1. A method of performing operations on a computing system having a touch sensitive surface, the method comprising: tracking the paths of multiple distinguishable contacts, the contacts corresponding to touch devices as they move on or near the surface at the same time, wherein tracking is based on at least shape and position data corresponding to the contacts; determining scaling motion information corresponding to two or more of the multiple contacts based on the tracked paths of the contacts; generating a scaling gesture control signal based on the scaling motion information.