易碎的 tcolorbox：奇数/偶数页识别错误

Question

Tcolorbox包不能正确识别奇数/偶数。来自这里对于双面文档不再正确工作

\documentclass[]{article}
\RequirePackage{changepage}
\RequirePackage[breakable, many]{tcolorbox}
\usepackage{lipsum}

\newcommand\printpage{%
Page is \thepage. It is \checkoddpage\ifoddpage odd\else even\fi.
}

\NewTColorBox{SomeBox}{+O{}}{%
  breakable, enhanced,
  check odd page,
  lowerbox=ignored,
underlay={%
  if odd page={%
     \draw[red!75!black,line width=1pt]
     (frame.north east)
     --(frame.south west);%
   }{%
     \draw[red!75!black,line width=1pt]
     (frame.north west)
     --(frame.south east);%
   },
},%
  #1
}

\begin{document}

\begin{SomeBox}

\printpage

\lipsum*

\bigskip
\printpage
\end{SomeBox}
\printpage
\end{document}

Answer 1

如果您if odd page直接在框代码内（而不是在里面underlay={...}）使用检查，它会起作用，如下所示：

\documentclass{article}
\usepackage{changepage}
\usepackage[breakable, many]{tcolorbox}
\usepackage{lipsum}

\newcommand\printpage{%
  Page is \thepage. It is \checkoddpage\ifoddpage odd\else even\fi.\par
}

\NewTColorBox{SomeBox}{+O{}}{%
  breakable, enhanced,
  check odd page,
  lowerbox=ignored,
  if odd page={
    underlay={
       \draw[blue!75!black,line width=1pt]
       (frame.north east)
       --(frame.south west);
    }
  }{
    underlay={
       \draw[red!75!black,line width=1pt]
       (frame.north west)
       --(frame.south east);
    }
  },
  #1
}

\begin{document}

\begin{SomeBox}
\printpage
\lipsum*[1-3]
\par
\printpage
\end{SomeBox}

\newpage
\begin{SomeBox}
\printpage
\lipsum*[4-6]
\par
\printpage
\end{SomeBox}

\end{document}

/tcb/if odd page我认为在参数中不起作用的原因/tcb/underlay是它/tcb/if odd page是一个tcolorbox键，而不是传递给样式的值所预期的〈图形代码〉（TikZ 代码等）/tcb/underlay。

当使用钥匙的盒子/tcb/breakable跨页破碎时，所有部件都会得到相同的检查结果，这似乎是在盒子启动时完成的。但通过使用计数器tcbbreakpart，您可以根据部件编号（从 1 开始）在可破碎的盒子内交替颜色或任何您想要的东西：

\documentclass{article}
\usepackage{changepage}
\usepackage[breakable, many]{tcolorbox}
\usepackage{lipsum}

\newcommand\printpage{%
  Page is \thepage. It is \checkoddpage\ifoddpage odd\else even\fi.\par
}

\NewTColorBox{SomeBox}{+O{}}{%
  breakable, enhanced,
  check odd page,
  lowerbox=ignored,
  if odd page={
    underlay={
       \ifodd\value{tcbbreakpart}
         \draw[blue!75!black,line width=1pt]
         (frame.north east) -- (frame.south west);
       \else
         \draw[red!75!black,line width=1pt]
         (frame.north west) -- (frame.south east);
       \fi
    }
  }{
    underlay={
       \ifodd\value{tcbbreakpart}
         \draw[red!75!black,line width=1pt]
         (frame.north west) -- (frame.south east);
       \else
         \draw[blue!75!black,line width=1pt]
         (frame.north east) -- (frame.south west);
       \fi
    }
  },
  #1
}

\begin{document}

\begin{SomeBox}
\printpage
\lipsum
\par
\printpage
\end{SomeBox}

\begin{SomeBox}
\printpage
\lipsum
\par
\printpage
\end{SomeBox}

\end{document}