SHCreateDataObject/IDataObject Exhibits Strange Behavior During CDefView::OnBeginDrag - c++

Question

In my IShellFolder::GetUIObjectOf with riid == IID_IDataObject, I invoke SHCreateDataObject and supply a pointer to my newly created DataObject as such:
DataObject *pDataObject = new DataObject (this->pidl_absolute, uCount, aPidl);
hr = SHCreateDataObject (this->pidl_absolute, uCount, aPidl, pDataObject, riid, ppvReturn);
DataObject::DataObject (PCIDLIST_ABSOLUTE pidlFolder, UINT cidl, LPCITEMIDLIST aPidl[]) : reference_count (0)
{
++DLL_reference_count;
return; // DEFECT: For testing.
In my DataObject::DataObject constructor, I take care not to insert any FORMATETC or STGMEDIUM. Then I start a drag-and-drop operation from an Explorer CDefView window, causing the following call sequence. The drag-loop icon is mostly the "drop-effect-none" circle/slash with small [+] for some windows. For some strange reason, my DataObject::QueryGetData and DataObject::SetData are being invoked with weird arguments (with zero values that should not be zero?). Perhaps I do not understand. How could this be happening when it occurs before I have done anything that could trigger it (I think)? I wrote code to add CFSTR_FILEDESCRIPTORW and CFSTR_FILECONTENTS to my DataObject::DataObject constructor, which did not work, which lead me to this problem.
EDIT:
After a more thorough investigation, I can conclude that my problem is not SHCreateDataObject. I only invoke this function in one place in my code:
hr = SHCreateDataObject (this->pidl_absolute, uCount, aPidl, pDataObject, riid, ppvReturn);
After invocation, there is only one format present in pDataObject: CF_SHELLIDLIST. As #SimonMourier noted, there probably should be more. I manually insert the ones I need, which, ~technically~, I should be able to do, since my NSE is virtual. I can clearly see that during the DoDragDrop() loop, Explorer is invoking my SetData with CF_HDROP with pmedium->hGlobal nullified.
The circle/slash problem no longer exists, as it was due to a bogust ReleaseStgMedium, but the nullifed hGlobal is still present.
DataObject.cpp(584) : atlTraceGeneral - DataObject::SetData : Format = Shell IDList Array // tymed == TYMED_HGLOBAL for both
DataObject.cpp(584) : atlTraceGeneral - DataObject::SetData : Format = UsingDefaultDragImage // tymed == TYMED_HGLOBAL for both
DataObject.cpp(584) : atlTraceGeneral - DataObject::SetData : Format = DragImageBits // tymed == TYMED_HGLOBAL for both
DataObject.cpp(584) : atlTraceGeneral - DataObject::SetData : Format = DragContext // tymed == TYMED_ISTREAM for both
DataObject.cpp(584) : atlTraceGeneral - DataObject::SetData : Format = DragSourceHelperFlags // tymed == TYMED_HGLOBAL for both
DataObject.cpp(584) : atlTraceGeneral - DataObject::SetData : Format = InShellDragLoop // tymed == TYMED_HGLOBAL for both
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = DragContext// tymed == TYMED_ISTREAM
DataObject.cpp(550) : atlTraceGeneral - DataObject::QueryGetData : Format = CF_HDROP // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = FileName // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = Net Resource // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = FileContents // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = FileGroupDescriptor // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = FileNameMapW // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = FileNameMapW // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC (again)
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = Shell IDList Array // tymed == TYMED_HGLOBAL, I return S_OK
DataObject.cpp(584) : atlTraceGeneral - DataObject::SetData : Format = Shell IDList Array // tymed == TYMED_HGLOBAL for both, all other fields of *pmedium are 0!
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = Shell Object Offsets // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = PrinterFriendlyName // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = Shell IDLData Private // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = HTML Format // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = FileNameW // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = FileGroupDescriptorW // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = Preferred DropEffect // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = Performed DropEffect // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = Paste Succeeded // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = UniformResourceLocator // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = InShellDragLoop // tymed == TYMED_HGLOBAL, I return S_OK
DataObject.cpp(584) : atlTraceGeneral - DataObject::SetData : Format = InShellDragLoop pformatetc->tymed == TYMED_HGLOBAL, *pmedium is ~ALL~ ZERO'S!!!, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = DragContext // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = TargetCLSID // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = Embedded Object // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = Object Descriptor // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = NotRecyclable // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = Logical Performed DropEffect // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = Briefcase File Object // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = DropEffectFolderList // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = Autoplay Enumerated IDList Array // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = UniformResourceLocator // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = UniformResourceLocatorW // cfformat == 0, tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(552) : atlTraceGeneral - DataObject::QueryGetData : Format = AsyncFlag // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
DataObject.cpp(608) : atlTraceGeneral - DataObject::EnumFormatEtc
DataObject.cpp(550) : atlTraceGeneral - DataObject::QueryGetData : Format = CF_HDROP // tymed == TYMED_HGLOBAL, I return DV_E_FORMATETC
The thread 0xfc8 has exited with code 0 (0x0).
