Add pan gesture animation examples to rntester (facebook#50851)

Summary:
Pull Request resolved: facebook#50851

## Changelog:

[General] [Added] - Add pan gesture animation example to rntester

Including examples of
* using native driven Animated.event + touch event (which will not be interrupted by busy js thread, and is potentially a boost to performance) - the code requires some hacks but it's doable
* using js PanResponder to drive pan gesture animation

Reviewed By: sammy-SC

Differential Revision: D68909931

Author: zeyap

packages/rn-tester/js/examples/Animated/AnimatedIndex.js

@@ -19,6 +19,7 @@ import EasingExample from './EasingExample';
 import FadeInViewExample from './FadeInViewExample';
 import LoopingExample from './LoopingExample';
 import MovingBoxExample from './MovingBoxExample';
+import PanGestureExample from './PanGestureExample';
 import PressabilityWithNativeDrivers from './PressabilityWithNativeDrivers';
 import RotatingImagesExample from './RotatingImagesExample';
 import TransformBounceExample from './TransformBounceExample';
@@ -47,5 +48,6 @@ export default ({
     ContinuousInteractionsExample,
     CombineExample,
     PressabilityWithNativeDrivers,
+    PanGestureExample,
   ],
 }: RNTesterModule);

packages/rn-tester/js/examples/Animated/PanGestureExample.js

@@ -0,0 +1,253 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ * @oncall react_native
+ */
+
+import type {RNTesterModuleExample} from '../../types/RNTesterTypes';
+
+import ToggleNativeDriver from './utils/ToggleNativeDriver';
+import * as React from 'react';
+import {useRef, useState, useLayoutEffect} from 'react';
+import {
+  Animated,
+  Button,
+  PanResponder,
+  StyleSheet,
+  Text,
+  View,
+} from 'react-native';
+
+function TextBox({children}: $ReadOnly<{children: React.Node}>): React.Node {
+  // Prevent touch from being hijacked by Text
+  return (
+    <View pointerEvents="none">
+      <Text style={styles.text}>{children}</Text>
+    </View>
+  );
+}
+
+function AnimatedEventExample({
+  containerPageXY,
+  useNativeDriver,
+}: $ReadOnly<{
+  containerPageXY: $ReadOnly<{x: number, y: number}>,
+  useNativeDriver: boolean,
+}>): React.Node {
+  const boxRef = useRef<?React.ElementRef<typeof Animated.View>>();
+
+  const pointerPageXY = useRef(
+    new Animated.ValueXY(
+      {
+        x: containerPageXY.x,
+        y: containerPageXY.y,
+      },
+      {useNativeDriver},
+    ),
+  ).current;
+
+  const dragStartOffsetXY = useRef(
+    new Animated.ValueXY({x: 0, y: 0}, {useNativeDriver}),
+  ).current;
+
+  const finalOffsetX = Animated.subtract(
+    Animated.subtract(pointerPageXY.x, dragStartOffsetXY.x),
+    containerPageXY.x,
+  );
+  const finalOffsetY = Animated.subtract(
+    Animated.subtract(pointerPageXY.y, dragStartOffsetXY.y),
+    containerPageXY.y,
+  );
+
+  const syncAnimationToHostView = () => {
+    boxRef.current?.setNativeProps({
+      transform: [
+        {translateX: finalOffsetX.__getValue()},
+        {translateY: finalOffsetY.__getValue()},
+      ],
+    });
+  };
+
+  return (
+    <Animated.View
+      ref={boxRef}
+      onTouchMove={Animated.event(
+        [
+          {
+            nativeEvent: {
+              pageX: pointerPageXY.x,
+              pageY: pointerPageXY.y,
+            },
+          },
+        ],
+        {useNativeDriver},
+      )}
+      onTouchStart={Animated.event(
+        [
+          {
+            nativeEvent: {
+              pageX: pointerPageXY.x,
+              pageY: pointerPageXY.y,
+              locationX: dragStartOffsetXY.x,
+              locationY: dragStartOffsetXY.y,
+            },
+          },
+        ],
+        {useNativeDriver},
+      )}
+      onTouchEnd={() => {
+        // Animated change sometimes doesn't commit to Fabric, and box will jump back to offset before animation
+        // This is to make sure that finalOffsetX/Y are synced to native host view
