src/share/classes/javax/swing/RepaintManager.java

*** 987,997 ****
--- 987,1002 ----
          if (image == null || image.getWidth() < width ||
                               image.getHeight() < height) {
              if (image != null) {
                  image.flush();
              }
+             final Toolkit tk = Toolkit.getDefaultToolkit();
+             if ((tk instanceof SunToolkit) && ((SunToolkit)tk).isSwingBackbufferTranslucencySupported()) {
+                 image = config.createCompatibleVolatileImage(width, height, Transparency.TRANSLUCENT);
+             }else {
                  image = config.createCompatibleVolatileImage(width, height);
+             }
              volatileMap.put(config, image);
          }
          return image;
      }
  
*** 1475,1493 ****
--- 1480,1512 ----
                              int clipW, int clipH) {
              Graphics osg = image.getGraphics();
              int bw = Math.min(clipW, image.getWidth(null));
              int bh = Math.min(clipH, image.getHeight(null));
              int x,y,maxx,maxy;
+             final Toolkit tk = Toolkit.getDefaultToolkit();
+             final boolean isTranslucent = (tk instanceof SunToolkit)
+                     && ((SunToolkit) tk).isSwingBackbufferTranslucencySupported();
  
              try {
                  for(x = clipX, maxx = clipX+clipW; x < maxx ;  x += bw ) {
                      for(y=clipY, maxy = clipY + clipH; y < maxy ; y += bh) {
                          osg.translate(-x, -y);
                          osg.setClip(x,y,bw,bh);
+                         if (isTranslucent && osg instanceof Graphics2D) {
+                             Graphics2D g2d = (Graphics2D) osg.create();
+                             g2d.setBackground(c.getBackground());
+                             g2d.clearRect(x, y, bw, bh);
+                         }
                          c.paintToOffscreen(osg, x, y, bw, bh, maxx, maxy);
                          g.setClip(x, y, bw, bh);
+                         if (isTranslucent && g instanceof Graphics2D) {
+                             Graphics2D g2d = (Graphics2D) g.create();
+                             g2d.setComposite(AlphaComposite.Src);
+                             g2d.drawImage(image, x, y, c);
+                         } else {
                              g.drawImage(image, x, y, c);
+                         }
                          osg.translate(x, y);
                      }
                  }
              } finally {
                  osg.dispose();