fix(flutter): preserve cursor minimum sizes and native hotspots

flutter/lib/models/model.dart

@@ -2893,7 +2893,7 @@ class CursorData {
 
   double _checkUpdateScale(double scale) {
     double oldScale = this.scale;
-    if (!_usesLogicalCursorPixels && scale != 1.0) {
+    if (scale != 1.0) {
       // Update data if scale changed.
       final tgtWidth = (width * scale).toInt();
       final tgtHeight = (height * scale).toInt();
@@ -2929,8 +2929,8 @@ class CursorData {
     }
 
     this.scale = scale;
-    hotx = hotxOrigin * (_usesLogicalCursorPixels ? scaledWidth / width : scale);
-    hoty = hotyOrigin * (_usesLogicalCursorPixels ? scaledHeight / height : scale);
+    hotx = hotxOrigin * scaledWidth / width;
+    hoty = hotyOrigin * scaledHeight / height;
     return scale;
   }
 

flutter/lib/native/custom_cursor.dart

@@ -16,8 +16,8 @@ deleteCustomCursor(String key) =>
 resetSystemCursor() {}
 
 double _nativeHotspot(double hotspot, int bitmapSize) {
-  if (!isLinux) return hotspot;
-  // GDK takes integer hotspots inside the bitmap; avoid truncating toward zero.
+  if (!isLinux && !isWindows) return hotspot;
+  // GDK and Win32 take integer hotspots inside the bitmap; use the nearest pixel.
   return min(hotspot.round(), bitmapSize - 1).toDouble();
 }
 

flutter/test/cursor_dpi_scale_test.dart

@@ -7,17 +7,31 @@ import 'package:flutter_hbb/native/custom_cursor.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:image/image.dart' as img;
 
-// Source size, source hotspot, scale, artwork size, Linux hotspot.
-const _cases = [
-  ((9, 18), (4.0, 9.0), 1 / 3, (3, 6), (1.0, 3.0)),
-  ((17, 23), (4.0, 4.0), 1 / 3, (6, 8), (1.0, 1.0)),
-  ((32, 16), (16.0, 8.0), 0.5, (16, 8), (8.0, 4.0)),
-  ((24, 24), (11.0, 11.0), 1 / 3, (8, 8), (4.0, 4.0)),
-  ((3, 3), (2.0, 2.0), 1 / 3, (1, 1), (0.0, 0.0)),
-  ((1, 48), (0.0, 24.0), 1 / 3, (1, 16), (0.0, 8.0)),
-  ((9, 18), (4.0, 9.0), 1.0, (9, 18), (4.0, 9.0)),
-  ((9, 18), (4.0, 9.0), 7 / 18, (4, 7), (2.0, 4.0)),
-  ((24, 24), (4.0, 4.0), 0.1, (2, 2), (0.0, 0.0)),
+// Source size, source hotspot, requested/effective scale, artwork size, integer hotspot.
+final _cases = [
+  ((17, 23), (4.0, 4.0), 1 / 3, 12 / 17, (12, 16), (3.0, 3.0)),
+  ((32, 16), (16.0, 8.0), 0.5, 0.75, (24, 12), (12.0, 6.0)),
+  ((34, 46), (8.0, 8.0), 0.5, 0.5, (17, 23), (4.0, 4.0)),
+  ((24, 24), (11.0, 11.0), 1 / 3, 0.5, (12, 12), (6.0, 6.0)),
+  ((1, 48), (0.0, 24.0), 1.0, 1.0, (1, 48), (0.0, 24.0)),
+  ((9, 18), (4.0, 9.0), 1.0, 1.0, (9, 18), (4.0, 9.0)),
+  ((24, 24), (4.0, 4.0), 0.1, 0.5, (12, 12), (2.0, 2.0)),
+  (
+    (19, 27),
+    (6.0, 13.0),
+    1.37,
+    1.37,
+    Platform.isWindows ? (26, 36) : (26, 37),
+    Platform.isWindows ? (8.0, 17.0) : (8.0, 18.0)
+  ),
+  (
+    (18, 36),
+    (8.0, 18.0),
+    0.75,
+    0.75,
+    Platform.isWindows ? (13, 27) : (14, 27),
+    (6.0, 14.0)
+  ),
 ];
 const _hotspotTolerance = 1e-9;
 
