额外的平行路径和“缩短”

Question

不久前，我偶然发现了一个用 TikZ 绘制平行路径的非常好的解决方案，可以在这里找到：在 TikZ 中绘制额外的平行路径。

shorten >=然而，当我尝试将其用于我的目的时（即与和选项结合使用shorten <=），我发现此解决方案的表现并不像预期的那样。这是一个 MWE：

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.pathmorphing}
\usetikzlibrary{positioning}

\def\pgfdecoratedcontourdistance{0pt}

\pgfkeys{/pgf/decoration/contour distance/.code={%
    \pgfmathparse{#1}%
    \let\pgfdecoratedcontourdistance=\pgfmathresult}%
}

\pgfdeclaredecoration{contour lineto}{start}
{
    \state{start}[next state=draw, width=0pt]{
        \pgfpathmoveto{\pgfpoint{0pt}{\pgfdecoratedcontourdistance}}%
    }
    \state{draw}[next state=draw, width=\pgfdecoratedinputsegmentlength]{       
        \pgfmathparse{-\pgfdecoratedcontourdistance*cot(-\pgfdecoratedangletonextinputsegment/2+90)}%
        \let\shorten=\pgfmathresult%
        \pgfpathlineto{\pgfpoint{\pgfdecoratedinputsegmentlength+\shorten}{\pgfdecoratedcontourdistance}}%  
    }
    \state{final}{
        \pgfpathlineto{\pgfpoint{\pgfdecoratedinputsegmentlength}{\pgfdecoratedcontourdistance}}%
    }   
}

\begin{document}
  \tikzset{
    box/.style={draw=black, fill=blue!20, inner sep=1em},
    arrow/.style={->,draw=black, shorten >=1mm,shorten <=1mm},
    quintuple/.style={
      postaction={decoration={contour lineto, contour distance=-4pt},draw=black, decorate},
      postaction={decoration={contour lineto, contour distance=-2pt},draw=black, decorate},
      postaction={decoration={contour lineto, contour distance=+2pt},draw=black, decorate},
      postaction={decoration={contour lineto, contour distance=+4pt},draw=black, decorate},
    },
  }
  \begin{tikzpicture}
    \node[box] (box1) {Box 1};
    \node[box,above right=of box1] (box2) {Box 2};
    \draw[arrow,quintuple] (box1) |- (box2);
  \end{tikzpicture}
\end{document}

生成的图片如下所示：

箭头末端全都弄乱了，我不明白为什么会这样。有人能提供一个解决方案，让箭头末端看起来漂亮吗（或者至少解释一下这里发生了什么）？

Answer 1

正是final状态把事情搞乱了，但在您的情况下，这种final状态是不需要的，因为您不需要或不希望添加的路径在与基本路径相同的点结束。

只需删除状态声明final，一切就会按我们想要的方式运行：

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.pathmorphing}
\usetikzlibrary{positioning}

\def\pgfdecoratedcontourdistance{0pt}

\pgfkeys{/pgf/decoration/contour distance/.code={%
    \pgfmathparse{#1}%
    \let\pgfdecoratedcontourdistance=\pgfmathresult}%
}

\pgfdeclaredecoration{contour lineto}{start}
{
    \state{start}[next state=draw, width=0pt]{
        \pgfpathmoveto{\pgfpoint{0pt}{\pgfdecoratedcontourdistance}}%
    }
    \state{draw}[next state=draw, width=\pgfdecoratedinputsegmentlength]{       
        \pgfmathparse{-\pgfdecoratedcontourdistance*cot(-\pgfdecoratedangletonextinputsegment/2+90)}%
        \let\shorten=\pgfmathresult%
        \pgfpathlineto{\pgfpoint{\pgfdecoratedinputsegmentlength+\shorten}{\pgfdecoratedcontourdistance}}%  
    }
}

\begin{document}
  \tikzset{
    box/.style={draw=black, fill=blue!20, inner sep=1em},
    arrow/.style={->,draw=black, shorten >=1mm,shorten <=1mm},
    quintuple/.style={
      postaction={decoration={contour lineto, contour distance=-4pt},draw=black, decorate},
      postaction={decoration={contour lineto, contour distance=-2pt},draw=black, decorate},
      postaction={decoration={contour lineto, contour distance=+2pt},draw=black, decorate},
      postaction={decoration={contour lineto, contour distance=+4pt},draw=black, decorate},
    },
  }
  \begin{tikzpicture}
    \node[box] (box1) {Box 1};
    \node[box,above right=of box1] (box2) {Box 2};
    \draw[arrow,quintuple] (box1) |- (box2);
    \draw[arrow,quintuple] (box1) -| (box2);
  \end{tikzpicture}
\end{document}