@Override
    public void write(JmeExporter ex) throws IOException {
        super.write(ex);
        OutputCapsule oc = ex.getCapsule(this);
        oc.write(screen, "screen", "");
    }
@author Nehon
@deprecated use GuiEvent instead
jme3-niftygui/src/main/java/com/jme3/cinematic/events/GuiTrack.java