kTouchSlop top-level constant

const kTouchSlop = 18.0

The distance a touch has to travel for the framework to be confident that the gesture is a scroll gesture, or, inversely, the maximum distance that a touch can travel before the framework becomes confident that it is not a tap.

A total delta less than or equal to kTouchSlop is not considered to be a drag, whereas if the delta is greater than kTouchSlop it is considered to be a drag.

Implementation

const double kTouchSlop = 18.0