Description:

Grail consists of an interface and tools for handling gesture
recognition and gesture instantiation.

When a multitouch gesture is performed on a device, the recognizer
emits one or several possible gestures. Once the context of the
gesture is known, i.e., in what window the touches land and what
gestures the clients of that window listen to, the instantiator
delivers the matching set of gestures.

The library handles tentative getures, i.e., buffering of events for
several alternative gestures until a match is confirmed.