Implementation of the ReleaseStgMedium method.

[wine/multimedia.git] / ole / ole2.c

/*
 *      OLE2 library
 *
 *      Copyright 1995  Martin von Loewis
 *      Copyright 1999  Francis Beaudet
 */

#include <assert.h>

#include "winuser.h"
#include "winerror.h"
#include "ole2.h"
#include "process.h"
#include "wine/obj_clientserver.h"
#include "debug.h"

/******************************************************************************
 * These are static/global variables and internal data structures that the 
 * OLE module uses to maintain it's state.
 */
typedef struct tagDropTargetNode
{
  HWND          hwndTarget;
  IDropTarget*    dropTarget;
  struct tagDropTargetNode* prevDropTarget;
  struct tagDropTargetNode* nextDropTarget;
} DropTargetNode;

typedef struct tagTrackerWindowInfo
{
  IDataObject* dataObject;
  IDropSource* dropSource;
  DWORD        dwOKEffect;
  DWORD*       pdwEffect;
  BOOL       trackingDone;
  HRESULT      returnValue;

  BOOL       escPressed;
  HWND       curDragTargetHWND;
  IDropTarget* curDragTarget;
} TrackerWindowInfo;

/*
 * This is the lock count on the OLE library. It is controlled by the
 * OLEInitialize/OLEUninitialize methods.
 */
static ULONG OLE_moduleLockCount = 0;

/*
 * Name of our registered window class.
 */
static const char OLEDD_DRAGTRACKERCLASS[] = "WineDragDropTracker32";

/*
 * This is the head of the Drop target container.
 */
static DropTargetNode* targetListHead = NULL;

/******************************************************************************
 * These are the prototypes of the utility methods used for OLE Drag n Drop
 */
static void            OLEDD_Initialize();
static void            OLEDD_UnInitialize();
static void            OLEDD_InsertDropTarget(
                         DropTargetNode* nodeToAdd);
static DropTargetNode* OLEDD_ExtractDropTarget(
                         HWND hwndOfTarget);
static DropTargetNode* OLEDD_FindDropTarget(
                         HWND hwndOfTarget);
static LRESULT WINAPI  OLEDD_DragTrackerWindowProc(
                         HWND   hwnd, 
                         UINT   uMsg,
                         WPARAM wParam, 
                         LPARAM   lParam);
static void OLEDD_TrackMouseMove(
                         TrackerWindowInfo* trackerInfo,
                         POINT            mousePos,
                         DWORD              keyState);
static void OLEDD_TrackStateChange(
                         TrackerWindowInfo* trackerInfo,
                         POINT            mousePos,
                         DWORD              keyState);
static DWORD OLEDD_GetButtonState();


/******************************************************************************
 *              OleBuildVersion [OLE2.1]
 */
DWORD WINAPI OleBuildVersion(void)
{
    TRACE(ole,"(void)\n");
    return (rmm<<16)+rup;
}

/***********************************************************************
 *           OleInitialize       (OLE2.2) (OLE32.108)
 */
HRESULT WINAPI OleInitialize(LPVOID reserved)
{
  HRESULT hr;

  TRACE(ole, "(%p)\n", reserved);

  /*
   * The first duty of the OleInitialize is to initialize the COM libraries.
   */
  hr = CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);

  /*
   * If the CoInitializeEx call failed, the OLE libraries can't be 
   * initialized.
   */
  if (FAILED(hr))
    return hr;    

  /*
   * Then, it has to initialize the OLE specific modules.
   * This includes:
   *     Clipboard
   *     Drag and Drop
   *     Object linking and Embedding
   *     In-place activation
   */
  if (OLE_moduleLockCount==0)
{
    /* 
     * Initialize the libraries.
     */
    TRACE(ole, "() - Initializing the OLE libraries\n");

    /*
     * Drag and Drop
     */
    OLEDD_Initialize();
}

  /*
   * Then, we increase the lock count on the OLE module.
   */
  OLE_moduleLockCount++;  

  return hr;
}

/******************************************************************************
 *              CoGetCurrentProcess     [COMPOBJ.34] [OLE2.2][OLE32.108]
 *
 * NOTES
 *   Is DWORD really the correct return type for this function?
 */
DWORD WINAPI CoGetCurrentProcess(void) {
        return (DWORD)PROCESS_Current();
}

