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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,

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 *

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

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package java.awt;

import java.util.List;

import java.util.ArrayList;

import sun.util.logging.PlatformLogger;

/**

 * A FocusTraversalPolicy that determines traversal order based on the order

 * of child Components in a Container. From a particular focus cycle root, the

 * policy makes a pre-order traversal of the Component hierarchy, and traverses

 * a Container's children according to the ordering of the array returned by

 * <code>Container.getComponents()</code>. Portions of the hierarchy that are

 * not visible and displayable will not be searched.

 * <p>

 * By default, ContainerOrderFocusTraversalPolicy implicitly transfers focus

 * down-cycle. That is, during normal forward 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>

 * visible, displayable, enabled, and focusable. Subclasses can modify this

 * behavior by overriding the <code>accept</code> method.

 * <p>

 * This policy takes into account <a

 * href="doc-files/FocusSpec.html#FocusTraversalPolicyProviders">focus traversal

 * policy providers</a>.  When searching for first/last/next/previous Component,

 * if a focus traversal policy provider is encountered, its focus traversal

 * policy is used to perform the search operation.

 *

 * @author David Mendenhall

 *

 * @see Container#getComponents

 * @since 1.4

 */

public class ContainerOrderFocusTraversalPolicy extends FocusTraversalPolicy

    implements java.io.Serializable

{

    private static final PlatformLogger log = PlatformLogger.getLogger("java.awt.ContainerOrderFocusTraversalPolicy");

    final private int FORWARD_TRAVERSAL = 0;

    final private int BACKWARD_TRAVERSAL = 1;

    /*

     * JDK 1.4 serialVersionUID

     */

    private static final long serialVersionUID = 486933713763926351L;

    private boolean implicitDownCycleTraversal = true;

    /**

     * Used by getComponentAfter and getComponentBefore for efficiency. In

     * order to maintain compliance with the specification of

     * FocusTraversalPolicy, if traversal wraps, we should invoke

     * getFirstComponent or getLastComponent. These methods may be overriden in

     * subclasses to behave in a non-generic way. However, in the generic case,

     * these methods will simply return the first or last Components of the

     * sorted list, respectively. Since getComponentAfter and

     * getComponentBefore have already built the list before determining

     * that they need to invoke getFirstComponent or getLastComponent, the

     * list should be reused if possible.

     */

    transient private Container cachedRoot;

    transient private List cachedCycle;

    /*

     * We suppose to use getFocusTraversalCycle & getComponentIndex methods in order

     * to divide the policy into two parts:

     * 1) Making the focus traversal cycle.

     * 2) Traversing the cycle.

     * The 1st point assumes producing a list of components representing the focus

     * traversal cycle. The two methods mentioned above should implement this logic.

     * The 2nd point assumes implementing the common concepts of operating on the

     * cycle: traversing back and forth, retrieving the initial/default/first/last

     * component. These concepts are described in the AWT Focus Spec and they are

     * applied to the FocusTraversalPolicy in general.

     * Thus, a descendant of this policy may wish to not reimplement the logic of

     * the 2nd point but just override the implementation of the 1st one.

     * A striking example of such a descendant is the javax.swing.SortingFocusTraversalPolicy.

     */

    /*protected*/ private List<Component> getFocusTraversalCycle(Container aContainer) {

        List<Component> cycle = new ArrayList<Component>();

        enumerateCycle(aContainer, cycle);

        return cycle;

    }

    /*protected*/ private int getComponentIndex(List<Component> cycle, Component aComponent) {

        return cycle.indexOf(aComponent);

    }

    private void enumerateCycle(Container container, List cycle) {

        if (!(container.isVisible() && container.isDisplayable())) {

            return;

        }

        cycle.add(container);

        Component[] components = container.getComponents();

        for (int i = 0; i < components.length; i++) {

            Component comp = components[i];

            if (comp instanceof Container) {

                Container cont = (Container)comp;

                if (!cont.isFocusCycleRoot() && !cont.isFocusTraversalPolicyProvider()) {

                    enumerateCycle(cont, cycle);

                    continue;

                }

            }

            cycle.add(comp);

        }

    }

    private Container getTopmostProvider(Container focusCycleRoot, Component aComponent) {

        Container aCont = aComponent.getParent();

        Container ftp = null;

        while (aCont  != focusCycleRoot && aCont != null) {

            if (aCont.isFocusTraversalPolicyProvider()) {

                ftp = aCont;

            }

            aCont = aCont.getParent();

        }

        if (aCont == null) {

            return null;

        }

        return ftp;

    }

    /*

     * Checks if a new focus cycle takes place and returns a Component to traverse focus to.

