org.eclipse.swt.widgets.Widget.java Source code

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/*******************************************************************************
 * Copyright (c) 2000, 2017 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.swt.widgets;

import org.eclipse.swt.*;
import org.eclipse.swt.events.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.internal.*;
import org.eclipse.swt.internal.win32.*;

/**
 * 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;

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

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

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

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

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

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

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

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

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

    /* Notify of the opportunity to skin this widget */
    static final int SKIN_NEEDED = 1 << 21;

    /* Bidi "auto" text direction */
    static final int HAS_AUTO_DIRECTION = 1 << 22;

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

    /* Bidi UCC to enforce text direction */
    static final char LRE = '\u202a';
    static final char RLE = '\u202b';

    /* Bidi flag and for auto text direction */
    static final int AUTO_TEXT_DIRECTION = SWT.LEFT_TO_RIGHT | SWT.RIGHT_TO_LEFT;

    /* Initialize the Common Controls DLL */
    static {
        OS.InitCommonControls();
    }

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

    /**
     * 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 Widget(Widget parent, int style) {
        checkSubclass();
        checkParent(parent);
        this.style = style;
        display = parent.display;
        reskinWidget();
    }

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

    void _removeListener(int eventType, Listener listener) {
        if (eventTable == null)
            return;
        eventTable.unhook(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 == 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 == null)
            error(SWT.ERROR_NULL_ARGUMENT);
        TypedListener typedListener = new TypedListener(listener);
        addListener(SWT.Dispose, typedListener);
    }

    long callWindowProc(long hwnd, int msg, long wParam, long 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) == 0)
            style |= int0;
        if ((style & int0) != 0)
            style = (style & ~mask) | int0;
        if ((style & int1) != 0)
            style = (style & ~mask) | int1;
        if ((style & int2) != 0)
            style = (style & ~mask) | int2;
        if ((style & int3) != 0)
            style = (style & ~mask) | int3;
        if ((style & int4) != 0)
            style = (style & ~mask) | int4;
        if ((style & int5) != 0)
            style = (style & ~mask) | int5;
        return style;
    }

    void checkOrientation(Widget parent) {
        style &= ~SWT.MIRRORED;
        if ((style & (SWT.LEFT_TO_RIGHT | SWT.RIGHT_TO_LEFT)) == 0) {
            if (parent != null) {
                if ((parent.style & SWT.LEFT_TO_RIGHT) != 0)
                    style |= SWT.LEFT_TO_RIGHT;
                if ((parent.style & SWT.RIGHT_TO_LEFT) != 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 == 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>
     */
    protected void checkWidget() {
        Display display = this.display;
        if (display == null)
            error(SWT.ERROR_WIDGET_DISPOSED);
        if (display.thread != 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 != OS.GetCurrentThreadId()) {
                error(SWT.ERROR_THREAD_INVALID_ACCESS);
            }
        }
        if ((state & DISPOSED) != 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();
    }

    /**
     * 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.
     * This method does nothing if the widget is already disposed.
     * <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);
    }

    boolean dragDetect(long hwnd, int x, int y, boolean filter, boolean[] detect, boolean[] consume) {
        if (consume != null)
            consume[0] = false;
        if (detect != null)
            detect[0] = true;
        POINT pt = new POINT();
        pt.x = x;
        pt.y = y;
        OS.ClientToScreen(hwnd, pt);
        return 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);
    }

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

    Widget findItem(long id) {
        return null;
    }

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

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

    char[] fixMnemonic(String string, boolean spaces, boolean removeAppended) {
        // fixMnemonic must return a null-terminated array
        char[] buffer = new char[string.length() + 1];
        string.getChars(0, string.length(), buffer, 0);
        int i = 0, j = 0;
        while (i < buffer.length) {
            if (buffer[i] == '&') {
                if (i + 1 < buffer.length && buffer[i + 1] == '&') {
                    buffer[j++] = spaces ? ' ' : buffer[i];
                    i++;
                }
                i++;
            } else if (buffer[i] == '(' && removeAppended && i + 4 == string.length() && buffer[i + 1] == '&'
                    && buffer[i + 3] == ')') {
                if (spaces)
                    buffer[j++] = ' ';
                i += 4;
            } else {
                buffer[j++] = buffer[i++];
            }
        }
        while (j < buffer.length)
            buffer[j++] = 0;
        return buffer;
    }

