Fix predefined cursor density and scrollbar centering

flutter/lib/desktop/pages/remote_page.dart

@@ -1113,7 +1113,11 @@ class _ImagePaintState extends State<ImagePaint> {
     mouseRegion({child}) => Obx(() {
           double getCursorScale() {
             final cursor = Provider.of<CursorModel>(context);
-            final peerDpr = cursor.cache?.pixelRatio ?? 0;
+            // Predefined artwork must not inherit the cached remote bitmap's DPI.
+            final cache = keyboardEnabled.isTrue
+                ? cursor.cache ?? preDefaultCursor.cache
+                : preForbiddenCursor.cache;
+            final peerDpr = cache?.pixelRatio ?? 0;
             if (!isWeb && isViewScaled() && !zoomCursor.value && peerDpr > 0) {
               return (isWindows ? dpr : 1.0) / peerDpr;
             }
@@ -1417,9 +1421,10 @@ class CursorPaint extends StatelessWidget {
       // Pan offsets can be stale after leaving the image; scrollbars do not use them.
       final imageWidth = rect.width * c.scale;
       final imageHeight = rect.height * c.scale;
-      cx = (c.size.width > imageWidth ? (c.size.width - imageWidth) / 2 : 0) -
+      // Match the integer centering in _buildCrossScrollbarFromLayout.
+      cx = (c.size.width > imageWidth ? (c.size.width - imageWidth) ~/ 2 : 0) -
           imageWidth * c.scrollX;
-      cy = (c.size.height > imageHeight ? (c.size.height - imageHeight) / 2 : 0) -
+      cy = (c.size.height > imageHeight ? (c.size.height - imageHeight) ~/ 2 : 0) -
           imageHeight * c.scrollY;
     }
 

flutter/test/cursor_dpi_policy_test.dart

@@ -4,6 +4,7 @@ import 'dart:ui' as ui;
 
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
+import 'package:flutter_custom_cursor/cursor_manager.dart' show CursorManager;
 import 'package:flutter_hbb/consts.dart';
 import 'package:flutter_hbb/desktop/pages/remote_page.dart';
 import 'package:flutter_hbb/models/input_model.dart';
@@ -167,6 +168,9 @@ void main() {
   test('live DPR changes invalidate a cached native cursor',
       () => _checkDprChange(view, registrations));
   for (final style in [kRemoteViewStyleAdaptive, kRemoteViewStyleCustom]) {
+    testWidgets('$style forbidden cursor ignores remote DPR', (tester) =>
+        tester.runAsync(() => _checkPolicy(tester,
+            (style, false, 2, 0.25, 0.5), registrations, dpr: 1)));
     testWidgets('Linux $style zoom follows video pixels', (tester) => tester.runAsync(
         () => _checkPolicy(tester, (style, true, 2, 1.0, windows ? 1.0 : 0.5),
             registrations, linux: true)));
@@ -176,9 +180,10 @@ void main() {
 Future<void> _checkPolicy(
     WidgetTester tester,
     (String, bool, int, double, double) testCase,
-    List<Map<dynamic, dynamic>> registrations, {bool linux = false}) async {
+    List<Map<dynamic, dynamic>> registrations,
+    {bool linux = false, double dpr = 2}) async {
   final (style, zoom, density, viewScale, expectedScale) = testCase;
-  tester.view.devicePixelRatio = 2;
+  tester.view.devicePixelRatio = dpr;
   final data = await _data(density, '$style-$zoom-$density');
   final originalBytes = data.data;
   // A stale cached DPR must not affect the cursor when the window moves.
@@ -187,8 +192,9 @@ Future<void> _checkPolicy(
   ffi.ffiModel.isPeerLinux = linux;
   if (linux) ffi.ffiModel.pi.displays.add(_LinuxDisplay());
   final cursor = _Cursor(data, ffi);
+  final keyboardEnabled = true.obs;
   await tester.pumpWidget(MediaQuery(
-    data: const MediaQueryData(devicePixelRatio: 2),
+    data: MediaQueryData(devicePixelRatio: dpr),
     child: MultiProvider(
         providers: [
           ChangeNotifierProvider<ImageModel>(create: (_) => _Image()),
@@ -200,10 +206,17 @@ Future<void> _checkPolicy(
           id: 'dpi-policy',
           zoomCursor: zoom.obs,
           cursorOverImage: true.obs,
-          keyboardEnabled: true.obs,
+          keyboardEnabled: keyboardEnabled,
           remoteCursorMoved: false.obs,
         )),
   ));
+  final revoke = !zoom && style != kRemoteViewStyleOriginal;
+  if (revoke) {
+    await Future.wait(cursor.cachedKeys
+        .map(CursorManager.instance.ensureCursorRegistered));
+    keyboardEnabled.value = false;
+    await tester.pump();
+  }
   await tester.pumpWidget(const SizedBox.shrink());
   for (final key in cursor.cachedKeys) {
     await deleteCustomCursor(key);
@@ -215,11 +228,17 @@ Future<void> _checkPolicy(
   expect(data.hotx, closeTo(data.hotxOrigin * expectedScale, 1e-9));
   expect(data.hoty, closeTo(data.hotyOrigin * expectedScale, 1e-9));
   expect(data.data, same(originalBytes));
+  if (revoke) {
+    final args = registrations.last;
+    expect(args['name'], contains('_${kPreForbiddenCursorId}_'));
+    expect((args['width'], args['height']), (32, 32));
+    expect((args['hotX'], args['hotY']), (0.0, 0.0));
+  }
   if (style == kRemoteViewStyleAdaptive && !zoom && density > 0) {
-    final args = registrations.single;
+    final args = registrations.first;
-    expect((args['width'], args['height']), (Platform.isLinux ? 36 : 18, 36));
+    expect((args['width'], args['height']), ((Platform.isLinux ? 18 : 9) * dpr, 18 * dpr));
-    expect((args['hotX'], args['hotY']), (8.0, 18.0));
+    expect((args['hotX'], args['hotY']), (4 * dpr, 9 * dpr));
-    expect(args['imagePixelRatio'], 2.0);
+    expect(args['imagePixelRatio'], dpr);
   }
 }
 

