There was a case a few years ago, down in engerlund, where the attacking team put a man on the post when taking direct free kicks. Plan was ,when the ball was struck towards the area of goal occupied by him , he would simply move out the way of the ball.Their argument was that as the player had no intention of playing the ball therefore was not "active".
IIRC , the powers deemed that his presence was an unfair distraction on the keeper & therefore hes offside. I would have thought anyone blocking the keepers view while in an offside position as you described would have to be flagged as offside.
But then again , sometimes i feel the officials dont even know how to interpret their own rules.