将 varwidth 与 algorithm2e 结合使用

Question

我试图在一个algortihm2e结构周围画一个框，如下所示：

我尝试使用该varwidth包来获取具有内容自然宽度的盒子：

\documentclass{article}

\usepackage{algorithm2e}
\usepackage{varwidth}

\begin{document}
    \fbox{\begin{varwidth}{10cm}
        \If{condition}{
            loop content
        }
    \end{varwidth}}
\end{document}

不幸的是，结果如下： 看起来当内部使用或构造varwidth时会占用最大宽度。我怎样才能获得具有自然宽度的框？\If\For

Answer 1

同时，我自己想出了一个办法：覆盖algorithm2e绘制块的内部宏并varwidth在那里使用环境。

以下是该选项的解决方案vlined：

\documentclass{article}

\usepackage[vlined]{algorithm2e}
\usepackage{varwidth}

\makeatletter
\renewcommand{\algocf@Vline}[1]{%     no vskip in between boxes but a strut to separate them, 
    \strut\par\nointerlineskip% then interblock space stay the same whatever is inside it
    \algocf@push{\skiprule}%        move to the right before the vertical rule
    \vbox{\hbox{\vrule%
        \begin{varwidth}{\hsize}%
            \vbox{\algocf@push{\skiptext}%move the right after the rule
                \hbox{%
                    \algocf@addskiptotal%
                    \begin{varwidth}{\hsize}%
                        #1% inside the block
                    \end{varwidth}%
                }%
                \Hlne}%
        \end{varwidth}%
    }\vskip\skiphlne}%
    \algocf@pop{\skiprule}%\algocf@subskiptotal% restore indentation
    \nointerlineskip}% no vskip after

\renewcommand{\algocf@Vsline}[1]{%    no vskip in between boxes but a strut to separate them, 
    \strut\par\nointerlineskip% then interblock space stay the same whatever is inside it
    \algocf@bblockcode%
    \algocf@push{\skiprule}%        move to the right before the vertical rule
    \hbox{\vrule%               the vertical rule
        \begin{varwidth}{\hsize}%
            \vbox{\algocf@push{\skiptext}%move the right after the rule
                \hbox{\algocf@addskiptotal%
                    \begin{varwidth}{\hsize}%
                        #1% inside the block
                    \end{varwidth}%
                }}%
        \end{varwidth}%
    }%
    \algocf@pop{\skiprule}% restore indentation
    \algocf@eblockcode%
}
\makeatother

\begin{document}
    \fbox{\begin{varwidth}{\hsize}
            \If{condition}{
                loop content

                a line longer than the loop header
            }
    \end{varwidth}}
\end{document}

对于块样式的其他选项\algocf@Noline可能必须进行类似的调整（未经测试）。

Answer 2

这是一个使用\tikzmarks 来定位顶部、底部和右侧（或多或少）的临时解决方案。

请注意，如果没有 minipage，algorithm2e 将使用边距外的空间。

\documentclass{article}

\usepackage{algorithm2e}
\usepackage{tikz}
\usetikzlibrary{tikzmark}

\begin{document}
    \begin{minipage}{\textwidth}
      \tikzmark{A}\If{condition\tikzmark{B}}{
            loop content
        }\tikzmark{C}
    \end{minipage}%
    \begin{tikzpicture}[overlay, remember picture]
      %\draw[red] (pic cs:A) -- (pic cs:B) -- (pic cs:C);
      \path (pic cs:B) node[right, inner sep=0pt] (BB) {\phantom{ \textbf{then}}};
      \path (pic cs:C) ++(0,\baselineskip) coordinate (CC);
      \draw (pic cs:A) ++(0, \ht\strutbox)  rectangle (BB.east |- CC);
    \end{tikzpicture}
\end{document}