Duilib模式对话框DoModal实现

其原理就是通过禁用该窗口的拥有者，便能该窗口。
执行完成后，在该DoModal函数中建立消息循环（因为主消息循环已经卡死）。

UINT CWindowWnd::ShowModal()
{
    ASSERT(::IsWindow(m_hWnd));
    UINT nRet = 0;
    HWND hWndParent = GetWindowOwner(m_hWnd);
    ::ShowWindow(m_hWnd, SW_SHOWNORMAL);
    ::EnableWindow(hWndParent, FALSE);
    MSG msg = { 0 };
    while( ::IsWindow(m_hWnd) && ::GetMessage(&msg, NULL, 0, 0) ) {
        if( msg.message == WM_CLOSE && msg.hwnd == m_hWnd ) {
            nRet = msg.wParam;
            ::EnableWindow(hWndParent, TRUE);
            ::SetFocus(hWndParent);
        }
        if( !CPaintManagerUI::TranslateMessage(&msg) ) {
            ::TranslateMessage(&msg);
            ::DispatchMessage(&msg);
        }
        if( msg.message == WM_QUIT ) break;
    }
    ::EnableWindow(hWndParent, TRUE);
    ::SetFocus(hWndParent);
    if( msg.message == WM_QUIT ) ::PostQuitMessage(msg.wParam);
    return nRet;
}