Add getCurrentEventPriority to the host config

packages/react-art/src/ReactARTHostConfig.js

@@ -8,6 +8,7 @@
 import Transform from 'art/core/transform';
 import Mode from 'art/modes/current';
 import invariant from 'shared/invariant';
+import {DefaultEvent} from 'shared/ReactTypes';
 
 import {TYPES, EVENT_TYPES, childrenAsString} from './ReactARTInternals';
 
@@ -327,6 +328,10 @@ export function getChildHostContext() {
   return NO_CONTEXT;
 }
 
+export function getCurrentEventPriority() {
+  return DefaultEvent;
+}
+
 export const scheduleTimeout = setTimeout;
 export const cancelTimeout = clearTimeout;
 export const noTimeout = -1;

packages/react-dom/src/client/ReactDOMHostConfig.js

@@ -15,7 +15,7 @@ import type {
   ObserveVisibleRectsCallback,
 } from 'react-reconciler/src/ReactTestSelectors';
 import type {RootType} from './ReactDOMRoot';
-import type {ReactScopeInstance} from 'shared/ReactTypes';
+import type {ReactScopeInstance, EventPriority} from 'shared/ReactTypes';
 
 import {
   precacheFiberNode,
@@ -59,6 +59,7 @@ import {
 import dangerousStyleValue from '../shared/dangerousStyleValue';
 
 import {REACT_OPAQUE_ID_TYPE} from 'shared/ReactSymbols';
+import {getEventPriorityForPluginSystem} from '../events/DOMEventProperties';
 import {retryIfBlockedOn} from '../events/ReactDOMEventReplaying';
 
 import {
@@ -68,6 +69,7 @@ import {
 } from 'shared/ReactFeatureFlags';
 import {HostComponent, HostText} from 'react-reconciler/src/ReactWorkTags';
 import {listenToAllSupportedEvents} from '../events/DOMPluginEventSystem';
+import {DefaultEvent} from 'shared/ReactTypes';
 
 export type Type = string;
 export type Props = {
@@ -372,6 +374,15 @@ export function createTextInstance(
   return textNode;
 }
 
+export function getCurrentEventPriority(): EventPriority {
+  const currentEvent = window.event;
+  if (currentEvent === undefined) {
+    return DefaultEvent;
+  }
+  // TODO: Is this fast enough? It reads from a Map.
+  return getEventPriorityForPluginSystem(currentEvent.type);
+}
+
 export const isPrimaryRenderer = true;
 export const warnsIfNotActing = true;
 // This initialization code may run even on server environments

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

@@ -17,11 +17,13 @@ import type {
   ReactNativeBaseComponentViewConfig,
   TouchedViewDataAtPoint,
 } from './ReactNativeTypes';
+import type {EventPriority} from 'shared/ReactTypes';
 
 import {mountSafeCallback_NOT_REALLY_SAFE} from './NativeMethodsMixinUtils';
 import {create, diff} from './ReactNativeAttributePayload';
 
 import invariant from 'shared/invariant';
+import {DefaultEvent} from 'shared/ReactTypes';
 
 import {dispatchEvent} from './ReactFabricEventEmitter';
 
@@ -339,6 +341,10 @@ export function shouldSetTextContent(type: string, props: Props): boolean {
   return false;
 }
 
+export function getCurrentEventPriority(): EventPriority {
+  return DefaultEvent;
+}
+
 // The Fabric renderer is secondary to the existing React Native renderer.
 export const isPrimaryRenderer = false;
 

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

@@ -8,6 +8,7 @@
  */
 
 import type {TouchedViewDataAtPoint} from './ReactNativeTypes';
+import type {EventPriority} from 'shared/ReactTypes';
 
 import invariant from 'shared/invariant';
 
@@ -25,6 +26,7 @@ import {
   updateFiberProps,
 } from './ReactNativeComponentTree';
 import ReactNativeFiberHostComponent from './ReactNativeFiberHostComponent';
+import {DefaultEvent} from 'shared/ReactTypes';
 
 const {get: getViewConfigForType} = ReactNativeViewConfigRegistry;
 
