为什么我的 IExtractIcon 处理程序没有被调用？

我正试图在C++中实现一个基于示例的图标处理程序：

编写外壳扩展程序的完整白痴指南-第九部分

我使用示例项目使示例正常工作没有问题，但当我尝试在QT项目中构建它时，我的处理程序永远不会被调用。

在安装了我的DLL之后，‘ShellExtView’将它显示为一个"；图标处理程序"；据我所见，注册表中的一切看起来都很好。

我使用了这里的注册代码，并用它来注册示例shell扩展，它起到了作用，所以我认为注册shell扩展的方式没有问题。

这是我的代码：

头文件：

#include <Windows.h>
// ATL
#include <atlbase.h>
extern CComModule _Module;
#include <atlcom.h>
#include <atlconv.h>
// Win32
#include <comdef.h>
#include <ShlObj.h>
#define MAX_SUFFIX (32)
#define MY_ID "{E94EFFAC-DBD6-40EF-92FC-460FDEB3684A}"
#define TARGET_ICON_HANDLER_CLASS "txtfile"
const CLSID my_id = {0xE94EFFAC, 0xDBD6, 0x40EF, {0x92, 0XF, 0X46, 0X0F, 0XDE, 0XB3, 0X68, 0X4A}};
const CLSID myLib_id = {0xE94EFFAD, 0xDBD6, 0x40EF, {0x92, 0XF, 0X46, 0X0F, 0XDE, 0XB3, 0X68, 0X4A}};

class CIconShlExt :
public CComObjectRootEx<CComSingleThreadModel>,
public CComCoClass<CIconShlExt, &my_id>,
public IPersistFile,
public IExtractIcon
{
public:
CIconShlExt() : m_haveSuffix(false) { }
BEGIN_COM_MAP(CIconShlExt)
COM_INTERFACE_ENTRY(IPersistFile)
COM_INTERFACE_ENTRY(IExtractIcon)
END_COM_MAP()
DECLARE_NO_REGISTRY()
// IPersistFile
STDMETHODIMP GetClassID( CLSID* pClsId)  { return E_NOTIMPL; }
STDMETHODIMP IsDirty() { return E_NOTIMPL; }
STDMETHODIMP Save( LPCOLESTR, BOOL ) { return E_NOTIMPL; }
STDMETHODIMP SaveCompleted( LPCOLESTR ) { return E_NOTIMPL; }
STDMETHODIMP GetCurFile( LPOLESTR* ) { return E_NOTIMPL; }
STDMETHODIMP Load( LPCOLESTR wszFile, DWORD );
// IExtractIcon
STDMETHODIMP GetIconLocation( UINT uFlags, LPTSTR szIconFile, UINT cchMax,
int* piIndex, UINT* pwFlags );
STDMETHODIMP Extract( LPCTSTR pszFile, UINT nIconIndex, HICON* phiconLarge,
HICON* phiconSmall, UINT nIconSize );
WCHAR m_suffix[MAX_SUFFIX];
bool  m_haveSuffix;
};

IPersistFile和IExtractIcon方法(从不调用(:

#pragma region IPersistFile
STDMETHODIMP CIconShlExt::Load(LPCOLESTR wszFile, DWORD)
{
// I never get here!
return S_OK;
}
#pragma endregion

#pragma region IExtractIcon
STDMETHODIMP CIconShlExt::GetIconLocation(UINT /*uFlags*/, LPTSTR szIconFile, UINT cchMax, int* piIndex, UINT* pwFlags )
{
// I never get here!
// Give it a strange icon so I know it did something
*piIndex = -218;
lstrcpyn(szIconFile, "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\Common7\IDE\msenvico.dll", cchMax);
*pwFlags = GIL_PERINSTANCE; // GIL_NOTFILENAME;
return S_OK;
}
STDMETHODIMP CIconShlExt::Extract( LPCTSTR , UINT , HICON*, HICON* , UINT)
{
return S_FALSE;
}
#pragma endregion

