[megaman821]

What is the patent office's mandate? It is not to grant trivial patents so companies can sue each other. Patents are supposed to be preferable to trade secrets because they make knowledge public in exchange for certain protections, and they encourage innovation in fields that require heavy investment.

It would not matter if slide-to-unlock remained a "trade secret" and the investment in making that feature is low enough that they would do it, even if they were never granted patent protection.