/*******************************************************************************
 * Copyright (c) 2000, 2008 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.swt.dnd.DropTarget;



import org.eclipse.swt.SWT;
import org.eclipse.swt.SWTError;
import org.eclipse.swt.SWTException;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.internal.gtk.OS;
import org.eclipse.swt.widgets.Combo;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Table;
import org.eclipse.swt.widgets.Tree;
import org.eclipse.swt.widgets.Widget;
import org.eclipse.swt.dnd.DND;
import org.eclipse.swt.dnd.Transfer;
import org.eclipse.swt.dnd.DropTargetEffect;
import org.eclipse.swt.dnd.DNDEvent;
import org.eclipse.swt.dnd.DNDListener;
import org.eclipse.swt.dnd.TransferData;
import org.eclipse.swt.dnd.DropTargetListener;
import org.eclipse.swt.dnd.TableDropTargetEffect;
import org.eclipse.swt.dnd.TreeDropTargetEffect;
import java.lang.all;

import java.lang.Thread;
version(Tango){
static import tango.stdc..string;
} else { // Phobos
}

/**
 *
 * 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>
 *
 * @see <a href="http://www.eclipse.org/swt/snippets/#dnd">Drag and Drop snippets</a>
 * @see <a href="http://www.eclipse.org/swt/examples.php">SWT Example: DNDExample</a>
 * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>
 */
public class DropTarget : Widget {

    Control control;
    Listener controlListener;
    Transfer[] transferAgents;
    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 - Simulate events when the mouse is not moving
    long dragOverStart;
    Runnable dragOverHeartbeat;
    DNDEvent dragOverEvent;

    ptrdiff_t drag_motion_handler;
    ptrdiff_t drag_leave_handler;
    ptrdiff_t drag_data_received_handler;
    ptrdiff_t drag_drop_handler;

    static const String DEFAULT_DROP_TARGET_EFFECT = "DEFAULT_DROP_TARGET_EFFECT"; //$NON-NLS-1$
    static const int DRAGOVER_HYSTERESIS = 50;

//     static Callback Drag_Motion;
//     static Callback Drag_Leave;
//     static Callback Drag_Data_Received;
//     static Callback Drag_Drop;
//
//      static this(){
//         Drag_Motion = new Callback(DropTarget.class, "Drag_Motion", 5); //$NON-NLS-1$
//         if (Drag_Motion.getAddress() is 0) SWT.error(SWT.ERROR_NO_MORE_CALLBACKS);
//         Drag_Leave = new Callback(DropTarget.class, "Drag_Leave", 3); //$NON-NLS-1$
//         if (Drag_Leave.getAddress() is 0) SWT.error(SWT.ERROR_NO_MORE_CALLBACKS);
//         Drag_Data_Received = new Callback(DropTarget.class, "Drag_Data_Received", 7); //$NON-NLS-1$
//         if (Drag_Data_Received.getAddress() is 0) SWT.error(SWT.ERROR_NO_MORE_CALLBACKS);
//         Drag_Drop = new Callback(DropTarget.class, "Drag_Drop", 5); //$NON-NLS-1$
//         if (Drag_Drop.getAddress() is 0) SWT.error(SWT.ERROR_NO_MORE_CALLBACKS);
//     }

/**
 * 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 SWTException <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 SWTError <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 SWTException, 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 (Drag_Motion is null || Drag_Leave is null || Drag_Data_Received is null || Drag_Drop is null) {
//          DND.error(DND.ERROR_CANNOT_INIT_DROP);
//     }
    if (control.getData(DND.DROP_TARGET_KEY) !is null) {
        DND.error(DND.ERROR_CANNOT_INIT_DROP);
    }
    control.setData(DND.DROP_TARGET_KEY, this);

    drag_motion_handler = OS.g_signal_connect(control.handle, OS.drag_motion.ptr, cast(GCallback)&Drag_Motion, null);
    drag_leave_handler = OS.g_signal_connect(control.handle, OS.drag_leave.ptr, cast(GCallback)&Drag_Leave, null);
    drag_data_received_handler = OS.g_signal_connect(control.handle, OS.drag_data_received.ptr, cast(GCallback)&Drag_Data_Received, null);
    drag_drop_handler = OS.g_signal_connect(control.handle, OS.drag_drop.ptr, cast(GCallback)&Drag_Drop, null);

