Track the range offsets along the timeline where previous/current/next is

Also, let you specify this as options. This lets you model more than three
states along a timeline by clamping them.

It also allows specifying the "current" offset as something different than
what it was when the gesture started such as if it has to start scroll has
already happened.

Author: sebmarkbage

packages/react-art/src/ReactFiberConfigART.js

@@ -510,8 +510,13 @@ export function createViewTransitionInstance(
 
 export type GestureTimeline = null;
 
+export function getCurrentGestureOffset(provider: GestureTimeline): number {
+  throw new Error('useSwipeTransition is not yet supported in react-art.');
+}
+
 export function subscribeToGestureDirection(
   provider: GestureTimeline,
+  currentOffset: number,
   directionCallback: (direction: boolean) => void,
 ): () => void {
   throw new Error('useSwipeTransition is not yet supported in react-art.');

packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js

@@ -1480,17 +1480,21 @@ export function createViewTransitionInstance(
 
 export type GestureTimeline = AnimationTimeline; // TODO: More provider types.
 
-export function subscribeToGestureDirection(
-  provider: GestureTimeline,
-  directionCallback: (direction: boolean) => void,
-): () => void {
+export function getCurrentGestureOffset(provider: GestureTimeline): number {
   const time = provider.currentTime;
   if (time === null) {
     throw new Error(
       'Cannot start a gesture with a disconnected AnimationTimeline.',
     );
   }
-  const startTime = typeof time === 'number' ? time : time.value;
+  return typeof time === 'number' ? time : time.value;
+}
+
+export function subscribeToGestureDirection(
+  provider: GestureTimeline,
+  currentOffset: number,
+  directionCallback: (direction: boolean) => void,
+): () => void {
   if (
     typeof ScrollTimeline === 'function' &&
     provider instanceof ScrollTimeline
@@ -1502,8 +1506,8 @@ export function subscribeToGestureDirection(
       if (newTime !== null) {
         directionCallback(
           typeof newTime === 'number'
-            ? newTime > startTime
-            : newTime.value > startTime,
+            ? newTime > currentOffset
+            : newTime.value > currentOffset,
         );
       }
     };
@@ -1519,8 +1523,8 @@ export function subscribeToGestureDirection(
       if (newTime !== null) {
         directionCallback(
           typeof newTime === 'number'
-            ? newTime > startTime
-            : newTime.value > startTime,
+            ? newTime > currentOffset
+            : newTime.value > currentOffset,
         );
       }
       callbackID = requestAnimationFrame(rafCallback);

packages/react-native-renderer/src/ReactFiberConfigNative.js

@@ -607,8 +607,13 @@ export function createViewTransitionInstance(
 
 export type GestureTimeline = null;
 
+export function getCurrentGestureOffset(provider: GestureTimeline): number {
+  throw new Error('useSwipeTransition is not yet supported in React Native.');
+}
+
 export function subscribeToGestureDirection(
   provider: GestureTimeline,
+  currentOffset: number,
   directionCallback: (direction: boolean) => void,
 ): () => void {
   throw new Error('useSwipeTransition is not yet supported in React Native.');

packages/react-noop-renderer/src/createReactNoop.js

@@ -796,8 +796,13 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
           return null;
         },
 
+        getCurrentGestureOffset(provider: GestureTimeline): number {
+          return 0;
+        },
+
         subscribeToGestureDirection(
           provider: GestureTimeline,
+          currentOffset: number,
           directionCallback: (direction: boolean) => void,
         ): () => void {
           return () => {};

packages/react-reconciler/src/ReactFiberConfigWithNoMutation.js

@@ -49,4 +49,5 @@ export const startViewTransition = shim;
 export type ViewTransitionInstance = null | {name: string, ...};
 export const createViewTransitionInstance = shim;
 export type GestureTimeline = any;
+export const getCurrentGestureOffset = shim;
 export const subscribeToGestureDirection = shim;

