code: func (u *UserInterface) getScale() float64 {
  	if !u.isFullscreen() {
  		return u.scale
  	}
  	if u.fullscreenScale == 0 {
  		v := u.window.GetMonitor().GetVideoMode()
  		sw := float64(v.Width) / u.glfwScale() / float64(u.width)
  		sh := float64(v.Height) / u.glfwScale() / float64(u.height)
  		s := sw
  		if s > sh {
  			s = sh
  		}
  		u.fullscreenScale = s
  	}
  	return u.fullscreenScale
  }
docs: // getScale must be called from the main thread.