/******************************************************************************
 *              OleUninitialize [OLE2.3] [OLE32.131]
 */
void WINAPI OleUninitialize(void)
{
  TRACE(ole, "()\n");

  /*
   * Decrease the lock count on the OLE module.
   */
  OLE_moduleLockCount--;

  /*
   * If we hit the bottom of the lock stack, free the libraries.
   */
  if (OLE_moduleLockCount==0)
  {
    /*
     * Actually free the libraries.
     */
    TRACE(ole, "() - Freeing the last reference count\n");

    /*
     * Drag and Drop
     */
    OLEDD_UnInitialize();
  }
  
  /*
   * Then, uninitialize the COM libraries.
   */
  CoUninitialize();
}

/***********************************************************************
 *           OleFlushClipboard   [OLE2.76]
 */
HRESULT WINAPI OleFlushClipboard16(void)
{
    return S_OK;
}

/***********************************************************************
 *           OleSetClipboard     [OLE32.127]
 */
HRESULT WINAPI OleSetClipboard(LPVOID pDataObj)
{
    FIXME(ole,"(%p), stub!\n", pDataObj);
    return S_OK;
}

/******************************************************************************
 *              CoRegisterMessageFilter32       [OLE32.38]
 */
HRESULT WINAPI CoRegisterMessageFilter(
    LPMESSAGEFILTER lpMessageFilter,    /* Pointer to interface */
    LPMESSAGEFILTER *lplpMessageFilter  /* Indirect pointer to prior instance if non-NULL */
) {
    FIXME(ole,"stub\n");
    if (lplpMessageFilter) {
        *lplpMessageFilter = NULL;
    }
    return S_OK;
}

/******************************************************************************
 *              OleInitializeWOW        [OLE32.109]
 */
HRESULT WINAPI OleInitializeWOW(DWORD x) {
        FIXME(ole,"(0x%08lx),stub!\n",x);
        return 0;
}

/***********************************************************************
 *           RegisterDragDrop16 (OLE2.35)
 */
HRESULT WINAPI RegisterDragDrop16(
        HWND16 hwnd,
        LPDROPTARGET pDropTarget
) {
        FIXME(ole,"(0x%04x,%p),stub!\n",hwnd,pDropTarget);
        return S_OK;
}

/***********************************************************************
 *           RegisterDragDrop32 (OLE32.139)
 */
HRESULT WINAPI RegisterDragDrop(
        HWND hwnd,
        LPDROPTARGET pDropTarget) 
{
  DropTargetNode* dropTargetInfo;

  TRACE(ole,"(0x%x,%p)\n", hwnd, pDropTarget);

  /*
   * First, check if the window is already registered.
   */
  dropTargetInfo = OLEDD_FindDropTarget(hwnd);

  if (dropTargetInfo!=NULL)
    return DRAGDROP_E_ALREADYREGISTERED;

  /*
   * If it's not there, we can add it. We first create a node for it.
   */
  dropTargetInfo = HeapAlloc(GetProcessHeap(), 0, sizeof(DropTargetNode));

  if (dropTargetInfo==NULL)
    return E_OUTOFMEMORY;

  dropTargetInfo->hwndTarget     = hwnd;
  dropTargetInfo->prevDropTarget = NULL;
  dropTargetInfo->nextDropTarget = NULL;

  /*
   * Don't forget that this is an interface pointer, need to nail it down since
   * we keep a copy of it.
   */
  dropTargetInfo->dropTarget  = pDropTarget;
  IDropTarget_AddRef(dropTargetInfo->dropTarget);
  
  OLEDD_InsertDropTarget(dropTargetInfo);

        return S_OK;
}

/***********************************************************************
 *           RevokeDragDrop16 (OLE2.36)
 */
HRESULT WINAPI RevokeDragDrop16(
        HWND16 hwnd
) {
        FIXME(ole,"(0x%04x),stub!\n",hwnd);
        return S_OK;
}

