Tikz：如何存储节点的坐标

Question

我需要获取一个节点（西和东）的 2 个 X 值，将它们保存为变量，然后使用它们进行一些计算。以下是一些显然不起作用的伪代码：

\usepackage{fp}
\usepackage{tikz}
\usetikzlibrary{calc}    

\path let
    \p{W}=(node1.west),
    \p{E}=(node1.east)
in
    \def\nWest{\x{W}} % Here, I get an error everytime I try to any commands
    \def\nEast{\x{E}}
;
\def\nWidth {} % Also, is it possible to do calculations right here in the definition?
\FPeval\num{clip((nEast-nWest)/3)} % This may be more complex in the final code.

Answer 1

如以下示例所示，这是可能的：

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc}
\begin{document}
\begin{tikzpicture}
\node[draw,minimum width=3cm](node1) {};
\path
  let
  \p1=(node1.west),
  \p2=(node1.east),
  \n1={abs(\x2-\x1)/3} in node[
    draw,red,
    minimum width=\n1,] {};

\end{tikzpicture}
\end{document}

如果您想在这里使用\def(或\xdef) 等，请\pgfextra类似地使用：

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc}
\begin{document}
\begin{tikzpicture}
\node[draw,minimum width=3cm](node1) {};
\path
  let
  \p1=(node1.west),
  \p2=(node1.east),
  \n1={abs(\x2-\x1)/3} in
  \pgfextra{
    \newlength{\mylen}
    \setlength{\mylen}{\n1}
    }
    node[
    draw,red,
    minimum width=\mylen,] {};

\end{tikzpicture}
\end{document}