org.eclipse.swt.custom.CCombo.java Source code

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/*******************************************************************************
 * Copyright (c) 2000, 2016 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.custom;

import java.util.function.*;

import org.eclipse.swt.*;
import org.eclipse.swt.accessibility.*;
import org.eclipse.swt.events.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.widgets.*;

/**
 * The CCombo class represents a selectable user interface object
 * that combines a text field and a list and issues notification
 * when an item is selected from the list.
 * <p>
 * CCombo was written to work around certain limitations in the native
 * combo box. Specifically, on win32, the height of a CCombo can be set;
 * attempts to set the height of a Combo are ignored. CCombo can be used
 * anywhere that having the increased flexibility is more important than
 * getting native L&amp;F, but the decision should not be taken lightly.
 * There is no is no strict requirement that CCombo look or behave
 * the same as the native combo box.
 * </p>
 * <p>
 * Note that although this class is a subclass of <code>Composite</code>,
 * it does not make sense to add children to it, or set a layout on it.
 * </p>
 * <dl>
 * <dt><b>Styles:</b>
 * <dd>BORDER, READ_ONLY, FLAT</dd>
 * <dt><b>Events:</b>
 * <dd>DefaultSelection, Modify, Selection, Verify</dd>
 * </dl>
 *
 * @see <a href="http://www.eclipse.org/swt/snippets/#ccombo">CCombo snippets</a>
 * @see <a href="http://www.eclipse.org/swt/examples.php">SWT Example: CustomControlExample</a>
 * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>
 */
public class CCombo extends Composite {

    Text text;
    List list;
    int visibleItemCount = 5;
    Shell popup;
    Button arrow;
    boolean hasFocus;
    Listener listener, filter;
    Color foreground, background;
    Font font;
    Shell _shell;

    static final String PACKAGE_PREFIX = "org.eclipse.swt.custom."; //$NON-NLS-1$

    /**
     * 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>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li>
     * </ul>
     *
     * @see SWT#BORDER
     * @see SWT#READ_ONLY
     * @see SWT#FLAT
     * @see Widget#getStyle()
     */
    public CCombo(Composite parent, int style) {
        super(parent, style = checkStyle(style));
        _shell = super.getShell();

        int textStyle = SWT.SINGLE;
        if ((style & SWT.READ_ONLY) != 0)
            textStyle |= SWT.READ_ONLY;
        if ((style & SWT.FLAT) != 0)
            textStyle |= SWT.FLAT;
        text = new Text(this, textStyle);
        int arrowStyle = SWT.ARROW | SWT.DOWN;
        if ((style & SWT.FLAT) != 0)
            arrowStyle |= SWT.FLAT;
        arrow = new Button(this, arrowStyle);

        listener = event -> {
            if (isDisposed())
                return;
            if (popup == event.widget) {
                popupEvent(event);
                return;
            }
            if (text == event.widget) {
                textEvent(event);
                return;
            }
            if (list == event.widget) {
                listEvent(event);
                return;
            }
            if (arrow == event.widget) {
                arrowEvent(event);
                return;
            }
            if (CCombo.this == event.widget) {
                comboEvent(event);
                return;
            }
            if (getShell() == event.widget) {
                getDisplay().asyncExec(() -> {
                    if (isDisposed())
                        return;
                    handleFocus(SWT.FocusOut);
                });
            }
        };
        filter = event -> {
            if (isDisposed())
                return;
            if (event.type == SWT.Selection) {
                if (event.widget instanceof ScrollBar) {
                    handleScroll(event);
                }
                return;
            }
            Shell shell = ((Control) event.widget).getShell();
            if (shell == CCombo.this.getShell()) {
                handleFocus(SWT.FocusOut);
            }
        };

        int[] comboEvents = { SWT.Dispose, SWT.FocusIn, SWT.Move, SWT.Resize, SWT.FocusOut };
        for (int i = 0; i < comboEvents.length; i++)
            this.addListener(comboEvents[i], listener);

        int[] textEvents = { SWT.DefaultSelection, SWT.DragDetect, SWT.KeyDown, SWT.KeyUp, SWT.MenuDetect,
                SWT.Modify, SWT.MouseDown, SWT.MouseUp, SWT.MouseDoubleClick, SWT.MouseEnter, SWT.MouseExit,
                SWT.MouseHover, SWT.MouseMove, SWT.MouseWheel, SWT.Traverse, SWT.FocusIn, SWT.Verify };
        for (int i = 0; i < textEvents.length; i++)
            text.addListener(textEvents[i], listener);

        int[] arrowEvents = { SWT.DragDetect, SWT.MouseDown, SWT.MouseEnter, SWT.MouseExit, SWT.MouseHover,
                SWT.MouseMove, SWT.MouseUp, SWT.MouseWheel, SWT.Selection, SWT.FocusIn };
        for (int i = 0; i < arrowEvents.length; i++)
            arrow.addListener(arrowEvents[i], listener);

        createPopup(null, -1);
        if ((style & SWT.SIMPLE) == 0) {
            int itemHeight = list.getItemHeight();
            if (itemHeight != 0) {
                int maxHeight = getMonitor().getClientArea().height / 3;
                visibleItemCount = Math.max(visibleItemCount, maxHeight / itemHeight);
            }
        }

        initAccessible();
    }

    static int checkStyle(int style) {
        int mask = SWT.BORDER | SWT.READ_ONLY | SWT.FLAT | SWT.LEFT_TO_RIGHT | SWT.RIGHT_TO_LEFT;
        return SWT.NO_FOCUS | (style & mask);
    }

    /**
     * Adds the argument to the end of the receiver's list.
     * <p>
     * Note: If control characters like '\n', '\t' etc. are used
     * in the string, then the behavior is platform dependent.
     * </p>
     * @param string the new item
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the string 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 #add(String,int)
     */
    public void add(String string) {
        checkWidget();
        if (string == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        list.add(string);
    }

    /**
     * Adds the argument to the receiver's list at the given
     * zero-relative index.
     * <p>
     * Note: To add an item at the end of the list, use the
     * result of calling <code>getItemCount()</code> as the
     * index or use <code>add(String)</code>.
     * </p><p>
     * Also note, if control characters like '\n', '\t' etc. are used
     * in the string, then the behavior is platform dependent.
     * </p>
     *
     * @param string the new item
     * @param index the index for the item
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the string is null</li>
     *    <li>ERROR_INVALID_RANGE - if the index is not between 0 and the number of elements in the list (inclusive)</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 #add(String)
     */
    public void add(String string, int index) {
        checkWidget();
        if (string == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        list.add(string, index);
    }

