windows 8 IShellIconOverlayIdentifier shell extension not working properly - c++

Question

I have an application where i want to have icon overlays for specific files and folders.
For this purpose i've written a shell extension that implements the IShellIconOverlayIdentifier interface. Its written in c++ / Qt (activeqt) as a dll that connects to the application in question using tcp to query the application to decide wether to show the icon overlay or not. Its buildt much the same way this is.
It works fine in XP/Vista/7 but it wont work in windows 8.
In windows 8 the dll is loaded. I can see it in process explorer and also as a part of debugging it also logs output to a file so i can see whats happening and infer whats not.
Using ShellExView i can also see thats its registered, not disabled and in general everything looks ok.
The class declaration looks more or less like this:
class Q_DECL_EXPORT OverlayClass :
public QAxAggregated,
public IShellIconOverlayIdentifier{
public:
// Implements IUnknown
QAXAGG_IUNKNOWN;
JShellOverlayWorking();
// Implements IShellIconOverlayIdentifier
STDMETHOD(GetOverlayInfo)(LPWSTR pwszIconFile, int cchMax, int *pIndex, DWORD* pdwFlags);
STDMETHOD(GetPriority)(int* pPriority);
STDMETHOD(IsMemberOf)(LPCWSTR pwszPath, DWORD dwAttrib);
//pure virtual from QAxAggregated
long queryInterface(const QUuid &iid, void**iface);
};
Whats happens on XP/Vista/7 :
that explorer on load first call queryInterface() and gets an S_OK if iid == IID_IShellIconOverlayIdentifier and E_NOINTERFACE for all other iid's
and then it goes on to call GetOverlayInfo() to initialize stuff. Get the icon file path etc.
And then as the shell needs to it calls IsMemberOf() to see if it should display the icon for a file or folder.
What happens on windows 8 :
that explorer on load calls queryInterface() and gets an S_OK when iid == IID_IShellIconOverlayIdentifier and E_NOINTERFACE for all other iid's
And nothing else. queryInterface() is getting called, but after that nothing happens. I can see my application connecting successfully to the tcp socket created by the shell extension and IPC is working( i can send data back and forth between the application and the dll, but again. Nothing else happens. Explorer is not using the implemented interface.
The dll is registered using:
regsvr32.exe shellext.dll
and the registry key below is also added
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ShellIconOverlayIdentifiers\Shellextname ( value = CSLID )
for testing on windows 8 i've also added the following key to
HKCU\Software\Microsoft\Windows\CurrentVersion\Shell Extensions\Approved
with my shell extensions CSLID as the name and data = Shellextname ( as above in the previous key) though this doesn't seem to matter on XP/Vista/7 so i'm guessing its inconsequential here as well.
Again, this works on every windows( >= xp) except windows 8.
What am i missing? Where do i go from here to find out?

Answer 1

It seems the problem was that the registry key
HKEY_CLASSES_ROOT\CLSID\{myguid}\InprocServer32
ThreadingModel = Apartment
as specified here was not set by regsvr32.exe. I guess previous windows versions ignored this if it wasn't set, but windows 8 required it. Setting it manually worked.