/*******************************************************************************
 * 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.widgets.Widget;

import org.eclipse.swt.SWT;
import org.eclipse.swt.SWTException;
import org.eclipse.swt.events.DisposeListener;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.GCData;
import org.eclipse.swt.internal.SWTEventListener;
import org.eclipse.swt.internal.win32.OS;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.EventTable;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Menu;
import org.eclipse.swt.widgets.TypedListener;

import java.lang.all;
import java.lang.Thread;

/**
 * This class is the abstract superclass of all user interface objects.
 * Widgets are created, disposed and issue notification to listeners
 * when events occur which affect them.
 * <dl>
 * <dt><b>Styles:</b></dt>
 * <dd>(none)</dd>
 * <dt><b>Events:</b></dt>
 * <dd>Dispose</dd>
 * </dl>
 * <p>
 * IMPORTANT: This class is intended to be subclassed <em>only</em>
 * within the SWT implementation. However, it has not been marked
 * final to allow those outside of the SWT development team to implement
 * patched versions of the class in order to get around specific
 * limitations in advance of when those limitations can be addressed
 * by the team.  Any class built using subclassing to access the internals
 * of this class will likely fail to compile or run between releases and
 * may be strongly platform specific. Subclassing should not be attempted
 * without an intimate and detailed understanding of the workings of the
 * hierarchy. No support is provided for user-written classes which are
 * implemented as subclasses of this class.
 * </p>
 *
 * @see #checkSubclass
 * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>
 */

public abstract class Widget {

    int style, state;
    Display display;
    EventTable eventTable;
    Object data;

    public alias org.eclipse.swt.internal.win32.OS.LDWTRESULT LRESULT;

    /* Global state flags */
    static const int DISPOSED       = 1<<0;
    static const int CANVAS         = 1<<1;
    static const int KEYED_DATA     = 1<<2;
    static const int DISABLED       = 1<<3;
    static const int HIDDEN         = 1<<4;

    /* A layout was requested on this widget */
    static const int LAYOUT_NEEDED  = 1<<5;

    /* The preferred size of a child has changed */
    static const int LAYOUT_CHANGED = 1<<6;

    /* A layout was requested in this widget hierarchy */
    static const int LAYOUT_CHILD = 1<<7;

    /* Background flags */
    static const int THEME_BACKGROUND = 1<<8;
    static const int DRAW_BACKGROUND = 1<<9;
    static const int PARENT_BACKGROUND = 1<<10;

    /* Dispose and release flags */
    static const int RELEASED       = 1<<11;
    static const int DISPOSE_SENT   = 1<<12;

    /* More global widget state flags */
    static const int TRACK_MOUSE    = 1<<13;
    static const int FOREIGN_HANDLE = 1<<14;
    static const int DRAG_DETECT    = 1<<15;

    /* Move and resize state flags */
    static const int MOVE_OCCURRED      = 1<<16;
    static const int MOVE_DEFERRED      = 1<<17;
    static const int RESIZE_OCCURRED    = 1<<18;
    static const int RESIZE_DEFERRED    = 1<<19;

    /* Ignore WM_CHANGEUISTATE */
    static const int IGNORE_WM_CHANGEUISTATE = 1<<20;

    /* Default size for widgets */
    static const int DEFAULT_WIDTH  = 64;
    static const int DEFAULT_HEIGHT = 64;

    /* Check and initialize the Common Controls DLL */
    static const int MAJOR = 5, MINOR = 80;

    private static bool static_this_completed = false;
    private static void static_this() {
        if( static_this_completed ){
            return;
        }
        synchronized {
            if( static_this_completed ){
                return;
            }
            static if (!OS.IsWinCE) {
                if (OS.COMCTL32_VERSION < OS.VERSION (MAJOR, MINOR)) {
                    getDwtLogger().warn ( __FILE__, __LINE__, "***WARNING: SWT requires comctl32.dll version {}.{} or greater", MAJOR, MINOR); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
                    getDwtLogger().warn ( __FILE__, __LINE__, "***WARNING: Detected: {}.{}", OS.COMCTL32_MAJOR, OS.COMCTL32_MINOR); //$NON-NLS-1$ //$NON-NLS-2$
                }
            }
            OS.InitCommonControls ();
            static_this_completed = true;
        }
    }

/**
 * Prevents uninitialized instances from being created outside the package.
 */
this () {
    static_this();
}

/**
 * Constructs a new instance of this class given its parent
 * and a style value describing its behavior and appearance.
 * <p>
 * The style value is either one of the style constants defined in
 * class <code>SWT</code> which is applicable to instances of this
 * class, or must be built by <em>bitwise OR</em>'ing together
 * (that is, using the <code>int</code> "|" operator) two or more
 * of those <code>SWT</code> style constants. The class description
 * lists the style constants that are applicable to the class.
 * Style bits are also inherited from superclasses.
 * </p>
 *
 * @param parent a widget which will be the parent of the new instance (cannot be null)
 * @param style the style of widget to construct
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the parent is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the parent is disposed</li>
 * </ul>
 * @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>
 *
 * @see SWT
 * @see #checkSubclass
 * @see #getStyle
 */
public this (Widget parent, int style) {
    static_this();
    checkSubclass ();
    checkParent (parent);
    this.style = style;
    display = parent.display;
}

void _addListener (int eventType, Listener listener) {
    if (eventTable is null) eventTable = new EventTable ();
    eventTable.hook (eventType, listener);
}

/**
 * Adds the listener to the collection of listeners who will
 * be notified when an event of the given type occurs. When the
 * event does occur in the widget, the listener is notified by
 * sending it the <code>handleEvent()</code> message. The event
 * type is one of the event constants defined in class <code>SWT</code>.
 *
 * @param eventType the type of event to listen for
 * @param listener the listener which should be notified when the event occurs
 *
 * @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 Listener
 * @see SWT
 * @see #getListeners(int)
 * @see #removeListener(int, Listener)
 * @see #notifyListeners
 */
public void addListener (int eventType, Listener listener) {
    checkWidget();
    if (listener is null) error (SWT.ERROR_NULL_ARGUMENT);
    _addListener (eventType, listener);
}

/**
 * Adds the listener to the collection of listeners who will
 * be notified when the widget is disposed. When the widget is
 * disposed, the listener is notified by sending it the
 * <code>widgetDisposed()</code> message.
 *
 * @param listener the listener which should be notified when the receiver is disposed
 *
 * @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 DisposeListener
 * @see #removeDisposeListener
 */
public void addDisposeListener (DisposeListener listener) {
    checkWidget();
    if (listener is null) error (SWT.ERROR_NULL_ARGUMENT);
    TypedListener typedListener = new TypedListener (listener);
    addListener (SWT.Dispose, typedListener);
}

int callWindowProc (HWND hwnd, int msg, int wParam, int lParam) {
    return 0;
}

/**
 * Returns a style with exactly one style bit set out of
 * the specified set of exclusive style bits. All other
 * possible bits are cleared when the first matching bit
 * is found. Bits that are not part of the possible set
 * are untouched.
 *
 * @param style the original style bits
 * @param int0 the 0th possible style bit
 * @param int1 the 1st possible style bit
 * @param int2 the 2nd possible style bit
 * @param int3 the 3rd possible style bit
 * @param int4 the 4th possible style bit
 * @param int5 the 5th possible style bit
 *
 * @return the new style bits
 */
static int checkBits (int style, int int0, int int1, int int2, int int3, int int4, int int5) {
    int mask = int0 | int1 | int2 | int3 | int4 | int5;
    if ((style & mask) is 0) style |= int0;
    if ((style & int0) !is 0) style = (style & ~mask) | int0;
    if ((style & int1) !is 0) style = (style & ~mask) | int1;
    if ((style & int2) !is 0) style = (style & ~mask) | int2;
    if ((style & int3) !is 0) style = (style & ~mask) | int3;
    if ((style & int4) !is 0) style = (style & ~mask) | int4;
    if ((style & int5) !is 0) style = (style & ~mask) | int5;
    return style;
}

void checkOrientation (Widget parent) {
    style &= ~SWT.MIRRORED;
    if ((style & (SWT.LEFT_TO_RIGHT | SWT.RIGHT_TO_LEFT)) is 0) {
        if (parent !is null) {
            if ((parent.style & SWT.LEFT_TO_RIGHT) !is 0) style |= SWT.LEFT_TO_RIGHT;
            if ((parent.style & SWT.RIGHT_TO_LEFT) !is 0) style |= SWT.RIGHT_TO_LEFT;
        }
    }
    style = checkBits (style, SWT.LEFT_TO_RIGHT, SWT.RIGHT_TO_LEFT, 0, 0, 0, 0);
}

void checkOpened () {
    /* Do nothing */
}

/**
 * Throws an exception if the specified widget can not be
 * used as a parent for the receiver.
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the parent is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the parent is disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li>
 * </ul>
 */
void checkParent (Widget parent) {
    if (parent is null) error (SWT.ERROR_NULL_ARGUMENT);
    if (parent.isDisposed ()) error (SWT.ERROR_INVALID_ARGUMENT);
    parent.checkWidget ();
    parent.checkOpened ();
}

/**
 * Checks that this class can be subclassed.
 * <p>
 * The SWT class library is intended to be subclassed
 * only at specific, controlled points (most notably,
 * <code>Composite</code> and <code>Canvas</code> when
 * implementing new widgets). This method enforces this
 * rule unless it is overridden.
 * </p><p>
 * <em>IMPORTANT:</em> By providing an implementation of this
 * method that allows a subclass of a class which does not
 * normally allow subclassing to be created, the implementer
 * agrees to be fully responsible for the fact that any such
 * subclass will likely fail between SWT releases and will be
 * strongly platform specific. No support is provided for
 * user-written classes which are implemented in this fashion.
 * </p><p>
 * The ability to subclass outside of the allowed SWT classes
 * is intended purely to enable those not on the SWT development
 * team to implement patches in order to get around specific
 * limitations in advance of when those limitations can be
 * addressed by the team. Subclassing should not be attempted
 * without an intimate and detailed understanding of the hierarchy.
 * </p>
 *
 * @exception SWTException <ul>
 *    <li>ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass</li>
 * </ul>
 */
protected void checkSubclass () {
    if (!isValidSubclass ()) error (SWT.ERROR_INVALID_SUBCLASS);
}

/**
 * Throws an <code>SWTException</code> if the receiver can not
 * be accessed by the caller. This may include both checks on
 * the state of the receiver and more generally on the entire
 * execution context. This method <em>should</em> be called by
 * widget implementors to enforce the standard SWT invariants.
 * <p>
 * Currently, it is an error to invoke any method (other than
 * <code>isDisposed()</code>) on a widget that has had its
 * <code>dispose()</code> method called. It is also an error
 * to call widget methods from any thread that is different
 * from the thread that created the widget.
 * </p><p>
 * In future releases of SWT, there may be more or fewer error
 * checks and exceptions may be thrown for different reasons.
 * </p>
 *
 * @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>
 */
void checkWidget () {
    Display display = this.display;
    if (display is null) error (SWT.ERROR_WIDGET_DISPOSED);
    if (display.thread !is Thread.currentThread ()) {
        /*
        * Bug in IBM JVM 1.6.  For some reason, under
        * conditions that are yet to be full understood,
        * Thread.currentThread() is either returning null
        * or a different instance from the one that was
        * saved when the Display was created.  This is
        * possibly a JIT problem because modifying this
        * method to print logging information when the
        * error happens seems to fix the problem.  The
        * fix is to use operating system calls to verify
        * that the current thread is not the Display thread.
        *
        * NOTE: Despite the fact that Thread.currentThread()
        * is used in other places, the failure has not been
        * observed in all places where it is called. 
        */
        if (display.threadId !is OS.GetCurrentThreadId ()) {
            error (SWT.ERROR_THREAD_INVALID_ACCESS);
        }
    }
    if ((state & DISPOSED) !is 0) error (SWT.ERROR_WIDGET_DISPOSED);
}

