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不太合适：新箭头

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不太合适：新箭头

我发现我无法将装饰应用于使用“to”路径操作绘制的（大多数）曲线。这是一个有效示例：

\documentclass[a4paper, reqno]{amsart}

\usepackage{tikz}
\usetikzlibrary{decorations.markings, topaths}

\makeatletter
\tikzset{nomorepostaction/.code = \let\tikz@postactions\pgfutil@empty}
\makeatother
\tikzset{bigdiagramarrow/.style = {
    decoration = {markings, mark = at position 1 with {\arrow[thick]{latex}}},
    postaction = {nomorepostaction, decorate}
}}

\begin{document}
    \begin{tikzpicture}
        \node [draw] (A) at (0, 0) {$A$};
        \node [draw] (B) at (0, 1) {$B$};
        \node [draw] (C) at (2, 1) {$C$};
        \draw [bigdiagramarrow] (A) -- (B);
        \draw [out = 0, in = 180, bigdiagramarrow] (A) to (C);
    \end{tikzpicture}
\end{document}

以下是我编译后得到的结果：

可以看到，使用路径操作绘制的路径末端会绘制一个箭头--，但是使用路径操作绘制的路径末端却没有绘制箭头to。

奇怪的是，在我遇到此问题的文档中，我发现使用“to”路径操作创建的一些曲线将显示装饰。更准确地说，我实际尝试排版的文档中的 12 条曲线中有 3 条显示了装饰。每次我编译文档时都是这 3 条。我不知道这 3 条与其他曲线有什么不同。

一开始看起来这个问题可能相关，但据我所知，我似乎没有遇到相同的“陷阱”，因为我没有将选项传递给路径to操作而是传递给\draw宏。

注意：nomorepostaction关键来自 Ulrich Schwarz 对这个问题。

答案1

我找到了两种或多或少合适的方法来改变箭头的大小（这不是解决当前实际问题的方法，也就是说at position 1不是计算正确的）：

  • 不太合适： 
    • 新箭头：_latex
    • 新风格arrow line width：长度（新的\pgflinewidth）
    • 并且arrow ultra thin，，arrow very thin…，arrow ultra thick设置arrow line width
  • 更合适： 
    • 重新定义一个宏，本地（！）为箭头设置新的线宽。
    • 新风格arrow line width：因素
    • 并且arrow ultra thin，，arrow very thin…，arrow ultra thick设置arrow line width

（它们甚至可以结合在一起。）

不太合适：新箭头

我选择定义一个_latex与 相同的新箭头，latex只是将其\pgflinewidth替换为\pgflinewidth@arrow。

长度\pgflinewidth@arrow是默认的\pgflinewidth，因此箭头会照常工作，除非arrow line width明确使用任意长度的键。（遗憾的是，thick等等不能使用，但 arrow thick。

可以进行改进的是，人们可以通过找到一个好的钩子在\pgflinewidth本地设置来使用已经存在的箭头而无需进行任何改变。

有许多其他方法来改变箭头大小：是否可以更改 TikZ/PGF 中箭头的大小？

代码

\documentclass[tikz,border=2pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}

\makeatletter
\tikzset{nomorepostaction/.code = \let\tikz@postactions\pgfutil@empty}
\newdimen\pgflinewidth@arrow
\pgfarrowsdeclare{_latex}{_latex}
{
  \pgfutil@tempdima=0.28pt%
  \pgfutil@tempdimb=\pgflinewidth@arrow%
  \ifdim\pgfinnerlinewidth>0pt%
    \pgfmathsetlength\pgfutil@tempdimb{.6\[email protected]*\pgfinnerlinewidth}%
  \fi%
  \advance\pgfutil@tempdima by.3\pgfutil@tempdimb%
  \pgfarrowsleftextend{+-1\pgfutil@tempdima}
  \pgfarrowsrightextend{+9\pgfutil@tempdima}
}
{
  \pgfutil@tempdima=0.28pt%
  \pgfutil@tempdimb=\pgflinewidth@arrow%
  \ifdim\pgfinnerlinewidth>0pt%
    \pgfmathsetlength\pgfutil@tempdimb{.6\[email protected]*\pgfinnerlinewidth}%
  \fi%
  \advance\pgfutil@tempdima by.3\pgfutil@tempdimb%
  \pgfpathmoveto{\pgfqpoint{9\pgfutil@tempdima}{0pt}}
  \pgfpathcurveto
  {\pgfqpoint{6.3333\pgfutil@tempdima}{.5\pgfutil@tempdima}}
  {\pgfqpoint{2\pgfutil@tempdima}{2\pgfutil@tempdima}}
  {\pgfqpoint{-1\pgfutil@tempdima}{3.75\pgfutil@tempdima}}
  \pgfpathlineto{\pgfqpoint{-1\pgfutil@tempdima}{-3.75\pgfutil@tempdima}}
  \pgfpathcurveto
  {\pgfqpoint{2\pgfutil@tempdima}{-2\pgfutil@tempdima}}
  {\pgfqpoint{6.3333\pgfutil@tempdima}{-.5\pgfutil@tempdima}}
  {\pgfqpoint{9\pgfutil@tempdima}{0pt}}
  \pgfusepathqfill
}

