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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package javax.swing;

import java.awt.Component;

import java.awt.Container;

import java.awt.ComponentOrientation;

import java.util.Comparator;

import java.io.*;

import sun.awt.SunToolkit;

/**

 * A SortingFocusTraversalPolicy which sorts Components based on their size,

 * position, and orientation. Based on their size and position, Components are

 * roughly categorized into rows and columns. For a Container with horizontal

 * orientation, columns run left-to-right or right-to-left, and rows run top-

 * to-bottom. For a Container with vertical orientation, columns run top-to-

 * bottom and rows run left-to-right or right-to-left. See

 * <code>ComponentOrientation</code> for more information. All columns in a

 * row are fully traversed before proceeding to the next row.

 *

 * @author David Mendenhall

 *

 * @see java.awt.ComponentOrientation

 * @since 1.4

 */

public class LayoutFocusTraversalPolicy extends SortingFocusTraversalPolicy

    implements Serializable

{

    // Delegate most of our fitness test to Default so that we only have to

    // code the algorithm once.

    private static final SwingDefaultFocusTraversalPolicy fitnessTestPolicy =

        new SwingDefaultFocusTraversalPolicy();

    /**

     * Constructs a LayoutFocusTraversalPolicy.

     */

    public LayoutFocusTraversalPolicy() {

        super(new LayoutComparator());

    }

    /**

     * Constructs a LayoutFocusTraversalPolicy with the passed in

     * <code>Comparator</code>.

     */

    LayoutFocusTraversalPolicy(Comparator<? super Component> c) {

        super(c);

    }

    /**

     * Returns the Component that should receive the focus after aComponent.

     * aContainer must be a focus cycle root of aComponent.

     * <p>

     * By default, LayoutFocusTraversalPolicy implicitly transfers focus down-

     * cycle. That is, during normal focus traversal, the Component

     * traversed after a focus cycle root will be the focus-cycle-root's

     * default Component to focus. This behavior can be disabled using the

     * <code>setImplicitDownCycleTraversal</code> method.

     * <p>

     * If aContainer is <a href="../../java/awt/doc-files/FocusSpec.html#FocusTraversalPolicyProviders">focus

     * traversal policy provider</a>, the focus is always transferred down-cycle.

     *

     * @param aContainer a focus cycle root of aComponent or a focus traversal policy provider

     * @param aComponent a (possibly indirect) child of aContainer, or

     *        aContainer itself

     * @return the Component that should receive the focus after aComponent, or

     *         null if no suitable Component can be found

     * @throws IllegalArgumentException if aContainer is not a focus cycle

     *         root of aComponent or a focus traversal policy provider, or if either aContainer or

     *         aComponent is null

     */

    public Component getComponentAfter(Container aContainer,

                                       Component aComponent) {

        if (aContainer == null || aComponent == null) {

            throw new IllegalArgumentException("aContainer and aComponent cannot be null");

        }

        Comparator comparator = getComparator();

        if (comparator instanceof LayoutComparator) {

            ((LayoutComparator)comparator).

                setComponentOrientation(aContainer.

                                        getComponentOrientation());

        }

        return super.getComponentAfter(aContainer, aComponent);

    }

    /**

     * Returns the Component that should receive the focus before aComponent.

     * aContainer must be a focus cycle root of aComponent.

     * <p>

     * By default, LayoutFocusTraversalPolicy implicitly transfers focus down-

     * cycle. That is, during normal focus traversal, the Component

     * traversed after a focus cycle root will be the focus-cycle-root's

     * default Component to focus. This behavior can be disabled using the

     * <code>setImplicitDownCycleTraversal</code> method.

     * <p>

     * If aContainer is <a href="../../java/awt/doc-files/FocusSpec.html#FocusTraversalPolicyProviders">focus

     * traversal policy provider</a>, the focus is always transferred down-cycle.

     *

     * @param aContainer a focus cycle root of aComponent or a focus traversal policy provider

     * @param aComponent a (possibly indirect) child of aContainer, or

     *        aContainer itself

     * @return the Component that should receive the focus before aComponent,

     *         or null if no suitable Component can be found

     * @throws IllegalArgumentException if aContainer is not a focus cycle

     *         root of aComponent or a focus traversal policy provider, or if either aContainer or

     *         aComponent is null

     */

    public Component getComponentBefore(Container aContainer,

                                        Component aComponent) {

        if (aContainer == null || aComponent == null) {

            throw new IllegalArgumentException("aContainer and aComponent cannot be null");

        }

        Comparator comparator = getComparator();

        if (comparator instanceof LayoutComparator) {

            ((LayoutComparator)comparator).

                setComponentOrientation(aContainer.

                                        getComponentOrientation());

        }

        return super.getComponentBefore(aContainer, aComponent);

    }

    /**

     * Returns the first Component in the traversal cycle. This method is used

     * to determine the next Component to focus when traversal wraps in the

     * forward direction.

