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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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
Container.getComponents(). Portions of the hierarchy that are
not visible and displayable will not be searched.


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
setImplicitDownCycleTraversal method.


By default, methods of this class will return a Component only if it is
visible, displayable, enabled, and focusable. Subclasses can modify this
behavior by overriding the accept method.


This policy takes into account focus traversal
policy providers.  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 Also:
Since:1.4
/**
 * 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>
 * By default, methods of this class will return a Component only if it is
 * 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.

/**
     * 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<Component> 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<Component> 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.Level.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.Level.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.


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 setImplicitDownCycleTraversal method.


If aContainer is focus
traversal policy provider, the focus is always transferred down-cycle.

Params:
  • aContainer – a focus cycle root of aComponent or a focus traversal policy provider
  • aComponent – a (possibly indirect) child of aContainer, or
       aContainer itself
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
Returns:the Component that should receive the focus after aComponent, or
        null if no suitable Component can be found
/**
     * 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.Level.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.Level.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.Level.FINE)) {
                        log.fine("### FTP returned " + afterComp);
                    }
                    return afterComp;
                }
                aComponent = provider;
            }

            List<Component> cycle = getFocusTraversalCycle(aContainer);

            if (log.isLoggable(PlatformLogger.Level.FINE)) {
                log.fine("### Cycle is " + cycle + ", component is " + aComponent);
            }

            int index = getComponentIndex(cycle, aComponent);

            if (index < 0) {
                if (log.isLoggable(PlatformLogger.Level.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 focus traversal policy
provider.

Params:
  • aContainer – a focus cycle root of aComponent or focus traversal policy provider
  • aComponent – a (possibly indirect) child of aContainer, or
       aContainer itself
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
Returns:the Component that should receive the focus before aComponent,
        or null if no suitable Component can be found
/**
     * 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.Level.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.Level.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.Level.FINE)) {
                log.fine("### Cycle is " + cycle + ", component is " + aComponent);
            }

            int index = getComponentIndex(cycle, aComponent);

            if (index < 0) {
                if (log.isLoggable(PlatformLogger.Level.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.

Params:
  • aContainer – the focus cycle root or focus traversal policy provider whose first
       Component is to be returned
Throws:
Returns:the first Component in the traversal cycle of aContainer,
        or null if no suitable Component can be found
/**
     * 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.Level.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.Level.FINE)) {
                    log.fine("### Cycle is empty");
                }
                return null;
            }
            if (log.isLoggable(PlatformLogger.Level.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.

Params:
  • aContainer – the focus cycle root or focus traversal policy provider whose last
       Component is to be returned
Throws:
Returns:the last Component in the traversal cycle of aContainer,
        or null if no suitable Component can be found
/**
     * 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.Level.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.Level.FINE)) {
                    log.fine("### Cycle is empty");
                }
                return null;
            }
            if (log.isLoggable(PlatformLogger.Level.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()) {
                        Component retComp = cont.getFocusTraversalPolicy().getLastComponent(cont);
                        if (retComp != null) {
                            return retComp;
                        }
                    }
                }
            }
        }
        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 getFirstComponent.

Params:
  • aContainer – the focus cycle root or focus traversal policy provider whose default
       Component is to be returned
Throws:
See Also:
Returns:the default Component in the traversal cycle of aContainer,
        or null if no suitable Component can be found
/**
     * 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
     *        Component is to be returned
     * @return the default Component in the traversal cycle of aContainer,
     *         or null if no suitable Component can be found
     * @see #getFirstComponent
     * @throws IllegalArgumentException if aContainer is null
     */
    public Component getDefaultComponent(Container aContainer) {
        return getFirstComponent(aContainer);
    }

    
Sets whether this ContainerOrderFocusTraversalPolicy transfers focus
down-cycle implicitly. If true, during normal forward focus
traversal, the Component traversed after a focus cycle root will be the
focus-cycle-root's default Component to focus. If false,
the next Component in the focus traversal cycle rooted at the specified
focus cycle root will be traversed instead. The default value for this
property is true.

Params:
  • implicitDownCycleTraversal – whether this
       ContainerOrderFocusTraversalPolicy transfers focus down-cycle
       implicitly
See Also:
/**
     * Sets whether this ContainerOrderFocusTraversalPolicy transfers focus
     * down-cycle implicitly. If <code>true</code>, during normal forward focus
     * traversal, the Component traversed after a focus cycle root will be the
     * focus-cycle-root's default Component to focus. If <code>false</code>,
     * the next Component in the focus traversal cycle rooted at the specified
     * focus cycle root will be traversed instead. The default value for this
     * property is <code>true</code>.
     *
     * @param implicitDownCycleTraversal whether this
     *        ContainerOrderFocusTraversalPolicy transfers focus down-cycle
     *        implicitly
     * @see #getImplicitDownCycleTraversal
     * @see #getFirstComponent
     */
    public void setImplicitDownCycleTraversal(boolean implicitDownCycleTraversal) {
        this.implicitDownCycleTraversal = implicitDownCycleTraversal;
    }

    
Returns whether this ContainerOrderFocusTraversalPolicy transfers focus
down-cycle implicitly. If true, during normal forward focus
traversal, the Component traversed after a focus cycle root will be the
focus-cycle-root's default Component to focus. If false,
the next Component in the focus traversal cycle rooted at the specified
focus cycle root will be traversed instead.

See Also:
Returns:whether this ContainerOrderFocusTraversalPolicy transfers focus
        down-cycle implicitly
/**
     * Returns whether this ContainerOrderFocusTraversalPolicy transfers focus
     * down-cycle implicitly. If <code>true</code>, during normal forward focus
     * traversal, the Component traversed after a focus cycle root will be the
     * focus-cycle-root's default Component to focus. If <code>false</code>,
     * the next Component in the focus traversal cycle rooted at the specified
     * focus cycle root will be traversed instead.
     *
     * @return whether this ContainerOrderFocusTraversalPolicy transfers focus
     *         down-cycle implicitly
     * @see #setImplicitDownCycleTraversal
     * @see #getFirstComponent
     */
    public boolean getImplicitDownCycleTraversal() {
        return implicitDownCycleTraversal;
    }

    
Determines whether a Component is an acceptable choice as the new
focus owner. By default, this method will accept a Component if and
only if it is visible, displayable, enabled, and focusable.

Params:
  • aComponent – the Component whose fitness as a focus owner is to
       be tested
Returns:true if aComponent is visible, displayable,
        enabled, and focusable; false otherwise
/**
     * Determines whether a Component is an acceptable choice as the new
     * focus owner. By default, this method will accept a Component if and
     * only if it is visible, displayable, enabled, and focusable.
     *
     * @param aComponent the Component whose fitness as a focus owner is to
     *        be tested
     * @return <code>true</code> if aComponent is visible, displayable,
     *         enabled, and focusable; <code>false</code> otherwise
     */
    protected boolean accept(Component aComponent) {
        if (!aComponent.canBeFocusOwner()) {
            return false;
        }

        // Verify that the Component is recursively enabled. Disabling a
        // heavyweight Container disables its children, whereas disabling
        // a lightweight Container does not.
        if (!(aComponent instanceof Window)) {
            for (Container enableTest = aComponent.getParent();
                 enableTest != null;
                 enableTest = enableTest.getParent())
            {
                if (!(enableTest.isEnabled() || enableTest.isLightweight())) {
                    return false;
                }
                if (enableTest instanceof Window) {
                    break;
                }
            }
        }

        return true;
    }
}