[web] Add support for two finger pan

example/App.tsx

@@ -39,6 +39,7 @@
 import PointerType from './src/release_tests/pointerType';
 import SwipeableReanimation from './src/release_tests/swipeableReanimation';
 import NestedGestureHandlerRootViewWithModal from './src/release_tests/nestedGHRootViewWithModal';
+import TwoFingerPan from 'src/release_tests/twoFingerPan';
 import { PinchableBox } from './src/recipes/scaleAndRotate';
 import PanAndScroll from './src/recipes/panAndScroll';
 import { BottomSheet } from './src/showcase/bottomSheet';
@@ -209,6 +210,11 @@
         unsupportedPlatforms: new Set(['android', 'ios', 'macos']),
       },
       { name: 'Stylus data', component: StylusData },
+      {
+        name: 'Two finger Pan',
+        component: TwoFingerPan,
+        unsupportedPlatforms: new Set(['android', 'macos']),
+      },
     ],
   },
   {
@@ -313,7 +319,7 @@
         renderSectionHeader={({ section: { sectionTitle } }) => (
           <Text style={styles.sectionTitle}>{sectionTitle}</Text>
         )}
         ItemSeparatorComponent={() => <View style={styles.separator} />}
       />
     </SafeAreaView>
   );

example/src/release_tests/twoFingerPan/index.tsx

@@ -0,0 +1,55 @@
+import { StyleSheet, View } from 'react-native';
+import Animated, {
+  useAnimatedStyle,
+  useSharedValue,
+} from 'react-native-reanimated';
+
+import React from 'react';
+import { Gesture, GestureDetector } from 'react-native-gesture-handler';
+
+const BOX_SIZE = 270;
+
+const clampColor = (v: number) => Math.min(255, Math.max(0, v));
+
+export default function TwoFingerPan() {
+  const r = useSharedValue(128);
+  const b = useSharedValue(128);
+
+  const pan = Gesture.Pan()
+    .onChange((event) => {
+      r.value = clampColor(r.value - event.changeY);
+      b.value = clampColor(b.value + event.changeX);
+    })
+    .runOnJS(true)
+    .enableTrackpadTwoFingerGesture(true);
+
+  const animatedStyles = useAnimatedStyle(() => {
+    const backgroundColor = `rgb(${r.value}, 128, ${b.value})`;
+
+    return {
+      backgroundColor,
+    };
+  });
+
+  return (
+    <View style={styles.container} collapsable={false}>
+      <GestureDetector gesture={pan}>
+        <Animated.View style={[styles.box, animatedStyles]} />
+      </GestureDetector>
+    </View>
+  );
+}
+
+const styles = StyleSheet.create({
+  container: {
+    flex: 1,
+    alignItems: 'center',
+    justifyContent: 'center',
+    height: '100%',
+  },
+  box: {
+    width: BOX_SIZE,
+    height: BOX_SIZE,
+    borderRadius: BOX_SIZE / 2,
+  },
+});

src/web/handlers/GestureHandler.ts

@@ -74,6 +74,7 @@ export default abstract class GestureHandler implements IGestureHandler {
     manager.setOnPointerOutOfBounds(this.onPointerOutOfBounds.bind(this));
     manager.setOnPointerMoveOver(this.onPointerMoveOver.bind(this));
     manager.setOnPointerMoveOut(this.onPointerMoveOut.bind(this));
+    manager.setOnWheel(this.onWheel.bind(this));
 
     manager.registerListeners();
   }
@@ -338,7 +339,10 @@ export default abstract class GestureHandler implements IGestureHandler {
   protected onPointerMoveOut(_event: AdaptedEvent): void {
     // Used only by hover gesture handler atm
   }
-  private tryToSendMoveEvent(out: boolean, event: AdaptedEvent): void {
+  protected onWheel(_event: AdaptedEvent): void {
+    // Used only by pan gesture handler
+  }
+  protected tryToSendMoveEvent(out: boolean, event: AdaptedEvent): void {
     if ((out && this.shouldCancelWhenOutside) || !this.enabled) {
       return;
     }

src/web/handlers/PanGestureHandler.ts

@@ -1,6 +1,6 @@
 import { State } from '../../State';
 import { DEFAULT_TOUCH_SLOP } from '../constants';
-import { AdaptedEvent, Config, StylusData } from '../interfaces';
+import { AdaptedEvent, Config, StylusData, WheelDevice } from '../interfaces';
 
 import GestureHandler from './GestureHandler';
 
