XCreateIC ICValues default XNFocusWindow to XNClientWindow if not
specified, it can be omitted since it is the same.
From the documentation
https://www.x.org/releases/current/doc/libX11/libX11/libX11.html
> Focus Window
>
> The XNFocusWindow argument specifies the focus window. The primary
> purpose of the XNFocusWindow is to identify the window that will receive
> the key event when input is composed.
>
> When this XIC value is left unspecified, the input method will use the
> client window as the default focus window.