/**
 * Destroys the widget in the operating system and releases
 * the widget's handle.  If the widget does not have a handle,
 * this method may hide the widget, mark the widget as destroyed
 * or do nothing, depending on the widget.
 * <p>
 * When a widget is destroyed in the operating system, its
 * descendants are also destroyed by the operating system.
 * This means that it is only necessary to call <code>destroyWidget</code>
 * on the root of the widget tree.
 * </p><p>
 * This method is called after <code>releaseWidget()</code>.
 * </p><p>
 * See also <code>releaseChild()</code>, <code>releaseWidget()</code>
 * and <code>releaseHandle()</code>.
 * </p>
 *
 * @see #dispose
 */
void destroyWidget () {
    releaseHandle ();
}

HDWP DeferWindowPos(HDWP hWinPosInfo, HWND hWnd, HWND hWndInsertAfter, int X, int Y, int cx, int cy, int uFlags){
    static if (OS.IsWinCE) {
        /*
        * Feature in Windows.  On Windows CE, DeferWindowPos always causes
        * a WM_SIZE message, even when the new size is the same as the old
        * size.  The fix is to detect that the size has not changed and set
        * SWP_NOSIZE.
        */
        if ((uFlags & OS.SWP_NOSIZE) is 0) {
            RECT lpRect;
            OS.GetWindowRect (hWnd, &lpRect);
            if (cy is lpRect.bottom - lpRect.top && cx is lpRect.right - lpRect.left) {
                /*
                * Feature in Windows.  On Windows CE, DeferWindowPos when called
                * with SWP_DRAWFRAME always causes a WM_SIZE message, even
                * when SWP_NOSIZE is set and when the new size is the same as the
                * old size.  The fix is to clear SWP_DRAWFRAME when the size is
                * the same.
                */
                uFlags &= ~OS.SWP_DRAWFRAME;
                uFlags |= OS.SWP_NOSIZE;
            }
        }
    }
    return OS.DeferWindowPos (hWinPosInfo, hWnd, hWndInsertAfter, X, Y, cx, cy, uFlags);
}

/**
 * Disposes of the operating system resources associated with
 * the receiver and all its descendants. After this method has
 * been invoked, the receiver and all descendants will answer
 * <code>true</code> when sent the message <code>isDisposed()</code>.
 * Any internal connections between the widgets in the tree will
 * have been removed to facilitate garbage collection.
 * <p>
 * NOTE: This method is not called recursively on the descendants
 * of the receiver. This means that, widget implementers can not
 * detect when a widget is being disposed of by re-implementing
 * this method, but should instead listen for the <code>Dispose</code>
 * event.
 * </p>
 *
 * @exception SWTException <ul>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see #addDisposeListener
 * @see #removeDisposeListener
 * @see #checkWidget
 */
public void dispose () {
    /*
    * Note:  It is valid to attempt to dispose a widget
    * more than once.  If this happens, fail silently.
    */
    if (isDisposed ()) return;
    if (!isValidThread ()) error (SWT.ERROR_THREAD_INVALID_ACCESS);
    release (true);
}

bool dragDetect (HWND hwnd, int x, int y, bool filter, bool [] detect, bool [] consume) {
    if (consume !is null) consume [0] = false;
    if (detect !is null) detect [0] = true;
    POINT pt;
    pt.x = x;
    pt.y = y;
    OS.ClientToScreen (hwnd, &pt);
    return cast(bool) OS.DragDetect (hwnd, pt);
}

/**
 * Does whatever widget specific cleanup is required, and then
 * uses the code in <code>SWTError.error</code> to handle the error.
 *
 * @param code the descriptive error code
 *
 * @see SWT#error(int)
 */
void error (int code) {
    SWT.error(code);
}

bool filters (int eventType) {
    return display.filters (eventType);
}

Widget findItem (HANDLE id) {
    return null;
}

char [] fixMnemonic (String string) {
    return fixMnemonic (string, false);
}

char [] fixMnemonic (String string, bool spaces) {
    char[] buffer = cast(char[])string ~ '\0';
    int i = 0, j = 0;
    while (i < buffer.length) {
        if (buffer [i] is '&') {
            if (i + 1 < buffer.length && buffer [i + 1] is '&') {
                buffer [j++] = spaces ? ' ' : buffer [i];
                i++;
            }
            i++;
        } else {
            buffer [j++] = buffer [i++];
        }
    }
    if (j < buffer.length) buffer [j++] = 0;
    return buffer[0 .. j];
}

/**
 * Returns the application defined widget data associated
 * with the receiver, or null if it has not been set. The
 * <em>widget data</em> is a single, unnamed field that is
 * stored with every widget.
 * <p>
 * Applications may put arbitrary objects in this field. If
 * the object stored in the widget data needs to be notified
 * when the widget is disposed of, it is the application's
 * responsibility to hook the Dispose event on the widget and
 * do so.
 * </p>
 *
 * @return the widget data
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - when the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - when called from the wrong thread</li>
 * </ul>
 *
 * @see #setData(Object)
 */
public Object getData () {
    checkWidget();
    return (state & KEYED_DATA) !is 0 ? (cast(ArrayWrapperObject) data).array [0] : data;
}
public String getDataStr () {
    return stringcast(getData());
}

/**
 * Returns the application defined property of the receiver
 * with the specified name, or null if it has not been set.
 * <p>
 * Applications may have associated arbitrary objects with the
 * receiver in this fashion. If the objects stored in the
 * properties need to be notified when the widget is disposed
 * of, it is the application's responsibility to hook the
 * Dispose event on the widget and do so.
 * </p>
 *
 * @param   key the name of the property
 * @return the value of the property or null if it has not been set
 *
 * @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 #setData(String, Object)
 */
public Object getData (String key) {
    checkWidget();
    // SWT extension: allow null key
    //if (key is null) error (SWT.ERROR_NULL_ARGUMENT);
    if ((state & KEYED_DATA) !is 0) {
        Object [] table = (cast(ArrayWrapperObject) data).array;
        for (int i=1; i<table.length; i+=2) {
            auto tablekey = (cast(ArrayWrapperString) table[i]).array;
            if (key ==/*eq*/ tablekey ) return table [i+1];
        }
    }
    return null;
}
public String getDataStr (String key) {
    return stringcast(getData(key));
}

/**
 * Returns the <code>Display</code> that is associated with
 * the receiver.
 * <p>
 * A widget's display is either provided when it is created
 * (for example, top level <code>Shell</code>s) or is the
 * same as its parent's display.
 * </p>
 *
 * @return the receiver's display
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 * </ul>
 */
public Display getDisplay () {
    Display display = this.display;
    if (display is null) error (SWT.ERROR_WIDGET_DISPOSED);
    return display;
}

/**
 * Returns an array of listeners who will be notified when an event
 * of the given type occurs. The event type is one of the event constants
 * defined in class <code>SWT</code>.
 *
 * @param eventType the type of event to listen for
 * @return an array of listeners that will be notified when the event occurs
 *
 * @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 Listener
 * @see SWT
 * @see #addListener(int, Listener)
 * @see #removeListener(int, Listener)
 * @see #notifyListeners
 *
 * @since 3.4
 */
public Listener[] getListeners (int eventType) {
    checkWidget();
    if (eventTable is null) return new Listener[0];
    return eventTable.getListeners(eventType);
}

Menu getMenu () {
    return null;
}

/**
 * Returns the name of the widget. This is the name of
 * the class without the package name.
 *
 * @return the name of the widget
 */
String getName () {
    String str = this.classinfo.name;
    int index = str.length;
    while ((--index > 0) && (str[index] !is '.')) {}
    return str[index + 1 .. $ ];
}

/*
 * Returns a short printable representation for the contents
 * of a widget. For example, a button may answer the label
 * text. This is used by <code>toString</code> to provide a
 * more meaningful description of the widget.
 *
 * @return the contents string for the widget
 *
 * @see #toString
 */
String getNameText () {
    return ""; //$NON-NLS-1$
}

/**
 * Returns the receiver's style information.
 * <p>
 * Note that the value which is returned by this method <em>may
 * not match</em> the value which was provided to the constructor
 * when the receiver was created. This can occur when the underlying
 * operating system does not support a particular combination of
 * requested styles. For example, if the platform widget used to
 * implement a particular SWT widget always has scroll bars, the
 * result of calling this method would always have the
 * <code>SWT.H_SCROLL</code> and <code>SWT.V_SCROLL</code> bits set.
 * </p>
 *
 * @return the style bits
 *
 * @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>
 */
public int getStyle () {
    checkWidget();
    return style;
}

/*
 * Returns <code>true</code> if the specified eventType is
 * hooked, and <code>false</code> otherwise. Implementations
 * of SWT can avoid creating objects and sending events
 * when an event happens in the operating system but
 * there are no listeners hooked for the event.
 *
 * @param eventType the event to be checked
 *
 * @return <code>true</code> when the eventType is hooked and <code>false</code> otherwise
 *
 * @see #isListening
 */
bool hooks (int eventType) {
    if (eventTable is null) return false;
    return eventTable.hooks (eventType);
}

/**
 * Returns <code>true</code> if the widget has been disposed,
 * and <code>false</code> otherwise.
 * <p>
 * This method gets the dispose state for the widget.
 * When a widget has been disposed, it is an error to
 * invoke any other method using the widget.
 * </p>
 *
 * @return <code>true</code> when the widget is disposed and <code>false</code> otherwise
 */
public bool isDisposed () {
    return (state & DISPOSED) !is 0;
}

/**
 * Returns <code>true</code> if there are any listeners
 * for the specified event type associated with the receiver,
 * and <code>false</code> otherwise. The event type is one of
 * the event constants defined in class <code>SWT</code>.
 *
 * @param eventType the type of event
 * @return true if the event is hooked
 *
 * @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 SWT
 */
public bool isListening (int eventType) {
    checkWidget();
    return hooks (eventType);
}

/*
 * Returns <code>true</code> when subclassing is
 * allowed and <code>false</code> otherwise
 *
 * @return <code>true</code> when subclassing is allowed and <code>false</code> otherwise
 */
bool isValidSubclass () {
    return true;//Display.isValidClass (getClass ());
}

/*
 * Returns <code>true</code> when the current thread is
 * the thread that created the widget and <code>false</code>
 * otherwise.
 *
 * @return <code>true</code> when the current thread is the thread that created the widget and <code>false</code> otherwise
 */
bool isValidThread () {
    return getDisplay ().isValidThread ();
}

void mapEvent (HWND hwnd, Event event) {
}

GC new_GC (GCData data) {
    return null;
}

/**
 * Notifies all of the receiver's listeners for events
 * of the given type that one such event has occurred by
 * invoking their <code>handleEvent()</code> method.  The
 * event type is one of the event constants defined in class
 * <code>SWT</code>.
 *
 * @param eventType the type of event which has occurred
 * @param event the event data
 *
 * @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 SWT
 * @see #addListener
 * @see #getListeners(int)
 * @see #removeListener(int, Listener)
 */
public void notifyListeners (int eventType, Event event) {
    checkWidget();
    if (event is null) event = new Event ();
    sendEvent (eventType, event);
}

void postEvent (int eventType) {
    sendEvent (eventType, null, false);
}

void postEvent (int eventType, Event event) {
    sendEvent (eventType, event, false);
}

