LOS ANGELES—Best actor nominee Will Smith smacked presenter Chris Rock in the face with an open hand and shouted a vulgarity at the comedian for making a joke about his wife’s appearance at the Oscars ceremony on Sunday. Minutes later, when accepting the Oscar for best actor for his role in “King Richard,” Smith apologized to the Academy of Motion Picture Arts and Sciences and his fellow nominees but not to Rock. The episode with Rock at first appeared to be a scripted joke but turned serious when Smith shouted out, “Keep my wife’s name out of your [expletive] mouth.” The audio from the show, broadcast on a time-delay of a few seconds in the United States, appeared to have been cut from the live transmission for many viewers because of the language. Rock was roasting some of the nominees and, after mentioning Smith, said of his wife, Jada Pinkett …