gecko-dev/content/base/src/nsContentList.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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 * Version: NPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Netscape Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * http://www.mozilla.org/NPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is 
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1998
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
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#include "nsContentList.h"
#include "nsIContent.h"
#include "nsIDOMNode.h"
#include "nsIDOM3Node.h"
#include "nsIDocument.h"
#include "nsINameSpaceManager.h"
#include "nsGenericElement.h"

#include "nsContentUtils.h"

#include "nsLayoutAtoms.h"
#include "nsHTMLAtoms.h" // XXX until atoms get factored into nsLayoutAtoms

// Form related includes
#include "nsIDOMHTMLFormElement.h"
#include "nsIContentList.h"

#include "pldhash.h"

nsBaseContentList::nsBaseContentList()
{
  NS_INIT_REFCNT();
}

nsBaseContentList::~nsBaseContentList()
{
  // mElements only has weak references to the content objects so we
  // don't need to do any cleanup here.
}


// QueryInterface implementation for nsBaseContentList
NS_INTERFACE_MAP_BEGIN(nsBaseContentList)
  NS_INTERFACE_MAP_ENTRY(nsIDOMNodeList)
  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIDOMNodeList)
  NS_INTERFACE_MAP_ENTRY_CONTENT_CLASSINFO(NodeList)
NS_INTERFACE_MAP_END


NS_IMPL_ADDREF(nsBaseContentList)
NS_IMPL_RELEASE(nsBaseContentList)


NS_IMETHODIMP
nsBaseContentList::GetLength(PRUint32* aLength)
{
  *aLength = mElements.Count();

  return NS_OK;
}

NS_IMETHODIMP
nsBaseContentList::Item(PRUint32 aIndex, nsIDOMNode** aReturn)
{
  nsISupports *tmp = NS_REINTERPRET_CAST(nsISupports *,
                                         mElements.SafeElementAt(aIndex));
  if (!tmp) {
    *aReturn = nsnull;

    return NS_OK;
  }

  return CallQueryInterface(tmp, aReturn);
}

NS_IMETHODIMP
nsBaseContentList::AppendElement(nsIContent *aContent)
{
  // Shouldn't hold a reference since we'll be told when the content
  // leaves the document or the document will be destroyed.
  mElements.AppendElement(aContent);

  return NS_OK;
}

NS_IMETHODIMP
nsBaseContentList::RemoveElement(nsIContent *aContent)
{
  mElements.RemoveElement(aContent);
  
  return NS_OK;
}

NS_IMETHODIMP
nsBaseContentList::IndexOf(nsIContent *aContent, PRInt32& aIndex)
{
  aIndex = mElements.IndexOf(aContent);

  return NS_OK;
}

NS_IMETHODIMP
nsBaseContentList::Reset()
{
  mElements.Clear();

  return NS_OK;
}

// nsFormContentList

// This helper function checks if aContent is in some way associated
// with aForm, this check is only successful if the form is a
// container (and a form is a container as long as the document is
// wellformed). If the form is a container the only elements that are
// considerd to be associated with a form are the elements that are
// contained within the form. If the form is a leaf element then all
// the elements will be accepted into this list.

static PRBool BelongsInForm(nsIDOMHTMLFormElement *aForm,
                            nsIContent *aContent)
{
  nsCOMPtr<nsIContent> form(do_QueryInterface(aForm));

  if (!form) {
    NS_WARNING("This should not happen, form is not an nsIContent!");

    return PR_TRUE;
  }

  if (form.get() == aContent) {
    // The list for aForm contains the form itself, forms should not
    // be reachable by name in the form namespace, so we return false
    // here.

    return PR_FALSE;
  }

  nsCOMPtr<nsIContent> content;

  aContent->GetParent(*getter_AddRefs(content));

  while (content) {
    if (content == form) {
      // aContent is contained within the form so we return true.

      return PR_TRUE;
    }

    nsCOMPtr<nsIAtom> tag;

    content->GetTag(*getter_AddRefs(tag));

    if (tag.get() == nsHTMLAtoms::form) {
      // The child is contained within a form, but not the right form
      // so we ignore it.

