Allow caller to activate the input handling.
Allow caller to activate the input handling.

This results in better interaction with screens, such that a single interface
instance manages the UI for a screen and is activated and deactivated as
needed.

tomfisher/tripleplay,tomfisher/tripleplay,joansmith/tripleplay,joansmith/tripleplay,joansmith/tripleplay,tomfisher/tripleplay,joansmith/tripleplay,joansmith/tripleplay,tomfisher/tripleplay,tomfisher/tripleplay