    /**
     * Adds the listener to the collection of listeners who will
     * be notified when the receiver's text is modified, by sending
     * it one of the messages defined in the <code>ModifyListener</code>
     * interface.
     *
     * @param listener the listener which should be notified
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
     *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
     * </ul>
     *
     * @see ModifyListener
     * @see #removeModifyListener
     */
    public void addModifyListener(ModifyListener listener) {
        checkWidget();
        if (listener == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        TypedListener typedListener = new TypedListener(listener);
        addListener(SWT.Modify, typedListener);
    }

    /**
     * Adds the listener to the collection of listeners who will
     * be notified when the user changes the receiver's selection, by sending
     * it one of the messages defined in the <code>SelectionListener</code>
     * interface.
     * <p>
     * <code>widgetSelected</code> is called when the combo's list selection changes.
     * <code>widgetDefaultSelected</code> is typically called when ENTER is pressed the combo's text area.
     * </p>
     *
     * @param listener the listener which should be notified when the user changes the receiver's selection
     *
     * @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 SelectionListener
     * @see #removeSelectionListener
     * @see SelectionEvent
     */
    public void addSelectionListener(SelectionListener listener) {
        checkWidget();
        if (listener == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        TypedListener typedListener = new TypedListener(listener);
        addListener(SWT.Selection, typedListener);
        addListener(SWT.DefaultSelection, typedListener);
    }

    /**
     * Adds the listener to the collection of listeners who will
     * be notified when the receiver's text is verified, by sending
     * it one of the messages defined in the <code>VerifyListener</code>
     * interface.
     *
     * @param listener the listener which should be notified
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
     *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
     * </ul>
     *
     * @see VerifyListener
     * @see #removeVerifyListener
     *
     * @since 3.3
     */
    public void addVerifyListener(VerifyListener listener) {
        checkWidget();
        if (listener == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        TypedListener typedListener = new TypedListener(listener);
        addListener(SWT.Verify, typedListener);
    }

    void arrowEvent(Event event) {
        switch (event.type) {
        case SWT.FocusIn: {
            handleFocus(SWT.FocusIn);
            break;
        }
        case SWT.DragDetect:
        case SWT.MouseDown:
        case SWT.MouseUp:
        case SWT.MouseMove:
        case SWT.MouseEnter:
        case SWT.MouseExit:
        case SWT.MouseHover: {
            Point pt = getDisplay().map(arrow, this, event.x, event.y);
            event.x = pt.x;
            event.y = pt.y;
            notifyListeners(event.type, event);
            event.type = SWT.None;
            break;
        }
        case SWT.MouseWheel: {
            Point pt = getDisplay().map(arrow, this, event.x, event.y);
            event.x = pt.x;
            event.y = pt.y;
            notifyListeners(SWT.MouseWheel, event);
            event.type = SWT.None;
            if (isDisposed())
                break;
            if (!event.doit)
                break;
            if (event.count != 0) {
                event.doit = false;
                int oldIndex = getSelectionIndex();
                if (event.count > 0) {
                    select(Math.max(oldIndex - 1, 0));
                } else {
                    select(Math.min(oldIndex + 1, getItemCount() - 1));
                }
                if (oldIndex != getSelectionIndex()) {
                    Event e = new Event();
                    e.time = event.time;
                    e.stateMask = event.stateMask;
                    notifyListeners(SWT.Selection, e);
                }
                if (isDisposed())
                    break;
            }
            break;
        }
        case SWT.Selection: {
            text.setFocus();
            dropDown(!isDropped());
            break;
        }
        }
    }

    @Override
    protected void checkSubclass() {
        String name = getClass().getName();
        int index = name.lastIndexOf('.');
        if (!name.substring(0, index + 1).equals(PACKAGE_PREFIX)) {
            SWT.error(SWT.ERROR_INVALID_SUBCLASS);
        }
    }

    /**
     * Sets the selection in the receiver's text field to an empty
     * selection starting just before the first character. If the
     * text field is editable, this has the effect of placing the
     * i-beam at the start of the text.
     * <p>
     * Note: To clear the selected items in the receiver's list,
     * use <code>deselectAll()</code>.
     * </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>
     *
     * @see #deselectAll
     */
    public void clearSelection() {
        checkWidget();
        text.clearSelection();
        list.deselectAll();
    }

    void comboEvent(Event event) {
        switch (event.type) {
        case SWT.Dispose:
            removeListener(SWT.Dispose, listener);
            notifyListeners(SWT.Dispose, event);
            event.type = SWT.None;

            if (popup != null && !popup.isDisposed()) {
                list.removeListener(SWT.Dispose, listener);
                popup.dispose();
            }
            Shell shell = getShell();
            shell.removeListener(SWT.Deactivate, listener);
            Display display = getDisplay();
            display.removeFilter(SWT.FocusIn, filter);
            popup = null;
            text = null;
            list = null;
            arrow = null;
            _shell = null;
            break;
        case SWT.FocusIn:
            Control focusControl = getDisplay().getFocusControl();
            if (focusControl == arrow || focusControl == list)
                return;
            if (isDropped()) {
                list.setFocus();
            } else {
                text.setFocus();
            }
            break;
        case SWT.FocusOut:
            text.clearSelection();
            break;
        case SWT.Move:
            dropDown(false);
            break;
        case SWT.Resize:
            internalLayout(false);
            break;
        }
    }

    @Override
    public Point computeSize(int wHint, int hHint, boolean changed) {
        checkWidget();
        int width = 0, height = 0;
        String[] items = list.getItems();
        GC gc = new GC(text);
        int spacer = gc.stringExtent(" ").x; //$NON-NLS-1$
        int textWidth = gc.stringExtent(text.getText()).x;
        for (int i = 0; i < items.length; i++) {
            textWidth = Math.max(gc.stringExtent(items[i]).x, textWidth);
        }
        gc.dispose();
        Point textSize = text.computeSize(SWT.DEFAULT, SWT.DEFAULT, changed);
        Point arrowSize = arrow.computeSize(SWT.DEFAULT, SWT.DEFAULT, changed);
        Point listSize = list.computeSize(SWT.DEFAULT, SWT.DEFAULT, changed);
        int borderWidth = getBorderWidth();

        height = Math.max(textSize.y, arrowSize.y);
        width = Math.max(textWidth + 2 * spacer + arrowSize.x + 2 * borderWidth, listSize.x);
        if (wHint != SWT.DEFAULT)
            width = wHint;
        if (hHint != SWT.DEFAULT)
            height = hHint;
        return new Point(width + 2 * borderWidth, height + 2 * borderWidth);
    }