    // Dispose listeners
    controlListener = new class() Listener{
        public void handleEvent(Event event){
            if (!this.outer.isDisposed()){
                this.outer.dispose();
            }
        }
    };
    control.addListener(SWT.Dispose, controlListener);

    this.addListener(SWT.Dispose, new class() Listener {
        public void handleEvent(Event event){
            onDispose();
        }
    });

    Object effect = control.getData(DEFAULT_DROP_TARGET_EFFECT);
    if ( auto de = cast(DropTargetEffect)effect ) {
        dropEffect = de;
    } else if ( auto table = cast(Table)control ) {
        dropEffect = new TableDropTargetEffect(table);
    } else if ( auto tree = cast(Tree) control ) {
        dropEffect = new TreeDropTargetEffect(tree);
    }

    dragOverHeartbeat = new class() Runnable {
        public void run() {
            Control control = this.outer.control;
            if (control is null || control.isDisposed() || dragOverStart is 0) return;
            long time = System.currentTimeMillis();
            int delay = DRAGOVER_HYSTERESIS;
            if (time < dragOverStart) {
                delay = cast(int)(dragOverStart - time);
            } else {
                dragOverEvent.time += DRAGOVER_HYSTERESIS;
                int allowedOperations = dragOverEvent.operations;
                TransferData[] allowedTypes = dragOverEvent.dataTypes;
                //pass a copy of data types in to listeners in case application modifies it
                TransferData[] dataTypes = new TransferData[allowedTypes.length];
                System.arraycopy(allowedTypes, 0, dataTypes, 0, dataTypes.length);

                DNDEvent event = new DNDEvent();
                event.widget = dragOverEvent.widget;
                event.x = dragOverEvent.x;
                event.y = dragOverEvent.y;
                event.time = dragOverEvent.time;
                event.feedback = DND.FEEDBACK_SELECT;
                event.dataTypes = dataTypes;
                event.dataType = selectedDataType;
                event.operations = dragOverEvent.operations;
                event.detail  = selectedOperation;
                if (dropEffect !is null) {
                    event.item = dropEffect.getItem(dragOverEvent.x, dragOverEvent.y);
                }
                selectedDataType = null;
                selectedOperation = DND.DROP_NONE;
                notifyListeners(DND.DragOver, event);
                if (event.dataType !is null) {
                    for (int i = 0; i < allowedTypes.length; i++) {
                        if (allowedTypes[i].type is event.dataType.type) {
                            selectedDataType = event.dataType;
                            break;
                        }
                    }
                }
                if (selectedDataType !is null && (event.detail & allowedOperations) !is 0) {
                    selectedOperation = event.detail;
                }
            }
            control = this.outer.control;
            if (control is null || control.isDisposed()) return;
            control.getDisplay().timerExec(delay, dragOverHeartbeat);
        }
    };
}

static int checkStyle (int style) {
    if (style is SWT.NONE) return DND.DROP_MOVE;
    return style;
}

private static extern(C) void Drag_Data_Received (
    GtkWidget *widget,
    GdkDragContext *context,
    int x,
    int y,
    GtkSelectionData *data,
    uint info,
    uint time,
    void* user_data)
{
    DropTarget target = FindDropTarget(widget);
    if (target is null) return;
    target.drag_data_received (widget, context, x, y, data, info, time);
}

