Tikz : Creation of complex custom node

Question

I've come again to pic your interesting brains.

I am trying to make a custom node with a drawing I've made

    \documentclass[tikz, margin=3mm]{standalone}
    \usepackage[utf8]{inputenc}
    \usepackage{pgfplots,tikz}
    \pgfplotsset{compat=1.16}
    \usetikzlibrary{calc}
    
    \tikzset{
      pics/mynodeB/.style={
         code={
            \draw[fill] (0,0.5) circle (1cm);
            \draw[line width=4pt] (0,0) circle (2.2cm) ;
            \pgfmathsetmacro{\AngleA}{52.5}
            \draw[fill] (0,-2) arc (-90:-37.8:2cm) arc (29:66.2:1.8cm) arc (-\AngleA:{-180+\AngleA}:1.2cm)  arc ({180-66.2}:{180-29}:1.8cm) arc ({-180+37.8}:-90:2cm) ;
         }
      },
        cross/.style={path picture={
            \draw[black] let
              \p1 = (path picture bounding box.south),
              \p2 = (path picture bounding box.north),
              \n1 = {veclen((\x2-\x1),(\y2-\y1))}
              in ($(path picture bounding box.south east)!0.5!(path picture bounding box.north west)$) circle (1cm);  % Change is to be made here
        }},
    }
    
    
    \begin{document}
    
      \begin{tikzpicture}
            \draw[fill] (0,0.5) circle (1cm);
            \draw[line width=4pt] (0,0) circle (2.2cm) ;
            \pgfmathsetmacro{\AngleA}{52.5}
            \draw[fill] (0,-2) arc (-90:-37.8:2cm) arc (29:66.2:1.8cm) arc (-\AngleA:{-180+\AngleA}:1.2cm)  arc ({180-66.2}:{180-29}:1.8cm) arc ({-180+37.8}:-90:2cm) ;
            
          \pic[red] at (5,0) {mynodeB};
          \node[cross,minimum size=2cm] at (10,0) {};
      \end{tikzpicture}
    
    \end{document}

It gives this

The first is the drawing I'm trying to use. You can see some weird numerical values because I had drawn it using filled circles and some clipping/reversed clipping but it was not working well when I tried to turn it into a node so I approximated the shape with arcs.

The red one is the same drawing done with a "pic" I defined (I don't really know what a pic is, I used a code I found here...). The problem is that a pic is not a node, and I can't use my usual commands to play with it.

The circle on the right is based on a simpler custom node I had made previously. I am trying to make the same drawing than before, but I must not use fixed length (or the shape won't be resized with the node). You can see I have tried in cross/.style evaluating the length \n1 of the node, but if I put \n1 where 1cm is, the circle disappears.

Do you have ideas ?

Answer 1

Quite hard to understand what you're looking for, but here's an attempt to answer. Pics are a way to save drawings and be able to reuse them. Hence, you can scale them too (like I did in violet).

A way to name a pic as a node is to give it the parameter local bounding box=A, for example. Then you can use A like a node, especially to place another one next to it, like I did (with the positioning library).

\documentclass[tikz,border=3.14mm]{standalone}
   \usetikzlibrary{positioning}
    
\tikzset{
      mypic/.pic={
            \filldraw (0,0.5) circle (1cm);
            \draw[line width=4pt] (0,0) circle (2.2cm) ;
            \pgfmathsetmacro{\AngleA}{52.5}
            \filldraw (0,-2) arc (-90:-37.8:2cm) arc (29:66.2:1.8cm) arc (-\AngleA:{-180+\AngleA}:1.2cm)  arc ({180-66.2}:{180-29}:1.8cm) arc ({-180+37.8}:-90:2cm) ;
      }
    }
   
    
\begin{document}
    
    \begin{tikzpicture}[on grid]
        \pic[red,local bounding box=A] {mypic};
        \pic[violet,scale=0.5,right=4 cm of A] {mypic};
    \end{tikzpicture}
    
\end{document}

Answer 2

You were almost there. You only need to introduce a scale factor that allows you to scale the pic without resorting to the scale key because otherwise you may be in trouble if you use the scale key on the node.

