fix(cursor): address sizing and capture review findings

flutter/test/cursor_resize_limit_test.dart

@@ -0,0 +1,43 @@
+import 'dart:math';
+import 'dart:typed_data';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:flutter_hbb/models/model.dart';
+import 'package:image/image.dart' as img;
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  test('sparse remote artwork cannot amplify the native bitmap without limit',
+      () {
+    const sourceSize = 64;
+    const bitmapLimit = 512;
+    final image = img.Image(width: sourceSize, height: sourceSize, numChannels: 4)
+      ..setPixelRgba(0, 0, 255, 255, 255, 255);
+    final cache = CursorData(
+      peerId: 'sparse-cursor',
+      id: '1',
+      image: image,
+      scale: 1,
+      data: Uint8List.fromList(img.encodePng(image)),
+      hotxOrigin: 32,
+      hotyOrigin: 48,
+      width: sourceSize,
+      height: sourceSize,
+    )..localSize = sourceSize.toDouble();
+    final messages = <String>[];
+    final previous = debugPrint;
+    debugPrint = (String? message, {int? wrapWidth}) {
+      messages.add(message ?? '');
+    };
+    addTearDown(() => debugPrint = previous);
+
+    cache.updateGetKey(1);
+
+    expect(max(cache.scaledWidth, cache.scaledHeight), bitmapLimit);
+    expect(cache.hotx, 32 * cache.scaledWidth / sourceSize);
+    expect(cache.hoty, 48 * cache.scaledHeight / sourceSize);
+    expect(messages.single, contains('bitmap limit'));
+  });
+}