Function UnregisterShellExtThumbnailHandler

GTE_Win/Reg.cpp:269–303

FUNCTION: UnregisterShellExtThumbnailHandler PURPOSE: Unregister the thumbnail handler. PARAMETERS: pszFileType - The file type that the thumbnail handler is associated with. For example, '*' means all file types; '.txt' means all .txt files. The parameter must not be NULL. NOTE: The function removes the registry key HKCR\ \shellex\{e357fccd-a995-4576-b01f-234630154e96}.

//   HKCR\<File Type>\shellex\{e357fccd-a995-4576-b01f-234630154e96}.
//
HRESULT UnregisterShellExtThumbnailHandler(PCWSTR pszFileType)
{
    if (pszFileType == nullptr) {
        return E_INVALIDARG;
    }

    HRESULT hr;

    wchar_t szSubkey[MAX_PATH];

    // If pszFileType starts with '.', try to read the default value of the
    // HKCR\<File Type> key which contains the ProgID to which the file type
    // is linked.
    if (*pszFileType == L'.') {
        wchar_t szDefaultVal[260];
        hr = GetHKCRRegistryKeyAndValue(pszFileType, nullptr, szDefaultVal, sizeof(szDefaultVal));

        // If the key exists and its default value is not empty, use the
        // ProgID as the file type.
        if (SUCCEEDED(hr) && szDefaultVal[0] != L'\0') {
            pszFileType = szDefaultVal;
        }
    }

    // Remove the registry key:
    // HKCR\<File Type>\shellex\{e357fccd-a995-4576-b01f-234630154e96}
    hr = StringCchPrintf(szSubkey, ARRAYSIZE(szSubkey),
        L"%s\\shellex\\{e357fccd-a995-4576-b01f-234630154e96}", pszFileType);
    if (SUCCEEDED(hr)) {
        hr = HRESULT_FROM_WIN32(static_cast<unsigned>(RegDeleteTree(HKEY_CLASSES_ROOT, szSubkey)));
        ;
    }

    return hr;
}