martin rudalics <rudalics@gmx.at> writes:

>>> Its definition is conditional on !USE_GTK || !HAVE_GTK3, but its use
>>> only on !USE_GTK.  Which one is right?
>>
>> The !USE_GTK one, I think.
>
> It's a tad more complicated.  You have to do something like the below.
>
> martin
>
> diff --git a/src/xfns.c b/src/xfns.c
> index 481ee0e225..82424ae080 100644
> --- a/src/xfns.c
> +++ b/src/xfns.c
> @@ -4663,6 +4663,9 @@ x_get_net_workarea (struct x_display_info *dpyinfo, XRectangle *rect)
>    return result;
>  }
>
> +#endif /* !defined USE_GTK || !defined HAVE_GTK3 */
> +#if !defined USE_GTK
> +
>  /* Return monitor number where F is "most" or closest to.  */
>  static int
>  x_get_monitor_for_frame (struct frame *f,

What about this?