private static extern(C) int Drag_Drop(
    GtkWidget *widget,
    GdkDragContext *context,
    int x,
    int y,
    uint time,
    void* user_data)
{
    DropTarget target = FindDropTarget(widget);
    if (target is null) return 0;
    return target.drag_drop (widget, context, x, y, time) ? 1 : 0;
}

private static extern(C) void Drag_Leave (
    GtkWidget *widget,
    GdkDragContext *context,
    uint time,
    void* user_data)
{
    DropTarget target = FindDropTarget(widget);
    if (target is null) return;
    target.drag_leave (widget, context, time);
}

private static extern(C) int Drag_Motion (
    GtkWidget *widget,
    GdkDragContext *context,
    int x,
    int y,
    uint time,
    void* user_data)
{
    DropTarget target = FindDropTarget(widget);
    if (target is null) return 0;
    return target.drag_motion (widget, context, x, y, time) ? 1 : 0;
}

static DropTarget FindDropTarget(GtkWidget* handle) {
    Display display = Display.findDisplay(Thread.currentThread());
    if (display is null || display.isDisposed()) return null;
    Widget widget = display.findWidget(handle);
    if (widget is null) return null;
    return cast(DropTarget)widget.getData(DND.DROP_TARGET_KEY);
}

/**
 * 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 SWTException <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 #getDropListeners
 * @see #removeDropListener
 * @see DropTargetEvent
 */
public void addDropListener(DropTargetListener listener) {
    if (listener is null) DND.error (SWT.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);
}

protected override void checkSubclass () {
    String name = this.classinfo.name;
    String validName = DropTarget.classinfo.name;
    if ( validName !=/*eq*/ name ) {
        DND.error (SWT.ERROR_INVALID_SUBCLASS);
    }
}

void drag_data_received (
    GtkWidget *widget,
    GdkDragContext *context,
    int x,
    int y,
    GtkSelectionData *data,
    uint info,
    uint time )
{
    DNDEvent event = new DNDEvent();
    if (data is null || !setEventData(context, x, y, time, event)) {
        keyOperation = -1;
        return;
    }
    keyOperation = -1;

    int allowedOperations = event.operations;

    // Get data in a Java format
    Object object = null;
    TransferData transferData = new TransferData();
    if (data.data !is null) {
        transferData.type = data.type;
        transferData.length = data.length;
        transferData.pValue = data.data;
        transferData.format = data.format;
        for (int i = 0; i < transferAgents.length; i++) {
            Transfer transfer = transferAgents[i];
            if (transfer !is null && transfer.isSupportedType(transferData)) {
                object = transfer.nativeToJava(transferData);
                break;
            }
        }
    }
    if (object is null) {
        selectedOperation = DND.DROP_NONE;
    }

    event.detail = selectedOperation;
    event.dataType = transferData;
    event.data = object;
    selectedOperation = DND.DROP_NONE;
    notifyListeners(DND.Drop, event);
    if ((allowedOperations & event.detail) is event.detail) {
        selectedOperation = event.detail;
    }
    //stop native handler
    OS.g_signal_stop_emission_by_name(widget, OS.drag_data_received.ptr);

    //notify source of action taken
    OS.gtk_drag_finish(context, selectedOperation !is DND.DROP_NONE, selectedOperation is DND.DROP_MOVE, time);
    return;
}

bool drag_drop(
    GtkWidget *widget,
    GdkDragContext *context,
    int x,
    int y,
    uint time)
{
    DNDEvent event = new DNDEvent();
    if (!setEventData(context, x, y, time, event)) {
        keyOperation = -1;
        return 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;
    selectedDataType = null;
    selectedOperation = DND.DROP_NONE;
    notifyListeners(DND.DropAccept,event);
    if (event.dataType !is null) {
        for (int i = 0; i < allowedDataTypes.length; i++) {
            if (allowedDataTypes[i].type is event.dataType.type) {
                selectedDataType = allowedDataTypes[i];
                break;
            }
        }
    }
    if (selectedDataType !is null && ((event.detail & allowedOperations) is event.detail)) {
        selectedOperation = event.detail;
    }
    if (selectedOperation is DND.DROP_NONE) {
        // this was not a successful drop
        return false;
    }
    // ask drag source for dropped data
    OS.gtk_drag_get_data(widget, context, selectedDataType.type, time);
    return true;
}

void drag_leave(
    GtkWidget *widget,
    GdkDragContext *context,
    uint time )
{
    updateDragOverHover(0, null);

    if (keyOperation is -1) return;
    keyOperation = -1;

