fix(cursor): normalize native cursor density in scaled views

flutter/lib/desktop/pages/remote_page.dart

@@ -1105,17 +1105,22 @@ class _ImagePaintState extends State<ImagePaint> {
     // changes, so read it live to follow the window across monitors.
     final dpr = MediaQuery.devicePixelRatioOf(context);
 
-    bool isViewAdaptive() => c.viewStyle.style == kRemoteViewStyleAdaptive;
+    bool isViewScaled() =>
+        c.viewStyle.style == kRemoteViewStyleAdaptive ||
+        c.viewStyle.style == kRemoteViewStyleCustom;
     bool isViewOriginal() => c.viewStyle.style == kRemoteViewStyleOriginal;
 
     mouseRegion({child}) => Obx(() {
           double getCursorScale() {
-            var c = Provider.of<CanvasModel>(context);
+            final peerDpr = Provider.of<CursorModel>(context).cache?.pixelRatio ?? 0;
+            if (!isWeb && isViewScaled() && !zoomCursor.value && peerDpr > 0) {
+              return (isWindows ? dpr : 1.0) / peerDpr;
+            }
             var cursorScale = 1.0;
             if (isWindows) {
               // debug win10
-              if (zoomCursor.value && isViewAdaptive()) {
-                cursorScale = s * c.devicePixelRatio;
+              if (zoomCursor.value && isViewScaled()) {
+                cursorScale = s * dpr;
               }
             } else {
               if (zoomCursor.value || isViewOriginal()) {
@@ -1420,7 +1425,9 @@ class CursorPaint extends StatelessWidget {
     if (image != null && scale * nativePixels != 1.0) {
       final sx = kMinCursorSize / (image.width * nativePixels);
       final sy = kMinCursorSize / (image.height * nativePixels);
-      final minimumScale = sx > sy ? sx : sy;
+      final minimumScale = c.viewStyle.style == kRemoteViewStyleOriginal
+          ? (sx > sy ? sx : sy)
+          : (sx < sy ? sx : sy);
       if (scale < minimumScale) scale = minimumScale;
     }
     final x = (m.x * c.scale + cx) / scale - hotx;

flutter/lib/models/model.dart

@@ -2858,6 +2858,8 @@ class CursorData {
   // Borrowed from CursorModel/PredefinedCursor, which own its lifetime.
   // The plugin clones the handle before starting asynchronous encoding.
   final ui.Image nativeImage;
+  // Zero preserves sizing for peers that predate cursor density metadata.
+  final double pixelRatio;
   double scale;
   Uint8List? data;
   final double hotxOrigin;
@@ -2872,6 +2874,7 @@ class CursorData {
     required this.id,
     required this.image,
     required this.nativeImage,
+    this.pixelRatio = 0,
     required this.scale,
     required this.data,
     required this.hotxOrigin,
@@ -2885,9 +2888,13 @@ class CursorData {
 
   // 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 _checkUpdateScale(double scale,
+      {bool resizeImage = true, bool useLegacyMinimum = true}) {
     double oldScale = this.scale;
-    if (scale != 1.0) {
+    if (!useLegacyMinimum) {
+      scale = max(scale, kMinCursorSize / max(width, height));
+    }
+    if (useLegacyMinimum && scale != 1.0) {
       // Update data if scale changed.
       final tgtWidth = (width * scale).toInt();
       final tgtHeight = (height * scale).toInt();
@@ -2928,8 +2935,10 @@ class CursorData {
     return scale;
   }
 
-  String updateGetKey(double scale, {bool resizeImage = true}) {
-    scale = _checkUpdateScale(scale, resizeImage: resizeImage);
+  String updateGetKey(double scale,
+      {bool resizeImage = true, bool useLegacyMinimum = true}) {
+    scale = _checkUpdateScale(scale,
+        resizeImage: resizeImage, useLegacyMinimum: useLegacyMinimum);
     return '${peerId}_${id}_${_doubleToInt(width * scale)}_${_doubleToInt(height * scale)}';
   }
 }
@@ -3436,6 +3445,10 @@ class CursorModel with ChangeNotifier {
     final hoty = double.parse(evt['hoty']);
     final width = int.parse(evt['width']);
     final height = int.parse(evt['height']);
+    final pixelRatio = double.parse(evt['scale'] ?? '0');
+    if (!pixelRatio.isFinite || pixelRatio < 0) {
+      throw FormatException('Invalid cursor pixel ratio: $pixelRatio');
+    }
     List<dynamic> colors = json.decode(evt['colors']);
     final rgba = Uint8List.fromList(colors.map((s) => s as int).toList());
     final image = await img.decodeImageFromPixels(
@@ -3443,9 +3456,12 @@ class CursorModel with ChangeNotifier {
     if (image == null) {
       return;
     }
-    if (await _updateCache(rgba, image, id, hotx, hoty, width, height)) {
+    if (await _updateCache(rgba, image, id, hotx, hoty, width, height,
+        pixelRatio: pixelRatio)) {
       _images[id]?.item1.dispose();
       _images[id] = Tuple3(image, hotx, hoty);
+    } else {
+      image.dispose();
     }
 