    /**
     * 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) != 0 ? ((Object[]) data)[0] : data;
    }

    /**
     * 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 IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the key 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 #setData(String, Object)
     */
    public Object getData(String key) {
        checkWidget();
        if (key == null)
            error(SWT.ERROR_NULL_ARGUMENT);
        if ((state & KEYED_DATA) != 0) {
            Object[] table = (Object[]) data;
            for (int i = 1; i < table.length; i += 2) {
                if (key.equals(table[i]))
                    return table[i + 1];
            }
        }
        return null;
    }

    /**
     * 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 == 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 == 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 string = getClass().getName();
        int index = string.lastIndexOf('.');
        if (index == -1)
            return string;
        return string.substring(index + 1, string.length());
    }

    /*
     * 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
     */
    boolean hooks(int eventType) {
        if (eventTable == null)
            return false;
        return eventTable.hooks(eventType);
    }

    /**
     * Returns <code>true</code> if the widget has auto text direction,
     * and <code>false</code> otherwise.
     *
     * @return <code>true</code> when the widget has auto direction and <code>false</code> otherwise
     *
     * @see SWT#AUTO_TEXT_DIRECTION
     *
     * @since 3.105
     */
    public boolean isAutoDirection() {
        return (state & HAS_AUTO_DIRECTION) != 0;
    }

    /**
     * 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 (except {@link #dispose()}) using the widget.
     * </p>
     *
     * @return <code>true</code> when the widget is disposed and <code>false</code> otherwise
     */
    public boolean isDisposed() {
        return (state & DISPOSED) != 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 boolean 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
     */
    boolean isValidSubclass() {
        return 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
     */
    boolean isValidThread() {
        return getDisplay().isValidThread();
    }

    void mapEvent(long 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 == 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(boolean destroy) {
        if ((state & DISPOSE_SENT) == 0) {
            state |= DISPOSE_SENT;
            sendEvent(SWT.Dispose);
        }
        if ((state & DISPOSED) == 0) {
            releaseChildren(destroy);
        }
        if ((state & RELEASED) == 0) {
            state |= RELEASED;
            if (destroy) {
                releaseParent();
                releaseWidget();
                destroyWidget();
            } else {
                releaseWidget();
                releaseHandle();
            }
        }
    }

    void releaseChildren(boolean 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 == null)
            error(SWT.ERROR_NULL_ARGUMENT);
        _removeListener(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
     *
     * @noreference This method is not intended to be referenced by clients.
     * @nooverride This method is not intended to be re-implemented or extended by clients.
     */
    protected void removeListener(int eventType, SWTEventListener listener) {
        checkWidget();
        if (listener == null)
            error(SWT.ERROR_NULL_ARGUMENT);
        if (eventTable == 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 == null)
            error(SWT.ERROR_NULL_ARGUMENT);
        if (eventTable == null)
            return;
        eventTable.unhook(SWT.Dispose, listener);
    }

    /**
     * Marks the widget to be skinned.
     * <p>
     * The skin event is sent to the receiver's display when appropriate (usually before the next event
     * is handled). Widgets are automatically marked for skinning upon creation as well as when its skin
     * id or class changes. The skin id and/or class can be changed by calling {@link Display#setData(String, Object)}
     * with the keys {@link SWT#SKIN_ID} and/or {@link SWT#SKIN_CLASS}. Once the skin event is sent to a widget, it
     * will not be sent again unless <code>reskin(int)</code> is called on the widget or on an ancestor
     * while specifying the <code>SWT.ALL</code> flag.
     * </p>
     * <p>
     * The parameter <code>flags</code> may be either:
     * </p>
     * <dl>
     * <dt><b>{@link SWT#ALL}</b></dt>
     * <dd>all children in the receiver's widget tree should be skinned</dd>
     * <dt><b>{@link SWT#NONE}</b></dt>
     * <dd>only the receiver should be skinned</dd>
     * </dl>
     * @param flags the flags specifying how to reskin
     *
     * @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>
     * @since 3.6
     */
    public void reskin(int flags) {
        checkWidget();
        reskinWidget();
        if ((flags & SWT.ALL) != 0)
            reskinChildren(flags);
    }

    void reskinChildren(int flags) {
    }

    void reskinWidget() {
        if ((state & SKIN_NEEDED) != SKIN_NEEDED) {
            this.state |= SKIN_NEEDED;
            display.addSkinnableWidget(this);
        }
    }