     *

     * @param aContainer a focus cycle root of aComponent or a focus traversal policy provider whose

     *        first Component is to be returned

     * @return the first Component in the traversal cycle of aContainer,

     *         or null if no suitable Component can be found

     * @throws IllegalArgumentException if aContainer is null

     */

    public Component getFirstComponent(Container aContainer) {

        if (aContainer == null) {

            throw new IllegalArgumentException("aContainer cannot be null");

        }

        Comparator comparator = getComparator();

        if (comparator instanceof LayoutComparator) {

            ((LayoutComparator)comparator).

                setComponentOrientation(aContainer.

                                        getComponentOrientation());

        }

        return super.getFirstComponent(aContainer);

    }

    /**

     * Returns the last Component in the traversal cycle. This method is used

     * to determine the next Component to focus when traversal wraps in the

     * reverse direction.

     *

     * @param aContainer a focus cycle root of aComponent or a focus traversal policy provider whose

     *        last Component is to be returned

     * @return the last Component in the traversal cycle of aContainer,

     *         or null if no suitable Component can be found

     * @throws IllegalArgumentException if aContainer is null

     */

    public Component getLastComponent(Container aContainer) {

        if (aContainer == null) {

            throw new IllegalArgumentException("aContainer cannot be null");

        }

        Comparator comparator = getComparator();

        if (comparator instanceof LayoutComparator) {

            ((LayoutComparator)comparator).

                setComponentOrientation(aContainer.

                                        getComponentOrientation());

        }

        return super.getLastComponent(aContainer);

    }

    /**

     * Determines whether the specified <code>Component</code>

     * is an acceptable choice as the new focus owner.

     * This method performs the following sequence of operations:

     * <ol>

     * <li>Checks whether <code>aComponent</code> is visible, displayable,

     *     enabled, and focusable.  If any of these properties is

     *     <code>false</code>, this method returns <code>false</code>.

     * <li>If <code>aComponent</code> is an instance of <code>JTable</code>,

     *     returns <code>true</code>.

     * <li>If <code>aComponent</code> is an instance of <code>JComboBox</code>,

     *     then returns the value of

     *     <code>aComponent.getUI().isFocusTraversable(aComponent)</code>.

     * <li>If <code>aComponent</code> is a <code>JComponent</code>

     *     with a <code>JComponent.WHEN_FOCUSED</code>

     *     <code>InputMap</code> that is neither <code>null</code>

     *     nor empty, returns <code>true</code>.

     * <li>Returns the value of

     *     <code>DefaultFocusTraversalPolicy.accept(aComponent)</code>.

     * </ol>

     *

     * @param aComponent the <code>Component</code> whose fitness

     *                   as a focus owner is to be tested

     * @see java.awt.Component#isVisible

     * @see java.awt.Component#isDisplayable

     * @see java.awt.Component#isEnabled

     * @see java.awt.Component#isFocusable

     * @see javax.swing.plaf.ComboBoxUI#isFocusTraversable

     * @see javax.swing.JComponent#getInputMap

     * @see java.awt.DefaultFocusTraversalPolicy#accept

     * @return <code>true</code> if <code>aComponent</code> is a valid choice

     *         for a focus owner;

     *         otherwise <code>false</code>

     */

     protected boolean accept(Component aComponent) {

        if (!super.accept(aComponent)) {

            return false;

        } else if (SunToolkit.isInstanceOf(aComponent, "javax.swing.JTable")) {

            // JTable only has ancestor focus bindings, we thus force it

            // to be focusable by returning true here.

            return true;

        } else if (SunToolkit.isInstanceOf(aComponent, "javax.swing.JComboBox")) {

            JComboBox box = (JComboBox)aComponent;

            return box.getUI().isFocusTraversable(box);

        } else if (aComponent instanceof JComponent) {

            JComponent jComponent = (JComponent)aComponent;

            InputMap inputMap = jComponent.getInputMap(JComponent.WHEN_FOCUSED,

                                                       false);

            while (inputMap != null && inputMap.size() == 0) {

                inputMap = inputMap.getParent();

            }

            if (inputMap != null) {

                return true;

            }

            // Delegate to the fitnessTestPolicy, this will test for the

            // case where the developer has overriden isFocusTraversable to

            // return true.

        }

        return fitnessTestPolicy.accept(aComponent);

    }

    private void writeObject(ObjectOutputStream out) throws IOException {

        out.writeObject(getComparator());

        out.writeBoolean(getImplicitDownCycleTraversal());

    }

    private void readObject(ObjectInputStream in)

        throws IOException, ClassNotFoundException

    {

        setComparator((Comparator)in.readObject());

        setImplicitDownCycleTraversal(in.readBoolean());

    }

}

// Create our own subclass and change accept to public so that we can call

// accept.

class SwingDefaultFocusTraversalPolicy

    extends java.awt.DefaultFocusTraversalPolicy

{

    public boolean accept(Component aComponent) {

        return super.accept(aComponent);

    }

}