length];
+    System.arraycopy(event.dataTypes, 0, allowedDataTypes, 0, allowedDataTypes.length);
+    notifyListeners(DND.DragEnter, event);
+    refresh();
+    if (event.detail is DND.DROP_DEFAULT) {
+        event.detail = (allowedOperations & DND.DROP_MOVE) !is 0 ? DND.DROP_MOVE : DND.DROP_NONE;
+    }
+
+    selectedDataType = null;
+    for (int i = 0; i < allowedDataTypes.length; i++) {
+        if (TransferData.sameType(allowedDataTypes[i], event.dataType)){
+            selectedDataType = allowedDataTypes[i];
+            break;
+        }
+    }
+
+    selectedOperation = DND.DROP_NONE;
+    if (selectedDataType !is null && ((allowedOperations & event.detail) !is 0)) {
+        selectedOperation = event.detail;
+    }
+
+    OS.MoveMemory(pdwEffect, new int[] {opToOs(selectedOperation)}, 4);
+    return COM.S_OK;
+}
+
+int DragLeave() {
+    keyOperation = -1;
+
+    if (iDataObject is null) return COM.S_FALSE;
+
+    DNDEvent event = new DNDEvent();
+    event.widget = this;
+    event.time = OS.GetMessageTime();
+    event.detail = DND.DROP_NONE;
+    notifyListeners(DND.DragLeave, event);
+    refresh();
+
+    iDataObject.Release();
+    iDataObject = null;
+    return COM.S_OK;
+}
+
+int DragOver(int grfKeyState, int pt_x, int pt_y, int pdwEffect) {
+    if (iDataObject is null) return COM.S_FALSE;
+    int oldKeyOperation = keyOperation;
+
+    DNDEvent event = new DNDEvent();
+    if (!setEventData(event, iDataObject.getAddress(), grfKeyState, pt_x, pt_y, pdwEffect)) {
+        keyOperation = -1;
+        OS.MoveMemory(pdwEffect, new int[] {COM.DROPEFFECT_NONE}, 4);
+        return COM.S_FALSE;
+    }
+
+    int allowedOperations = event.operations;
+    TransferData[] allowedDataTypes = new TransferData[event.dataTypes.length];
+    System.arraycopy(event.dataTypes, 0, allowedDataTypes, 0, allowedDataTypes.length);
+
+    if (keyOperation is oldKeyOperation) {
+        event.type = DND.DragOver;
+        event.dataType = selectedDataType;
+        event.detail = selectedOperation;
+    } else {
+        event.type = DND.DragOperationChanged;
+        event.dataType = selectedDataType;
+    }
+    notifyListeners(event.type, event);
+    refresh();
+    if (event.detail is DND.DROP_DEFAULT) {
+        event.detail = (allowedOperations & DND.DROP_MOVE) !is 0 ? DND.DROP_MOVE : DND.DROP_NONE;
+    }
+
+    selectedDataType = null;
+    for (int i = 0; i < allowedDataTypes.length; i++) {
+        if (TransferData.sameType(allowedDataTypes[i], event.dataType)){
+            selectedDataType = allowedDataTypes[i];
+            break;
+        }
+    }
+
+    selectedOperation = DND.DROP_NONE;
+    if (selectedDataType !is null && ((allowedOperations & event.detail) is event.detail)) {
+        selectedOperation = event.detail;
+    }
+
+    OS.MoveMemory(pdwEffect, new int[] {opToOs(selectedOperation)}, 4);
+    return COM.S_OK;
+}
+
+int Drop(int pDataObject, int grfKeyState, int pt_x, int pt_y, int pdwEffect) {
+    DNDEvent event = new DNDEvent();
+    event.widget = this;
+    event.time = OS.GetMessageTime();
+    if (dropEffect !is null) {
+        event.item = dropEffect.getItem(pt_x, pt_y);
+    }
+    event.detail = DND.DROP_NONE;
+    notifyListeners(DND.DragLeave, event);
+    refresh();
+
+    event = new DNDEvent();
