gecko/layout/base/nsChildIterator.h

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/*
 * used by nsCSSFrameConstructor to determine and iterate the child list
 * used to construct frames (normal children or something from XBL)
 */

#include "nsCOMPtr.h"
#include "nsIContent.h"
#include "nsIDOMNodeList.h"
#include "nsIDOMNode.h"

/**
 * Helper class for iterating children during frame construction.
 * This class should always be used in lieu of the straight content
 * node APIs, since it handles XBL-generated anonymous content as
 * well.
 */
class ChildIterator
{
protected:
  nsCOMPtr<nsIContent> mContent;
  PRUint32 mIndex;
  nsCOMPtr<nsIDOMNodeList> mNodes;

public:
  ChildIterator()
    : mIndex(0) {}

  ChildIterator(const ChildIterator& aOther)
    : mContent(aOther.mContent),
      mIndex(aOther.mIndex),
      mNodes(aOther.mNodes) {}

  ChildIterator& operator=(const ChildIterator& aOther) {
    mContent = aOther.mContent;
    mIndex = aOther.mIndex;
    mNodes = aOther.mNodes;
    return *this;
  }

  ChildIterator& operator++() {
    ++mIndex;
    return *this;
  }

  ChildIterator operator++(int) {
    ChildIterator result(*this);
    ++mIndex;
    return result;
  }

  ChildIterator& operator--() {
    --mIndex;
    return *this;
  }

  ChildIterator operator--(int) {
    ChildIterator result(*this);
    --mIndex;
    return result;
  }

  already_AddRefed<nsIContent> get() const {
    nsIContent* result = nsnull;
    if (mNodes) {
      nsCOMPtr<nsIDOMNode> node;
      mNodes->Item(mIndex, getter_AddRefs(node));
      CallQueryInterface(node, &result);
    } else {
      result = mContent->GetChildAt(PRInt32(mIndex));
      NS_IF_ADDREF(result);
    }

    return result;
  }

  already_AddRefed<nsIContent> operator*() const { return get(); }

  PRBool operator==(const ChildIterator& aOther) const {
    return mContent == aOther.mContent && mIndex == aOther.mIndex;
  }

  PRBool operator!=(const ChildIterator& aOther) const {
    return !aOther.operator==(*this);
  }

  PRUint32 index() {
    return mIndex;
  }

  void seek(PRUint32 aIndex) {
    // Make sure that aIndex is reasonable.  This should be |#ifdef
    // DEBUG|, but we need these numbers for the temporary workaround
    // for bug 133219.
    PRUint32 length;
    if (mNodes)
      mNodes->GetLength(&length);
    else
      length = mContent->GetChildCount();

    NS_ASSERTION(PRInt32(aIndex) >= 0 && aIndex <= length, "out of bounds");

    // Temporary workaround for bug 133219.
    if (aIndex > length)
      aIndex = length;

    mIndex = aIndex;
  }

  /**
   * Create a pair of ChildIterators for a content node. aFirst will
   * point to the first child of aContent; aLast will point one past
   * the last child of aContent.
   */
  static nsresult Init(nsIContent*    aContent,
                       ChildIterator* aFirst,
                       ChildIterator* aLast);
};