\documentclass[tikz, margin=3mm]{standalone}
\usetikzlibrary{calc}
\tikzset{
  pics/mynodeB/.style={
     code={
        \draw[fill] (0,0.5*#1) circle[radius=#1*1cm];
        \draw[line width=#1*4pt] (0,0) circle[radius=#1*2.2cm];
        \pgfmathsetmacro{\AngleA}{52.5}
        \draw[fill] (0,-2*#1) arc[start angle=-90,end angle=-37.8,radius=#1*2cm] 
         arc[start angle=29,end angle=66.2,radius=#1*1.8cm] 
         arc[start angle=-\AngleA,end angle={-180+\AngleA},radius=#1*1.2cm]  
         arc[start angle={180-66.2},end angle={180-29},radius=#1*1.8cm] 
         arc[start angle={-180+37.8},end angle=-90,radius=#1*2cm];
     }
  },pics/mynodeB/.default=1,
    cross/.style={circle,path picture={
        \path let
          \p1 = (path picture bounding box.south west),
          \p2 = (path picture bounding box.north east),
          \n1 = {scalar(veclen(\x2-\x1,\y2-\y1)/4.4cm/sqrt(2))}
          in (path picture bounding box.center)
          pic{mynodeB=\n1};
    }},
}

\begin{document}
\begin{tikzpicture}
    \draw[fill] (0,0.5) circle (1cm);
    \draw[line width=4pt] (0,0) circle (2.2cm) ;
    \pgfmathsetmacro{\AngleA}{52.5}
    \draw[fill] (0,-2) arc (-90:-37.8:2cm) arc (29:66.2:1.8cm) arc (-\AngleA:{-180+\AngleA}:1.2cm)  arc ({180-66.2}:{180-29}:1.8cm) arc ({-180+37.8}:-90:2cm) ;
    \pic[red] at (5,0) {mynodeB};
    \node[cross,minimum size=2cm] (A) at (10,0) {};
    \node[cross,minimum size=2cm,blue] (B) at (14,0) {};
    \draw[thick,orange] (A.45) to[out=45,in=-135] (B.-135);
\end{tikzpicture}
\end{document}

Answer 3

Why not abuse a little bit from path picture? If the node is a circle with minimum size, it's possible measure this size and draw a figure proportional to it.

Following code need some adjustments, but it shows the idea

\documentclass[tikz, margin=3mm]{standalone}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{calc}
    
\tikzset{
    head/.style={circle, draw, path picture={%
        \fill let \p1=($(path picture bounding box.north)-(path picture bounding box.south)$), \n1={veclen(\p1)} in ([yshift=.1*\n1]path picture bounding box.center) circle(0.22*\n1);
        \fill let \p1=($(path picture bounding box.north)-(path picture bounding box.south)$), \n1={veclen(\p1)} in 
        ([shift={(45:.25*\n1)}]path picture bounding box.-135) to[out=-45, in=-135]
        ([shift={(135:.25*\n1)}]path picture bounding box.-45) to[bend right]
        ([shift={(135:.5*\n1)}]path picture bounding box.-45) to[out=-135, in=-45]
        ([shift={(45:.5*\n1)}]path picture bounding box.-135) to[bend right] cycle
        ;
    }}
}

\begin{document}
    
\begin{tikzpicture}

\node[head, minimum size=4cm, draw, blue, line width=1mm] (a) {};

\node[head, minimum size=2cm, draw, green, line width=1mm] at (4,0) (b) {};

\node[head, minimum size=1cm, draw, red] at (4,2) (b) {};

\end{tikzpicture}
    
\end{document}

Update: Reduced code.

Previous code solution can be reduced with the help of Mark Wibrow's "alias" and compacting both fill commands into only one.

\documentclass[tikz, margin=3mm]{standalone}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{calc}
    
\tikzset{
    alias path picture bounding box/.code=\pgfnodealias{#1}{path picture bounding box},
    head/.style={circle, draw, path picture={%
        \tikzset{alias path picture bounding box=@}
        \fill let \p1=($(@.north)-(@.south)$), \n1={veclen(\p1)} in ([yshift=.1*\n1]@.center) circle(0.22*\n1)%;
        ([shift={(45:.25*\n1)}]@.-135) to[out=-45, in=-135]
        ([shift={(135:.25*\n1)}]@.-45) to[bend right]
        ([shift={(135:.5*\n1)}]@.-45) to[out=-135, in=-45]
        ([shift={(45:.5*\n1)}]@.-135) to[bend right] cycle
        ;
    }}
}

\begin{document}
    
\begin{tikzpicture}

\node[head, minimum size=4cm, draw, blue, line width=1mm] (a) {};

\node[head, minimum size=2cm, draw, green, line width=1mm] at (4,0) (b) {};

\node[head, minimum size=1cm, draw, red] at (4,2) (b) {};

\end{tikzpicture}
    
\end{document}