public signal void begin (EventSequence? sequence)
This signal is emitted when the gesture is recognized.
This means the number of touch sequences matches n_points, and the
GtkGesture::check handler(s) returned
Note: These conditions may also happen when an extra touch (eg. a third touch on a 2-touches gesture) is lifted, in that situation
sequence won't pertain to the current set of active touches, so don't rely on this being true.
the EventSequence that made the gesture to be recognized