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

    boolean sendDragEvent(int button, int stateMask, int x, int y) {
        Event event = new Event();
        event.button = button;
        event.setLocationInPixels(x, 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 != null)
                display.sendEvent(eventTable, 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, boolean send) {
        if (eventTable == null && !display.filters(eventType)) {
            return;
        }
        if (event == null)
            event = new Event();
        event.type = eventType;
        event.display = display;
        event.widget = this;
        if (event.time == 0) {
            event.time = display.getLastEventTime();
        }
        if (send) {
            sendEvent(event);
        } else {
            display.postEvent(event);
        }
    }

    void sendSelectionEvent(int type) {
        sendSelectionEvent(type, null, false);
    }

    void sendSelectionEvent(int type, Event event, boolean send) {
        if (eventTable == null && !display.filters(type)) {
            return;
        }
        if (event == null)
            event = new Event();
        setInputState(event, type);
        sendEvent(type, event, send);
    }

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

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

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

    boolean sendMouseEvent(int type, int button, int count, int detail, boolean send, long hwnd, int msg,
            long wParam, long lParam) {
        if (!hooks(type) && !filters(type))
            return true;
        Event event = new Event();
        event.button = button;
        event.detail = detail;
        event.count = count;
        event.setLocationInPixels(OS.GET_X_LPARAM(lParam), 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;
    }

    boolean sendMouseWheelEvent(int type, long hwnd, long wParam, long lParam) {
        int delta = OS.GET_WHEEL_DELTA_WPARAM(wParam);
        int detail = 0;
        if (type == SWT.MouseWheel) {
            int[] linesToScroll = new int[1];
            OS.SystemParametersInfo(OS.SPI_GETWHEELSCROLLLINES, 0, linesToScroll, 0);
            if (linesToScroll[0] == OS.WHEEL_PAGESCROLL) {
                detail = SWT.SCROLL_PAGE;
            } else {
                detail = SWT.SCROLL_LINE;
                delta *= linesToScroll[0];
            }
            /* 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;
        } else {
            /* Check if the delta and the remainder have the same direction (sign) */
            if ((delta ^ display.scrollHRemainder) >= 0)
                delta += display.scrollHRemainder;
            display.scrollHRemainder = delta % OS.WHEEL_DELTA;

            delta = -delta;
        }

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

    /**
     * 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) != 0) {
            ((Object[]) this.data)[0] = data;
        } else {
            this.data = 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 IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the key 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 #getData(String)
     */
    public void setData(String key, Object value) {
        checkWidget();
        if (key == null)
            error(SWT.ERROR_NULL_ARGUMENT);
        int index = 1;
        Object[] table = null;
        if ((state & KEYED_DATA) != 0) {
            table = (Object[]) data;
            while (index < table.length) {
                if (key.equals(table[index]))
                    break;
                index += 2;
            }
        }
        if (value != null) {
            if ((state & KEYED_DATA) != 0) {
                if (index == table.length) {
                    Object[] newTable = new Object[table.length + 2];
                    System.arraycopy(table, 0, newTable, 0, table.length);
                    data = table = newTable;
                }
            } else {
                table = new Object[3];
                table[0] = data;
                data = table;
                state |= KEYED_DATA;
            }
            table[index] = key;
            table[index + 1] = value;
        } else {
            if ((state & KEYED_DATA) != 0) {
                if (index != table.length) {
                    int length = table.length - 2;
                    if (length == 1) {
                        data = table[0];
                        state &= ~KEYED_DATA;
                    } else {
                        Object[] newTable = new Object[length];
                        System.arraycopy(table, 0, newTable, 0, index);
                        System.arraycopy(table, index + 2, newTable, index, length - index);
                        data = newTable;
                    }
                }
            }
        }
        if (key.equals(SWT.SKIN_CLASS) || key.equals(SWT.SKIN_ID))
            this.reskin(SWT.ALL);
    }

