code: func (dc *Context) capper() raster.Capper {
  	switch dc.lineCap {
  	case LineCapButt:
  		return raster.ButtCapper
  	case LineCapRound:
  		return raster.RoundCapper
  	case LineCapSquare:
  		return raster.SquareCapper
  	}
  	return nil
  }
docs: // Path Drawing