Arbitrary container around a tikzcd diagram

Question

I wish to draw a picture like this with an arbitrary shape around a few points with arrows between them. I am using the circle command in tikzpicture but the result is very different. Could someone guide me?

Answer 1

This is a job for ... tikzmark!

Basic idea: make your tikzcd as usual. But place a tikzmark in the middle. I placed one on an invisible (phantom) arrow from a to f and called it middleL.

Then leave some space and make your tikzpicture as usual. But place a tikzmark in the middle. I put one at (0,0) and called it middleR.

Then start a new tikzpicture using \begin{tikzpicture}[remember picture, overlay]. Draw big puffy cloud nodes (using shapes.symbols) and place them at coordinates using the syntax (pic cs:middleL) and (pic cs:middleR) (which is how to refer to previous tikzmarks). Then just treat them like ordinary nodes—label them and \draw an arrow between them with bend left.

Note: You must compile twice when using tikzmark.

Here is the code:

\documentclass{article}

\usepackage{tikz-cd}
\usetikzlibrary{tikzmark,shapes.geometric,shapes.symbols}
\tikzset{elnode/.style={draw, ellipse, dotted, minimum height=1cm, label distance=-2mm},
    cloudnode/.style={draw, dashed, black!80, inner sep=1.75cm, cloud, cloud puffs=20, cloud puff arc=120}}

\begin{document}

\begin{tikzcd}[arrows={-latex, outer sep=-1.5pt},row sep=1cm, column sep=2cm]
 & b\arrow[dd,bend left=20,"f"{name=F}]\\
a\arrow[ur,bend left,"g_1"]\arrow[ur,"g_2"]\arrow[ur,bend right,"g_3"]
    \arrow[dr,bend left=20,"h_1"']\arrow[dr,bend right=20,"h_2"'] 
    \arrow[to=F,phantom,"{}\tikzmark{middleL}"] \\
 & c
\end{tikzcd}\hspace{3.5cm}
\begin{tikzpicture}[baseline,font=\small]
\node[elnode,label={above:$C(a,b)$}] at(0,1){$g_1\quad g_2\quad g_3$};
\node[elnode,label={below:$C(a,c)$}] at (0,-1){$h_1\quad h_2$};
\node at (0,0){\tikzmark{middleR}{}};
\end{tikzpicture}

\begin{tikzpicture}[remember picture, overlay]
\node[cloudnode, label={above:$C$}](lft) at (pic cs:middleL){};
\node[cloudnode, label={above:\textbf{Set}}](rgt) at (pic cs:middleR){};
\draw[-latex](lft)to[bend left]node[above]{$C(a,-)$}(rgt);
\end{tikzpicture}

\end{document}