     * @param comp a possible focus cycle root or policy provider

     * @param traversalDirection the direction of the traversal

     * @return a Component to traverse focus to if {@code comp} is a root or provider

     *         and implicit down-cycle is set, otherwise {@code null}

     */

    private Component getComponentDownCycle(Component comp, int traversalDirection) {

        Component retComp = null;

        if (comp instanceof Container) {

            Container cont = (Container)comp;

            if (cont.isFocusCycleRoot()) {

                if (getImplicitDownCycleTraversal()) {

                    retComp = cont.getFocusTraversalPolicy().getDefaultComponent(cont);

                    if (retComp != null && log.isLoggable(PlatformLogger.FINE)) {

                        log.fine("### Transfered focus down-cycle to " + retComp +

                                 " in the focus cycle root " + cont);

                    }

                } else {

                    return null;

                }

            } else if (cont.isFocusTraversalPolicyProvider()) {

                retComp = (traversalDirection == FORWARD_TRAVERSAL ?

                           cont.getFocusTraversalPolicy().getDefaultComponent(cont) :

                           cont.getFocusTraversalPolicy().getLastComponent(cont));

                if (retComp != null && log.isLoggable(PlatformLogger.FINE)) {

                    log.fine("### Transfered focus to " + retComp + " in the FTP provider " + cont);

                }

            }

        }

        return retComp;

    }

    /**

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

     * aContainer must be a focus cycle root of aComponent or a focus traversal policy provider.

     * <p>

     * By default, ContainerOrderFocusTraversalPolicy implicitly transfers

     * focus down-cycle. That is, during normal forward 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="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 focus traversal policy provider, or if either aContainer or

     *         aComponent is null

     */

    public Component getComponentAfter(Container aContainer, Component aComponent) {

        if (log.isLoggable(PlatformLogger.FINE)) {

            log.fine("### Searching in " + aContainer + " for component after " + aComponent);

        }

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

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

        }

        if (!aContainer.isFocusTraversalPolicyProvider() && !aContainer.isFocusCycleRoot()) {

            throw new IllegalArgumentException("aContainer should be focus cycle root or focus traversal policy provider");

        } else if (aContainer.isFocusCycleRoot() && !aComponent.isFocusCycleRoot(aContainer)) {

            throw new IllegalArgumentException("aContainer is not a focus cycle root of aComponent");

        }

        synchronized(aContainer.getTreeLock()) {

            if (!(aContainer.isVisible() && aContainer.isDisplayable())) {

                return null;

            }

            // Before all the ckecks below we first see if it's an FTP provider or a focus cycle root.

            // If it's the case just go down cycle (if it's set to "implicit").

            Component comp = getComponentDownCycle(aComponent, FORWARD_TRAVERSAL);

            if (comp != null) {

                return comp;

            }

            // See if the component is inside of policy provider.

            Container provider = getTopmostProvider(aContainer, aComponent);

            if (provider != null) {

                if (log.isLoggable(PlatformLogger.FINE)) {

                    log.fine("### Asking FTP " + provider + " for component after " + aComponent);

                }

                // FTP knows how to find component after the given. We don't.

                FocusTraversalPolicy policy = provider.getFocusTraversalPolicy();

                Component afterComp = policy.getComponentAfter(provider, aComponent);

                // Null result means that we overstepped the limit of the FTP's cycle.

                // In that case we must quit the cycle, otherwise return the component found.

                if (afterComp != null) {

                    if (log.isLoggable(PlatformLogger.FINE)) {

                        log.fine("### FTP returned " + afterComp);

                    }

                    return afterComp;

                }

                aComponent = provider;

            }

            List<Component> cycle = getFocusTraversalCycle(aContainer);

            if (log.isLoggable(PlatformLogger.FINE)) {

                log.fine("### Cycle is " + cycle + ", component is " + aComponent);

            }

            int index = getComponentIndex(cycle, aComponent);

            if (index < 0) {

                if (log.isLoggable(PlatformLogger.FINE)) {

                    log.fine("### Didn't find component " + aComponent + " in a cycle " + aContainer);

                }

                return getFirstComponent(aContainer);

            }

            for (index++; index < cycle.size(); index++) {

                comp = cycle.get(index);

                if (accept(comp)) {

                    return comp;

                } else if ((comp = getComponentDownCycle(comp, FORWARD_TRAVERSAL)) != null) {

                    return comp;

                }

            }

            if (aContainer.isFocusCycleRoot()) {

                this.cachedRoot = aContainer;

                this.cachedCycle = cycle;

                comp = getFirstComponent(aContainer);

                this.cachedRoot = null;

                this.cachedCycle = null;

                return comp;

            }

        }

        return null;

    }

    /**

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

     * aContainer must be a focus cycle root of aComponent or a <a

     * href="doc-files/FocusSpec.html#FocusTraversalPolicyProviders">focus traversal policy

     * provider</a>.

     *

     * @param aContainer a focus cycle root of aComponent or 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 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");

        }

        if (!aContainer.isFocusTraversalPolicyProvider() && !aContainer.isFocusCycleRoot()) {

            throw new IllegalArgumentException("aContainer should be focus cycle root or focus traversal policy provider");

        } else if (aContainer.isFocusCycleRoot() && !aComponent.isFocusCycleRoot(aContainer)) {

            throw new IllegalArgumentException("aContainer is not a focus cycle root of aComponent");

        }

        synchronized(aContainer.getTreeLock()) {

            if (!(aContainer.isVisible() && aContainer.isDisplayable())) {

                return null;

            }

            // See if the component is inside of policy provider.

