tikz 箭头类型沿弯曲路径改变节点定位？

Question

我试图将方形节点定位在弯曲路径的中间，但我注意到我选择的箭头样式会影响定位——如果我使用默认箭头以外的箭头，节点将“偏离中心”定位在路径的法线方向。有没有其他方法可以指定这一点，让节点正确居中，例如使用“latex”样式的箭头？

\documentclass[border=10pt]{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
  \draw[<->,bend angle=90,thick] (-1,-1)
  to[bend right] 
  node[rectangle,sloped,fill=black,minimum size=1mm,inner sep=0pt] {}
  (1,0);
  \begin{scope}[shift={(2,0)}]
    \draw[<->,>=stealth,bend angle=90,thick] (-1,-1) to[bend right] 
    node[rectangle,sloped,fill=black,minimum size=1mm,inner sep=0pt] {}
    (1,0);
  \end{scope}
  \begin{scope}[shift={(4,0)}]
    \draw[<->,>=latex,bend angle=90,thick] (-1,-1) to[bend right] 
    node[rectangle,sloped,fill=black,minimum size=1mm,inner sep=0pt] {}
    (1,0);
  \end{scope}
\end{tikzpicture}
\end{document}

Answer 1

这个问题可以通过使用 TikZ 库来解决bending。

\documentclass[border=10pt]{standalone}

\usepackage{tikz}
\usetikzlibrary{bending}

\tikzset{%
  my node/.style={rectangle,sloped,fill=black,minimum size=1mm,inner sep=0pt},
  draw my path/.style={draw,bend angle=90,thick,#1},
}

\begin{document}

\begin{tikzpicture}
  \draw[draw my path={<->}] (-1,-1) to[bend right] node[my node] {} (1,0);

  \begin{scope}[shift={(2,0)}]
    \path[draw my path={<->,>=stealth}] (-1,-1) to[bend right] node[my node] {} (1,0);
  \end{scope}

  \begin{scope}[shift={(4,0)}]
    \path[draw my path={<->,>=latex}] (-1,-1) to[bend right] node[my node] {} (1,0);
  \end{scope}

\end{tikzpicture}

\end{document}

看来，计算节点位置所用的路径和绘制和添加箭头所用的路径是不同的。我拼凑了以下内容来展示差异：红色是节点路径的颜色。

代码：

\documentclass[border=10pt]{standalone}

\usepackage{tikz}
%\usetikzlibrary{bending}

\tikzset{%
  my node/.style={rectangle,sloped,fill=black,minimum size=1mm,inner sep=0pt,#1},
  draw my path/.style={draw,bend angle=90,thick,#1},
}

\begin{document}

\begin{tikzpicture}
  \draw[draw my path={<->}] (-1,-1) to[bend right] node[my node] {} (1,0);

  \begin{scope}[shift={(2,0)}]
    \path[orange,draw my path,thin]  (-1,-1) to[bend right] node[my node] {} (1,0);
    \path[draw my path={<->,>=stealth}] (-1,-1) to[bend right] node[my node] {} (1,0);
  \end{scope}

  \begin{scope}[shift={(4,0)}]
    \path[orange,draw my path,thin]  (-1,-1) to[bend right] node[my node] {} (1,0);
    \path[draw my path={<->,>=latex}] (-1,-1) to[bend right] node[my node] {} (1,0);
  \end{scope}

\end{tikzpicture}

\end{document}