    DNDEvent event = new DNDEvent();
    event.widget = this;
    event.time = time;
    event.detail = DND.DROP_NONE;
    notifyListeners(DND.DragLeave, event);
}

bool drag_motion (
    GtkWidget *widget,
    GdkDragContext *context,
    int x,
    int y,
    uint time)
{
    int oldKeyOperation = keyOperation;

    if (oldKeyOperation is -1) { //drag enter
        selectedDataType = null;
        selectedOperation = DND.DROP_NONE;
    }

    DNDEvent event = new DNDEvent();
    if (!setEventData(context, x, y, time, event)) {
        keyOperation = -1;
        OS.gdk_drag_status(context, 0, time);
        return false;
    }

    int allowedOperations = event.operations;
    TransferData[] allowedDataTypes = new TransferData[event.dataTypes.length];
    System.arraycopy(event.dataTypes, 0, allowedDataTypes, 0, allowedDataTypes.length);

    if (oldKeyOperation is -1) {
        event.type = DND.DragEnter;
    } else {
        if (keyOperation is oldKeyOperation) {
            event.type = DND.DragOver;
            event.dataType = selectedDataType;
            event.detail = selectedOperation;
        } else {
            event.type = DND.DragOperationChanged;
            event.dataType = selectedDataType;
        }
    }
    updateDragOverHover(DRAGOVER_HYSTERESIS, event);
    selectedDataType = null;
    selectedOperation = DND.DROP_NONE;
    notifyListeners(event.type, event);
    if (event.detail is DND.DROP_DEFAULT) {
        event.detail = (allowedOperations & DND.DROP_MOVE) !is 0 ? DND.DROP_MOVE : DND.DROP_NONE;
    }
    if (event.dataType !is null) {
        for (int i = 0; i < allowedDataTypes.length; i++) {
            if (allowedDataTypes[i].type is event.dataType.type) {
                selectedDataType = allowedDataTypes[i];
                break;
            }
        }
    }
    if (selectedDataType !is null && (allowedOperations & event.detail) !is 0) {
        selectedOperation = event.detail;
    }

    switch (selectedOperation) {
        case DND.DROP_NONE:
            OS.gdk_drag_status(context, 0, time);
            break;
        case DND.DROP_COPY:
            OS.gdk_drag_status(context, OS.GDK_ACTION_COPY, time);
            break;
        case DND.DROP_MOVE:
            OS.gdk_drag_status(context, OS.GDK_ACTION_MOVE, time);
            break;
        case DND.DROP_LINK:
            OS.gdk_drag_status(context, OS.GDK_ACTION_LINK, time);
            break;
        default:
    }

    if (oldKeyOperation is -1) {
        dragOverHeartbeat.run();
    }
    return true;
}

/**
 * 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 an array 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.
 *
 * @return the listeners who will be notified when a drag and drop 
 * operation is in progress
 *
 * @exception SWTException <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
 * @see #removeDropListener
 * @see DropTargetEvent
 *
 * @since 3.4
 */
public DropTargetListener[] getDropListeners() {
    Listener[] listeners = getListeners(DND.DragEnter);
    auto length = listeners.length;
    DropTargetListener[] dropListeners = new DropTargetListener[length];
    int count = 0;
    for (typeof(length) i = 0; i < length; i++) {
        Listener listener = listeners[i];
        if ( auto l = cast(DNDListener)listener ) {
            dropListeners[count] = cast(DropTargetListener) (l.getEventListener());
            count++;
        }
    }
    if (count is length) return dropListeners;
    DropTargetListener[] result = new DropTargetListener[count];
    SimpleType!(DropTargetListener).arraycopy(dropListeners, 0, result, 0, count);
    return result;
}

