⏪️(frontend) revert GridLayout re-render optimization too

Out of precaution, also revert the previous GridLayout re-render
optimization to avoid any layout regression alongside the
CarouselLayout revert.

The useSize-based re-render optimization will be reintroduced in a
dedicated small PR and release. That will also be a good occasion to
polish the layout code along the way.

src/frontend/src/features/layout/components/CarouselLayout.tsx

@@ -3,7 +3,6 @@ import { getScrollBarWidth } from '@livekit/components-core'
 import * as React from 'react'
 import { TrackLoop, useVisualStableUpdate } from '@livekit/components-react'
 import { useSize } from '@/features/rooms/livekit/hooks/useResizeObserver'
-import { useCallback, useEffect, useLayoutEffect } from 'react'
 
 const MIN_HEIGHT = 130
 const MIN_WIDTH = 140
@@ -11,72 +10,6 @@ const MIN_VISIBLE_TILES = 1
 const ASPECT_RATIO = 16 / 10
 const ASPECT_RATIO_INVERT = (1 - ASPECT_RATIO) * -1
 
-type CarouselOrientation = 'vertical' | 'horizontal'
-
-interface CarouselLayoutState {
-  orientation: CarouselOrientation
-  maxVisibleTiles: number
-}
-
-interface CarouselLayoutObserverProps {
-  asideEl: React.RefObject<HTMLDivElement>
-  orientation?: CarouselOrientation
-  onLayoutChange: (layout: CarouselLayoutState) => void
-}
-
-const CarouselLayoutObserver = ({
-  orientation,
-  asideEl,
-  onLayoutChange,
-}: CarouselLayoutObserverProps) => {
-  const { width, height } = useSize(asideEl)
-
-  // Hysteresis memory: avoids flapping between N and N+1 tiles when the
-  // container size hovers around a breakpoint. A ref (not state) because
-  // updating it must not trigger a re-render.
-  const prevTilesRef = React.useRef(0)
-
-  const carouselOrientation: CarouselOrientation =
-    orientation ?? (height >= width ? 'vertical' : 'horizontal')
-
-  const tileSpan =
-    carouselOrientation === 'vertical'
-      ? Math.max(width * ASPECT_RATIO_INVERT, MIN_HEIGHT)
-      : Math.max(height * ASPECT_RATIO, MIN_WIDTH)
-
-  const scrollBarWidth = getScrollBarWidth()
-
-  const availableSpan =
-    (carouselOrientation === 'vertical' ? height : width) - scrollBarWidth
-
-  const tilesThatFit = Math.max(availableSpan / tileSpan, MIN_VISIBLE_TILES)
-
-  let maxVisibleTiles: number
-  if (Math.abs(tilesThatFit - prevTilesRef.current) < 0.5) {
-    // Within the dead zone: keep the previous count.
-    maxVisibleTiles = Math.round(prevTilesRef.current)
-  } else {
-    maxVisibleTiles = Math.round(tilesThatFit)
-    prevTilesRef.current = tilesThatFit
-  }
-
-  // Apply cosmetic layout output straight to the DOM.
-  useLayoutEffect(() => {
-    const el = asideEl.current
-    if (!el) return
-    el.dataset.lkOrientation = carouselOrientation
-    el.style.setProperty('--lk-max-visible-tiles', maxVisibleTiles.toString())
-  }, [asideEl, carouselOrientation, maxVisibleTiles])
-
-  // Report upward only what the parent actually needs for
-  // `useVisualStableUpdate` (and only when it changes — see parent handler).
-  useEffect(() => {
-    onLayoutChange({ orientation: carouselOrientation, maxVisibleTiles })
-  }, [carouselOrientation, maxVisibleTiles, onLayoutChange])
-
-  return null
-}
-
 /** @public */
 export interface CarouselLayoutProps extends React.HTMLAttributes<HTMLMediaElement> {
   tracks: TrackReferenceOrPlaceholder[]
@@ -107,42 +40,52 @@ export function CarouselLayout({
   ...props
 }: CarouselLayoutProps) {
   const asideEl = React.useRef<HTMLDivElement>(null)
+  const [prevTiles, setPrevTiles] = React.useState(0)
+  const { width, height } = useSize(asideEl)
+  const carouselOrientation = orientation
+    ? orientation
+    : height >= width
+      ? 'vertical'
+      : 'horizontal'
 
-  const [layout, setLayout] = React.useState<CarouselLayoutState>({
-    orientation: orientation ?? 'vertical',
-    maxVisibleTiles: MIN_VISIBLE_TILES,
-  })
+  const tileSpan =
+    carouselOrientation === 'vertical'
+      ? Math.max(width * ASPECT_RATIO_INVERT, MIN_HEIGHT)
+      : Math.max(height * ASPECT_RATIO, MIN_WIDTH)
+  const scrollBarWidth = getScrollBarWidth()
 
