The size of the ATL control does not display correctly in a control container

CAUSE

By default, ATL control projects have two entries in the Property Map that allow the control's display size to be persisted. These entries are:

• PROP_DATA_ENTRY("_cx", m_sizeExtent.cx, VT_UI4)
• PROP_DATA_ENTRY("_cy", m_sizeExtent.cy, VT_UI4)

If the control supports IPersistPropertyBagWhen, AtlIPersistPropertyBag_Load() is called when the control's properties are read in. In this function, IPropertyBag::Read() is called, but the VARIANT passed in is not initialized. Because the "vt" member of the VARIANT is set to VT_EMPTY instead of VT_UI4, in the case of "_cx" and "_cy" they are read in as some other type, which results in incorrect values.

ATLINLINE ATLAPI AtlIPersistPropertyBag_Load(LPPROPERTYBAG pPropBag,

   LPERRORLOG pErrorLog, ATL_PROPMAP_ENTRY* pMap, void* pThis,
   IUnknown* pUnk)

{

   USES_CONVERSION;
   CComPtr<IDispatch> pDispatch;
   const IID* piidOld = NULL;
   for (int i = 0; pMap[i].pclsidPropPage != NULL; i++)
   {
      if (pMap[i].szDesc == NULL)
         continue;


      CComVariant var;
      var.vt = pMap[i].vt;     // This line needs to be added.
      ....
   }

}