001/* BasicPanelUI.java
002   Copyright (C) 2002, 2004, 2006, Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package javax.swing.plaf.basic;
040
041import javax.swing.JComponent;
042import javax.swing.JPanel;
043import javax.swing.LookAndFeel;
044import javax.swing.plaf.ComponentUI;
045import javax.swing.plaf.PanelUI;
046
047/**
048 * A UI delegate for the {@link JPanel} component.
049 */
050public 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}