    /**
     * Copies the selected text.
     * <p>
     * The current selection is copied to the clipboard.
     * </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>
     *
     * @since 3.3
     */
    public void copy() {
        checkWidget();
        text.copy();
    }

    void createPopup(String[] items, int selectionIndex) {
        // create shell and list
        popup = new Shell(getShell(), SWT.NO_TRIM | SWT.ON_TOP);
        int style = getStyle();
        int listStyle = SWT.SINGLE | SWT.V_SCROLL | SWT.H_SCROLL;
        if ((style & SWT.FLAT) != 0)
            listStyle |= SWT.FLAT;
        if ((style & SWT.RIGHT_TO_LEFT) != 0)
            listStyle |= SWT.RIGHT_TO_LEFT;
        if ((style & SWT.LEFT_TO_RIGHT) != 0)
            listStyle |= SWT.LEFT_TO_RIGHT;
        list = new List(popup, listStyle);
        if (font != null)
            list.setFont(font);
        if (foreground != null)
            list.setForeground(foreground);
        if (background != null)
            list.setBackground(background);

        int[] popupEvents = { SWT.Close, SWT.Paint };
        for (int i = 0; i < popupEvents.length; i++)
            popup.addListener(popupEvents[i], listener);
        int[] listEvents = { SWT.MouseUp, SWT.Selection, SWT.Traverse, SWT.KeyDown, SWT.KeyUp, SWT.FocusIn,
                SWT.FocusOut, SWT.Dispose };
        for (int i = 0; i < listEvents.length; i++)
            list.addListener(listEvents[i], listener);

        if (items != null)
            list.setItems(items);
        if (selectionIndex != -1)
            list.setSelection(selectionIndex);
    }

    /**
     * Cuts the selected text.
     * <p>
     * The current selection is first copied to the
     * clipboard and then deleted from the widget.
     * </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>
     *
     * @since 3.3
     */
    public void cut() {
        checkWidget();
        text.cut();
    }

    /**
     * Deselects the item at the given zero-relative index in the receiver's
     * list.  If the item at the index was already deselected, it remains
     * deselected. Indices that are out of range are ignored.
     *
     * @param index the index of the item to deselect
     *
     * @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 void deselect(int index) {
        checkWidget();
        if (0 <= index && index < list.getItemCount() && index == list.getSelectionIndex()
                && text.getText().equals(list.getItem(index))) {
            text.setText(""); //$NON-NLS-1$
            list.deselect(index);
        }
    }

    /**
     * Deselects all selected items in the receiver's list.
     * <p>
     * Note: To clear the selection in the receiver's text field,
     * use <code>clearSelection()</code>.
     * </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>
     *
     * @see #clearSelection
     */
    public void deselectAll() {
        checkWidget();
        text.setText(""); //$NON-NLS-1$
        list.deselectAll();
    }

    void dropDown(boolean drop) {
        if (drop == isDropped())
            return;
        Display display = getDisplay();
        if (!drop) {
            display.removeFilter(SWT.Selection, filter);
            popup.setVisible(false);
            if (!isDisposed() && isFocusControl()) {
                text.setFocus();
            }
            return;
        }
        if (!isVisible())
            return;
        if (getShell() != popup.getParent()) {
            String[] items = list.getItems();
            int selectionIndex = list.getSelectionIndex();
            list.removeListener(SWT.Dispose, listener);
            popup.dispose();
            popup = null;
            list = null;
            createPopup(items, selectionIndex);
        }

        Point comboSize = getSize();
        int itemCount = list.getItemCount();
        itemCount = (itemCount == 0) ? visibleItemCount : Math.min(visibleItemCount, itemCount);
        int itemHeight = list.getItemHeight() * itemCount;
        Point listSize = list.computeSize(SWT.DEFAULT, itemHeight, false);
        Rectangle displayRect = getMonitor().getClientArea();
        list.setBounds(1, 1, Math.max(comboSize.x - 2, Math.min(listSize.x, displayRect.width - 2)), listSize.y);

        int index = list.getSelectionIndex();
        if (index != -1)
            list.setTopIndex(index);
        Rectangle listRect = list.getBounds();
        Rectangle parentRect = display.map(getParent(), null, getBounds());
        int width = listRect.width + 2;
        int height = listRect.height + 2;
        int x = parentRect.x;
        if (x + width > displayRect.x + displayRect.width) {
            x = displayRect.x + displayRect.width - width;
        }
        int y = parentRect.y + comboSize.y;
        if (y + height > displayRect.y + displayRect.height) {
            int popUpwardsHeight = (parentRect.y - height < displayRect.y) ? parentRect.y - displayRect.y : height;
            int popDownwardsHeight = displayRect.y + displayRect.height - y;
            if (popUpwardsHeight > popDownwardsHeight) {
                height = popUpwardsHeight;
                y = parentRect.y - popUpwardsHeight;
            } else {
                height = popDownwardsHeight;
            }
            listRect.height = height - 2;
        }
        /*
         * Invisible HScrollBar lead to empty space at end of CCombo drop-down.
         * Fix is to reduce height of list and shell in that case, bug 388126.
         */
        ScrollBar hBar = list.getHorizontalBar();
        int emptyHBarSpace = hBar.isVisible() ? 0 : hBar.getSize().y;
        list.setSize(listRect.width, listRect.height - emptyHBarSpace);
        popup.setBounds(x, y, width, height - emptyHBarSpace);
        popup.setVisible(true);
        if (isFocusControl())
            list.setFocus();

        /*
         * Add a filter to listen to scrolling of the parent composite, when the
         * drop-down is visible. Remove the filter when drop-down is not
         * visible.
         */
        display.removeFilter(SWT.Selection, filter);
        display.addFilter(SWT.Selection, filter);
    }

    /*
     * Return the lowercase of the first non-'&' character following
     * an '&' character in the given string. If there are no '&'
     * characters in the given string, return '\0'.
     */
    char _findMnemonic(String string) {
        if (string == null)
            return '\0';
        int index = 0;
        int length = string.length();
        do {
            while (index < length && string.charAt(index) != '&')
                index++;
            if (++index >= length)
                return '\0';
            if (string.charAt(index) != '&')
                return Character.toLowerCase(string.charAt(index));
            index++;
        } while (index < length);
        return '\0';
    }

    /*
     * Return the Label immediately preceding the receiver in the z-order,
     * or null if none.
     */
    String getAssociatedLabel() {
        Control[] siblings = getParent().getChildren();
        for (int i = 0; i < siblings.length; i++) {
            if (siblings[i] == this) {
                if (i > 0) {
                    Control sibling = siblings[i - 1];
                    if (sibling instanceof Label)
                        return ((Label) sibling).getText();
                    if (sibling instanceof CLabel)
                        return ((CLabel) sibling).getText();
                }
                break;
            }
        }
        return null;
    }

