gecko-dev/accessible/src/msaa/nsAccessibleWrap.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla 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/MPL/
 *
 * 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) 2003
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 * Original Author: Aaron Leventhal (aaronl@netscape.com)
 *
 * 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
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#include "nsAccessibleWrap.h"
#include "nsIAccessibleSelectable.h"
#include "nsIAccessibleWin32Object.h"

// for the COM IEnumVARIANT solution in get_AccSelection()
#define _ATLBASE_IMPL
#include <atlbase.h>
extern CComModule _Module;
#define _ATLCOM_IMPL
#include <atlcom.h>

 /* For documentation of the accessibility architecture, 
 * see http://lxr.mozilla.org/seamonkey/source/accessible/accessible-docs.html
 */

//#define DEBUG_LEAKS

#ifdef DEBUG_LEAKS
static gAccessibles = 0;
#endif

CComModule _Module;

EXTERN_C GUID CDECL CLSID_Accessible =
{ 0x61044601, 0xa811, 0x4e2b, { 0xbb, 0xba, 0x17, 0xbf, 0xab, 0xd3, 0x29, 0xd7 } };

/*
 * Class nsAccessibleWrap
 */

//-----------------------------------------------------
// construction 
//-----------------------------------------------------
nsAccessibleWrap::nsAccessibleWrap(nsIDOMNode* aNode, nsIWeakReference *aShell): 
  nsAccessible(aNode, aShell), mCachedChildCount(-1), mEnumVARIANTPosition(0)
{
}

//-----------------------------------------------------
// destruction
//-----------------------------------------------------
nsAccessibleWrap::~nsAccessibleWrap()
{
}


// Microsoft COM QueryInterface
//-----------------------------------------------------
// IUnknown interface methods - see iunknown.h for documentation
//-----------------------------------------------------
STDMETHODIMP_(ULONG) nsAccessibleWrap::AddRef()
{
  return nsAccessNode::AddRef();
}

STDMETHODIMP_(ULONG) nsAccessibleWrap::Release()
{
  return nsAccessNode::Release();
}

STDMETHODIMP nsAccessibleWrap::QueryInterface(REFIID iid, void** ppv)
{
  *ppv = NULL;

  if (IID_IUnknown == iid || IID_IDispatch == iid || IID_IAccessible == iid)
    *ppv = NS_STATIC_CAST(IAccessible*, this);
  else if (IID_IEnumVARIANT == iid && !gIsEnumVariantSupportDisabled) {
    CacheMSAAChildren();
    if (mCachedChildCount > 0)  // Don't support this interface for leaf elements
      *ppv = NS_STATIC_CAST(IEnumVARIANT*, this);
  }
  else if (IID_IServiceProvider == iid) {
    *ppv = NS_STATIC_CAST(IServiceProvider*, this);
  }

  if (NULL == *ppv)
    return nsAccessNodeWrap::QueryInterface(iid, ppv);
    
  (NS_REINTERPRET_CAST(IUnknown*, *ppv))->AddRef();
  return S_OK;
}

//-----------------------------------------------------
// IAccessible methods
//-----------------------------------------------------


STDMETHODIMP nsAccessibleWrap::AccessibleObjectFromWindow(HWND hwnd,
                                                          DWORD dwObjectID,
                                                          REFIID riid,
                                                          void **ppvObject)
{
  // open the dll dynamically
  if (!gmAccLib) 
    gmAccLib =::LoadLibrary("OLEACC.DLL");  

  if (gmAccLib) {
    if (!gmAccessibleObjectFromWindow)
      gmAccessibleObjectFromWindow = (LPFNACCESSIBLEOBJECTFROMWINDOW)GetProcAddress(gmAccLib,"AccessibleObjectFromWindow");

    if (gmAccessibleObjectFromWindow)
      return gmAccessibleObjectFromWindow(hwnd, dwObjectID, riid, ppvObject);
  }

  return E_FAIL;
}

STDMETHODIMP nsAccessibleWrap::NotifyWinEvent(DWORD event,
                                              HWND hwnd,
                                              LONG idObjectType,
                                              LONG idObject)
{
  if (gmNotifyWinEvent)
    return gmNotifyWinEvent(event, hwnd, idObjectType, idObject);
    
  return E_FAIL;
}

STDMETHODIMP nsAccessibleWrap::get_accParent( IDispatch __RPC_FAR *__RPC_FAR *ppdispParent)
{
  nsCOMPtr<nsIAccessible> xpParentAccessible;
  GetAccParent(getter_AddRefs(xpParentAccessible));

  if (xpParentAccessible) {
    *ppdispParent = NativeAccessible(xpParentAccessible);
    return S_OK;
  }

