react-native-gesture-handler/lib/module/v3/hooks/useJSResponderHandler.js

Declarative API exposing native platform touch and gesture system to React Native

"use strict";

import { use, useCallback, useEffect, useRef, useState } from 'react';
import { Reanimated } from '../../handlers/gestures/reanimatedWrapper';
import { JSResponderContext, updateResponderEventValue } from '../components/ScrollViewResponderInterceptor';
import { SingleGestureName } from '../types';
import { isComposedGesture, isGestureEnabled } from './utils';
import { getEnabledSharedValues, SHARED_VALUE_OFFSET } from './utils/reanimatedUtils';

// adding 0.5 to not call Math.random and to make sure that listener ID is not an integer to avoid conflicts
let nextJSResponderContextListenerId = SHARED_VALUE_OFFSET + 0.5;
function isSupportedGesture(gesture) {
  if (isComposedGesture(gesture)) {
    return gesture.gestures.some(isSupportedGesture);
  }
  switch (gesture.type) {
    case SingleGestureName.Tap:
    case SingleGestureName.LongPress:
    case SingleGestureName.Fling:
    case SingleGestureName.Native:
    case SingleGestureName.Hover:
      return true;
    default:
      return false;
  }
}
export function useJSResponderHandler(gesture) {
  const jsResponderContext = use(JSResponderContext);
  const [enabledSharedValueRevision, setEnabledSharedValueRevision] = useState(0);
  const listenerIdRef = useRef(null);
  if (listenerIdRef.current === null) {
    listenerIdRef.current = nextJSResponderContextListenerId++;
  }
  useEffect(() => {
    const reanimated = Reanimated;
    const enabledSharedValues = getEnabledSharedValues(gesture);
    if (reanimated === undefined || enabledSharedValues.length === 0) {
      return;
    }
    const listenerId = listenerIdRef.current;
    if (listenerId === null) {
      return;
    }
    const {
      runOnJS
    } = reanimated;
    const notifyEnabledChanged = () => {
      setEnabledSharedValueRevision(revision => revision + 1);
    };
    const attachListeners = (sharedValues, id, notify) => {
      'worklet';

      const listener = runOnJS(notify);
      for (const sharedValue of sharedValues) {
        sharedValue.addListener(id, listener);
      }
    };
    const detachListeners = (sharedValues, id) => {
      'worklet';

      for (const sharedValue of sharedValues) {
        sharedValue.removeListener(id);
      }
    };
    reanimated.runOnUI(attachListeners)(enabledSharedValues, listenerId, notifyEnabledChanged);
    return () => {
      reanimated.runOnUI(detachListeners)(enabledSharedValues, listenerId);
    };
  }, [gesture]);
  const shouldHandleJSResponderEvent = useCallback(() => {
    void enabledSharedValueRevision;
    return isGestureEnabled(gesture) && isSupportedGesture(gesture);
  }, [enabledSharedValueRevision, gesture]);
  const handleStartShouldSetResponder = useCallback(() => {
    if (shouldHandleJSResponderEvent()) {
      updateResponderEventValue(jsResponderContext, true);
    }
    return false;
  }, [jsResponderContext, shouldHandleJSResponderEvent]);
  return {
    handleStartShouldSetResponder: jsResponderContext == null ? () => false : handleStartShouldSetResponder
  };
}
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