    @Override
    public Control[] getChildren() {
        checkWidget();
        return new Control[0];
    }

    /**
     * Gets the editable state.
     *
     * @return whether or not the receiver is editable
     *
     * @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 3.0
     */
    public boolean getEditable() {
        checkWidget();
        return text.getEditable();
    }

    /**
     * Returns the item at the given, zero-relative index in the
     * receiver's list. Throws an exception if the index is out
     * of range.
     *
     * @param index the index of the item to return
     * @return the item at the given index
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_INVALID_RANGE - if the index is not between 0 and the number of elements in the list minus 1 (inclusive)</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>
     */
    public String getItem(int index) {
        checkWidget();
        return list.getItem(index);
    }

    /**
     * Returns the number of items contained in the receiver's list.
     *
     * @return the number of items
     *
     * @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 getItemCount() {
        checkWidget();
        return list.getItemCount();
    }

    /**
     * Returns the height of the area which would be used to
     * display <em>one</em> of the items in the receiver's list.
     *
     * @return the height of one item
     *
     * @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 getItemHeight() {
        checkWidget();
        return list.getItemHeight();
    }

    /**
     * Returns an array of <code>String</code>s which are the items
     * in the receiver's list.
     * <p>
     * Note: This is not the actual structure used by the receiver
     * to maintain its list of items, so modifying the array will
     * not affect the receiver.
     * </p>
     *
     * @return the items in the receiver's list
     *
     * @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 String[] getItems() {
        checkWidget();
        return list.getItems();
    }

    /**
     * Returns <code>true</code> if the receiver's list is visible,
     * and <code>false</code> otherwise.
     * <p>
     * If one of the receiver's ancestors is not visible or some
     * other condition makes the receiver not visible, this method
     * may still indicate that it is considered visible even though
     * it may not actually be showing.
     * </p>
     *
     * @return the receiver's list's visibility state
     *
     * @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 3.4
     */
    public boolean getListVisible() {
        checkWidget();
        return isDropped();
    }

    @Override
    public Menu getMenu() {
        return text.getMenu();
    }

    /**
     * Returns a <code>Point</code> whose x coordinate is the start
     * of the selection in the receiver's text field, and whose y
     * coordinate is the end of the selection. The returned values
     * are zero-relative. An "empty" selection as indicated by
     * the the x and y coordinates having the same value.
     *
     * @return a point representing the selection start and end
     *
     * @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 Point getSelection() {
        checkWidget();
        return text.getSelection();
    }

    /**
     * Returns the zero-relative index of the item which is currently
     * selected in the receiver's list, or -1 if no item is selected.
     *
     * @return the index of the selected item
     *
     * @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 getSelectionIndex() {
        checkWidget();
        return list.getSelectionIndex();
    }

    @Override
    public Shell getShell() {
        checkWidget();
        Shell shell = super.getShell();
        if (shell != _shell) {
            if (_shell != null && !_shell.isDisposed()) {
                _shell.removeListener(SWT.Deactivate, listener);
            }
            _shell = shell;
        }
        return _shell;
    }

    @Override
    public int getStyle() {
        int style = super.getStyle();
        style &= ~SWT.READ_ONLY;
        if (!text.getEditable())
            style |= SWT.READ_ONLY;
        return style;
    }

    /**
     * Returns a string containing a copy of the contents of the
     * receiver's text field.
     *
     * @return the receiver's text
     *
     * @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 String getText() {
        checkWidget();
        return text.getText();
    }

    /**
     * Returns the height of the receivers's text field.
     *
     * @return the text height
     *
     * @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 getTextHeight() {
        checkWidget();
        return text.getLineHeight();
    }

    /**
     * Returns the maximum number of characters that the receiver's
     * text field is capable of holding. If this has not been changed
     * by <code>setTextLimit()</code>, it will be the constant
     * <code>Combo.LIMIT</code>.
     *
     * @return the text limit
     *
     * @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 getTextLimit() {
        checkWidget();
        return text.getTextLimit();
    }

    /**
     * Gets the number of items that are visible in the drop
     * down portion of the receiver's list.
     *
     * @return the number of items that are visible
     *
     * @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 3.0
     */
    public int getVisibleItemCount() {
        checkWidget();
        return visibleItemCount;
    }

    void handleFocus(int type) {
        switch (type) {
        case SWT.FocusIn: {
            if (hasFocus)
                return;
            if (getEditable())
                text.selectAll();
            hasFocus = true;
            Shell shell = getShell();
            shell.removeListener(SWT.Deactivate, listener);
            shell.addListener(SWT.Deactivate, listener);
            Display display = getDisplay();
            display.removeFilter(SWT.FocusIn, filter);
            display.addFilter(SWT.FocusIn, filter);
            Event e = new Event();
            notifyListeners(SWT.FocusIn, e);
            break;
        }
        case SWT.FocusOut: {
            if (!hasFocus)
                return;
            Control focusControl = getDisplay().getFocusControl();
            if (focusControl == arrow || focusControl == list || focusControl == text)
                return;
            hasFocus = false;
            Shell shell = getShell();
            shell.removeListener(SWT.Deactivate, listener);
            Display display = getDisplay();
            display.removeFilter(SWT.FocusIn, filter);
            Event e = new Event();
            notifyListeners(SWT.FocusOut, e);
            break;
        }
        }
    }

    void handleScroll(Event event) {
        ScrollBar scrollBar = (ScrollBar) event.widget;
        Control scrollableParent = scrollBar.getParent();
        if (scrollableParent.equals(list))
            return;
        if (isParentScrolling(scrollableParent))
            dropDown(false);
    }

    /**
     * Searches the receiver's list starting at the first item
     * (index 0) until an item is found that is equal to the
     * argument, and returns the index of that item. If no item
     * is found, returns -1.
     *
     * @param string the search item
     * @return the index of the item
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the string 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>
     */
    public int indexOf(String string) {
        checkWidget();
        if (string == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        return list.indexOf(string);
    }

    /**
     * Searches the receiver's list starting at the given,
     * zero-relative index until an item is found that is equal
     * to the argument, and returns the index of that item. If
     * no item is found or the starting index is out of range,
     * returns -1.
     *
     * @param string the search item
     * @param start the zero-relative index at which to begin the search
     * @return the index of the item
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the string 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>
     */
    public int indexOf(String string, int start) {
        checkWidget();
        if (string == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        return list.indexOf(string, start);
    }

    void initAccessible() {
        AccessibleAdapter accessibleAdapter = new AccessibleAdapter() {
            @Override
            public void getName(AccessibleEvent e) {
                String name = null;
                String text = getAssociatedLabel();
                if (text != null) {
                    name = stripMnemonic(text);
                }
                e.result = name;
            }

