code: func (v *ViewPort) Reset() {
  	v.limx = 0
  	v.limy = 0
  	v.viewx = 0
  	v.viewy = 0
  }
docs: // Reset resets the record of content, and also resets the offset back
  // to the origin.  It doesn't alter the dimensions of the view port, nor
  // the physical location relative to its parent.