Re: MFC Icon Handler's IExtractIcon::GetIconLocation() never gets

"Jim Barry" wrote:


Well, ATL, for one thing.

Anyway, debugger aside, I've got a test app now and I can verify that I can
load the DLL and call into the IExtractIcon interface if I call
::CoInitialize(), CoCreateInstance(), do a QueryInterface(), and then call
the method off the pointer I get back:

    ::CoInitialize(NULL);

    IUnknown* pUnk(NULL);

    result = ::CoCreateInstance(kIHCLSID, NULL, CLSCTX_INPROC_SERVER,
                                IID_IUnknown,
                                reinterpret_cast<LPVOID*>(&pUnk));

    IPersistFile* pIPF(NULL);

    if (S_OK == pUnk->QueryInterface(IID_IPersistFile,
                                     reinterpret_cast<LPVOID*>(&pIPF)))
    {
        ASSERT(S_OK == pIPF->Load(_T("<path to my data file>"), 0));
    }

    IExtractIcon* pIEI(NULL);
    TCHAR path[MAX_PATH];

    if (S_OK == pUnk->QueryInterface(IID_IExtractIcon,
                               reinterpret_cast<LPVOID*>(&pIEI)))
    {
        int iIndex(0);
        UINT wFlags(0);

        if (S_OK == pIEI->GetIconLocation(0, path, MAX_PATH, &iIndex, &wFlags))
        {
            if (S_OK == pIEI->Extract(path, iIndex, &fHBigIcon, &fHSmallIcon,
                                      MAKELONG(32, 16)))
            {
                (void) fBigIcon.SetIcon(fHBigIcon);
                (void) fSmallIcon.SetIcon(fHSmallIcon);
            }
        }
    }

That all works fine. I can also do it using SHGetDesktopFolder() and the
various related calls:

    ::CoInitialize(NULL);

    if (FAILED(SHGetDesktopFolder(&deskFolder)))
        return TRUE;

    if (FAILED(deskFolder->ParseDisplayName(NULL, NULL,
     _T("g:\\development\\projects\\sample files\\files with
embedded previews\\biotite.cmdf"),
     NULL, &pidlLocal, NULL)))
    {
        deskFolder->Release();
        return TRUE;
    }

    pidlRelative = ILClone(ILFindLastID(pidlLocal));
  ILRemoveLastID(pidlLocal);

    if (FAILED(deskFolder->BindToObject(pidlLocal, NULL, IID_IShellFolder,
(void**)&appObject)))
    {
        deskFolder->Release();
        ILFree(pidlLocal);
        return TRUE;
    }

    ILFree(pidlLocal);

    hr = appObject->GetUIObjectOf(NULL, 1, (LPCITEMIDLIST*)&pidlRelative,
IID_IExtractIcon, NULL,
        (void**)&extractIcon);

But if I attach to an explorer window with the debugger, what happens is
that my IPersistFile::Load() method gets called, then I load the interface
for IExtractIcon, and, right after that, my IExtractIcon::Release() method
gets called (apparently from CoWaitForMultipleHandles()). So the shell gets
the IExtractIcon interface, and releases it without (apparently) calling
anything.