def highlight_at!(y, x)
      update_highlighter if @highlighter_tokens.nil?

      fail(HighlighterUnknownSegment, "line: #{y}") if @highlighter_tokens[@offset_y + y].nil?
      fail(HighlighterUnknownSegment, "line: #{y} char: #{x}") if @highlighter_tokens[@offset_y + y][x].nil?

      @highlighter_tokens[@offset_y + y][x]
    end
def highlight_at!(y, x)
      update_highlighter if @highlighter_tokens.nil?

      fail(HighlighterUnknownSegment, "line: #{y}") if @highlighter_tokens[@offset_y + y].nil?
      fail(HighlighterUnknownSegment, "line: #{y} char: #{x}") if @highlighter_tokens[@offset_y + y][x].nil?

      @highlighter_tokens[@offset_y + y][x]
    end
The current highlight token for the item at y, x if the token is unknown throws
 a {Mad::HighlighterUnknownSegment HighlighterUnknownSegment} exception.

 @param y [Fixnum]
 @param x [Fixnum]
 @return [Symbol] the token