在 Context 中更改逐项标记位置

Question

使用 Metapost 手动定义 itemize 标记时，标记的位置似乎很低（见图片，添加的粉红线是为了突出显示问题）。它看起来相当丑陋，我想将其向上移动一点。

\startuseMPgraphic{itemize:triangle}
  save p; path p;
  p := ( (0,-0.5) --(0,0.5)--(0.5,0)--cycle ) scaled ExHeight;
  fill p withcolor red;
\stopuseMPgraphic

\definesymbol[itemize:main][\useMPgraphic{itemize:triangle}]
\setupitemize[1][symbol=itemize:main]

\starttext

\startitemize
    \startitem
        The triangle position could be better!
    \stopitem
\stopitemize

\stoptext

Answer 1

要将项目化符号对齐到行的中间，可以使用 plain-TeX-inherited \vcenter。

\startuseMPgraphic{itemize:triangle}
  save p; path p;
  p := ( (0,-0.5) --(0,0.5)--(0.5,0)--cycle ) scaled ExHeight;
  fill p withcolor red;
\stopuseMPgraphic

\definesymbol[itemize:main][\vcenter{\hbox{\useMPgraphic{itemize:triangle}}}]
\setupitemize[1][symbol=itemize:main]

\starttext
\startitemize
  \startitem
    The triangle position could be better!
  \stopitem
\stopitemize
\stoptext