text: /**************************************************************************\
   *
   *  This file is part of the Coin 3D visualization library.
   *  Copyright (C) by Kongsberg Oil & Gas Technologies.
   *
   *  This library is free software; you can redistribute it and/or
   *  modify it under the terms of the GNU General Public License
   *  ("GPL") version 2 as published by the Free Software Foundation.
   *  See the file LICENSE.GPL at the root directory of this source
   *  distribution for additional information about the GNU GPL.
   *
   *  For using Coin with software that can not be combined with the GNU
   *  GPL, and for taking advantage of the additional benefits of our
   *  support services, please contact Kongsberg Oil & Gas Technologies
   *  about acquiring a Coin Professional Edition License.
   *
   *  See http://www.coin3d.org/ for more information.
   *
   *  Kongsberg Oil & Gas Technologies, Bygdoy Alle 5, 0257 Oslo, NORWAY.
   *  http://www.sim.no/  sales@sim.no  coin-support@coin3d.org
   *
  \**************************************************************************/
  
  /*!
    \class SoClipPlaneElement Inventor/elements/SoClipPlaneElement.h
    \brief The SoClipPlaneElement class is used to manage the clip plane stack.
    \ingroup elements
  */
  
  #include <Inventor/elements/SoClipPlaneElement.h>
  #include <Inventor/elements/SoModelMatrixElement.h>
  #include <Inventor/nodes/SoNode.h>
  
  #include "SbBasicP.h"
  
  //
  // constructor for the internal class
  //
  SoClipPlaneElement::so_plane_data::so_plane_data(const SbPlane &planeref, const SbMatrix &matrix)
  {
    this->plane = this->wcPlane = planeref;
    this->wcPlane.transform(matrix);
  }
  
  /*!
    \fn SoClipPlaneElement::planes
    List of currently active planes.
  */
  
  /*!
    \fn SoClipPlaneElement::startIndex
    Index of first clip plane in this element. Used to disable clip planes
    in SoGLClipPlaneElement::pop().
  */
  
  SO_ELEMENT_SOURCE(SoClipPlaneElement);
  
  // doc from parent
  void
  SoClipPlaneElement::initClass(void)
  {
    SO_ELEMENT_INIT_CLASS(SoClipPlaneElement, inherited);
  }
  
  /*!
    The destructor.
  */
  SoClipPlaneElement::~SoClipPlaneElement()
  {
  }
  
  /*!
    Adds \a plane as an active plane. Calls addToElt() to do the job.
  */
  void
  SoClipPlaneElement::add(SoState * const state,
                          SoNode * const node,
                          const SbPlane & plane)
  {
    SoClipPlaneElement * element =
      coin_safe_cast<SoClipPlaneElement * >
      (
       SoElement::getElement(state, classStackIndex)
       );
  
    if (element) {
      element->addToElt(plane, SoModelMatrixElement::get(state));
      if (node) element->addNodeId(node);
    }
  }
  
  /*!
    Returns the current (top-of-stack) element.
  */
  const SoClipPlaneElement *
  SoClipPlaneElement::getInstance(SoState * const state)
  {
    return coin_assert_cast<const SoClipPlaneElement *>
      (
       SoElement::getConstElement(state, classStackIndex)
       );
  }
  
  /*!
    Returns the current number of active clipping planes.
  */
  int
  SoClipPlaneElement::getNum() const
  {
    return this->planes.getLength();
  }
  
  /*!
    Returns the \index'th plane.
  */
  const SbPlane &
  SoClipPlaneElement::get(const int index,
                          const SbBool inworldspace) const
  {
    assert(index >= 0 && index < this->planes.getLength());
    if (inworldspace) return this->planes.getArrayPtr()[index].wcPlane;
    return this->planes.getArrayPtr()[index].plane;
  }
  
  /*!
    This method adds the clipping plane, \a plane, to an instance.
    \a modelmatrix is the current model matrix.
  */
  void
  SoClipPlaneElement::addToElt(const SbPlane &plane,
                               const SbMatrix &modelMatrix)
  {
    SoClipPlaneElement::so_plane_data data(plane, modelMatrix);
    this->planes.append(data);
  }
  
  // doc from parent
  void
  SoClipPlaneElement::init(SoState * state)
  {
    inherited::init(state);
    this->planes.truncate(0);
    this->startIndex = 0;
  }
  
  // Documented in superclass. Overridden to copy planes into the new
  // top of stack, since planes are accumulated. Also copies accumulated
  // node ids.
  void
  SoClipPlaneElement::push(SoState * state)
  {
    inherited::push(state);
  
    SoClipPlaneElement * const prev =
      coin_assert_cast<SoClipPlaneElement *>(this->getNextInStack());
  
    this->planes.truncate(0);
    for (int i = 0; i < prev->planes.getLength(); i++) {
      this->planes.append(prev->planes[i]);
    }
    this->startIndex = prev->planes.getLength();
    this->copyNodeIds(prev);
  }
  