fix(cursor): delegate native image scaling to cursor plugin

Use the original Flutter image and source hotspot with explicit DPR, retaining the existing view and minimum-size policies. Pin the plugin implementation from rustdesk-org/flutter_custom_cursor#1.

flutter/lib/models/model.dart

@@ -2855,6 +2855,9 @@ class CursorData {
   final String peerId;
   final String id;
   final img2.Image image;
+  // Borrowed from CursorModel/PredefinedCursor, which own its lifetime.
+  // The plugin clones the handle before starting asynchronous encoding.
+  final ui.Image nativeImage;
   double scale;
   Uint8List? data;
   final double hotxOrigin;
@@ -2868,6 +2871,7 @@ class CursorData {
     required this.peerId,
     required this.id,
     required this.image,
+    required this.nativeImage,
     required this.scale,
     required this.data,
     required this.hotxOrigin,
@@ -2879,7 +2883,9 @@ class CursorData {
 
   int _doubleToInt(double v) => (v * 10e6).round().toInt();
 
-  double _checkUpdateScale(double scale) {
+  // Keep the minimum-size policy here. Native callers let the plugin rasterize
+  // the original ui.Image; Web keeps the encoded-image resizing path.
+  double _checkUpdateScale(double scale, {bool resizeImage = true}) {
     double oldScale = this.scale;
     if (scale != 1.0) {
       // Update data if scale changed.
@@ -2892,7 +2898,7 @@ class CursorData {
       }
     }
 
-    if (_doubleToInt(oldScale) != _doubleToInt(scale)) {
+    if (resizeImage && _doubleToInt(oldScale) != _doubleToInt(scale)) {
       if (isWindows) {
         data = img2
             .copyResize(
@@ -2922,8 +2928,8 @@ class CursorData {
     return scale;
   }
 
-  String updateGetKey(double scale) {
-    scale = _checkUpdateScale(scale);
+  String updateGetKey(double scale, {bool resizeImage = true}) {
+    scale = _checkUpdateScale(scale, resizeImage: resizeImage);
     return '${peerId}_${id}_${_doubleToInt(width * scale)}_${_doubleToInt(height * scale)}';
   }
 }
@@ -2976,9 +2982,10 @@ class PredefinedCursor {
         // This function is called only one time, no need to care about the performance.
         Uint8List data = defaultImg.getBytes(order: img2.ChannelOrder.rgba);
         _image?.dispose();
-        _image = await img.decodeImageFromPixels(
+        final nativeImage = await img.decodeImageFromPixels(
             data, defaultImg.width, defaultImg.height, ui.PixelFormat.rgba8888);
-        if (_image == null) {
+        _image = nativeImage;
+        if (nativeImage == null) {
           print("decodeImageFromPixels failed, pre-defined cursor $id");
           return;
         }
@@ -2993,6 +3000,7 @@ class PredefinedCursor {
           peerId: '',
           id: id,
           image: _image2!.clone(),
+          nativeImage: nativeImage,
           scale: scale,
           data: data,
           hotxOrigin:
@@ -3471,6 +3479,7 @@ class CursorModel with ChangeNotifier {
       peerId: peerId,
       id: id,
       image: imgOrigin,
+      nativeImage: image,
       scale: 1.0,
       data: data,
       hotxOrigin: hotx,

flutter/lib/native/custom_cursor.dart

@@ -1,10 +1,14 @@
+import 'dart:async';
+
 import 'package:flutter_custom_cursor/cursor_manager.dart'
     as custom_cursor_manager;
 import 'package:flutter_custom_cursor/flutter_custom_cursor.dart';
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart' show WidgetsBinding;
 