/*
 * Releases the widget hierarchy and optionally destroys
 * the receiver.
 * <p>
 * Typically, a widget with children will broadcast this
 * message to all children so that they too can release their
 * resources.  The <code>releaseHandle</code> method is used
 * as part of this broadcast to zero the handle fields of the
 * children without calling <code>destroyWidget</code>.  In
 * this scenario, the children are actually destroyed later,
 * when the operating system destroys the widget tree.
 * </p>
 *
 * @param destroy indicates that the receiver should be destroyed
 *
 * @see #dispose
 * @see #releaseHandle
 * @see #releaseParent
 * @see #releaseWidget
*/
void release (bool destroy) {
    if ((state & DISPOSE_SENT) is 0) {
        state |= DISPOSE_SENT;
        sendEvent (SWT.Dispose);
    }
    if ((state & DISPOSED) is 0) {
        releaseChildren (destroy);
    }
    if ((state & RELEASED) is 0) {
        state |= RELEASED;
        if (destroy) {
            releaseParent ();
            releaseWidget ();
            destroyWidget ();
        } else {
            releaseWidget ();
            releaseHandle ();
        }
    }
}

void releaseChildren (bool destroy) {
}

/*
 * Releases the widget's handle by zero'ing it out.
 * Does not destroy or release any operating system
 * resources.
 * <p>
 * This method is called after <code>releaseWidget</code>
 * or from <code>destroyWidget</code> when a widget is being
 * destroyed to ensure that the widget is marked as destroyed
 * in case the act of destroying the widget in the operating
 * system causes application code to run in callback that
 * could access the widget.
 * </p>
 *
 * @see #dispose
 * @see #releaseChildren
 * @see #releaseParent
 * @see #releaseWidget
 */
void releaseHandle () {
    state |= DISPOSED;
    display = null;
}

/*
 * Releases the receiver, a child in a widget hierarchy,
 * from its parent.
 * <p>
 * When a widget is destroyed, it may be necessary to remove
 * it from an internal data structure of the parent. When
 * a widget has no handle, it may also be necessary for the
 * parent to hide the widget or otherwise indicate that the
 * widget has been disposed. For example, disposing a menu
 * bar requires that the menu bar first be released from the
 * shell when the menu bar is active.
 * </p>
 *
 * @see #dispose
 * @see #releaseChildren
 * @see #releaseWidget
 * @see #releaseHandle
 */
void releaseParent () {
}

/*
 * Releases any internal resources back to the operating
 * system and clears all fields except the widget handle.
 * <p>
 * When a widget is destroyed, resources that were acquired
 * on behalf of the programmer need to be returned to the
 * operating system.  For example, if the widget made a
 * copy of an icon, supplied by the programmer, this copy
 * would be freed in <code>releaseWidget</code>.  Also,
 * to assist the garbage collector and minimize the amount
 * of memory that is not reclaimed when the programmer keeps
 * a reference to a disposed widget, all fields except the
 * handle are zero'd.  The handle is needed by <code>destroyWidget</code>.
 * </p>
 *
 * @see #dispose
 * @see #releaseChildren
 * @see #releaseHandle
 * @see #releaseParent
 */
void releaseWidget () {
    eventTable = null;
    data = null;
}

/**
 * Removes the listener from the collection of listeners who will
 * be notified when an event of the given type occurs. The event
 * type is one of the event constants defined in class <code>SWT</code>.
 *
 * @param eventType the type of event to listen for
 * @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 Listener
 * @see SWT
 * @see #addListener
 * @see #getListeners(int)
 * @see #notifyListeners
 */
public void removeListener (int eventType, Listener listener) {
    checkWidget();
    if (listener is null) error (SWT.ERROR_NULL_ARGUMENT);
    if (eventTable is null) return;
    eventTable.unhook (eventType, listener);
}

/**
 * Removes the listener from the collection of listeners who will
 * be notified when an event of the given type occurs.
 * <p>
 * <b>IMPORTANT:</b> This method is <em>not</em> part of the SWT
 * public API. It is marked public only so that it can be shared
 * within the packages provided by SWT. It should never be
 * referenced from application code.
 * </p>
 *
 * @param eventType the type of event to listen for
 * @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 Listener
 * @see #addListener
 */
protected void removeListener (int eventType, SWTEventListener listener) {
    checkWidget();
    if (listener is null) error (SWT.ERROR_NULL_ARGUMENT);
    if (eventTable is null) return;
    eventTable.unhook (eventType, listener);
}

/**
 * Removes the listener from the collection of listeners who will
 * be notified when the widget is disposed.
 *
 * @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 DisposeListener
 * @see #addDisposeListener
 */
public void removeDisposeListener (DisposeListener listener) {
    checkWidget();
    if (listener is null) error (SWT.ERROR_NULL_ARGUMENT);
    if (eventTable is null) return;
    eventTable.unhook (SWT.Dispose, listener);
}

bool sendDragEvent (int button, int x, int y) {
    Event event = new Event ();
    event.button = button;
    event.x = x;
    event.y = y;
    setInputState (event, SWT.DragDetect);
    postEvent (SWT.DragDetect, event);
    if (isDisposed ()) return false;
    return event.doit;
}

bool sendDragEvent (int button, int stateMask, int x, int y) {
    Event event = new Event ();
    event.button = button;
    event.x = x;
    event.y = y;
    event.stateMask = stateMask;
    postEvent (SWT.DragDetect, event);
    if (isDisposed ()) return false;
    return event.doit;
}

void sendEvent (Event event) {
    Display display = event.display;
    if (!display.filterEvent (event)) {
        if (eventTable !is null) eventTable.sendEvent (event);
    }
}

void sendEvent (int eventType) {
    sendEvent (eventType, null, true);
}

void sendEvent (int eventType, Event event) {
    sendEvent (eventType, event, true);
}

void sendEvent (int eventType, Event event, bool send) {
    if (eventTable is null && !display.filters (eventType)) {
        return;
    }
    if (event is null) event = new Event ();
    event.type = eventType;
    event.display = display;
    event.widget = this;
    if (event.time is 0) {
        event.time = display.getLastEventTime ();
    }
    if (send) {
        sendEvent (event);
    } else {
        display.postEvent (event);
    }
}

bool sendKeyEvent (int type, int msg, int /*long*/ wParam, int /*long*/ lParam) {
    Event event = new Event ();
    if (!setKeyState (event, type, wParam, lParam)) return true;
    return sendKeyEvent (type, msg, wParam, lParam, event);
}

bool sendKeyEvent (int type, int msg, int /*long*/ wParam, int /*long*/ lParam, Event event) {
    sendEvent (type, event);
    if (isDisposed ()) return false;
    return event.doit;
}

bool sendMouseEvent (int type, int button, HWND hwnd, int msg, int wParam, int lParam) {
    return sendMouseEvent (type, button, display.getClickCount (type, button, hwnd, lParam), 0, false, hwnd, msg, wParam, lParam);
}

bool sendMouseEvent (int type, int button, int count, int detail, bool send, HWND hwnd, int msg, int wParam, int lParam) {
    if (!hooks (type) && !filters (type)) return true;
    Event event = new Event ();
    event.button = button;
    event.detail = detail;
    event.count = count;
    event.x = OS.GET_X_LPARAM (lParam);
    event.y = OS.GET_Y_LPARAM (lParam);
    setInputState (event, type);
    mapEvent (hwnd, event);
    if (send) {
        sendEvent (type, event);
        if (isDisposed ()) return false;
    } else {
        postEvent (type, event);
    }
    return event.doit;
}

/**
 * Sets the application defined widget data associated
 * with the receiver to be the argument. The <em>widget
 * data</em> is a single, unnamed field that is stored
 * with every widget.
 * <p>
 * Applications may put arbitrary objects in this field. If
 * the object stored in the widget data needs to be notified
 * when the widget is disposed of, it is the application's
 * responsibility to hook the Dispose event on the widget and
 * do so.
 * </p>
 *
 * @param data the widget data
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - when the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - when called from the wrong thread</li>
 * </ul>
 *
 * @see #getData()
 */
public void setData (Object data) {
    checkWidget();
    if ((state & KEYED_DATA) !is 0) {
        (cast(ArrayWrapperObject) this.data).array [0] = data;
    } else {
        this.data = data;
    }
}
/// SWT extension
public void setDataStr (String data) {
    setData(stringcast(data));
}

/**
 * Sets the application defined property of the receiver
 * with the specified name to the given value.
 * <p>
 * Applications may associate arbitrary objects with the
 * receiver in this fashion. If the objects stored in the
 * properties need to be notified when the widget is disposed
 * of, it is the application's responsibility to hook the
 * Dispose event on the widget and do so.
 * </p>
 *
 * @param key the name of the property
 * @param value the new value for the property
 *
 * @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 #getData(String)
 */
public void setData (String key, Object value) {
    checkWidget();
    // SWT extension: allow null key
    //if (key.length is 0) error (SWT.ERROR_NULL_ARGUMENT);
    int index = 1;
    Object [] table = null;
    if ((state & KEYED_DATA) !is 0) {
        table = (cast(ArrayWrapperObject) data).array;
        while (index < table.length) {
            auto tablekey = (cast(ArrayWrapperString)table[index]).array;
            if (key ==/*eq*/ tablekey ) break;
            index += 2;
        }
    }
    if (value !is null) {
        if ((state & KEYED_DATA) !is 0) {
            if (index is table.length) {
                Object [] newTable = new Object [table.length + 2];
                System.arraycopy (table, 0, newTable, 0, table.length);
                table = newTable;
                data = new ArrayWrapperObject( table );
            }
        } else {
            table = new Object [3];
            table [0] = data;
            data = new ArrayWrapperObject( table );
            state |= KEYED_DATA;
        }
        table [index] = new ArrayWrapperString( cast(char[])key );
        table [index + 1] = value;
    } else {
        if ((state & KEYED_DATA) !is 0) {
            if (index !is table.length) {
                int len = table.length - 2;
                if (len is 1) {
                    data = table [0];
                    state &= ~KEYED_DATA;
                } else {
                    Object [] newTable = new Object [len];
                    System.arraycopy (table, 0, newTable, 0, index);
                    System.arraycopy (table, index + 2, newTable, index, len - index);
                    data = new ArrayWrapperObject( newTable );
                }
            }
        }
    }
}
/// SWT extension
public void setDataStr (String key, String value) {
    setData( key, stringcast(value));
}

bool sendFocusEvent (int type) {
    sendEvent (type);
    // widget could be disposed at this point
    return true;
}

