[perf] Reinstate render throttling (#3160)

Follow up to #3129 

### Change Type

<!-- ❗ Please select a 'Scope' label ❗️ -->

- [x] `sdk` — Changes the tldraw SDK

- [x] `improvement` — Improving existing features



### Test Plan

1. Add a step-by-step description of how to test your PR here.
2.

- [ ] Unit Tests
- [ ] End to end tests

### Release Notes

- Add a brief release note for your PR here.

packages/editor/src/lib/components/Shape.tsx

@@ -1,4 +1,4 @@
-import { track, useQuickReactor, useStateTracking } from '@tldraw/state'
+import { track, useLayoutReaction, useStateTracking } from '@tldraw/state'
 import { TLShape, TLShapeId } from '@tldraw/tlschema'
 import * as React from 'react'
 import { ShapeUtil } from '../editor/shapes/ShapeUtil'
@@ -49,36 +49,16 @@ export const Shape = track(function Shape({
 		backgroundContainerRef.current?.style.setProperty(property, value)
 	}, [])
 
-	useQuickReactor(
+	useLayoutReaction('set shape stuff', () => {
-		'set shape container transform position',
-		() => {
 		const shape = editor.getShape(id)
 		if (!shape) return // probably the shape was just deleted
 
 		const pageTransform = editor.getShapePageTransform(id)
 		const transform = Mat.toCssString(pageTransform)
 		setProperty('transform', transform)
-		},
-		[editor, setProperty]
-	)
-
-	useQuickReactor(
-		'set shape container clip path',
-		() => {
-			const shape = editor.getShape(id)
-			if (!shape) return null
 
 		const clipPath = editor.getShapeClipPath(id)
 		setProperty('clip-path', clipPath ?? 'none')
-		},
-		[editor, setProperty]
-	)
-
-	useQuickReactor(
-		'set shape height and width',
-		() => {
-			const shape = editor.getShape(id)
-			if (!shape) return null
 
 		const bounds = editor.getShapeGeometry(shape).bounds
 		const dpr = Math.floor(editor.getInstanceState().devicePixelRatio * 100) / 100
@@ -93,9 +73,7 @@ export const Shape = track(function Shape({
 		const height = heightRemainder === 0 ? bounds.h : bounds.h + (dprMultiple - heightRemainder)
 		setProperty('width', Math.max(width, dprMultiple) + 'px')
 		setProperty('height', Math.max(height, dprMultiple) + 'px')
-		},
+	})
-		[editor]
-	)
 
 	// Set the opacity of the container when the opacity changes
 	React.useLayoutEffect(() => {

packages/editor/src/lib/components/default-components/DefaultCanvas.tsx

@@ -1,4 +1,4 @@
-import { react, track, useQuickReactor, useValue } from '@tldraw/state'
+import { react, track, useLayoutReaction, useValue } from '@tldraw/state'
 import { TLHandle, TLShapeId } from '@tldraw/tlschema'
 import { dedupe, modulate, objectMapValues } from '@tldraw/utils'
 import classNames from 'classnames'
@@ -41,9 +41,7 @@ export function DefaultCanvas({ className }: TLCanvasComponentProps) {
 	useGestureEvents(rCanvas)
 	useFixSafariDoubleTapZoomPencilEvents(rCanvas)
 
-	useQuickReactor(
+	useLayoutReaction('position layers', () => {
-		'position layers',
-		() => {
 		const htmlElm = rHtmlLayer.current
 		if (!htmlElm) return
 		const htmlElm2 = rHtmlLayer2.current
@@ -62,9 +60,7 @@ export function DefaultCanvas({ className }: TLCanvasComponentProps) {
 		)}px,${toDomPrecision(y + offset)}px)`
 		htmlElm.style.setProperty('transform', transform)
 		htmlElm2.style.setProperty('transform', transform)
-		},
+	})
-		[editor]
-	)
 
 	const events = useCanvasEvents()
 

packages/state/api-report.md

@@ -128,6 +128,9 @@ export function useComputed<Value>(name: string, compute: () => Value, deps: any
 // @public (undocumented)
 export function useComputed<Value, Diff = unknown>(name: string, compute: () => Value, opts: ComputedOptions<Value, Diff>, deps: any[]): Computed<Value>;
 