@@ -57,6 +57,10 @@ export default class PanGestureHandler extends GestureHandler {
   private activateAfterLongPress = 0;
   private activationTimeout = 0;
 
+  private enableTrackpadTwoFingerGesture = false;
+  private endWheelTimeout = 0;
+  private wheelDevice = WheelDevice.UNDETERMINED;
+
   public init(ref: number, propsRef: React.RefObject<unknown>): void {
     super.init(ref, propsRef);
   }
@@ -161,6 +165,11 @@ export default class PanGestureHandler extends GestureHandler {
         this.failOffsetYStart = Number.MIN_SAFE_INTEGER;
       }
     }
+
+    if (this.config.enableTrackpadTwoFingerGesture !== undefined) {
+      this.enableTrackpadTwoFingerGesture =
+        this.config.enableTrackpadTwoFingerGesture;
+    }
   }
 
   protected resetConfig(): void {
@@ -351,6 +360,65 @@ export default class PanGestureHandler extends GestureHandler {
     }
   }
 
+  private scheduleWheelEnd(event: AdaptedEvent) {
+    clearTimeout(this.endWheelTimeout);
+
+    this.endWheelTimeout = setTimeout(() => {
+      if (this.currentState === State.ACTIVE) {
+        this.end();
+        this.tracker.removeFromTracker(event.pointerId);
+        this.currentState = State.UNDETERMINED;
+      }
+
+      this.wheelDevice = WheelDevice.UNDETERMINED;
+    }, 30);
+  }
+
+  protected onWheel(event: AdaptedEvent): void {
+    if (
+      this.wheelDevice === WheelDevice.MOUSE ||
+      !this.enableTrackpadTwoFingerGesture
+    ) {
+      return;
+    }
+
+    if (this.currentState === State.UNDETERMINED) {
+      this.wheelDevice =
+        event.wheelDeltaY! % 120 !== 0
+          ? WheelDevice.TOUCHPAD
+          : WheelDevice.MOUSE;
+
+      if (this.wheelDevice === WheelDevice.MOUSE) {
+        this.scheduleWheelEnd(event);
+        return;
+      }
+
+      this.tracker.addToTracker(event);
+
+      const lastCoords = this.tracker.getAbsoluteCoordsAverage();
+      this.lastX = lastCoords.x;
+      this.lastY = lastCoords.y;
+
+      this.startX = this.lastX;
+      this.startY = this.lastY;
+
+      this.begin();
+      this.activate();
+    }
+    this.tracker.track(event);
+
+    const lastCoords = this.tracker.getAbsoluteCoordsAverage();
+    this.lastX = lastCoords.x;
+    this.lastY = lastCoords.y;
+
+    const velocity = this.tracker.getVelocity(event.pointerId);
+    this.velocityX = velocity.x;
+    this.velocityY = velocity.y;
+
+    this.tryToSendMoveEvent(false, event);
+    this.scheduleWheelEnd(event);
+  }
+
   private shouldActivate(): boolean {
     const dx: number = this.getTranslationX();
 

src/web/interfaces.ts

@@ -78,6 +78,7 @@ export interface Config extends Record<string, ConfigArgs> {
   shouldActivateOnStart?: boolean;
   disallowInterruption?: boolean;
   direction?: Directions;
+  enableTrackpadTwoFingerGesture?: boolean;
 }
 
 type NativeEventArgs = number | State | boolean | undefined;
@@ -151,6 +152,7 @@ export interface AdaptedEvent {
   time: number;
   button?: MouseButton;
   stylusData?: StylusData;
+  wheelDeltaY?: number;
 }
 
