[General] Schedule flushes instead of flushing immediately

[j-piasecki]

Description

Currently, when creating a gesture or configuring relations, flushOperations is called immediately. When rendering multiple detectors in the same batch, this adds unnecessary overhead as it can be done a single time at the end of the batch. This PR changes that.

I also noticed that createGestureHandler is scheduled on the UI anyway, so I figured there may be no point in keeping it synchronous.

Test plan

Used this stress test to measure impact:

import React, { Profiler, useEffect, useRef } from 'react';
import { ScrollView, StyleSheet, View } from 'react-native';
import { GestureDetector, usePan } from 'react-native-gesture-handler';
import Animated, {
  useAnimatedStyle,
  useSharedValue,
} from 'react-native-reanimated';

const DATA = new Array(500).fill(null).map((_, i) => `Item ${i + 1}`);

function Item() {
  const translateX = useSharedValue(0);

  const style = useAnimatedStyle(() => {
    return {
      transform: [{ translateX: translateX.value }],
    };
  });

  const pan = usePan({
    onUpdate: (event) => {
      'worklet';
      translateX.value += event.handlerData.changeX;
    },
  });

  return (
    <View style={{ height: 80, padding: 16, backgroundColor: 'gray' }}>
      <GestureDetector gesture={pan}>
        {/* <View collapsable={false} style={{opacity: 0.5}}> */}
        <Animated.View
          style={[
            { backgroundColor: 'red', height: '100%', aspectRatio: 1 },
            style,
          ]}
        />
        {/* </View> */}
      </GestureDetector>
    </View>
  );
}

function Benchmark() {
  return (
    <ScrollView
      style={{ flex: 1 }}
      contentContainerStyle={{ flexGrow: 1, gap: 8 }}>
      {DATA.map((_, index) => (
        <Item key={index} />
      ))}
    </ScrollView>
  );
}

const TIMES = 30;

export default function EmptyExample() {
  const times = useRef<number[]>([]).current;
  const [visible, setVisible] = React.useState(false);

  useEffect(() => {
    if (!visible && times.length < TIMES) {
      setTimeout(() => {
        setVisible(true);
      }, 24);
    }

    if (times.length === TIMES) {
      // calculate average, but remove highest and lowest
      const sortedTimes = [...times].sort((a, b) => a - b);
      sortedTimes.shift();
      sortedTimes.pop();
      const avgTime =
        sortedTimes.reduce((sum, time) => sum + time, 0) / sortedTimes.length;

      console.log(`Average render time: ${avgTime} ms`);
    }
  }, [visible]);

  return (
    <View style={styles.container}>
      {visible && (
        <Profiler
          id="v3"
          onRender={(_id, _phase, actualDuration) => {
            times.push(actualDuration);
            setTimeout(() => {
              setVisible(false);
            }, 24);
          }}>
          <Benchmark />
        </Profiler>
      )}
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
  },
});

I saw the average time fall from ~610ms to ~595ms.

[m-bert]

Suggested change

	// It's possible that this can cause errors about handler not being created when attemting to mound NativeDetector
	// It's possible that this can cause errors about handler not being created when attempting to mount NativeDetector

[m-bert]

Also, isn't it connected with the error that I've shown you offline? The one when app would sometimes crash on startup because handler has not yet been created?

[j-piasecki]

I don't know - it cannot be the cause, since it wasn't there when you found it, but I also was able to reproduce that only by modifying RNGH source while the app was running.