            Container provider = getTopmostProvider(aContainer, aComponent);

            if (provider != null) {

                if (log.isLoggable(PlatformLogger.FINE)) {

                    log.fine("### Asking FTP " + provider + " for component after " + aComponent);

                }

                // FTP knows how to find component after the given. We don't.

                FocusTraversalPolicy policy = provider.getFocusTraversalPolicy();

                Component beforeComp = policy.getComponentBefore(provider, aComponent);

                // Null result means that we overstepped the limit of the FTP's cycle.

                // In that case we must quit the cycle, otherwise return the component found.

                if (beforeComp != null) {

                    if (log.isLoggable(PlatformLogger.FINE)) {

                        log.fine("### FTP returned " + beforeComp);

                    }

                    return beforeComp;

                }

                aComponent = provider;

                // If the provider is traversable it's returned.

                if (accept(aComponent)) {

                    return aComponent;

                }

            }

            List<Component> cycle = getFocusTraversalCycle(aContainer);

            if (log.isLoggable(PlatformLogger.FINE)) {

                log.fine("### Cycle is " + cycle + ", component is " + aComponent);

            }

            int index = getComponentIndex(cycle, aComponent);

            if (index < 0) {

                if (log.isLoggable(PlatformLogger.FINE)) {

                    log.fine("### Didn't find component " + aComponent + " in a cycle " + aContainer);

                }

                return getLastComponent(aContainer);

            }

            Component comp = null;

            Component tryComp = null;

            for (index--; index>=0; index--) {

                comp = cycle.get(index);

                if (comp != aContainer && (tryComp = getComponentDownCycle(comp, BACKWARD_TRAVERSAL)) != null) {

                    return tryComp;

                } else if (accept(comp)) {

                    return comp;

                }

            }

            if (aContainer.isFocusCycleRoot()) {

                this.cachedRoot = aContainer;

                this.cachedCycle = cycle;

                comp = getLastComponent(aContainer);

                this.cachedRoot = null;

                this.cachedCycle = null;

                return comp;

            }

        }

        return null;

    }

    /**

     * 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 the focus cycle root or 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) {

        List<Component> cycle;

        if (log.isLoggable(PlatformLogger.FINE)) {

            log.fine("### Getting first component in " + aContainer);

        }

        if (aContainer == null) {

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

        }

        synchronized(aContainer.getTreeLock()) {

            if (!(aContainer.isVisible() && aContainer.isDisplayable())) {

                return null;

            }

            if (this.cachedRoot == aContainer) {

                cycle = this.cachedCycle;

            } else {

                cycle = getFocusTraversalCycle(aContainer);

            }

            if (cycle.size() == 0) {

                if (log.isLoggable(PlatformLogger.FINE)) {

                    log.fine("### Cycle is empty");

                }

                return null;

            }

            if (log.isLoggable(PlatformLogger.FINE)) {

                log.fine("### Cycle is " + cycle);

            }

            for (Component comp : cycle) {

                if (accept(comp)) {

                    return comp;

                } else if (comp != aContainer &&

                           (comp = getComponentDownCycle(comp, FORWARD_TRAVERSAL)) != null)

                {

                    return comp;

                }

            }

        }

        return null;

    }

    /**

     * 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 the focus cycle root or 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) {

        List<Component> cycle;

        if (log.isLoggable(PlatformLogger.FINE)) {

            log.fine("### Getting last component in " + aContainer);

        }

        if (aContainer == null) {

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

        }

        synchronized(aContainer.getTreeLock()) {

            if (!(aContainer.isVisible() && aContainer.isDisplayable())) {

                return null;

            }

            if (this.cachedRoot == aContainer) {

                cycle = this.cachedCycle;

            } else {

                cycle = getFocusTraversalCycle(aContainer);

            }

            if (cycle.size() == 0) {

                if (log.isLoggable(PlatformLogger.FINE)) {

                    log.fine("### Cycle is empty");

                }

                return null;

            }

            if (log.isLoggable(PlatformLogger.FINE)) {

                log.fine("### Cycle is " + cycle);

            }

            for (int i= cycle.size() - 1; i >= 0; i--) {

                Component comp = cycle.get(i);

                if (accept(comp)) {

                    return comp;

                } else if (comp instanceof Container && comp != aContainer) {

                    Container cont = (Container)comp;

                    if (cont.isFocusTraversalPolicyProvider()) {

                        return cont.getFocusTraversalPolicy().getLastComponent(cont);

                    }

                }

            }

        }

        return null;

    }

    /**

     * Returns the default Component to focus. This Component will be the first

     * to receive focus when traversing down into a new focus traversal cycle

     * rooted at aContainer. The default implementation of this method

     * returns the same Component as <code>getFirstComponent</code>.

     *

     * @param aContainer the focus cycle root or focus traversal policy provider whose default