1. A method of determining input events of a computing system having a touch sensing surface, the method comprising: tracking multiple distinguishable contacts, the contacts corresponding to touch devices concurrently on or near the surface, wherein motion of a first contact and motion of a second contact are tracked in a first period during which the first and second contacts remain touched down on the surface; detecting a liftoff of the first contact from the surface while the second contact remains touched down on the surface, wherein the motion of the second contact continues to be tracked during a second period after the liftoff of the first contact; and determining at least two input events, including determining a first input event during the first period and determining a second input event during the second period, wherein the first input event corresponds to the tracked motion of the first contact and is not based on the tracked motion of the second contact which is not stationary, and the second input event corresponds to the tracked motion of the second contact.