Issue 691 interact mac broken

@dlonie @aashish24 please review and feel free to suggest better/cleaner solutions.
@ThomasMaxwell wouldn't mind you looking this over as well and testing it against DV3D.

But *what* is being redone? Just seeing "redo" in a complex codebase doesn't really give another developer any idea what the variable is for -- always check through  patches for clarity like you're reading the code for the first time -- everyone else will have to ;)