packages/react-reconciler/src/ReactFiberGestureScheduler.js

@@ -19,6 +19,9 @@ export type ScheduledGesture = {
   provider: GestureTimeline,
   count: number, // The number of times this same provider has been started.
   direction: boolean, // false = previous, true = next
+  rangePrevious: number, // The end along the timeline where the previous state is reached.
+  rangeCurrent: number, // The starting offset along the timeline.
+  rangeNext: number, // The end along the timeline where the next state is reached.
   cancel: () => void, // Cancel the subscription to direction change.
   prev: null | ScheduledGesture, // The previous scheduled gesture in the queue for this root.
   next: null | ScheduledGesture, // The next scheduled gesture in the queue for this root.
@@ -28,6 +31,9 @@ export function scheduleGesture(
   root: FiberRoot,
   provider: GestureTimeline,
   initialDirection: boolean,
+  rangePrevious: number,
+  rangeCurrent: number,
+  rangeNext: number,
 ): ScheduledGesture {
   let prev = root.gestures;
   while (prev !== null) {
@@ -42,32 +48,43 @@ export function scheduleGesture(
     }
     prev = next;
   }
+  const isFlippedDirection = rangePrevious > rangeNext;
   // Add new instance to the end of the queue.
-  const cancel = subscribeToGestureDirection(provider, (direction: boolean) => {
-    if (gesture.direction !== direction) {
-      gesture.direction = direction;
-      if (gesture.prev === null && root.gestures !== gesture) {
-        // This gesture is not in the schedule, meaning it was already rendered.
-        // We need to rerender in the new direction. Insert it into the first slot
-        // in case other gestures are queued after the on-going one.
-        const existing = root.gestures;
-        gesture.next = existing;
-        if (existing !== null) {
-          existing.prev = gesture;
+  const cancel = subscribeToGestureDirection(
+    provider,
+    rangeCurrent,
+    (direction: boolean) => {
+      if (isFlippedDirection) {
+        direction = !direction;
+      }
+      if (gesture.direction !== direction) {
+        gesture.direction = direction;
+        if (gesture.prev === null && root.gestures !== gesture) {
+          // This gesture is not in the schedule, meaning it was already rendered.
+          // We need to rerender in the new direction. Insert it into the first slot
+          // in case other gestures are queued after the on-going one.
+          const existing = root.gestures;
+          gesture.next = existing;
+          if (existing !== null) {
+            existing.prev = gesture;
+          }
+          root.gestures = gesture;
+          // Schedule the lane on the root. The Fibers will already be marked as
+          // long as the gesture is active on that Hook.
+          root.pendingLanes |= GestureLane;
+          ensureRootIsScheduled(root);
         }
-        root.gestures = gesture;
-        // Schedule the lane on the root. The Fibers will already be marked as
-        // long as the gesture is active on that Hook.
-        root.pendingLanes |= GestureLane;
-        ensureRootIsScheduled(root);
+        // TODO: If we're currently rendering this gesture, we need to restart it.
       }
-      // TODO: If we're currently rendering this gesture, we need to restart it.
-    }
-  });
+    },
+  );
   const gesture: ScheduledGesture = {
     provider: provider,
     count: 1,
     direction: initialDirection,
+    rangePrevious: rangePrevious,
+    rangeCurrent: rangeCurrent,
+    rangeNext: rangeNext,
     cancel: cancel,
     prev: prev,
     next: null,

