\pic 不带命名坐标

Question

是否可以使用 tikz 中的角度库提供的 \pic 命令，而不使用坐标？
如果我使用类似的东西，它可以正常工作。

\begin{tikzpicture}
    \coordinate (A) at (0,0);
    \coordinate (B) at (0,5);
    \coordinate (C) at (5,0);

    \node [left] at (A) {$A$};
    \node [left] at (B) {$B$};
    \node [right] at (C) {$C$};

    \draw (A) -- (B) -- (C);

    \pic [draw] {angle = A--B--C};
\end{tikzpicture}

但是，如果我使用这个，

\begin{tikzpicture}
    \coordinate (A) at (0,0);
    \coordinate (B) at (0,5);
    \coordinate (C) at (5,0);

    \node [left] at (A) {$A$};
    \node [left] at (B) {$B$};
    \node [right] at (C) {$C$};

    \draw (A) -- (B) -- (C);

    \pic [draw] {angle = (0,0)--(0,5)--(5,0)};
\end{tikzpicture}

这是行不通的。

如果我能使用这个，那就太好了，这样我就可以使用点而不用命名它们。

Answer 1

angle需要名称，而不是坐标。名称参数直接解析为 \pgfpointanchor，来自tikzlibraryangles.code.tex：

\def\tikz@lib@angle@parse#1--#2--#3\pgf@stop{%
  % ...
  \pgf@process{\pgfpointanchor{#2}{center}}%
  \pgf@xa=\pgf@x%
  \pgf@ya=\pgf@y%
  \pgf@process{\pgfpointanchor{#1}{center}}%
  \pgf@xb=\pgf@x%
  \pgf@yb=\pgf@y%
  \pgf@process{\pgfpointanchor{#3}{center}}%
  % ...
}

\pgfpointanchor期望节点名称作为第一个参数。

因此，库也需要大量修补才能支持坐标规范。以下示例修补了 libary angles。 的参数angle需要用花括号括起来，以便向解析器隐藏逗号pgfkeys：

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

\usepackage{etoolbox}
\makeatletter
% Helper macros
\def\tikz@lib@angle@def@coord#1{%
  \ifx(#1\relax
    \coordinate(tikz@lib@angle@tmp)at#1;%
  \else
    \coordinate(tikz@lib@angle@tmp)at(#1);%
  \fi
}
\def\tikz@lib@angle@coord#1{%
  \pgf@process{% 
    \ifx(#1\relax
      \tikz@scan@one@point\@firstofone#1\relax
    \else
      \pgfpointanchor{#1}{center}%
    \fi
  }%
}
% Patching
\patchcmd\tikz@lib@angle@background{#2}{tikz@lib@angle@tmp}{}{%
  \errmessage{Cannot patch \string\tikz@lib@angle@background}%
}
\patchcmd\tikz@lib@angle@foreground{#2}{tikz@lib@angle@tmp}{}{%
  \errmessage{Cannot patch \string\tikz@lib@angle@foreground}%
}
\pretocmd\tikz@lib@angle@background{\tikz@lib@angle@def@coord{#2}}{}{%
  \errmessage{Cannot prepend \string\tikz@lib@angle@background}%
}
\pretocmd\tikz@lib@angle@foreground{\tikz@lib@angle@def@coord{#2}}{}{%
  \errmessage{Cannot prepend \string\tikz@lib@angle@foreground}%
}
\patchcmd\tikz@lib@angle@parse{%
  \pgf@process{\pgfpointanchor{#2}{center}}%
}{%
  \tikz@lib@angle@coord{#2}%
}{}{%
  \errmessage{Cannot patch \string\tikz@lib@angle@parse}%
}
\patchcmd\tikz@lib@angle@parse{%
  \pgf@process{\pgfpointanchor{#1}{center}}%
}{%
  \tikz@lib@angle@coord{#1}%
}{}{%
  \errmessage{Cannot patch \string\tikz@lib@angle@parse}%
}
\patchcmd\tikz@lib@angle@parse{%
  \pgf@process{\pgfpointanchor{#3}{center}}%
}{%
  \tikz@lib@angle@coord{#3}%
}{}{%
  \errmessage{Cannot patch \string\tikz@lib@angle@parse}%
}
% Better support for the comma in the value for angle:
\tikzset{
  pics/angle/.style = {
    setup code  = {\tikz@lib@angle@parse#1\pgf@stop},
    background code = {\tikz@lib@angle@background#1\pgf@stop},
    foreground code = {\tikz@lib@angle@foreground#1\pgf@stop},
  },
}
\makeatother

\begin{document}
\begin{tikzpicture}
    \coordinate (A) at (0,0);
    \coordinate (B) at (0,5);
    \coordinate (C) at (5,0);

    \node [left] at (A) {$A$};
    \node [left] at (B) {$B$};
    \node [right] at (C) {$C$};

    \draw (A) -- (B) -- (C);

    % \pic [draw] {angle=A--B--C};
    \pic [draw] {angle={(0,0)--(0,5)--(5,0)}};
\end{tikzpicture}
\end{document}

Answer 2

您还可以通过插入angle自定义来采用另一种方式pic。

\documentclass[tikz]{standalone}
\usetikzlibrary{angles}

\makeatletter
\tikzset{pics/anglecoords/.style = {
 setup code  = {
  \def\minicoordparser##1--##2--##3\pgf@stop{
    \coordinate (A-a) at ##1;\coordinate (B-b) at ##2;\coordinate (C-c) at ##3;
  }
  \minicoordparser#1\pgf@stop
  \tikz@lib@angle@parse{A-a}--{B-b}--{C-c}\pgf@stop
},
background code = \tikz@lib@angle@background{A-a}--{B-b}--{C-c}\pgf@stop,
foreground code = \tikz@lib@angle@foreground{A-a}--{B-b}--{C-c}\pgf@stop,  
  },
}
\makeatother

\begin{document}
\begin{tikzpicture}[]
\draw (0,0) --(0,5) --(5,0) -- cycle;
\pic[draw]{anglecoords = {(0,0)--(0,5)--(5,0)}};
\pic[draw,fill=yellow]{anglecoords = {(5,0)--(0,0)--(0,5)}};
\end{tikzpicture}
\end{document}