lpRect
[in, out] Pointer to a RECT structure that contains the coordinates of the top-left and bottom-right corners of the desired client area. When the function returns, the structure contains the coordinates of the top-left and bottom-right corners of the window to accommodate the desired client area.
dwStyle
[in] Specifies the window style of the window whose required size is to be calculated. Note that you cannot specify the WS_OVERLAPPED style.
bMenu
[in] Specifies whether the window has a menu.