+        syncAnimationToHostView();
+      }}
+      style={[
+        styles.box,
+        {
+          backgroundColor: useNativeDriver ? 'orange' : 'violet',
+          transform: [
+            {
+              translateX: finalOffsetX,
+            },
+            {
+              translateY: finalOffsetY,
+            },
+          ],
+        },
+      ]}>
+      <TextBox>Use {useNativeDriver ? 'Native' : 'JS'} Animated.event</TextBox>
+    </Animated.View>
+  );
+}
+
+function PanResponderExample({
+  useNativeDriver,
+}: $ReadOnly<{useNativeDriver: boolean}>): React.Node {
+  const finalOffsetXY = useRef(
+    new Animated.ValueXY({x: 0, y: 0}, {useNativeDriver}),
+  ).current;
+  const dragStartOffsetXY = useRef({x: 0, y: 0}).current;
+  const panResponder = useRef(
+    PanResponder.create({
+      onMoveShouldSetPanResponder: (pressEvent, gestureState) => {
+        dragStartOffsetXY.x = finalOffsetXY.x.__getValue();
+        dragStartOffsetXY.y = finalOffsetXY.y.__getValue();
+        return true;
+      },
+      onPanResponderMove: (pressEvent, gestureState) => {
+        if (gestureState.dx !== 0) {
+          finalOffsetXY.x.setValue(dragStartOffsetXY.x + gestureState.dx);
+        }
+
+        if (gestureState.dy !== 0) {
+          finalOffsetXY.y.setValue(dragStartOffsetXY.y + gestureState.dy);
+        }
+      },
+    }),
+  ).current;
+
+  return (
+    <Animated.View
+      {...panResponder.panHandlers}
+      style={[
+        styles.box,
+        {
+          backgroundColor: useNativeDriver ? 'pink' : 'cyan',
+          transform: [
+            {
+              translateX: finalOffsetXY.x,
+            },
+            {
+              translateY: finalOffsetXY.y,
+            },
+          ],
+        },
+      ]}>
+      <TextBox>
+        Use PanResponder{' '}
+        {`+ ${useNativeDriver ? 'Native Animated value' : 'JS Animated value'}`}
+      </TextBox>
+    </Animated.View>
+  );
+}
+
+function PanGestureExample(): React.Node {
+  const [busy, setBusy] = useState(false);
+  const [useNativeDriver, setUseNativeDriver] = useState(false);
+
+  const containerRef = useRef<?React.ElementRef<typeof View>>();
+  const [containerPageXY, setContainerPageXY] =
+    useState<?{x: number, y: number}>(null);
+
+  useLayoutEffect(() => {
+    containerRef.current?.measure((x, y, width, height, pageX, pageY) => {
+      setContainerPageXY({x: pageX, y: pageY});
+    });
+  }, []);
+
+  function sleep(t: number) {
+    setBusy(true);
+    setTimeout(() => {
+      const start = Date.now();
+      while (Date.now() - start < t) {
+        // sleeping
+      }
+      setBusy(false);
+    }, 1000);
+  }
+
+  return (
+    <View style={styles.container}>
+      <ToggleNativeDriver
+        value={useNativeDriver}
+        onValueChange={setUseNativeDriver}
+      />
+      <Button
+        title={busy ? 'js thread blocked...' : 'Block js thread for 5s'}
+        onPress={() => {
+          sleep(5000);
+        }}
+      />
+      <View style={styles.examplesContainer} ref={containerRef}>
+        {containerPageXY != null ? (
+          <AnimatedEventExample
+            useNativeDriver={useNativeDriver}
+            containerPageXY={containerPageXY}
+          />
+        ) : null}
+        <PanResponderExample useNativeDriver={useNativeDriver} />
+      </View>
+    </View>
+  );
+}
+
+const styles = StyleSheet.create({
+  container: {
+    alignItems: 'stretch',
+    justifyContent: 'flex-start',
+  },
+  examplesContainer: {
+    flex: 1,
+  },
+  box: {
+    width: 160,
+    height: 160,
+    alignItems: 'center',
+    justifyContent: 'center',
+    padding: 12,
+  },
+  text: {
+    pointerEvents: 'none',
+  },
+});
+
+export default ({
+  title: 'Pan Gesture',
+  name: 'panGesture',
+  description: 'Animations driven by pan gesture.',
+  render: () => <PanGestureExample />,
+}: RNTesterModuleExample);