windmove-reference-loc
windmove-reference-loc is a compiled Lisp function in `windmove.el
'.
(windmove-reference-loc &optional ARG WINDOW)
Return the reference location for directional window selection.
Return a coordinate (HPOS . VPOS) that is frame-based. If ARG is nil
or not supplied, the reference point is the buffer's point in the
currently-selected window, or WINDOW if supplied; otherwise, it is the
top-left or bottom-right corner of the selected window, or WINDOW if
supplied, if ARG is greater or smaller than zero, respectively.