text: /*
   * Copyright (C) 2013 Google 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:
   *
   *     * Redistributions of source code must retain the above copyright
   * notice, this list of conditions and the following disclaimer.
   *     * Redistributions 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 Google Inc. nor the names of its
   * contributors may be used to endorse or promote products derived from
   * this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #ifndef PaintLayerStackingNodeIterator_h
  #define PaintLayerStackingNodeIterator_h
  
  #include "wtf/Allocator.h"
  #include "wtf/Noncopyable.h"
  
  namespace blink {
  
  enum ChildrenIteration {
    NegativeZOrderChildren = 1,
    // Normal flow children are not mandated by CSS 2.1 but are an artifact of
    // our implementation: we allocate PaintLayers for elements that
    // are not treated as stacking contexts and thus we need to walk them
    // during painting and hit-testing.
    NormalFlowChildren = 1 << 1,
    PositiveZOrderChildren = 1 << 2,
    AllChildren =
        NegativeZOrderChildren | NormalFlowChildren | PositiveZOrderChildren
  };
  
  class PaintLayerStackingNode;
  class PaintLayer;
  
  // This iterator walks the PaintLayerStackingNode lists in the following order:
  // NegativeZOrderChildren -> NormalFlowChildren -> PositiveZOrderChildren.
  class PaintLayerStackingNodeIterator {
    STACK_ALLOCATED();
    WTF_MAKE_NONCOPYABLE(PaintLayerStackingNodeIterator);
  
   public:
    PaintLayerStackingNodeIterator(const PaintLayerStackingNode& root,
                                   unsigned whichChildren);
  
    PaintLayerStackingNode* next();
  
   private:
    const PaintLayerStackingNode& m_root;
    unsigned m_remainingChildren;
    unsigned m_index;
    PaintLayer* m_currentNormalFlowChild;
  };
  
  // This iterator is similar to PaintLayerStackingNodeIterator but it walks the
  // lists in reverse order (from the last item to the first one).
  class PaintLayerStackingNodeReverseIterator {
    STACK_ALLOCATED();
    WTF_MAKE_NONCOPYABLE(PaintLayerStackingNodeReverseIterator);
  
   public:
    PaintLayerStackingNodeReverseIterator(const PaintLayerStackingNode& root,
                                          unsigned whichChildren)
        : m_root(root), m_remainingChildren(whichChildren) {
      setIndexToLastItem();
    }
  
    PaintLayerStackingNode* next();
  
   private:
    void setIndexToLastItem();
  
    const PaintLayerStackingNode& m_root;
    unsigned m_remainingChildren;
    int m_index;
    PaintLayer* m_currentNormalFlowChild;
  };
  
  }  // namespace blink
  
  #endif  // PaintLayerStackingNodeIterator_h
  