1 /* 2 * Copyright (c) 1997, 1998, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package javax.swing.plaf; 27 28 29 /** 30 * This interface is used to mark objects created by ComponentUI delegates. 31 * The <code>ComponentUI.installUI()</code> and 32 * <code>ComponentUI.uninstallUI()</code> methods can use this interface 33 * to decide if a properties value has been overridden. For example, the 34 * JList cellRenderer property is initialized by BasicListUI.installUI(), 35 * only if it's initial value is null: 36 * <pre> 37 * if (list.getCellRenderer() == null) { 38 * list.setCellRenderer((ListCellRenderer)(UIManager.get("List.cellRenderer"))); 39 * } 40 * </pre> 41 * At uninstallUI() time we reset the property to null if its value 42 * is an instance of UIResource: 43 * <pre> 44 * if (list.getCellRenderer() instanceof UIResource) { 45 * list.setCellRenderer(null); 46 * } 47 *</pre> 48 * This pattern applies to all properties except the java.awt.Component 49 * properties font, foreground, and background. If one of these 50 * properties isn't initialized, or is explicitly set to null, 51 * its container provides the value. For this reason the 52 * <code>"== null"</code> is unreliable when installUI() is called 53 * to dynamically change a components look and feel. So at installUI() 54 * time we check to see if the current value is a UIResource: 55 *<pre> 56 * if (!(list.getFont() instanceof UIResource)) { 57 * list.setFont(UIManager.getFont("List.font")); 58 * } 59 * </pre> 60 * 61 * @see ComponentUI 62 * @author Hans Muller 63 * 64 */ 65 66 public interface UIResource { 67 }