packages/react-reconciler/src/ReactFiberHooks.js

@@ -16,6 +16,7 @@ import type {
   Awaited,
   StartGesture,
   GestureProvider,
+  GestureOptions,
 } from 'shared/ReactTypes';
 import type {
   Fiber,
@@ -35,6 +36,7 @@ import {
   NotPendingTransition as NoPendingHostTransition,
   setCurrentUpdatePriority,
   getCurrentUpdatePriority,
+  getCurrentGestureOffset,
 } from './ReactFiberConfig';
 import ReactSharedInternals from 'shared/ReactSharedInternals';
 import {
@@ -3988,6 +3990,7 @@ function startGesture(
   fiber: Fiber,
   queue: SwipeTransitionUpdateQueue,
   gestureProvider: GestureProvider,
+  gestureOptions?: GestureOptions,
 ): () => void {
   const root = enqueueGestureRender(fiber);
   if (root === null) {
@@ -3998,10 +4001,44 @@ function startGesture(
     };
   }
   const gestureTimeline: GestureTimeline = gestureProvider;
+  const currentOffset = getCurrentGestureOffset(gestureTimeline);
+  const range = gestureOptions && gestureOptions.range;
+  const rangePrevious: number = range ? range[0] : 0; // If no range is provider we assume it's the starting point of the range.
+  const rangeCurrent: number = range ? range[1] : currentOffset;
+  const rangeNext: number = range ? range[2] : 100; // If no range is provider we assume it's the starting point of the range.
+  if (__DEV__) {
+    if (
+      (rangePrevious > rangeCurrent && rangeNext > rangeCurrent) ||
+      (rangePrevious < rangeCurrent && rangeNext < rangeCurrent)
+    ) {
+      console.error(
+        'The range of a gesture needs "previous" and "next" to be on either side of ' +
+          'the "current" offset. Both cannot be above current and both cannot be below current.',
+      );
+    }
+  }
+  const isFlippedDirection = rangePrevious > rangeNext;
+  const initialDirection =
+    // If a range is specified we can imply initial direction if it's not the current
+    // value such as if the gesture starts after it has already moved.
+    currentOffset < rangeCurrent
+      ? isFlippedDirection
+      : currentOffset > rangeCurrent
+        ? !isFlippedDirection
+        : // Otherwise, look for an explicit option.
+          gestureOptions && gestureOptions.direction === 'next'
+          ? true
+          : gestureOptions && gestureOptions.direction === 'previous'
+            ? false
+            : // If no option is specified, imply from the values specified.
+              queue.initialDirection;
   const scheduledGesture = scheduleGesture(
     root,
     gestureTimeline,
-    queue.initialDirection,
+    initialDirection,
+    rangePrevious,
+    rangeCurrent,
+    rangeNext,
   );
   // Add this particular instance to the queue.
   // We add multiple of the same timeline even if they get batched so

packages/react-reconciler/src/forks/ReactFiberConfig.custom.js

@@ -145,6 +145,7 @@ export const wasInstanceInViewport = $$$config.wasInstanceInViewport;
 export const hasInstanceChanged = $$$config.hasInstanceChanged;
 export const hasInstanceAffectedParent = $$$config.hasInstanceAffectedParent;
 export const startViewTransition = $$$config.startViewTransition;
+export const getCurrentGestureOffset = $$$config.getCurrentGestureOffset;
 export const subscribeToGestureDirection =
   $$$config.subscribeToGestureDirection;
 export const createViewTransitionInstance =

packages/react-test-renderer/src/ReactFiberConfigTestHost.js

@@ -393,8 +393,13 @@ export function getInstanceFromNode(mockNode: Object): Object | null {
 
 export type GestureTimeline = null;
 
+export function getCurrentGestureOffset(provider: GestureTimeline): number {
+  return 0;
+}
+
 export function subscribeToGestureDirection(
   provider: GestureTimeline,
+  currentOffset: number,
   directionCallback: (direction: boolean) => void,
 ): () => void {
   return () => {};

packages/shared/ReactTypes.js

@@ -172,7 +172,15 @@ export type ReactFormState<S, ReferenceId> = [
 // renderer supports it.
 export type GestureProvider = any;
 
-export type StartGesture = (gestureProvider: GestureProvider) => () => void;
+export type StartGesture = (
+  gestureProvider: GestureProvider,
+  gestureOptions: GestureOptions,
+) => () => void;
+
+export type GestureOptions = {
+  direction?: 'previous' | 'next',
+  range?: [/*previous*/ number, /*current*/ number, /*next*/ number],
+};
 
 export type Awaited<T> = T extends null | void
   ? T // special case for `null | undefined` when not in `--strictNullChecks` mode