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 * 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
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package net.java.joglutils.msg.elements;

import net.java.joglutils.msg.math.*;
import net.java.joglutils.msg.misc.*;

/** Represents the viewing matrix, which contains the transformation
    between the camera and the model. */

public class ViewingMatrixElement extends Element {
  // Boilerplate
  private static StateIndex index = State.registerElementType();
  public StateIndex getStateIndex() { return index; }
  public Element newInstance() {
    return new ViewingMatrixElement();
  }
  /** Returns the instance of this element in the passed State. */
  public static ViewingMatrixElement getInstance(State state) {
    return (ViewingMatrixElement) state.getElement(index);
  }
  /** Enables this element in the passed state, which should be the
      default for a given action. */
  public static void enable(State defaultState) {
    Element tmp = new ViewingMatrixElement();
    defaultState.setElement(tmp.getStateIndex(), tmp);
  }
  /** Indicates whether this element is enabled in the given default
      state for a particular action. */
  public static boolean isEnabled(State state) {
    return (state.getDefaults().getElement(index) != null);
  }

  // The matrix data
  protected Mat4f matrix;

  public ViewingMatrixElement() {
    matrix = new Mat4f();
    matrix.makeIdent();
  }
  
  /** Returns the current viewing matrix; callers should not mutate
      this directly but instead use the accessor methods to change
      it. */
  public Mat4f getMatrix() {
    return matrix;
  }

  public void push(State state) {
    ViewingMatrixElement prev = (ViewingMatrixElement) getNextInStack();
    if (prev != null) {
      matrix.set(prev.matrix);
    }
  }

  /** Sets the viewing matrix in the given state to the given one. */
  public static void set(State state, Mat4f matrix) {
    ViewingMatrixElement elt = getInstance(state);
    elt.setElt(matrix);
  }

  /** Sets the viewing matrix in this element to the given one. */
  public void setElt(Mat4f matrix) {
    this.matrix.set(matrix);
  }
}