+    if (!setEventData(event, pDataObject, grfKeyState, pt_x, pt_y, pdwEffect)) {
+        keyOperation = -1;
+        OS.MoveMemory(pdwEffect, new int[] {COM.DROPEFFECT_NONE}, 4);
+        return COM.S_FALSE;
+    }
+    keyOperation = -1;
+    int allowedOperations = event.operations;
+    TransferData[] allowedDataTypes = new TransferData[event.dataTypes.length];
+    System.arraycopy(event.dataTypes, 0, allowedDataTypes, 0, allowedDataTypes.length);
+    event.dataType = selectedDataType;
+    event.detail = selectedOperation;
+    notifyListeners(DND.DropAccept,event);
+    refresh();
+
+    selectedDataType = null;
+    for (int i = 0; i < allowedDataTypes.length; i++) {
+        if (TransferData.sameType(allowedDataTypes[i], event.dataType)){
+            selectedDataType = allowedDataTypes[i];
+            break;
+        }
+    }
+    selectedOperation = DND.DROP_NONE;
+    if (selectedDataType !is null && (allowedOperations & event.detail) is event.detail) {
+        selectedOperation = event.detail;
+    }
+
+    if (selectedOperation is DND.DROP_NONE){
+        OS.MoveMemory(pdwEffect, new int[] {COM.DROPEFFECT_NONE}, 4);
+        return COM.S_OK;
+    }
+
+    // Get Data in a Java format
+    Object object = null;
+    for (int i = 0; i < transferAgents.length; i++){
+        Transfer transfer = transferAgents[i];
+        if (transfer !is null && transfer.isSupportedType(selectedDataType)){
+            object = transfer.nativeToJava(selectedDataType);
+            break;
+        }
+    }
+    if (object is null){
+        selectedOperation = DND.DROP_NONE;
+    }
+
+    event.detail = selectedOperation;
+    event.dataType = selectedDataType;
+    event.data = object;
+    OS.ImageList_DragShowNolock(false);
+    try {
+        notifyListeners(DND.Drop,event);
+    } finally {
+        OS.ImageList_DragShowNolock(true);
+    }
+    refresh();
+    selectedOperation = DND.DROP_NONE;
+    if ((allowedOperations & event.detail) is event.detail) {
+        selectedOperation = event.detail;
+    }
+    //notify source of action taken
+    OS.MoveMemory(pdwEffect, new int[] {opToOs(selectedOperation)}, 4);
+    return COM.S_OK;
+}
+
+/**
+ * Returns the Control which is registered for this DropTarget.  This is the control over which the
+ * user positions the cursor to drop the data.
+ *
+ * @return the Control which is registered for this DropTarget
+ */
+public Control getControl () {
+    return control;
+}
+
+/**
+ * Returns the drop effect for this DropTarget.  This drop effect will be
+ * used during a drag and drop to display the drag under effect on the
+ * target widget.
+ *
+ * @return the drop effect that is registered for this DropTarget
+ *
+ * @since 3.3
+ */
+public DropTargetEffect getDropTargetEffect() {
+    return dropEffect;
+}
+
+int getOperationFromKeyState(int grfKeyState) {
+    bool ctrl = (grfKeyState & OS.MK_CONTROL) !is 0;
+    bool shift = (grfKeyState & OS.MK_SHIFT) !is 0;
+    bool alt = (grfKeyState & OS.MK_ALT) !is 0;
+    if (alt) {
+        if (ctrl || shift) return DND.DROP_DEFAULT;
+        return DND.DROP_LINK;
+    }
+    if (ctrl && shift) return DND.DROP_LINK;
+    if (ctrl)return DND.DROP_COPY;
+    if (shift)return DND.DROP_MOVE;
+    return DND.DROP_DEFAULT;
+}
+
+/**
+ * Returns a list of the data types that can be transferred to this DropTarget.
