PowerToys/src/modules/previewpane/StlThumbnailProviderCpp/dllmain.cpp

// dllmain.cpp : Defines the entry point for the DLL application.
#include "pch.h"
#include "ClassFactory.h"

HINSTANCE g_hInst = NULL;
long g_cDllRef = 0;

// {77257004-6F25-4521-B602-50ECC6EC62A6}
static const GUID CLSID_StlThumbnailProvider = { 0x77257004, 0x6f25, 0x4521, { 0xb6, 0x2, 0x50, 0xec, 0xc6, 0xec, 0x62, 0xa6 } };

BOOL APIENTRY DllMain(HMODULE hModule,
                      DWORD ul_reason_for_call,
                      LPVOID lpReserved)
{
    switch (ul_reason_for_call)
    {
    case DLL_PROCESS_ATTACH:
        g_hInst = hModule;
        DisableThreadLibraryCalls(hModule);
        break;
    case DLL_THREAD_ATTACH:
    case DLL_THREAD_DETACH:
    case DLL_PROCESS_DETACH:
        break;
    }
    return TRUE;
}

//
//   FUNCTION: DllGetClassObject
//
//   PURPOSE: Create the class factory and query to the specific interface.
//
//   PARAMETERS:
//   * rclsid - The CLSID that will associate the correct data and code.
//   * riid - A reference to the identifier of the interface that the caller
//     is to use to communicate with the class object.
//   * ppv - The address of a pointer variable that receives the interface
//     pointer requested in riid. Upon successful return, *ppv contains the
//     requested interface pointer. If an error occurs, the interface pointer
//     is NULL.
//
STDAPI DllGetClassObject(REFCLSID rclsid, REFIID riid, void** ppv)
{
    HRESULT hr = CLASS_E_CLASSNOTAVAILABLE;

    if (IsEqualCLSID(CLSID_StlThumbnailProvider, rclsid))
    {
        hr = E_OUTOFMEMORY;

        ClassFactory* pClassFactory = new ClassFactory();
        if (pClassFactory)
        {
            hr = pClassFactory->QueryInterface(riid, ppv);
            pClassFactory->Release();
        }
    }

    return hr;
}

//
//   FUNCTION: DllCanUnloadNow
//
//   PURPOSE: Check if we can unload the component from the memory.
//
//   NOTE: The component can be unloaded from the memory when its reference
//   count is zero (i.e. nobody is still using the component).
//
STDAPI DllCanUnloadNow(void)
{
    return g_cDllRef > 0 ? S_FALSE : S_OK;
}