code: func NewMasterWindowSize(flags WindowFlags, title string, sz image.Point, updatefn UpdateFn) MasterWindow {
  	ctx := &context{}
  	wnd := &masterWindow{}
  
  	wnd.masterWindowCommonInit(ctx, flags, updatefn, wnd)
  
  	wnd.Title = title
  	wnd.initialSize = sz
  
  	clipboardMu.Lock()
  	if !clipboardStarted {
  		clipboardStarted = true
  		clipboard.Start()
  	}
  	clipboardMu.Unlock()
  
  	return wnd
  }
docs: // Creates new master window