+ *
+ * @return a list of the data types that can be transferred to this DropTarget
+ */
+public Transfer[] getTransfer() {
+    return transferAgents;
+}
+
+void onDispose () {
+    if (control is null) return;
+
+    COM.RevokeDragDrop(control.handle);
+
+    if (controlListener !is null)
+        control.removeListener(DWT.Dispose, controlListener);
+    controlListener = null;
+    control.setData(DROPTARGETID, null);
+    transferAgents = null;
+    control = null;
+
+    COM.CoLockObjectExternal(iDropTarget.getAddress(), false, true);
+
+    this.Release();
+
+    COM.CoFreeUnusedLibraries();
+}
+
+int opToOs(int operation) {
+    int osOperation = 0;
+    if ((operation & DND.DROP_COPY) !is 0){
+        osOperation |= COM.DROPEFFECT_COPY;
+    }
+    if ((operation & DND.DROP_LINK) !is 0) {
+        osOperation |= COM.DROPEFFECT_LINK;
+    }
+    if ((operation & DND.DROP_MOVE) !is 0) {
+        osOperation |= COM.DROPEFFECT_MOVE;
+    }
+    return osOperation;
+}
+
+int osToOp(int osOperation){
+    int operation = 0;
+    if ((osOperation & COM.DROPEFFECT_COPY) !is 0){
+        operation |= DND.DROP_COPY;
+    }
+    if ((osOperation & COM.DROPEFFECT_LINK) !is 0) {
+        operation |= DND.DROP_LINK;
+    }
+    if ((osOperation & COM.DROPEFFECT_MOVE) !is 0) {
+        operation |= DND.DROP_MOVE;
+    }
+    return operation;
+}
+
+/* QueryInterface([in] iid, [out] ppvObject)
+ * Ownership of ppvObject transfers from callee to caller so reference count on ppvObject
+ * must be incremented before returning.  Caller is responsible for releasing ppvObject.
+ */
+int QueryInterface(int riid, int ppvObject) {
+
+    if (riid is 0 || ppvObject is 0)
+        return COM.E_INVALIDARG;
+    GUID guid = new GUID();
+    COM.MoveMemory(guid, riid, GUID.sizeof);
+    if (COM.IsEqualGUID(guid, COM.IIDIUnknown) || COM.IsEqualGUID(guid, COM.IIDIDropTarget)) {
+        OS.MoveMemory(ppvObject, new int[] {iDropTarget.getAddress()}, 4);
+        AddRef();
+        return COM.S_OK;
+    }
+
+    OS.MoveMemory(ppvObject, new int[] {0}, 4);
+    return COM.E_NOINTERFACE;
+}
+
+int Release() {
+    refCount--;
+
+    if (refCount is 0) {
+        disposeCOMInterfaces();
+        COM.CoFreeUnusedLibraries();
+    }
+
+    return refCount;
+}
+
+void refresh() {
+    if (control is null || control.isDisposed()) return;
+    int handle = control.handle;
+    RECT lpRect = new RECT();
+    if (OS.GetUpdateRect(handle, lpRect, false)) {
+        OS.ImageList_DragShowNolock(false);
+        OS.RedrawWindow(handle, lpRect, 0, OS.RDW_UPDATENOW | OS.RDW_INVALIDATE);
+        OS.ImageList_DragShowNolock(true);
+    }
+}
+
+/**
+ * Removes the listener from the collection of listeners who will
+ * be notified when a drag and drop operation is in progress.
+ *
+ * @param listener the listener which should be notified
+ *
+ * @exception IllegalArgumentException <ul>
+ *    <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
+ * </ul>
+ * @exception DWTException <ul>
+ *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
+ *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
+ * </ul>
+ *
+ * @see DropTargetListener
+ * @see #addDropListener
+ */
+public void removeDropListener(DropTargetListener listener) {
+    if (listener is null) DND.error (DWT.ERROR_NULL_ARGUMENT);
+    removeListener (DND.DragEnter, listener);
+    removeListener (DND.DragLeave, listener);
+    removeListener (DND.DragOver, listener);
+    removeListener (DND.DragOperationChanged, listener);
+    removeListener (DND.Drop, listener);
+    removeListener (DND.DropAccept, listener);
+}
+
+/**
+ * Specifies the drop effect for this DropTarget.  This drop effect will be
+ * used during a drag and drop to display the drag under effect on the
+ * target widget.
