code: func (f *Fpdf) SetDisplayMode(zoomStr, layoutStr string) {
  	if f.err != nil {
  		return
  	}
  	if layoutStr == "" {
  		layoutStr = "default"
  	}
  	switch zoomStr {
  	case "fullpage", "fullwidth", "real", "default":
  		f.zoomMode = zoomStr
  	default:
  		f.err = fmt.Errorf("incorrect zoom display mode: %s", zoomStr)
  		return
  	}
  	switch layoutStr {
  	case "single", "continuous", "two", "default", "SinglePage", "OneColumn",
  		"TwoColumnLeft", "TwoColumnRight", "TwoPageLeft", "TwoPageRight":
  		f.layoutMode = layoutStr
  	default:
  		f.err = fmt.Errorf("incorrect layout display mode: %s", layoutStr)
  		return
  	}
  }
docs: // SetDisplayMode sets advisory display directives for the document viewer.
  // Pages can be displayed entirely on screen, occupy the full width of the
  // window, use real size, be scaled by a specific zooming factor or use viewer
  // default (configured in the Preferences menu of Adobe Reader). The page
  // layout can be specified so that pages are displayed individually or in
  // pairs.
  //
  // zoomStr can be "fullpage" to display the entire page on screen, "fullwidth"
  // to use maximum width of window, "real" to use real size (equivalent to 100%
  // zoom) or "default" to use viewer default mode.
  //
  // layoutStr can be "single" (or "SinglePage") to display one page at once,
  // "continuous" (or "OneColumn") to display pages continuously, "two" (or
  // "TwoColumnLeft") to display two pages on two columns with odd-numbered pages
  // on the left, or "TwoColumnRight" to display two pages on two columns with
  // odd-numbered pages on the right, or "TwoPageLeft" to display pages two at a
  // time with odd-numbered pages on the left, or "TwoPageRight" to display pages
  // two at a time with odd-numbered pages on the right, or "default" to use
  // viewer default mode.