window.chgat

chgat([y, x,] [n=-1,] attr)
Set the attributes of characters.

  y
    Y-coordinate.
  x
    X-coordinate.
  n
    Number of characters.
  attr
    Attributes for characters.

Set the attributes of num characters at the current cursor position, or at
position (y, x) if supplied.  If no value of num is given or num = -1, the
attribute will be set on all the characters to the end of the line.  This
function does not move the cursor.  The changed line will be touched using
the touchline() method so that the contents will be redisplayed by the next
window refresh.