+ *
+ * @param effect the drop effect that is registered for this DropTarget
+ *
+ * @since 3.3
+ */
+public void setDropTargetEffect(DropTargetEffect effect) {
+    dropEffect = effect;
+}
+
+bool setEventData(DNDEvent event, int pDataObject, int grfKeyState, int pt_x, int pt_y, int pdwEffect) {
+    if (pDataObject is 0 || pdwEffect is 0) return false;
+
+    // get allowed operations
+    int style = getStyle();
+    int[] operations = new int[1];
+    OS.MoveMemory(operations, pdwEffect, 4);
+    operations[0] = osToOp(operations[0]) & style;
+    if (operations[0] is DND.DROP_NONE) return false;
+
+    // get current operation
+    int operation = getOperationFromKeyState(grfKeyState);
+    keyOperation = operation;
+    if (operation is DND.DROP_DEFAULT) {
+        if ((style & DND.DROP_DEFAULT) is 0) {
+            operation = (operations[0] & DND.DROP_MOVE) !is 0 ? DND.DROP_MOVE : DND.DROP_NONE;
+        }
+    } else {
+        if ((operation & operations[0]) is 0) operation = DND.DROP_NONE;
+    }
+
+    // Get allowed transfer types
+    TransferData[] dataTypes = new TransferData[0];
+    IDataObject dataObject = new IDataObject(pDataObject);
+    dataObject.AddRef();
+    try {
+        int[] address = new int[1];
+        if (dataObject.EnumFormatEtc(COM.DATADIR_GET, address) !is COM.S_OK) {
+            return false;
+        }
+        IEnumFORMATETC enumFormatetc = new IEnumFORMATETC(address[0]);
+        try {
+            // Loop over enumerator and save any types that match what we are looking for
+            int rgelt = OS.GlobalAlloc(OS.GMEM_FIXED | OS.GMEM_ZEROINIT, FORMATETC.sizeof);
+            try {
+                int[] pceltFetched = new int[1];
+                enumFormatetc.Reset();
+                while (enumFormatetc.Next(1, rgelt, pceltFetched) is COM.S_OK && pceltFetched[0] is 1) {
+                    TransferData transferData = new TransferData();
+                    transferData.formatetc = new FORMATETC();
+                    COM.MoveMemory(transferData.formatetc, rgelt, FORMATETC.sizeof);
+                    transferData.type = transferData.formatetc.cfFormat;
+                    transferData.pIDataObject = pDataObject;
+                    for (int i = 0; i < transferAgents.length; i++){
+                        Transfer transfer = transferAgents[i];
+                        if (transfer !is null && transfer.isSupportedType(transferData)){
+                            TransferData[] newDataTypes = new TransferData[dataTypes.length + 1];
+                            System.arraycopy(dataTypes, 0, newDataTypes, 0, dataTypes.length);
+                            newDataTypes[dataTypes.length] = transferData;
+                            dataTypes = newDataTypes;
+                            break;
+                        }
+                    }
+                }
+            } finally {
+                OS.GlobalFree(rgelt);
+            }
+        } finally {
+            enumFormatetc.Release();
+        }
+    } finally {
+        dataObject.Release();
+    }
+    if (dataTypes.length is 0) return false;
+
+    event.widget = this;
+    event.x = pt_x;
+    event.y = pt_y;
+    event.time = OS.GetMessageTime();
+    event.feedback = DND.FEEDBACK_SELECT;
+    event.dataTypes = dataTypes;
+    event.dataType = dataTypes[0];
+    if (dropEffect !is null) {
+        event.item = dropEffect.getItem(pt_x, pt_y);
+    }
+    event.operations = operations[0];
+    event.detail = operation;
+    return true;
+}
+
+/**
+ * Specifies the data types that can be transferred to this DropTarget.  If data is
+ * being dragged that does not match one of these types, the drop target will be notified of
+ * the drag and drop operation but the currentDataType will be null and the operation
+ * will be DND.NONE.
+ *
+ * @param transferAgents a list of Transfer objects which define the types of data that can be
+ *                       dropped on this target
+ *
+ * @exception IllegalArgumentException <ul>
+ *    <li>ERROR_NULL_ARGUMENT - if transferAgents is null</li>
+ * </ul>
+ */
+public void setTransfer(Transfer[] transferAgents){
+    if (transferAgents is null) DND.error(DWT.ERROR_NULL_ARGUMENT);
+    this.transferAgents = transferAgents;
+}
+}