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[iOS] Report zero Pan velocity when the pointer rested before release - #4642
Follow-up to the web fix for #4636, same rule on iOS and macOS.
The Pan handler reports UIKit's velocityInView: in every event, including the end event. That estimate freezes at the last touch move, so a drag that stops, holds still, and then lifts reports the velocity of the drag in onEnd, and a withDecay started from it flings a pointer that had come to rest. Android reports 0 in that case, since its VelocityTracker treats a pointer as stopped after 40 ms without a sample.
RNBetterPanGestureRecognizer now stamps the time of every move and, on release, records whether more than 40 ms passed since the last move. The check runs before the superclass handles the release, because that is where the gesture ends and the action is dispatched. The event payload reads the velocity through reportedVelocityInView:, which returns zero in the ended state after such a rest and UIKit's estimate otherwise. Update events, activation criteria and failure paths are unchanged, and so is a release within 40 ms of the last move.
Test plan
Tested on "Velocity Test" example
iPhone 17 simulator, v3 usePanGesture screen, a 160 px drag in 48 ms driven with argent: released at the last move velocityX 2517, released 19 ms later 2587, released 500 ms later 0 (2657 before the change).
macOS and tvOS share the change and compile the same paths, not run on a device.
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📝 Summary
Summary by CodeRabbit
Bug Fixes
Improved pan gesture velocity reporting when a pointer pauses before release. If no movement is detected for more than a brief interval before release, the reported velocity is now zero; otherwise, the estimated velocity is preserved. This applies to both touch and mouse interactions, helping prevent stale movement from affecting gesture results.
Apple pan recognizers now track the time of the latest movement. When release follows a pause longer than 0.04 seconds, macOS and iOS pan event payloads report zero velocity.
Changes: Apple Pan release velocity
Layer / File(s)
Summary
Track movement and report release velocity packages/react-native-gesture-handler/apple/Handlers/RNPanHandler.m
The recognizer records movement timestamps and checks the pause duration at mouse or touch release. Its velocity helper returns zero after a pause longer than 0.04 seconds. macOS and iOS pan event payloads use the helper, and reset clears the stopped-before-release flag.
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Actionable comments posted: 1
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Inline comments:
Review comments at
@packages/react-native-gesture-handler/apple/Handlers/RNPanHandler.m:
- Around line 145-146: Update the touch-begin handling in RNPanHandler so
_lastMoveTimestamp and _restedBeforeRelease are initialized only when a new
touch sequence starts; preserve both values when UIKit calls
touchesBegan:withEvent: for additional fingers.
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Description
Follow-up to the web fix for #4636, same rule on iOS and macOS.
The Pan handler reports UIKit's
velocityInView:in every event, including the end event. That estimate freezes at the last touch move, so a drag that stops, holds still, and then lifts reports the velocity of the drag inonEnd, and awithDecaystarted from it flings a pointer that had come to rest. Android reports 0 in that case, since itsVelocityTrackertreats a pointer as stopped after 40 ms without a sample.RNBetterPanGestureRecognizernow stamps the time of every move and, on release, records whether more than 40 ms passed since the last move. The check runs before the superclass handles the release, because that is where the gesture ends and the action is dispatched. The event payload reads the velocity throughreportedVelocityInView:, which returns zero in the ended state after such a rest and UIKit's estimate otherwise. Update events, activation criteria and failure paths are unchanged, and so is a release within 40 ms of the last move.Test plan
Tested on "Velocity Test" example
usePanGesturescreen, a 160 px drag in 48 ms driven with argent: released at the last movevelocityX2517, released 19 ms later 2587, released 500 ms later 0 (2657 before the change).