+// @internal (undocumented)
+export function useLayoutReaction(name: string, effect: () => void): void;
+
 // @public (undocumented)
 export function useQuickReactor(name: string, reactFn: () => void, deps?: any[]): void;
 

packages/state/package.json

@@ -52,6 +52,9 @@
 			"node_modules/(?!(nanoid)/)"
 		]
 	},
+	"dependencies": {
+		"@tldraw/utils": "workspace:*"
+	},
 	"devDependencies": {
 		"@types/lodash": "^4.14.188",
 		"@types/react": "^18.2.47",

packages/state/src/lib/core/EffectScheduler.ts

@@ -51,6 +51,7 @@ class __EffectScheduler__<Result> {
 	lastTraversedEpoch = GLOBAL_START_EPOCH
 
 	private lastReactedEpoch = GLOBAL_START_EPOCH
+	private hasPendingEffect = true
 	private _scheduleCount = 0
 
 	/**
@@ -94,6 +95,7 @@ class __EffectScheduler__<Result> {
 	/** @internal */
 	scheduleEffect() {
 		this._scheduleCount++
+		this.hasPendingEffect = true
 		if (this._scheduleEffect) {
 			// if the effect should be deferred (e.g. until a react render), do so
 			this._scheduleEffect(this.maybeExecute)
@@ -103,9 +105,10 @@ class __EffectScheduler__<Result> {
 		}
 	}
 
-	private maybeExecute = () => {
+	/** @internal */
+	readonly maybeExecute = () => {
 		// bail out if we have been detached before this runs
-		if (!this._isActivelyListening) return
+		if (!this._isActivelyListening || !this.hasPendingEffect) return
 		this.execute()
 	}
 
@@ -141,6 +144,7 @@ class __EffectScheduler__<Result> {
 		try {
 			startCapturingParents(this)
 			const result = this.runEffect(this.lastReactedEpoch)
+			this.hasPendingEffect = false
 			this.lastReactedEpoch = getGlobalEpoch()
 			return result
 		} finally {

packages/state/src/lib/react/index.ts

@@ -1,6 +1,7 @@
 export { track } from './track'
 export { useAtom } from './useAtom'
 export { useComputed } from './useComputed'
+export { useLayoutReaction } from './useLayoutReaction'
 export { useQuickReactor } from './useQuickReactor'
 export { useReactor } from './useReactor'
 export { useStateTracking } from './useStateTracking'

packages/state/src/lib/react/useLayoutReaction.ts

@@ -0,0 +1,10 @@
+import React from 'react'
+import { useTrackedScheduler } from './useTrackedScheduler'
+
+/** @internal */
+export function useLayoutReaction(name: string, effect: () => void): void {
+	const scheduler = useTrackedScheduler(name, effect)
+
+	// eslint-disable-next-line react-hooks/exhaustive-deps
+	React.useLayoutEffect(scheduler.maybeExecute)
+}

packages/state/src/lib/react/useStateTracking.ts

@@ -1,58 +1,6 @@
-import React from 'react'
+import { useTrackedScheduler } from './useTrackedScheduler'
-import { EffectScheduler } from '../core'
 
 /** @internal */
 export function useStateTracking<T>(name: string, render: () => T): T {
-	// user render is only called at the bottom of this function, indirectly via scheduler.execute()
+	return useTrackedScheduler(name, render).execute()
-	// we need it to always be up-to-date when calling scheduler.execute() but it'd be wasteful to
-	// instantiate a new EffectScheduler on every render, so we use an immediately-updated ref
-	// to wrap it
-	const renderRef = React.useRef(render)
-	renderRef.current = render
-
-	const [scheduler, subscribe, getSnapshot] = React.useMemo(() => {
-		let scheduleUpdate = null as null | (() => void)
-		// useSyncExternalStore requires a subscribe function that returns an unsubscribe function
-		const subscribe = (cb: () => void) => {
-			scheduleUpdate = cb
-			return () => {
-				scheduleUpdate = null
-			}
-		}
-
-		const scheduler = new EffectScheduler(
-			`useStateTracking(${name})`,
-			// this is what `scheduler.execute()` will call
-			() => renderRef.current?.(),
-			// this is what will be invoked when @tldraw/state detects a change in an upstream reactive value
-			{
-				scheduleEffect() {
-					scheduleUpdate?.()
-				},
-			}
-		)
-
-		// we use an incrementing number based on when this
-		const getSnapshot = () => scheduler.scheduleCount
-
-		return [scheduler, subscribe, getSnapshot]
-	}, [name])
-
-	React.useSyncExternalStore(subscribe, getSnapshot, getSnapshot)
-
-	// reactive dependencies are captured when `scheduler.execute()` is called
-	// and then to make it reactive we wait for a `useEffect` to 'attach'
-	// this allows us to avoid rendering outside of React's render phase
-	// and avoid 'zombie' components that try to render with bad/deleted data before
-	// react has a chance to umount them.
-	React.useEffect(() => {
-		scheduler.attach()
-		// do not execute, we only do that in render
-		scheduler.maybeScheduleEffect()
-		return () => {
-			scheduler.detach()
-		}
-	}, [scheduler])
-
-	return scheduler.execute()
 }

