[Tex/LaTex] How to retrieve current stroke and fill color in PGF/TikZ

colortikz-pgf

I am defining a shape which can be drawn in normal or inverted mode. In normal mode, the border lines and inner lines are drawn with the current stoke color, while the shape is filled with the current fill color. In inverted mode, the border lines is still drawn with the current stoke color, but the shape is filled with the current stroke color and inner lines are drawn with the current fill color.

Here is a MWE:

\documentclass[varwidth,border=50]{standalone}

\usepackage{tikz}

\makeatother

\pgfkeys{%
  /pgf/invert/.initial=no,%
  /pgf/invert/.default=yes,%
}

\pgfdeclareshape{test}{%
  \inheritsavedanchors[from=circle]%
  \inheritanchorborder[from=circle]%
  \inheritanchor[from=circle]{center}%
  %
  \backgroundpath{%
    \pgfpathcircle{\pgfpointorigin}{5em}%
  }%
  %
  \beforebackgroundpath{%
    %\def\strokecolor{\string\color@pgfstrokecolor}%
    %\def\fillcolor{\string\color@pgffillcolor}%
    %\global\let\strokecolor\csname\string\color@pgfstrokecolor\endcsname%
    %\global\let\fillcolor\csname\string\color@pgffillcolor\endcsname%
    \def\borderColor{\strokecolor}%
    \ifnum\pdfstrcmp{\pgfkeysvalueof{/pgf/invert}}{no}=0%
      \def\fillColor{\fillcolor}%
      \def\innerColor{\strokecolor}%
    \else%
      \def\fillColor{\strokecolor}%
      \def\innerColor{\fillcolor}%
    \fi%
    \pgfsetlinewidth{.5em}%
    \pgfsetstrokecolor{\borderColor}%
    \pgfsetfillcolor{\fillColor}%
    \pgfpathcircle{\pgfpointorigin}{5em}%
    \pgfusepath{fill,stroke}%
    \pgfsetstrokecolor{\innerColor}%
    \pgfmoveto{\pgfpointpolar{135}{4em}}%
    \pgflineto{\pgfpointpolar{-45}{4em}}%
    \pgfusepath{stroke}%
  }%
}

\makeatletter

\begin{document}

  \begin{tikzpicture}
    % In this MWE, I'll use "\strokecolor" and "\fillcolor" in this example
    % instead of the commands I'm looking for to retrieve the current stroke
    % and fill colors

    \begin{scope}[draw=black, fill=white]
      \def\strokecolor{black}
      \def\fillcolor{white}

      \node[test] at (0em, 0em) {};
      \node[test, invert] at (12em, 0em) {};
    \end{scope}

    \begin{scope}[draw=blue, fill=red]
      \def\strokecolor{blue}
      \def\fillcolor{red}

      \node[test] at (0em, 12em) {};
      \node[test, invert] at (12em, 12em) {};
    \end{scope}
  \end{tikzpicture}

\end{document}

Here is the intended result:

I tried to use the "\color@pgfstrokecolor" and "\color@pgffillcolor". However, I then get the following error:

! Package xcolor Error: Undefined color `\color@pgfstrokecolor'.

How can I retrieve the current stroke and fill colors in a PGF shape declaration ?

Best Answer

I used percusse's trick in the answer at How to save the current color in PGF/TikZ?.

Note also that the OP wrongly reversed the sense of \makeatletter and \makeatother which would never allow a solution, until corrected.

\documentclass[varwidth,border=50]{standalone}
\usepackage{tikz}
\makeatletter
\tikzset{%
  get stroke color/.code={%
    \expandafter\global% Jump over, now we have \global
    \expandafter\let% Jump over now we have \global\let
    \expandafter\pgfsavedstrokecolor% Jump we have \global\let\pgf...
    \csname\string\color@pgfstrokecolor\endcsname% Finally expand this and put it at the end 
    },                                           % \global\let\pgf...{} in expanded form 
  restore stroke color/.code={\pgf@setstrokecolor#1},
  get fill color/.code={%
    \expandafter\global% Jump over, now we have \global
    \expandafter\let% Jump over now we have \global\let
    \expandafter\pgfsavedfillcolor% Jump we have \global\let\pgf...
    \csname\string\color@pgffillcolor\endcsname% Finally expand this and put it at the end 
    },                                           % \global\let\pgf...{} in expanded form 
  restore fill color/.code={\pgf@setfillcolor#1},
}

