我尝试在C++中实现一个图标处理程序，基于以下示例：
The Complete Idiot's Guide to Writing Shell Extensions - Part IX
使用示例项目使示例工作没有问题，但是当我尝试在QT项目中构建它时，我的处理程序从未被调用。
在安装了我的DLL之后，"ShellExtView"将其显示为"图标处理程序"，并且在注册表中一切正常，就我所见。
我用这里的注册码注册了示例shell扩展，它工作正常，所以我不认为这是注册shell扩展的方式有问题。
下面是我的代码：
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（从未调用）：

#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);
}