/**
 * 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 state;
    OS.gdk_window_get_pointer(null, null, null, &state);
    bool ctrl = (state & OS.GDK_CONTROL_MASK) !is 0;
    bool shift = (state & OS.GDK_SHIFT_MASK) !is 0;
    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;
    OS.g_signal_handler_disconnect(control.handle, drag_motion_handler);
    OS.g_signal_handler_disconnect(control.handle, drag_leave_handler);
    OS.g_signal_handler_disconnect(control.handle, drag_data_received_handler);
    OS.g_signal_handler_disconnect(control.handle, drag_drop_handler);
    if (transferAgents.length !is 0)
        OS.gtk_drag_dest_unset(control.handle);
    transferAgents = null;
    if (controlListener !is null)
        control.removeListener(SWT.Dispose, controlListener);
    control.setData(DND.DROP_TARGET_KEY, null);
    control = null;
    controlListener = null;
}

int opToOsOp(int operation){
    int osOperation = 0;
    if ((operation & DND.DROP_COPY) is DND.DROP_COPY)
        osOperation |= OS.GDK_ACTION_COPY;
    if ((operation & DND.DROP_MOVE) is DND.DROP_MOVE)
        osOperation |= OS.GDK_ACTION_MOVE;
    if ((operation & DND.DROP_LINK) is DND.DROP_LINK)
        osOperation |= OS.GDK_ACTION_LINK;
    return osOperation;
}

int osOpToOp(int osOperation){
    int operation = DND.DROP_NONE;
    if ((osOperation & OS.GDK_ACTION_COPY) is OS.GDK_ACTION_COPY)
        operation |= DND.DROP_COPY;
    if ((osOperation & OS.GDK_ACTION_MOVE) is OS.GDK_ACTION_MOVE)
        operation |= DND.DROP_MOVE;
    if ((osOperation & OS.GDK_ACTION_LINK) is OS.GDK_ACTION_LINK)
        operation |= DND.DROP_LINK;
    return operation;
}

/**
 * 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 no longer be notified
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
 * </ul>
 * @exception SWTException <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
 * @see #getDropListeners
 */
public void removeDropListener(DropTargetListener listener) {
    if (listener is null) DND.error (SWT.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 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(SWT.ERROR_NULL_ARGUMENT);

    if (this.transferAgents.length !is 0) {
        OS.gtk_drag_dest_unset(control.handle);
    }
    this.transferAgents = transferAgents;

    GtkTargetEntry*[] targets;
    for (int i = 0; i < transferAgents.length; i++) {
        Transfer transfer = transferAgents[i];
        if (transfer !is null) {
            int[] typeIds = transfer.getTypeIds();
            String[] typeNames = transfer.getTypeNames();
            for (int j = 0; j < typeIds.length; j++) {
                GtkTargetEntry* entry = new GtkTargetEntry();
                entry.target = cast(char*)
                    OS.g_malloc(typeNames[j].length +1);
                entry.target[ 0 .. typeNames[j].length ] = typeNames[j];
                entry.target[ typeNames[j].length ] = '\0';
                entry.info = typeIds[j];
                GtkTargetEntry*[] newTargets = new GtkTargetEntry*[targets.length + 1];
                SimpleType!(GtkTargetEntry*).arraycopy(targets, 0, newTargets,
                                             0, targets.length);
                newTargets[targets.length] = entry;
                targets = newTargets;
            }
        }
    }