  *ppdispParent = NULL;

  // If we have a widget but no parent nsIAccessible then we might have a native
  // widget parent that could give us a IAccessible. Lets check.

  void* wnd;
  GetOwnerWindow(&wnd);

  HWND pWnd = ::GetParent(NS_REINTERPRET_CAST(HWND, wnd));
  if (pWnd) {
    // get the accessible.
    void* ptr = nsnull;
    HRESULT result = AccessibleObjectFromWindow(pWnd, OBJID_WINDOW, IID_IAccessible, &ptr);
    if (SUCCEEDED(result)) {
      IAccessible* msaaParentAccessible = (IAccessible*)ptr;
      // got one? return it.
      if (msaaParentAccessible) {
        *ppdispParent = msaaParentAccessible;
        return NS_OK;
      }
    }
  }

  return E_FAIL;  
}

void nsAccessibleWrap::CacheMSAAChildren()
{
  mCachedChildCount = -1;  // Don't use old info
  if (mCachedChildCount < 0)
    GetCachedChild(-1); // This caches the children and sets mCachedChildCount
}

STDMETHODIMP nsAccessibleWrap::get_accChildCount( long __RPC_FAR *pcountChildren)
{
  CacheMSAAChildren();
  
  *pcountChildren = mCachedChildCount;

  return S_OK;
}

STDMETHODIMP nsAccessibleWrap::get_accChild( 
      /* [in] */ VARIANT varChild,
      /* [retval][out] */ IDispatch __RPC_FAR *__RPC_FAR *ppdispChild)
{
  *ppdispChild = NULL;

  if (varChild.vt != VT_I4)
    return E_FAIL;

  if (varChild.lVal == CHILDID_SELF) {
    *ppdispChild = this;
    AddRef();
    return S_OK;
  }

  CacheMSAAChildren();

  *ppdispChild = GetCachedChild(varChild.lVal - 1); // already addrefed

  return (*ppdispChild)? S_OK: E_FAIL;
}

STDMETHODIMP nsAccessibleWrap::get_accName( 
      /* [optional][in] */ VARIANT varChild,
      /* [retval][out] */ BSTR __RPC_FAR *pszName)
{
  *pszName = NULL;
  nsCOMPtr<nsIAccessible> xpAccessible;
  GetXPAccessibleFor(varChild, getter_AddRefs(xpAccessible));
  if (xpAccessible) {
    nsAutoString name;
    if (NS_FAILED(xpAccessible->GetAccName(name)))
      return S_FALSE;

    *pszName = ::SysAllocString(name.get());
  }

  return S_OK;
}


STDMETHODIMP nsAccessibleWrap::get_accValue( 
      /* [optional][in] */ VARIANT varChild,
      /* [retval][out] */ BSTR __RPC_FAR *pszValue)
{
  *pszValue = NULL;
  nsCOMPtr<nsIAccessible> xpAccessible;
  GetXPAccessibleFor(varChild, getter_AddRefs(xpAccessible));
  if (xpAccessible) {
    nsAutoString value;
    if (NS_FAILED(xpAccessible->GetAccValue(value)))
      return S_FALSE;

    *pszValue = ::SysAllocString(value.get());
  }

  return S_OK;
}


STDMETHODIMP nsAccessibleWrap::get_accDescription( 
      /* [optional][in] */ VARIANT varChild,
      /* [retval][out] */ BSTR __RPC_FAR *pszDescription)
{
  *pszDescription = NULL;
  nsCOMPtr<nsIAccessible> xpAccessible;
  GetXPAccessibleFor(varChild, getter_AddRefs(xpAccessible));
  if (xpAccessible) {
     nsAutoString description;
     if (NS_FAILED(xpAccessible->GetAccDescription(description)))
       return S_FALSE;

     *pszDescription = ::SysAllocString(description.get());
  }

  return S_OK;
}

STDMETHODIMP nsAccessibleWrap::get_accRole( 
      /* [optional][in] */ VARIANT varChild,
      /* [retval][out] */ VARIANT __RPC_FAR *pvarRole)
{
  VariantInit(pvarRole);
  pvarRole->vt = VT_I4;

  nsCOMPtr<nsIAccessible> xpAccessible;
  GetXPAccessibleFor(varChild, getter_AddRefs(xpAccessible));

  if (!xpAccessible)
    return E_FAIL;

