Performance: Ignore redundant layout updates

When someone starts or stops speaking, the layout will often be recomputed only to find out that there is ultimately no layout change. We can ignore these redundant updates to avoid re-rendering the InCallView and Grid components, which are relatively slow.

For that specific, common case, this reduces JS CPU usage by as much as 70% in my testing.

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>(