/***********************************************************************
 *           RevokeDragDrop32 (OLE32.141)
 */
HRESULT WINAPI RevokeDragDrop(
        HWND hwnd)
{
  DropTargetNode* dropTargetInfo;

  TRACE(ole,"(0x%x)\n", hwnd);

  /*
   * First, check if the window is already registered.
   */
  dropTargetInfo = OLEDD_ExtractDropTarget(hwnd);

  /*
   * If it ain't in there, it's an error.
   */
  if (dropTargetInfo==NULL)
    return DRAGDROP_E_NOTREGISTERED;

  /*
   * If it's in there, clean-up it's used memory and
   * references
   */
  IDropTarget_Release(dropTargetInfo->dropTarget);
  HeapFree(GetProcessHeap(), 0, dropTargetInfo);  

        return S_OK;
}

/***********************************************************************
 *           OleRegGetUserType (OLE32.122)
 */
HRESULT WINAPI OleRegGetUserType( 
        REFCLSID clsid, 
        DWORD dwFormOfType,
        LPOLESTR* pszUserType)
{
        FIXME(ole,",stub!\n");
        return S_OK;
}

/***********************************************************************
 * DoDragDrop32 [OLE32.65]
 */
HRESULT WINAPI DoDragDrop (
  IDataObject *pDataObject,  /* ptr to the data obj           */
  IDropSource* pDropSource,  /* ptr to the source obj         */
  DWORD       dwOKEffect,    /* effects allowed by the source */
  DWORD       *pdwEffect)    /* ptr to effects of the source  */
{
  TrackerWindowInfo trackerInfo;
  HWND            hwndTrackWindow;
  MSG             msg;

  TRACE(ole,"(DataObject %p, DropSource %p)\n", pDataObject, pDropSource);

  /*
   * Setup the drag n drop tracking window.
   */
  trackerInfo.dataObject        = pDataObject;
  trackerInfo.dropSource        = pDropSource;
  trackerInfo.dwOKEffect        = dwOKEffect;
  trackerInfo.pdwEffect         = pdwEffect;
  trackerInfo.trackingDone      = FALSE;
  trackerInfo.escPressed        = FALSE;
  trackerInfo.curDragTargetHWND = 0;
  trackerInfo.curDragTarget     = 0;

  hwndTrackWindow = CreateWindowA(OLEDD_DRAGTRACKERCLASS,
                                    "TrackerWindow",
                                    WS_POPUP,
                                    CW_USEDEFAULT, CW_USEDEFAULT,
                                    CW_USEDEFAULT, CW_USEDEFAULT,
                                    0,
                                    0,
                                    0,
                                    (LPVOID)&trackerInfo);

  if (hwndTrackWindow!=0)
  {
    /*
     * Capture the mouse input
     */
    SetCapture(hwndTrackWindow);

    /*
     * Pump messages. All mouse input should go the the capture window.
     */
    while (!trackerInfo.trackingDone && GetMessageA(&msg, 0, 0, 0) )
    {
      if ( (msg.message >= WM_KEYFIRST) && 
           (msg.message <= WM_KEYFIRST) )
      {
        /*
         * When keyboard messages are sent to windows on this thread, we
         * want to ignore notify the drop source that the state changed.
         * in the case of the Escape key, we also notify the drop source
         * we give it a special meaning.
         */
        if ( (msg.message==WM_KEYDOWN) &&
             (msg.wParam==VK_ESCAPE) )
        {
          trackerInfo.escPressed = TRUE;
        }

        /*
         * Notify the drop source.
         */       
        OLEDD_TrackStateChange(&trackerInfo,
                               msg.pt,
                               OLEDD_GetButtonState());
      }
      else
      {
        /*
         * Dispatch the messages only when it's not a keyboard message.
         */
        DispatchMessageA(&msg);
      }
    }

    /*
     * Destroy the temporary window.
     */
    DestroyWindow(hwndTrackWindow);

    return trackerInfo.returnValue;
  }

  return E_FAIL;
}

/***********************************************************************
 * OleQueryLinkFromData32 [OLE32.118]
 */
HRESULT WINAPI OleQueryLinkFromData32(
  IDataObject* pSrcDataObject)
{
  FIXME(ole,"(%p),stub!\n", pSrcDataObject);
  return S_OK;
}

