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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
ComponentOrientation for more information. All columns in a
row are fully traversed before proceeding to the next row.
Author:
David Mendenhall
See Also:
ComponentOrientation
Since:
1.4/**
 * 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.
/**
     * Constructs a LayoutFocusTraversalPolicy.
     */
    public LayoutFocusTraversalPolicy() {
        super(new LayoutComparator());
    }

    
Constructs a LayoutFocusTraversalPolicy with the passed in
Comparator.
/**
     * 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.

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
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 a 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.
     * <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.

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
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 a 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.
     * <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.
Params:
aContainer – a focus cycle root of aComponent or a focus traversal policy provider whose
       first Component is to be returned
Throws:
IllegalArgumentException – if aContainer is null
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 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.
Params:
aContainer – a focus cycle root of aComponent or a focus traversal policy provider whose
       last Component is to be returned
Throws:
IllegalArgumentException – if aContainer is null
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 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 Component
is an acceptable choice as the new focus owner.
This method performs the following sequence of operations:

Checks whether aComponent is visible, displayable,
    enabled, and focusable.  If any of these properties is
    false, this method returns false.
If aComponent is an instance of JTable,
    returns true.
If aComponent is an instance of JComboBox,
    then returns the value of
    aComponent.getUI().isFocusTraversable(aComponent).
If aComponent is a JComponent
    with a JComponent.WHEN_FOCUSED
    InputMap that is neither null
    nor empty, returns true.
Returns the value of
    DefaultFocusTraversalPolicy.accept(aComponent).

Params:
aComponent – the Component whose fitness
                  as a focus owner is to be tested
See Also:
Component.isVisible
Component.isDisplayable
Component.isEnabled
Component.isFocusable
ComboBoxUI.isFocusTraversable
JComponent.getInputMap
DefaultFocusTraversalPolicy.accept
Returns:
true if aComponent is a valid choice
        for a focus owner;
        otherwise false/**
     * 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);
    }
}