From 5f4bb00007c92a0a2310540e0c97230d73c63e70 Mon Sep 17 00:00:00 2001
From: fufesou <linlong1266@gmail.com>
Date: Sat, 12 Sep 2026 00:20:28 +0800
Subject: [PATCH] fix(web): align cursor bitmap and hotspot rounding

---
 flutter/lib/models/model.dart      |  2 +-
 flutter/lib/web/custom_cursor.dart |  8 ++--
 flutter/test/cursor_web_test.dart  | 64 ++++++++++++++++++++++++++++++
 3 files changed, 69 insertions(+), 5 deletions(-)
 create mode 100644 flutter/test/cursor_web_test.dart

diff --git a/flutter/lib/models/model.dart b/flutter/lib/models/model.dart
index eaa82ed6e..7ac4cf95c 100644
--- a/flutter/lib/models/model.dart
+++ b/flutter/lib/models/model.dart
@@ -2882,7 +2882,7 @@ class CursorData {
 
   int _doubleToInt(double v) => (v * 10e6).round().toInt();
 
-  bool get _usesLogicalCursorPixels => isLinux || isMacOS;
+  bool get _usesLogicalCursorPixels => isLinux || isMacOS || isWeb;
   int get scaledWidth => _scaledDimension(width, scale);
   int get scaledHeight => _scaledDimension(height, scale);
 
diff --git a/flutter/lib/web/custom_cursor.dart b/flutter/lib/web/custom_cursor.dart
index 54df77e98..cc1ed081a 100644
--- a/flutter/lib/web/custom_cursor.dart
+++ b/flutter/lib/web/custom_cursor.dart
@@ -52,8 +52,8 @@ class CursorManager {
         'cursor',
         jsonEncode({
           'url': cursorData.url,
-          'hotx': cursorData.hotX.toInt(),
-          'hoty': cursorData.hotY.toInt(),
+          'hotx': cursorData.hotX.round(),
+          'hoty': cursorData.hotY.round(),
         })
       ]);
     }
@@ -116,8 +116,8 @@ MouseCursor buildCursorOfCache(
       CursorManager.instance.registerCursor(CursorData(
           key: key,
           url: 'data:image/rgba;base64,${base64Encode(data)}',
-          width: (cache.width * cache.scale).toInt(),
-          height: (cache.height * cache.scale).toInt(),
+          width: cache.scaledWidth,
+          height: cache.scaledHeight,
           hotX: cache.hotx,
           hotY: cache.hoty));
       cursor.addKey(key);
diff --git a/flutter/test/cursor_web_test.dart b/flutter/test/cursor_web_test.dart
new file mode 100644
index 000000000..0e32d35e1
--- /dev/null
+++ b/flutter/test/cursor_web_test.dart
@@ -0,0 +1,64 @@
+@TestOn('browser')
+library;
+
+import 'dart:convert';
+import 'dart:js' as js;
+import 'dart:typed_data';
+
+import 'package:flutter_hbb/models/model.dart' as model;
+import 'package:flutter_hbb/web/custom_cursor.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:image/image.dart' as img;
+
+class _CursorModel extends Fake implements model.CursorModel {
+  @override
+  final Set<String> cachedKeys = {};
+
+  @override
+  void addKey(String key) => cachedKeys.add(key);
+}
+
+void main() {
+  test('Web cursor rounds its bitmap and hotspot together', () async {
+    Map<String, dynamic>? registered;
+    final original = js.context['setByName'];
+    js.context['setByName'] = js.allowInterop((String name, String value) {
+      expect(name, 'cursor');
+      registered = jsonDecode(value) as Map<String, dynamic>;
+    });
+    addTearDown(() => js.context['setByName'] = original);
+
+    const sourceSide = 48;
+    final image = img.Image(width: sourceSide, height: sourceSide, numChannels: 4);
+    img.fill(image, color: img.ColorRgba8(255, 255, 255, 255));
+    for (final (sourceHotspot, scale, outputSide, expectedHotspot) in [
+      ((7.0, 7.0), 633 / 1600, 19, (3, 3)),
+      ((21.0, 23.0), 633 / 1600, 19, (8, 9)),
+      ((22.0, 22.0), 633 / 1600, 19, (9, 9)),
+      ((21.0, 23.0), 0.05, 12, (5, 6)),
+      ((21.0, 23.0), 0.5, 24, (11, 12)),
+      ((7.0, 7.0), 1.0, 48, (7, 7)),
+    ]) {
+      final cache = model.CursorData(
+        peerId: 'web-cursor-test',
+        id: '$sourceHotspot',
+        image: image,
+        scale: 1,
+        data: Uint8List.fromList(img.encodePng(image)),
+        hotxOrigin: sourceHotspot.$1,
+        hotyOrigin: sourceHotspot.$2,
+        width: sourceSide,
+        height: sourceSide,
+      );
+      final cursor = buildCursorOfCache(_CursorModel(), scale, cache);
+      final session = cursor.createSession(1);
+      await session.activate();
+      final uri = Uri.parse(registered!['url'] as String);
+      final bitmap = img.decodePng(uri.data!.contentAsBytes())!;
+      expect((bitmap.width, bitmap.height), (outputSide, outputSide));
+      expect((registered!['hotx'], registered!['hoty']), expectedHotspot);
+      session.dispose();
+      await deleteCustomCursor(cache.updateGetKey(scale));
+    }
+  });
+}