아래 예에서  draw let 부분에서 \n1을 삭제하고 \p3, \p4를 각각 (barycentric cs:#3=1,\p1=4), (barycentric cs:#2=1,\p2=4)로 하면 좌표를 찾을 수 없다라는 오류가 납니다. 아례 예제 밖에 방법이 없나요?

\documentclass[12pt]{standalone}
\usepackage{tikz}
\usepackage{tkz-euclide}
\usetikzlibrary{3d,calc,math,angles,positioning,intersections,decorations.markings,backgrounds,patterns,through}
\def\segmentmeasureone[#1](#2,#3)#4#5#6{%
\begin{scope}[on background layer]
    \draw let
        \p1=($(#3)!#4mm!90:(#2)$),
        \p2=($(#2)!#4mm!-90:(#3)$),
        \n1={0.8*#4},
        \p3=($(#3)!\n1mm!90:(#2)$),
        \p4=($(#2)!\n1mm!-90:(#3)$),
     in
        (#3) -- (\p1) (#2) -- (\p2) 
        [<->] (\p3)--(\p4) node[pos=#5,#1,inner sep=1pt] (#2#3segment) {#6};
        \end{scope}
}%
\begin{document}
\begin{tikzpicture}[scale=0.7]

\draw (0,0) coordinate (A) node[below] {A} 
--
(4,3) coordinate (B) node[right] {B};
\segmentmeasureone[fill=white](B,A){8}{0.5}{$x$};

\end{tikzpicture}
\end{document}