/***********************************************************************
 * OleRegGetMiscStatus32 [OLE32.121]
 */
HRESULT WINAPI OleRegGetMiscStatus32(
  REFCLSID clsid,
  DWORD    dwAspect,
  DWORD*   pdwStatus)
{
  FIXME(ole,"(),stub!\n");
  return REGDB_E_CLASSNOTREG;
}

/***********************************************************************
 * OleGetClipboard32 [OLE32.105]
 */
HRESULT WINAPI OleGetClipboard32(
  IDataObject** ppDataObj)
{
  FIXME(ole,"(%p),stub!\n", ppDataObj);

  if (ppDataObj)
    *ppDataObj=0;

  return E_FAIL;
}

/***********************************************************************
 * OleCreateMenuDescriptor [OLE32.97]
 */
HOLEMENU WINAPI OleCreateMenuDescriptor(
  HMENU                hmenuCombined,
  LPOLEMENUGROUPWIDTHS lpMenuWidths)
{
  FIXME(ole,"(%x,%p),stub!\n", hmenuCombined, lpMenuWidths);

  return NULL;
}

/***********************************************************************
 * OleDestroyMenuDescriptor [OLE32.99]
 */
void WINAPI OleDestroyMenuDescriptor(
  HOLEMENU hmenuDescriptor)
{
  FIXME(ole,"(%x),stub!\n", (unsigned int)hmenuDescriptor);
}

/***********************************************************************
 * OleSetMenuDescriptor [OLE32.129]
 */
HRESULT WINAPI OleSetMenuDescriptor(
  HOLEMENU               hmenuDescriptor,
  HWND                   hwndFrame,
  HWND                   hwndActiveObject,
  LPOLEINPLACEFRAME        lpFrame,
  LPOLEINPLACEACTIVEOBJECT lpActiveObject)
{
  FIXME(ole,"(%x, %x, %x, %p, %p),stub!\n", 
        (unsigned int)hmenuDescriptor,
        hwndFrame,
        hwndActiveObject,
        lpFrame,
        lpActiveObject);

  return E_FAIL;
}

/***********************************************************************
 * ReleaseStgMedium [OLE32.140]
 */
void WINAPI ReleaseStgMedium(
  STGMEDIUM* pmedium)
{
  switch (pmedium->tymed)
  {
    case TYMED_HGLOBAL:
    {
      if ( (pmedium->pUnkForRelease==0) && 
           (pmedium->u.hGlobal!=0) )
        GlobalFree(pmedium->u.hGlobal);

      pmedium->u.hGlobal = 0;
      break;
    }
    case TYMED_FILE:
    {
      if (pmedium->u.lpszFileName!=0)
      {
        if (pmedium->pUnkForRelease==0)
        {
          DeleteFileW(pmedium->u.lpszFileName);
        }
        
        CoTaskMemFree(pmedium->u.lpszFileName);
      }

      pmedium->u.lpszFileName = 0;
      break;
    }
    case TYMED_ISTREAM:
    {
      if (pmedium->u.pstm!=0)
      {
        IStream_Release(pmedium->u.pstm);
      }

      pmedium->u.pstm = 0;
      break;
    }
    case TYMED_ISTORAGE:
    {
      if (pmedium->u.pstg!=0)
      {
        IStorage_Release(pmedium->u.pstg);
      }

      pmedium->u.pstg = 0;
      break;
    }
    case TYMED_GDI:
    {
      if ( (pmedium->pUnkForRelease==0) && 
           (pmedium->u.hGlobal!=0) )
        DeleteObject(pmedium->u.hGlobal);

      pmedium->u.hGlobal = 0;
      break;
    }
    case TYMED_MFPICT:
    {
      if ( (pmedium->pUnkForRelease==0) && 
           (pmedium->u.hMetaFilePict!=0) )
      {
        DeleteMetaFile(pmedium->u.hMetaFilePict);
        GlobalFree(pmedium->u.hMetaFilePict);
      }

      pmedium->u.hMetaFilePict = 0;
      break;
    }
    case TYMED_ENHMF:
    {
      if ( (pmedium->pUnkForRelease==0) && 
           (pmedium->u.hEnhMetaFile!=0) )
      {
        DeleteEnhMetaFile(pmedium->u.hEnhMetaFile);
      }

      pmedium->u.hEnhMetaFile = 0;
      break;
    }
    case TYMED_NULL:
    default:
      break;
  }