flutter/test/cursor_paint_scale_test.dart

@@ -118,16 +118,18 @@ class _CanvasModel extends ChangeNotifier implements CanvasModel {
 }
 
 class _ScrollbarCanvasModel extends _CanvasModel {
-  _ScrollbarCanvasModel(String style) : super(style, 2, true) {
+  _ScrollbarCanvasModel(String style, {Size? frame, double scale = 2})
+      : super(style, scale, true) {
     imageOverflow.value = true;
+    if (frame != null) _ffi.ffiModel.rect = Offset.zero & frame;
   }
 
   @override
   ScrollStyle get scrollStyle => ScrollStyle.scrollbar;
   @override
-  double get scrollX => 0.1;
+  double get scrollX => _ffi.ffiModel.rect.width * scale > size.width ? 0.1 : 0;
   @override
-  double get scrollY => 0.2;
+  double get scrollY => _ffi.ffiModel.rect.height * scale > size.height ? 0.2 : 0;
 }
 
 class _Canvas extends Fake implements Canvas {
@@ -249,12 +251,20 @@ void main() {
     });
   }
   for (final style in [kRemoteViewStyleOriginal, kRemoteViewStyleCustom]) {
-    testWidgets('$style painted cursor follows scrollbar position',
+    for (final (frame, scale, offset) in [
-        (tester) async {
+      (_viewport, 2.0, const Offset(-40, -64)),
-      final painter = await _paintCursor(tester, _ScrollbarCanvasModel(style));
+      (const Size(199, 320), 1.0, const Offset(0, -64)),
-      final target = _remotePosition * 2 -
+      (const Size(198, 320), 1.0, const Offset(1, -64)),
-          Offset(_viewport.width * 2 * 0.1, _viewport.height * 2 * 0.2);
+      (const Size(400, 159), 1.0, const Offset(-40, 0)),
-      expect((Offset(painter.x, painter.y) + _hotspot) * painter.scale, target);
+      (const Size(400, 158), 1.0, const Offset(-40, 1)),
-    });
+    ]) {
+      testWidgets('$style frame=$frame painted cursor follows scrollbar layout',
+          (tester) async {
+        final painter = await _paintCursor(
+            tester, _ScrollbarCanvasModel(style, frame: frame, scale: scale));
+        final target = _remotePosition * scale + offset;
+        expect((Offset(painter.x, painter.y) + _hotspot) * painter.scale, target);
+      });
+    }
   }
 }