Question

I have code:

......
    g_hWnd = CreateWindow( L"Urok6WindowClass", L"TitleWindow", WS_OVERLAPPEDWINDOW,
                           CW_USEDEFAULT, CW_USEDEFAULT, rc.right - rc.left, rc.bottom - rc.top, NULL, NULL, hInstance,
                           NULL );
    if( !g_hWnd )
        return E_FAIL;

    ShowWindow(g_hWnd, nCmdShow );

All works fine. But if I add:

    LPTSTR tilte_old= L"Old title";
    int gettus = GetWindowText(g_hWnd, tilte_old, 100);
    DWORD error = GetLastError();
    WCHAR szTest[10];
    swprintf_s(szTest, 10, L"%d", error); 
    MessageBox(NULL, szTest, L"TEST2", MB_OK); 

MessageBox >> 1400

gettus >> ”

Why is this happening? Why windows handle is invalid?

Answer 1

The second parameter of GetWindowText is an out parameter:

lpString [out]
Type: LPTSTR

The buffer that will receive the text. If the string is as long or longer than the buffer, the string is truncated and terminated with a null character.

So you need to supply a buffer to be filled, not a pointer to a constant string (the third parameter indicates the maximum size of the buffer to avoid overflow)

Try:

const size_t BUFF_SIZE = 100;
TCHAR title_old[BUFF_SIZE];
int gettus = GetWindowText(g_hWnd, title_old, BUFF_SIZE);

Also, you only need to call GetLastError if gettus is 0 (GetWindowText() failed)