            @Override
            public void getKeyboardShortcut(AccessibleEvent e) {
                String shortcut = null;
                String text = getAssociatedLabel();
                if (text != null) {
                    char mnemonic = _findMnemonic(text);
                    if (mnemonic != '\0') {
                        shortcut = "Alt+" + mnemonic; //$NON-NLS-1$
                    }
                }
                e.result = shortcut;
            }

            @Override
            public void getHelp(AccessibleEvent e) {
                e.result = getToolTipText();
            }
        };
        getAccessible().addAccessibleListener(accessibleAdapter);
        text.getAccessible().addAccessibleListener(accessibleAdapter);
        list.getAccessible().addAccessibleListener(accessibleAdapter);

        arrow.getAccessible().addAccessibleListener(new AccessibleAdapter() {
            @Override
            public void getName(AccessibleEvent e) {
                e.result = isDropped() ? SWT.getMessage("SWT_Close") : SWT.getMessage("SWT_Open"); //$NON-NLS-1$ //$NON-NLS-2$
            }

            @Override
            public void getKeyboardShortcut(AccessibleEvent e) {
                e.result = "Alt+Down Arrow"; //$NON-NLS-1$
            }

            @Override
            public void getHelp(AccessibleEvent e) {
                e.result = getToolTipText();
            }
        });

        getAccessible().addAccessibleTextListener(new AccessibleTextAdapter() {
            @Override
            public void getCaretOffset(AccessibleTextEvent e) {
                e.offset = text.getCaretPosition();
            }

            @Override
            public void getSelectionRange(AccessibleTextEvent e) {
                Point sel = text.getSelection();
                e.offset = sel.x;
                e.length = sel.y - sel.x;
            }
        });

        getAccessible().addAccessibleControlListener(new AccessibleControlAdapter() {
            @Override
            public void getChildAtPoint(AccessibleControlEvent e) {
                Point testPoint = toControl(e.x, e.y);
                if (getBounds().contains(testPoint)) {
                    e.childID = ACC.CHILDID_SELF;
                }
            }

            @Override
            public void getLocation(AccessibleControlEvent e) {
                Rectangle location = getBounds();
                Point pt = getParent().toDisplay(location.x, location.y);
                e.x = pt.x;
                e.y = pt.y;
                e.width = location.width;
                e.height = location.height;
            }

            @Override
            public void getChildCount(AccessibleControlEvent e) {
                e.detail = 0;
            }

            @Override
            public void getRole(AccessibleControlEvent e) {
                e.detail = ACC.ROLE_COMBOBOX;
            }

            @Override
            public void getState(AccessibleControlEvent e) {
                e.detail = ACC.STATE_NORMAL;
            }

            @Override
            public void getValue(AccessibleControlEvent e) {
                e.result = getText();
            }
        });

        text.getAccessible().addAccessibleControlListener(new AccessibleControlAdapter() {
            @Override
            public void getRole(AccessibleControlEvent e) {
                e.detail = text.getEditable() ? ACC.ROLE_TEXT : ACC.ROLE_LABEL;
            }
        });

        arrow.getAccessible().addAccessibleControlListener(new AccessibleControlAdapter() {
            @Override
            public void getDefaultAction(AccessibleControlEvent e) {
                e.result = isDropped() ? SWT.getMessage("SWT_Close") : SWT.getMessage("SWT_Open"); //$NON-NLS-1$ //$NON-NLS-2$
            }
        });
    }

    boolean isDropped() {
        return !isDisposed() && popup.getVisible();
    }

    @Override
    public boolean isFocusControl() {
        checkWidget();
        Predicate<Control> checkFocusControl = (
                control) -> (control != null && !control.isDisposed() && control.isFocusControl());
        if (checkFocusControl.test(text) || checkFocusControl.test(arrow) || checkFocusControl.test(list)
                || checkFocusControl.test(popup)) {
            return true;
        }
        return super.isFocusControl();
    }

    boolean isParentScrolling(Control scrollableParent) {
        Control parent = this.getParent();
        while (parent != null) {
            if (parent.equals(scrollableParent))
                return true;
            parent = parent.getParent();
        }
        return false;
    }

    void internalLayout(boolean changed) {
        if (isDropped())
            dropDown(false);
        Rectangle rect = getClientArea();
        int width = rect.width;
        int height = rect.height;
        Point arrowSize = arrow.computeSize(SWT.DEFAULT, height, changed);
        text.setBounds(0, 0, width - arrowSize.x, height);
        arrow.setBounds(width - arrowSize.x, 0, arrowSize.x, arrowSize.y);
    }