bool setInputState (Event event, int type) {
    if (OS.GetKeyState (OS.VK_MENU) < 0) event.stateMask |= SWT.ALT;
    if (OS.GetKeyState (OS.VK_SHIFT) < 0) event.stateMask |= SWT.SHIFT;
    if (OS.GetKeyState (OS.VK_CONTROL) < 0) event.stateMask |= SWT.CONTROL;
    if (OS.GetKeyState (OS.VK_LBUTTON) < 0) event.stateMask |= SWT.BUTTON1;
    if (OS.GetKeyState (OS.VK_MBUTTON) < 0) event.stateMask |= SWT.BUTTON2;
    if (OS.GetKeyState (OS.VK_RBUTTON) < 0) event.stateMask |= SWT.BUTTON3;
    if (display.xMouse) {
        if (OS.GetKeyState (OS.VK_XBUTTON1) < 0) event.stateMask |= SWT.BUTTON4;
        if (OS.GetKeyState (OS.VK_XBUTTON2) < 0) event.stateMask |= SWT.BUTTON5;
    }
    switch (type) {
        case SWT.MouseDown:
        case SWT.MouseDoubleClick:
            if (event.button is 1) event.stateMask &= ~SWT.BUTTON1;
            if (event.button is 2) event.stateMask &= ~SWT.BUTTON2;
            if (event.button is 3) event.stateMask &= ~SWT.BUTTON3;
            if (event.button is 4) event.stateMask &= ~SWT.BUTTON4;
            if (event.button is 5) event.stateMask &= ~SWT.BUTTON5;
            break;
        case SWT.MouseUp:
            if (event.button is 1) event.stateMask |= SWT.BUTTON1;
            if (event.button is 2) event.stateMask |= SWT.BUTTON2;
            if (event.button is 3) event.stateMask |= SWT.BUTTON3;
            if (event.button is 4) event.stateMask |= SWT.BUTTON4;
            if (event.button is 5) event.stateMask |= SWT.BUTTON5;
            break;
        case SWT.KeyDown:
        case SWT.Traverse:
            if (event.keyCode is SWT.ALT) event.stateMask &= ~SWT.ALT;
            if (event.keyCode is SWT.SHIFT) event.stateMask &= ~SWT.SHIFT;
            if (event.keyCode is SWT.CONTROL) event.stateMask &= ~SWT.CONTROL;
            break;
        case SWT.KeyUp:
            if (event.keyCode is SWT.ALT) event.stateMask |= SWT.ALT;
            if (event.keyCode is SWT.SHIFT) event.stateMask |= SWT.SHIFT;
            if (event.keyCode is SWT.CONTROL) event.stateMask |= SWT.CONTROL;
            break;
        default:
    }
    return true;
}

bool setKeyState (Event event, int type, int /*long*/ wParam, int /*long*/ lParam) {

    /*
    * Feature in Windows.  When the user presses Ctrl+Backspace
    * or Ctrl+Enter, Windows sends a WM_CHAR with Delete (0x7F)
    * and '\n' instead of '\b' and '\r'.  This is the correct
    * platform behavior but is not portable.  The fix is to detect
    * these cases and convert the character.
    */
    switch (display.lastAscii) {
        case SWT.DEL:
            if (display.lastKey is SWT.BS) display.lastAscii = SWT.BS;
            break;
        case SWT.LF:
            if (display.lastKey is SWT.CR) display.lastAscii = SWT.CR;
            break;
        default:
    }

    /*
    * Feature in Windows.  When the user presses either the Enter
    * key or the numeric keypad Enter key, Windows sends a WM_KEYDOWN
    * with wParam=VK_RETURN in both cases.  In order to distinguish
    * between the keys, the extended key bit is tested. If the bit
    * is set, assume that the numeric keypad Enter was pressed.
    */
    if (display.lastKey is SWT.CR && display.lastAscii is SWT.CR) {
        if ((lParam & 0x1000000) !is 0) display.lastKey = SWT.KEYPAD_CR;
    }

    if (display.lastVirtual) {
        /*
        * Feature in Windows.  The virtual key VK_DELETE is not
        * treated as both a virtual key and an ASCII key by Windows.
        * Therefore, we will not receive a WM_CHAR for this key.
        * The fix is to treat VK_DELETE as a special case and map
        * the ASCII value explicitly (Delete is 0x7F).
        */
        if (display.lastKey is OS.VK_DELETE) display.lastAscii = 0x7F;

        /*
        * Feature in Windows.  When the user presses Ctrl+Pause, the
        * VK_CANCEL key is generated and a WM_CHAR is sent with 0x03,
        * possibly to allow an application to look for Ctrl+C and the
        * the Break key at the same time.  This is unexpected and
        * unwanted.  The fix is to detect the case and set the character
        * to zero.
        */
        if (display.lastKey is OS.VK_CANCEL) display.lastAscii = 0x0;

        event.keyCode = Display.translateKey (display.lastKey);
    } else {
        event.keyCode = display.lastKey;
    }
    if (display.lastAscii !is 0 || display.lastNull) {
        event.character = Display.mbcsToWcs (cast(wchar) display.lastAscii);
    }
    if (event.keyCode is 0 && event.character is 0) {
        if (!display.lastNull) return false;
    }
    return setInputState (event, type);
}

bool SetWindowPos (HWND hWnd, HWND hWndInsertAfter, int X, int Y, int cx, int cy, int uFlags) {
    static if (OS.IsWinCE) {
        /*
        * Feature in Windows.  On Windows CE, SetWindowPos() always causes
        * a WM_SIZE message, even when the new size is the same as the old
        * size.  The fix is to detect that the size has not changed and set
        * SWP_NOSIZE.
        */
        if ((uFlags & OS.SWP_NOSIZE) is 0) {
            RECT lpRect;
            OS.GetWindowRect (hWnd, &lpRect);
            if (cy is lpRect.bottom - lpRect.top && cx is lpRect.right - lpRect.left) {
                /*
                * Feature in Windows.  On Windows CE, SetWindowPos() when called
                * with SWP_DRAWFRAME always causes a WM_SIZE message, even
                * when SWP_NOSIZE is set and when the new size is the same as the
                * old size.  The fix is to clear SWP_DRAWFRAME when the size is
                * the same.
                */
                uFlags &= ~OS.SWP_DRAWFRAME;
                uFlags |= OS.SWP_NOSIZE;
            }
        }
    }
    return cast(bool) OS.SetWindowPos (hWnd, hWndInsertAfter, X, Y, cx, cy, uFlags);
}

bool showMenu (int x, int y) {
    Event event = new Event ();
    event.x = x;
    event.y = y;
    sendEvent (SWT.MenuDetect, event);
    if (!event.doit) return true;
    Menu menu = getMenu ();
    if (menu !is null && !menu.isDisposed ()) {
        if (x !is event.x || y !is event.y) {
            menu.setLocation (event.x, event.y);
        }
        menu.setVisible (true);
        return true;
    }
    return false;
}

/**
 * Returns a string containing a concise, human-readable
 * description of the receiver.
 *
 * @return a string representation of the receiver
 */
override public String toString () {
    String string = "*Disposed*"; //$NON-NLS-1$
    if (!isDisposed ()) {
        string = "*Wrong Thread*"; //$NON-NLS-1$
        if (isValidThread ()) string = getNameText ();
    }
    return Format( "{} {{{}}", getName (), string ); //$NON-NLS-1$ //$NON-NLS-2$
}

LRESULT wmCaptureChanged (HWND hwnd, int wParam, int lParam) {
    display.captureChanged = true;
    return null;
}

LRESULT wmChar (HWND hwnd, int wParam, int lParam) {
    /*
    * Do not report a lead byte as a key pressed.
    */
    if (!OS.IsUnicode && OS.IsDBLocale) {
        byte lead = cast(byte) (wParam & 0xFF);
        if (OS.IsDBCSLeadByte (lead)) return null;
    }
    display.lastAscii = wParam;
    display.lastNull = wParam is 0;
    if (!sendKeyEvent (SWT.KeyDown, OS.WM_CHAR, wParam, lParam)) {
        return LRESULT.ONE;
    }
    // widget could be disposed at this point
    return null;
}

LRESULT wmContextMenu (HWND hwnd, int wParam, int lParam) {
    if (wParam !is cast(int)hwnd) return null;

    /*
    * Feature in Windows.  SHRecognizeGesture() sends an undocumented
    * WM_CONTEXTMENU notification when the flag SHRG_NOTIFY_PARENT is
    * not set.  This causes the context menu to be displayed twice,
    * once by the caller of SHRecognizeGesture() and once from this
    * method.  The fix is to ignore WM_CONTEXTMENU notifications on
    * all WinCE platforms.
    *
    * NOTE: This only happens on WM2003.  Previous WinCE versions did
    * not support WM_CONTEXTMENU.
    */
    static if (OS.IsWinCE) return null;

    /*
    * Feature in Windows.  When the user presses  WM_NCRBUTTONUP,
    * a WM_CONTEXTMENU message is generated.  This happens when
    * the user releases the mouse over a scroll bar.  Normally,
    * window displays the default scrolling menu but applications
    * can process WM_CONTEXTMENU to display a different menu.
    * Typically, an application does not want to supply a special
    * scroll menu.  The fix is to look for a WM_CONTEXTMENU that
    * originated from a mouse event and display the menu when the
    * mouse was released in the client area.
    */
    int x = 0, y = 0;
    if (lParam !is -1) {
        POINT pt;
        OS.POINTSTOPOINT (pt, lParam);
        x = pt.x;
        y = pt.y;
        OS.ScreenToClient (hwnd, &pt);
        RECT rect;
        OS.GetClientRect (hwnd, &rect);
        if (!OS.PtInRect (&rect, pt)) return null;
    } else {
        int pos = OS.GetMessagePos ();
        x = OS.GET_X_LPARAM (pos);
        y = OS.GET_Y_LPARAM (pos);
    }

    /* Show the menu */
    return showMenu (x, y) ? LRESULT.ZERO : null;
}

LRESULT wmIMEChar (HWND hwnd, int wParam, int lParam) {
    Display display = this.display;
    display.lastKey = 0;
    display.lastAscii = wParam;
    display.lastVirtual = display.lastNull = display.lastDead = false;
    if (!sendKeyEvent (SWT.KeyDown, OS.WM_IME_CHAR, wParam, lParam)) {
        return LRESULT.ONE;
    }
    sendKeyEvent (SWT.KeyUp, OS.WM_IME_CHAR, wParam, lParam);
    // widget could be disposed at this point
    display.lastKey = display.lastAscii = 0;
    return LRESULT.ONE;
}

LRESULT wmKeyDown (HWND hwnd, int wParam, int lParam) {

    /* Ignore repeating modifier keys by testing key down state */
    switch (wParam) {
        case OS.VK_SHIFT:
        case OS.VK_MENU:
        case OS.VK_CONTROL:
        case OS.VK_CAPITAL:
        case OS.VK_NUMLOCK:
        case OS.VK_SCROLL:
            if ((lParam & 0x40000000) !is 0) return null;
        default:
    }

    /* Clear last key and last ascii because a new key has been typed */
    display.lastAscii = display.lastKey = 0;
    display.lastVirtual = display.lastNull = display.lastDead = false;

    /*
    * Do not report a lead byte as a key pressed.
    */
    if (!OS.IsUnicode && OS.IsDBLocale) {
        byte lead = cast(byte) (wParam & 0xFF);
        if (OS.IsDBCSLeadByte (lead)) return null;
    }