 export enum EventTypes {
@@ -171,3 +173,9 @@ export enum TouchEventType {
   UP,
   CANCELLED,
 }
+
+export enum WheelDevice {
+  UNDETERMINED,
+  MOUSE,
+  TOUCHPAD,
+}

src/web/tools/EventManager.ts

@@ -37,6 +37,7 @@ export default abstract class EventManager<T> {
   protected onPointerOutOfBounds(_event: AdaptedEvent): void {}
   protected onPointerMoveOver(_event: AdaptedEvent): void {}
   protected onPointerMoveOut(_event: AdaptedEvent): void {}
+  protected onWheel(_event: AdaptedEvent): void {}
 
   public setOnPointerDown(callback: PointerEventCallback): void {
     this.onPointerDown = callback;
@@ -71,6 +72,9 @@ export default abstract class EventManager<T> {
   public setOnPointerMoveOut(callback: PointerEventCallback): void {
     this.onPointerMoveOut = callback;
   }
+  public setOnWheel(callback: PointerEventCallback): void {
+    this.onWheel = callback;
+  }
 
   protected markAsInBounds(pointerId: number): void {
     if (this.pointersInBounds.indexOf(pointerId) >= 0) {

src/web/tools/GestureHandlerWebDelegate.ts

@@ -11,6 +11,7 @@ import EventManager from './EventManager';
 import { Config } from '../interfaces';
 import { MouseButton } from '../../handlers/gestureHandlerCommon';
 import KeyboardEventManager from './KeyboardEventManager';
+import WheelEventManager from './WheelEventManager';
 
 interface DefaultViewStyles {
   userSelect: string;
@@ -58,6 +59,7 @@ export class GestureHandlerWebDelegate
 
     this.eventManagers.push(new PointerEventManager(this.view));
     this.eventManagers.push(new KeyboardEventManager(this.view));
+    this.eventManagers.push(new WheelEventManager(this.view));
 
     this.eventManagers.forEach((manager) =>
       this.gestureHandler.attachEventManager(manager)

src/web/tools/WheelEventManager.ts

@@ -0,0 +1,48 @@
+import EventManager from './EventManager';
+import { AdaptedEvent, EventTypes } from '../interfaces';
+import { PointerType } from '../../PointerType';
+
+export default class WheelEventManager extends EventManager<HTMLElement> {
+  private wheelDelta = { x: 0, y: 0 };
+
+  private resetDelta = (_event: PointerEvent) => {
+    this.wheelDelta = { x: 0, y: 0 };
+  };
+
+  private wheelCallback = (event: WheelEvent) => {
+    this.wheelDelta.x += event.deltaX;
+    this.wheelDelta.y += event.deltaY;
+
+    const adaptedEvent = this.mapEvent(event);
+    this.onWheel(adaptedEvent);
+  };
+
+  public registerListeners(): void {
+    this.view.addEventListener('pointermove', this.resetDelta);
+    this.view.addEventListener('wheel', this.wheelCallback);
+  }
+
+  public unregisterListeners(): void {
+    this.view.removeEventListener('pointermove', this.resetDelta);
+    this.view.removeEventListener('wheel', this.wheelCallback);
+  }
+
+  protected mapEvent(event: WheelEvent): AdaptedEvent {
+    return {
+      x: event.clientX + this.wheelDelta.x,
+      y: event.clientY + this.wheelDelta.y,
+      offsetX: event.offsetX - event.deltaX,
+      offsetY: event.offsetY - event.deltaY,
+      pointerId: -1,
+      eventType: EventTypes.MOVE,
+      pointerType: PointerType.OTHER,
+      time: event.timeStamp,
+      // @ts-ignore It does exist, but it's deprecated
+      wheelDeltaY: event.wheelDeltaY,
+    };
+  }
+
+  public resetManager(): void {
+    super.resetManager();
+  }
+}