  /*
   * After cleaning up, the unknown is released
   */
  if (pmedium->pUnkForRelease!=0)
  {
    IUnknown_Release(pmedium->pUnkForRelease);
    pmedium->pUnkForRelease = 0;
  }
}

/***
 * OLEDD_Initialize()
 *
 * Initializes the OLE drag and drop data structures.
 */
static void OLEDD_Initialize()
{
    WNDCLASSA wndClass;

    ZeroMemory (&wndClass, sizeof(WNDCLASSA));
    wndClass.style         = CS_GLOBALCLASS;
    wndClass.lpfnWndProc   = (WNDPROC)OLEDD_DragTrackerWindowProc;
    wndClass.cbClsExtra    = 0;
    wndClass.cbWndExtra    = sizeof(TrackerWindowInfo*);
    wndClass.hCursor       = 0;
    wndClass.hbrBackground = 0;
    wndClass.lpszClassName = OLEDD_DRAGTRACKERCLASS;
 
    RegisterClassA (&wndClass);
}

/***
 * OLEDD_UnInitialize()
 *
 * Releases the OLE drag and drop data structures.
 */
static void OLEDD_UnInitialize()
{
  /*
   * Simply empty the list.
   */
  while (targetListHead!=NULL)
  {
    RevokeDragDrop(targetListHead->hwndTarget);
  }
}

/***
 * OLEDD_InsertDropTarget()
 *
 * Insert the target node in the tree.
 */
static void OLEDD_InsertDropTarget(DropTargetNode* nodeToAdd)
{
  DropTargetNode*  curNode;
  DropTargetNode** parentNodeLink;

  /*
   * Iterate the tree to find the insertion point.
   */
  curNode        = targetListHead;
  parentNodeLink = &targetListHead;

  while (curNode!=NULL)
  {
    if (nodeToAdd->hwndTarget<curNode->hwndTarget)
    {
      /*
       * If the node we want to add has a smaller HWND, go left
       */
      parentNodeLink = &curNode->prevDropTarget;
      curNode        =  curNode->prevDropTarget;
    }
    else if (nodeToAdd->hwndTarget>curNode->hwndTarget)
    {
      /*
       * If the node we want to add has a larger HWND, go right
       */
      parentNodeLink = &curNode->nextDropTarget;
      curNode        =  curNode->nextDropTarget;
    }
    else
    {
      /*
       * The item was found in the list. It shouldn't have been there
       */
      assert(FALSE);
      return;
    }
  }

  /*
   * If we get here, we have found a spot for our item. The parentNodeLink
   * pointer points to the pointer that we have to modify. 
   * The curNode should be NULL. We just have to establish the link and Voila!
   */
  assert(curNode==NULL);
  assert(parentNodeLink!=NULL);
  assert(*parentNodeLink==NULL);

  *parentNodeLink=nodeToAdd;
}

/***
 * OLEDD_ExtractDropTarget()
 *
 * Removes the target node from the tree.
 */
static DropTargetNode* OLEDD_ExtractDropTarget(HWND hwndOfTarget)
{
  DropTargetNode*  curNode;
  DropTargetNode** parentNodeLink;

