message: Initialize renderer primitive properly
diff: @@ -38,9 +38,15 @@ pub trait UserInterface {
  let mut renderer = Renderer::new(&window);
  let mut target = renderer.target(width, height);
  - let mut cache = Some(iced_winit::Cache::default());
  + let user_interface = iced_winit::UserInterface::build(
  + document(&mut self, width, height),
  + iced_winit::Cache::default(),
  + &mut renderer,
  + );
  +
  + let mut primitive = user_interface.draw(&mut renderer);
  + let mut cache = Some(user_interface.into_cache());
  let mut events = Vec::new();
  - let mut primitive = Primitive::None;
  window.request_redraw();
  