主DLL文件：

static DWORD SetRegistryKeyAndValue(HKEY root, const char *key, const char *value, const char *name)
{
HKEY hKey = NULL;
DWORD err;
err = RegCreateKeyEx(root, key, 0, NULL, REG_OPTION_NON_VOLATILE, KEY_WRITE, NULL, &hKey, NULL);
if (err == ERROR_SUCCESS) {
if (name != NULL) {
// Set the specified value of the key.
DWORD cbData = lstrlen(name) * sizeof(*name) +1;
err = RegSetValueEx(hKey, value, 0, REG_SZ, reinterpret_cast<const BYTE *>(name), cbData);
}
RegCloseKey(hKey);
}
return err;
}
static void unregisterHandler()
{
RegDeleteTree(HKEY_CLASSES_ROOT, "CLSID\" MY_ID);
RegDeleteKey(HKEY_LOCAL_MACHINE, "Software\Microsoft\Windows\CurrentVersion\Shell Extensions\Approved\" MY_ID);
RegDeleteTree(HKEY_CLASSES_ROOT, TARGET_ICON_HANDLER_CLASS "\ShellEx\IconHandler");
}
static DWORD registerHandler(const char *dll)
{
DWORD err;
if ((err = SetRegistryKeyAndValue(HKEY_CLASSES_ROOT, "CLSID\" MY_ID, nullptr, "My icon extension")) != ERROR_SUCCESS)
goto error;
if ((err = SetRegistryKeyAndValue(HKEY_CLASSES_ROOT, "CLSID\" MY_ID"\InprocServer32", NULL, dll)) != ERROR_SUCCESS)
goto error;
if ((err = SetRegistryKeyAndValue(HKEY_CLASSES_ROOT, "CLSID\" MY_ID"\InprocServer32", "ThreadingModel", "Apartment")) != ERROR_SUCCESS)
goto error;
if ((err = SetRegistryKeyAndValue(HKEY_LOCAL_MACHINE, "Software\Microsoft\Windows\CurrentVersion\Shell Extensions\Approved", MY_ID, "My icon extension")) != ERROR_SUCCESS)
goto error;
if ((err = SetRegistryKeyAndValue(HKEY_CLASSES_ROOT, TARGET_ICON_HANDLER_CLASS "\ShellEx\IconHandler", nullptr, MY_ID)) != ERROR_SUCCESS)
goto error;
if ((err = SetRegistryKeyAndValue(HKEY_CLASSES_ROOT, TARGET_ICON_HANDLER_CLASS "\DefaultIcon", nullptr, "%1")) != ERROR_SUCCESS)
goto error;
return err;
error:
unregisterHandler();
return err;
}

BEGIN_OBJECT_MAP(ObjectMap)
OBJECT_ENTRY(my_id, CIconShlExt)
END_OBJECT_MAP()
CComModule _Module;
extern "C"
BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD dwReason, LPVOID /*lpReserved*/)
{
if (dwReason == DLL_PROCESS_ATTACH)
{
_Module.Init(ObjectMap, hInstance, &myLib_id);
DisableThreadLibraryCalls(hInstance);
}
else if (dwReason == DLL_PROCESS_DETACH)
_Module.Term();
return TRUE;    // ok
}
/////////////////////////////////////////////////////////////////////////////
// Used to determine whether the DLL can be unloaded by OLE
STDAPI DllCanUnloadNow()
{
return (_Module.GetLockCount()==0) ? S_OK : S_FALSE;
}
/////////////////////////////////////////////////////////////////////////////
// Returns a class factory to create an object of the requested type
STDAPI DllGetClassObject(REFCLSID rclsid, REFIID riid, LPVOID* ppv)
{
return _Module.GetClassObject(rclsid, riid, ppv);
}
STDAPI DllRegisterServer()
{
char dllPath[MAX_PATH];
if (GetModuleFileName(_Module.m_hInst, dllPath, ARRAYSIZE(dllPath)) == 0)
{
HRESULT hr = HRESULT_FROM_WIN32(GetLastError());
return hr;
}
DWORD rtc = registerHandler(dllPath);
if (rtc != ERROR_SUCCESS)
return HRESULT_FROM_WIN32(rtc);
return _Module.RegisterServer(false);
}
STDAPI  DllUnregisterServer(void)
{   
unregisterHandler();
return _Module.UnregisterServer(false);
}