  /*
   * Iterate the tree to find the insertion point.
   */
  curNode        = targetListHead;
  parentNodeLink = &targetListHead;

  while (curNode!=NULL)
  {
    if (hwndOfTarget<curNode->hwndTarget)
    {
      /*
       * If the node we want to add has a smaller HWND, go left
       */
      parentNodeLink = &curNode->prevDropTarget;
      curNode        =  curNode->prevDropTarget;
    }
    else if (hwndOfTarget>curNode->hwndTarget)
    {
      /*
       * If the node we want to add has a larger HWND, go right
       */
      parentNodeLink = &curNode->nextDropTarget;
      curNode        =  curNode->nextDropTarget;
    }
    else
    {
      /*
       * The item was found in the list. Detach it from it's parent and 
       * re-insert it's kids in the tree.
       */
      assert(parentNodeLink!=NULL);
      assert(*parentNodeLink==curNode);

      /*
       * We arbitrately re-attach the left sub-tree to the parent.
       */
      *parentNodeLink = curNode->prevDropTarget;

      /*
       * And we re-insert the right subtree
       */
      if (curNode->nextDropTarget!=NULL)
      {
        OLEDD_InsertDropTarget(curNode->nextDropTarget);
      }

      /*
       * The node we found is still a valid node once we complete
       * the unlinking of the kids.
       */
      curNode->nextDropTarget=NULL;
      curNode->prevDropTarget=NULL;

      return curNode;
    }
  }

  /*
   * If we get here, the node is not in the tree
   */
  return NULL;
}

/***
 * OLEDD_FindDropTarget()
 *
 * Finds information about the drop target.
 */
static DropTargetNode* OLEDD_FindDropTarget(HWND hwndOfTarget)
{
  DropTargetNode*  curNode;

  /*
   * Iterate the tree to find the HWND value.
   */
  curNode        = targetListHead;

  while (curNode!=NULL)
  {
    if (hwndOfTarget<curNode->hwndTarget)
    {
      /*
       * If the node we want to add has a smaller HWND, go left
       */
      curNode =  curNode->prevDropTarget;
    }
    else if (hwndOfTarget>curNode->hwndTarget)
    {
      /*
       * If the node we want to add has a larger HWND, go right
       */
      curNode =  curNode->nextDropTarget;
    }
    else
    {
      /*
       * The item was found in the list.
       */
      return curNode;
    }
  }

  /*
   * If we get here, the item is not in the list
   */
  return NULL;
}

/***
 * OLEDD_DragTrackerWindowProc()
 *
 * This method is the WindowProcedure of the drag n drop tracking
 * window. During a drag n Drop operation, an invisible window is created
 * to receive the user input and act upon it. This procedure is in charge
 * of this behavior.
 */
static LRESULT WINAPI OLEDD_DragTrackerWindowProc(
                         HWND   hwnd, 
                         UINT   uMsg,
                         WPARAM wParam, 
                         LPARAM   lParam)
{
  switch (uMsg)
  {
    case WM_CREATE:
    {
      LPCREATESTRUCTA createStruct = (LPCREATESTRUCTA)lParam;

      SetWindowLongA(hwnd, 0, (LONG)createStruct->lpCreateParams); 

      
      break;
    }
    case WM_MOUSEMOVE:
    {
      TrackerWindowInfo* trackerInfo = (TrackerWindowInfo*)GetWindowLongA(hwnd, 0);
      POINT            mousePos;

      /*
       * Get the current mouse position in screen coordinates.
       */
      mousePos.x = LOWORD(lParam);
      mousePos.y = HIWORD(lParam);
      ClientToScreen(hwnd, &mousePos);

      /*
       * Track the movement of the mouse.
       */
      OLEDD_TrackMouseMove(trackerInfo, mousePos, wParam);

      break;
    }
    case WM_LBUTTONUP:
    case WM_MBUTTONUP:
    case WM_RBUTTONUP:
    case WM_LBUTTONDOWN:
    case WM_MBUTTONDOWN:
    case WM_RBUTTONDOWN:
    {
      TrackerWindowInfo* trackerInfo = (TrackerWindowInfo*)GetWindowLongA(hwnd, 0);
      POINT            mousePos;

      /*
       * Get the current mouse position in screen coordinates.
       */
      mousePos.x = LOWORD(lParam);
      mousePos.y = HIWORD(lParam);
      ClientToScreen(hwnd, &mousePos);

