避免线交叉

Question

intersections以下是使用库的一种可能性TikZ：

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{intersections}

\newcommand\tikzmark[1]{%
  \tikz[remember picture,overlay]\node[inner xsep=0pt,inner ysep=10pt,outer sep=0pt] (#1) {};}

\begin{document}

\[
\tikzmark{c}2:\tikzmark{a}3 + 5:\tikzmark{d}3+\tikzmark{b}2:3+5:3
\]

\begin{tikzpicture}[remember picture,overlay]
\draw[name path=line1,red,->] ([xshift=2pt]a.north east) -- +(0pt,10pt) -| ([xshift=2pt]b.north east);
\path[name path=line2] ([xshift=2pt]c.north east) -- +(0pt,23pt) -| ([xshift=2pt]d.north east);
\draw[name intersections={of=line1 and line2,by={int}},draw,->,red] 
  ([xshift=2pt]c.north east) -- +(0pt,23pt) -| ([yshift=3pt]int) arc(90:-90:2.5pt) -- ([xshift=2pt]d.north east);
\end{tikzpicture}

\end{document}

在此处输入图片描述

这个想法是利用无处不在的\tikzmark来为路径放置标记，然后找到两条路径的交点，然后在交点处画一个弧。

上述代码第一次运行将导致错误：

! Package pgf Error: No shape named intersection-1 is known.

See the pgf package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.19 ...{of=line1 and line2,by={int}},draw,->,red]

由于标记的坐标尚不清楚，因此路径交点的计算失败。退出编译并重新编译，应该会得到所需的结果。

在聊天中，大卫·卡莱尔建议进行如下修改：

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{intersections}

\newcommand\tikzmark[1]{%
  \tikz[remember picture,overlay]\node[inner xsep=0pt,inner ysep=10pt,outer sep=0pt] (#1) {};%
}

\begin{document}

\[
\tikzmark{c}2:\tikzmark{a}3 + 5:\tikzmark{d}3+\tikzmark{b}2:3+5:3
\]

\expandafter \ifx\csname pgf@sys@pdf@mark@pos@pgfid\the \csname
pgf@picture@serial@count\endcsname\endcsname\relax
\typeout{no}%
\else
\typeout{yes}%
\begin{tikzpicture}[remember picture,overlay]
\draw[name path=line1,red,->] ([xshift=2pt]a.north east) -- +(0pt,10pt) -| ([xshift=2pt]b.north east);
\path[name path=line2] ([xshift=2pt]c.north east) -- +(0pt,23pt) -| ([xshift=2pt]d.north east);
\draw[name intersections={of=line1 and line2,by={int}},draw,->,red] 
  ([xshift=2pt]c.north east) -- +(0pt,23pt) -| ([yshift=3pt]int) arc(90:-90:2.5pt) -- ([xshift=2pt]d.north east);
\end{tikzpicture}
\fi

\end{document}

不会产生错误。该文档必须运行三次。

现在敲击提供了以下替代方案：

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{intersections}

\newcommand\tikzmark[1]{%
  \tikz[remember picture,overlay]\node[inner xsep=0pt,inner ysep=10pt,outer sep=0pt] (#1) {};}

\begin{document}

\[
\tikzmark{c}2:\tikzmark{a}3 + 5:\tikzmark{d}3+\tikzmark{b}2:3+5:3
\]

\begin{tikzpicture}[remember picture,overlay]
\draw[name path=line1,red,->] ([xshift=2pt]a.north east) -- +(0pt,10pt) -| ([xshift=2pt]b.north east);
\path[name path=line2] ([xshift=2pt]c.north east) -- +(0pt,23pt) -| ([xshift=2pt]d.north east);
\path[name intersections={of=line1 and line2,total=\totinter}] \pgfextra{\xdef\totinter{\totinter}};
\ifnum\totinter=0\relax%
\else
\path[name intersections={of=line1 and line2,by={int}}];
  \draw[,draw,->,red] ([xshift=2pt]c.north east) -- +(0pt,23pt) -| ([yshift=3pt]int) arc(90:-90:2.5pt) -- ([xshift=2pt]d.north east);
\fi
\end{tikzpicture}


\end{document}

Answer 1