001    /* BasicPanelUI.java
002       Copyright (C) 2002, 2004, 2006, Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    
039    package javax.swing.plaf.basic;
040    
041    import javax.swing.JComponent;
042    import javax.swing.JPanel;
043    import javax.swing.LookAndFeel;
044    import javax.swing.plaf.ComponentUI;
045    import javax.swing.plaf.PanelUI;
046    
047    /**
048     * A UI delegate for the {@link JPanel} component.
049     */
050    public class BasicPanelUI extends PanelUI
051    {
052      /**
053       * A UI delegate that can be shared by all panels (because the delegate is
054       * stateless).
055       */
056      static BasicPanelUI sharedUI;
057    
058      /**
059       * Returns a UI delegate for the specified component.
060       *
061       * @param panel  the panel.
062       */
063      public static ComponentUI createUI(JComponent panel)
064      {
065        if (sharedUI == null)
066          sharedUI = new BasicPanelUI();
067        return sharedUI;
068      }
069    
070      /**
071       * Installs this UI delegate in the specified component.
072       *
073       * @param c  the component (should be a {@link JPanel}, <code>null</code> not
074       *     permitted).
075       */
076      public void installUI(JComponent c)
077      {
078        super.installUI(c);
079        if (c instanceof JPanel)
080          {
081            JPanel p = (JPanel) c;
082            installDefaults(p);
083          }
084      }
085    
086      /**
087       * Installs the defaults for this UI delegate in the specified panel.
088       *
089       * @param p  the panel (<code>null</code> not permitted).
090       */
091      protected void installDefaults(JPanel p)
092      {
093        LookAndFeel.installColorsAndFont(p, "Panel.background", "Panel.foreground",
094                                         "Panel.font");
095    
096        // A test against the reference implementation shows that this method will
097        // install a border if one is defined in the UIDefaults table (even though
098        // the BasicLookAndFeel doesn't actually define a "Panel.border").  This
099        // test was written after discovering that a null argument to
100        // uninstallDefaults throws a NullPointerException in
101        // LookAndFeel.uninstallBorder()...
102        LookAndFeel.installBorder(p, "Panel.border");
103      }
104    
105      /**
106       * Uninstalls this UI delegate from the specified component.
107       *
108       * @param c the component (<code>null</code> not permitted).
109       */
110      public void uninstallUI(JComponent c)
111      {
112        uninstallDefaults((JPanel) c);
113      }
114    
115      /**
116       * Uninstalls the UI defaults for the specified panel.
117       *
118       * @param p  the panel (<code>null</code> not permitted).
119       */
120      protected void uninstallDefaults(JPanel p)
121      {
122        // Tests on the reference implementation showed this method:
123        // (1) doesn't actually remove the installed colors and font installed
124        //     by installDefaults(), it isn't necessary;
125        // (2) throws a NullPointerException in LookAndFeel.uninstallBorder() if
126        //     p is null.  Strangely, no border is installed by the
127        //     BasicLookAndFeel - perhaps this is needed by another LAF?
128    
129        LookAndFeel.uninstallBorder(p);
130      }
131    
132    }