      /*
       * Notify everyone that the button state changed
       * TODO: Check if the "escape" key was pressed.
       */
      OLEDD_TrackStateChange(trackerInfo, mousePos, wParam);

      break;
    }
  }

  /*
   * This is a window proc after all. Let's call the default.
   */
  return DefWindowProcA (hwnd, uMsg, wParam, lParam);
}

/***
 * OLEDD_TrackMouseMove()
 *
 * This method is invoked while a drag and drop operation is in effect.
 * it will generate the appropriate callbacks in the drop source
 * and drop target. It will also provide the expected feedback to
 * the user.
 *
 * params:
 *    trackerInfo - Pointer to the structure identifying the
 *                  drag & drop operation that is currently
 *                  active.
 *    mousePos    - Current position of the mouse in screen
 *                  coordinates.
 *    keyState    - Contains the state of the shift keys and the
 *                  mouse buttons (MK_LBUTTON and the like)
 */
static void OLEDD_TrackMouseMove(
  TrackerWindowInfo* trackerInfo,
  POINT            mousePos,
  DWORD              keyState)
{
  HWND   hwndNewTarget = 0;
  HRESULT  hr = S_OK;

  /*
   * Get the handle of the window under the mouse
   */
  hwndNewTarget = WindowFromPoint(mousePos);

  /*
   * If we are hovering over the same target as before, send the
   * DragOver notification
   */
  if ( (trackerInfo->curDragTarget != 0) && 
       (trackerInfo->curDragTargetHWND==hwndNewTarget) )
  {
    POINTL  mousePosParam;
    
    /*
     * The documentation tells me that the coordinate should be in the target
     * window's coordinate space. However, the tests I made tell me the
     * coordinates should be in screen coordinates.
     */
    mousePosParam.x = mousePos.x;
    mousePosParam.y = mousePos.y;
    
    IDropTarget_DragOver(trackerInfo->curDragTarget,
                         keyState,
                         mousePosParam,
                         trackerInfo->pdwEffect);
  }
  else
{
    DropTargetNode* newDropTargetNode = 0;
    
    /*
     * If we changed window, we have to notify our old target and check for
     * the new one.
     */
    if (trackerInfo->curDragTarget!=0)
    {
      IDropTarget_DragLeave(trackerInfo->curDragTarget);
    }
    
    /*
     * Make sure we're hovering over a window.
     */
    if (hwndNewTarget!=0)
    {
      /*
       * Find-out if there is a drag target under the mouse
       */
      newDropTargetNode = OLEDD_FindDropTarget(hwndNewTarget);
      
      trackerInfo->curDragTargetHWND = hwndNewTarget;
      trackerInfo->curDragTarget     = newDropTargetNode ? newDropTargetNode->dropTarget : 0;
      
      /*
       * If there is, notify it that we just dragged-in
       */
      if (trackerInfo->curDragTarget!=0)
      {
        POINTL  mousePosParam;
        
        /*
         * The documentation tells me that the coordinate should be in the target
         * window's coordinate space. However, the tests I made tell me the
         * coordinates should be in screen coordinates.
         */
        mousePosParam.x = mousePos.x;
        mousePosParam.y = mousePos.y;
        
        IDropTarget_DragEnter(trackerInfo->curDragTarget,
                              trackerInfo->dataObject,
                              keyState,
                              mousePosParam,
                              trackerInfo->pdwEffect);
      }
    }
    else
    {
      /*
       * The mouse is not over a window so we don't track anything.
       */
      trackerInfo->curDragTargetHWND = 0;
      trackerInfo->curDragTarget     = 0;
    }
  }

  /*
   * Now that we have done that, we have to tell the source to give 
   * us feedback on the work being done by the target.  If we don't 
   * have a target, simulate no effect.
   */
  if (trackerInfo->curDragTarget==0)
  {
    *trackerInfo->pdwEffect = DROPEFFECT_NONE;
  }

  hr = IDropSource_GiveFeedback(trackerInfo->dropSource,
                                *trackerInfo->pdwEffect);

