libjava/java/awt/DefaultFocusTraversalPolicy.java

   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., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 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   /**
  65    * Construct a default focus traversal policy.
  66    */
  67   public DefaultFocusTraversalPolicy ()
  68   {
  69   }
  70
  71   /**
  72    * Check whether a given Component would be acceptable as a focus
  73    * owner.  The Component must be displayable, visible and enabled to
  74    * be acceptable.  If the Component's focus traversability has been
  75    * overridden, by overriding Component.isFocusTraversable or
  76    * Component.isFocusable, or by calling Component.setFocusable, then
  77    * the Component will be accepted if it is focusable.  If the
  78    * Component uses the default focus traversable behaviour, then
  79    * <code>comp</code> will always be rejected if it is a Canvas,
  80    * Panel, Label, ScrollPane, Scrollbar, Window or lightweight
  81    * Component.
  82    *
  83    * @param comp the Component to check
  84    *
  85    * @return true if the Component is an acceptable target for
  86    * keyboard input focus, false otherwise
  87    */
  88   protected boolean accept (Component comp)
  89   {
  90     if (comp.visible
  91         && comp.isDisplayable ()
  92         && comp.enabled)
  93       {
  94         if (comp.isFocusTraversableOverridden != 0
  95             && (comp.isFocusTraversable () || comp.isFocusable()))
  96           return true;
  97
  98         if (!(comp instanceof Canvas
  99               || comp instanceof Panel
 100               || comp instanceof Label
 101               || comp instanceof ScrollPane
 102               || comp instanceof Scrollbar
 103               || comp instanceof Window
 104               || comp.isLightweight ()))
 105           return true;
 106       }
 107     return false;
 108   }
 109 }