code: func (v *ViewPort) Fill(ch rune, style tcell.Style) {
  	if v.v != nil {
  		for y := 0; y < v.height; y++ {
  			for x := 0; x < v.width; x++ {
  				v.v.SetContent(x+v.physx, y+v.physy, ch, nil, style)
  			}
  		}
  	}
  }
docs: // Fill fills the displayed view port with the given character and style.