A pointer went up: a drag flings on (a finger or pen) or snaps (paged modes), a quick touch is a tap and two taps close together toggle the zoom; ending a pinch snaps to fit-width or fit-page when the zoom is within 5 % of it, and the other finger drags on.
public void PointerUp(long pointerId, double x, double y)
The pointer's identifier.
The x in device-independent pixels.
The y in device-independent pixels.
Spec #33 viewer capability 14.