      return PR_FALSE;
    }

    nsIContent *tmp = content;

    tmp->GetParent(*getter_AddRefs(content));
  }

  PRInt32 count = 0;

  form->ChildCount(count);

  if (!count) {
    // The form is a leaf and aContent wasn't inside any other form so
    // we return true

    return PR_TRUE;
  }

  // The form is a container but aContent wasn't inside the form,
  // return false

  return PR_FALSE;
}

nsFormContentList::nsFormContentList(nsIDOMHTMLFormElement *aForm,
                                     nsBaseContentList& aContentList)
  : nsBaseContentList()
{
  NS_INIT_REFCNT();

  // move elements that belong to mForm into this content list

  PRUint32 i, length = 0;
  nsCOMPtr<nsIDOMNode> item;

  aContentList.GetLength(&length);

  for (i = 0; i < length; i++) {
    aContentList.Item(i, getter_AddRefs(item));

    nsCOMPtr<nsIContent> c(do_QueryInterface(item));

    if (c && BelongsInForm(aForm, c)) {
      AppendElement(c);
    }
  }
}

nsFormContentList::~nsFormContentList()
{
  Reset();
}

NS_IMETHODIMP
nsFormContentList::AppendElement(nsIContent *aContent)
{
  NS_ADDREF(aContent);

  return nsBaseContentList::AppendElement(aContent);
}

NS_IMETHODIMP
nsFormContentList::RemoveElement(nsIContent *aContent)
{
  PRInt32 i = mElements.IndexOf(aContent);

  if (i >= 0) {
    nsIContent *content = NS_STATIC_CAST(nsIContent *, mElements.ElementAt(i));

    NS_RELEASE(content);

    mElements.RemoveElementAt(i);
  }

  return NS_OK;
}

NS_IMETHODIMP
nsFormContentList::Reset()
{
  PRInt32 i, length = mElements.Count();

  for (i = 0; i < length; i++) {
    nsIContent *content = NS_STATIC_CAST(nsIContent *, mElements.ElementAt(i));

    NS_RELEASE(content);
  }

  return nsBaseContentList::Reset();
}

// Hashtable for storing nsContentLists
static PLDHashTable gContentListHashTable;

struct ContentListHashEntry : public PLDHashEntryHdr
{
  nsContentList* mContentList;
};

PR_STATIC_CALLBACK(const void *)
ContentListHashtableGetKey(PLDHashTable *table, PLDHashEntryHdr *entry)
{
  ContentListHashEntry *e = NS_STATIC_CAST(ContentListHashEntry *, entry);
  return e->mContentList->GetKey();
}

PR_STATIC_CALLBACK(PLDHashNumber)
ContentListHashtableHashKey(PLDHashTable *table, const void *key)
{
  const nsContentListKey* list = NS_STATIC_CAST(const nsContentListKey *, key);
  return list->GetHash();
}

PR_STATIC_CALLBACK(PRBool)
ContentListHashtableMatchEntry(PLDHashTable *table,
                               const PLDHashEntryHdr *entry,
                               const void *key)
{
  const ContentListHashEntry *e =
    NS_STATIC_CAST(const ContentListHashEntry *, entry);
  const nsContentListKey* list1 = e->mContentList->GetKey();
  const nsContentListKey* list2 = NS_STATIC_CAST(const nsContentListKey *, key);

  return list1->Equals(*list2);
}

nsresult
NS_GetContentList(nsIDocument* aDocument, nsIAtom* aMatchAtom,
                  PRInt32 aMatchNameSpaceId, nsIContent* aRootContent,
                  nsIContentList** aInstancePtrResult)
{
  *aInstancePtrResult = nsnull;
  nsContentList* list = nsnull;

  static PLDHashTableOps hash_table_ops =
  {
    PL_DHashAllocTable,
    PL_DHashFreeTable,
    ContentListHashtableGetKey,
    ContentListHashtableHashKey,
    ContentListHashtableMatchEntry,
    PL_DHashMoveEntryStub,
    PL_DHashClearEntryStub,
    PL_DHashFinalizeStub
  };

