[macOS] Fix Pan activation criteria being ignored (#4387)

On macOS, all of `Pan`'s custom activation criteria — `minDistance`,
`activeOffsetX/Y`, `minVelocity(X/Y)` — were silently ignored: the
handler activated the moment the mouse button went down.

Two things combined to cause this:

1. Both custom-activation code paths in `RNPanHandler.m` were compiled
out for macOS. The early-activation guard in `interactionsBegan` and the
`shouldActivateUnderCustomCriteria` check in `interactionsMoved` were
wrapped in `#if !TARGET_OS_TV && !TARGET_OS_OSX`, so the config values
were stored but never evaluated. (Only the fail criteria worked —
`shouldFailUnderCustomCriteria` runs unconditionally.)
2. `NSPanGestureRecognizer` begins on mouse-down. Unlike
`UIPanGestureRecognizer`, which has a built-in ~10 pt hysteresis, the
AppKit recognizer transitions to `Began` immediately, so without the
check there is nothing preventing a click from activating the handler.

The iOS implementation holds the recognizer back with the
`minimumNumberOfTouches = 20` trick, which has no AppKit equivalent.
Instead, on macOS the recognizer is held in the `Possible` state
explicitly:

- When a mouse-down arrives and custom activation criteria are
configured, a `_blockAutomaticActivation` flag is set.
- A `setState:` override swallows the superclass's `Began`/`Changed`
transitions while the flag is up. The superclass keeps receiving events,
so `translationInView:` / `velocityInView:` stay valid — which also
keeps `failOffsetX/Y` and the JS event payload working.
- `interactionsMoved` now evaluates `shouldActivateUnderCustomCriteria`
on macOS and, once it passes, clears the flag, sets `Began` and resets
the translation to zero — same semantics as iOS/Android (translation
counts from the activation point).
- A mouse-up before the criteria are met arrives at `setState:` as
`Ended` and is rewritten to `Failed`, so the gesture finalizes correctly
(`onFinalize` with `canceled=true`).
- The flag is cleared in `reset` and in `activateAfterLongPress` (which
already forces `minDistSq >= 100`, so the block is active while waiting
for the long-press timer).

<details>
<summary>Tested on the following code:</summary>

```tsx
import React from 'react';
import { StyleSheet, Text, View } from 'react-native';
import { GestureDetector, usePanGesture } from 'react-native-gesture-handler';

export default function EmptyExample() {
  const minDistPan = usePanGesture({
    minDistance: 50,
    onBegin: () => console.log('[minDist] onBegin'),
    onActivate: (e) =>
      console.log(`[minDist] onActivate tx=${e.translationX.toFixed(1)} ty=${e.translationY.toFixed(1)}`),
    onDeactivate: () => console.log('[minDist] onDeactivate'),
    onFinalize: (e) => console.log(`[minDist] onFinalize canceled=${e.canceled}`),
  });

  const activeOffsetPan = usePanGesture({
    activeOffsetX: [-50, 50],
    onBegin: () => console.log('[activeOffsetX] onBegin'),
    onActivate: (e) =>
      console.log(`[activeOffsetX] onActivate tx=${e.translationX.toFixed(1)} ty=${e.translationY.toFixed(1)}`),
    onDeactivate: () => console.log('[activeOffsetX] onDeactivate'),
    onFinalize: (e) => console.log(`[activeOffsetX] onFinalize canceled=${e.canceled}`),
  });

  const minVelocityPan = usePanGesture({
    minVelocity: 800,
    onBegin: () => console.log('[minVelocity] onBegin'),
    onActivate: (e) =>
      console.log(`[minVelocity] onActivate tx=${e.translationX.toFixed(1)} ty=${e.translationY.toFixed(1)}`),
    onDeactivate: () => console.log('[minVelocity] onDeactivate'),
    onFinalize: (e) => console.log(`[minVelocity] onFinalize canceled=${e.canceled}`),
  });

  return (
    <View style={styles.container}>
      <Text style={styles.label}>minDistance: 50</Text>
      <GestureDetector gesture={minDistPan}>
        <View style={[styles.box, { backgroundColor: 'tomato' }]} />
      </GestureDetector>

      <Text style={styles.label}>activeOffsetX: [-50, 50]</Text>
      <GestureDetector gesture={activeOffsetPan}>
        <View style={[styles.box, { backgroundColor: 'mediumseagreen' }]} />
      </GestureDetector>

      <Text style={styles.label}>minVelocity: 800</Text>
      <GestureDetector gesture={minVelocityPan}>
        <View style={[styles.box, { backgroundColor: 'steelblue' }]} />
      </GestureDetector>
    </View>
  );
}

const styles = StyleSheet.create({
  container: { flex: 1, justifyContent: 'center', alignItems: 'center', gap: 8 },
  label: { marginTop: 16, fontSize: 15, opacity: 0.6 },
  box: { width: 140, height: 140, borderRadius: 12 },
});
```

