Question

When I run this code, the text is updated AFTER the message box in the thread is popped.

void PnlOptions::ClickHandler() {
    SetWindowText(txt_progress_, "CLASS MEMBER FUNCTION");

    HANDLE hThread = (HANDLE) _beginthreadex(0, 0, &ThreadProcess, 0, CREATE_SUSPENDED, 0);

    ResumeThread(hThread);
    WaitForSingleObject(hThread, INFINITE);
    CloseHandle(hThread);
}

unsigned int __stdcall ThreadProcess(void * data0) {
    MessageBox(NULL, "THREAD FREE FUNCTION", "Alert", MB_OK);
}

I thought it was because

If the thread is created in a runnable state (that is, if the CREATE_SUSPENDED flag is not used), the thread can start running before CreateThread returns and, in particular, before the caller receives the handle and identifier of the created thread.

but using a non-suspended thread: same result.

Also tried:

• Using CreateThread

• Changing thread priority

• Using SendMessage instead of SetWindowText

• PeekMessage

Why does the thread start before the UI is updated?

---

Declarations:

pnl_options.h:

unsigned int __stdcall ThreadProcess(void *);

public PnlOptions:
     void Init(HWND);
     void ClickHandler();

private:
     HWND txt_progress_;

pnl_options.cpp (other than above code):

 void PnlOptions::Init(HWND hwnd0) {
    txt_progress_ = CreateWindowEx (0,
        TEXT("EDIT"), "Press \"GO\" to process all selected files.",
        SS_LEFT | SS_CENTERIMAGE | WS_VISIBLE | WS_CHILD,
        0, 0, 0, 0,
        hwnd0, (HMENU) IDT_PROGRESSTEXT, NULL, NULL
        );   
 }

Answer 1

I reproduced this behavior and it seems that there is a kind of deadlock between the EDIT control and his parent window because of a posted WM_PAINT message.

“Curioser”, it works if you replace the EDIT with a STATIC control.

I don’t have real explanation/solution for this, so it’s more a clue than an answer…

PS: Note that SS_LEFT and SS_CENTERIMAGE are not valid for an EDIT control, use ES_* defines instead.