  PRUint32 role = 0;
  if (NS_FAILED(xpAccessible->GetAccRole(&role)))
    return E_FAIL;

  pvarRole->lVal = role;
  return S_OK;
}

STDMETHODIMP nsAccessibleWrap::get_accState( 
      /* [optional][in] */ VARIANT varChild,
      /* [retval][out] */ VARIANT __RPC_FAR *pvarState)
{
  VariantInit(pvarState);
  pvarState->vt = VT_I4;
  pvarState->lVal = 0;

  nsCOMPtr<nsIAccessible> xpAccessible;
  GetXPAccessibleFor(varChild, getter_AddRefs(xpAccessible));
  if (!xpAccessible)
    return E_FAIL;

  PRUint32 state;
  if (NS_FAILED(xpAccessible->GetAccState(&state)))
    return E_FAIL;

  pvarState->lVal = state;

  return S_OK;
}


STDMETHODIMP nsAccessibleWrap::get_accHelp( 
      /* [optional][in] */ VARIANT varChild,
      /* [retval][out] */ BSTR __RPC_FAR *pszHelp)
{
  *pszHelp = NULL;
  return S_FALSE;
}

STDMETHODIMP nsAccessibleWrap::get_accHelpTopic( 
      /* [out] */ BSTR __RPC_FAR *pszHelpFile,
      /* [optional][in] */ VARIANT varChild,
      /* [retval][out] */ long __RPC_FAR *pidTopic)
{
  *pszHelpFile = NULL;
  *pidTopic = 0;
  return E_NOTIMPL;
}

STDMETHODIMP nsAccessibleWrap::get_accKeyboardShortcut( 
      /* [optional][in] */ VARIANT varChild,
      /* [retval][out] */ BSTR __RPC_FAR *pszKeyboardShortcut)
{
  *pszKeyboardShortcut = NULL;
  nsCOMPtr<nsIAccessible> xpAccessible;
  GetXPAccessibleFor(varChild, getter_AddRefs(xpAccessible));
  if (xpAccessible) {
    nsAutoString shortcut;
    nsresult rv = xpAccessible->GetAccKeyboardShortcut(shortcut);
    if (NS_FAILED(rv))
      return S_FALSE;

    *pszKeyboardShortcut = ::SysAllocString(shortcut.get());
    return S_OK;
  }
  return S_FALSE;
}

STDMETHODIMP nsAccessibleWrap::get_accFocus( 
      /* [retval][out] */ VARIANT __RPC_FAR *pvarChild)
{
  // Return the current nsIAccessible that has focus
  VariantInit(pvarChild);

  nsCOMPtr<nsIAccessible> focusedAccessible;
  if (NS_SUCCEEDED(GetAccFocused(getter_AddRefs(focusedAccessible)))) {
    pvarChild->vt = VT_DISPATCH;
    pvarChild->pdispVal = NativeAccessible(focusedAccessible);
    return S_OK;
  }

  pvarChild->vt = VT_EMPTY;
  return E_FAIL;
}

/**
  * This method is called when a client wants to know which children of a node
  *  are selected. Currently we only handle this for HTML selects, which are the
  *  only nsIAccessible objects to implement nsIAccessibleSelectable.
  *
  * The VARIANT return value arguement is expected to either contain a single IAccessible
  *  or an IEnumVARIANT of IAccessibles. We return the IEnumVARIANT regardless of the number
  *  of options selected, unless there are none selected in which case we return an empty
  *  VARIANT.
  *
  * The typedefs at the beginning set up the structure that will contain an array 
  *  of the IAccessibles. It implements the IEnumVARIANT interface, allowing us to 
  *  use it to return the IAccessibles in the VARIANT.
  *
  * We get the selected options from the select's accessible object and then put create 
  *  IAccessible objects for them and put those in the CComObject<EnumeratorType> 
  *  object. Then we put the CComObject<EnumeratorType> object in the VARIANT and return.
  *
  * returns a VT_EMPTY VARIANT if:
  *  - there are no options in the select
  *  - none of the options are selected
  *  - there is an error QIing to IEnumVARIANT
  *  - The object is not the type that can have children selected
  */
STDMETHODIMP nsAccessibleWrap::get_accSelection(VARIANT __RPC_FAR *pvarChildren)
{
  typedef VARIANT                      ItemType;              /* type of the object to be stored in container */
  typedef ItemType                     EnumeratorExposedType; /* the type of the item exposed by the enumerator interface */
  typedef IEnumVARIANT                 EnumeratorInterface;   /* a COM enumerator ( IEnumXXXXX ) interface */
  typedef _Copy<EnumeratorExposedType> EnumeratorCopyPolicy;  /* Copy policy class */
  typedef CComEnum<EnumeratorInterface,
                   &__uuidof(EnumeratorInterface),
                   EnumeratorExposedType,
                   EnumeratorCopyPolicy > EnumeratorType;

