[web:canvaskit] migrate Paint API to UniqueRef (flutter/engine#41230)

Migrate Paint API to `UniqueRef`. This includes `Paint`, `ImageFilter` (and all subtypes), `ColorFilter` (and all subtypes).

Also fix the following memory leaks:

* `CkPaint` is frequently used by layers where a one-off paint object is created, used, and immediately dropped. `CkPaint` now has a `dispose` method, and all one-off usages now dispose of the paint after they are done.
* `CkColorFilter.initRawImageFilter` was leaking the `SkColorFilter` created by `_initRawColorFilter` inside the expression.
* `CkManagedSkImageFilterConvertible.imageFilter` now takes a closure, which allows the implementation decide on the lifetime of the `SkImageFilter` vended to the caller. Because `CkColorFilter` is a const class it cannot store C++ instances inside its own fields, so it creates a temporary `SkImageFilter` class to be used by the caller and then it needs to delete it. Now it does.

engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/canvas.dart

@@ -291,18 +291,20 @@ class CkCanvas {
 
   void saveLayerWithFilter(ui.Rect bounds, ui.ImageFilter filter,
       [CkPaint? paint]) {
-      final CkManagedSkImageFilterConvertible convertible;
-      if (filter is ui.ColorFilter) {
-        convertible = createCkColorFilter(filter as EngineColorFilter)!;
-      } else {
-        convertible = filter as CkManagedSkImageFilterConvertible;
-      }
-    return skCanvas.saveLayer(
-      paint?.skiaObject,
-      toSkRect(bounds),
-      convertible.imageFilter.skiaObject,
-      0,
-    );
+    final CkManagedSkImageFilterConvertible convertible;
+    if (filter is ui.ColorFilter) {
+      convertible = createCkColorFilter(filter as EngineColorFilter)!;
+    } else {
+      convertible = filter as CkManagedSkImageFilterConvertible;
+    }
+    convertible.imageFilter((SkImageFilter filter) {
+      skCanvas.saveLayer(
+        paint?.skiaObject,
+        toSkRect(bounds),
+        filter,
+        0,
+      );
+    });
   }
 
   void scale(double sx, double sy) {
@@ -1173,11 +1175,13 @@ class CkSaveLayerWithFilterCommand extends CkPaintCommand {
     } else {
       convertible = filter as CkManagedSkImageFilterConvertible;
     }
-    return canvas.saveLayer(
-      paint?.skiaObject,
-      toSkRect(bounds),
-      convertible.imageFilter.skiaObject,
-      0,
-    );
+    convertible.imageFilter((SkImageFilter filter) {
+      canvas.saveLayer(
+        paint?.skiaObject,
+        toSkRect(bounds),
+        filter,
+        0,
+      );
+    });
   }
 }

engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/color_filter.dart

@@ -10,31 +10,25 @@ import '../color_filter.dart';
 import '../util.dart';
 import 'canvaskit_api.dart';
 import 'image_filter.dart';
-import 'skia_object_cache.dart';
+import 'native_memory.dart';
 
-/// A concrete [ManagedSkiaObject] subclass that owns a [SkColorFilter] and
-/// manages its lifecycle.
+/// Owns a [SkColorFilter] and manages its lifecycle.
 ///
-/// Seealso:
+/// See also:
 ///
 /// * [CkPaint.colorFilter], which uses a [ManagedSkColorFilter] to manage
 ///   the lifecycle of its [SkColorFilter].
-class ManagedSkColorFilter extends ManagedSkiaObject<SkColorFilter> {
+class ManagedSkColorFilter {
   ManagedSkColorFilter(CkColorFilter ckColorFilter)
-      : colorFilter = ckColorFilter;
+      : colorFilter = ckColorFilter {
+    _ref = UniqueRef<SkColorFilter>(this, colorFilter._initRawColorFilter(), 'ColorFilter');
+  }
 
   final CkColorFilter colorFilter;
 
-  @override
-  SkColorFilter createDefault() => colorFilter._initRawColorFilter();
+  late final UniqueRef<SkColorFilter> _ref;
 
-  @override
-  SkColorFilter resurrect() => colorFilter._initRawColorFilter();
-
-  @override
-  void delete() {
-    rawSkiaObject?.delete();
-  }
+  SkColorFilter get skiaObject => _ref.nativeObject;
 
   @override
   int get hashCode => colorFilter.hashCode;
@@ -51,64 +45,83 @@ class ManagedSkColorFilter extends ManagedSkiaObject<SkColorFilter> {
   String toString() => colorFilter.toString();
 }
 
-/// A [ui.ColorFilter] backed by Skia's [SkColorFilter].
-///
-/// Additionally, this class provides the interface for converting itself to a
-/// [ManagedSkiaObject] that manages a skia image filter.
-abstract class CkColorFilter
-    implements CkManagedSkImageFilterConvertible {
+/// CanvasKit implementation of [ui.ColorFilter].
+abstract class CkColorFilter implements CkManagedSkImageFilterConvertible {
   const CkColorFilter();
 