    auto pTargets = OS.g_malloc(targets.length * GtkTargetEntry.sizeof);
    for (int i = 0; i < targets.length; i++) {
        OS.memmove(pTargets + i*GtkTargetEntry.sizeof, targets[i], GtkTargetEntry.sizeof);
    }

    int actions = opToOsOp(getStyle());
    if ( auto c = cast(Combo)control ) {
        if ((control.getStyle() & SWT.READ_ONLY) is 0) {
            auto entryHandle = OS.gtk_bin_get_child (control.handle);
            if (entryHandle !is null) {
                OS.gtk_drag_dest_unset(entryHandle);
            }
        }
    }
    OS.gtk_drag_dest_set(control.handle, 0, pTargets,
                         cast(int)/*64bit*/targets.length, actions);

    for (int i = 0; i < targets.length; i++) {
        OS.g_free(targets[i].target);
    }
}

/**
 * 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(GdkDragContext* dragContext, int x, int y, int time, DNDEvent event) {
    if (dragContext is null) return false;
    if (dragContext.targets is null) return false;

    // get allowed operations
    int style = getStyle();
    int operations = osOpToOp(dragContext.actions) & style;
    if (operations is DND.DROP_NONE) return false;

    // get current operation
    int operation = getOperationFromKeyState();
    keyOperation = operation;
    if (operation is DND.DROP_DEFAULT) {
        if ((style & DND.DROP_DEFAULT) is 0) {
            operation = (operations & DND.DROP_MOVE) !is 0 ? DND.DROP_MOVE : DND.DROP_NONE;
        }
    } else {
        if ((operation & operations) is 0) operation = DND.DROP_NONE;
    }

    // Get allowed transfer types
    int length = OS.g_list_length(dragContext.targets);
    TransferData[] dataTypes = new TransferData[0];
    for (int i = 0; i < length; i++) {
        auto pData = OS.g_list_nth(dragContext.targets, i);
        GtkTargetPair* gtkTargetPair = cast(GtkTargetPair*)pData;
        TransferData data = new TransferData();
        data.type = gtkTargetPair.target;
        for (int j = 0; j < transferAgents.length; j++) {
            Transfer transfer = transferAgents[j];
            if (transfer !is null && transfer.isSupportedType(data)) {
                TransferData[] newDataTypes = new TransferData[dataTypes.length + 1];
                System.arraycopy(dataTypes, 0, newDataTypes, 0, dataTypes.length);
                newDataTypes[dataTypes.length] = data;
                dataTypes = newDataTypes;
                break;
            }
        }
    }
    if (dataTypes.length is 0) return false;

    auto window = OS.GTK_WIDGET_WINDOW(control.handle);
    int origin_x, origin_y;
    OS.gdk_window_get_origin(window, &origin_x, &origin_y);
    Point coordinates = new Point(origin_x + x, origin_y + y);

    event.widget = this;
    event.x = coordinates.x;
    event.y = coordinates.y;
    event.time = time;
    event.feedback = DND.FEEDBACK_SELECT;
    event.dataTypes = dataTypes;
    event.dataType = dataTypes[0];
    event.operations = operations;
    event.detail = operation;
    if (dropEffect !is null) {
        event.item = dropEffect.getItem(coordinates.x, coordinates.y);
    }
    return true;
}

void updateDragOverHover(long delay, DNDEvent event) {
    if (delay is 0) {
        dragOverStart = 0;
        dragOverEvent = null;
        return;
    }
    dragOverStart = System.currentTimeMillis() + delay;
    if (dragOverEvent is null) dragOverEvent = new DNDEvent();
    dragOverEvent.x = event.x;
    dragOverEvent.y = event.y;
    TransferData[] dataTypes = new TransferData[ event.dataTypes.length];
    System.arraycopy( event.dataTypes, 0, dataTypes, 0, dataTypes.length);
    dragOverEvent.dataTypes  = dataTypes;
    dragOverEvent.operations = event.operations;
    dragOverEvent.time = event.time;
}

}