@@ -241,6 +243,10 @@ export function resetAfterCommit(containerInfo: Container): void {
   // Noop
 }
 
+export function getCurrentEventPriority(): EventPriority {
+  return DefaultEvent;
+}
+
 export const isPrimaryRenderer = true;
 export const warnsIfNotActing = true;
 

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

@@ -16,11 +16,12 @@
 
 import type {Fiber} from 'react-reconciler/src/ReactInternalTypes';
 import type {UpdateQueue} from 'react-reconciler/src/ReactUpdateQueue';
-import type {ReactNodeList, Thenable} from 'shared/ReactTypes';
+import type {ReactNodeList, Thenable, EventPriority} from 'shared/ReactTypes';
 import type {RootTag} from 'react-reconciler/src/ReactRootTags';
 
 import * as Scheduler from 'scheduler/unstable_mock';
 import {REACT_FRAGMENT_TYPE, REACT_ELEMENT_TYPE} from 'shared/ReactSymbols';
+import {DefaultEvent} from 'shared/REactTypes';
 import {
   ConcurrentRoot,
   BlockingRoot,
@@ -391,6 +392,10 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
 
     resetAfterCommit(): void {},
 
+    getCurrentEventPriority(): EventPriority {
+      return DefaultEvent;
+    },
+
     now: Scheduler.unstable_now,
 
     isPrimaryRenderer: true,

packages/react-reconciler/README.md

@@ -207,6 +207,16 @@ This is a property (not a function) that should be set to something that can nev
 
 You can proxy this to `queueMicrotask` or its equivalent in your environment.
 
+#### `getCurrentEventPriority(fn)`
+
+If there is no ongoing event (like `window.event` in the DOM), return `0`.
+
+Else, return one of the numbers depending on the ongoing event type:
+
+- For events originating from user input where each event is intentional (e.g. clicks), return `2`.
+- For events originating from continuous user input (e.g. mouse move), return `1`.
+- For any other events, return `0`.
+
 #### `isPrimaryRenderer`
 
 This is a property (not a function) that should be set to `true` if your renderer is the main one on the page. For example, if you're writing a renderer for the Terminal, it makes sense to set it to `true`, but if your renderer is used *on top of* React DOM or some other existing renderer, set it to `false`.

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

@@ -52,6 +52,7 @@ export const finalizeInitialChildren = $$$hostConfig.finalizeInitialChildren;
 export const prepareUpdate = $$$hostConfig.prepareUpdate;
 export const shouldSetTextContent = $$$hostConfig.shouldSetTextContent;
 export const createTextInstance = $$$hostConfig.createTextInstance;
+export const getCurrentEventPriority = $$$hostConfig.getCurrentEventPriority;
 export const scheduleTimeout = $$$hostConfig.scheduleTimeout;
 export const cancelTimeout = $$$hostConfig.cancelTimeout;
 export const scheduleMicrotask = $$$hostConfig.scheduleMicrotask;

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

@@ -7,7 +7,10 @@
  * @flow
  */
 
+import type {EventPriority} from 'shared/ReactTypes';
+
 import {REACT_OPAQUE_ID_TYPE} from 'shared/ReactSymbols';
+import {DefaultEvent} from 'shared/ReactTypes';
 
 export type Type = string;
 export type Props = Object;
@@ -213,6 +216,10 @@ export function createTextInstance(
   };
 }
 
+export function getCurrentEventPriority(): EventPriority {
+  return DefaultEvent;
+}
+
 export const isPrimaryRenderer = false;
 export const warnsIfNotActing = true;
 

packages/shared/ReactTypes.js

@@ -88,9 +88,9 @@ export type RefObject = {|
 
 export type EventPriority = 0 | 1 | 2;
 
-export const DiscreteEvent: EventPriority = 0;
+export const DefaultEvent: EventPriority = 0;
 export const ContinuousEvent: EventPriority = 1;
-export const DefaultEvent: EventPriority = 2;
+export const DiscreteEvent: EventPriority = 2;
 
 export type ReactScope = {|
   $$typeof: Symbol | number,