\pgfkeys{%
  /pgf/invert/.initial=no,%
  /pgf/invert/.default=yes,%
}

\pgfdeclareshape{test}{%
  \inheritsavedanchors[from=circle]%
  \inheritanchorborder[from=circle]%
  \inheritanchor[from=circle]{center}%
  %
  \backgroundpath{%
    \pgfpathcircle{\pgfpointorigin}{5em}%
  }%
  %
  \beforebackgroundpath{%
    \def\borderColor{\strokecolor}%
    \ifnum\pdfstrcmp{\pgfkeysvalueof{/pgf/invert}}{no}=0%
%      \tikzset{restore fill color/.expand once=\pgfsavedfillcolor}
%      \tikzset{restore stroke color/.expand once=\pgfsavedstrokecolor}
    \else%
      \tikzset{restore stroke color/.expand once=\pgfsavedstrokecolor}
      \tikzset{restore fill color/.expand once=\pgfsavedstrokecolor}
    \fi%
    \pgfsetlinewidth{.5em}%
    \pgfpathcircle{\pgfpointorigin}{5em}%
    \pgfusepath{fill,stroke}%
    \ifnum\pdfstrcmp{\pgfkeysvalueof{/pgf/invert}}{no}=0%
%      \tikzset{restore stroke color/.expand once=\pgfsavedstrokecolor}
    \else%
      \tikzset{restore stroke color/.expand once=\pgfsavedfillcolor}
    \fi%
    \pgfmoveto{\pgfpointpolar{135}{4em}}%
    \pgflineto{\pgfpointpolar{-45}{4em}}%
    \pgfusepath{stroke}%
  }%
}
\makeatother
\begin{document}

  \begin{tikzpicture}
    \begin{scope}[draw=black, fill=white]
      \tikzset{get stroke color}
      \tikzset{get fill color}
      \node[test] at (0em, 0em) {};
      \node[test, invert] at (12em, 0em) {};
    \end{scope}

    \begin{scope}[draw=blue, fill=red]
      \tikzset{get stroke color}
      \tikzset{get fill color}
      \node[test] at (0em, 12em) {};
      \node[test, invert] at (12em, 12em) {};
    \end{scope}
  \end{tikzpicture}
\end{document}

Related Solutions

[Tex/LaTex] Tikz/pgf half-arrow stroke always down/left

You could try a decoration which provides \pgfdecoratedangle (for straight lines this gives angle of the line) and use this to apply the appropriate arrow:

\documentclass[tikz,border=5]{standalone}
\usetikzlibrary{decorations.pathreplacing,arrows.meta}
\tikzset{barbs/.style={
  decoration={show path construction,
    lineto code={
    \draw 
      \pgfextra{%      
        \pgfmathparse{int(\pgfdecoratedangle/90)}% Possibly check for -ve values.
        \ifcase\pgfmathresult
          \tikzset{-{Straight Barb[right]}}
        \or
          \tikzset{-{Straight Barb[left]}}
        \or
          \tikzset{-{Straight Barb[left]}}
        \else
          \tikzset{-{Straight Barb[right]}}
        \fi
      }  (\tikzinputsegmentfirst) -- (\tikzinputsegmentlast);
    }
  },
  decorate
}}
\begin{document}
\begin{tikzpicture}
\node (o) {o};
\foreach \l [count=\i from 0] in {a,...,d}
   \node (\l) at (\i*90:1) {\l};

\foreach \l in {a,...,d}
  \draw [barbs] (\l) -- (o);
\end{tikzpicture}
\end{document}

enter image description here

[Tex/LaTex] How to draw points in TikZ

Method I (using node)

\tikzset{
  every point/.style = {circle, inner sep={.75\pgflinewidth}, opacity=1, draw, solid, fill=white},
  point/.style={insert path={node[every point, #1]{}}}, point/.default={},
  point name/.style = {insert path={coordinate (#1)}},
}

and some extra stuff :

\tikzset{
  colored point/.style = {point={fill=#1}},
  inherit/.style = {point/.style={insert path={node[circle, inner sep={.75\pgflinewidth}, draw, fill, #1]{}}}}
}

Satisfies 1.
Satisfies 2 with styling like this [point={fill=red, very thick}]
Partially satisfies 3. I don't know how to define draw opacity=inherit or fill=inherit. I define new style inherit which will redefine the entire point by removing the opacity=1 and fill=white, but this is ugly ;).
Partially satisfy 4 : you can use point name=A. I would like to be able to use quotes for saying something like [point={red, "A"}] but I don't know how to do this.
Almost satisfy 5 : we can put [point] almost anywhere, like (A) [point], or node[point, above]{A}, or coordinate[point](A). But can't be used with \coordinate at or \node at (except if you repeat yourself like this \coordinate (A) at (1,1) (A) [point];)
FAILS on 6. I know that there is a hacky solution to put node on layer, but this is in contradiction with 7).
Satisfies 7.

The full code of all tests and the result

\documentclass[varwidth,border=50]{standalone}
\usepackage{tikz}

% not clear how to use layers with this method
\pgfdeclarelayer{background}
\pgfdeclarelayer{foreground}
\pgfsetlayers{background,main,foreground}

\tikzset{
  every point/.style = {circle, inner sep={.75\pgflinewidth}, opacity=1, draw, solid, fill=white},
  point/.style={insert path={node[every point, #1]{}}}, point/.default={},
  colored point/.style = {point={fill=#1}},
  point name/.style = {insert path={coordinate (#1)}},
  inherit/.style = {point/.style={insert path={node[circle, inner sep={.75\pgflinewidth}, draw, fill, #1]{}}}}
}

\begin{document}
  \begin{itemize}

    % ---------------------------------
    \item Test 1 : ok.\\[1em]
    \begin{tikzpicture}
      \foreach[count=\i] \w in {ultra thin, thin, ultra thick} {
      \draw[yshift=-\i em, \w] (0,0) -- (.5,0) [point] -- (1,0);
      }
      \foreach[count=\i] \s in {.2, .5, 1} {
      \draw[xshift=1.5cm, yshift=-\i em, scale=\s] (0,0) -- (.5,0) [point] -- (1,0);
      }
    \end{tikzpicture}

    % ---------------------------------
    \item Test 2 : ok.

