path: root/libjava/javax/swing/SortingFocusTraversalPolicy.java

/* SortingFocusTraversalPolicy.java --
   Copyright (C) 2005  Free Software Foundation, Inc.

This file is part of GNU Classpath.

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package javax.swing;

import java.awt.Component;
import java.awt.Container;
import java.util.Comparator;
import java.util.Iterator;
import java.util.TreeSet;

/**
 * @author Graydon Hoare
 * @author Michael Koch
 * 
 * @since 1.4
 */
public class SortingFocusTraversalPolicy 
  extends InternalFrameFocusTraversalPolicy
{
  /**
   * The comparator used to sort elements in the focus traversal cycle
   * managed by this class.
   */
  Comparator comparator;

  /**
   * <p>Whether or not to perform an "implicit DownCycle" when selecting
   * successor components within a focus cycle.</p>
   *
   * <p>When this is true, requesting the "next" component following a
   * component which is a focus cycle root (and, necessarily, a container)
   * will enter the focus cycle root of that container, and return its
   * default focus.</p>
   *
   * <p>When this property is false, requesting the "next" component will
   * simply advance within the containing focus cycle, subject to the
   * {@link #comparator} order and the {@link #accept} judgment.</p>
   *
   * @see #getNextFocusableComponent
   */
  boolean implicitDownCycleTraversal = true;
  
  /**
   * Creates a new <code>SortingFocusTraversalPolicy</code> with no
   * comparator set.
   */
  protected SortingFocusTraversalPolicy()
  {
    // Do nothing here.
  }

  /**
   * Creates a new <code>SortingFocusTraversalPolicy</code> with the given
   * comparator set.
   *
   * @param the comparator to set
   */
  public SortingFocusTraversalPolicy(Comparator comparator)
  {
    this.comparator = comparator;
  }

  /**
   * Decide whether a component is an acceptable focus owner. 
   *
   * @param comp The component which is a candidate for focus ownership.
   *
   * @return true if the component is focusable, displayable, visible, and
   * enabled; otherwise false
   */
  protected boolean accept(Component comp)
  {
    return (comp.isVisible()
	    && comp.isDisplayable()
	    && comp.isEnabled()
	    && comp.isFocusable());
  }

  /**
   * Get the current value of the {@link #comparator} property.
   *
   * @return the current value of the property
   * 
   * @see #setComparator
   */
  protected Comparator getComparator()
  {
    return comparator;
  }

  /**
   * Set the current value of the {@link #comparator} property.
   *
   * @param comparator the new value of the property
   * 
   * @see #getComparator
   */
  protected void setComparator(Comparator comparator)
  {
    this.comparator = comparator;
  }

  private TreeSet getSortedCycle(Container root, TreeSet set)
  {
    if (set == null)
      set = (getComparator() == null 
             ? new TreeSet()
             : new TreeSet(getComparator()));
    
    if (root != null) 
      {
        Component[] comps = root.getComponents();
        for (int i = 0; i < comps.length; ++i)
          {
            Component c = comps[i];
            if (accept(c))
              set.add(c);
            if (c instanceof Container)
              getSortedCycle((Container) c, set);
          }
      }
    return set;
  }

  /**
   * Return the component which follows the specified component in this
   * focus cycle, relative to the order imposed by {@link
   * #comparator}. Candidate components are only considered if they are
   * accepted by the {@link #accept} method.
   *
   * If {@link #getImplicitDownCycleTraversal} is <code>true</code> and the
   * <code>comp</code> is a focus cycle root, an "implicit DownCycle"
   * occurs and the method returns the
   * <code>getDefaultComponent(comp)</code>.
   * 
   * @param root the focus cycle root to search for a successor within
   * @param comp the component to search for the successor of
   *
   * @return the component following the specified component under
   * the specified root, or null if no such component is found
   * 
   * @throws IllegalArgumentException if either argument is null, or
   * if the root is not a focus cycle root of the component
   */
  public Component getComponentAfter(Container root, 
                                     Component comp)
  {
    if (comp == null || root == null || !comp.isFocusCycleRoot(root))
      throw new IllegalArgumentException();

    if (getImplicitDownCycleTraversal() 
        && comp instanceof Container
        && ((Container)comp).isFocusCycleRoot())
      {
        return getDefaultComponent((Container) comp);
      }