+import 'package:flutter_hbb/common.dart';
 import 'package:flutter_hbb/models/model.dart';
 
 deleteCustomCursor(String key) =>
@@ -16,27 +20,32 @@ MouseCursor buildCursorOfCache(
   if (cache == null) {
     return MouseCursor.defer;
   } else {
-    final key = cache.updateGetKey(scale);
+    // Include the live DPR so moving between monitors rebuilds the native
+    // bitmap even when the remote view scale has not changed.
+    final dpr = WidgetsBinding
+        .instance.platformDispatcher.views.single.devicePixelRatio;
+    final key = '${cache.updateGetKey(scale, resizeImage: false)}_$dpr';
     if (!cursor.cachedKeys.contains(key)) {
-      // data should be checked here, because it may be changed after `updateGetKey()`
-      final data = cache.data;
-      if (data == null) {
-        return MouseCursor.defer;
-      }
       debugPrint(
           "Register custom cursor with key $key (${cache.hotx},${cache.hoty})");
-      // [Safety]
-      // It's ok to call async registerCursor in current synchronous context,
-      // because activating the cursor is also an async call and will always
-      // be executed after this.
-      custom_cursor_manager.CursorManager.instance
-          .registerCursor(custom_cursor_manager.CursorData()
-            ..name = key
-            ..buffer = data
-            ..width = (cache.width * cache.scale).toInt()
-            ..height = (cache.height * cache.scale).toInt()
-            ..hotX = cache.hotx
-            ..hotY = cache.hoty);
+      unawaited(custom_cursor_manager.CursorManager.instance
+          .registerCursorImage(
+        name: key,
+        image: cache.nativeImage,
+        hotSpot: Offset(cache.hotxOrigin, cache.hotyOrigin),
+        // Windows callers already express scale in physical pixels.
+        // The plugin takes logical scale and applies DPR during rasterization.
+        scale: isWindows ? cache.scale / dpr : cache.scale,
+        devicePixelRatio: dpr,
+      )
+          .then<void>((_) {}, onError: (Object error, StackTrace stack) {
+        cursor.cachedKeys.remove(key);
+        FlutterError.reportError(FlutterErrorDetails(
+            exception: error,
+            stack: stack,
+            library: 'native cursor',
+            context: ErrorDescription('registering cursor $key')));
+      }));
       cursor.addKey(key);
     }
     return FlutterCustomMemoryImageCursor(key: key);

flutter/pubspec.lock

@@ -522,9 +522,9 @@ packages:
     dependency: "direct main"
     description:
       path: "."
-      ref: db63b785c38153603e9fb84b50d3ec46f0d7e05e
-      resolved-ref: db63b785c38153603e9fb84b50d3ec46f0d7e05e
-      url: "https://github.com/rustdesk-org/flutter_custom_cursor"
+      ref: aa9e68a38b2efad7411d39ddb1a762cb2c6170eb
+      resolved-ref: aa9e68a38b2efad7411d39ddb1a762cb2c6170eb
+      url: "https://github.com/fufesou/flutter_custom_cursor"
     source: git
     version: "0.0.3"
   flutter_gpu_texture_renderer:

flutter/pubspec.yaml

@@ -62,8 +62,8 @@ dependencies:
   freezed_annotation: ^2.0.3
   flutter_custom_cursor:
     git:
-      url: https://github.com/rustdesk-org/flutter_custom_cursor
-      ref: db63b785c38153603e9fb84b50d3ec46f0d7e05e
+      url: https://github.com/fufesou/flutter_custom_cursor
+      ref: aa9e68a38b2efad7411d39ddb1a762cb2c6170eb
   window_size:
     git:
       url: https://github.com/21pages/flutter-desktop-embedding.git