The thread 0xfa0 has exited with code 0 (0x0).
Exception thrown at 0x000007FEFD11B87D (KernelBase.dll) in explorer.exe: 0x80010108: The object invoked has disconnected from its clients.
DataObject.cpp(461) : atlTraceGeneral - DataObject::GetData : Format = Shell IDList Array pformatetc->tymed == TYMED_HGLOBAL, *pmedium is ~ALL~ ZERO'S!!!, not sure what to do so I lie and return S_OK without doing anything.
DataObject.cpp(461) : atlTraceGeneral - DataObject::GetData : Format = IsShowingText
DataObject.cpp(461) : atlTraceGeneral - DataObject::GetData : Format = UsingDefaultDragImage
DataObject.cpp(461) : atlTraceGeneral - DataObject::GetData : Format = DragSourceHelperFlags
DataObject.cpp(461) : atlTraceGeneral - DataObject::GetData : Format = IsComputingImage
DataObject.cpp(461) : atlTraceGeneral - DataObject::GetData : Format = DisableDragText
DataObject.cpp(461) : atlTraceGeneral - DataObject::GetData : Format = IsComputingImage
DataObject.cpp(461) : atlTraceGeneral - DataObject::GetData : Format = DropDescription
DataObject.cpp(461) : atlTraceGeneral - DataObject::GetData : Format = DragContext
DataObject.cpp(461) : atlTraceGeneral - DataObject::GetData : Format = IsShowingLayered
DataObject.cpp(461) : atlTraceGeneral - DataObject::GetData : Format = UntrustedDragDrop
DataObject.cpp(584) : atlTraceGeneral - DataObject::SetData : Format = DropDescription
DataObject.cpp(584) : atlTraceGeneral - DataObject::SetData : Format = DisableDragText
DataObject.cpp(461) : atlTraceGeneral - DataObject::GetData : Format = DisableDragText
DataObject.cpp(461) : atlTraceGeneral - DataObject::GetData : Format = IsComputingImage
DataObject.cpp(461) : atlTraceGeneral - DataObject::GetData : Format = DropDescription
DataObject.cpp(461) : atlTraceGeneral - DataObject::GetData : Format = IsShowingLayered
DataObject.cpp(584) : atlTraceGeneral - DataObject::SetData : Format = IsShowingLayered
DataObject.cpp(584) : atlTraceGeneral - DataObject::SetData : Format = IsShowingText
The following code shows that SHCreateDataObject injects only one FORMATETC for a filename. My guess is that format is CF_SHELLIDLIST.
#include <ole2.h>
#include <atlbase.h>
#include <Shobjidl.h>
#include <ShlObj.h>
#include <iostream>
using namespace std;
int main()
{
OleInitialize(NULL); // clipboard needs this
CComPtr<IShellItem> item;
SHCreateItemFromParsingName(L"C:\\Windows\\write.exe", NULL, IID_PPV_ARGS(&item));
CComHeapPtr<ITEMID_CHILD> child;
CComHeapPtr<ITEMIDLIST_ABSOLUTE> pidl;
CComQIPtr<IParentAndItem>(item)->GetParentAndItem(&pidl, NULL, &child);
CComPtr<IDataObject> dao;
LPCITEMIDLIST list[1];
list[0] = child;
SHCreateDataObject(pidl, 1, list, NULL, IID_PPV_ARGS(&dao));
OleSetClipboard(dao);
IEnumFORMATETC* pEnumerator = 0;
dao->EnumFormatEtc(DATADIR_GET, &pEnumerator);
unsigned int i = 0;
FORMATETC formatec;
while (S_OK == pEnumerator->Next(1, &formatec, NULL))
++i;
cout << "The number of formats created is: " << i << endl; // ... This printed "1".
OleUninitialize();
return 0;
}