% English-label smoke: cursor row, operator, meaning box, formula last.
\documentclass[border=8pt]{standalone}
\usepackage[en]{superfig}

\sfsetrole{x}{sfTeal}
\sfsetrole{y}{sfOrange}

\begin{document}
\begin{tikzpicture}
\sfstage{S}{one band}
\sfrow{R1}{12mm}
  \sfnode[role=x]{A}{$A$}{14mm}{10mm}
  \sfop{op}{$\circ$}
  \sfnode[role=y]{B}{$B$}{14mm}{10mm}
\sfrowend
\sflane{R1}
\sfcaption{A}{$A$}{left}
\sfcaption{B}{$B$}{right}
\sfbbox{all}
\sftopformula{F}{$B = A \circ f$}
\sfmeaningbox{mb}{92mm}{all}
  {one composition}
  {two objects}
  {the operator sits in the flow and reserves its own width}
\sfsignature{Smoke test}{mb}
\end{tikzpicture}
\end{document}