     // Update last cursor data.
@@ -3460,8 +3476,9 @@ class CursorModel with ChangeNotifier {
     double hotx,
     double hoty,
     int w,
-    int h,
-  ) async {
+    int h, {
+    required double pixelRatio,
+  }) async {
     Uint8List? data;
     img2.Image imgOrigin = img2.Image.fromBytes(
         width: w, height: h, bytes: rgba.buffer, order: img2.ChannelOrder.rgba);
@@ -3471,6 +3488,7 @@ class CursorModel with ChangeNotifier {
       ByteData? imgBytes =
           await image.toByteData(format: ui.ImageByteFormat.png);
       if (imgBytes == null) {
+        debugPrint('Unable to encode cursor $id as PNG');
         return false;
       }
       data = imgBytes.buffer.asUint8List();
@@ -3480,6 +3498,7 @@ class CursorModel with ChangeNotifier {
       id: id,
       image: imgOrigin,
       nativeImage: image,
+      pixelRatio: pixelRatio,
       scale: 1.0,
       data: data,
       hotxOrigin: hotx,

flutter/lib/native/custom_cursor.dart

@@ -9,6 +9,7 @@ import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart' show WidgetsBinding;
 
 import 'package:flutter_hbb/common.dart';
+import 'package:flutter_hbb/consts.dart';
 import 'package:flutter_hbb/models/model.dart';
 
 deleteCustomCursor(String key) =>
@@ -24,7 +25,11 @@ MouseCursor buildCursorOfCache(
     // 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';
+    // Keep Original and older peers unchanged. A long-edge minimum preserves
+    // the proportions of thin remote cursors when normalizing their DPI.
+    final legacyMinimum = cache.pixelRatio == 0 ||
+        cursor.parent.target?.canvasModel.viewStyle.style == kRemoteViewStyleOriginal;
+    final key = '${cache.updateGetKey(scale, resizeImage: false, useLegacyMinimum: legacyMinimum)}_$dpr';
     if (!cursor.cachedKeys.contains(key)) {
       debugPrint(
           "Register custom cursor with key $key (${cache.hotx},${cache.hoty})");

