在 ConTeXt 和 Metafun 中从框架覆盖层到页面边缘进行绘制

Question

使用 ConTeXt 进行排版并使用 metafun 进行绘制，我想为我的目录创建一个自定义彩色覆盖层。我想为某些目录条目填充一个彩色矩形，该矩形从其章节编号（或者更确切地说是我喜欢的数字替代）延伸到页面的右边缘。但是无论我尝试什么，我的带框 metafun 覆盖层始终位于带框元素的中心，我无法不对称地向一侧绘制。

这是一个最小的工作示例。

\setuphead[chapter][number=yes]
\setuphead[section][number=no]

%Draw in TOC
\startuseMPgraphic{TOChighlight}
path p;
p := origin  -- origin shifted (0,\overlayheight) -- origin shifted (PaperWidth,\overlayheight)  -- origin shifted (PaperWidth,0) --cycle;
fill p  withcolor .3red;
\stopuseMPgraphic

\defineoverlay[TOChighlight][\uniqueMPgraphic{TOChighlight}]

\define[1]\ChapterTOCNumber{ 
  \inframed[background=TOChighlight, frame=off]{
    \hbox to 3em{\sc \doifnot{\rawstructurelistuservariable{short}}{}{\[\structurelistuservariable{short}\]\crlf} } 
  }
}

\setuplist[chapter][width=1em,  numbercommand=\ChapterTOCNumber,  width=5em, alternative=c]
\setuplist[section] [margin=6em]


\starttext

\placecontent[criterium=all]

\startchapter[title=A Vision of The Future][short=What]
  \input tufte
  \section{What will happen?}
  \section{What will cause it?}
\stopchapter

\starttext
\startchapter[title=A Causal Account][short=Why]
  \input tufte
  \section{Why did it happen?}
  \section{Why wasn't it stopped?}
\stopchapter

\stoptext

我尝试的一切都会产生如下结果：

当我尝试实现以下目标时：

额外的加分项：我还想继续沿右边缘绘制颜色，直到下一章（即，不是小节）行。metapost 能否知道下一章行在哪里，即使调用绘制命令时下一章的条目尚不存在？

Answer 1

我不确定我是否完全明白您想要什么，改变 MetaFun 图片的边界框也许就是您想要的。

我还简化了您的路径 p 并在框架上设置了偏​​移量。

对于加分题，我不知道。

\setuphead[chapter][number=yes]
\setuphead[section][number=no]

%Draw in TOC
\startuseMPgraphic{TOChighlight}
path p;
p:=unitsquare xyscaled (PaperWidth,OverlayHeight);
fill p  withcolor .3red withtransparency (1,.5);
setbounds currentpicture to unitsquare xyscaled (OverlayWidth,OverlayHeight);
\stopuseMPgraphic

\defineoverlay[TOChighlight][\uniqueMPgraphic{TOChighlight}]

\define[1]\ChapterTOCNumber{ 
  \inframed[background=TOChighlight,offset=0pt,frame=off]{
    \hbox to 3em{\sc \doifnot{\rawstructurelistuservariable{short}}{}{\[\structurelistuservariable{short}\]\crlf} } 
  }
}

\setuplist[chapter][width=1em,  numbercommand=\ChapterTOCNumber,  width=5em, alternative=c]
\setuplist[section] [margin=6em]

\starttext

\placecontent[criterium=all]

\startchapter[title=A Vision of The Future][short=What]
  \input tufte
  \section{What will happen?}
  \section{What will cause it?}
\stopchapter

\starttext
\startchapter[title=A Causal Account][short=Why]
  \input tufte
  \section{Why did it happen?}
  \section{Why wasn't it stopped?}
\stopchapter

\stoptext