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

    boolean 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;
        /*
        * 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.
        */
        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 == 1)
                event.stateMask &= ~SWT.BUTTON1;
            if (event.button == 2)
                event.stateMask &= ~SWT.BUTTON2;
            if (event.button == 3)
                event.stateMask &= ~SWT.BUTTON3;
            if (event.button == 4)
                event.stateMask &= ~SWT.BUTTON4;
            if (event.button == 5)
                event.stateMask &= ~SWT.BUTTON5;
            break;
        case SWT.MouseUp:
            if (event.button == 1)
                event.stateMask |= SWT.BUTTON1;
            if (event.button == 2)
                event.stateMask |= SWT.BUTTON2;
            if (event.button == 3)
                event.stateMask |= SWT.BUTTON3;
            if (event.button == 4)
                event.stateMask |= SWT.BUTTON4;
            if (event.button == 5)
                event.stateMask |= SWT.BUTTON5;
            break;
        case SWT.KeyDown:
        case SWT.Traverse:
            if (event.keyCode == SWT.ALT)
                event.stateMask &= ~SWT.ALT;
            if (event.keyCode == SWT.SHIFT)
                event.stateMask &= ~SWT.SHIFT;
            if (event.keyCode == SWT.CONTROL)
                event.stateMask &= ~SWT.CONTROL;
            break;
        case SWT.KeyUp:
            if (event.keyCode == SWT.ALT)
                event.stateMask |= SWT.ALT;
            if (event.keyCode == SWT.SHIFT)
                event.stateMask |= SWT.SHIFT;
            if (event.keyCode == SWT.CONTROL)
                event.stateMask |= SWT.CONTROL;
            break;
        }
        return true;
    }

    boolean setKeyState(Event event, int type, long wParam, 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 == SWT.BS)
                display.lastAscii = SWT.BS;
            break;
        case SWT.LF:
            if (display.lastKey == SWT.CR)
                display.lastAscii = SWT.CR;
            break;
        }

        /*
        * 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 == SWT.CR && display.lastAscii == SWT.CR) {
            if ((lParam & 0x1000000) != 0)
                display.lastKey = SWT.KEYPAD_CR;
        }

        setLocationMask(event, type, wParam, lParam);

        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 == 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 == OS.VK_CANCEL)
                display.lastAscii = 0x0;

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

    int setLocationMask(Event event, int type, long wParam, long lParam) {
        int location = SWT.NONE;
        if (display.lastVirtual) {
            switch (display.lastKey) {
            case OS.VK_SHIFT:
                if (OS.GetKeyState(OS.VK_LSHIFT) < 0)
                    location = SWT.LEFT;
                if (OS.GetKeyState(OS.VK_RSHIFT) < 0)
                    location = SWT.RIGHT;
                break;
            case OS.VK_NUMLOCK:
                location = SWT.KEYPAD;
                break;
            case OS.VK_CONTROL:
            case OS.VK_MENU:
                location = (lParam & 0x1000000) == 0 ? SWT.LEFT : SWT.RIGHT;
                break;
            case OS.VK_INSERT:
            case OS.VK_DELETE:
            case OS.VK_HOME:
            case OS.VK_END:
            case OS.VK_PRIOR:
            case OS.VK_NEXT:
            case OS.VK_UP:
            case OS.VK_DOWN:
            case OS.VK_LEFT:
            case OS.VK_RIGHT:
                if ((lParam & 0x1000000) == 0) {
                    location = SWT.KEYPAD;
                }
                break;
            }
            if (display.numpadKey(display.lastKey) != 0) {
                location = SWT.KEYPAD;
            }
        } else {
            if (display.lastKey == SWT.KEYPAD_CR) {
                location = SWT.KEYPAD;
            }
        }
        event.keyLocation = location;
        return location;
    }

    boolean setTabGroupFocus() {
        return setTabItemFocus();
    }

    boolean setTabItemFocus() {
        return false;
    }

    boolean showMenu(int x, int y) {
        return showMenu(x, y, SWT.MENU_MOUSE);
    }

    boolean showMenu(int x, int y, int detail) {
        Event event = new Event();
        event.setLocationInPixels(x, y);
        event.detail = detail;
        if (event.detail == SWT.MENU_KEYBOARD) {
            updateMenuLocation(event);
        }
        sendEvent(SWT.MenuDetect, event);
        // widget could be disposed at this point
        if (isDisposed())
            return false;
        if (!event.doit)
            return true;
        Menu menu = getMenu();
        if (menu != null && !menu.isDisposed()) {
            Point loc = event.getLocationInPixels(); // In Pixels
            if (x != loc.x || y != loc.y) {
                menu.setLocation(event.getLocation());
            }
            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 getName() + " {" + string + "}"; //$NON-NLS-1$ //$NON-NLS-2$
    }

