Warner Bros. just finished its annual presentation at CinemaCon and yada, yada, yada... Joker looks fucking incredible. That's what I tweeted an hour ago, and I'm standing by that insightful assessment. Don't worry, you're all going to be able to watch the Joker trailer tomorrow, so if you want to go in fresh then stop reading right now. Those who dare to continue, spoilers lie ahead. The trailer, set to Jimmy Durante's "Smile," opens on a happy note, with Joaquin Phoenix explaining to a therapist that his mother always told him to "smile and put …