  // Initialize the hashtable if needed.
  if (!gContentListHashTable.ops) {
    PRBool success = PL_DHashTableInit(&gContentListHashTable,
                                       &hash_table_ops, nsnull,
                                       sizeof(ContentListHashEntry),
                                       16);

    if (!success) {
      gContentListHashTable.ops = nsnull;
    }
  }
  
  ContentListHashEntry *entry = nsnull;
  // First we look in our hashtable.  Then we create a content list if needed
  if (gContentListHashTable.ops) {
    nsContentListKey hashKey(aDocument, aMatchAtom,
                             aMatchNameSpaceId, aRootContent);
    
    // A PL_DHASH_ADD is equivalent to a PL_DHASH_LOOKUP for cases
    // when the entry is already in the hashtable.
    entry = NS_STATIC_CAST(ContentListHashEntry *,
                           PL_DHashTableOperate(&gContentListHashTable,
                                                &hashKey,
                                                PL_DHASH_ADD));
    if (entry)
      list = entry->mContentList;
  }

  if (!list) {
    // We need to create a ContentList and add it to our new entry, if
    // we have an entry
    list = new nsContentList(aDocument, aMatchAtom,
                             aMatchNameSpaceId, aRootContent);
    if (entry) {
      if (list)
        entry->mContentList = list;
      else
        PL_DHashTableRawRemove(&gContentListHashTable, entry);
    }
  }

  NS_ENSURE_TRUE(list, NS_ERROR_OUT_OF_MEMORY);

  *aInstancePtrResult = list;
  NS_ADDREF(*aInstancePtrResult);
                               
  return NS_OK;
}


// nsContentList implementation

nsContentList::nsContentList(nsIDocument *aDocument,
                             nsIAtom* aMatchAtom,
                             PRInt32 aMatchNameSpaceId,
                             nsIContent* aRootContent)
  : nsBaseContentList(), nsContentListKey(aDocument, aMatchAtom, aMatchNameSpaceId, aRootContent)
{
  if (nsLayoutAtoms::wildcard == mMatchAtom) {
    mMatchAll = PR_TRUE;
  }
  else {
    mMatchAll = PR_FALSE;
  }
  mFunc = nsnull;
  mData = nsnull;
  mState = LIST_DIRTY;
  Init(aDocument);
}

nsContentList::nsContentList(nsIDocument *aDocument,
                             nsContentListMatchFunc aFunc,
                             const nsAString& aData,
                             nsIContent* aRootContent)
  : nsBaseContentList(), nsContentListKey(aDocument, nsnull, kNameSpaceID_Unknown, aRootContent)
{
  mFunc = aFunc;
  if (!aData.IsEmpty()) {
    mData = new nsString(aData);
    // If this fails, fail silently
  }
  else {
    mData = nsnull;
  }
  mMatchAtom = nsnull;
  mRootContent = aRootContent;
  mMatchAll = PR_FALSE;
  mState = LIST_DIRTY;
  Init(aDocument);
}

void nsContentList::Init(nsIDocument *aDocument)
{
  // We don't reference count the reference to the document
  // If the document goes away first, we'll be informed and we
  // can drop our reference.
  // If we go away first, we'll get rid of ourselves from the
  // document's observer list.
  mDocument = aDocument;
  if (mDocument) {
    mDocument->AddObserver(this);
  }
}

nsContentList::~nsContentList()
{
  RemoveFromHashtable();
  if (mDocument) {
    mDocument->RemoveObserver(this);
  }
  
  delete mData;
}


// QueryInterface implementation for nsContentList
NS_INTERFACE_MAP_BEGIN(nsContentList)
  NS_INTERFACE_MAP_ENTRY(nsIDOMHTMLCollection)
  NS_INTERFACE_MAP_ENTRY(nsIContentList)
  NS_INTERFACE_MAP_ENTRY_CONTENT_CLASSINFO(HTMLCollection)
NS_INTERFACE_MAP_END_INHERITING(nsBaseContentList)


