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diff --git a/src/net/java/joglutils/msg/elements/Element.java b/src/net/java/joglutils/msg/elements/Element.java
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+/*
+ * Copyright (c) 2007 Sun Microsystems, Inc. All Rights Reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ * 
+ * - Redistribution of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * 
+ * - Redistribution in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ * 
+ * Neither the name of Sun Microsystems, Inc. or the names of
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ * 
+ * This software is provided "AS IS," without a warranty of any kind. ALL
+ * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES,
+ * INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A
+ * PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN
+ * MICROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL NOT BE LIABLE FOR
+ * ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
+ * DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL SUN OR
+ * ITS LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR
+ * DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE
+ * DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY,
+ * ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE, EVEN IF
+ * SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
+ * 
+ * You acknowledge that this software is not designed or intended for use
+ * in the design, construction, operation or maintenance of any nuclear
+ * facility.
+ * 
+ */
+
+package net.java.joglutils.msg.elements;
+
+import net.java.joglutils.msg.misc.*;
+
+/** Represents an element in the global {@link
+    net.java.joglutils.msg.misc.State state}, such as the current 3D
+    coordinates or texture to be applied. The organization of the
+    global state into elements is one of the key mechanisms for
+    extendability of the library which was pioneered by Open Inventor.
+*/
+
+public abstract class Element {
+  // Elements are organized into stacks. When we descend past (for
+  // example) a Separator node, we need to push all of the state
+  // elements, traverse the children, and then pop the state elements
+  // so afterward we restore the original state. This is implemented
+  // in the State class using a linked list of Elements, where the
+  // State keeps track of the top of each element stack.
+  private Element nextInStack;
+
+  // Additionally we maintain a linked list through all Element
+  // instances pushed and popped in the State, so that we don't have
+  // to traverse all Element slots when performing a state pop.
+  private Element next;
+
+  // Elements need to keep track of their depth in the stack in order
+  // for the State to maintain itself
+  private int depth;
+
+  protected Element() {}
+
+  /** Creates a new instance initialized to the default values for the
+      state element. All concrete Element subclasses must implement
+      this operation. */
+  public abstract Element newInstance();
+
+  /** Returns the next element in the stack. */
+  public Element getNextInStack()                    { return nextInStack;             }
+  /** Sets the next element in the stack. */
+  public void    setNextInStack(Element nextInStack) { this.nextInStack = nextInStack; }
+
+  /** Returns the next element in the linked list of elements which
+      were modified since the last state push. */
+  public Element getNext()             { return next;      }
+  /** Sets the next element in the linked list of elements which were
+      modified since the last state push. */
+  public void    setNext(Element next) { this.next = next; }
+
+  /** Returns the depth of this element in its stack, used to implement lazy state pushing. */
+  public int     getDepth()          { return depth;       }
+  /** Sets the depth of this element in its stack, used to implement lazy state pushing. */
+  public void    setDepth(int depth) { this.depth = depth; }
+
+  /** Pushes the element, allowing for side effects to occur. Default method does nothing. */
+  public void    push(State state) {}
+  /** Pops the element, allowing for side effects to occur. Default
+      method does nothing. NOTE that it is not legal to call
+      State.getElement() in the implementation of this method, which
+      is why the previous top element is provided as an argument. */
+  public void    pop (State state, Element previousTopElement) {}
+
+  /** All concrete element subclasses must register themselves with
+      the State in order to reserve a slot, or index, in the
+      state. This method must be overridden to return this slot. */
+  public abstract StateIndex getStateIndex();
+}