    /* Map the virtual key */
    /*
    * Bug in WinCE.  MapVirtualKey() returns incorrect values.
    * The fix is to rely on a key mappings table to determine
    * whether the key event must be sent now or if a WM_CHAR
    * event will follow.  The key mappings table maps virtual
    * keys to SWT key codes and does not contain mappings for
    * Windows virtual keys like VK_A.  Virtual keys that are
    * both virtual and ASCII are a special case.
    */
    int mapKey = 0;
    static if (OS.IsWinCE) {
        switch (wParam) {
            case OS.VK_BACK: mapKey = SWT.BS; break;
            case OS.VK_RETURN: mapKey = SWT.CR; break;
            case OS.VK_DELETE: mapKey = SWT.DEL; break;
            case OS.VK_ESCAPE: mapKey = SWT.ESC; break;
            case OS.VK_TAB: mapKey = SWT.TAB; break;
            default:
        }
    } else {
        /*
        * Feature in Windows.  For numbers in Marathi and Bengali,
        * MapVirtualKey() returns the localized number instead of
        * the ASCII equivalent.  For example, MapVirtualKey()
        * maps VK_1 on the Marathi keyboard to \u2407, which is
        * a valid Unicode Marathi '1' character, but not ASCII.
        * The fix is to test for VK_0 to VK_9 and map these
        * explicitly.
        *
        * NOTE: VK_0 to VK_9 are the same as ASCII.
        */
        if ('0' <= wParam && wParam <= '9') {
            mapKey = wParam;
        } else {
            mapKey = OS.MapVirtualKey (wParam, 2);
        }
    }

    /*
    * Bug in Windows 95 and NT.  When the user types an accent key such
    * as ^ to get an accented character on a German keyboard, the accent
    * key should be ignored and the next key that the user types is the
    * accented key.  The fix is to detect the accent key stroke (called
    * a dead key) by testing the high bit of the value returned by
    * MapVirtualKey().  A further problem is that the high bit on
    * Windows NT is bit 32 while the high bit on Windows 95 is bit 16.
    * They should both be bit 32.
    *
    * When the user types an accent key that does not correspond to a
    * virtual key, MapVirtualKey() won't set the high bit to indicate
    * a dead key.  This happens when an accent key, such as '^' is the
    * result of a modifier such as Shift key and MapVirtualKey() always
    * returns the unshifted key.  The fix is to peek for a WM_DEADCHAR
    * and avoid issuing the event.
    */
    if (OS.IsWinNT) {
        if ((mapKey & 0x80000000) !is 0) return null;
    } else {
        if ((mapKey & 0x8000) !is 0) return null;
    }
    MSG msg;
    int flags = OS.PM_NOREMOVE | OS.PM_NOYIELD | OS.PM_QS_INPUT | OS.PM_QS_POSTMESSAGE;
    if (OS.PeekMessage (&msg, hwnd, OS.WM_DEADCHAR, OS.WM_DEADCHAR, flags)) {
        display.lastDead = true;
        display.lastVirtual = mapKey is 0;
        display.lastKey = display.lastVirtual ? wParam : mapKey;
        return null;
    }

    /*
    *  Bug in Windows.  Somehow, the widget is becoming disposed after
    *  calling PeekMessage().  In rare circumstances, it seems that
    *  PeekMessage() can allow SWT listeners to run that might contain
    *  application code that disposes the widget.  It is not exactly
    *  clear how this can happen.  PeekMessage() is only looking for
    *  WM_DEADCHAR.  It is not dispatching any message that it finds
    *  or removing any message from the queue.  Cross-thread messages
    *  are disabled.  The fix is to check for a disposed widget and
    *  return without calling the window proc.
    */
    if (isDisposed ()) return LRESULT.ONE;

    /*
    * If we are going to get a WM_CHAR, ensure that last key has
    * the correct character value for the key down and key up
    * events.  It is not sufficient to ignore the WM_KEYDOWN
    * (when we know we are going to get a WM_CHAR) and compute
    * the key in WM_CHAR because there is not enough information
    * by the time we get the WM_CHAR.  For example, when the user
    * types Ctrl+Shift+6 on a US keyboard, we get a WM_CHAR with
    * wParam=30.  When the user types Ctrl+Shift+6 on a German
    * keyboard, we also get a WM_CHAR with wParam=30.  On the US
    * keyboard Shift+6 is ^, on the German keyboard Shift+6 is &.
    * There is no way to map wParam=30 in WM_CHAR to the correct
    * value.  Also, on international keyboards, the control key
    * may be down when the user has not entered a control character.
    *
    * NOTE: On Windows 98, keypad keys are virtual despite the
    * fact that a WM_CHAR is issued.  On Windows 2000 and XP,
    * they are not virtual.  Therefore it is necessary to force
    * numeric keypad keys to be virtual.
    */
    display.lastVirtual = mapKey is 0 || display.numpadKey (wParam) !is 0;
    if (display.lastVirtual) {
        display.lastKey = wParam;
        /*
        * Feature in Windows.  The virtual key VK_DELETE is not
        * treated as both a virtual key and an ASCII key by Windows.
        * Therefore, we will not receive a WM_CHAR for this key.
        * The fix is to treat VK_DELETE as a special case and map
        * the ASCII value explicitly (Delete is 0x7F).
        */
        if (display.lastKey is OS.VK_DELETE) display.lastAscii = 0x7F;

        /*
        * It is possible to get a WM_CHAR for a virtual key when
        * Num Lock is on.  If the user types Home while Num Lock
        * is down, a WM_CHAR is issued with WPARM=55 (for the
        * character 7).  If we are going to get a WM_CHAR we need
        * to ensure that the last key has the correct value.  Note
        * that Ctrl+Home does not issue a WM_CHAR when Num Lock is
        * down.
        */
        if (OS.VK_NUMPAD0 <= display.lastKey && display.lastKey <= OS.VK_DIVIDE) {
            /*
            * Feature in Windows.  Calling to ToAscii() or ToUnicode(), clears
            * the accented state such that the next WM_CHAR loses the accent.
            * This makes is critical that the accent key is detected.  Also,
            * these functions clear the character that is entered using the
            * special Windows keypad sequence when NumLock is down (ie. typing
            * ALT+0231 should gives 'c' with a cedilla when NumLock is down).
            */
            if (display.asciiKey (display.lastKey) !is 0) return null;
            display.lastAscii = display.numpadKey (display.lastKey);
        }
    } else {
        /*
        * Convert LastKey to lower case because Windows non-virtual
        * keys that are also ASCII keys, such as like VK_A, are have
        * upper case values in WM_KEYDOWN despite the fact that the
        * Shift was not pressed.
        */
        display.lastKey = cast(int) OS.CharLower (cast(wchar*) mapKey);

        /*
        * Feature in Windows. The virtual key VK_CANCEL is treated
        * as both a virtual key and ASCII key by Windows.  This
        * means that a WM_CHAR with WPARAM=3 will be issued for
        * this key.  In order to distinguish between this key and
        * Ctrl+C, mark the key as virtual.
        */
        if (wParam is OS.VK_CANCEL) display.lastVirtual = true;

        /*
        * Some key combinations map to Windows ASCII keys depending
        * on the keyboard.  For example, Ctrl+Alt+Q maps to @ on a
        * German keyboard.  If the current key combination is special,
        * the correct character is placed in wParam for processing in
        * WM_CHAR.  If this is the case, issue the key down event from
        * inside WM_CHAR.
        */
        dchar asciiKey = display.asciiKey (wParam);
        if (asciiKey !is 0) {
            /*
            * When the user types Ctrl+Space, ToAscii () maps this to
            * Space.  Normally, ToAscii () maps a key to a different
            * key if both a WM_KEYDOWN and a WM_CHAR will be issued.
            * To avoid the extra SWT.KeyDown, look for a space and
            * issue the event from WM_CHAR.
            */
            if (asciiKey is ' ') return null;
            if (asciiKey !is wParam) return null;
            /*
            * Feature in Windows. The virtual key VK_CANCEL is treated
            * as both a virtual key and ASCII key by Windows.  This
            * means that a WM_CHAR with WPARAM=3 will be issued for
            * this key. To avoid the extra SWT.KeyDown, look for
            * VK_CANCEL and issue the event from WM_CHAR.
            */
            if (wParam is OS.VK_CANCEL) return null;
        }

        /*
        * If the control key is not down at this point, then
        * the key that was pressed was an accent key or a regular
        * key such as 'A' or Shift+A.  In that case, issue the
        * key event from WM_CHAR.
        */
        if (OS.GetKeyState (OS.VK_CONTROL) >= 0) return null;

        /*
        * Get the shifted state or convert to lower case if necessary.
        * If the user types Ctrl+A, LastAscii should be 'a', not 'A'.
        * If the user types Ctrl+Shift+A, LastAscii should be 'A'.
        * If the user types Ctrl+Shift+6, the value of LastAscii will
        * depend on the international keyboard.
        */
        if (OS.GetKeyState (OS.VK_SHIFT) < 0) {
            display.lastAscii = display.shiftedKey (wParam);
            if (display.lastAscii is 0) display.lastAscii = mapKey;
        } else {
            display.lastAscii = cast(int)OS.CharLower (cast(wchar*) mapKey);
        }

        /* Note that Ctrl+'@' is ASCII NUL and is delivered in WM_CHAR */
        if (display.lastAscii is '@') return null;
        display.lastAscii = display.controlKey (display.lastAscii);
    }
    if (!sendKeyEvent (SWT.KeyDown, OS.WM_KEYDOWN, wParam, lParam)) {
        return LRESULT.ONE;
    }
    // widget could be disposed at this point
    return null;
}

LRESULT wmKeyUp (HWND hwnd, int wParam, int lParam) {
    Display display = this.display;

    /* Check for hardware keys */
    static if (OS.IsWinCE) {
        if (OS.VK_APP1 <= wParam && wParam <= OS.VK_APP6) {
            display.lastKey = display.lastAscii = 0;
            display.lastVirtual = display.lastNull = display.lastDead = false;
            Event event = new Event ();
            event.detail = wParam - OS.VK_APP1 + 1;
            /* Check the bit 30 to get the key state */
            int type = (lParam & 0x40000000) !is 0 ? SWT.HardKeyUp : SWT.HardKeyDown;
            if (setInputState (event, type)) sendEvent (type, event);
            // widget could be disposed at this point
            return null;
        }
    }

    /*
    * If the key up is not hooked, reset last key
    * and last ascii in case the key down is hooked.
    */
    if (!hooks (SWT.KeyUp) && !display.filters (SWT.KeyUp)) {
        display.lastKey = display.lastAscii = 0;
        display.lastVirtual = display.lastNull = display.lastDead = false;
        return null;
    }

    /* Map the virtual key. */
    /*
    * Bug in WinCE.  MapVirtualKey() returns incorrect values.
    * The fix is to rely on a key mappings table to determine
    * whether the key event must be sent now or if a WM_CHAR
    * event will follow.  The key mappings table maps virtual
    * keys to SWT key codes and does not contain mappings for
    * Windows virtual keys like VK_A.  Virtual keys that are
    * both virtual and ASCII are a special case.
    */
    int mapKey = 0;
    static if (OS.IsWinCE) {
        switch (wParam) {
            case OS.VK_BACK: mapKey = SWT.BS; break;
            case OS.VK_RETURN: mapKey = SWT.CR; break;
            case OS.VK_DELETE: mapKey = SWT.DEL; break;
            case OS.VK_ESCAPE: mapKey = SWT.ESC; break;
            case OS.VK_TAB: mapKey = SWT.TAB; break;
            default:
        }
    } else {
        mapKey = OS.MapVirtualKey (wParam, 2);
    }

    /*
    * Bug in Windows 95 and NT.  When the user types an accent key such
    * as ^ to get an accented character on a German keyboard, the accent
    * key should be ignored and the next key that the user types is the
    * accented key. The fix is to detect the accent key stroke (called
    * a dead key) by testing the high bit of the value returned by
    * MapVirtualKey ().  A further problem is that the high bit on
    * Windows NT is bit 32 while the high bit on Windows 95 is bit 16.
    * They should both be bit 32.
    */
    if (OS.IsWinNT) {
        if ((mapKey & 0x80000000) !is 0) return null;
    } else {
        if ((mapKey & 0x8000) !is 0) return null;
    }
    if (display.lastDead) return null;

