Merge pull request #4177 from element-hq/ignore-layout-updates

Performance: Ignore redundant layout updates

src/state/CallViewModel/CallViewModel.ts

@@ -79,7 +79,7 @@ import {
   type ReactionInfo,
   type ReactionOption,
 } from "../../reactions";
-import { shallowEquals } from "../../utils/array";
+import { shallowEquals as shallowArrayEquals } from "../../utils/array";
 import { type MediaDevices } from "../MediaDevices";
 import { constant, type Behavior } from "../Behavior";
 import { E2eeType } from "../../e2ee/e2eeType";
@@ -89,6 +89,7 @@ import { getUrlParams, HeaderStyle } from "../../UrlParams";
 import { type ProcessorState } from "../../livekit/TrackProcessorContext";
 import { ElementWidgetActions, widget } from "../../widget";
 import {
+  layoutShallowEquals,
   type Alignment,
   type GridLayoutMedia,
   type Layout,
@@ -941,7 +942,7 @@ export function createCallViewModel$(
               bins.sort(([, bin1], [, bin2]) => bin1 - bin2).map(([m]) => m),
             );
       }),
-      distinctUntilChanged(shallowEquals),
+      distinctUntilChanged(shallowArrayEquals),
     ),
   );
 
@@ -1000,7 +1001,7 @@ export function createCallViewModel$(
   const spotlight$ = scope.behavior<MediaViewModel[]>(
     spotlightAndPip$.pipe(
       map(({ spotlight }) => spotlight),
-      distinctUntilChanged<MediaViewModel[]>(shallowEquals),
+      distinctUntilChanged<MediaViewModel[]>(shallowArrayEquals),
     ),
   );
 
@@ -1209,6 +1210,7 @@ export function createCallViewModel$(
         }
         return layout;
       }),
+      distinctUntilChanged(),
       scope.bind(),
     )
     .subscribe((orientation) => {
@@ -1574,7 +1576,11 @@ export function createCallViewModel$(
    * The layout of tiles in the call interface.
    */
   const layout$ = scope.behavior<Layout>(
-    layoutInternals$.pipe(map(({ layout }) => layout)),
+    layoutInternals$.pipe(
+      map(({ layout }) => layout),
+      // Drop redundant layout updates before they would hit React.
+      distinctUntilChanged<Layout>(layoutShallowEquals),
+    ),
   );
 
   const overflowing$ = scope.behavior<boolean>(

src/state/layout-types.test.ts

@@ -0,0 +1,74 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { test, expect } from "vitest";
+import {
+  type Alignment,
+  layoutShallowEquals,
+  type Layout,
+} from "./layout-types";
+import {
+  type SpotlightTileViewModel,
+  type GridTileViewModel,
+} from "./TileViewModel";
+import { BehaviorSubject } from "rxjs";
+
+const spotlightTile = {} as unknown as SpotlightTileViewModel;
+const gridTile = {} as unknown as GridTileViewModel;
+const pipAlignment$ = new BehaviorSubject<Alignment>({
+  inline: "end",
+  block: "end",
+});
+
+const spotlightExpanded: Layout = {
+  type: "spotlight-expanded",
+  spotlight: spotlightTile,
+  pipAlignment$,
+};
+
+const spotlightPortrait: Layout = {
+  type: "spotlight-portrait",
+  spotlight: spotlightTile,
+  grid: [gridTile],
+  setVisibleTiles: () => {},
+};
+
+test("layoutShallowEquals considers a layout to be equal to its shallow clone", () =>
+  expect(layoutShallowEquals(spotlightExpanded, { ...spotlightExpanded })).toBe(
+    true,
+  ));
+
+test("layoutShallowEquals detects a missing key", () => {
+  expect(
+    layoutShallowEquals(spotlightExpanded, {
+      ...spotlightExpanded,
+      pip: gridTile,
+    }),
+  ).toBe(false);
+  expect(
+    layoutShallowEquals(
+      { ...spotlightExpanded, pip: gridTile },
+      spotlightExpanded,
+    ),
+  ).toBe(false);
+});
+
+test("layoutShallowEquals considers grid arrays with equal contents to be equal", () =>
+  expect(
+    layoutShallowEquals(spotlightPortrait, {
+      ...spotlightPortrait,
+      grid: [...spotlightPortrait.grid],
+    }),
+  ).toBe(true));
+
+test("layoutShallowEquals detects grid arrays with different contents", () =>
+  expect(
+    layoutShallowEquals(spotlightPortrait, {
+      ...spotlightPortrait,
+      grid: [...spotlightPortrait.grid, gridTile],
+    }),
+  ).toBe(false));

src/state/layout-types.ts

@@ -16,6 +16,7 @@ import {
   type SpotlightTileViewModel,
 } from "./TileViewModel.ts";
 import { type Behavior } from "./Behavior.ts";
+import { shallowEquals as arrayShallowEquals } from "../utils/array.ts";
 
 export interface GridLayoutMedia {
   type: "grid";
@@ -140,3 +141,30 @@ export type Layout =
   | OneOnOneDesktopLayout
   | OneOnOneMobileLayout
   | PipLayout;
+
+/**
+ * Tests whether the top-level properties and array elements of layout `a` are
+ * equal to those of layout `b`. Useful for deduping redundant layout updates.
+ */
+export function layoutShallowEquals(a: Layout, b: Layout): boolean {
+  // If a and b have the same number of keys and every key in a is also in b,
+  // then they have the same keys.
+  const aKeys = Object.keys(a);
+  const bKeys = Object.keys(b);
+  if (aKeys.length !== bKeys.length) return false;
+
+  for (const key of aKeys) {
+    if (!(key in b)) return false;
+
+    // Now check that they have the same values.
+    const aValue = (a as any)[key];
+    const bValue = (b as any)[key];
+    if (Array.isArray(aValue) && Array.isArray(bValue)) {
+      // Special case for arrays so we can detect when the grid tiles arrays are
+      // essentially the same.
+      if (!arrayShallowEquals(aValue, bValue)) return false;
+    } else if (aValue !== bValue) return false;
+  }
+
+  return true;
+}