如图所示，框内的独立文本跨越整个页面宽度，如何操作？

Question

我认为你不可能拥有你想要的一切。我几乎可以肯定，如果不认真努力，你不可能拥有你想要的一切。

这里有两种可能的方法。两者都适用tcolorbox于文本和边缘图像内容。

这使用了一种修改后的环境形式examplebox。缺点是，在偶数页上必须首先指定边缘图像，而在奇数页上则必须第二个指定边缘图像，即内容切换不是自动的。
这会自动切换内容。缺点是您必须使用\tcbsidebyside[example box]{<text column content>}{<marginal image column content>}来指定文本和边距图像。如果您想要标题，则将其作为参数传递给example box。

我用 4 个例子来说明这一点：奇数页和偶数页上各举一个每种类型的例子。

\begin{examplebox}{}
  I use my ``examplebox'' as usual text and margin figure work as they should be but I want my example box spread out to the right margin on an odd page, breakable, and spread out to the left margin on the even page.
  \tcblower
  \includegraphics[scale=0.25]{example-image}
  \captionof{figure}{I am figure}\label{fig:example-image}
\end{examplebox}

这里，边缘图像位于其后\tcblower，文本位于其前。可以向环境传递一个可选参数，以在本地覆盖设置。强制参数包含标题（此处为空）。

\tcbsidebyside[example box=Title here]{%
  I use my ``examplebox'' as usual text and margin figure work as they should be but I want my example box spread out to the right margin on an odd page, breakable, and spread out to the left margin on the even page.%
}{%
  \includegraphics[scale=0.25]{example-image-a}
  \captionof{figure}{I am a figure}\label{fig:example-image-a}%
}

这里example box使用了 style 和 title Title here。文本放在第一个强制参数中；边缘图像放在第二个强制参数中。

\newpage

我们的奇怪页面就这样结束了。

\begin{examplebox}{}
  \includegraphics[scale=0.25]{example-image-b}
  \captionof{figure}{I am b figure}\label{fig:example-image-b}
  \tcblower
  I use my ``examplebox'' as usual text and margin figure work as they should be but I want my example box spread out to the right margin on an odd page, breakable, and spread out to the left margin on the even page.
\end{examplebox}

这里，边缘图像位于之前\tcblower，而文本位于之后。参数与前面相同。

\tcbsidebyside[example box]{% with no title
  I use my ``examplebox'' as usual text and margin figure work as they should be but I want my example box spread out to the right margin on an odd page, breakable, and spread out to the left margin on the even page.%
}{%
  \includegraphics[scale=0.25]{example-image-c}
  \captionof{figure}{I am c figure}\label{fig:example-image-c}%
}

这里，example box样式调用时没有参数，因此在这种情况下标题为空。与之前一样，文本在第一个强制参数中指定；边距图像在第二个参数中指定。由于我们在偶数页上，因此排版时将自动切换此顺序，即边距图像将设置在框的左侧，文本将设置在右侧。

我们的偶数页到此结束。

第一种方法与examplebox环境已被修改为使用自定义计数器，以便说明第二种方法如何集成到单个编号序列中，以防您想混合使用这两种方法。如果不想，您可以更方便地坚持使用tcbcounter。

\documentclass[twoside,chapterprefix]{scrbook}
\usepackage{graphicx}
\usepackage[showframe, papersize={21cm,23cm},top=1.8cm, bottom=2cm, outer=7cm, inner=2cm, heightrounded, marginparwidth=5.0cm, marginparsep=0.5cm]{geometry}% I guess you know this package tramples wantonly on KOMA-script's careful typographic design?!
%The package provides an environment for coloured and framed text boxes with a heading line
\usepackage[most]{tcolorbox}

\NewTColorBox
[%
  use counter=mytcbcounter, 
]{examplebox}{ O{} +m }{%
  breakable, 
  toggle enlargement=evenpage, 
  grow to right by=\marginparwidth+\marginparsep, 
  sidebyside, 
  lower separated=false, 
  if odd page={lefthand width=\textwidth-2.5mm-2pt, before lower app=\centering,}{righthand width=\textwidth-2.5mm-2pt, before upper app=\centering},
  boxrule=.5mm, 
  boxsep=1mm, 
  left=1pt,
  right=1pt, 
  sidebyside gap=\marginparsep+2mm+2pt, 
  fonttitle=\bfseries\Large, 
  title={Problem~\themytcbcounter #2}, 
  #1,
}

\tcbset{%
  example box/.style={
    breakable, 
    toggle enlargement=evenpage, 
    grow to right by=\marginparwidth+\marginparsep, 
    sidebyside, 
    lower separated=false, 
    if odd page={lefthand width=\textwidth-2.5mm-2pt, before lower app=\centering,}{before upper app=\centering, righthand width=\textwidth-2.5mm-2pt, sidebyside switch},% p.125 of manual
    boxrule=.5mm, 
    boxsep=1mm, 
    left=1pt,
    right=1pt,      
    sidebyside gap=\marginparsep+2mm+2pt, 
    fonttitle=\bfseries\Large, 
    code=\refstepcounter{mytcbcounter},
    title={Problem~\themytcbcounter{} #1}, 
  },
}

\newcounter{mytcbcounter}
\setcounter{mytcbcounter}{0}
\numberwithin{mytcbcounter}{chapter}

\begin{document}

\chapter{Introduction}

\begin{examplebox}{}
  I use my ``examplebox'' as usual text and margin figure work as they should be but I want my example box spread out to the right margin on an odd page, breakable, and spread out to the left margin on the even page.
  \tcblower
  \includegraphics[scale=0.25]{example-image}
  \captionof{figure}{I am figure}\label{fig:example-image}
\end{examplebox}


\tcbsidebyside[example box=Title here]{%
  I use my ``examplebox'' as usual text and margin figure work as they should be but I want my example box spread out to the right margin on an odd page, breakable, and spread out to the left margin on the even page.%
}{%
  \includegraphics[scale=0.25]{example-image-a}
  \captionof{figure}{I am a figure}\label{fig:example-image-a}%
}

\newpage

\begin{examplebox}{}
  \includegraphics[scale=0.25]{example-image-b}
  \captionof{figure}{I am b figure}\label{fig:example-image-b}
  \tcblower
  I use my ``examplebox'' as usual text and margin figure work as they should be but I want my example box spread out to the right margin on an odd page, breakable, and spread out to the left margin on the even page.
\end{examplebox}

\tcbsidebyside[example box]{% with no title
  I use my ``examplebox'' as usual text and margin figure work as they should be but I want my example box spread out to the right margin on an odd page, breakable, and spread out to the left margin on the even page.%
}{%
  \includegraphics[scale=0.25]{example-image-c}
  \captionof{figure}{I am c figure}\label{fig:example-image-c}%
}

\end{document}

Answer 1