NS_IMPL_ADDREF_INHERITED(nsContentList, nsBaseContentList)
NS_IMPL_RELEASE_INHERITED(nsContentList, nsBaseContentList)


NS_IMETHODIMP 
nsContentList::GetLength(PRUint32* aLength, PRBool aDoFlush)
{
  nsresult result = CheckDocumentExistence();
  if (NS_SUCCEEDED(result)) {
    BringSelfUpToDate(aDoFlush);
    
    *aLength = mElements.Count();
  }

  return result;
}

NS_IMETHODIMP 
nsContentList::Item(PRUint32 aIndex, nsIDOMNode** aReturn, PRBool aDoFlush)
{
  nsresult result = CheckDocumentExistence();
  if (NS_SUCCEEDED(result)) {
    if (mDocument && aDoFlush) {
      // Flush pending content changes Bug 4891
      mDocument->FlushPendingNotifications(PR_FALSE);
    }

    if (mState != LIST_UP_TO_DATE)
      PopulateSelf(aIndex+1);

    NS_ASSERTION(!mDocument || mState != LIST_DIRTY,
                 "PopulateSelf left the list in a dirty (useless) state!");

    nsIContent *element = NS_STATIC_CAST(nsIContent *,
                                         mElements.SafeElementAt(aIndex));
 
    if (element) {
      result = CallQueryInterface(element, aReturn);
    }
    else {
      *aReturn = nsnull;
    }
  }

  return result;
}

NS_IMETHODIMP
nsContentList::NamedItem(const nsAString& aName, nsIDOMNode** aReturn, PRBool aDoFlush)
{
  nsresult result = CheckDocumentExistence();

  if (NS_SUCCEEDED(result)) {
    BringSelfUpToDate(aDoFlush);
    
    PRInt32 i, count = mElements.Count();

    for (i = 0; i < count; i++) {
      nsIContent *content = NS_STATIC_CAST(nsIContent *,
                                           mElements.ElementAt(i));
      if (content) {
        nsAutoString name;
        // XXX Should it be an EqualsIgnoreCase?
        if (((content->GetAttr(kNameSpaceID_None, nsHTMLAtoms::name,
                               name) == NS_CONTENT_ATTR_HAS_VALUE) &&
             aName.Equals(name)) ||
            ((content->GetAttr(kNameSpaceID_None, nsHTMLAtoms::id,
                               name) == NS_CONTENT_ATTR_HAS_VALUE) &&
             aName.Equals(name))) {
          return CallQueryInterface(content, aReturn);
        }
      }
    }
  }

  *aReturn = nsnull;
  return result;
}

NS_IMETHODIMP
nsContentList::IndexOf(nsIContent *aContent, PRInt32& aIndex, PRBool aDoFlush)
{
  nsresult result = CheckDocumentExistence();
  if (NS_SUCCEEDED(result)) {
    BringSelfUpToDate(aDoFlush);
    
    aIndex = mElements.IndexOf(aContent);
  }

  return result;
}

NS_IMETHODIMP
nsContentList::GetLength(PRUint32* aLength)
{
  return GetLength(aLength, PR_TRUE);
}

NS_IMETHODIMP
nsContentList::Item(PRUint32 aIndex, nsIDOMNode** aReturn)
{
  return Item(aIndex, aReturn, PR_TRUE);
}

NS_IMETHODIMP
nsContentList::NamedItem(const nsAString& aName, nsIDOMNode** aReturn)
{
  return NamedItem(aName, aReturn, PR_TRUE);
}

NS_IMETHODIMP 
nsContentList::ContentAppended(nsIDocument *aDocument, nsIContent* aContainer,
                               PRInt32 aNewIndexInContainer)
{
  /*
   * If the state is LIST_DIRTY then we have no useful information in
   * our list and we want to put off doing work as much as possible.
   */
  if (mState == LIST_DIRTY) 
    return NS_OK;

  PRInt32 count;
  aContainer->ChildCount(count);