  IEnumVARIANT* pUnk = NULL;
  CComObject<EnumeratorType>* pEnum = NULL;
  VariantInit(pvarChildren);
  pvarChildren->vt = VT_EMPTY;

  nsCOMPtr<nsIAccessibleSelectable> select;
  nsAccessNode::QueryInterface(NS_GET_IID(nsIAccessibleSelectable), getter_AddRefs(select));
  //nsCOMPtr<nsIAccessibleSelectable> select(do_QueryInterface(this)); // aaronl is this correct?

  if (select) {  // do we have an nsIAccessibleSelectable?
    // we have an accessible that can have children selected
    nsCOMPtr<nsISupportsArray> selectedOptions;
    // gets the selected options as nsIAccessibles.
    select->GetSelectedChildren(getter_AddRefs(selectedOptions));
    if (selectedOptions) { // false if the select has no children or none are selected
      PRUint32 length;
      selectedOptions->Count(&length);
      CComVariant* optionArray = new CComVariant[length]; // needs to be a CComVariant to go into the EnumeratorType object

      // 1) Populate an array to store in the enumeration
      for (PRUint32 i = 0 ; i < length ; i++) {
        nsCOMPtr<nsISupports> tempOption;
        selectedOptions->GetElementAt(i,getter_AddRefs(tempOption)); // this expects an nsISupports
        if (tempOption) {
          nsCOMPtr<nsIAccessible> tempAccess(do_QueryInterface(tempOption));
          if ( tempAccess ) {
            optionArray[i] = NativeAccessible(tempAccess);
          }
        }
      }

      // 2) Create and initialize the enumeration
      HRESULT hr = CComObject<EnumeratorType>::CreateInstance(&pEnum);
      pEnum->Init(&optionArray[0], &optionArray[length], NULL, AtlFlagCopy);
      pEnum->QueryInterface(IID_IEnumVARIANT, reinterpret_cast<void**>(&pUnk));
      delete [] optionArray; // clean up, the Init call copies the data (AtlFlagCopy)

      // 3) Put the enumerator in the VARIANT
      if (!pUnk)
        return NS_ERROR_FAILURE;
      pvarChildren->vt = VT_UNKNOWN;    // this must be VT_UNKNOWN for an IEnumVARIANT
      pvarChildren->punkVal = pUnk;
    }
  }
  return S_OK;
}

STDMETHODIMP nsAccessibleWrap::get_accDefaultAction( 
      /* [optional][in] */ VARIANT varChild,
      /* [retval][out] */ BSTR __RPC_FAR *pszDefaultAction)
{
  *pszDefaultAction = NULL;
  nsCOMPtr<nsIAccessible> xpAccessible;
  GetXPAccessibleFor(varChild, getter_AddRefs(xpAccessible));
  if (xpAccessible) {
    nsAutoString defaultAction;
    if (NS_FAILED(xpAccessible->GetAccActionName(0, defaultAction)))
      return S_FALSE;

    *pszDefaultAction = ::SysAllocString(defaultAction.get());
  }

  return S_OK;
}

STDMETHODIMP nsAccessibleWrap::accSelect( 
      /* [in] */ long flagsSelect,
      /* [optional][in] */ VARIANT varChild)
{
  // currently only handle focus and selection
  nsCOMPtr<nsIAccessible> xpAccessible;
  GetXPAccessibleFor(varChild, getter_AddRefs(xpAccessible));

  if (flagsSelect & (SELFLAG_TAKEFOCUS|SELFLAG_TAKESELECTION|SELFLAG_REMOVESELECTION))
  {
    if (flagsSelect & SELFLAG_TAKEFOCUS)
      xpAccessible->AccTakeFocus();

