Hi, The code works, but is it possible to make it shorter ?

Thank you

Fabrice

\startuseMPgraphic{DiagonalRule}
   rulethickness := \frameddimension{rulethickness};

   drawoptions(
     withpen pencircle scaled rulethickness
     withcolor \MPcolor{\framedparameter{framecolor}});

   pair leftcorner, rightcorner, Leftcorner, Rightcorner;
   leftcorner  := (rulethickness, \overlayheight-rulethickness);
   rightcorner := (\overlaywidth-rulethickness, rulethickness);
   Leftcorner  := ( rulethickness, rulethickness);
   Rightcorner := (\overlaywidth-rulethickness,\overlayheight-rulethickness);

   draw leftcorner -- rightcorner;
   draw Leftcorner -- Rightcorner;
 \stopuseMPgraphic

\defineoverlay
  [DiagonalRule]
  [\useMPgraphic{DiagonalRule}]

\define[2]\DiagonalLabel{%
  \setuptabulate [after={\blank[\frameddimension{offset}]}]
  \starttabulate [|p|r|]
    \NC    \NC \bf #2 \NC\NR
    \NC \bf #1 \NC    \NC\NR
  \stoptabulate
}
\starttext
\startluacode
  local background_one = {
   align = "middle",
   style = "type",
   background = "DiagonalRule",
  }

  local letters_1 = { "A", "B", "C", "D", "E", "F", "G", "H" }
  context.startxtable({"align={middle,lohi}, width=0.8cm,offset=0.8ex,bodyfont=9pt,framecolor=cyan"})
  context.startxrow()
  context.startxcell({"frame=off"})
  context()
  context.stopxcell()
  for _, letter in ipairs(letters_1) do
    context.startxcell()
    context(letter) context.stopxcell()
  end
  context.stopxrow()
   for _, letter in ipairs(letters_1) do
  context.startxrow()
    context.startxcell()
    context(letter)
    context.stopxcell()
  for j = 0, 7 do
  context.startxcell(  j == 0 and letter == "B" and background_one
  or j == 0 and letter == "C" and background_one
  or j == 0 and letter == "D" and background_one
  or j == 0 and letter == "G" and background_one
  or j == 0 and letter == "H" and background_one
  or j == 1 and letter == "A" and background_one
  or j == 1 and letter == "E" and background_one
  or j == 1 and letter == "F" and background_one
  or j == 1 and letter == "G" and background_one
  or j == 2 and letter == "A" and background_one
  or j == 2 and letter == "D" and background_one
  or j == 2 and letter == "F" and background_one
  or j == 2 and letter == "G" and background_one
  or j == 2 and letter == "H" and background_one
  or j == 3 and letter == "A" and background_one
  or j == 3 and letter == "C" and background_one
  or j == 3 and letter == "E" and background_one
  or j == 3 and letter == "H" and background_one
  or j == 4 and letter == "B" and background_one
  or j == 4 and letter == "D" and background_one
  or j == 4 and letter == "F" and background_one
  or j == 4 and letter == "G" and background_one
  or j == 5 and letter == "B" and background_one
  or j == 5 and letter == "C" and background_one
  or j == 5 and letter == "E" and background_one
  or j == 6 and letter == "A" and background_one
  or j == 6 and letter == "B" and background_one
  or j == 6 and letter == "C" and background_one
  or j == 6 and letter == "E" and background_one
  or j == 7 and letter == "A" and background_one
  or j == 7 and letter == "C" and background_one
  or j == 7 and letter == "D" and background_one
  )
  context()
  context.stopxcell()
  end
  context.stopxrow()
  end
  context.stopxtable()
\stopluacode
\stoptext