    void listEvent(Event event) {
        switch (event.type) {
        case SWT.Dispose:
            if (getShell() != popup.getParent()) {
                String[] items = list.getItems();
                int selectionIndex = list.getSelectionIndex();
                popup = null;
                list = null;
                createPopup(items, selectionIndex);
            }
            break;
        case SWT.FocusIn: {
            handleFocus(SWT.FocusIn);
            break;
        }
        case SWT.FocusOut: {
            /*
             * Behavior in Windows, GTK & Cocoa: When the arrow button is pressed
             * with the popup list visible, the following events are received-
             * popup control receives a deactivate event,
             * list receives focus lost event, and then
             * arrow button receives a selection event.
             * If we hide the popup in the focus out event, the selection event will
             * show it again. To prevent the popup from showing again, we will detect
             * this case and let the selection event of the arrow button hide the popup.
             */
            Point point = arrow.toControl(getDisplay().getCursorLocation());
            Point size = arrow.getSize();
            Rectangle rect = new Rectangle(0, 0, size.x, size.y);
            if (rect.contains(point)) {
                boolean comboShellActivated = getDisplay().getActiveShell() == getShell();
                if (!comboShellActivated)
                    dropDown(false);
                break;
            }
            dropDown(false);
            break;
        }
        case SWT.MouseUp: {
            if (event.button != 1)
                return;
            dropDown(false);
            break;
        }
        case SWT.Selection: {
            int index = list.getSelectionIndex();
            if (index == -1)
                return;
            text.setText(list.getItem(index));
            if (text.getEditable() && text.isFocusControl())
                text.selectAll();
            list.setSelection(index);
            Event e = new Event();
            e.time = event.time;
            e.stateMask = event.stateMask;
            e.doit = event.doit;
            notifyListeners(SWT.Selection, e);
            event.doit = e.doit;
            break;
        }
        case SWT.Traverse: {
            switch (event.detail) {
            case SWT.TRAVERSE_RETURN:
            case SWT.TRAVERSE_ESCAPE:
            case SWT.TRAVERSE_ARROW_PREVIOUS:
            case SWT.TRAVERSE_ARROW_NEXT:
                event.doit = false;
                break;
            case SWT.TRAVERSE_TAB_NEXT:
            case SWT.TRAVERSE_TAB_PREVIOUS:
                event.doit = text.traverse(event.detail);
                event.detail = SWT.TRAVERSE_NONE;
                if (event.doit)
                    dropDown(false);
                return;
            }
            Event e = new Event();
            e.time = event.time;
            e.detail = event.detail;
            e.doit = event.doit;
            e.character = event.character;
            e.keyCode = event.keyCode;
            e.keyLocation = event.keyLocation;
            notifyListeners(SWT.Traverse, e);
            event.doit = e.doit;
            event.detail = e.detail;
            break;
        }
        case SWT.KeyUp: {
            Event e = new Event();
            e.time = event.time;
            e.character = event.character;
            e.keyCode = event.keyCode;
            e.keyLocation = event.keyLocation;
            e.stateMask = event.stateMask;
            notifyListeners(SWT.KeyUp, e);
            event.doit = e.doit;
            break;
        }
        case SWT.KeyDown: {
            if (event.character == SWT.ESC) {
                // Escape key cancels popup list
                dropDown(false);
            }
            if ((event.stateMask & SWT.ALT) != 0
                    && (event.keyCode == SWT.ARROW_UP || event.keyCode == SWT.ARROW_DOWN)) {
                dropDown(false);
            }
            if (event.character == SWT.CR) {
                // Enter causes default selection
                dropDown(false);
                Event e = new Event();
                e.time = event.time;
                e.stateMask = event.stateMask;
                notifyListeners(SWT.DefaultSelection, e);
            }
            // At this point the widget may have been disposed.
            // If so, do not continue.
            if (isDisposed())
                break;
            Event e = new Event();
            e.time = event.time;
            e.character = event.character;
            e.keyCode = event.keyCode;
            e.keyLocation = event.keyLocation;
            e.stateMask = event.stateMask;
            notifyListeners(SWT.KeyDown, e);
            event.doit = e.doit;
            break;

        }
        }
    }

    /**
     * Pastes text from clipboard.
     * <p>
     * The selected text is deleted from the widget
     * and new text inserted from the clipboard.
     * </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>
     *
     * @since 3.3
     */
    public void paste() {
        checkWidget();
        text.paste();
    }

    void popupEvent(Event event) {
        switch (event.type) {
        case SWT.Paint:
            // draw black rectangle around list
            Rectangle listRect = list.getBounds();
            Color black = getDisplay().getSystemColor(SWT.COLOR_BLACK);
            event.gc.setForeground(black);
            event.gc.drawRectangle(0, 0, listRect.width + 1, listRect.height + 1);
            break;
        case SWT.Close:
            event.doit = false;
            dropDown(false);
            break;
        }
    }

    @Override
    public void redraw() {
        super.redraw();
        text.redraw();
        arrow.redraw();
        if (popup.isVisible())
            list.redraw();
    }

    @Override
    public void redraw(int x, int y, int width, int height, boolean all) {
        super.redraw(x, y, width, height, true);
    }

    /**
     * Removes the item from the receiver's list at the given
     * zero-relative index.
     *
     * @param index the index for the item
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_INVALID_RANGE - if the index is not between 0 and the number of elements in the list minus 1 (inclusive)</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>
     */
    public void remove(int index) {
        checkWidget();
        list.remove(index);
    }

    /**
     * Removes the items from the receiver's list which are
     * between the given zero-relative start and end
     * indices (inclusive).
     *
     * @param start the start of the range
     * @param end the end of the range
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_INVALID_RANGE - if either the start or end are not between 0 and the number of elements in the list minus 1 (inclusive)</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>
     */
    public void remove(int start, int end) {
        checkWidget();
        list.remove(start, end);
    }

    /**
     * Searches the receiver's list starting at the first item
     * until an item is found that is equal to the argument,
     * and removes that item from the list.
     *
     * @param string the item to remove
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the string is null</li>
     *    <li>ERROR_INVALID_ARGUMENT - if the string is not found in the list</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>
     */
    public void remove(String string) {
        checkWidget();
        if (string == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        list.remove(string);
    }

    /**
     * Removes all of the items from the receiver's list and clear the
     * contents of receiver's text field.
     *
     * @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 void removeAll() {
        checkWidget();
        text.setText(""); //$NON-NLS-1$
        list.removeAll();
    }

    /**
     * Removes the listener from the collection of listeners who will
     * be notified when the receiver's text is modified.
     *
     * @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 ModifyListener
     * @see #addModifyListener
     */
    public void removeModifyListener(ModifyListener listener) {
        checkWidget();
        if (listener == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        removeListener(SWT.Modify, listener);
    }

    /**
     * Removes the listener from the collection of listeners who will
     * be notified when the user changes the receiver's selection.
     *
     * @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 SelectionListener
     * @see #addSelectionListener
     */
    public void removeSelectionListener(SelectionListener listener) {
        checkWidget();
        if (listener == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        removeListener(SWT.Selection, listener);
        removeListener(SWT.DefaultSelection, listener);
    }

    /**
     * Removes the listener from the collection of listeners who will
     * be notified when the control is verified.
     *
     * @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 VerifyListener
     * @see #addVerifyListener
     *
     * @since 3.3
     */
    public void removeVerifyListener(VerifyListener listener) {
        checkWidget();
        if (listener == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        removeListener(SWT.Verify, listener);
    }

    /**
     * Selects the item at the given zero-relative index in the receiver's
     * list.  If the item at the index was already selected, it remains
     * selected. Indices that are out of range are ignored.
     *
     * @param index the index of the item to select
     *
     * @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 void select(int index) {
        checkWidget();
        if (index == -1) {
            list.deselectAll();
            text.setText(""); //$NON-NLS-1$
            return;
        }
        if (0 <= index && index < list.getItemCount()) {
            if (index != getSelectionIndex()) {
                text.setText(list.getItem(index));
                if (text.getEditable() && text.isFocusControl())
                    text.selectAll();
                list.select(index);
                list.showSelection();
            }
        }
    }

    @Override
    public void setBackground(Color color) {
        super.setBackground(color);
        background = color;
        if (text != null)
            text.setBackground(color);
        if (list != null)
            list.setBackground(color);
        if (arrow != null)
            arrow.setBackground(color);
    }

