How to hook the ItaskbarList4 class?

Question

I'm trying to customize the taskbar buttons, for this i'm hooking the ItaskbarList4 class using Detours, however, the functions on MyTaskbarList isn't getting called, trying to figure out what's wrong:

inline HRESULT(WINAPI* CoCreateInstance_O)(REFCLSID rclsid, LPUNKNOWN pUnkOuter, DWORD dwClsContext, REFIID riid, LPVOID* ppv) = CoCreateInstance;

class MyTaskbarList : public ITaskbarList4 {
public:
    MyTaskbarList(ITaskbarList4* original) : m_original(original) {}
    // IUnknown methods
    HRESULT STDMETHODCALLTYPE QueryInterface(REFIID riid, void** ppvObject) override {
        if (riid == __uuidof(IUnknown) || riid == __uuidof(ITaskbarList4)) {
            *ppvObject = static_cast<ITaskbarList4*>(this);
            AddRef();
            return S_OK;
        }
        *ppvObject = nullptr;
        return E_NOINTERFACE;
    }
    ULONG STDMETHODCALLTYPE AddRef() override {
        return InterlockedIncrement(&m_refCount);
    }
    ULONG STDMETHODCALLTYPE Release() override {
        ULONG refCount = InterlockedDecrement(&m_refCount);
        if (refCount == 0) {
            delete this;
        }
        return refCount;
    }
    HRESULT STDMETHODCALLTYPE HrInit() override {
        return m_original->HrInit();
    }
    HRESULT STDMETHODCALLTYPE AddTab(HWND hwnd) override {
        return m_original->AddTab(hwnd);
    }
    HRESULT STDMETHODCALLTYPE DeleteTab(HWND hwnd) override {
        return m_original->DeleteTab(hwnd);
    }
    HRESULT STDMETHODCALLTYPE ActivateTab(HWND hwnd) override {
        return m_original->ActivateTab(hwnd);
    }
    HRESULT STDMETHODCALLTYPE SetActiveAlt(HWND hwnd) override {
        return m_original->SetActiveAlt(hwnd);
    }
    HRESULT STDMETHODCALLTYPE MarkFullscreenWindow(HWND hwnd, BOOL fFullscreen) override {
        return m_original->MarkFullscreenWindow(hwnd, fFullscreen);
    }
    HRESULT STDMETHODCALLTYPE SetProgressValue(HWND hwnd, ULONGLONG ullCompleted, ULONGLONG ullTotal) override {
        return m_original->SetProgressValue(hwnd, ullCompleted, ullTotal);
    }
    HRESULT STDMETHODCALLTYPE SetProgressState(HWND hwnd, TBPFLAG tbpFlags) override {
        return m_original->SetProgressState(hwnd, tbpFlags);
    }
    HRESULT STDMETHODCALLTYPE RegisterTab(HWND hwndTab, HWND hwndMDI) override {
        OutputDebugStringW(L"RegisterTab");
        return m_original->RegisterTab(hwndTab, hwndMDI);
    }
    HRESULT STDMETHODCALLTYPE UnregisterTab(HWND hwndTab) override {
        return m_original->UnregisterTab(hwndTab);
    }
    HRESULT STDMETHODCALLTYPE SetTabOrder(HWND hwndTab, HWND hwndInsertBefore) override {
        return m_original->SetTabOrder(hwndTab, hwndInsertBefore);
    }
    HRESULT STDMETHODCALLTYPE SetTabActive(HWND hwndTab, HWND hwndMDI, DWORD dwReserved) override {
        return m_original->SetTabActive(hwndTab, hwndMDI, dwReserved);
    }
    HRESULT STDMETHODCALLTYPE ThumbBarAddButtons(HWND hwnd, UINT cButtons, LPTHUMBBUTTON pButton) override {
        return m_original->ThumbBarAddButtons(hwnd, cButtons, pButton);
    }
    HRESULT STDMETHODCALLTYPE ThumbBarUpdateButtons(HWND hwnd, UINT cButtons, LPTHUMBBUTTON pButton) override {
        return m_original->ThumbBarUpdateButtons(hwnd, cButtons, pButton);
    }
    HRESULT STDMETHODCALLTYPE ThumbBarSetImageList(HWND hwnd, HIMAGELIST himl) override {
        return m_original->ThumbBarSetImageList(hwnd, himl);
    }
    HRESULT STDMETHODCALLTYPE SetOverlayIcon(HWND hwnd, HICON hIcon, LPCWSTR pszDescription) override {
        return m_original->SetOverlayIcon(hwnd, hIcon, pszDescription);
    }
    HRESULT STDMETHODCALLTYPE SetThumbnailTooltip(HWND hwnd, LPCWSTR pszTip) override {
        return m_original->SetThumbnailTooltip(hwnd, pszTip);
    }
    HRESULT STDMETHODCALLTYPE SetThumbnailClip(HWND hwnd, RECT* prcClip) override {
        return m_original->SetThumbnailClip(hwnd, prcClip);
    }
    HRESULT STDMETHODCALLTYPE SetTabProperties(HWND hwndTab, STPFLAG stpFlags) override {
        return m_original->SetTabProperties(hwndTab, stpFlags);
    }
private:
    ITaskbarList4* m_original;
    LONG m_refCount;
};



HRESULT WINAPI CoCreateInstance_H(REFCLSID rclsid, LPUNKNOWN pUnkOuter, DWORD dwClsContext, REFIID riid, LPVOID* ppv)
{
    if (rclsid == CLSID_TaskbarList)
    {
        if (riid == IID_ITaskbarList4)
        {
            ITaskbarList4* original;
            HRESULT hr = CoCreateInstance_O(rclsid, pUnkOuter, dwClsContext, riid, (void**)&original);
            OutputDebugStringW(L"CoCreateInstance_H");
            if (SUCCEEDED(hr))
            {
                *ppv = new MyTaskbarList(original);
                OutputDebugStringW(L"success");
            }
            return hr;
        }
    }
	return CoCreateInstance_O(rclsid, pUnkOuter, dwClsContext, riid, ppv);
}

#include "stdafx.h"
#include "Detours.h"
#pragma comment(lib, "detours.lib")
BOOL APIENTRY DllMain( HMODULE hModule, DWORD  ul_reason_for_call, LPVOID lpReserved)
{
    switch (ul_reason_for_call)
    {
        case DLL_PROCESS_ATTACH:
        {
            DetourTransactionBegin();
            DetourUpdateThread(GetCurrentThread());
            DetourAttach(&(PVOID&)CoCreateInstance_O, CoCreateInstance_H);
        }
    }
    return TRUE;
}

Answer 1

I used Microsoft's TabThumbnails sample to demonstrate using an activation filter to intercept CLSID_TaskbarList creation to instantiate a wrapper object.

Instantiate the COM object that implements IActivationFilter and register it -

Results showing the COM interception while the sample application runs -

Answer 2

There are other ways of intercepting COM interfaces and their methods besides Detours. For example, registering a process activation filter using the CoRegisterActivationFilter function could cause COM to instantiate your wrapper object when processing CoCreateInstance for CLSID_TaskbarList.