tcolorbox 中的精确尺寸

Question

当框包含一个title节点时title，其west锚点可用于延伸底线，但当没有定义标题时不会创建节点，此时我们需要区分有标题和无标题的框。

由于原始代码已经在code选项中做出了这种区分，我只是将右下角定义移到了此选项中。对于无标题的情况，代码绘制 15mm 角，但对于有标题的情况，底线会延伸到标题的左边距。

顺便说一下，我还改变了角的绘制方式，现在它们用一个\draw带有语法的命令来定义|-，而不是两条不同的线

\documentclass{book}

\usepackage[most]{tcolorbox}
\usepackage{varwidth}
\tcbuselibrary{skins,breakable}

\usepackage{polyglossia}
\setmainlanguage{english}
\newfontfamily{\englishfont}{Arial}


\newcounter{proposition}[chapter]
\renewcommand{\theproposition}{\arabic{proposition}}
\newcommand{\propositionlabel}{\textbf{Prop \theproposition}}
\newcommand{\propositionnode}{%
\node[fill=blue!5!white, draw=blue!75!black, line width=.5pt, below right, minimum height=2em, 
    text width=.8cm, align=center] at ([xshift=3mm,yshift=-1mm]frame.north east) {\propositionlabel}}


\newenvironment{proposition}[1][]{%
\refstepcounter{proposition}%
\begin{tcolorbox}[enhanced jigsaw, breakable, colback=white, colframe=white, arc=0mm, rightrule=0mm, leftrule=0mm, toprule=0mm,
bottomrule=0mm, top=2mm, bottom=2mm, left=2mm, right=2mm, varwidth boxed title, 
attach boxed title to top right={xshift=.5mm,yshift=- \tcboxedtitleheight+.5mm},
boxed title style={enhanced, arc=0pt, outer arc=0pt, colframe=blue!75!black, right=1mm, boxrule=.5mm},
colbacktitle=blue!5!white, coltitle=black, extrude right by=-15mm,
underlay unbroken and first={%
    \propositionnode;

    \draw [blue!75!black,line width=.5mm]([shift={(15mm-.5\pgflinewidth,-15mm+.5\pgflinewidth)}]frame.north east)|-([shift={(-\textwidth/4+15mm,+.5\pgflinewidth)}]frame.north east);

    \draw [blue!75!black,line width=.5mm]([shift={(.5\pgflinewidth,-15mm+.5\pgflinewidth)}]frame.north west)|-([shift={(\textwidth/4,+.5\pgflinewidth)}]frame.north west);

    },
underlay unbroken and last={%
    \draw [blue!75!black,line width=.5mm]([shift={(.5\pgflinewidth,15mm+.5\pgflinewidth)}]frame.south west)|-([shift={(\textwidth/4,+.5\pgflinewidth)}]frame.south west);
        },
code={\ifstrempty{#1}
    {\tcbset{
    before upper={\parshape 4
        0pt \dimexpr \hsize-14mm\relax
        0pt \dimexpr \hsize-14mm\relax
        0pt \dimexpr \hsize-14mm\relax
        0pt \hsize},
     underlay unbroken and last={
        \draw [blue!75!black,line width=.5mm]([shift={(15mm-.5\pgflinewidth,15mm+.5\pgflinewidth)}]frame.south east)|-([shift={(-\textwidth/4+15mm,+.5\pgflinewidth)}]frame.south east);
},
    }}
    {\tcbset{
    title={#1},
    before upper={\vspace*{\baselineskip}\parshape 3
        0pt \dimexpr \hsize-14mm\relax
        0pt \dimexpr \hsize-14mm\relax
        0pt \hsize},
    underlay unbroken and last={
    \draw [blue!75!black,line width=.5mm]([shift={(15mm-.5\pgflinewidth,15mm+.5\pgflinewidth)}]frame.south east)|-(title.west|-frame.south);}
    }}}
]}{%
\end{tcolorbox}}

\begin{document}
\pagestyle{empty}

\noindent
In this document, the text would be written in arabic, a right-to-left language
\vspace{5mm}

\begin{proposition}
A non-titled proposition
\vspace{2.2cm}
\end{proposition}

\vspace{5mm}
\begin{proposition}[A long title]
A titled proposition
\vspace{2cm}
\end{proposition}

\end{document}

此处留下旧评论以供记录

这不是答案，而是带有图片的评论。OP 说：

当我的框有标题时，标题框的规则（使用命令 boxrule=.5mm 放置的规则）与框的东北规则（使用选项 line width=.5mm 获得的规则）不重叠。我怎样才能使规则完全重叠？

我用 xelatex 编译了代码，结果如下：

我看到标题框（已opacityframe=0.5添加）完全对齐并与东北规则（蓝线）重叠。那么问题出在哪里？我误解了您的问题吗？

Answer 1