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copied!<p>I finally had some time to figure out what is happening, so I wrote a short test to see what is going on.</p> <pre><code>// MarshalTest.cpp : Defines the entry point for the console application. // #include "stdafx.h" enum { WM_THEREYOUGO = WM_USER+1, WM_THANKYOU, WM_YOURWELCOME }; DWORD WINAPI TheOtherThread(DWORD * main_thread_id) { MSG msg = { 0 }; HRESULT hr = CoInitializeEx(NULL, COINIT_APARTMENTTHREADED); assert(SUCCEEDED(hr)); { // create web browser CComPtr<IWebBrowser2> wb; hr = wb.CoCreateInstance(CLSID_InternetExplorer, 0, CLSCTX_SERVER); assert(SUCCEEDED(hr) && wb); // navigate hr = wb->Navigate2(&CComVariant(_T("stackoverflow.com")), &CComVariant(0), &CComVariant(_T("")), &CComVariant(), &CComVariant()); assert(SUCCEEDED(hr)); hr = wb->put_Visible(VARIANT_TRUE); assert(SUCCEEDED(hr)); // Marshal DWORD the_cookie = 0; { CComPtr<IGlobalInterfaceTable> com_broker; hr = com_broker.CoCreateInstance(CLSID_StdGlobalInterfaceTable); assert(SUCCEEDED(hr)); hr = com_broker->RegisterInterfaceInGlobal(wb, __uuidof(IWebBrowser2), &the_cookie); } // notify main thread PostThreadMessage(*main_thread_id, WM_THEREYOUGO, the_cookie, NULL); // message loop while(GetMessage(&msg, 0, 0, 0)) { if(msg.hwnd == NULL) { // thread message switch(msg.message) { case WM_THANKYOU: PostQuitMessage(0); break; } } else { TranslateMessage(&msg); DispatchMessage(&msg); } } } CoUninitialize(); PostThreadMessage(*main_thread_id, WM_YOURWELCOME, 0, NULL); return msg.wParam; } int _tmain(int argc, _TCHAR* argv[]) { MSG msg = {0}; DWORD main_thread_id = GetCurrentThreadId(); HRESULT hr = CoInitializeEx(NULL, COINIT_APARTMENTTHREADED); assert(SUCCEEDED(hr)); { DWORD ThreadId = 0; HANDLE hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)TheOtherThread, &main_thread_id, 0, &ThreadId); DWORD the_cookie = 0; CComPtr<IWebBrowser2> wb, wb2; while(GetMessage(&msg, 0, 0, 0)) { if(msg.hwnd == NULL) { // thread message switch(msg.message) { case WM_THEREYOUGO: // we got the cookie. the_cookie = msg.wParam; // get the browser. This should work. { CComPtr<IGlobalInterfaceTable> com_broker; hr = com_broker.CoCreateInstance(CLSID_StdGlobalInterfaceTable); assert(SUCCEEDED(hr)); hr = com_broker->GetInterfaceFromGlobal(the_cookie, __uuidof(IWebBrowser2), (void**)&wb); assert(SUCCEEDED(hr) && wb); } // do something with it. hr = wb->put_FullScreen(VARIANT_TRUE); assert(SUCCEEDED(hr)); // signal the other thread. PostThreadMessage(ThreadId, WM_THANKYOU, 0, NULL); break; case WM_YOURWELCOME: // the other thread has ended. PostQuitMessage(0); break; } } else { TranslateMessage(&msg); DispatchMessage(&msg); } } // the other thread has ended. Try getting the interface again. { CComPtr<IGlobalInterfaceTable> com_broker; hr = com_broker.CoCreateInstance(CLSID_StdGlobalInterfaceTable); assert(SUCCEEDED(hr)); hr = com_broker->GetInterfaceFromGlobal(the_cookie, __uuidof(IWebBrowser2), (void**)&wb2); //assert(SUCCEEDED(hr) && wb2); // this fails, hr == E_INVALIDARG. // clean up, will not be executed. if(SUCCEEDED(hr)) { hr = com_broker->RevokeInterfaceFromGlobal(the_cookie); } } // try using it if(wb2) { hr = wb2->put_FullScreen(VARIANT_FALSE); assert(SUCCEEDED(hr)); } else if(wb) { // this succeeds hr = wb->put_FullScreen(VARIANT_FALSE); assert(SUCCEEDED(hr)); } CloseHandle(hThread); } CoUninitialize(); return msg.wParam; } </code></pre> <hr> <p>The bottom line is this:</p> <ul> <li>Ending the thread that registered the interface invalidates the cookie.</li> <li>The already marshaled interface stays valid. (In this case, that is.)</li> </ul> <p>This means that I get a proxy to the IE process instead of to the other thread's object.</p>

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