    if (flagsSelect & SELFLAG_TAKESELECTION)
      xpAccessible->AccTakeSelection();

    if (flagsSelect & SELFLAG_REMOVESELECTION)
      xpAccessible->AccRemoveSelection();

    return S_OK;
  }

  return E_FAIL;
}

STDMETHODIMP nsAccessibleWrap::accLocation( 
      /* [out] */ long __RPC_FAR *pxLeft,
      /* [out] */ long __RPC_FAR *pyTop,
      /* [out] */ long __RPC_FAR *pcxWidth,
      /* [out] */ long __RPC_FAR *pcyHeight,
      /* [optional][in] */ VARIANT varChild)
{
  nsCOMPtr<nsIAccessible> xpAccessible;
  GetXPAccessibleFor(varChild, getter_AddRefs(xpAccessible));

  if (xpAccessible) {
    PRInt32 x, y, width, height;
    if (NS_FAILED(xpAccessible->AccGetBounds(&x, &y, &width, &height)))
      return E_FAIL;

    *pxLeft = x;
    *pyTop = y;
    *pcxWidth = width;
    *pcyHeight = height;
    return S_OK;
  }

  return E_FAIL;  
}

IAccessible *
nsAccessibleWrap::GetCachedChild(long aChildNum)
{
  // aChildNum of -1 just counts up the children
  // and stores the value in mCachedChildCount
  VARIANT varStart, varResult;
  VariantInit(&varStart);
  varStart.lVal = CHILDID_SELF;
  varStart.vt = VT_I4;

  accNavigate(NAVDIR_FIRSTCHILD, varStart, &varResult);
  for (long index = 0; varResult.vt == VT_DISPATCH; ++index) {
    IAccessible *msaaAccessible = NS_STATIC_CAST(IAccessible*, varResult.pdispVal);
    if (aChildNum == index)
      return msaaAccessible;
    msaaAccessible->accNavigate(NAVDIR_NEXT, varStart, &varResult);
    msaaAccessible->Release();
  }
  if (mCachedChildCount < 0)
    mCachedChildCount = index;
  return nsnull;
}

STDMETHODIMP nsAccessibleWrap::accNavigate( 
      /* [in] */ long navDir,
      /* [optional][in] */ VARIANT varStart,
      /* [retval][out] */ VARIANT __RPC_FAR *pvarEndUpAt)
{
  nsCOMPtr<nsIAccessible> xpAccessibleStart, xpAccessibleResult;
  GetXPAccessibleFor(varStart, getter_AddRefs(xpAccessibleStart));

  nsCOMPtr<nsIAccessible> xpAccessibleThis(NS_STATIC_CAST(nsIAccessible*, this));
  PRBool isNavigatingFromSelf = (xpAccessibleStart == xpAccessibleThis);

  VariantInit(pvarEndUpAt);

  IAccessible* msaaAccessible = nsnull;

  switch(navDir) {
    case NAVDIR_DOWN: 
      xpAccessibleStart->AccNavigateDown(getter_AddRefs(xpAccessibleResult));
      break;
    case NAVDIR_FIRSTCHILD:
      xpAccessibleStart->GetAccFirstChild(getter_AddRefs(xpAccessibleResult));
      break;
    case NAVDIR_LASTCHILD:
      xpAccessibleStart->GetAccLastChild(getter_AddRefs(xpAccessibleResult));
      break;
    case NAVDIR_LEFT:
      xpAccessibleStart->AccNavigateLeft(getter_AddRefs(xpAccessibleResult));
      break;
    case NAVDIR_NEXT:
      xpAccessibleStart->GetAccNextSibling(getter_AddRefs(xpAccessibleResult));
      break;
    case NAVDIR_PREVIOUS:
      xpAccessibleStart->GetAccPreviousSibling(getter_AddRefs(xpAccessibleResult));
      break;
    case NAVDIR_RIGHT:
      xpAccessibleStart->AccNavigateRight(getter_AddRefs(xpAccessibleResult));
      break;
    case NAVDIR_UP:
      xpAccessibleStart->AccNavigateUp(getter_AddRefs(xpAccessibleResult));
      break;
  }

  if (xpAccessibleResult) {
    pvarEndUpAt->pdispVal = NativeAccessible(xpAccessibleResult);
    pvarEndUpAt->vt = VT_DISPATCH;
    return NS_OK;
  } 
  pvarEndUpAt->vt = VT_EMPTY;
  return E_FAIL;
}

