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Asked: 2026-05-11T11:05:58+00:00

Using the Win32 APIs, is it possible to create a Window or Dialog in

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Using the Win32 APIs, is it possible to create a Window or Dialog in one thread then collect events for it from another thread?

Are HWNDs tied to threads?

Trying the contrived example below I never see GetMessage() fire.

 HWND g_hWnd;  DWORD WINAPI myThreadProc(LPVOID lpParam) {     while(GetMessage(&msg, hWnd, 0, 0) > 0)     {        ...     }  }  int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)  {     hWnd = CreateDialog(hInstance, MAKEINTRESOURCE(IDD_MYDIALOG), 0, myDlgProc);     CreateThread(NULL, 0 myThreadProc, NULL, 0, NULL);     ... }

But here, I do.

 HWND g_hWnd; HINSTANCE g_hInstance;  DWORD WINAPI myThreadProc(LPVOID lpParam) {     hWnd = CreateDialog(hInstance, MAKEINTRESOURCE(IDD_MYDIALOG), 0, myDlgProc);      while(GetMessage(&msg, hWnd, 0, 0) > 0)     {        ...     }  }  int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)  {     g_hInstance = hInstance;     CreateThread(NULL, 0 myThreadProc, NULL, 0, NULL);     ... }

Can somebody explain what I’m seeing?

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1 Answer

  1. No.

    GetMessage returns messages on the current thread’s input queue. The HWND parameter is a filter, so that GetMessage only returns messages in the current thread’s input queue intended for that window.

    Windows have thread affinity – messages intended for a window get handled on the thread that created and therefore owns the window.

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