From 8036fd94daea937247a8266ee6f0299e78cbe265 Mon Sep 17 00:00:00 2001
From: Minh Vu <vuhoangminh97@gmail.com>
Date: Sun, 9 Aug 2026 21:33:01 +0200
Subject: [PATCH] fix(virtualized-lists): invalidate content length on
 orientation change

---
 .../Lists/ListMetricsAggregator.js            |  1 +
 .../__tests__/ListMetricsAggregator-test.js   | 37 +++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/packages/virtualized-lists/Lists/ListMetricsAggregator.js b/packages/virtualized-lists/Lists/ListMetricsAggregator.js
index 56d57e20fc00..b0516e6f7af1 100644
--- a/packages/virtualized-lists/Lists/ListMetricsAggregator.js
+++ b/packages/virtualized-lists/Lists/ListMetricsAggregator.js
@@ -319,6 +319,7 @@ export default class ListMetricsAggregator {
     if (orientation.horizontal !== this._orientation.horizontal) {
       this._cellMetrics.clear();
       this._averageCellLength = 0;
+      this._contentLength = null;
       this._highestMeasuredCellIndex = 0;
       this._measuredCellsLength = 0;
       this._measuredCellsCount = 0;
diff --git a/packages/virtualized-lists/Lists/__tests__/ListMetricsAggregator-test.js b/packages/virtualized-lists/Lists/__tests__/ListMetricsAggregator-test.js
index 7b5e416d4196..36b50e88e867 100644
--- a/packages/virtualized-lists/Lists/__tests__/ListMetricsAggregator-test.js
+++ b/packages/virtualized-lists/Lists/__tests__/ListMetricsAggregator-test.js
@@ -986,6 +986,43 @@ describe('ListMetricsAggregator', () => {
     expect(listMetrics.getContentLength()).toBe(25);
   });
 
+  it('invalidates content length when list orientation changes', () => {
+    const listMetrics = new ListMetricsAggregator();
+    const verticalOrientation = {horizontal: false, rtl: false};
+    const horizontalOrientation = {horizontal: true, rtl: false};
+    const horizontalRtlOrientation = {horizontal: true, rtl: true};
+    const cellLayout = {height: 50, width: 100, x: 0, y: 0};
+
+    listMetrics.notifyListContentLayout({
+      layout: {height: 800, width: 400},
+      orientation: verticalOrientation,
+    });
+    expect(listMetrics.hasContentLength()).toBe(true);
+
+    listMetrics.notifyCellLayout({
+      cellIndex: 0,
+      cellKey: '0',
+      orientation: horizontalOrientation,
+      layout: cellLayout,
+    });
+    expect(listMetrics.hasContentLength()).toBe(false);
+
+    expect(() =>
+      listMetrics.notifyCellLayout({
+        cellIndex: 0,
+        cellKey: '0',
+        orientation: horizontalRtlOrientation,
+        layout: cellLayout,
+      }),
+    ).toThrow();
+
+    listMetrics.notifyListContentLayout({
+      layout: {height: 50, width: 500},
+      orientation: horizontalRtlOrientation,
+    });
+    expect(listMetrics.getContentLength()).toBe(500);
+  });
+
   it('requires contentLength to resolve RTL metrics', () => {
     const listMetrics = new ListMetricsAggregator();
     const orientation = {horizontal: true, rtl: true};