packages/state/src/lib/react/useTrackedScheduler.ts

@@ -0,0 +1,61 @@
+import { fpsThrottle } from '@tldraw/utils'
+import React from 'react'
+import { EffectScheduler } from '../core'
+
+/** @internal */
+export function useTrackedScheduler<T>(name: string, exec: () => T): EffectScheduler<T> {
+	// This hook creates an effect scheduler that will trigger re-renders when its reactive dependencies change, but it
+	// defers the actual execution of the effect to the consumer of this hook.
+
+	// We need the exec fn to always be up-to-date when calling scheduler.execute() but it'd be wasteful to
+	// instantiate a new EffectScheduler on every render, so we use an immediately-updated ref
+	// to wrap it
+	const execRef = React.useRef(exec)
+	execRef.current = exec
+
+	const [scheduler, subscribe, getSnapshot] = React.useMemo(() => {
+		let scheduleUpdate = null as null | (() => void)
+		// useSyncExternalStore requires a subscribe function that returns an unsubscribe function
+		const subscribe = (cb: () => void) => {
+			scheduleUpdate = cb
+			return () => {
+				scheduleUpdate = null
+			}
+		}
+
+		const scheduler = new EffectScheduler(
+			`useStateTracking(${name})`,
+			// this is what `scheduler.execute()` will call
+			() => execRef.current?.(),
+			// this is what will be invoked when @tldraw/state detects a change in an upstream reactive value
+			{
+				scheduleEffect: fpsThrottle(() => {
+					scheduleUpdate?.()
+				}),
+			}
+		)
+
+		// we use an incrementing number based on when this
+		const getSnapshot = () => scheduler.scheduleCount
+
+		return [scheduler, subscribe, getSnapshot]
+	}, [name])
+
+	React.useSyncExternalStore(subscribe, getSnapshot, getSnapshot)
+
+	// reactive dependencies are captured when `scheduler.execute()` is called
+	// and then to make it reactive we wait for a `useEffect` to 'attach'
+	// this allows us to avoid rendering outside of React's render phase
+	// and avoid 'zombie' components that try to render with bad/deleted data before
+	// react has a chance to umount them.
+	React.useEffect(() => {
+		scheduler.attach()
+		// do not execute, we only do that in render
+		scheduler.maybeScheduleEffect()
+		return () => {
+			scheduler.detach()
+		}
+	}, [scheduler])
+
+	return scheduler
+}

packages/state/src/lib/react/useValue.ts

@@ -1,4 +1,5 @@
 /* eslint-disable prefer-rest-params */
+import { throttleToNextFrame } from '@tldraw/utils'
 import { useMemo, useRef, useSyncExternalStore } from 'react'
 import { Signal, computed, react } from '../core'
 
@@ -81,10 +82,16 @@ export function useValue() {
 		const { subscribe, getSnapshot } = useMemo(() => {
 			return {
 				subscribe: (listen: () => void) => {
-					return react(`useValue(${name})`, () => {
+					return react(
+						`useValue(${name})`,
+						() => {
 							$val.get()
 							listen()
-					})
+						},
+						{
+							scheduleEffect: throttleToNextFrame,
+						}
+					)
 				},
 				getSnapshot: () => $val.get(),
 			}

packages/state/tsconfig.json

@@ -2,6 +2,7 @@
 	"extends": "../../config/tsconfig.base.json",
 	"include": ["src"],
 	"exclude": ["node_modules", "dist", ".tsbuild*"],
+	"references": [{ "path": "../utils" }],
 	"compilerOptions": {
 		"outDir": "./.tsbuild",
 		"rootDir": "src"

yarn.lock

@@ -7380,6 +7380,7 @@ __metadata:
   version: 0.0.0-use.local
   resolution: "@tldraw/state@workspace:packages/state"
   dependencies:
+    "@tldraw/utils": "workspace:*"
     "@types/lodash": "npm:^4.14.188"
     "@types/react": "npm:^18.2.47"
     "@types/react-test-renderer": "npm:^18.0.0"