    void updateMenuLocation(Event event) {
        /* Do nothing */
    }

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

    LRESULT wmChar(long hwnd, long wParam, long lParam) {
        display.lastAscii = (int) wParam;
        display.lastNull = wParam == 0;
        if (!sendKeyEvent(SWT.KeyDown, OS.WM_CHAR, wParam, lParam)) {
            return LRESULT.ONE;
        }
        // widget could be disposed at this point
        return null;
    }

    LRESULT wmContextMenu(long hwnd, long wParam, long lParam) {
        if (wParam != hwnd)
            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, detail = 0;
        if (lParam != -1) {
            POINT pt = new POINT();
            OS.POINTSTOPOINT(pt, lParam);
            x = pt.x;
            y = pt.y;
            detail = SWT.MENU_MOUSE;
            OS.ScreenToClient(hwnd, pt);
            RECT rect = new 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);
            detail = SWT.MENU_KEYBOARD;
        }

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

    LRESULT wmIMEChar(long hwnd, long wParam, long lParam) {
        Display display = this.display;
        display.lastKey = 0;
        display.lastAscii = (int) 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(long hwnd, long wParam, long lParam) {

        /* Ignore repeating modifier keys by testing key down state */
        switch ((int) 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) != 0)
                return null;
        }

        /* 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;

        /* Map the virtual key */
        int mapKey = OS.MapVirtualKey((int) wParam, 2);
        /*
        * Feature in Windows.  For Devanagari and Bengali numbers,
        * MapVirtualKey() returns the localized number instead of
        * the ASCII equivalent.  For example, MapVirtualKey()
        * maps VK_1 on the numbers keyboard to \u0967, which is
        * the Devanagari digit '1', but not ASCII.
        * The fix is to test for Devanagari and Bengali digits and
        * map these explicitly.
        *
        * NOTE: VK_0 to VK_9 are the same as ASCII.
        */
        if (('\u09e6' <= mapKey && mapKey <= '\u09ef') || ('\u0966' <= mapKey && mapKey <= '\u096f')) {
            mapKey = (int) wParam;
        }

        /*
        * 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().
        *
        * 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 ((mapKey & 0x80000000) != 0)
            return null;

        MSG msg = new 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 == 0;
            display.lastKey = display.lastVirtual ? (int) 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 == 0 || display.numpadKey((int) wParam) != 0;
        if (display.lastVirtual) {
            display.lastKey = (int) 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 == 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) != 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 = (int) OS.CharLower((short) 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 == 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.
            */
            int asciiKey = display.asciiKey((int) wParam);
            if (asciiKey != 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 == ' ')
                    return null;
                if (asciiKey != (int) 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 == 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((int) wParam);
                if (display.lastAscii == 0)
                    display.lastAscii = mapKey;
            } else {
                display.lastAscii = (int) OS.CharLower((short) mapKey);
            }

            /* Note that Ctrl+'@' is ASCII NUL and is delivered in WM_CHAR */
            if (display.lastAscii == '@')
                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(long hwnd, long wParam, long lParam) {
        Display display = this.display;

        /*
        * 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. */
        int mapKey = OS.MapVirtualKey((int) 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 ().
        */
        if ((mapKey & 0x80000000) != 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 == 0 || display.numpadKey((int) wParam) != 0;
        if (display.lastVirtual) {
            display.lastKey = (int) 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 == OS.VK_CANCEL)
                display.lastVirtual = true;
            if (display.lastKey == 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(long hwnd, long wParam, long lParam) {
        display.scrollRemainder = display.scrollHRemainder = 0;
        long 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 == 0)
            return LRESULT.ZERO;
        return new LRESULT(code);
    }

    LRESULT wmLButtonDblClk(long hwnd, long wParam, long 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() != hwnd)
                OS.SetCapture(hwnd);
        }
        return result;
    }