  /*
   * We want to handle the case of ContentAppended by sometimes
   * appending the content to our list, not just setting state to
   * LIST_DIRTY, since most of our ContentAppended notifications
   * should come during pageload and be at the end of the document.
   * Do a bit of work to see whether we could just append to what we
   * already have.
   */
  
  if ((count > 0) && IsDescendantOfRoot(aContainer)) {
    PRInt32 ourCount = mElements.Count();
    PRBool appendToList = PR_FALSE;
    if (ourCount == 0) {
      appendToList = PR_TRUE;
    } else {
      nsIContent* ourLastContent =
        NS_STATIC_CAST(nsIContent*, mElements.ElementAt(ourCount - 1));
      /*
       * We want to append instead of invalidating in two cases:
       * 1) aContainer is an ancestor of ourLastContent (this case
             covers aContainer == ourLastContent)
       * 2) aContainer comes after ourLastContent in document order
       */
      if (nsContentUtils::ContentIsDescendantOf(ourLastContent, aContainer)) {
        appendToList = PR_TRUE;
      } else {
        nsCOMPtr<nsIDOM3Node> ourLastDOM3Node(do_QueryInterface(ourLastContent));
        nsCOMPtr<nsIDOMNode> newNodeContainer(do_QueryInterface(aContainer));
        if (ourLastDOM3Node && newNodeContainer) {
          PRUint16 comparisonFlags;
          nsresult rv = ourLastDOM3Node->CompareTreePosition(newNodeContainer,
                                                             &comparisonFlags);
          if (NS_SUCCEEDED(rv) && 
              (comparisonFlags & nsIDOMNode::TREE_POSITION_FOLLOWING)) {
            appendToList = PR_TRUE;
          }
        }
      }
    }
    
    PRInt32 i;
    
    if (!appendToList) {
      // The new stuff is somewhere in the middle of our list; check
      // whether we need to invalidate
      nsCOMPtr<nsIContent> content;
      for (i = aNewIndexInContainer; i <= count-1; ++i) {
        aContainer->ChildAt(i, *getter_AddRefs(content));
        if (MatchSelf(content)) {
          // Uh-oh.  We're gonna have to add elements into the middle
          // of our list. That's not worth the effort.
          mState = LIST_DIRTY;
          break;
        }
      }
 
      return NS_OK;
    }

    /*
     * At this point we know we could append.  If we're not up to
     * date, however, that would be a bad idea -- it could miss some
     * content that we never picked up due to being lazy.  Further, we
     * may never get asked for this content... so don't grab it yet.
     */
    if (mState == LIST_LAZY) // be lazy
      return NS_OK;

    /*
     * We're up to date.  That means someone's actively using us; we
     * may as well grab this content....
     */
    nsCOMPtr<nsIContent> content;
    for (i = aNewIndexInContainer; i <= count-1; ++i) {
      aContainer->ChildAt(i, *getter_AddRefs(content));
      PRUint32 limit = PRUint32(-1);
      PopulateWith(content, PR_TRUE, limit);
    }
  }

  return NS_OK;
}

NS_IMETHODIMP 
nsContentList::ContentInserted(nsIDocument *aDocument,
                               nsIContent* aContainer,
                               nsIContent* aChild,
                               PRInt32 aIndexInContainer)
{
  if (mState == LIST_DIRTY)
    return NS_OK;

  if (IsDescendantOfRoot(aContainer) && MatchSelf(aChild))
    mState = LIST_DIRTY;
  
  return NS_OK;
}
 
NS_IMETHODIMP
nsContentList::ContentReplaced(nsIDocument *aDocument,
                               nsIContent* aContainer,
                               nsIContent* aOldChild,
                               nsIContent* aNewChild,
                               PRInt32 aIndexInContainer)
{
  if (mState == LIST_DIRTY)
    return NS_OK;
  
  if (IsDescendantOfRoot(aContainer)) {
    if (MatchSelf(aOldChild) || MatchSelf(aNewChild)) {
      mState = LIST_DIRTY;
    }
  }
  else if (ContainsRoot(aOldChild)) {
    DisconnectFromDocument();
  }

