Source for java.awt.DefaultFocusTraversalPolicy

   1: /* DefaultFocusTraversalPolicy.java -- 
   2:    Copyright (C) 2002, 2005  Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package java.awt;
  40: 
  41: /**
  42:  * DefaultFocusTraversalPolicy is the default focus traversal policy
  43:  * used by Containers.
  44:  *
  45:  * This policy sharpens ContainerOrderFocusTraversalPolicy's
  46:  * acceptance criteria, to reject those Components that have
  47:  * unfocusable peers.  Despite this extra strictness, this policy will
  48:  * always accept a Component that has explicitly been set focusable by
  49:  * any means.
  50:  *
  51:  * This AWT implementation assumes that the peers of the following
  52:  * Components are not focusable: Canvas, Panel, Label, ScrollPane,
  53:  * Scrollbar, Window, and any lightweight Component.
  54:  *
  55:  * A Component's focusability is independent of the focusability of
  56:  * its peer.
  57:  *
  58:  * @author Thomas Fitzsimmons (fitzsim@redhat.com)
  59:  * @since 1.4
  60:  */
  61: public class DefaultFocusTraversalPolicy
  62:   extends ContainerOrderFocusTraversalPolicy
  63: {
  64:   private static final long serialVersionUID = 8876966522510157497L;
  65: 
  66:   /**
  67:    * Construct a default focus traversal policy.
  68:    */
  69:   public DefaultFocusTraversalPolicy ()
  70:   {
  71:   }
  72: 
  73:   /**
  74:    * Check whether a given Component would be acceptable as a focus
  75:    * owner.  The Component must be displayable, visible and enabled to
  76:    * be acceptable.  If the Component's focus traversability has been
  77:    * overridden, by overriding Component.isFocusTraversable or
  78:    * Component.isFocusable, or by calling Component.setFocusable, then
  79:    * the Component will be accepted if it is focusable.  If the
  80:    * Component uses the default focus traversable behaviour, then
  81:    * <code>comp</code> will always be rejected if it is a Canvas,
  82:    * Panel, Label, ScrollPane, Scrollbar, Window or lightweight
  83:    * Component.
  84:    *
  85:    * @param comp the Component to check
  86:    *
  87:    * @return true if the Component is an acceptable target for
  88:    * keyboard input focus, false otherwise
  89:    */
  90:   protected boolean accept (Component comp)
  91:   {
  92:     if (comp.visible
  93:     && comp.isDisplayable ()
  94:     && comp.enabled)
  95:       {
  96:     if (comp.isFocusTraversableOverridden != 0
  97:         && (comp.isFocusTraversable () || comp.isFocusable()))
  98:           return true;
  99:         
 100:     if (!(comp instanceof Canvas
 101:               || comp instanceof Panel
 102:               || comp instanceof Label
 103:               || comp instanceof ScrollPane
 104:               || comp instanceof Scrollbar
 105:               || comp instanceof Window
 106:               || comp.isLightweight ()))
 107:           return true;
 108:       }
 109:     return false;
 110:   }
 111: }