INTERPRETING GESTURE INPUT INCLUDING INTRODUCTION OR REMOVAL OF A POINT OF CONTACT WHILE A GESTURE IS IN PROGRESS

摘要

A touch-sensitive device accepts single-touch and multi-touch input representing gestures, and can change a parameter of a gesture responsive to introduction or removal of a point of contact while the gesture is in progress. The operation associated with the gesture, such as a manipulation of an on-screen object, changes in a predictable manner if the user introduces or removes a contact point while the gesture is in progress. The overall nature of the operation being performed does not change, but a parameter of the operation can change. In various embodiments, each time a contact point is added or removed, the system and method of the present invention resets the relationship between the contact point locations and the operation being performed, so as to avoid or minimize discontinuities in the operation. In this manner, the invention avoids sudden or unpredictable changes to an object being manipulated.