    TreeSet set = getSortedCycle(root, null);
    Iterator i = set.iterator();
    while (i.hasNext())
      {
        Component c = (Component) i.next();
        if (c != null && c.equals(comp))
          {
            if (i.hasNext())
              return (Component) i.next();
            break;
          }
      }
    return null;
  }


  /**
   * Return the component which precedes the specified component in this
   * focus cycle, relative to the order imposed by {@link
   * #comparator}. Candidate components are only considered if they are
   * accepted by the {@link #accept} method.
   * 
   * @param root the focus cycle root to search for a predecessor within
   * @param comp the component to search for the predecessor of
   *
   * @return the component preceding the specified component under the
   * specified root, or null if no such component is found
   * 
   * @throws IllegalArgumentException if either argument is null, or
   * if the root is not a focus cycle root of the component
   */
  public Component getComponentBefore(Container root, 
                                      Component comp)
  {
    if (comp == null || root == null || !comp.isFocusCycleRoot(root))
      throw new IllegalArgumentException();
    TreeSet set = getSortedCycle(root, null);
    Iterator i = set.iterator();
    Component prev = null;
    while (i.hasNext())
      {
        Component c = (Component) i.next();
        if (c != null && c.equals(comp))
          break;
        prev = c;
      }
    return prev;
  }

  /**
   * Return the default component of <code>root</code>, which is by default
   * the same as the first component, returned by {@link
   * #getFirstComponent}.
   *
   * @param root the focus cycle root to return the default component of
   *
   * @return the default focus component for <code>root</code>
   *
   * @throws IllegalArgumentException if root is null
   */
  public Component getDefaultComponent(Container root)
  {
    return getFirstComponent(root);
  }

  /** 
   * Return the first focusable component of the focus cycle root
   * <code>comp</code> under the ordering imposed by the {@link
   * #comparator} property. Candidate components are only considered if
   * they are accepted by the {@link #accept} method.
   *
   * @param root the focus cycle root to search for the first component of
   *
   * @return the first component under <code>root</code>, or null if
   * no components are found.
   *
   * @throws IllegalArgumentException if root is null
   */
  public Component getFirstComponent(Container root)
  {
    if (root == null)
      throw new IllegalArgumentException();
    TreeSet set = getSortedCycle(root, null);
    Iterator i = set.iterator();
    if (i.hasNext())
      return (Component) i.next();
    return null;
  }
  
  /** 
   * Return the last focusable component of the focus cycle root
   * <code>comp</code> under the ordering imposed by the {@link
   * #comparator} property. Candidate components are only considered if
   * they are accepted by the {@link #accept} method.
   *
   * @param root the focus cycle root to search for the last component of
   *
   * @return the last component under <code>root</code>, or null if
   * no components are found.
   *
   * @throws IllegalArgumentException if root is null
   */
  public Component getLastComponent(Container root)
  {
    if (root == null)
      throw new IllegalArgumentException();
    TreeSet set = getSortedCycle(root, null);
    Iterator i = set.iterator();
    Component last = null;
    while (i.hasNext())
      last = (Component) i.next();
    return last;
  }

  /**
   * Return the current value of the {@link implicitDownCycleTraversal}
   * property.
   *
   * @return the current value of the property
   * 
   * @see setImplicitDownCycleTraversal
   */
  public boolean getImplicitDownCycleTraversal()
  {
    return implicitDownCycleTraversal;
  }

  /**
   * Set the current value of the {@link implicitDownCycleTraversal}
   * property.
   *
   * @param down the new value of the property
   * 
   * @see getImplicitDownCycleTraversal
   */
  public void setImplicitDownCycleTraversal(boolean down)
  {
    implicitDownCycleTraversal = down;
  }
}