flutter/test/cursor_dpi_policy_test.dart

@@ -0,0 +1,180 @@
+import 'dart:io';
+import 'dart:ui' as ui;
+
+import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_hbb/consts.dart';
+import 'package:flutter_hbb/desktop/pages/remote_page.dart';
+import 'package:flutter_hbb/models/input_model.dart';
+import 'package:flutter_hbb/models/model.dart';
+import 'package:flutter_hbb/native/custom_cursor.dart' show deleteCustomCursor;
+import 'package:flutter_test/flutter_test.dart';
+import 'package:get/get.dart';
+import 'package:image/image.dart' as img;
+import 'package:provider/provider.dart';
+
+const _viewport = Size(200, 160);
+
+class _Image extends ChangeNotifier implements ImageModel {
+  @override
+  bool get useTextureRender => false;
+  @override
+  ui.Image? get image => null;
+  @override
+  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+class _Canvas extends ChangeNotifier implements CanvasModel {
+  _Canvas(this.devicePixelRatio, {required this.style, required this.scale});
+
+  final String style;
+
+  @override
+  final double devicePixelRatio;
+  @override
+  final imageOverflow = false.obs;
+  @override
+  late final viewStyle = ViewStyle(
+    style: style,
+    width: _viewport.width,
+    height: _viewport.height,
+    displayWidth: 400,
+    displayHeight: 320,
+  );
+  @override
+  bool get cursorEmbedded => false;
+  @override
+  Size get size => _viewport;
+  @override
+  final double scale;
+  @override
+  double get x => 0;
+  @override
+  double get y => 0;
+  @override
+  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+class _Cursor extends ChangeNotifier implements CursorModel {
+  _Cursor(this.cache, this._ffi);
+
+  final FFI _ffi;
+  @override
+  WeakReference<FFI> get parent => WeakReference(_ffi);
+
+  @override
+  CursorData cache;
+  @override
+  ui.Image? get image => null;
+  @override
+  double get hotx => cache.hotxOrigin;
+  @override
+  double get hoty => cache.hotyOrigin;
+  @override
+  final Set<String> cachedKeys = {};
+  @override
+  void addKey(String key) => cachedKeys.add(key);
+  @override
+  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+class _Input extends Fake implements InputModel {
+  @override
+  final relativeMouseMode = false.obs;
+}
+
+class _Peer extends Fake implements FfiModel {
+  @override
+  final pi = PeerInfo();
+  @override
+  bool get isPeerLinux => false;
+}
+
+class _FFI extends Fake implements FFI {
+  _FFI(this.canvasModel);
+
+  @override
+  final CanvasModel canvasModel;
+  @override
+  final inputModel = _Input();
+  @override
+  final ffiModel = _Peer();
+}
+
+Future<CursorData> _data(int density, String id) async {
+  final image = await createTestImage(width: 9 * density, height: 18 * density);
+  return CursorData(
+    peerId: 'dpi-policy',
+    id: id,
+    image: img.Image(width: image.width, height: image.height, numChannels: 4),
+    nativeImage: image,
+    scale: 1,
+    data: null,
+    hotxOrigin: 4.0 * density,
+    hotyOrigin: 9.0 * density,
+    width: image.width,
+    height: image.height,
+    pixelRatio: density.toDouble(),
+  );
+}
+
+void main() {
+  for (final (style, zoom, density, viewScale, expectedScale) in [
+    (kRemoteViewStyleAdaptive, false, 1, 0.25, Platform.isWindows ? 2.0 : 1.0),
+    (kRemoteViewStyleAdaptive, false, 2, 0.25, Platform.isWindows ? 1.0 : 0.5),
+    (kRemoteViewStyleCustom, false, 2, 0.25, Platform.isWindows ? 1.0 : 0.5),
+    (kRemoteViewStyleAdaptive, true, 2, 0.25, 1 / 3),
+    (kRemoteViewStyleCustom, true, 2, 0.25, 1 / 3),
+    (kRemoteViewStyleOriginal, false, 2, 0.5, Platform.isWindows ? 1.0 : 2 / 3),
+  ]) {
+    testWidgets(
+        '$style zoom=$zoom peerDPR=$density keeps cursor units',
+        (tester) => tester.runAsync(() async {
+              tester.view.devicePixelRatio = 2;
+              addTearDown(tester.view.resetDevicePixelRatio);
+              final channel = Platform.isWindows
+                  ? SystemChannels.mouseCursor
+                  : const MethodChannel('flutter_custom_cursor');
+              tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(
+                  channel,
+                  (call) async => call.method.startsWith('createCustomCursor')
+                      ? (call.arguments as Map<dynamic, dynamic>)['name']
+                      : null);
+              final data = await _data(density, '$style-$zoom-$density');
+              // A stale cached DPR must not affect the cursor when the window moves.
+              final canvas = _Canvas(1, style: style, scale: viewScale);
+              final ffi = _FFI(canvas);
+              final cursor = _Cursor(data, ffi);
+              await tester.pumpWidget(MediaQuery(
+                data: const MediaQueryData(devicePixelRatio: 2),
+                child: MultiProvider(
+                    providers: [
+                      ChangeNotifierProvider<ImageModel>(
+                          create: (_) => _Image()),
+                      ChangeNotifierProvider<CanvasModel>.value(value: canvas),
+                      ChangeNotifierProvider<CursorModel>.value(value: cursor),
+                    ],
+                    child: ImagePaint(
+                      ffi: ffi,
+                      id: 'dpi-policy',
+                      zoomCursor: zoom.obs,
+                      cursorOverImage: true.obs,
+                      keyboardEnabled: true.obs,
+                      remoteCursorMoved: false.obs,
+                    )),
+              ));
+              await tester.pumpWidget(const SizedBox.shrink());
+              await Future.wait(cursor.cachedKeys.map((key) async {
+                await deleteCustomCursor(key);
+              }));
+              data.nativeImage.dispose();
+              cursor.dispose();
+              canvas.dispose();
+              tester.binding.defaultBinaryMessenger
+                  .setMockMethodCallHandler(channel, null);
+              expect(data.scale, closeTo(expectedScale, 1e-9));
+              expect(data.hotx, closeTo(4 * density * expectedScale, 1e-9));
+              expect(data.hoty, closeTo(9 * density * expectedScale, 1e-9));
+            }));
+  }
+}

flutter/test/cursor_paint_scale_test.dart

@@ -113,7 +113,7 @@ void main() {
       2.0,
       (9, 18),
       0.1,
-      Platform.isWindows ? 2 / 3 : 4 / 3,
+      Platform.isWindows ? 1 / 3 : 2 / 3,
       true
     ),
   ]) {