  return NS_OK;
}

NS_IMETHODIMP
nsContentList::ContentRemoved(nsIDocument *aDocument,
                              nsIContent* aContainer,
                              nsIContent* aChild,
                              PRInt32 aIndexInContainer)
{
  if (IsDescendantOfRoot(aContainer)) {
    if (MatchSelf(aChild)) {
      mState = LIST_DIRTY;
    }
  }
  else if (ContainsRoot(aChild)) {
    DisconnectFromDocument();
  }

  return NS_OK;
}

NS_IMETHODIMP
nsContentList::DocumentWillBeDestroyed(nsIDocument *aDocument)
{
  DisconnectFromDocument();
  Reset();
  
  return NS_OK;
}

PRBool
nsContentList::Match(nsIContent *aContent)
{
  if (!aContent)
    return PR_FALSE;

  if (mMatchAtom) {
    nsCOMPtr<nsINodeInfo> ni;
    aContent->GetNodeInfo(*getter_AddRefs(ni));

    if (!ni)
      return PR_FALSE;

    nsCOMPtr<nsIDOMNode> node(do_QueryInterface(aContent));

    if (!node)
      return PR_FALSE;

    PRUint16 type;
    node->GetNodeType(&type);

    if (type != nsIDOMNode::ELEMENT_NODE)
      return PR_FALSE;

    if (mMatchNameSpaceId == kNameSpaceID_Unknown) {
      return (mMatchAll || ni->Equals(mMatchAtom));
    }

    return ((mMatchAll && ni->NamespaceEquals(mMatchNameSpaceId)) ||
            ni->Equals(mMatchAtom, mMatchNameSpaceId));
  }
  else if (mFunc) {
    return (*mFunc)(aContent, mData);
  }

  return PR_FALSE;
}

nsresult
nsContentList::CheckDocumentExistence()
{
  nsresult result = NS_OK;
  if (!mDocument && mRootContent) {
    result = mRootContent->GetDocument(mDocument);
    if (mDocument) {
      mDocument->AddObserver(this);
      mState = LIST_DIRTY;
    }
  }

  return result;
}

PRBool 
nsContentList::MatchSelf(nsIContent *aContent)
{

  if (Match(aContent))
    return PR_TRUE;
  
  PRInt32 i, count = -1;

  aContent->ChildCount(count);
  nsCOMPtr<nsIContent> child;
  for (i = 0; i < count; i++) {
    aContent->ChildAt(i, *getter_AddRefs(child));
    if (MatchSelf(child)) {
      return PR_TRUE;
    }
  }
  
  return PR_FALSE;
}

void 
nsContentList::PopulateWith(nsIContent *aContent, PRBool aIncludeRoot,
                            PRUint32 & aElementsToAppend)
{
  if (aIncludeRoot) {
    if (Match(aContent)) {
      mElements.AppendElement(aContent);
      --aElementsToAppend;
      if (aElementsToAppend == 0)
        return;
    }
  }
  
  PRInt32 i, count;
  aContent->ChildCount(count);
  nsCOMPtr<nsIContent> child;
  for (i = 0; i < count; i++) {
    aContent->ChildAt(i, *getter_AddRefs(child));
    PopulateWith(child, PR_TRUE, aElementsToAppend);
    if (aElementsToAppend == 0)
      return;
  }
}

void 
nsContentList::PopulateWithStartingAfter(nsIContent *aStartRoot,
                                         nsIContent *aStartChild,
                                         PRUint32 & aElementsToAppend)
{
#ifdef DEBUG
  PRUint32 invariant = aElementsToAppend + mElements.Count();
#endif
  PRInt32 i = 0;
  if (aStartChild) {
    aStartRoot->IndexOf(aStartChild, i);
    NS_ASSERTION(i >= 0, "The start child must be a child of the start root!");
    ++i;  // move to one past
  }
  