    /*
    * NOTE: On Windows 98, keypad keys are virtual despite the
    * fact that a WM_CHAR is issued.  On Windows 2000 and XP,
    * they are not virtual.  Therefore it is necessary to force
    * numeric keypad keys to be virtual.
    */
    display.lastVirtual = mapKey is 0 || display.numpadKey (wParam) !is 0;
    if (display.lastVirtual) {
        display.lastKey = wParam;
    } else {
        /*
        * Feature in Windows. The virtual key VK_CANCEL is treated
        * as both a virtual key and ASCII key by Windows.  This
        * means that a WM_CHAR with WPARAM=3 will be issued for
        * this key.  In order to distinguish between this key and
        * Ctrl+C, mark the key as virtual.
        */
        if (wParam is OS.VK_CANCEL) display.lastVirtual = true;
        if (display.lastKey is 0) {
            display.lastAscii = 0;
            display.lastNull = display.lastDead = false;
            return null;
        }
    }
    LRESULT result = null;
    if (!sendKeyEvent (SWT.KeyUp, OS.WM_KEYUP, wParam, lParam)) {
        result = LRESULT.ONE;
    }
    // widget could be disposed at this point
    display.lastKey = display.lastAscii = 0;
    display.lastVirtual = display.lastNull = display.lastDead = false;
    return result;
}

LRESULT wmKillFocus (HWND hwnd, int wParam, int lParam) {
    display.scrollRemainder = 0;
    int code = callWindowProc (hwnd, OS.WM_KILLFOCUS, wParam, lParam);
    sendFocusEvent (SWT.FocusOut);
    // widget could be disposed at this point

    /*
    * It is possible (but unlikely), that application
    * code could have disposed the widget in the focus
    * or deactivate events.  If this happens, end the
    * processing of the Windows message by returning
    * zero as the result of the window proc.
    */
    if (isDisposed ()) return LRESULT.ZERO;
    if (code is 0) return LRESULT.ZERO;
    return new LRESULT(code);
}

LRESULT wmLButtonDblClk (HWND hwnd, int wParam, int lParam) {
    /*
    * Feature in Windows. Windows sends the following
    * messages when the user double clicks the mouse:
    *
    *   WM_LBUTTONDOWN      - mouse down
    *   WM_LBUTTONUP        - mouse up
    *   WM_LBUTTONDBLCLK    - double click
    *   WM_LBUTTONUP        - mouse up
    *
    * Applications that expect matching mouse down/up
    * pairs will not see the second mouse down.  The
    * fix is to send a mouse down event.
    */
    LRESULT result = null;
    Display display = this.display;
    display.captureChanged = false;
    sendMouseEvent (SWT.MouseDown, 1, hwnd, OS.WM_LBUTTONDOWN, wParam, lParam);
    if (sendMouseEvent (SWT.MouseDoubleClick, 1, hwnd, OS.WM_LBUTTONDBLCLK, wParam, lParam)) {
        result = new LRESULT( callWindowProc (hwnd, OS.WM_LBUTTONDBLCLK, wParam, lParam));
    } else {
        result = LRESULT.ZERO;
    }
    if (!display.captureChanged && !isDisposed ()) {
        if (OS.GetCapture () !is hwnd) OS.SetCapture (hwnd);
    }
    return result;
}

LRESULT wmLButtonDown (HWND hwnd, int wParam, int lParam) {
    Display display = this.display;
    LRESULT result = null;
    int x = OS.GET_X_LPARAM (lParam);
    int y = OS.GET_Y_LPARAM (lParam);
    bool [] consume = null, detect = null;
    bool dragging = false, mouseDown = true;
    int count = display.getClickCount (SWT.MouseDown, 1, hwnd, lParam);
    if (count is 1 && (state & DRAG_DETECT) !is 0 && hooks (SWT.DragDetect)) {
        static if (!OS.IsWinCE) {
            /*
            * Feature in Windows.  It's possible that the drag
            * operation will not be started while the mouse is
            * down, meaning that the mouse should be captured.
            * This can happen when the user types the ESC key
            * to cancel the drag.  The fix is to query the state
            * of the mouse and capture the mouse accordingly.
            */
            detect = new bool [1];
            consume = new bool [1];
            dragging = dragDetect (hwnd, x, y, true, detect, consume);
            if (isDisposed ()) return LRESULT.ZERO;
            mouseDown = OS.GetKeyState (OS.VK_LBUTTON) < 0;
        }
    }
    display.captureChanged = false;
    bool dispatch = sendMouseEvent (SWT.MouseDown, 1, count, 0, false, hwnd, OS.WM_LBUTTONDOWN, wParam, lParam);
    if (dispatch && (consume is null || !consume [0])) {
        result = new LRESULT( callWindowProc (hwnd, OS.WM_LBUTTONDOWN, wParam, lParam));
    } else {
        result = LRESULT.ZERO;
    }
    static if( OS.IsWinCE ){
        if (OS.IsPPC) {
            /*
            * Note: On WinCE PPC, only attempt to recognize the gesture for
            * a context menu when the control contains a valid menu or there
            * are listeners for the MenuDetect event.
            */
            Menu menu = getMenu ();
            bool hasMenu = menu !is null && !menu.isDisposed ();
            if (hasMenu || hooks (SWT.MenuDetect)) {
                SHRGINFO shrg;
                shrg.cbSize = SHRGINFO.sizeof;
                shrg.hwndClient = hwnd;
                shrg.ptDown.x = x;
                shrg.ptDown.y = y;
                shrg.dwFlags = OS.SHRG_RETURNCMD;
                int type = OS.SHRecognizeGesture (&shrg);
                if (type is OS.GN_CONTEXTMENU) showMenu (x, y);
            }
        }
    }
    if (mouseDown) {
        if (!display.captureChanged && !isDisposed ()) {
            if (OS.GetCapture () !is hwnd) OS.SetCapture (hwnd);
        }
    }
    if (dragging) {
        sendDragEvent (1, x, y);
    } else {
        if (detect !is null && detect [0]) {
            /*
            * Feature in Windows.  DragDetect() captures the mouse
            * and tracks its movement until the user releases the
            * left mouse button, presses the ESC key, or moves the
            * mouse outside the drag rectangle.  If the user moves
            * the mouse outside of the drag rectangle, DragDetect()
            * returns true and a drag and drop operation can be
            * started.  When the left mouse button is released or
            * the ESC key is pressed, these events are consumed by
            * DragDetect() so that application code that matches
            * mouse down/up pairs or looks for the ESC key will not
            * function properly.  The fix is to send the missing
            * events when the drag has not started.
            *
            * NOTE: For now, don't send a fake WM_KEYDOWN/WM_KEYUP
            * events for the ESC key.  This would require computing
            * wParam (the key) and lParam (the repeat count, scan code,
            * extended-key flag, context code, previous key-state flag,
            * and transition-state flag) which is non-trivial.
            */
            if (OS.GetKeyState (OS.VK_ESCAPE) >= 0) {
                OS.SendMessage (hwnd, OS.WM_LBUTTONUP, wParam, lParam);
            }
        }
    }
    return result;
}

LRESULT wmLButtonUp (HWND hwnd, int wParam, int lParam) {
    Display display = this.display;
    LRESULT result = null;
    if (sendMouseEvent (SWT.MouseUp, 1, hwnd, OS.WM_LBUTTONUP, wParam, lParam)) {
        result = new LRESULT (callWindowProc (hwnd, OS.WM_LBUTTONUP, wParam, lParam));
    } else {
        result = LRESULT.ZERO;
    }
    /*
    * Bug in Windows.  On some machines that do not have XBUTTONs,
    * the MK_XBUTTON1 and OS.MK_XBUTTON2 bits are sometimes set,
    * causing mouse capture to become stuck.  The fix is to test
    * for the extra buttons only when they exist.
    */
    int mask = OS.MK_LBUTTON | OS.MK_MBUTTON | OS.MK_RBUTTON;
    if (display.xMouse) mask |= OS.MK_XBUTTON1 | OS.MK_XBUTTON2;
    if ((wParam & mask) is 0) {
        if (OS.GetCapture () is hwnd) OS.ReleaseCapture ();
    }
    return result;
}

LRESULT wmMButtonDblClk (HWND hwnd, int wParam, int lParam) {
    /*
    * Feature in Windows. Windows sends the following
    * messages when the user double clicks the mouse:
    *
    *   WM_MBUTTONDOWN      - mouse down
    *   WM_MBUTTONUP        - mouse up
    *   WM_MLBUTTONDBLCLK   - double click
    *   WM_MBUTTONUP        - mouse up
    *
    * Applications that expect matching mouse down/up
    * pairs will not see the second mouse down.  The
    * fix is to send a mouse down event.
    */
    LRESULT result = null;
    Display display = this.display;
    display.captureChanged = false;
    sendMouseEvent (SWT.MouseDown, 2, hwnd, OS.WM_MBUTTONDOWN, wParam, lParam);
    if (sendMouseEvent (SWT.MouseDoubleClick, 2, hwnd, OS.WM_MBUTTONDBLCLK, wParam, lParam)) {
        result = new LRESULT (callWindowProc (hwnd, OS.WM_MBUTTONDBLCLK, wParam, lParam));
    } else {
        result = LRESULT.ZERO;
    }
    if (!display.captureChanged && !isDisposed ()) {
        if (OS.GetCapture () !is hwnd) OS.SetCapture (hwnd);
    }
    return result;
}

LRESULT wmMButtonDown (HWND hwnd, int wParam, int lParam) {
    LRESULT result = null;
    Display display = this.display;
    display.captureChanged = false;
    if (sendMouseEvent (SWT.MouseDown, 2, hwnd, OS.WM_MBUTTONDOWN, wParam, lParam)) {
        result = new LRESULT (callWindowProc (hwnd, OS.WM_MBUTTONDOWN, wParam, lParam));
    } else {
        result = LRESULT.ZERO;
    }
    if (!display.captureChanged && !isDisposed ()) {
        if (OS.GetCapture () !is hwnd) OS.SetCapture (hwnd);
    }
    return result;
}

LRESULT wmMButtonUp (HWND hwnd, int wParam, int lParam) {
    Display display = this.display;
    LRESULT result = null;
    if (sendMouseEvent (SWT.MouseUp, 2, hwnd, OS.WM_MBUTTONUP, wParam, lParam)) {
        result = new LRESULT (callWindowProc (hwnd, OS.WM_MBUTTONUP, wParam, lParam));
    } else {
        result = LRESULT.ZERO;
    }
    /*
    * Bug in Windows.  On some machines that do not have XBUTTONs,
    * the MK_XBUTTON1 and OS.MK_XBUTTON2 bits are sometimes set,
    * causing mouse capture to become stuck.  The fix is to test
    * for the extra buttons only when they exist.
    */
    int mask = OS.MK_LBUTTON | OS.MK_MBUTTON | OS.MK_RBUTTON;
    if (display.xMouse) mask |= OS.MK_XBUTTON1 | OS.MK_XBUTTON2;
    if ((wParam & mask) is 0) {
        if (OS.GetCapture () is hwnd) OS.ReleaseCapture ();
    }
    return result;
}