    LRESULT wmLButtonDown(long hwnd, long wParam, long lParam) {
        Display display = this.display;
        LRESULT result = null;
        int x = OS.GET_X_LPARAM(lParam);
        int y = OS.GET_Y_LPARAM(lParam);
        boolean[] consume = null, detect = null;
        boolean dragging = false, mouseDown = true;
        int count = display.getClickCount(SWT.MouseDown, 1, hwnd, lParam);
        if (count == 1 && (state & DRAG_DETECT) != 0 && hooks(SWT.DragDetect)) {
            /*
            * 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 boolean[1];
            consume = new boolean[1];
            dragging = dragDetect(hwnd, x, y, true, detect, consume);
            if (isDisposed())
                return LRESULT.ZERO;
            mouseDown = OS.GetKeyState(OS.VK_LBUTTON) < 0;
        }
        display.captureChanged = false;
        boolean dispatch = sendMouseEvent(SWT.MouseDown, 1, count, 0, false, hwnd, OS.WM_LBUTTONDOWN, wParam,
                lParam);
        if (dispatch && (consume == null || !consume[0])) {
            result = new LRESULT(callWindowProc(hwnd, OS.WM_LBUTTONDOWN, wParam, lParam));
        } else {
            result = LRESULT.ZERO;
        }
        if (mouseDown) {
            if (!display.captureChanged && !isDisposed()) {
                if (OS.GetCapture() != hwnd)
                    OS.SetCapture(hwnd);
            }
        }
        if (dragging) {
            sendDragEvent(1, x, y);
        } else {
            if (detect != 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(long hwnd, long wParam, long 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) == 0) {
            if (OS.GetCapture() == hwnd)
                OS.ReleaseCapture();
        }
        return result;
    }

    LRESULT wmMButtonDblClk(long hwnd, long wParam, long 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() != hwnd)
                OS.SetCapture(hwnd);
        }
        return result;
    }

    LRESULT wmMButtonDown(long hwnd, long wParam, long 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() != hwnd)
                OS.SetCapture(hwnd);
        }
        return result;
    }

    LRESULT wmMButtonUp(long hwnd, long wParam, long 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) == 0) {
            if (OS.GetCapture() == hwnd)
                OS.ReleaseCapture();
        }
        return result;
    }

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

    LRESULT wmMouseLeave(long hwnd, long wParam, long lParam) {
        if (!hooks(SWT.MouseExit) && !filters(SWT.MouseExit))
            return null;
        int pos = OS.GetMessagePos();
        POINT pt = new POINT();
        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(long hwnd, long wParam, long lParam) {
        LRESULT result = null;
        Display display = this.display;
        int pos = OS.GetMessagePos();
        if (pos != display.lastMouse || display.captureChanged) {
            boolean trackMouse = (state & TRACK_MOUSE) != 0;
            boolean mouseEnter = hooks(SWT.MouseEnter) || display.filters(SWT.MouseEnter);
            boolean mouseExit = hooks(SWT.MouseExit) || display.filters(SWT.MouseExit);
            boolean mouseHover = hooks(SWT.MouseHover) || display.filters(SWT.MouseHover);
            if (trackMouse || mouseEnter || mouseExit || mouseHover) {
                TRACKMOUSEEVENT lpEventTrack = new TRACKMOUSEEVENT();
                lpEventTrack.cbSize = TRACKMOUSEEVENT.sizeof;
                lpEventTrack.dwFlags = OS.TME_QUERY;
                lpEventTrack.hwndTrack = hwnd;
                OS.TrackMouseEvent(lpEventTrack);
                if (lpEventTrack.dwFlags == 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 = new MSG();
                        int flags = OS.PM_REMOVE | OS.PM_NOYIELD | OS.PM_QS_INPUT | OS.PM_QS_POSTMESSAGE;
                        while (OS.PeekMessage(msg, 0, 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 != 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(long hwnd, long wParam, long lParam) {
        return sendMouseWheelEvent(SWT.MouseWheel, hwnd, wParam, lParam) ? null : LRESULT.ZERO;
    }

    LRESULT wmMouseHWheel(long hwnd, long wParam, long lParam) {
        return sendMouseWheelEvent(SWT.MouseHorizontalWheel, hwnd, wParam, lParam) ? null : LRESULT.ZERO;
    }

    LRESULT wmNCPaint(long hwnd, long wParam, long lParam) {
        return null;
    }