flutter/test/cursor_plugin_test.dart

@@ -0,0 +1,108 @@
+// These tests drive the lifecycle normally owned by MouseTracker.
+// ignore_for_file: invalid_use_of_protected_member
+
+import 'dart:io';
+import 'dart:ui' as ui;
+
+import 'package:flutter/services.dart';
+import 'package:flutter_hbb/models/model.dart';
+import 'package:flutter_hbb/native/custom_cursor.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:image/image.dart' as img;
+
+class _CursorModel implements CursorModel {
+  @override
+  final Set<String> cachedKeys = {};
+  @override
+  void addKey(String key) => cachedKeys.add(key);
+  @override
+  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+Future<CursorData> _data() async {
+  final recorder = ui.PictureRecorder();
+  ui.Canvas(recorder).drawColor(const ui.Color(0xff123456), ui.BlendMode.src);
+  final picture = recorder.endRecording();
+  final nativeImage = await picture.toImage(20, 30);
+  picture.dispose();
+  addTearDown(nativeImage.dispose);
+  return CursorData(
+      peerId: 'plugin',
+      id: 'edit',
+      image: img.Image(width: 20, height: 30, numChannels: 4),
+      nativeImage: nativeImage,
+      scale: 1,
+      data: Uint8List.fromList([1, 2]),
+      hotxOrigin: 4,
+      hotyOrigin: 16,
+      width: 20,
+      height: 30);
+}
+
+void main() {
+  final binding = TestWidgetsFlutterBinding.ensureInitialized();
+  final view = binding.platformDispatcher.views.single;
+  final channel = Platform.isWindows
+      ? SystemChannels.mouseCursor
+      : const MethodChannel('flutter_custom_cursor');
+  late List<Map<dynamic, dynamic>> registrations;
+  setUp(() {
+    registrations = [];
+    binding.defaultBinaryMessenger.setMockMethodCallHandler(channel,
+        (call) async {
+      if (call.method.startsWith('createCustomCursor')) {
+        final args = call.arguments as Map<dynamic, dynamic>;
+        registrations.add(args);
+        return args['name'];
+      }
+      return null;
+    });
+  });
+  tearDown(() {
+    view.resetDevicePixelRatio();
+    binding.defaultBinaryMessenger.setMockMethodCallHandler(channel, null);
+  });
+
+  test('native bridge delegates rasterization and retains the minimum policy',
+      () => _checkRasterization(view, registrations));
+  test('live DPR changes invalidate a cached native cursor',
+      () => _checkDprChange(view, registrations));
+}
+
+Future<void> _checkRasterization(
+    TestFlutterView view, List<Map<dynamic, dynamic>> registrations) async {
+  view.devicePixelRatio = 2;
+  final data = await _data();
+  final originalBytes = data.data;
+  final cursor = _CursorModel();
+  final session = buildCursorOfCache(cursor, 0.5, data).createSession(1);
+  await session.activate();
+  session.dispose();
+  final args = registrations.single;
+  final pixelsPerUnit = Platform.isWindows ? 1 : 2;
+  expect(data.scale, 0.6);
+  expect(identical(data.data, originalBytes), isTrue);
+  expect(args['height'], 18 * pixelsPerUnit);
+  expect(args['width'], (Platform.isLinux ? 18 : 12) * pixelsPerUnit);
+  expect(args['imagePixelRatio'], 2.0);
+  expect(args['hotX'], Platform.isMacOS ? 4.8 : 2 * pixelsPerUnit);
+  expect(args['hotY'], Platform.isMacOS ? 19.2 : 10 * pixelsPerUnit);
+  await deleteCustomCursor(args['name'] as String);
+}
+
+Future<void> _checkDprChange(
+    TestFlutterView view, List<Map<dynamic, dynamic>> registrations) async {
+  final data = await _data();
+  final cursor = _CursorModel();
+  for (final dpr in [2.0, 1.0]) {
+    view.devicePixelRatio = dpr;
+    final session = buildCursorOfCache(cursor, 1, data).createSession(1);
+    await session.activate();
+    session.dispose();
+  }
+  expect(registrations, hasLength(2));
+  expect(registrations[0]['name'], isNot(registrations[1]['name']));
+  for (final args in registrations) {
+    await deleteCustomCursor(args['name'] as String);
+  }
+}