STDMETHODIMP nsAccessibleWrap::accHitTest( 
      /* [in] */ long xLeft,
      /* [in] */ long yTop,
      /* [retval][out] */ VARIANT __RPC_FAR *pvarChild)
{
  VariantInit(pvarChild);

  // convert to window coords
  nsCOMPtr<nsIAccessible> xpAccessible;

  xLeft = xLeft;
  yTop = yTop;

  AccGetAt(xLeft, yTop, getter_AddRefs(xpAccessible));

  // if we got a child
  if (xpAccessible) {
    // if the child is us
    if (xpAccessible == NS_STATIC_CAST(nsIAccessible*, this)) {
      pvarChild->vt = VT_I4;
      pvarChild->lVal = CHILDID_SELF;
    } else { // its not create an Accessible for it.
      pvarChild->vt = VT_DISPATCH;
      pvarChild->pdispVal = NativeAccessible(xpAccessible);
    }
  } else {
      // no child at that point
      pvarChild->vt = VT_EMPTY;
      return E_FAIL;
  }

  return S_OK;
}

STDMETHODIMP nsAccessibleWrap::accDoDefaultAction( 
      /* [optional][in] */ VARIANT varChild)
{
  nsCOMPtr<nsIAccessible> xpAccessible;
  GetXPAccessibleFor(varChild, getter_AddRefs(xpAccessible));

  if (!xpAccessible || FAILED(xpAccessible->AccDoAction(0))) {
    return E_FAIL;
  }
  return S_OK;
}

STDMETHODIMP nsAccessibleWrap::put_accName( 
      /* [optional][in] */ VARIANT varChild,
      /* [in] */ BSTR szName)
{
  return E_NOTIMPL;
}

STDMETHODIMP nsAccessibleWrap::put_accValue( 
      /* [optional][in] */ VARIANT varChild,
      /* [in] */ BSTR szValue)
{
  return E_NOTIMPL;
}

#include "mshtml.h"

STDMETHODIMP
nsAccessibleWrap::QueryService(REFGUID guidService, REFIID iid, void** ppv)
{
  *ppv = NULL;

  if (iid == IID_ISimpleDOMNode) {
    return nsAccessNodeWrap::QueryInterface(iid, ppv);
  }
    
  return E_NOINTERFACE;
}


STDMETHODIMP
nsAccessibleWrap::Next(ULONG aNumElementsRequested, VARIANT FAR* pvar, ULONG FAR* aNumElementsFetched)
{
  CacheMSAAChildren();
  *aNumElementsFetched = 0;

  if (aNumElementsRequested <= 0 || !pvar ||
      mEnumVARIANTPosition >= mCachedChildCount) {
    return E_FAIL;
  }

  VARIANT varStart;
  VariantInit(&varStart);
  varStart.lVal = CHILDID_SELF;
  varStart.vt = VT_I4;

  accNavigate(NAVDIR_FIRSTCHILD, varStart, &pvar[0]);

  for (long childIndex = 0; pvar[*aNumElementsFetched].vt == VT_DISPATCH; ++childIndex) {
    PRBool wasAccessibleFetched = PR_FALSE;
    nsAccessibleWrap *msaaAccessible = 
      NS_STATIC_CAST(nsAccessibleWrap*, pvar[*aNumElementsFetched].pdispVal);
    if (childIndex >= mEnumVARIANTPosition) {
      if (++*aNumElementsFetched >= aNumElementsRequested)
        break;
      wasAccessibleFetched = PR_TRUE;
    }
    msaaAccessible->accNavigate(NAVDIR_NEXT, varStart, &pvar[*aNumElementsFetched] );
    if (!wasAccessibleFetched)
      msaaAccessible->nsAccessNode::Release(); // this accessible will not be received by the caller
  }

  mEnumVARIANTPosition += *aNumElementsFetched;
  return NOERROR;
}

STDMETHODIMP
nsAccessibleWrap::Skip(ULONG aNumElements)
{
  CacheMSAAChildren();

  mEnumVARIANTPosition += aNumElements;

  if (mEnumVARIANTPosition > mCachedChildCount)
  {
    mEnumVARIANTPosition = mCachedChildCount;
    return S_FALSE;
  }
  return NOERROR;
}

STDMETHODIMP 
nsAccessibleWrap::Reset(void)
{
  mEnumVARIANTPosition = 0;
  return NOERROR;
}