  PRInt32 childCount;
  aStartRoot->ChildCount(childCount);
  nsCOMPtr<nsIContent> child;
  for ( ; i < childCount; ++i) {
    aStartRoot->ChildAt(i, *getter_AddRefs(child));
    PopulateWith(child, PR_TRUE, aElementsToAppend);
    NS_ASSERTION(aElementsToAppend + mElements.Count() == invariant,
                 "Something is awry in PopulateWith!");
    if (aElementsToAppend == 0)
      return;
  }
  
  nsCOMPtr<nsIContent> parent;
  aStartRoot->GetParent(*getter_AddRefs(parent));
  
  if (parent)
    PopulateWithStartingAfter(parent, aStartRoot, aElementsToAppend);
}

void 
nsContentList::PopulateSelf(PRUint32 aNeededLength)
{
  if (mState == LIST_DIRTY) {
    Reset();
  }
  PRUint32 count = mElements.Count();

  if (count >= aNeededLength) // We're all set
    return;

  PRUint32 elementsToAppend = aNeededLength - count;
#ifdef DEBUG
  PRUint32 invariant = elementsToAppend + mElements.Count();
#endif
  if (count != 0) {
    PopulateWithStartingAfter(NS_STATIC_CAST(nsIContent*,
                                             mElements.ElementAt(count - 1)),
                           nsnull,
                           elementsToAppend);
    NS_ASSERTION(elementsToAppend + mElements.Count() == invariant,
                 "Something is awry in PopulateWithStartingAfter!");
  } else if (mRootContent) {
    PopulateWith(mRootContent, PR_FALSE, elementsToAppend);
    NS_ASSERTION(elementsToAppend + mElements.Count() == invariant,
                 "Something is awry in PopulateWith!");
  }
  else if (mDocument) {
    nsCOMPtr<nsIContent> root;
    mDocument->GetRootContent(getter_AddRefs(root));
    if (root) {
      PopulateWith(root, PR_TRUE, elementsToAppend);
      NS_ASSERTION(elementsToAppend + mElements.Count() == invariant,
                   "Something is awry in PopulateWith!");
    }
  }

  if (mDocument) {
    if (elementsToAppend != 0)
      mState = LIST_UP_TO_DATE;
    else
      mState = LIST_LAZY;
  } else {
    // No document means we have to stay on our toes since we don't
    // get content notifications.
    mState = LIST_DIRTY;
  }
}

PRBool
nsContentList::IsDescendantOfRoot(nsIContent* aContainer) 
{
  if (!mRootContent) {
#ifdef DEBUG
    nsCOMPtr<nsIDocument> doc;
    aContainer->GetDocument(*getter_AddRefs(doc));
    NS_ASSERTION(doc == mDocument, "We should not get in here if aContainer is appended to some _other_ document!");
#endif
    return PR_TRUE;
  }

  if (!aContainer) {
    return PR_FALSE;
  }

  return nsContentUtils::ContentIsDescendantOf(aContainer, mRootContent);
}

PRBool
nsContentList::ContainsRoot(nsIContent* aContent)
{
  if (!mRootContent || !aContent) {
    return PR_FALSE;
  }

  return nsContentUtils::ContentIsDescendantOf(mRootContent, aContent);
}

void 
nsContentList::DisconnectFromDocument()
{
  if (mDocument) {
    // Our key will change... Best remove ourselves before that happens.
    RemoveFromHashtable();
    mDocument->RemoveObserver(this);
    mDocument = nsnull;
  }

  // We will get no more updates, so we can never know we're up to
  // date
  mState = LIST_DIRTY;
}

void
nsContentList::RemoveFromHashtable()
{
  if (!gContentListHashTable.ops)
    return;
    
  PL_DHashTableOperate(&gContentListHashTable,
                       GetKey(),
                       PL_DHASH_REMOVE);

  if (gContentListHashTable.entryCount == 0) {
    PL_DHashTableFinish(&gContentListHashTable);
    gContentListHashTable.ops = nsnull;
  }
}

void
nsContentList::BringSelfUpToDate(PRBool aDoFlush)
{
  if (mDocument && aDoFlush) {
    mDocument->FlushPendingNotifications(PR_FALSE); // Flush pending content changes Bug 4891
  }

  if (mState != LIST_UP_TO_DATE)
    PopulateSelf(PRUint32(-1));
    
  NS_ASSERTION(!mDocument || mState == LIST_UP_TO_DATE,
               "PopulateSelf dod not bring content list up to date!");
}