code: func (ctx *context) nonblockOpen(flags WindowFlags, body rect.Rect, header rect.Rect, updateFn UpdateFn) *Window {
  	popup := createWindow(ctx, "")
  	popup.idx = len(ctx.Windows)
  	popup.updateFn = updateFn
  	ctx.Windows = append(ctx.Windows, popup)
  
  	popup.Bounds = body
  	popup.layout = &panel{}
  	popup.flags = flags
  	popup.flags |= WindowBorder | windowPopup
  	popup.flags |= WindowDynamic | windowSub
  	popup.flags |= windowNonblock
  
  	popup.header = header
  
  	if updateFn == nil {
  		popup.specialPanelBegin()
  	}
  	return popup
  }
docs: ///////////////////////////////////////////////////////////////////////////////////
  // POPUP
  ///////////////////////////////////////////////////////////////////////////////////