% Copyright 2022 by Qrrbrbirlbel
%
% This file may be distributed and/or modified
%
% 1. under the LaTeX Project Public License and/or
% 2. under the GNU Free Documentation License.
%
\tikzset{
  arc to/.code=\pgfqkeys{/tikz/arc to}{#1},
  arc to={
    counter clockwise/.code=\pgfkeyssetvalue{/tikz/arc to/ccw flag}{1},
    clockwise/.code=\pgfkeyssetvalue{/tikz/arc to/ccw flag}{0},
    x radius/.code=\pgfkeyssetvalue{/tikz/x radius}{#1},
    y radius/.code=\pgfkeyssetvalue{/tikz/y radius}{#1},
    radius/.code=\pgfkeyssetvalue{/tikz/x radius}{#1}\pgfkeyssetvalue{/tikz/y radius}{#1},
    large/.code=\pgfkeyssetvalue{/tikz/arc to/large flag}{1},
    small/.code=\pgfkeyssetvalue{/tikz/arc to/large flag}{0},
    % defaults
    rotate/.initial=0, counter clockwise, small,
    counter clockwise/.value forbidden,
    clockwise/.value forbidden,
    large/.value forbidden,
    small/.value forbidden}}
\def\tikz@arcA rc{\pgfutil@ifnextchar t%
  {\tikz@flush@moveto\expandafter\expandafter\expandafter\tikz@arcB@cont\expandafter\pgfutil@gobble\pgfutil@gobble}
  {\tikz@flush@moveto\tikz@arc@cont}}
\def\tikz@arcB@cont{%
  \pgfutil@ifnextchar[\tikz@@do@arcB{
    \advance\tikz@expandcount by -10\relax% go down quickly
    \ifnum\tikz@expandcount<0\relax%
      \def\@next{\tikz@@do@arcB[]}%
    \else%
      \def\@next{\expandafter\tikz@arcB@cont}%
    \fi%
    \@next}}%
\def\tikz@@do@arcB[#1]{%
  \def\tikz@arcB@options{#1}%
  \tikz@do@@arcB}
\def\tikz@do@@arcB{%
  \pgfutil@ifnextchar n{\tikz@collect@label@onpath\tikz@do@@arcB}
    {\pgfutil@ifnextchar c{\tikz@collect@coordinate@onpath\tikz@do@@arcB}
      {\pgfutil@ifnextchar p{\tikz@collect@pic@onpath\tikz@do@@arcB}
        {\tikz@scan@one@point\tikz@do@arcB}}}}

\def\tikz@do@arcB#1{%
  \edef\tikz@timer@start{\noexpand\pgfqpoint{\the\tikz@lastx}{\the\tikz@lasty}}
  \tikz@make@last@position{#1}%
  \edef\tikz@timer@end{\noexpand\pgfqpoint{\the\tikz@lastx}{\the\tikz@lasty}}%
  \iftikz@shapeborder
    \edef\tikz@moveto@waiting{\tikz@shapeborder@name}%
  \fi
  \begingroup
    \tikzset{every arc/.try,every arc to/.try,arc to/.expand once=\tikz@arcB@options}%
    \pgfmathsetmacro\tikz@arc@x{\pgfkeysvalueof{/tikz/x radius}}%
    \ifpgfmathunitsdeclared
      \pgfmathsetmacro\tikz@arc@y{\pgfkeysvalueof{/tikz/y radius}}%
      \ifpgfmathunitsdeclared
        \pgfpatharcto{\tikz@arc@x pt}{\tikz@arc@y pt}
                     {\pgfkeysvalueof{/tikz/arc to/rotate}}{\pgfkeysvalueof{/tikz/arc to/large flag}}
                     {\pgfkeysvalueof{/tikz/arc to/ccw flag}}{#1}%
      \else
        \tikzerror{You cannot mix dimensions and dimension values in an arc}%
      \fi
    \else
      \pgfmathsetmacro\tikz@arc@y{\pgfkeysvalueof{/tikz/y radius}}%
      \ifpgfmathunitsdeclared
        \tikzerror{You cannot mix dimensions and dimension values in an arc}%
      \else
        \pgf@process{\pgfpointxy{\tikz@arc@x}{0}}%
        \pgfmathveclen@{\pgf@sys@tonumber\pgf@x}{\pgf@sys@tonumber\pgf@y}%
        \let\tikz@arc@x\pgfmathresult
        \pgf@process{\pgfpointxy{0}{\tikz@arc@y}}%
        \pgfmathveclen@{\pgf@sys@tonumber\pgf@x}{\pgf@sys@tonumber\pgf@y}%
        \let\tikz@arc@y\pgfmathresult
        \pgfpatharcto{+\tikz@arc@x pt}{+\tikz@arc@y pt}
                     {\pgfkeysvalueof{/tikz/arc to/rotate}}{\pgfkeysvalueof{/tikz/arc to/large flag}}
                     {\pgfkeysvalueof{/tikz/arc to/ccw flag}}{#1}%
      \fi
    \fi
  \endgroup
  % check whether \pgf@marshall starts with \pgfpathlineto
  \pgfutil@ifxempty\pgf@marshal{}{%
    \edef\tikz@temp{\expandafter\expandafter\expandafter\noexpand\expandafter\pgfutil@firstgobblerest\pgf@marshal\relax}%
    \expandafter\let\expandafter\tikz@temp\tikz@temp
    \pgfutil@ifx\tikz@temp\pgfpathlineto{}{%
      % getting rid of \pgfpatharcaxes inside \pgf@marshal
      \expandafter\expandafter\expandafter\def\expandafter\expandafter\expandafter\pgf@marshal
      \expandafter\expandafter\expandafter{\expandafter\pgfutil@gobble\pgf@marshal}%
      % extracting the other four values needed for the timer
      \edef\tikz@timer@start@angle{\expandafter\pgfutil@firstoffour\pgf@marshal}%
      \edef\tikz@timer@end@angle{\expandafter\pgfutil@secondoffour\pgf@marshal}%
      \pgfextract@process\tikz@timer@zero@axis{\expandafter\pgfutil@thirdoffour\pgf@marshal}%
      \pgfextract@process\tikz@timer@ninety@axis{\expandafter\pgfutil@fourthoffour\pgf@marshal}%
      %
      \let\tikz@timer=\tikz@timer@arc
    }%
  }%
  \tikz@scan@next@command
}
\def\pgfutil@firstoffour#1#2#3#4{#1}
\def\pgfutil@secondoffour#1#2#3#4{#2}
\def\pgfutil@thirdoffour#1#2#3#4{#3}
\def\pgfutil@fourthoffour#1#2#3#4{#4}
\def\pgfutil@firstgobblerest#1#2\relax{#1}