@@ -51,7 +65,9 @@ CursorData _cursorData((int, int) size, (double, double) hotspot) {
     id: 'native',
     image: image,
     scale: 1,
-    data: Uint8List.fromList(img.encodePng(image)),
+    data: Platform.isWindows
+        ? image.getBytes(order: img.ChannelOrder.bgra)
+        : Uint8List.fromList(img.encodePng(image)),
     hotxOrigin: hotspot.$1,
     hotyOrigin: hotspot.$2,
     width: size.$1,
@@ -61,11 +77,17 @@ CursorData _cursorData((int, int) size, (double, double) hotspot) {
 
 Future<Map<dynamic, dynamic>> _register(
     WidgetTester tester, CursorData data, double scale) async {
-  const channel = MethodChannel('flutter_custom_cursor');
+  final channel = Platform.isWindows
+      ? SystemChannels.mouseCursor
+      : const MethodChannel('flutter_custom_cursor');
   Map<dynamic, dynamic>? registered;
   tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(channel,
       (call) async {
-    expect(call.method, 'createCustomCursor');
+    expect(
+        call.method,
+        Platform.isWindows
+            ? 'createCustomCursor/windows'
+            : 'createCustomCursor');
     registered = call.arguments as Map<dynamic, dynamic>;
     return registered!['name'];
   });
@@ -129,16 +151,30 @@ void main() {
     }
   });
 
-  for (final (source, hotspot, scale, size, linuxHotspot) in _cases) {
+  for (final (source, hotspot, scale, effectiveScale, size, integerHotspot)
+      in _cases) {
     testWidgets('${source.$1}x${source.$2} cursor at scale $scale',
         (tester) async {
       final data = _cursorData(source, hotspot);
       final cursor = await _register(tester, data, scale);
-      final artwork = img.decodePng(data.data!)!;
-      final native = img.decodePng(cursor['buffer'] as Uint8List)!;
+      final artwork = Platform.isWindows
+          ? img.Image.fromBytes(
+              width: data.scaledWidth,
+              height: data.scaledHeight,
+              bytes: data.data!.buffer,
+              order: img.ChannelOrder.bgra)
+          : img.decodePng(data.data!)!;
+      final native = Platform.isWindows
+          ? img.Image.fromBytes(
+              width: cursor['width'],
+              height: cursor['height'],
+              bytes: (cursor['buffer'] as Uint8List).buffer,
+              bytesOffset: (cursor['buffer'] as Uint8List).offsetInBytes,
+              order: img.ChannelOrder.bgra)
+          : img.decodePng(cursor['buffer'] as Uint8List)!;
       final width = Platform.isLinux && size.$2 > size.$1 ? size.$2 : size.$1;
 
-      expect(data.scale, scale);
+      expect(data.scale, effectiveScale);
       expect((artwork.width, artwork.height), size);
       expect(data.hotx / size.$1,
           closeTo(hotspot.$1 / source.$1, _hotspotTolerance));
@@ -146,12 +182,15 @@ void main() {
           closeTo(hotspot.$2 / source.$2, _hotspotTolerance));
       expect((native.width, native.height), (width, size.$2));
       expect((cursor['width'], cursor['height']), (width, size.$2));
-      expect((cursor['hotX'], cursor['hotY']),
-          Platform.isLinux ? linuxHotspot : (data.hotx, data.hoty));
+      expect(
+          (cursor['hotX'], cursor['hotY']),
+          Platform.isLinux || Platform.isWindows
+              ? integerHotspot
+              : (data.hotx, data.hoty));
       _expectArtwork(native, artwork);
       if (width == artwork.width) {
         expect(cursor['buffer'], data.data);
       }
-    }, skip: Platform.isWindows);
+    });
   }
 }