将“pgfornaments”中的装饰品集中在定理环境周围？

Question

这是我的最小代码：

\documentclass[12pt,letterpaper]{article}

\usepackage{lmodern}
\usepackage[T1]{fontenc}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{pgfornament}

\newtheorem{thm}{Theorem}

\newcommand*{\centeredornament}{\begin{center}\pgfornament{88}\end{center}}
\newenvironment{theorem}[1][]{\centeredornament\begin{thm}[#1]\upshape}{\end{thm}\centeredornament}

\begin{document}
 \begin{theorem}[This is a sentence. ]
  This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. 
 \end{theorem}

\end{document}

它产生以下输出：

黑色部分标记了页面的宽度。看到装饰物向右移动了吗，而不是实际上位于页面宽度的“中心”吗？我该如何解决这个问题？

Answer 1

您应该[width=13cm]向使用的命令添加选项\pgfornament，例如

\pgfornament[width=13cm]{88}

如果没有这个宽度，装饰物就会太长而无法适合文本的宽度。

您可以使用

\usepackage{showframe}

使打字区域和边距可视化。

拥有完整的 MWE

\documentclass[12pt,letterpaper]{article}

\usepackage{showframe} % <==============================================
\usepackage{lmodern}
\usepackage[T1]{fontenc}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{pgfornament}

\newtheorem{thm}{Theorem}

\newcommand*{\centeredornament}{\begin{center}\pgfornament[width=13cm]{88}\end{center}} % 88
\newenvironment{theorem}[1][]{\centeredornament\begin{thm}[#1]\upshape}{\end{thm}\centeredornament}

\begin{document}
\begin{theorem}[This is a sentence. ]
  This is a sentence. This is a sentence. This is a sentence. This is a 
  sentence. This is a sentence. This is a sentence. This is a sentence. 
  This is a sentence. This is a sentence. This is a sentence. This is a 
  sentence. This is a sentence. This is a sentence. This is a sentence. 
  This is a sentence. This is a sentence. This is a sentence. This is a 
  sentence. This is a sentence. This is a sentence. This is a sentence. 
  This is a sentence. This is a sentence. This is a sentence. This is a 
  sentence. This is a sentence. This is a sentence. This is a sentence. 
  This is a sentence. This is a sentence. This is a sentence. This is a 
  sentence. This is a sentence. This is a sentence. This is a sentence. 
  This is a sentence. This is a sentence. This is a sentence. This is a 
  sentence. This is a sentence. This is a sentence. This is a sentence. 
  This is a sentence. This is a sentence. This is a sentence. This is a 
  sentence. This is a sentence. 
\end{theorem}

\end{document}

你会得到这个结果：

如果没有的话，[width=13cm]你会得到以下结果（参见到达边缘的装饰线）：

Answer 2

您的装饰品实际上已经超出了边缘，正如代码问题中发出的过满 vbox 警告所告诉您的那样。

因此，您可以使用以下方法更好地设置缩进\makebox：

\newcommand*{\centeredornament}{\noindent\makebox[\textwidth][c]{\pgfornament[width=1.1\textwidth]{88}}}

装饰物的宽度[width=1.1\textwidth]故意比文本宽度稍大（但居中），这似乎是您的意图。当然，您可以随意设置此值。

在全：

\documentclass[12pt,letterpaper]{article}

\usepackage{lmodern}
\usepackage[T1]{fontenc}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{pgfornament}
\usepackage{showframe}

\newtheorem{thm}{Theorem}

\newcommand*{\centeredornament}{\noindent\makebox[\textwidth][c]{\pgfornament[width=1.1\textwidth]{88}}}

\newenvironment{theorem}[1][]{\centeredornament\begin{thm}[#1]\upshape}{\end{thm}\vspace{-1ex}\centeredornament}

\begin{document}

 \begin{theorem}[This is a sentence. ]
  This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence. This is a sentence.
 \end{theorem}

\end{document}