001/* DefaultFocusTraversalPolicy.java -- 002 Copyright (C) 2002, 2005 Free Software Foundation, Inc. 003 004This file is part of GNU Classpath. 005 006GNU Classpath is free software; you can redistribute it and/or modify 007it under the terms of the GNU General Public License as published by 008the Free Software Foundation; either version 2, or (at your option) 009any later version. 010 011GNU Classpath is distributed in the hope that it will be useful, but 012WITHOUT ANY WARRANTY; without even the implied warranty of 013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014General Public License for more details. 015 016You should have received a copy of the GNU General Public License 017along with GNU Classpath; see the file COPYING. If not, write to the 018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 01902110-1301 USA. 020 021Linking this library statically or dynamically with other modules is 022making a combined work based on this library. Thus, the terms and 023conditions of the GNU General Public License cover the whole 024combination. 025 026As a special exception, the copyright holders of this library give you 027permission to link this library with independent modules to produce an 028executable, regardless of the license terms of these independent 029modules, and to copy and distribute the resulting executable under 030terms of your choice, provided that you also meet, for each linked 031independent module, the terms and conditions of the license of that 032module. An independent module is a module which is not derived from 033or based on this library. If you modify this library, you may extend 034this exception to your version of the library, but you are not 035obligated to do so. If you do not wish to do so, delete this 036exception statement from your version. */ 037 038 039package java.awt; 040 041/** 042 * DefaultFocusTraversalPolicy is the default focus traversal policy 043 * used by Containers. 044 * 045 * This policy sharpens ContainerOrderFocusTraversalPolicy's 046 * acceptance criteria, to reject those Components that have 047 * unfocusable peers. Despite this extra strictness, this policy will 048 * always accept a Component that has explicitly been set focusable by 049 * any means. 050 * 051 * This AWT implementation assumes that the peers of the following 052 * Components are not focusable: Canvas, Panel, Label, ScrollPane, 053 * Scrollbar, Window, and any lightweight Component. 054 * 055 * A Component's focusability is independent of the focusability of 056 * its peer. 057 * 058 * @author Thomas Fitzsimmons (fitzsim@redhat.com) 059 * @since 1.4 060 */ 061public class DefaultFocusTraversalPolicy 062 extends ContainerOrderFocusTraversalPolicy 063{ 064 private static final long serialVersionUID = 8876966522510157497L; 065 066 /** 067 * Construct a default focus traversal policy. 068 */ 069 public DefaultFocusTraversalPolicy () 070 { 071 } 072 073 /** 074 * Check whether a given Component would be acceptable as a focus 075 * owner. The Component must be displayable, visible and enabled to 076 * be acceptable. If the Component's focus traversability has been 077 * overridden, by overriding Component.isFocusTraversable or 078 * Component.isFocusable, or by calling Component.setFocusable, then 079 * the Component will be accepted if it is focusable. If the 080 * Component uses the default focus traversable behaviour, then 081 * <code>comp</code> will always be rejected if it is a Canvas, 082 * Panel, Label, ScrollPane, Scrollbar, Window or lightweight 083 * Component. 084 * 085 * @param comp the Component to check 086 * 087 * @return true if the Component is an acceptable target for 088 * keyboard input focus, false otherwise 089 */ 090 protected boolean accept (Component comp) 091 { 092 if (comp.visible 093 && comp.isDisplayable () 094 && comp.enabled) 095 { 096 if (comp.isFocusTraversableOverridden != 0 097 && (comp.isFocusTraversable () || comp.isFocusable())) 098 return true; 099 100 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}