001: /*
002: * Copyright (c) 2002-2007 JGoodies Karsten Lentzsch. All Rights Reserved.
003: *
004: * Redistribution and use in source and binary forms, with or without
005: * modification, are permitted provided that the following conditions are met:
006: *
007: * o Redistributions of source code must retain the above copyright notice,
008: * this list of conditions and the following disclaimer.
009: *
010: * o Redistributions in binary form must reproduce the above copyright notice,
011: * this list of conditions and the following disclaimer in the documentation
012: * and/or other materials provided with the distribution.
013: *
014: * o Neither the name of JGoodies Karsten Lentzsch nor the names of
015: * its contributors may be used to endorse or promote products derived
016: * from this software without specific prior written permission.
017: *
018: * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
019: * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
020: * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
021: * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
022: * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
023: * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
024: * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
025: * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
026: * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
027: * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
028: * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029: */
030:
031: package com.jgoodies.forms.util;
032:
033: import java.beans.PropertyChangeEvent;
034: import java.beans.PropertyChangeListener;
035:
036: import javax.swing.UIManager;
037:
038: /**
039: * Consists only of static utility methods.
040: *
041: * This class may be merged with the FormLayoutUtils extra - or not. *
042: *
043: * @author Karsten Lentzsch
044: * @version $Revision: 1.4 $
045: */
046: public final class Utilities {
047:
048: // Instance *************************************************************
049:
050: private Utilities() {
051: // Suppresses default constructor, ensuring non-instantiability.
052: }
053:
054: /**
055: * Lazily checks and answers whether the Aqua look&feel is active.
056: *
057: * @return true if the current look&feel is Aqua
058: */
059: public static boolean isLafAqua() {
060: if (cachedIsLafAqua == null) {
061: cachedIsLafAqua = Boolean.valueOf(computeIsLafAqua());
062: ensureLookAndFeelChangeHandlerRegistered();
063: }
064: return cachedIsLafAqua.booleanValue();
065: }
066:
067: // Caching and Lazily Computing the Laf State *****************************
068:
069: /**
070: * Holds the cached result of the Aqua l&f check.
071: * Is invalidated by the <code>LookAndFeelChangeHandler</code>
072: * if the look&feel changes.
073: */
074: private static Boolean cachedIsLafAqua;
075:
076: /**
077: * Describes whether the <code>LookAndFeelChangeHandler</code>
078: * has been registered with the <code>UIManager</code> or not.
079: * It is registered lazily when the first cached l&f state is computed.
080: */
081: private static boolean lafChangeHandlerRegistered = false;
082:
083: private static synchronized void ensureLookAndFeelChangeHandlerRegistered() {
084: if (!lafChangeHandlerRegistered) {
085: UIManager
086: .addPropertyChangeListener(new LookAndFeelChangeHandler());
087: lafChangeHandlerRegistered = true;
088: }
089: }
090:
091: /**
092: * Computes and answers whether an Aqua look&feel is active.
093: * This may be Apple's Aqua L&f, or a sub-L&f that
094: * uses the same ID, because it doesn't substantially change the look.
095: *
096: * @return true if the current look&feel is Aqua
097: */
098: private static boolean computeIsLafAqua() {
099: return UIManager.getLookAndFeel().getID().equals("Aqua");
100: }
101:
102: /**
103: * Listens to changes of the Look and Feel and invalidates the cache.
104: */
105: private static final class LookAndFeelChangeHandler implements
106: PropertyChangeListener {
107:
108: /**
109: * Invalidates the cached laf states, if the UIManager has fired
110: * any property change event. Since we need to handle look&feel
111: * changes only, we check the event's property name to be
112: * "lookAndFeel" or <code>null</code>. The check for null is necessary
113: * to handle the special event where property name, old and new value
114: * are all <code>null</code> to indicate that multiple properties
115: * have changed.
116: *
117: * @param evt describes the property change
118: */
119: public void propertyChange(PropertyChangeEvent evt) {
120: String propertyName = evt.getPropertyName();
121: if ((propertyName == null)
122: || propertyName.equals("lookAndFeel")) {
123: cachedIsLafAqua = null;
124: }
125: }
126: }
127:
128: }
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