Automatic subcaption listing

Question

Imagine I have the following figure

\begin{figure}[H]
\begin{minipage}{0.45\linewidth}
\begin{subfigure}[b]{\textwidth}
\centering
        \includegraphics[width=.7\linewidth]{example-image}
        \caption{}
        \label{fig1a}
    \end{subfigure}
    \quad
    \begin{subfigure}[b]{\textwidth}
    \centering
        \includegraphics[width=.7\linewidth]{example-image}
        \caption{}
        \label{fig1b}
    \end{subfigure}
\end{minipage}%
\begin{minipage}{0.55\linewidth}
    \begin{subfigure}[b]{0.5\textwidth}
    \centering
        \includegraphics[width=\linewidth]{example-image}
        \caption{}
        \label{fig1c}
    \end{subfigure}%
    \begin{subfigure}[b]{0.5\textwidth}
    \centering
        \includegraphics[width=\linewidth]{example-image}
        \caption{}
        \label{fig1d}
    \end{subfigure}
    \quad
    \begin{subfigure}[b]{0.5\textwidth}
    \centering
        \includegraphics[width=\linewidth]{example-image}
        \caption{}
        \label{fig1e}
    \end{subfigure}%
    \begin{subfigure}[b]{0.5\textwidth}
    \centering
        \includegraphics[width=\linewidth]{example-image}
        \caption{}
        \label{fig1f}
    \end{subfigure}
\end{minipage}
\caption{(a) A caption. (b) Another caption. (c) Yet another caption. (d) So many captions. (e) Really. (f) I'm done with captions.} 
\label{fig1}
\end{figure}

which gives

My question: is it possible to automatically label the subfigures so that I don't have to write (a), (b), ... (f) by hand on the figure caption, and keep their order (as set by the mini pages)?

In some sense, it would be nice to simply write the caption under each subfigure but make these captions appear, automatically labelled in the correct ordering, in the figure's main caption. Any ideas?

Edit: I saw this question, but it still doesn't fix the automatic ordering problem.

Answer 1

The creates a global macro (\thecaption) containing the accumulated subcaptions.

\documentclass{article}
\usepackage{graphicx}
\usepackage{subcaption}

\newcommand{\thecaption}{}% reserve global name

\newcommand{\mysubcaption}[1]{% #1 = text
  \caption{}%
  \ifnum\value{subfigure}=1 
    \xdef\thecaption{(\thesubfigure)~#1}%
  \else
    \xdef\thecaption{\thecaption, (\thesubfigure)~#1}%
  \fi}

\begin{document}
\begin{figure}[ht]% friends don't let friends use H
\begin{minipage}{0.45\linewidth}
\begin{subfigure}{\textwidth}
\centering
        \includegraphics[width=.7\linewidth]{example-image}
        \mysubcaption{A caption}
    \end{subfigure}
    \vskip\floatsep
    \begin{subfigure}{\textwidth}
    \centering
        \includegraphics[width=.7\linewidth]{example-image}
        \mysubcaption{Another caption}
    \end{subfigure}
\end{minipage}%
\begin{minipage}{0.55\linewidth}
    \begin{subfigure}[b]{0.5\textwidth}
    \centering
        \includegraphics[width=\linewidth]{example-image}
        \mysubcaption{Yet another caption}
    \end{subfigure}%
    \begin{subfigure}[b]{0.5\textwidth}
    \centering
        \includegraphics[width=\linewidth]{example-image}
        \mysubcaption{So many captions}
    \end{subfigure}
    \vskip\floatsep
    \begin{subfigure}[b]{0.5\textwidth}
    \centering
        \includegraphics[width=\linewidth]{example-image}
        \mysubcaption{Really}
    \end{subfigure}%
    \begin{subfigure}[b]{0.5\textwidth}
    \centering
        \includegraphics[width=\linewidth]{example-image}
        \mysubcaption{I'm done with captions}
    \end{subfigure}
\end{minipage}
\caption{\thecaption.}% Note the period.
\end{figure}
\end{document}

Answer 2

You can do it with expl3.

\documentclass{article}
\usepackage{subcaption}
\usepackage{graphicx}

\ExplSyntaxOn

\AddToHook{env/figure/begin}
  {
    \seq_gclear:N \g_samwolfe_ac_captions_seq
  }

\NewDocumentCommand{\delayedsubcaption}{m}
  {
    \int_gincr:N \g_samwolfe_ac_label_int
    \caption{ \label{ac@\int_to_arabic:n { \g_samwolfe_ac_label_int}} }
    \seq_gput_right:Nx \g_samwolfe_ac_captions_seq
      {
        \exp_not:N \protect
        (\exp_not:N \subref {ac@\int_to_arabic:n { \g_samwolfe_ac_label_int}})
        \exp_not:n { \nobreakspace #1 }
      }
  }

\NewExpandableDocumentCommand{\printsubcaptions}{}
  {
    \seq_use:Nn \g_samwolfe_ac_captions_seq { .~ }.
  }

\int_new:N \g_samwolfe_ac_label_int
\seq_new:N \g_samwolfe_ac_captions_seq

\ExplSyntaxOff

\begin{document}

\listoffigures

\section{Main}

\begin{figure}[htp]

\begin{minipage}{0.45\linewidth}
\begin{subfigure}[b]{\textwidth}
\centering
        \includegraphics[width=.7\linewidth]{example-image}
        \delayedsubcaption{A caption}
        \label{fig1a}
    \end{subfigure}

    \begin{subfigure}[b]{\textwidth}
    \centering
        \includegraphics[width=.7\linewidth]{example-image}
        \delayedsubcaption{Another caption}
        \label{fig1b}
    \end{subfigure}
\end{minipage}\hfill
\begin{minipage}{0.55\linewidth}
    \begin{subfigure}[b]{0.5\textwidth}
    \centering
        \includegraphics[width=\linewidth]{example-image}
        \delayedsubcaption{Yet another caption}
        \label{fig1c}
    \end{subfigure}%
    \begin{subfigure}[b]{0.5\textwidth}
    \centering
        \includegraphics[width=\linewidth]{example-image}
        \delayedsubcaption{So many captions}
        \label{fig1d}
    \end{subfigure}

    \begin{subfigure}[b]{0.5\textwidth}
    \centering
        \includegraphics[width=\linewidth]{example-image}
        \delayedsubcaption{Really}
        \label{fig1e}
    \end{subfigure}%
    \begin{subfigure}[b]{0.5\textwidth}
    \centering
        \includegraphics[width=\linewidth]{example-image}
        \delayedsubcaption{I'm done with captions}
        \label{fig1f}
    \end{subfigure}
\end{minipage}
\caption{\printsubcaptions}
\label{fig1}

\end{figure}

\end{document}

You can add whatever you want to the main caption. Disposable labels are created, but you can add your own for reference.

I changed your \quad to a blank line, which is “the right thing to do”.