将文本拉伸至节点内边界框的宽度

Question

给出下面的代码，谜题中缺少的部分是从内部确定边界框的宽度（这应该比从外面）。

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{tikz}
\usetikzlibrary{backgrounds, calc}

\begin{document}

\newlength{\myl}

\begin{tikzpicture}
  \draw (-2,-1) rectangle (2,1);
  \begin{pgfonlayer}{background}
    \path[fill=red](current bounding box.south west)rectangle(current bounding box.north east);
  \end{pgfonlayer}

%\settowidth{\myl}{current bounbind box.width} % HOW TO?
\coordinate (sw) at (current bounding box.south west);
%\node[black,above right] at (sw) {\the\myl}; % (0pt)

  \node[above right,
  text width=5em
%  text width=\myl
  ] (bottom) at (current bounding box.south west) {\color{black}
    %\makebox[\myl]{%
      A\hspace*{\fill}Z
    %}
  };

% UPDATE:

\path (bottom.north west) coordinate (SW);
\node[black] (SW) {SW};
  
\end{tikzpicture}

\end{document}

更新＃1：

辅助问题是，我本来预计位于（A）-（Z）边界框的西南西北方向：为什么它离得这么远？

更新 # 2：以下是澄清

  \node[above right,
  text width=5em
%  text width=\myl
  ] (bottom) at (current bounding box.south west) {\color{black}
    \frame{\makebox[5em]{A\hspace*{\fill}Z}}
    };

Answer 1

您可以使用锚点来实现这种自动拉伸。这样就不需要计算矩形的宽度了。

\documentclass[tikz, border=5pt]{standalone}
\usetikzlibrary{backgrounds}

\begin{document}

\begin{tikzpicture}
  \draw (-2,-1) rectangle (2,1);
  \begin{pgfonlayer}{background}
    \path[fill=red] (current bounding box.south west) rectangle (current bounding box.north east);
  \end{pgfonlayer}

  \node[text=black, anchor=south west] (bottoml) at (current bounding box.south west) {A};
  \node[text=black, anchor=south east] (bottomr) at (current bounding box.south east) {Z};

  \node[text=black, anchor=south west] at (bottoml.north west) {SW};
  
\end{tikzpicture}

\end{document}

顺便说一句，我可能会先定义矩形角的坐标，然后使用它们来绘制矩形并放置节点。您应该考虑一下是否真的需要这个backgrounds库。带有黑色边框的红色矩形可以轻松用 绘制\draw[fill=red] (-2,-1) rectangle (2,1);。

---

更新：

如果你真的想计算矩形的宽度，你确实可以使用所引用的方法：

\begin{tikzpicture}
  \draw (-2,-1) rectangle (2,1);
  \begin{pgfonlayer}{background}
    \path[fill=red] (current bounding box.south west) rectangle (current bounding box.north east);
  \end{pgfonlayer}

  \newdimen\myl
  \pgfextractx{\myl}{\pgfpointdiff{\pgfpointanchor{current bounding box}{west}}
 {\pgfpointanchor{current bounding box}{east}}}

  \node at (0,0) {\the\myl};

  \node[text=black, draw, anchor=south west, text width={\myl-2*\pgfkeysvalueof{/pgf/inner xsep}-2*\pgflinewidth}] (bottoml) at (current bounding box.south west) {A \hfill Z};
  
  \node[text=black, anchor=south west] at (bottoml.north west) {SW};
  
\end{tikzpicture}

代码将两个坐标current bounding box.west和x 值的差值存储current bounding box.east在新定义的维度宏 ( \myl) 中。这几乎就是您已有的。但是，您不能直接使用它，因为您仍然需要从此宽度中减去节点的inner sep(padding) 和边框宽度以使其适合。inner sep可以用 评估的(horizo​​ntal) 的值\pgfkeysvalueof{/pgf/inner xsep}以及可以用 评估的边框的值\pgflinewidth都需要乘以 2，因为 padding 和 border 位于节点的两侧。

Answer 2

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{tikz}
\usetikzlibrary{backgrounds, calc, shapes, positioning}

\begin{document}
    
    \newlength{\myl}
    
    \begin{tikzpicture}
        \node[rectangle, draw, fill=red, inner sep=2.5cm,]at(0,0)(a){};
        \node at( a.south west) {\color{black}A};
        \node at($( a.south west)+(5cm,0cm)$) {\color{black}Z};
        
        % UPDATE:
        
        \path (a.north west) coordinate (SW);
        \node[black] at(SW.east) {SW};
        
    \end{tikzpicture}
    
\end{document}