Substrings in ConTeXt

Question

Problem

Trying to get the first letter of a word for a chapter heading. The chapter style is being applied as follows:

  \setuphead[chapter][
    command=\StyleChapter,
    % Hide the header's chapter name.
    header=empty,
    % Hide the footer's page number.
    footer=empty,
  ]

To emphasize the first character of the word (e.g., "Bread"), I've written:

\define[2]\StyleChapter{%
  \framed[
    frame=off,
    width=local,
    align={flushright,low,nothyphenated,verytolerant},
    width=\dimexpr\textwidth+\rightmargindistance,
    height=\dimexpr\textheight-\footerheight,
  ]{\substring{#2}{1}{1}}{#2}
}

As well as:

  ]{\substring{#2}{1}{1}{#2}}

And:

  ]{{#2}{\substring{#2}{1}{1}}}

And:

\defineframed[StyleChapterFramed][
  frame=off,
  width=local,
  align={flushright,low,nothyphenated,verytolerant},
  width=\dimexpr\textwidth+\rightmargindistance,
  height=\dimexpr\textheight-\footerheight,
]

\define[2]\StyleChapter{%
  \StyleChapterFramed{%
    {\getfirstcharacter{#2}\firstcharacter #2}
  } 
} 

And variations thereof. It seems \substring is not a macro available in ConTeXT? The effect I'm trying to produce:

The effect I've achieved so far:

Using the following yields the letter H, but I'm trying to use the chapter title, which is parameter #2:

{\getfirstcharacter{Hello}\firstcharacter #2}

Any ideas how to obtain a substring in ConTeXt?

Answer 1

To get the first character of a string use \getfirstcharacter. For example:

\getfirstcharacter{Hello} \firstcharacter -- \remainingcharacters

Thus to duplicate the first character in the chapter, you would use:

\defineframed
  [StyleChapterFramed]
  [
    frame=off,
    width=local,
    align={flushright,low,nothyphenated,verytolerant},
    width=\dimexpr\textwidth+\rightmargindistance\relax,
    height=\dimexpr\textheight-\footerheight\relax,
  ]

\define[1]\StyleChapter
  {\getfirstcharacter{#1}\StyleChapterFramed{\firstcharacter #1}}

\setuphead
  [chapter]
  [
    deeptextcommand=\StyleChapter,
  ]