I don't recall the outcome of that "Apple claims ownership of rounded corners" lawsuit, but I suspect (being absolutely not a lawyer) that'd be the relevant case law.
This really depends on the Google v Oracle lawsuit currently. If Oracle wins then the remains of VisCalc will have a copyright claim against everyone...
Microsoft successfully sued Corel for design patent infringement related to the ribbon interface. Corel had a “Word mode” in WordPerfect X7. The damages were about a quarter million dollars. YMMV.
Oracle v Google is copyright as applied to API’s. Different laws. Patents expire more quickly.