</details>

Author: m-bert

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

@@ -42,7 +42,9 @@ - (id)initWithGestureHandler:(RNGestureHandler *)gestureHandler;
 
 @implementation RNBetterPanGestureRecognizer {
   __weak RNGestureHandler *_gestureHandler;
-#if !TARGET_OS_OSX
+#if TARGET_OS_OSX
+  BOOL _blockAutomaticActivation;
+#else
   NSUInteger _realMinimumNumberOfTouches;
 #endif
   BOOL _hasCustomActivationCriteria;
@@ -114,6 +116,9 @@ - (void)tryUpdateStylusData:(UIEvent *)event
 
 - (void)activateAfterLongPress
 {
+#if TARGET_OS_OSX
+  _blockAutomaticActivation = NO;
+#endif
   self.state = UIGestureRecognizerStateBegan;
   // Send event in ACTIVE state because UIGestureRecognizerStateBegan is mapped to RNGestureHandlerStateBegan
   [_gestureHandler handleGesture:self inState:RNGestureHandlerStateActive];
@@ -139,6 +144,11 @@ - (void)interactionsBegan:(NSSet *)touches withEvent:(UIEvent *)event
 #endif
 
 #if TARGET_OS_OSX
+  // NSPanGestureRecognizer transitions to the Began state on mouse-down, without any
+  // built-in movement hysteresis. To honor the custom activation criteria (minDist,
+  // activeOffsets, minVelocity) we hold the recognizer in the Possible state until
+  // they are met in interactionsMoved.
+  _blockAutomaticActivation = _hasCustomActivationCriteria;
   [super mouseDown:event];
 #else
   [super touchesBegan:touches withEvent:event];
@@ -176,7 +186,14 @@ - (void)interactionsMoved:(NSSet *)touches withEvent:(UIEvent *)event
     }
   }
 
-#if !TARGET_OS_TV && !TARGET_OS_OSX
+#if TARGET_OS_OSX
+  if (_hasCustomActivationCriteria && self.state == UIGestureRecognizerStatePossible &&
+      [self shouldActivateUnderCustomCriteria]) {
+    _blockAutomaticActivation = NO;
+    self.state = UIGestureRecognizerStateBegan;
+    [self setTranslation:CGPointMake(0, 0) inView:self.view];
+  }
+#elif !TARGET_OS_TV
   if (_hasCustomActivationCriteria && self.state == UIGestureRecognizerStatePossible &&
       [self shouldActivateUnderCustomCriteria]) {
     super.minimumNumberOfTouches = _realMinimumNumberOfTouches;
@@ -209,6 +226,23 @@ - (void)interactionsCancelled:(NSSet *)touches withEvent:(UIEvent *)event
 
 #if TARGET_OS_OSX
 
+- (void)setState:(NSGestureRecognizerState)state
+{
+  if (_blockAutomaticActivation) {
+    if (state == NSGestureRecognizerStateBegan || state == NSGestureRecognizerStateChanged) {
+      // Hold the recognizer in the Possible state until the custom activation criteria
+      // are met — the superclass keeps tracking the mouse regardless, so translation
+      // and velocity stay valid for the criteria checks.
+      return;
+    }
+    if (state == NSGestureRecognizerStateEnded) {
+      // Mouse released before the activation criteria were met — the gesture failed.
+      state = NSGestureRecognizerStateFailed;
+    }
+  }
+  [super setState:state];
+}
+
 - (void)mouseDown:(NSEvent *)event
 {
   [_gestureHandler setCurrentPointerTypeToMouse];
@@ -265,6 +299,9 @@ - (void)reset
   [_gestureHandler.pointerTracker reset];
   [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(activateAfterLongPress) object:nil];
   self.enabled = YES;
+#if TARGET_OS_OSX
+  _blockAutomaticActivation = NO;
+#endif
   [super reset];
   [_gestureHandler reset];