The current interface between scenegraph and quantum for screen configuration queries and update notifications doesn't provide enough information about configuration changes. From the available information scenegraph side can't detect which screens were added, removed or changed. It can only obtain the new screen configurations, but there is no way how to match them against the old configuration and determine the specific changes. For this we need some kind of unique screen id attribute which will be kept for modified screens (glass Screen.getNativeScreen?). Alternatively quantum needs to ensure that a single screen will always be represented by the same java object (requires mutable screen objects).