defaultfocustraversalpolicy.java

gcc的组建

/* DefaultFocusTraversalPolicy.java -- 
   Copyright (C) 2002, 2005  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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General Public License for more details.

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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
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this exception to your version of the library, but you are not
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package java.awt;

/**
 * DefaultFocusTraversalPolicy is the default focus traversal policy
 * used by Containers.
 *
 * This policy sharpens ContainerOrderFocusTraversalPolicy's
 * acceptance criteria, to reject those Components that have
 * unfocusable peers.  Despite this extra strictness, this policy will
 * always accept a Component that has explicitly been set focusable by
 * any means.
 *
 * This AWT implementation assumes that the peers of the following
 * Components are not focusable: Canvas, Panel, Label, ScrollPane,
 * Scrollbar, Window, and any lightweight Component.
 *
 * A Component's focusability is independent of the focusability of
 * its peer.
 *
 * @author Thomas Fitzsimmons ([e-mail])
 * @since 1.4
 */
public class DefaultFocusTraversalPolicy
  extends ContainerOrderFocusTraversalPolicy
{
  /**
   * Construct a default focus traversal policy.
   */
  public DefaultFocusTraversalPolicy ()
  {
  }

  /**
   * Check whether a given Component would be acceptable as a focus
   * owner.  The Component must be displayable, visible and enabled to
   * be acceptable.  If the Component's focus traversability has been
   * overridden, by overriding Component.isFocusTraversable or
   * Component.isFocusable, or by calling Component.setFocusable, then
   * the Component will be accepted if it is focusable.  If the
   * Component uses the default focus traversable behaviour, then
   * <code>comp</code> will always be rejected if it is a Canvas,
   * Panel, Label, ScrollPane, Scrollbar, Window or lightweight
   * Component.
   *
   * @param comp the Component to check
   *
   * @return true if the Component is an acceptable target for
   * keyboard input focus, false otherwise
   */
  protected boolean accept (Component comp)
  {
    if (comp.visible
	&& comp.isDisplayable ()
	&& comp.enabled)
      {
	if (comp.isFocusTraversableOverridden != 0
	    && (comp.isFocusTraversable () || comp.isFocusable()))
          return true;
        
	if (!(comp instanceof Canvas
              || comp instanceof Panel
              || comp instanceof Label
              || comp instanceof ScrollPane
              || comp instanceof Scrollbar
              || comp instanceof Window
              || comp.isLightweight ()))
          return true;
      }
    return false;
  }
}