\tikzset{
    bigdiagramarrow/.style = {
        -_latex,
        arrow thick
    },
    arrow line width/.code={
        \pgfmathsetlength\pgflinewidth@arrow{#1}
    },
    arrow line width/.initial=\pgflinewidth,
    arrow ultra thin/.style={arrow line width=0.1pt},
    arrow very thin/.style={arrow line width=0.2pt},
    arrow thin/.style={arrow line width=0.4pt},
    arrow semithick/.style={arrow line width=0.6pt},
    arrow thick/.style={arrow line width=0.8pt},
    arrow very thick/.style={arrow line width=1.2pt},
    arrow ultra thick/.style={arrow line width=1.6pt},
}
\makeatother
\begin{document}
    \begin{tikzpicture}
        \node [draw] (A) at (0, 0) {$A$};
        \node [draw] (B) at (0, 1) {$B$};
        \node [draw] (C) at (2, 1) {$C$};
        \draw [bigdiagramarrow] (A) to (B);
        \draw [out = 0, in = 180][bigdiagramarrow] (A) to (C);
    \end{tikzpicture}
\end{document}

输出

在此处输入图片描述

更合适： 

代码

\documentclass[tikz,border=2pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}

\makeatletter
\tikzset{nomorepostaction/.code = \let\tikz@postactions\pgfutil@empty}
\def\pgf@arrowset#1#2{%
  \pgfutil@ifundefined{pgf@arrow@code@#2}
  {\PackageError{pgf}{Arrow #1 type ``#2'' unknown}{}}
  {%
    \edef\pgf@arrow@temp{#2}%
    \ifx\pgf@arrow@temp\pgfutil@empty% ah. clear!
      \expandafter\let\csname pgf@#1arrow\endcsname=\pgfutil@empty%
      \expandafter\let\csname pgf@shorten@#1\endcsname=\pgfutil@empty%
    \else%
      %\pgf@arrow@prepare{#2}%
      \expandafter\def\csname pgf@#1arrow\endcsname{\multiply\pgflinewidth by \pgflinewidth@arrow\relax\pgf@arrow@call{#2}}%
      \expandafter\edef\csname pgf@shorten@#1\endcsname{\multiply\pgflinewidth by \noexpand\pgflinewidth@arrow\relax\expandafter\noexpand\csname pgf@arrow@right@#2\endcsname}%
    \fi%
  }%
}
\tikzset{
    bigdiagramarrow/.style = {
        -latex,
        arrow thick
    },
    arrow line width/.code={
        \pgfmathsetmacro\pgflinewidth@arrow{#1}
    },
    arrow line width=1,
    arrow ultra thin/.style={arrow line width=0.25},
    arrow very thin/.style={arrow line width=0.5},
    arrow thin/.style={arrow line width=1},
    arrow semithick/.style={arrow line width=1.5},
    arrow thick/.style={arrow line width=2},
    arrow very thick/.style={arrow line width=3},
    arrow ultra thick/.style={arrow line width=4},
}
\makeatother
\begin{document}
    \begin{tikzpicture}
        \node [draw] (A) at (0, 0) {$A$};
        \node [draw] (B) at (0, 1) {$B$};
        \node [draw] (C) at (2, 1) {$C$};
        \draw [bigdiagramarrow] (A) to (B);
        \draw [out = 0, in = 180][bigdiagramarrow] (A) to (C);
    \end{tikzpicture}
\end{document}

输出

在此处输入图片描述

答案2

既然有复杂的方法，为什么要采用简单的方法呢？

\documentclass{standalone}
\usepackage{tikz}
\begin{document}
    \begin{tikzpicture}
        \node [draw] (A) at (0, 0) {$A$};
        \node [draw] (B) at (0, 1) {$B$};
        \node [draw] (C) at (2, 1) {$C$};
        \draw [-latex] (A) -- (B);
        \draw [out = 0, in = 180, -latex] (A) to (C);
    \end{tikzpicture}
\end{document}

在此处输入图片描述

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