    /**
     * Sets the editable state.
     *
     * @param editable the new editable state
     *
     * @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 3.0
     */
    public void setEditable(boolean editable) {
        checkWidget();
        text.setEditable(editable);
    }

    @Override
    public void setEnabled(boolean enabled) {
        super.setEnabled(enabled);
        if (popup != null)
            popup.setVisible(false);
        if (text != null)
            text.setEnabled(enabled);
        if (arrow != null)
            arrow.setEnabled(enabled);
    }

    @Override
    public boolean setFocus() {
        checkWidget();
        if (!isEnabled() || !getVisible())
            return false;
        if (isFocusControl())
            return true;
        return text.setFocus();
    }

    @Override
    public void setFont(Font font) {
        super.setFont(font);
        this.font = font;
        text.setFont(font);
        list.setFont(font);
        internalLayout(true);
    }

    @Override
    public void setForeground(Color color) {
        super.setForeground(color);
        foreground = color;
        if (text != null)
            text.setForeground(color);
        if (list != null)
            list.setForeground(color);
        if (arrow != null)
            arrow.setForeground(color);
    }

    /**
     * Sets the text of the item in the receiver's list at the given
     * zero-relative index to the string argument. This is equivalent
     * to <code>remove</code>'ing the old item at the index, and then
     * <code>add</code>'ing the new item at that index.
     *
     * @param index the index for the item
     * @param string the new text for the item
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_INVALID_RANGE - if the index is not between 0 and the number of elements in the list minus 1 (inclusive)</li>
     *    <li>ERROR_NULL_ARGUMENT - if the string 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>
     */
    public void setItem(int index, String string) {
        checkWidget();
        list.setItem(index, string);
    }

    /**
     * Sets the receiver's list to be the given array of items.
     *
     * @param items the array of items
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the items array is null</li>
     *    <li>ERROR_INVALID_ARGUMENT - if an item in the items array 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>
     */
    public void setItems(String[] items) {
        checkWidget();
        list.setItems(items);
        if (!text.getEditable())
            text.setText(""); //$NON-NLS-1$
    }

    /**
     * Sets the layout which is associated with the receiver to be
     * the argument which may be null.
     * <p>
     * Note: No Layout can be set on this Control because it already
     * manages the size and position of its children.
     * </p>
     *
     * @param layout the receiver's new layout or null
     *
     * @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>
     */
    @Override
    public void setLayout(Layout layout) {
        checkWidget();
        return;
    }

    /**
     * Marks the receiver's list as visible if the argument is <code>true</code>,
     * and marks it invisible otherwise.
     * <p>
     * If one of the receiver's ancestors is not visible or some
     * other condition makes the receiver not visible, marking
     * it visible may not actually cause it to be displayed.
     * </p>
     *
     * @param visible the new visibility state
     *
     * @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 3.4
     */
    public void setListVisible(boolean visible) {
        checkWidget();
        dropDown(visible);
    }

    @Override
    public void setMenu(Menu menu) {
        text.setMenu(menu);
    }

    /**
     * Sets the selection in the receiver's text field to the
     * range specified by the argument whose x coordinate is the
     * start of the selection and whose y coordinate is the end
     * of the selection.
     *
     * @param selection a point representing the new selection start and end
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the point 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>
     */
    public void setSelection(Point selection) {
        checkWidget();
        if (selection == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        text.setSelection(selection.x, selection.y);
    }

    /**
     * Sets the contents of the receiver's text field to the
     * given string.
     * <p>
     * Note: The text field in a <code>Combo</code> is typically
     * only capable of displaying a single line of text. Thus,
     * setting the text to a string containing line breaks or
     * other special characters will probably cause it to
     * display incorrectly.
     * </p><p>
     * Also note, if control characters like '\n', '\t' etc. are used
     * in the string, then the behavior is platform dependent.
     * </p>
     *
     * @param string the new text
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the string 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>
     */
    public void setText(String string) {
        checkWidget();
        if (string == null)
            SWT.error(SWT.ERROR_NULL_ARGUMENT);
        int index = list.indexOf(string);
        if (index == -1) {
            list.deselectAll();
            text.setText(string);
            return;
        }
        text.setText(string);
        if (text.getEditable() && text.isFocusControl())
            text.selectAll();
        list.setSelection(index);
        list.showSelection();
    }

    /**
     * Sets the maximum number of characters that the receiver's
     * text field is capable of holding to be the argument.
     *
     * @param limit new text limit
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_CANNOT_BE_ZERO - if the limit is zero</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>
     */
    public void setTextLimit(int limit) {
        checkWidget();
        text.setTextLimit(limit);
    }

    @Override
    public void setToolTipText(String string) {
        checkWidget();
        super.setToolTipText(string);
        arrow.setToolTipText(string);
        text.setToolTipText(string);
    }

    @Override
    public void setVisible(boolean visible) {
        super.setVisible(visible);
        /*
         * At this point the widget may have been disposed in a FocusOut event.
         * If so then do not continue.
         */
        if (isDisposed())
            return;
        // TEMPORARY CODE
        if (popup == null || popup.isDisposed())
            return;
        if (!visible)
            popup.setVisible(false);
    }

    /**
     * Sets the number of items that are visible in the drop
     * down portion of the receiver's list.
     *
     * @param count the new number of items to be visible
     *
     * @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 3.0
     */
    public void setVisibleItemCount(int count) {
        checkWidget();
        if (count < 0)
            return;
        visibleItemCount = count;
    }

    String stripMnemonic(String string) {
        int index = 0;
        int length = string.length();
        do {
            while ((index < length) && (string.charAt(index) != '&'))
                index++;
            if (++index >= length)
                return string;
            if (string.charAt(index) != '&') {
                return string.substring(0, index - 1) + string.substring(index, length);
            }
            index++;
        } while (index < length);
        return string;
    }