-  // Stable callback + identity check: the parent only re-renders when the
-  // derived layout genuinely changed, not on every resize tick.
-  const handleLayoutChange = useCallback((next: CarouselLayoutState) => {
-    setLayout((prev) =>
-      prev.orientation === next.orientation &&
-      prev.maxVisibleTiles === next.maxVisibleTiles
-        ? prev
-        : next
-    )
-  }, [])
+  const tilesThatFit =
+    carouselOrientation === 'vertical'
+      ? Math.max((height - scrollBarWidth) / tileSpan, MIN_VISIBLE_TILES)
+      : Math.max((width - scrollBarWidth) / tileSpan, MIN_VISIBLE_TILES)
 
-  const sortedTiles = useVisualStableUpdate(tracks, layout.maxVisibleTiles)
+  let maxVisibleTiles = Math.round(tilesThatFit)
+  if (Math.abs(tilesThatFit - prevTiles) < 0.5) {
+    maxVisibleTiles = Math.round(prevTiles)
+  } else if (prevTiles !== tilesThatFit) {
+    setPrevTiles(tilesThatFit)
+  }
+
+  const sortedTiles = useVisualStableUpdate(tracks, maxVisibleTiles)
+
+  React.useLayoutEffect(() => {
+    if (asideEl.current) {
+      asideEl.current.dataset.lkOrientation = carouselOrientation
+      asideEl.current.style.setProperty(
+        '--lk-max-visible-tiles',
+        maxVisibleTiles.toString()
+      )
+    }
+  }, [maxVisibleTiles, carouselOrientation])
 
   return (
-    <>
-      <CarouselLayoutObserver
-        asideEl={asideEl}
-        orientation={orientation}
-        onLayoutChange={handleLayoutChange}
-      />
-      {/* `key` intentionally remounts the container when orientation flips, */}
-      {/* which resets scroll position and re-runs the observer measurement. */}
-      <aside
-        key={layout.orientation}
-        className="lk-carousel"
-        ref={asideEl}
-        {...props}
-      >
-        <TrackLoop tracks={sortedTiles}>{props.children}</TrackLoop>
-      </aside>
-    </>
+    <aside
+      key={carouselOrientation}
+      className="lk-carousel"
+      ref={asideEl}
+      {...props}
+    >
+      <TrackLoop tracks={sortedTiles}>{props.children}</TrackLoop>
+    </aside>
   )
 }

src/frontend/src/features/layout/components/GridLayout.tsx

@@ -10,36 +10,8 @@ import { mergeProps } from '@/utils/mergeProps'
 import { PaginationIndicator } from './PaginationIndicator'
 import { useGridLayout } from '../hooks/useGridLayout'
 import { PaginationControl } from './PaginationControl'
-import { useEffect, useRef, useState } from 'react'
 import { useSpeakerPromotionTrigger } from '../hooks/useSpeakerPromotionTrigger'
 
-interface GridLayoutObserverProps {
-  gridEl: React.RefObject<HTMLDivElement>
-  trackCount: number
-  onMaxTilesChange: (maxTiles: number) => void
-}
-
-/**
- * Headless component that runs the layout calculation in isolation and
- * reports the resulting tile capacity upward.
- *
- * `useGridLayout` re-renders its host on every layout recalculation
- * (e.g. container resizes). Rendering it in a null child means only this
- * component churns; the parent `GridLayout` re-renders solely when
- * `maxTiles` actually changes, since `setState` bails out on equal values.
- */
-const GridLayoutObserver = ({
-  gridEl,
-  trackCount,
-  onMaxTilesChange,
-}: GridLayoutObserverProps) => {
-  const { layout } = useGridLayout(gridEl, trackCount)
-  useEffect(() => {
-    onMaxTilesChange(layout.maxTiles)
-  }, [onMaxTilesChange, layout.maxTiles])
-
-  return null
-}
 
 /** @public */
 export interface GridLayoutProps
@@ -67,14 +39,15 @@ export interface GridLayoutProps
  * @public
  */
 export function GridLayout({ tracks, ...props }: GridLayoutProps) {
-  const gridEl = useRef<HTMLDivElement>(null)
-  const [maxTiles, setMaxTiles] = useState(1)
+  const gridEl = React.createRef<HTMLDivElement>()
 
   const elementProps = React.useMemo(
     () => mergeProps(props, { className: 'lk-grid-layout' }),
     [props]
   )
-  const pagination = usePagination(maxTiles, tracks)
+
+  const { layout } = useGridLayout(gridEl, tracks.length)
+  const pagination = usePagination(layout.maxTiles, tracks)
   useSpeakerPromotionTrigger(pagination.tracks)
 
   useSwipe(gridEl, {
@@ -88,13 +61,8 @@ export function GridLayout({ tracks, ...props }: GridLayoutProps) {
       data-lk-pagination={pagination.totalPageCount > 1}
       {...elementProps}
     >
-      <GridLayoutObserver
-        gridEl={gridEl}
-        trackCount={tracks.length}
-        onMaxTilesChange={setMaxTiles}
-      />
       <TrackLoop tracks={pagination.tracks}>{props.children}</TrackLoop>
-      {tracks.length > maxTiles && (
+      {tracks.length > layout.maxTiles && (
         <>
           <PaginationIndicator
             totalPageCount={pagination.totalPageCount}