LRESULT wmMouseHover (HWND hwnd, int wParam, int lParam) {
    if (!sendMouseEvent (SWT.MouseHover, 0, hwnd, OS.WM_MOUSEHOVER, wParam, lParam)) {
        return LRESULT.ZERO;
    }
    return null;
}

LRESULT wmMouseLeave (HWND hwnd, int wParam, int lParam) {
    if (!hooks (SWT.MouseExit) && !filters (SWT.MouseExit)) return null;
    int pos = OS.GetMessagePos ();
    POINT pt;
    OS.POINTSTOPOINT (pt, pos);
    OS.ScreenToClient (hwnd, &pt);
    lParam = OS.MAKELPARAM (pt.x, pt.y);
    if (!sendMouseEvent (SWT.MouseExit, 0, hwnd, OS.WM_MOUSELEAVE, wParam, lParam)) {
        return LRESULT.ZERO;
    }
    return null;
}

LRESULT wmMouseMove (HWND hwnd, int wParam, int lParam) {
    LRESULT result = null;
    Display display = this.display;
    int pos = OS.GetMessagePos ();
    if (pos !is display.lastMouse || display.captureChanged) {
        static if (!OS.IsWinCE) {
            bool trackMouse = (state & TRACK_MOUSE) !is 0;
            bool mouseEnter = hooks (SWT.MouseEnter) || display.filters (SWT.MouseEnter);
            bool mouseExit = hooks (SWT.MouseExit) || display.filters (SWT.MouseExit);
            bool mouseHover = hooks (SWT.MouseHover) || display.filters (SWT.MouseHover);
            if (trackMouse || mouseEnter || mouseExit || mouseHover) {
                TRACKMOUSEEVENT lpEventTrack;
                lpEventTrack.cbSize = TRACKMOUSEEVENT.sizeof;
                lpEventTrack.dwFlags = OS.TME_QUERY;
                lpEventTrack.hwndTrack = hwnd;
                OS.TrackMouseEvent (&lpEventTrack);
                if (lpEventTrack.dwFlags is 0) {
                    lpEventTrack.dwFlags = OS.TME_LEAVE | OS.TME_HOVER;
                    lpEventTrack.hwndTrack = hwnd;
                    OS.TrackMouseEvent (&lpEventTrack);
                    if (mouseEnter) {
                        /*
                        * Force all outstanding WM_MOUSELEAVE messages to be dispatched before
                        * issuing a mouse enter.  This causes mouse exit events to be processed
                        * before mouse enter events.  Note that WM_MOUSELEAVE is posted to the
                        * event queue by TrackMouseEvent().
                        */
                        MSG msg;
                        int flags = OS.PM_REMOVE | OS.PM_NOYIELD | OS.PM_QS_INPUT | OS.PM_QS_POSTMESSAGE;
                        while (OS.PeekMessage (&msg, null, OS.WM_MOUSELEAVE, OS.WM_MOUSELEAVE, flags)) {
                            OS.TranslateMessage (&msg);
                            OS.DispatchMessage (&msg);
                        }
                        sendMouseEvent (SWT.MouseEnter, 0, hwnd, OS.WM_MOUSEMOVE, wParam, lParam);
                    }
                } else {
                    lpEventTrack.dwFlags = OS.TME_HOVER;
                    OS.TrackMouseEvent (&lpEventTrack);
                }
            }
        }
        if (pos !is display.lastMouse) {
            display.lastMouse = pos;
            if (!sendMouseEvent (SWT.MouseMove, 0, hwnd, OS.WM_MOUSEMOVE, wParam, lParam)) {
                result = LRESULT.ZERO;
            }
        }
    }
    display.captureChanged = false;
    return result;
}

LRESULT wmMouseWheel (HWND hwnd, int wParam, int lParam) {
    int delta = OS.GET_WHEEL_DELTA_WPARAM (wParam);
    int linesToScroll;
    int detail;
    OS.SystemParametersInfo (OS.SPI_GETWHEELSCROLLLINES, 0, &linesToScroll, 0);
    if (linesToScroll is OS.WHEEL_PAGESCROLL) {
        detail = SWT.SCROLL_PAGE;
    } else {
        detail = SWT.SCROLL_LINE;
        delta *= linesToScroll;
    }
    /* Check if the delta and the remainder have the same direction (sign) */
    if ((delta ^ display.scrollRemainder) >= 0) delta += display.scrollRemainder;
    display.scrollRemainder = delta % OS.WHEEL_DELTA;

    if (!hooks (SWT.MouseWheel) && !filters (SWT.MouseWheel)) return null;
    int count = delta / OS.WHEEL_DELTA;
    POINT pt;
    OS.POINTSTOPOINT (pt, lParam);
    OS.ScreenToClient (hwnd, &pt);
    lParam = OS.MAKELPARAM (pt.x, pt.y);
    if (!sendMouseEvent (SWT.MouseWheel, 0, count, detail, true, hwnd, OS.WM_MOUSEWHEEL, wParam, lParam)) {
        return LRESULT.ZERO;
    }
    return null;
}

LRESULT wmNCPaint (HWND hwnd, int /*long*/ wParam, int /*long*/ lParam) {
    return null;
}

LRESULT wmPaint (HWND hwnd, int /*long*/ wParam, int /*long*/ lParam) {

    /* Exit early - don't draw the background */
    if (!hooks (SWT.Paint) && !filters (SWT.Paint)) {
        return null;
    }

    /* Issue a paint event */
    int /*long*/ result = 0;
    static if (OS.IsWinCE) {
        RECT rect;
        OS.GetUpdateRect (hwnd, &rect, false);
        result = callWindowProc (hwnd, OS.WM_PAINT, wParam, lParam);
        /*
        * Bug in Windows.  When InvalidateRgn(), InvalidateRect()
        * or RedrawWindow() with RDW_INVALIDATE is called from
        * within WM_PAINT to invalidate a region for a further
        * BeginPaint(), the caret is not properly erased causing
        * pixel corruption.  The fix is to hide and show the
        * caret.
        */
        OS.HideCaret (hwnd);
        OS.InvalidateRect (hwnd, &rect, false);
        OS.ShowCaret (hwnd);
        PAINTSTRUCT* ps = new PAINTSTRUCT;
        GCData data = new GCData ();
        data.ps = ps;
        data.hwnd = hwnd;
        GC gc = new_GC (data);
        if (gc !is null) {
            int width = ps.rcPaint.right - ps.rcPaint.left;
            int height = ps.rcPaint.bottom - ps.rcPaint.top;
            if (width !is 0 && height !is 0) {
                Event event = new Event ();
                event.gc = gc;
                event.x = ps.rcPaint.left;
                event.y = ps.rcPaint.top;
                event.width = width;
                event.height = height;
                sendEvent (SWT.Paint, event);
                // widget could be disposed at this point
                event.gc = null;
            }
            gc.dispose ();
        }
    } else {
        auto rgn = OS.CreateRectRgn (0, 0, 0, 0);
        OS.GetUpdateRgn (hwnd, rgn, false);
        result = callWindowProc (hwnd, OS.WM_PAINT, wParam, lParam);
        GCData data = new GCData ();
        data.hwnd = hwnd;
        GC gc = new_GC (data);
        if (gc !is null) {
            OS.HideCaret (hwnd);
            RECT rect;
            OS.GetRgnBox (rgn, &rect);
            int width = rect.right - rect.left;
            int height = rect.bottom - rect.top;
            if (width !is 0 && height !is 0) {
                auto hDC = gc.handle;
                OS.SelectClipRgn (hDC, rgn);
                OS.SetMetaRgn (hDC);
                Event event = new Event ();
                event.gc = gc;
                event.x = rect.left;
                event.y = rect.top;
                event.width = width;
                event.height = height;
                sendEvent (SWT.Paint, event);
                // widget could be disposed at this point
                event.gc = null;
            }
            gc.dispose ();
            OS.ShowCaret (hwnd);
        }
        OS.DeleteObject (rgn);
    }
    if (result is 0) return LRESULT.ZERO;
    return new LRESULT (result);
}

LRESULT wmPrint (HWND hwnd, int wParam, int lParam) {
    /*
    * Bug in Windows.  When WM_PRINT is used to print the contents
    * of a control that has WS_EX_CLIENTEDGE, the old 3D border is
    * drawn instead of the theme border.  The fix is to call the
    * default window proc and then draw the theme border on top.
    */
    if ((lParam & OS.PRF_NONCLIENT) !is 0) {
        if (OS.COMCTL32_MAJOR >= 6 && OS.IsAppThemed ()) {
            int bits = OS.GetWindowLong (hwnd, OS.GWL_EXSTYLE);
            if ((bits & OS.WS_EX_CLIENTEDGE) !is 0) {
                int /*long*/ code = callWindowProc (hwnd, OS.WM_PRINT, wParam, lParam);
                RECT rect;
                OS.GetWindowRect (hwnd, &rect);
                rect.right -= rect.left;
                rect.bottom -= rect.top;
                rect.left = rect.top = 0;
                int border = OS.GetSystemMetrics (OS.SM_CXEDGE);
                OS.ExcludeClipRect ( cast(void*)wParam, border, border, rect.right - border, rect.bottom - border);
                OS.DrawThemeBackground (display.hEditTheme (), cast(HDC)wParam, OS.EP_EDITTEXT, OS.ETS_NORMAL, &rect, null);
                return new LRESULT (code);
            }
        }
    }
    return null;
}

LRESULT wmRButtonDblClk (HWND hwnd, int wParam, int lParam) {
    /*
    * Feature in Windows. Windows sends the following
    * messages when the user double clicks the mouse:
    *
    *   WM_RBUTTONDOWN      - mouse down
    *   WM_RBUTTONUP        - mouse up
    *   WM_RBUTTONDBLCLK    - double click
    *   WM_LBUTTONUP        - mouse up
    *
    * Applications that expect matching mouse down/up
    * pairs will not see the second mouse down.  The
    * fix is to send a mouse down event.
    */
    LRESULT result = null;
    Display display = this.display;
    display.captureChanged = false;
    sendMouseEvent (SWT.MouseDown, 3, hwnd, OS.WM_RBUTTONDOWN, wParam, lParam);
    if (sendMouseEvent (SWT.MouseDoubleClick, 3, hwnd, OS.WM_RBUTTONDBLCLK, wParam, lParam)) {
        result = new LRESULT (callWindowProc (hwnd, OS.WM_RBUTTONDBLCLK, wParam, lParam));
    } else {
        result = LRESULT.ZERO;
    }
    if (!display.captureChanged && !isDisposed ()) {
        if (OS.GetCapture () !is hwnd) OS.SetCapture (hwnd);
    }
    return result;
}

LRESULT wmRButtonDown (HWND hwnd, int wParam, int lParam) {
    LRESULT result = null;
    Display display = this.display;
    display.captureChanged = false;
    if (sendMouseEvent (SWT.MouseDown, 3, hwnd, OS.WM_RBUTTONDOWN, wParam, lParam)) {
        result = new LRESULT (callWindowProc (hwnd, OS.WM_RBUTTONDOWN, wParam, lParam));
    } else {
        result = LRESULT.ZERO;
    }
    if (!display.captureChanged && !isDisposed ()) {
        if (OS.GetCapture () !is hwnd) OS.SetCapture (hwnd);
    }
    return result;
}