    void textEvent(Event event) {
        switch (event.type) {
        case SWT.FocusIn: {
            handleFocus(SWT.FocusIn);
            break;
        }
        case SWT.DefaultSelection: {
            dropDown(false);
            Event e = new Event();
            e.time = event.time;
            e.stateMask = event.stateMask;
            notifyListeners(SWT.DefaultSelection, e);
            break;
        }
        case SWT.DragDetect:
        case SWT.MouseDoubleClick:
        case SWT.MouseMove:
        case SWT.MouseEnter:
        case SWT.MouseExit:
        case SWT.MouseHover: {
            Point pt = getDisplay().map(text, this, event.x, event.y);
            event.x = pt.x;
            event.y = pt.y;
            notifyListeners(event.type, event);
            event.type = SWT.None;
            break;
        }
        case SWT.KeyDown: {
            Event keyEvent = new Event();
            keyEvent.time = event.time;
            keyEvent.character = event.character;
            keyEvent.keyCode = event.keyCode;
            keyEvent.keyLocation = event.keyLocation;
            keyEvent.stateMask = event.stateMask;
            notifyListeners(SWT.KeyDown, keyEvent);
            if (isDisposed())
                break;
            event.doit = keyEvent.doit;
            if (!event.doit)
                break;
            if (event.keyCode == SWT.ARROW_UP || event.keyCode == SWT.ARROW_DOWN) {
                event.doit = false;
                if ((event.stateMask & SWT.ALT) != 0) {
                    boolean dropped = isDropped();
                    if (text.getEditable() && text.isFocusControl())
                        text.selectAll();
                    if (!dropped)
                        setFocus();
                    dropDown(!dropped);
                    break;
                }

                int oldIndex = getSelectionIndex();
                if (event.keyCode == SWT.ARROW_UP) {
                    select(Math.max(oldIndex - 1, 0));
                } else {
                    select(Math.min(oldIndex + 1, getItemCount() - 1));
                }
                if (oldIndex != getSelectionIndex()) {
                    Event e = new Event();
                    e.time = event.time;
                    e.stateMask = event.stateMask;
                    notifyListeners(SWT.Selection, e);
                }
                if (isDisposed())
                    break;
            }

            // Further work : Need to add support for incremental search in
            // pop up list as characters typed in text widget
            break;
        }
        case SWT.KeyUp: {
            Event e = new Event();
            e.time = event.time;
            e.character = event.character;
            e.keyCode = event.keyCode;
            e.keyLocation = event.keyLocation;
            e.stateMask = event.stateMask;
            notifyListeners(SWT.KeyUp, e);
            event.doit = e.doit;
            break;
        }
        case SWT.MenuDetect: {
            Event e = new Event();
            e.time = event.time;
            e.detail = event.detail;
            e.x = event.x;
            e.y = event.y;
            if (event.detail == SWT.MENU_KEYBOARD) {
                Point pt = getDisplay().map(text, null, text.getCaretLocation());
                e.x = pt.x;
                e.y = pt.y;
            }
            notifyListeners(SWT.MenuDetect, e);
            event.doit = e.doit;
            event.x = e.x;
            event.y = e.y;
            break;
        }
        case SWT.Modify: {
            list.deselectAll();
            Event e = new Event();
            e.time = event.time;
            notifyListeners(SWT.Modify, e);
            break;
        }
        case SWT.MouseDown: {
            Point pt = getDisplay().map(text, this, event.x, event.y);
            Event mouseEvent = new Event();
            mouseEvent.button = event.button;
            mouseEvent.count = event.count;
            mouseEvent.stateMask = event.stateMask;
            mouseEvent.time = event.time;
            mouseEvent.x = pt.x;
            mouseEvent.y = pt.y;
            notifyListeners(SWT.MouseDown, mouseEvent);
            if (isDisposed())
                break;
            event.doit = mouseEvent.doit;
            if (!event.doit)
                break;
            if (event.button != 1)
                return;
            if (text.getEditable())
                return;
            boolean dropped = isDropped();
            if (text.getEditable() && text.isFocusControl())
                text.selectAll();
            if (!dropped)
                setFocus();
            dropDown(!dropped);
            break;
        }
        case SWT.MouseUp: {
            Point pt = getDisplay().map(text, this, event.x, event.y);
            Event mouseEvent = new Event();
            mouseEvent.button = event.button;
            mouseEvent.count = event.count;
            mouseEvent.stateMask = event.stateMask;
            mouseEvent.time = event.time;
            mouseEvent.x = pt.x;
            mouseEvent.y = pt.y;
            notifyListeners(SWT.MouseUp, mouseEvent);
            if (isDisposed())
                break;
            event.doit = mouseEvent.doit;
            if (!event.doit)
                break;
            if (event.button != 1)
                return;
            if (text.getEditable())
                return;
            if (text.getEditable() && text.isFocusControl())
                text.selectAll();
            break;
        }
        case SWT.MouseWheel: {
            notifyListeners(SWT.MouseWheel, event);
            event.type = SWT.None;
            if (isDisposed())
                break;
            if (!event.doit)
                break;
            if (event.count != 0) {
                event.doit = false;
                int oldIndex = getSelectionIndex();
                if (event.count > 0) {
                    select(Math.max(oldIndex - 1, 0));
                } else {
                    select(Math.min(oldIndex + 1, getItemCount() - 1));
                }
                if (oldIndex != getSelectionIndex()) {
                    Event e = new Event();
                    e.time = event.time;
                    e.stateMask = event.stateMask;
                    notifyListeners(SWT.Selection, e);
                }
                if (isDisposed())
                    break;
            }
            break;
        }
        case SWT.Traverse: {
            switch (event.detail) {
            case SWT.TRAVERSE_ARROW_PREVIOUS:
            case SWT.TRAVERSE_ARROW_NEXT:
                // The enter causes default selection and
                // the arrow keys are used to manipulate the list contents so
                // do not use them for traversal.
                event.doit = false;
                break;
            case SWT.TRAVERSE_TAB_PREVIOUS:
                event.doit = traverse(SWT.TRAVERSE_TAB_PREVIOUS);
                event.detail = SWT.TRAVERSE_NONE;
                return;
            }
            Event e = new Event();
            e.time = event.time;
            e.detail = event.detail;
            e.doit = event.doit;
            e.character = event.character;
            e.keyCode = event.keyCode;
            e.keyLocation = event.keyLocation;
            notifyListeners(SWT.Traverse, e);
            event.doit = e.doit;
            event.detail = e.detail;
            break;
        }
        case SWT.Verify: {
            Event e = new Event();
            e.text = event.text;
            e.start = event.start;
            e.end = event.end;
            e.character = event.character;
            e.keyCode = event.keyCode;
            e.keyLocation = event.keyLocation;
            e.stateMask = event.stateMask;
            notifyListeners(SWT.Verify, e);
            event.text = e.text;
            event.doit = e.doit;
            break;
        }
        }
    }

    @Override
    public boolean traverse(int event) {
        /*
         * When the traverse event is sent to the CCombo, it will create a list of
         * controls to tab to next. Since the CCombo is a composite, the next control is
         * the Text field which is a child of the CCombo. It will set focus to the text
         * field which really is itself. So, call the traverse next events directly on the text.
         */
        if (event == SWT.TRAVERSE_ARROW_NEXT || event == SWT.TRAVERSE_TAB_NEXT) {
            return text.traverse(event);
        }
        return super.traverse(event);
    }
}