    % ---------------------------------
    \item Test 3 : partialy ok, there is no good \texttt{inherit}.\\
    \begin{tikzpicture}[scale=2, very thick]
      \filldraw[draw opacity=.5, draw=red, fill opacity=.3, densely dotted]
        (0,0) [point] -- (.5,0) [point={ultra thick, fill=green}] -- (.5,.5) [inherit, point] -- cycle;
    \end{tikzpicture}

    % ---------------------------------
    \item Test 4 : almost ok (using \texttt{point name})\\
    \begin{tikzpicture}
      \draw[very thick] (0,1) [point] -- (1,0) [point={thick, fill=green, point name=A}];
      \draw[ultra thick, purple] (0,0) [point] -- (A);
    \end{tikzpicture}

    % ---------------------------------
    \item Test 5 : almost ok.

    % ---------------------------------
    \item Test 6 : fails ! (visible in test 4 too)\\
    \begin{tikzpicture}
      \coordinate (A) at (0,1) (A) node[point=ultra thick, left] {A};
      \coordinate (B) at (1,0) (B) [thick, point];
      \draw (A) -- (B);
    \end{tikzpicture}

  \end{itemize}
\end{document}

enter image description here

Method II (using pic)

\pgfdeclarelayer{background}
\pgfdeclarelayer{foreground}
\pgfsetlayers{background,main,foreground}

\tikzset{
  every point/.style = {radius={\pgflinewidth}, opacity=1, draw, solid, fill=white},
  pt/.pic = {
    \begin{pgfonlayer}{foreground}
      \path[every point, #1] circle;
    \end{pgfonlayer}
  },
  point/.style={insert path={pic{pt={#1}}}}, point/.default={},
  point name/.style = {insert path={coordinate (#1)}}
}

FAILS on 1. I don't know how to inherit styles from path to pic. Is there some style like current path style ?
Satisfies 2. Same as method I.
FAILS on 3. We can style as in method I, but because (1) fails, (3) fails.
Partially satisfies 4. Same as method I.
FAILS on 5 : as there is a bug in 'pic' we can't use node after it in PGF 3.0. When this bug will be fixed, this method will be equivalent to the first one at this test.
Satisfies 6. This is the main interest of this method.
Satisfies 7.

The full code of all tests and the result

\documentclass[varwidth,border=50]{standalone}
\usepackage{tikz}

\pgfdeclarelayer{background}
\pgfdeclarelayer{foreground}
\pgfsetlayers{background,main,foreground}

\tikzset{
  every point/.style = {radius={\pgflinewidth}, opacity=1, draw, solid, fill=white},
  pt/.pic = {
    \begin{pgfonlayer}{foreground}
      \path[every point, #1] circle;
    \end{pgfonlayer}
  },
  point/.style={insert path={pic{pt={#1}}}}, point/.default={},
  colored point/.style = {point={fill=#1}},
  point name/.style = {insert path={coordinate (#1)}}
}

\begin{document}
\begin{itemize}
\item Test 1 : fails for sizing from path width, scale is ok.\\[1em]
\begin{tikzpicture}
  \foreach[count=\i] \w in {ultra thin, thin, ultra thick} {
  \draw[yshift=-\i em, \w] (0,0) -- (.5,0) [point] -- (1,0);
  }
  \foreach[count=\i] \s in {.2, .5, 1} {
  \draw[xshift=1.5cm, yshift=-\i em, scale=\s] (0,0) -- (.5,0) [point] -- (1,0);
  }
\end{tikzpicture}

\item Test 2 : partialy ok, there is no \texttt{inherit} (at all).

\item Test 3 : fails ! Can't inherit style from path.\\
\begin{tikzpicture}[scale=2, very thick, densely dotted]
  \filldraw[draw opacity=.5, draw=red, fill opacity=.3]
    (0,0) [point] -- (.5,0) [point={ultra thick, fill=green}] -- (.5,.5) [point] -- cycle;
\end{tikzpicture}

\item Test 4 : almost ok (using \texttt{point name})\\
\begin{tikzpicture}
  \draw[very thick] (0,1) [point] -- (1,0) [point={thick, fill=green, point name=A}];
  \draw[ultra thick, purple] (0,0) [point] -- (A);
\end{tikzpicture}

\item Test 5 : fails ! (can't put node after [point] )

\item Test 6 : ok.\\
\begin{tikzpicture}
  \path (0,1) node[left] {A} coordinate (A) [point=ultra thick];
  \coordinate (B) at (1,0) (B) [thick, point];
  \draw (A) -- (B);
\end{tikzpicture}
\end{itemize}
\end{document}

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] Tikz/pgf half-arrow stroke always down/left

[Tex/LaTex] How to draw points in TikZ

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