    LRESULT wmPaint(long hwnd, long wParam, long lParam) {

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

        /* Issue a paint event */
        long rgn = OS.CreateRectRgn(0, 0, 0, 0);
        OS.GetUpdateRgn(hwnd, rgn, false);
        long result = callWindowProc(hwnd, OS.WM_PAINT, wParam, lParam);
        GCData data = new GCData();
        data.hwnd = hwnd;
        GC gc = new_GC(data);
        if (gc != null) {
            OS.HideCaret(hwnd);
            RECT rect = new RECT();
            OS.GetRgnBox(rgn, rect);
            int width = rect.right - rect.left;
            int height = rect.bottom - rect.top;
            if (width != 0 && height != 0) {
                long hDC = gc.handle;
                OS.SelectClipRgn(hDC, rgn);
                OS.SetMetaRgn(hDC);
                Event event = new Event();
                event.gc = gc;
                event.setBoundsInPixels(new Rectangle(rect.left, rect.top, width, 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 == 0)
            return LRESULT.ZERO;
        return new LRESULT(result);
    }

    LRESULT wmPrint(long hwnd, long wParam, long 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) != 0) {
            if (OS.IsAppThemed()) {
                int bits = OS.GetWindowLong(hwnd, OS.GWL_EXSTYLE);
                if ((bits & OS.WS_EX_CLIENTEDGE) != 0) {
                    long code = callWindowProc(hwnd, OS.WM_PRINT, wParam, lParam);
                    RECT rect = new 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(wParam, border, border, rect.right - border, rect.bottom - border);
                    OS.DrawThemeBackground(display.hEditTheme(), wParam, OS.EP_EDITTEXT, OS.ETS_NORMAL, rect, null);
                    return new LRESULT(code);
                }
            }
        }
        return null;
    }

    LRESULT wmRButtonDblClk(long hwnd, long wParam, long 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() != hwnd)
                OS.SetCapture(hwnd);
        }
        return result;
    }

    LRESULT wmRButtonDown(long hwnd, long wParam, long 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() != hwnd)
                OS.SetCapture(hwnd);
        }
        return result;
    }

    LRESULT wmRButtonUp(long hwnd, long wParam, long 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) == 0) {
            if (OS.GetCapture() == hwnd)
                OS.ReleaseCapture();
        }
        return result;
    }

    LRESULT wmSetFocus(long hwnd, long wParam, long lParam) {
        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 == 0)
            return LRESULT.ZERO;
        return new LRESULT(code);
    }

    LRESULT wmSysChar(long hwnd, long wParam, long lParam) {
        Display display = this.display;
        display.lastAscii = (int) wParam;
        display.lastNull = wParam == 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 */
        boolean oldKeyHit = display.mnemonicKeyHit;
        display.mnemonicKeyHit = true;
        long result = callWindowProc(hwnd, OS.WM_SYSCHAR, wParam, lParam);
        boolean 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(long hwnd, long wParam, long 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 != OS.VK_F10) {
            /* Make sure WM_SYSKEYDOWN was sent by ALT-<aKey>. */
            if ((lParam & 0x20000000) == 0)
                return null;
        }

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

        /* Ignore repeating modifier keys by testing key down state */
        switch ((int) 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) != 0)
                return null;
        }

        /* 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. */
        int mapKey = OS.MapVirtualKey((int) wParam, 2);

        display.lastVirtual = mapKey == 0 || display.numpadKey((int) wParam) != 0;
        if (display.lastVirtual) {
            display.lastKey = (int) 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 == 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;
                }
                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 = (int) OS.CharLower((short) mapKey);
            return null;
        }

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

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

    LRESULT wmXButtonDblClk(long hwnd, long wParam, long 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) == 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() != hwnd)
                OS.SetCapture(hwnd);
        }
        return result;
    }

    LRESULT wmXButtonDown(long hwnd, long wParam, long lParam) {
        LRESULT result = null;
        Display display = this.display;
        display.captureChanged = false;
        display.xMouse = true;
        int button = OS.HIWORD(wParam) == 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() != hwnd)
                OS.SetCapture(hwnd);
        }
        return result;
    }

    LRESULT wmXButtonUp(long hwnd, long wParam, long lParam) {
        Display display = this.display;
        LRESULT result = null;
        int button = OS.HIWORD(wParam) == 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) == 0) {
            if (OS.GetCapture() == hwnd)
                OS.ReleaseCapture();
        }
        return result;
    }
}