STDMETHODIMP
nsAccessibleWrap::Clone(IEnumVARIANT FAR* FAR* ppenum)
{
  // Clone could be bad, the cloned items aren't tracked for shutdown
  // Then again, as long as the client releases the items in time, we're okay
  *ppenum = nsnull;
  CacheMSAAChildren();

  nsAccessibleWrap *accessibleWrap = new nsAccessibleWrap(mDOMNode, mPresShell);
  if (!accessibleWrap)
    return E_FAIL;
  accessibleWrap->Init(mRootAccessibleDoc);

  IAccessible *msaaAccessible = NS_STATIC_CAST(IAccessible*, accessibleWrap);
  msaaAccessible->AddRef();
  QueryInterface(IID_IEnumVARIANT, (void**)ppenum);
  if (*ppenum)
    (*ppenum)->Skip(mEnumVARIANTPosition); // QI addrefed
  msaaAccessible->Release();

  return NOERROR;
}
        

// For IDispatch support
STDMETHODIMP 
nsAccessibleWrap::GetTypeInfoCount(UINT *p)
{
  *p = 0;
  return E_NOTIMPL;
}

// For IDispatch support
STDMETHODIMP nsAccessibleWrap::GetTypeInfo(UINT i, LCID lcid, ITypeInfo **ppti)
{
  *ppti = 0;
  return E_NOTIMPL;
}

// For IDispatch support
STDMETHODIMP 
nsAccessibleWrap::GetIDsOfNames(REFIID riid, LPOLESTR *rgszNames,
                           UINT cNames, LCID lcid, DISPID *rgDispId)
{
  return E_NOTIMPL;
}

// For IDispatch support
STDMETHODIMP nsAccessibleWrap::Invoke(DISPID dispIdMember, REFIID riid,
    LCID lcid, WORD wFlags, DISPPARAMS *pDispParams,
    VARIANT *pVarResult, EXCEPINFO *pExcepInfo, UINT *puArgErr)
{
  return E_NOTIMPL;
}


NS_IMETHODIMP nsAccessibleWrap::GetNativeInterface(void **aOutAccessible)
{
  *aOutAccessible = NS_STATIC_CAST(IAccessible*, this);
  NS_ADDREF_THIS();
  return NS_OK;
}

        
//------- Helper methods ---------

IDispatch *nsAccessibleWrap::NativeAccessible(nsIAccessible *aXPAccessible)
{
  nsCOMPtr<nsIAccessibleWin32Object> accObject(do_QueryInterface(aXPAccessible));
  if (accObject) {
    void* hwnd;
    accObject->GetHwnd(&hwnd);
    if (hwnd) {
      IDispatch *retval = nsnull;
      AccessibleObjectFromWindow(NS_REINTERPRET_CAST(HWND, hwnd), 
        OBJID_CLIENT, IID_IAccessible, (void **) &retval);
      return retval;
    }
  }

  nsCOMPtr<nsIAccessNode> accessNode(do_QueryInterface(aXPAccessible));
  accessNode->Init(mRootAccessibleDoc);

  IAccessible *msaaAccessible;
  aXPAccessible->GetNativeInterface((void**)&msaaAccessible);

  return NS_STATIC_CAST(IDispatch*, msaaAccessible);
}


void nsAccessibleWrap::GetXPAccessibleFor(VARIANT varChild, nsIAccessible **aXPAccessible)
{
  *aXPAccessible = nsnull;

  // if its us real easy - this seems to always be the case
  if (varChild.lVal == CHILDID_SELF) {
    *aXPAccessible = NS_STATIC_CAST(nsIAccessible*, this);
  } 
  else {
    // XXX It is rare to use a VARIANT with a child num
    // so optimizing this is not a priority
    // We can come back it do it later, if there are perf problems
    // with a specific assistive technology
    nsCOMPtr<nsIAccessible> xpAccessible, nextAccessible;
    GetAccFirstChild(getter_AddRefs(xpAccessible));
    for (PRInt32 index = 0; xpAccessible; index ++) {
      if (varChild.lVal == index) {
        *aXPAccessible = xpAccessible;
        break;
      }
      nextAccessible = xpAccessible;
      nextAccessible->GetAccNextSibling(getter_AddRefs(xpAccessible));
    }
  }
  NS_IF_ADDREF(*aXPAccessible);
}