[iOS] Report zero Pan velocity when the pointer rested before release (#4642)

## 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 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.

Author: m-bert

packages/react-native-gesture-handler/apple/Handlers/RNPanHandler.m

@@ -37,11 +37,18 @@ @interface RNBetterPanGestureRecognizer : UIPanGestureRecognizer
 #endif
 
 - (id)initWithGestureHandler:(RNGestureHandler *)gestureHandler;
+- (CGPoint)reportedVelocityInView:(RNGHUIView *)view;
 
 @end
 
+// A pointer that sent no move for this long is treated as stopped, like in
+// Android's VelocityTracker and the web tracker.
+static const NSTimeInterval pointerStoppedInterval = 0.04;
+
 @implementation RNBetterPanGestureRecognizer {
   __weak RNGestureHandler *_gestureHandler;
+  NSTimeInterval _lastMoveTimestamp;
+  BOOL _restedBeforeRelease;
 #if TARGET_OS_OSX
   BOOL _blockAutomaticActivation;
 #else
@@ -135,6 +142,11 @@ - (void)interactionsBegan:(NSSet *)touches withEvent:(UIEvent *)event
     [_gestureHandler reset];
   }
 
+  if (self.state == UIGestureRecognizerStatePossible) {
+    _lastMoveTimestamp = event.timestamp;
+    _restedBeforeRelease = NO;
+  }
+
 #if !TARGET_OS_TV && !TARGET_OS_OSX
   if (_hasCustomActivationCriteria) {
     // We use "minimumNumberOfTouches" property to prevent pan handler from recognizing
@@ -169,6 +181,7 @@ - (void)interactionsBegan:(NSSet *)touches withEvent:(UIEvent *)event
 
 - (void)interactionsMoved:(NSSet *)touches withEvent:(UIEvent *)event
 {
+  _lastMoveTimestamp = event.timestamp;
   [_gestureHandler.pointerTracker touchesMoved:touches withEvent:event];
 
   if (self.state == UIGestureRecognizerStatePossible && [self shouldFailUnderCustomCriteria]) {
@@ -212,6 +225,13 @@ - (void)interactionsMoved:(NSSet *)touches withEvent:(UIEvent *)event
 #endif
 }
 
+// Velocity for the event payload: zero on release when the pointer rested
+// before lifting, the recognizer's estimate otherwise.
+- (CGPoint)reportedVelocityInView:(RNGHUIView *)view
+{
+  return self.state == UIGestureRecognizerStateEnded && _restedBeforeRelease ? CGPointZero : [self velocityInView:view];
+}
+
 - (void)interactionsEnded:(NSSet *)touches withEvent:(UIEvent *)event
 {
   [_gestureHandler.pointerTracker touchesEnded:touches withEvent:event];
@@ -264,6 +284,8 @@ - (void)mouseDragged:(NSEvent *)event
 
 - (void)mouseUp:(NSEvent *)event
 {
+  _restedBeforeRelease = event.timestamp - _lastMoveTimestamp > pointerStoppedInterval;
+
   [super mouseUp:event];
   [self interactionsEnded:[NSSet setWithObject:event] withEvent:event];
 }
@@ -286,6 +308,8 @@ - (void)touchesMoved:(NSSet<RNGHUITouch *> *)touches withEvent:(UIEvent *)event
 
 - (void)touchesEnded:(NSSet<RNGHUITouch *> *)touches withEvent:(UIEvent *)event
 {
+  _restedBeforeRelease = event.timestamp - _lastMoveTimestamp > pointerStoppedInterval;
+
   [super touchesEnded:touches withEvent:event];
   [self interactionsEnded:touches withEvent:event];
 }
@@ -306,6 +330,7 @@ - (void)reset
 #if TARGET_OS_OSX
   _blockAutomaticActivation = NO;
 #endif
+  _restedBeforeRelease = NO;
   [super reset];
   [_gestureHandler reset];
 
@@ -486,13 +511,16 @@ - (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
 #if TARGET_OS_OSX
 - (RNGestureHandlerEventExtraData *)eventExtraData:(NSPanGestureRecognizer *)recognizer
 {
-  return [RNGestureHandlerEventExtraData forPan:[recognizer locationInView:self.coordinateView]
-                           withAbsolutePosition:[recognizer locationInView:recognizer.view.window.contentView]
-                                withTranslation:[recognizer translationInView:recognizer.view.window.contentView]
-                                   withVelocity:[recognizer velocityInView:recognizer.view.window.contentView]
-                            withNumberOfTouches:1
-                                withPointerType:RNGestureHandlerMouse
-                                 withStylusData:nil];
+  RNBetterPanGestureRecognizer *panRecognizer = (RNBetterPanGestureRecognizer *)recognizer;
+
+  return
+      [RNGestureHandlerEventExtraData forPan:[recognizer locationInView:self.coordinateView]
+                        withAbsolutePosition:[recognizer locationInView:recognizer.view.window.contentView]
+                             withTranslation:[recognizer translationInView:recognizer.view.window.contentView]
+                                withVelocity:[panRecognizer reportedVelocityInView:recognizer.view.window.contentView]
+                         withNumberOfTouches:1
+                             withPointerType:RNGestureHandlerMouse
+                              withStylusData:nil];
 }
 #else
 - (RNGestureHandlerEventExtraData *)eventExtraData:(UIPanGestureRecognizer *)recognizer
@@ -503,7 +531,7 @@ - (RNGestureHandlerEventExtraData *)eventExtraData:(UIPanGestureRecognizer *)rec
                     forPan:[recognizer locationInView:self.coordinateView]
       withAbsolutePosition:[recognizer locationInView:recognizer.view.window]
            withTranslation:[recognizer translationInView:recognizer.view.window]
-              withVelocity:[recognizer velocityInView:recognizer.view.window]
+              withVelocity:[panRecognizer reportedVelocityInView:recognizer.view.window]
        withNumberOfTouches:recognizer.numberOfTouches
            withPointerType:_pointerType
 #if !TARGET_OS_TV