C++ show an icon оverlay over all empty folders

Question

I am searching for the C++ solution to show icon overlay over the folder. but I have noticed that it's really bad idea to code overlays in .NET\Java +Shell because interpreter is called all the time you are using explorer.

So I have example how to do add icon over files which contains some text: http://www.codeproject.com/KB/shell/overlayicon.aspx

And I need to mark with my icon all empty folders. How can i do that?

Will appreciate any help.

Answer 1

You need to create a COM object that implements IShellIconOverlayIdentifier like that codeproject article.

Your IsMemberOf method would look something like this:

STDMETHODIMP YourClassThatImplementsIShellIconOverlayIdentifier::IsMemberOf(PCWSTR pwszPath,DWORD Attr)
{
    if (!(Attr&FILE_ATTRIBUTE_DIRECTORY)) return S_FALSE; // Not a folder

    UINT count = 0;
    WIN32_FIND_DATAW wfd;
    LPWSTR bufSpec = (LPWSTR) LocalAlloc(LPTR,(lstrlenW(pwszPath)+2+1)*sizeof(WCHAR));
    if (bufSpec)
    {
        lstrcpyW(bufSpec,pwszPath);
        PathAddBackslashW(bufSpec);
        lstrcatW(bufSpec,L"*");
        HANDLE hFind = FindFirstFileW(bufSpec,&wfd);
        if (INVALID_HANDLE_VALUE!=hFind) do
        {
            ++count;
        } while( count<= 2 && FindNextFileW(hFind,&wfd) );
        FindClose(hFind);
        LocalFree(bufSpec);
    }

    return count==2 ? S_OK : S_FALSE;
}

(A empty folder contains two special entries, "." and "..")