Hello,
I want the text area to be surrounded by a margin of 20 mm (top, right, left and bottom).
I have already done this to have a left and right margin of 20 mm.

\setuplayout
  [height=middle,
   backspace=20mm,
   width=middle]

I  think that I must now have :

topdistance + header + headerdistance = 20mm

footerdistance + footer + bottomdistance + bottom = 20 mm

How to do ?

Thanks

Fabrice