Hello Gurus,

I am writing a ATL COM DLL which in turn uses an another 3rd party normal
dll.

In my FinalConstruct i initialize the 3rd party dll toolkit and also
Register the Interface in the GIT.
While using the third party dll i also provide it with my own callback
function “DisplayPercentage”.

Now when the VB call a Write() function on my Interface I in turn call the
functions of the 3rd party dll which in turn call my call back function
say “DisplayPercentage” which is a global function.

Now in this DisplayPercentage funtion I need to fire events to the VB. I am
doing a work around. I call function FireEvents on IMedia interface. Which
in turn call Fire_…().

The problem is that when in my Write() function on my Interface I create
another thread and call the third party function call. It calls my
DisplayPercentage function but when I try to get the Interface from the GIT
it fails with HRESULT stating catastrophic failure.

Here are some excerpts from the code at your disposal.

HRESULT CMedia::FinalConstruct()
{
 HRESULT hRes = E_FAIL;

 try
 {
  IMedia* pIMedia;

  hRes = this->QueryInterface(__uuidof
(IMedia),reinterpret_cast<void**>(&pIMedia));
  if(hRes != S_OK)
   return hRes;

  hRes = CoCreateInstance(CLSID_StdGlobalInterfaceTable,
                            NULL,
                            CLSCTX_INPROC_SERVER,
                            IID_IGlobalInterfaceTable,
                            (void **)&g_pGIT);
  if(g_pGIT == NULL)
   return E_FAIL;

  hRes = g_pGIT->RegisterInterfaceInGlobal(pIMedia, __uuidof
(IMedia),&g_dwCookie);

  if(g_dwCookie == 0 || hRes != S_OK)
   return E_FAIL;

  l_UserFunctions.PercFunction = DisplayPercentage;

  if( !InitialiseToolkit())
   return E_FAIL;

  if( !InitialiseGenerator())
   return E_FAIL;

  if(!InitialiseRecorder())
   return E_FAIL;

  //g_pMedia = this;
  hRes = S_OK;
 }
 catch(...)
 {
  hRes = E_FAIL;
 }

 return hRes;
}
...

.....
void __stdcall
DisplayPercentage (void *FreeUserPtr, TK_INT iPercentageValue, TK_INT
iPercentageType)
{
  IMedia* pIMedia;
 IGlobalInterfaceTable* pGIT = NULL;
 HRESULT hRes;

hRes = CoCreateInstance(CLSID_StdGlobalInterfaceTable,
                            NULL,
                            CLSCTX_INPROC_SERVER,
                            IID_IGlobalInterfaceTable,
                            (void **)&pGIT);
 if(pGIT == NULL)
  return;

 hRes = pGIT->GetInterfaceFromGlobal(g_dwCookie, __uuidof(IMedia),
reinterpret_cast<void**>(&pIMedia));

 if(pIMedia == NULL)
  return;

 switch (iPercentageType)
 {
 case UI_PERC_VOLUME_WRITE:
 case UI_PERC_VOLUME_ESTIMATE:
 case UI_PERC_VOLUME_VERIFY_IMAGE:
 case UI_PERC_VOLUME_MAKE_PHYSICAL:
 case UI_PERC_VOLUME_VERIFY_AFTER_WRITE:
 case UI_PERC_DISC_READ:
 case UI_PERC_CYCLIC_BUFFER:
  // Ignored here
  if (iPercentageValue == -1)
  {
  // display_somewhere ("");
  }
  else
  {
    if(g_iBufferProgress != iPercentageValue)
    {
     g_iBufferProgress = iPercentageValue;
     ATLTRACE("Buffer Progress Percent %d \n",
iPercentageValue);
     pIMedia->FireEvent(UI_PERC_CYCLIC_BUFFER,
g_iBufferProgress);
    }
  }
  break;
 case UI_PERC_DISC_FIXATION:
  if (iPercentageValue == -1)
  {
  // display_somewhere ("");
  }
  else
  {
    if(g_iTotalProgress != iPercentageValue)
    {
     g_iTotalProgress = iPercentageValue;
     ATLTRACE("Total Progress Percent %d \n",
iPercentageValue);
     pIMedia->FireEvent(UI_PERC_DISC_FIXATION,
g_iTotalProgress);
    }
  }
  break;
 case UI_PERC_DISC_ERASE:
 case UI_PERC_TRACK_WRITE:
 case UI_PERC_TRACK_ESTIMATE:
 case UI_PERC_TRACK_VERIFY_IMAGE:
 case UI_PERC_TRACK_MAKE_PHYSICAL:
 case UI_PERC_TRACK_VERIFY_AFTER_WRITE:
 case UI_PERC_TRACK_READ:
  if (iPercentageValue == -1)
  {
  // display_somewhere ("");
  }
  else
  {
    if(g_iTrackProgress != iPercentageValue)
    {
     g_iTrackProgress = iPercentageValue;
     ATLTRACE("Track Progress Percent %d \n",
iPercentageValue);
     pIMedia->FireEvent(UI_PERC_TRACK_READ,
g_iTrackProgress);
    }
  }
  break;
 default:
  break;
 }

 pIMedia->Release();
}

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