code: func FillRect(x, y, w, h int, r rune) {
  	x, y, w, h = clip(x, y, w, h)
  	if w < 1 || y < -1 {
  		return
  	}
  
  	for yy := y; yy < y+h; yy++ {
  		for xx := x; xx < x+w; xx++ {
  			putCharUnsafe(xx, yy, r)
  		}
  	}
  }
docs: // FillRect paints the area with r character using the current colors