/*

 * Copyright (c) 1997, 1998, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 * questions.

 */

package javax.swing.plaf;

/**

 * This interface is used to mark objects created by ComponentUI delegates.

 * The <code>ComponentUI.installUI()</code> and

 * <code>ComponentUI.uninstallUI()</code> methods can use this interface

 * to decide if a properties value has been overridden.  For example, the

 * JList cellRenderer property is initialized by BasicListUI.installUI(),

 * only if it's initial value is null:

 * <pre>

 * if (list.getCellRenderer() == null) {

 *     list.setCellRenderer((ListCellRenderer)(UIManager.get("List.cellRenderer")));

 * }

 * </pre>

 * At uninstallUI() time we reset the property to null if its value

 * is an instance of UIResource:

 * <pre>

 * if (list.getCellRenderer() instanceof UIResource) {

 *     list.setCellRenderer(null);

 * }

 *</pre>

 * This pattern applies to all properties except the java.awt.Component

 * properties font, foreground, and background.  If one of these

 * properties isn't initialized, or is explicitly set to null,

 * its container provides the value.  For this reason the

 * <code>"== null"</code> is unreliable when installUI() is called

 * to dynamically change a components look and feel.  So at installUI()

 * time we check to see if the current value is a UIResource:

 *<pre>

 * if (!(list.getFont() instanceof UIResource)) {

 *     list.setFont(UIManager.getFont("List.font"));

 * }

 * </pre>

 *

 * @see ComponentUI

 * @author Hans Muller

 *

 */

public interface UIResource {

}