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/*
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* Copyright (c) 1997, 1998, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package javax.swing.plaf;
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/**
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* This interface is used to mark objects created by ComponentUI delegates.
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* The <code>ComponentUI.installUI()</code> and
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* <code>ComponentUI.uninstallUI()</code> methods can use this interface
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* to decide if a properties value has been overridden. For example, the
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* JList cellRenderer property is initialized by BasicListUI.installUI(),
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* only if it's initial value is null:
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* <pre>
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* if (list.getCellRenderer() == null) {
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* list.setCellRenderer((ListCellRenderer)(UIManager.get("List.cellRenderer")));
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* }
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* </pre>
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* At uninstallUI() time we reset the property to null if its value
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* is an instance of UIResource:
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* <pre>
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* if (list.getCellRenderer() instanceof UIResource) {
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* list.setCellRenderer(null);
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* }
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*</pre>
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* This pattern applies to all properties except the java.awt.Component
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* properties font, foreground, and background. If one of these
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* properties isn't initialized, or is explicitly set to null,
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* its container provides the value. For this reason the
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* <code>"== null"</code> is unreliable when installUI() is called
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* to dynamically change a components look and feel. So at installUI()
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* time we check to see if the current value is a UIResource:
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*<pre>
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* if (!(list.getFont() instanceof UIResource)) {
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* list.setFont(UIManager.getFont("List.font"));
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* }
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* </pre>
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*
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* @see ComponentUI
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* @author Hans Muller
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*
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*/
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public interface UIResource {
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}
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