如何强制列表标题名称和编号始终出现，即使标题为空？

Question

我注意到lstlisting当没有指定标题时，环境似乎会抑制标题名称和编号。

请参阅下面的代码：

\documentclass{article}
\usepackage{listings}
\lstset{language=C}
\begin{document}
The listing below will have no caption.
\begin{lstlisting}
int main(int argc, char *argv[])
{
    return 0;
}
\end{lstlisting}
Now this code will show the caption. 
\begin{lstlisting}[caption=This is the caption]
int main(int argc, char *argv[])
{
    return 0;
}
\end{lstlisting}
\end{document}

我发现的唯一解决方案是将标题设置为空白并删除分隔符，但这个解决方案看起来不太好：

\documentclass{article}
\usepackage{listings}
\lstset{language=C}
\usepackage{caption}
\captionsetup{labelsep=none}
\begin{document}
This is not an elegant solution, but works:
\begin{lstlisting}[caption=\ ]
int main(int argc, char *argv[])
{
    return 0;
}
\end{lstlisting}
\end{document}

有任何想法吗？

Answer 1

定义默认标题（我使用了\relax）并设置标题格式，以检查给定的标题是否不同。诀窍是知道标题文本存储在中\lst@caption。

\documentclass{article}
\usepackage{listings,caption}

\lstset{language=C,caption=\relax}

\makeatletter
%% define a caption format; if the caption
%% is the default (\relax), the separator is
%% not printed; as long as no caption text
%% starts with \relax, this will work
\DeclareCaptionFormat{alsoempty}{%
  #1\if\relax\expandafter\noexpand\lst@caption\else#2#3\fi}
\makeatother
%% set this format as the default for lstlisting
\captionsetup[lstlisting]{format=alsoempty}

\begin{document}

The listing below will have no caption.
\begin{lstlisting}
int main(int argc, char *argv[])
{
    return 0;
}
\end{lstlisting}
Now this code will show the caption. 
\begin{lstlisting}[caption=This is the caption]
int main(int argc, char *argv[])
{
    return 0;
}
\end{lstlisting}
\end{document}