under

#!/bin/sh
#
# under

main() {
    mouse="$(wmp)"
    pointX=${mouse% *}
    pointY=${mouse#* }

    for wid in $( (lsw; lsw -o) | tac); do
        windowX="$(wattr x "$wid")"
        windowY="$(wattr y "$wid")"

        # no match if the left and top edges are greater than X or Y
        [ "$windowX" -gt "$pointX" ] && continue
        [ "$windowY" -gt "$pointY" ] && continue

        windowW="$(wattr w "$wid")"
        windowH="$(wattr h "$wid")"

        # no match if the right and bottom edges are less than X or Y
        [ "$((windowX + windowW))" -lt "$pointX" ] && continue
        [ "$((windowY + windowH))" -lt "$pointY" ] && continue

        # print wid on detection if no args passed
        [ "$#" -eq 0 ] && printf '%s\n' "$wid"
        exit
    done

    # run args as command to shell as no window was detected
    [ "$#" -gt 0 ] && sh -c "$@"
}

main "$@"