  /*
   * When we ask for feedback from the drop source, sometimes it will
   * do all the necessary work and sometimes it will not handle it
   * when that's the case, we must display the standard drag and drop
   * cursors.
   */
  if (hr==DRAGDROP_S_USEDEFAULTCURSORS)
  {
    if ( (*trackerInfo->pdwEffect & DROPEFFECT_MOVE) ||
         (*trackerInfo->pdwEffect & DROPEFFECT_COPY) ||
         (*trackerInfo->pdwEffect & DROPEFFECT_LINK) )
    {
      SetCursor(LoadCursorA(0, IDC_SIZEALLA));
    }
    else
    {
      SetCursor(LoadCursorA(0, IDC_NOA));
    }
  }  
}

/***
 * OLEDD_TrackStateChange()
 *
 * This method is invoked while a drag and drop operation is in effect.
 * It is used to notify the drop target/drop source callbacks when
 * the state of the keyboard or mouse button change.
 *
 * params:
 *    trackerInfo - Pointer to the structure identifying the
 *                  drag & drop operation that is currently
 *                  active.
 *    mousePos    - Current position of the mouse in screen
 *                  coordinates.
 *    keyState    - Contains the state of the shift keys and the
 *                  mouse buttons (MK_LBUTTON and the like)
 */
static void OLEDD_TrackStateChange(
  TrackerWindowInfo* trackerInfo,
  POINT            mousePos,
  DWORD              keyState)
{
  /*
   * Ask the drop source what to do with the operation.
   */
  trackerInfo->returnValue = IDropSource_QueryContinueDrag(
                               trackerInfo->dropSource,
                               trackerInfo->escPressed, 
                               keyState);
  
  /*
   * All the return valued will stop the operation except the S_OK
   * return value.
   */
  if (trackerInfo->returnValue!=S_OK)
  {
    /*
     * Make sure the message loop in DoDragDrop stops
     */
    trackerInfo->trackingDone = TRUE;

    /*
     * Release the mouse in case the drop target decides to show a popup 
     * or a menu or something.
     */
    ReleaseCapture();
    
    /*
     * If we end-up over a target, drop the object in the target or 
     * inform the target that the operation was cancelled.
     */
    if (trackerInfo->curDragTarget!=0)
    {
      switch (trackerInfo->returnValue)
      {
        /*
         * If the source wants us to complete the operation, we tell 
         * the drop target that we just dropped the object in it.
         */
        case DRAGDROP_S_DROP:
        {
          POINTL  mousePosParam;
        
          /*
           * The documentation tells me that the coordinate should be 
           * in the target window's coordinate space. However, the tests
           * I made tell me the coordinates should be in screen coordinates.
           */
          mousePosParam.x = mousePos.x;
          mousePosParam.y = mousePos.y;
          
          IDropTarget_Drop(trackerInfo->curDragTarget,
                           trackerInfo->dataObject,
                           keyState,
                           mousePosParam,
                           trackerInfo->pdwEffect);
          break;
        }
        /*
         * If the source told us that we should cancel, fool the drop 
         * target by telling it that the mouse left it's window.
         */
        case DRAGDROP_S_CANCEL:
          IDropTarget_DragLeave(trackerInfo->curDragTarget);
          break;
      }
    }
  }
}

/***
 * OLEDD_GetButtonState()
 *
 * This method will use the current state of the keyboard to build
 * a button state mask equivalent to the one passed in the
 * WM_MOUSEMOVE wParam.
 */
static DWORD OLEDD_GetButtonState()
{
  BYTE  keyboardState[256];
  DWORD keyMask = 0;

  GetKeyboardState(keyboardState);

  if ( (keyboardState[VK_SHIFT] & 0x80) !=0)
    keyMask |= MK_SHIFT;

  if ( (keyboardState[VK_CONTROL] & 0x80) !=0)
    keyMask |= MK_CONTROL;

  if ( (keyboardState[VK_LBUTTON] & 0x80) !=0)
    keyMask |= MK_LBUTTON;

  if ( (keyboardState[VK_RBUTTON] & 0x80) !=0)
    keyMask |= MK_RBUTTON;

  if ( (keyboardState[VK_MBUTTON] & 0x80) !=0)
    keyMask |= MK_MBUTTON;

  return keyMask;
}