LRESULT wmRButtonUp (HWND hwnd, int wParam, int lParam) {
    Display display = this.display;
    LRESULT result = null;
    if (sendMouseEvent (SWT.MouseUp, 3, hwnd, OS.WM_RBUTTONUP, wParam, lParam)) {
        result = new LRESULT (callWindowProc (hwnd, OS.WM_RBUTTONUP, wParam, lParam));
    } else {
        /* Call the DefWindowProc() to support WM_CONTEXTMENU */
        OS.DefWindowProc (hwnd, OS.WM_RBUTTONUP, wParam, lParam);
        result = LRESULT.ZERO;
    }
    /*
    * Bug in Windows.  On some machines that do not have XBUTTONs,
    * the MK_XBUTTON1 and OS.MK_XBUTTON2 bits are sometimes set,
    * causing mouse capture to become stuck.  The fix is to test
    * for the extra buttons only when they exist.
    */
    int mask = OS.MK_LBUTTON | OS.MK_MBUTTON | OS.MK_RBUTTON;
    if (display.xMouse) mask |= OS.MK_XBUTTON1 | OS.MK_XBUTTON2;
    if ((wParam & mask) is 0) {
        if (OS.GetCapture () is hwnd) OS.ReleaseCapture ();
    }
    return result;
}

LRESULT wmSetFocus (HWND hwnd, int wParam, int lParam) {
    int /*long*/ code = callWindowProc (hwnd, OS.WM_SETFOCUS, wParam, lParam);
    sendFocusEvent (SWT.FocusIn);
    // widget could be disposed at this point

    /*
    * It is possible (but unlikely), that application
    * code could have disposed the widget in the focus
    * or activate events.  If this happens, end the
    * processing of the Windows message by returning
    * zero as the result of the window proc.
    */
    if (isDisposed ()) return LRESULT.ZERO;
    if (code is 0) return LRESULT.ZERO;
    return new LRESULT (code);
}

LRESULT wmSysChar (HWND hwnd, int wParam, int lParam) {
    Display display = this.display;
    display.lastAscii = wParam;
    display.lastNull = wParam is 0;

    /* Do not issue a key down if a menu bar mnemonic was invoked */
    if (!hooks (SWT.KeyDown) && !display.filters (SWT.KeyDown)) {
        return null;
    }

    /* Call the window proc to determine whether it is a system key or mnemonic */
    bool oldKeyHit = display.mnemonicKeyHit;
    display.mnemonicKeyHit = true;
    int /*long*/ result = callWindowProc (hwnd, OS.WM_SYSCHAR, wParam, lParam);
    bool consumed = false;
    if (!display.mnemonicKeyHit) {
        consumed = !sendKeyEvent (SWT.KeyDown, OS.WM_SYSCHAR, wParam, lParam);
        // widget could be disposed at this point
    }
    consumed |= display.mnemonicKeyHit;
    display.mnemonicKeyHit = oldKeyHit;
    return consumed ? LRESULT.ONE : new LRESULT (result);
}

LRESULT wmSysKeyDown (HWND hwnd, int wParam, int lParam) {
    /*
    * Feature in Windows.  When WM_SYSKEYDOWN is sent,
    * the user pressed ALT+<key> or F10 to get to the
    * menu bar.  In order to issue events for F10 but
    * ignore other key presses when the ALT is not down,
    * make sure that either F10 was pressed or that ALT
    * is pressed.
    */
    if (wParam !is OS.VK_F10) {
        /* Make sure WM_SYSKEYDOWN was sent by ALT-<aKey>. */
        if ((lParam & 0x20000000) is 0) return null;
    }

    /* Ignore well known system keys */
    switch (wParam) {
        case OS.VK_F4: {
            HWND hwndShell = hwnd;
            while (OS.GetParent (hwndShell) !is null) {
                if (OS.GetWindow (hwndShell, OS.GW_OWNER) !is null) break;
                hwndShell = OS.GetParent (hwndShell);
            }
            int bits = OS.GetWindowLong (hwndShell, OS.GWL_STYLE);
            if ((bits & OS.WS_SYSMENU) !is 0) return null;
        }
        default:
    }

    /* Ignore repeating modifier keys by testing key down state */
    switch (wParam) {
        case OS.VK_SHIFT:
        case OS.VK_MENU:
        case OS.VK_CONTROL:
        case OS.VK_CAPITAL:
        case OS.VK_NUMLOCK:
        case OS.VK_SCROLL:
            if ((lParam & 0x40000000) !is 0) return null;
        default:
    }

    /* Clear last key and last ascii because a new key has been typed */
    display.lastAscii = display.lastKey = 0;
    display.lastVirtual = display.lastNull = display.lastDead = false;

    /* If are going to get a WM_SYSCHAR, ignore this message. */
    /*
    * Bug in WinCE.  MapVirtualKey() returns incorrect values.
    * The fix is to rely on a key mappings table to determine
    * whether the key event must be sent now or if a WM_CHAR
    * event will follow.  The key mappings table maps virtual
    * keys to SWT key codes and does not contain mappings for
    * Windows virtual keys like VK_A.  Virtual keys that are
    * both virtual and ASCII are a special case.
    */
    int mapKey = 0;
    static if (OS.IsWinCE) {
        switch (wParam) {
            case OS.VK_BACK: mapKey = SWT.BS; break;
            case OS.VK_RETURN: mapKey = SWT.CR; break;
            case OS.VK_DELETE: mapKey = SWT.DEL; break;
            case OS.VK_ESCAPE: mapKey = SWT.ESC; break;
            case OS.VK_TAB: mapKey = SWT.TAB; break;
            default:
        }
    } else {
        mapKey = OS.MapVirtualKey (wParam, 2);
    }
    display.lastVirtual = mapKey is 0 || display.numpadKey (wParam) !is 0;
    if (display.lastVirtual) {
        display.lastKey = wParam;
        /*
        * Feature in Windows.  The virtual key VK_DELETE is not
        * treated as both a virtual key and an ASCII key by Windows.
        * Therefore, we will not receive a WM_SYSCHAR for this key.
        * The fix is to treat VK_DELETE as a special case and map
        * the ASCII value explicitly (Delete is 0x7F).
        */
        if (display.lastKey is OS.VK_DELETE) display.lastAscii = 0x7F;

        /* When a keypad key is typed, a WM_SYSCHAR is not issued */
        if (OS.VK_NUMPAD0 <= display.lastKey && display.lastKey <= OS.VK_DIVIDE) {
            /*
            * A WM_SYSCHAR will be issued for '*', '+', '-', '.' and '/'
            * on the numeric keypad.  Avoid issuing the key event twice
            * by checking for these keys.  Note that calling to ToAscii()
            * or ToUnicode(), clear the character that is entered using
            * the special Windows keypad sequence when NumLock is down
            * (ie. typing ALT+0231 should gives 'c' with a cedilla when
            * NumLock is down).  Do not call either of these from here.
            */
            switch (display.lastKey) {
                case OS.VK_MULTIPLY:
                case OS.VK_ADD:
                case OS.VK_SUBTRACT:
                case OS.VK_DECIMAL:
                case OS.VK_DIVIDE: return null;
                default:
            }
            display.lastAscii = display.numpadKey (display.lastKey);
        }
    } else {
        /*
        * Convert LastKey to lower case because Windows non-virtual
        * keys that are also ASCII keys, such as like VK_A, are have
        * upper case values in WM_SYSKEYDOWN despite the fact that the
        * Shift was not pressed.
        */
        display.lastKey = cast(int) OS.CharLower (cast(wchar*) mapKey);

        /*
        * Feature in Windows 98.  MapVirtualKey() indicates that
        * a WM_SYSCHAR message will occur for Alt+Enter but
        * this message never happens.  The fix is to issue the
        * event from WM_SYSKEYDOWN and map VK_RETURN to '\r'.
        */
        if (OS.IsWinNT) return null;
        if (wParam !is OS.VK_RETURN) return null;
        display.lastAscii = '\r';
    }

    if (!sendKeyEvent (SWT.KeyDown, OS.WM_SYSKEYDOWN, wParam, lParam)) {
        return LRESULT.ONE;
    }
    // widget could be disposed at this point
    return null;
}

LRESULT wmSysKeyUp (HWND hwnd, int wParam, int lParam) {
    return wmKeyUp (hwnd, wParam, lParam);
}

LRESULT wmXButtonDblClk (HWND hwnd, int wParam, int lParam) {
    /*
    * Feature in Windows. Windows sends the following
    * messages when the user double clicks the mouse:
    *
    *   WM_XBUTTONDOWN      - mouse down
    *   WM_XBUTTONUP        - mouse up
    *   WM_XLBUTTONDBLCLK   - double click
    *   WM_XBUTTONUP        - mouse up
    *
    * Applications that expect matching mouse down/up
    * pairs will not see the second mouse down.  The
    * fix is to send a mouse down event.
    */
    LRESULT result = null;
    Display display = this.display;
    display.captureChanged = false;
    int button = OS.HIWORD (wParam) is OS.XBUTTON1 ? 4 : 5;
    sendMouseEvent (SWT.MouseDown, button, hwnd, OS.WM_XBUTTONDOWN, wParam, lParam);
    if (sendMouseEvent (SWT.MouseDoubleClick, button, hwnd, OS.WM_XBUTTONDBLCLK, wParam, lParam)) {
        result = new LRESULT (callWindowProc (hwnd, OS.WM_XBUTTONDBLCLK, wParam, lParam));
    } else {
        result = LRESULT.ZERO;
    }
    if (!display.captureChanged && !isDisposed ()) {
        if (OS.GetCapture () !is hwnd) OS.SetCapture (hwnd);
    }
    return result;
}

LRESULT wmXButtonDown (HWND hwnd, int wParam, int lParam) {
    LRESULT result = null;
    Display display = this.display;
    display.captureChanged = false;
    display.xMouse = true;
    int button = OS.HIWORD (wParam) is OS.XBUTTON1 ? 4 : 5;
    if (sendMouseEvent (SWT.MouseDown, button, hwnd, OS.WM_XBUTTONDOWN, wParam, lParam)) {
        result = new LRESULT (callWindowProc (hwnd, OS.WM_XBUTTONDOWN, wParam, lParam));
    } else {
        result = LRESULT.ZERO;
    }
    if (!display.captureChanged && !isDisposed ()) {
        if (OS.GetCapture () !is hwnd) OS.SetCapture (hwnd);
    }
    return result;
}

LRESULT wmXButtonUp (HWND hwnd, int wParam, int lParam) {
    Display display = this.display;
    LRESULT result = null;
    int button = OS.HIWORD (wParam) is OS.XBUTTON1 ? 4 : 5;
    if (sendMouseEvent (SWT.MouseUp, button, hwnd, OS.WM_XBUTTONUP, wParam, lParam)) {
        result = new LRESULT (callWindowProc (hwnd, OS.WM_XBUTTONUP, wParam, lParam));
    } else {
        result = LRESULT.ZERO;
    }
    /*
    * Bug in Windows.  On some machines that do not have XBUTTONs,
    * the MK_XBUTTON1 and OS.MK_XBUTTON2 bits are sometimes set,
    * causing mouse capture to become stuck.  The fix is to test
    * for the extra buttons only when they exist.
    */
    int mask = OS.MK_LBUTTON | OS.MK_MBUTTON | OS.MK_RBUTTON;
    if (display.xMouse) mask |= OS.MK_XBUTTON1 | OS.MK_XBUTTON2;
    if ((wParam & mask) is 0) {
        if (OS.GetCapture () is hwnd) OS.ReleaseCapture ();
    }
    return result;
}
}