1 files changed, 53 insertions, 11 deletions

diff --git a/libjava/classpath/javax/swing/plaf/basic/BasicPanelUI.java b/libjava/classpath/javax/swing/plaf/basic/BasicPanelUI.java
index 4f535f653cc..458f10204f0 100644
--- a/libjava/classpath/javax/swing/plaf/basic/BasicPanelUI.java
+++ b/libjava/classpath/javax/swing/plaf/basic/BasicPanelUI.java
@@ -1,5 +1,5 @@
 /* BasicPanelUI.java
-   Copyright (C) 2002, 2004 Free Software Foundation, Inc.
+   Copyright (C) 2002, 2004, 2006, Free Software Foundation, Inc.
 
 This file is part of GNU Classpath.
 
@@ -44,33 +44,68 @@ import javax.swing.LookAndFeel;
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.PanelUI;
 
+/**
+ * A UI delegate for the {@link JPanel} component.
+ */
 public class BasicPanelUI extends PanelUI
 {
-  public static ComponentUI createUI(JComponent x) 
+  /**
+   * A UI delegate that can be shared by all panels (because the delegate is
+   * stateless).
+   */
+  static BasicPanelUI sharedUI;
+  
+  /**
+   * Returns a UI delegate for the specified component.
+   * 
+   * @param panel  the panel.
+   */
+  public static ComponentUI createUI(JComponent panel) 
   {
-    return new BasicPanelUI();
+    if (sharedUI == null)
+      sharedUI = new BasicPanelUI();
+    return sharedUI;
   }
 
+  /**
+   * Installs this UI delegate in the specified component.
+   * 
+   * @param c  the component (should be a {@link JPanel}, <code>null</code> not
+   *     permitted).
+   */
   public void installUI(JComponent c)
   {
     super.installUI(c);
     if (c instanceof JPanel)
       {
-	JPanel p = (JPanel) c;
-	installDefaults(p);
+        JPanel p = (JPanel) c;
+        installDefaults(p);
       }
   }
 
+  /**
+   * Installs the defaults for this UI delegate in the specified panel.
+   * 
+   * @param p  the panel (<code>null</code> not permitted).
+   */
   protected void installDefaults(JPanel p)
   {
     LookAndFeel.installColorsAndFont(p, "Panel.background", "Panel.foreground",
                                      "Panel.font");
+    
+    // A test against the reference implementation shows that this method will
+    // install a border if one is defined in the UIDefaults table (even though
+    // the BasicLookAndFeel doesn't actually define a "Panel.border").  This
+    // test was written after discovering that a null argument to 
+    // uninstallDefaults throws a NullPointerException in 
+    // LookAndFeel.uninstallBorder()...
+    LookAndFeel.installBorder(p, "Panel.border");
   }
 
   /**
-   * Uninstalls this UI from the JPanel.
+   * Uninstalls this UI delegate from the specified component.
    *
-   * @param c the JPanel from which to uninstall this UI
+   * @param c the component (<code>null</code> not permitted).
    */
   public void uninstallUI(JComponent c)
   {
@@ -78,13 +113,20 @@ public class BasicPanelUI extends PanelUI
   }
 
   /**
-   * Uninstalls the UI defaults that have been install through
-   * {@link #installDefaults}.
+   * Uninstalls the UI defaults for the specified panel.
    *
-   * @param p the panel from which to uninstall the UI defaults
+   * @param p  the panel (<code>null</code> not permitted).
    */
   protected void uninstallDefaults(JPanel p)
   {
-    // Nothing to do here.
+    // Tests on the reference implementation showed this method:
+    // (1) doesn't actually remove the installed colors and font installed
+    //     by installDefaults(), it isn't necessary;
+    // (2) throws a NullPointerException in LookAndFeel.uninstallBorder() if
+    //     p is null.  Strangely, no border is installed by the 
+    //     BasicLookAndFeel - perhaps this is needed by another LAF?
+    
+    LookAndFeel.uninstallBorder(p);
   }
+  
 }