src/java.desktop/share/classes/com/sun/java/swing/plaf/windows/AnimationController.java

@@ -81,11 +81,11 @@
     //this timer is used to cause repaint on animated components
     //30 repaints per second should give smooth animation affect
     private final javax.swing.Timer timer =
         new javax.swing.Timer(1000/30, this);
 
-    private static synchronized AnimationController getAnimationController() {
+    static synchronized AnimationController getAnimationController() {
         AppContext appContext = AppContext.getAppContext();
         Object obj = appContext.get(ANIMATION_CONTROLLER_KEY);
         if (obj == null) {
             obj = new AnimationController();
             appContext.put(ANIMATION_CONTROLLER_KEY, obj);

@@ -202,11 +202,11 @@
                                        State state) {
         component.putClientProperty(PartUIClientPropertyKey.getKey(part),
                                     state);
     }
 
-    private synchronized void startAnimation(JComponent component,
+    synchronized void startAnimation(JComponent component,
                                      Part part,
                                      State startState,
                                      State endState,
                                      long millis) {
         boolean isForwardAndReverse = false;

@@ -389,10 +389,14 @@
                     alpha = progress;
                 } else {
                     alpha = 1 - progress;
                 }
                 g.setComposite(AlphaComposite.SrcOver.derive(alpha));
+                if (state == null) { // used for animating buttons in a specific JToolBar
+                    g.setColor(Color.WHITE);
+                    g.fillRect(dx, dy, dw, dh);
+                }
                 skin.paintSkinRaw(g, dx, dy, dw, dh, state);
                 g.dispose();
             } else {
                 skin.paintSkinRaw(_g, dx, dy, dw, dh, state);
             }