There is a problem in the initialization/disposing of the peers.
1. setVisible() should be called at the end of the peers initialization. We can move super.initialize() to the end of the peers initializations.
2. Invokelater in the initialization/disposing is a tricky.
3. replaceSurfacedata() should be moved outside of LWWindowPeer.setVisible()
4. Backbuffer in replaceSurfacedata() should be initialized by clearRect instead of fillrect(composite is important).
5. During lwwindowpeer initialization we call two similar methods nativeSetNSWindowAlpha() and setAlphaValue().