-  /// Called by [ManagedSkiaObject.createDefault] and
-  /// [ManagedSkiaObject.resurrect] to create a new [SkImageFilter], when this
-  /// filter is used as an [ImageFilter].
-  SkImageFilter initRawImageFilter() =>
-      canvasKit.ImageFilter.MakeColorFilter(_initRawColorFilter(), null);
+  /// Converts this color filter into an image filter.
+  ///
+  /// Passes the ownership of the returned [SkImageFilter] to the caller. It is
+  /// the caller's responsibility to manage the lifecycle of the returned value.
+  SkImageFilter initRawImageFilter() {
+    final SkColorFilter skColorFilter = _initRawColorFilter();
+    final SkImageFilter result = canvasKit.ImageFilter.MakeColorFilter(skColorFilter, null);
 
-  /// Called by [ManagedSkiaObject.createDefault] and
-  /// [ManagedSkiaObject.resurrect] to create a new [SkColorFilter], when this
-  /// filter is used as a [ColorFilter].
+    // The underlying SkColorFilter is now owned by the SkImageFilter, so we
+    // need to drop the reference to allow it to be collected.
+    skColorFilter.delete();
+    return result;
+  }
+
+  /// Creates a Skia object based on the properties of this color filter.
+  ///
+  /// Passes the ownership of the returned [SkColorFilter] to the caller. It is
+  /// the caller's responsibility to manage the lifecycle of the returned value.
   SkColorFilter _initRawColorFilter();
 
   @override
-  ManagedSkiaObject<SkImageFilter> get imageFilter =>
-      CkColorFilterImageFilter(colorFilter: this);
+  void imageFilter(SkImageFilterBorrow borrow) {
+    // Since ColorFilter has a const constructor it cannot store dynamically
+    // created Skia objects. Therefore a new SkImageFilter is created every time
+    // it's used. However, once used it's no longer needed, so it's deleted
+    // immediately to free memory.
+    final SkImageFilter skImageFilter = initRawImageFilter();
+    borrow(skImageFilter);
+    skImageFilter.delete();
+  }
 }
 
+/// A reusable identity transform matrix.
+///
+/// WARNING: DO NOT MUTATE THIS MATRIX! It is a shared global singleton.
+Float32List _identityTransform = _computeIdentityTransform();
+
+Float32List _computeIdentityTransform() {
+  final Float32List result = Float32List(20);
+  const List<int> translationIndices = <int>[0, 6, 12, 18];
+  for (final int i in translationIndices) {
+    result[i] = 1;
+  }
+  _identityTransform = result;
+  return result;
+}
+
+SkColorFilter createSkColorFilterFromColorAndBlendMode(ui.Color color, ui.BlendMode blendMode) {
+  /// Return the identity matrix when the color opacity is 0. Replicates
+  /// effect of applying no filter
+  if (color.opacity == 0) {
+    return canvasKit.ColorFilter.MakeMatrix(_identityTransform);
+  }
+  final SkColorFilter? filter = canvasKit.ColorFilter.MakeBlend(
+    toSharedSkColor1(color),
+    toSkBlendMode(blendMode),
+  );
+  if (filter == null) {
+    throw ArgumentError('Invalid parameters for blend mode ColorFilter');
+  }
+  return filter;
+}
+
+
 class CkBlendModeColorFilter extends CkColorFilter {
   const CkBlendModeColorFilter(this.color, this.blendMode);
 
   final ui.Color color;
   final ui.BlendMode blendMode;
 
-  static Float32List get identityTransform => _identityTransform ?? _computeIdentityTransform();
-  static Float32List? _identityTransform;
-
-  static Float32List _computeIdentityTransform() {
-    final Float32List result = Float32List(20);
-    const List<int> translationIndices = <int>[0, 6, 12, 18];
-    for (final int i in translationIndices) {
-      result[i] = 1;
-    }
-    _identityTransform = result;
-    return result;
-  }
-
   @override
   SkColorFilter _initRawColorFilter() {
-    /// Return the identity matrix when the color opacity is 0. Replicates
-    /// effect of applying no filter
-    if (color.opacity == 0) {
-      return canvasKit.ColorFilter.MakeMatrix(identityTransform);
-    }
-    final SkColorFilter? filter = canvasKit.ColorFilter.MakeBlend(
-      toSharedSkColor1(color),
-      toSkBlendMode(blendMode),
-    );
-    if (filter == null) {
-      throw ArgumentError('Invalid parameters for blend mode ColorFilter');
-    }
-    return filter;
+    return createSkColorFilterFromColorAndBlendMode(color, blendMode);
   }
 
   @override

engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/image.dart

@@ -137,12 +137,14 @@ CkImage scaleImage(SkImage image, int? targetWidth, int? targetHeight) {
     final CkPictureRecorder recorder = CkPictureRecorder();
     final CkCanvas canvas = recorder.beginRecording(ui.Rect.largest);
 
+    final CkPaint paint = CkPaint();
     canvas.drawImageRect(
       CkImage(image),
       ui.Rect.fromLTWH(0, 0, image.width(), image.height()),
       ui.Rect.fromLTWH(0, 0, targetWidth!.toDouble(), targetHeight!.toDouble()),
-      CkPaint()
+      paint,
     );
+    paint.dispose();
 
     final CkPicture picture = recorder.endRecording();
     final ui.Image finalImage = picture.toImageSync(

engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/image_filter.dart

@@ -10,7 +10,9 @@ import 'package:ui/ui.dart' as ui;
 import '../util.dart';
 import 'canvaskit_api.dart';
 import 'color_filter.dart';
-import 'skia_object_cache.dart';
+import 'native_memory.dart';
+
+typedef SkImageFilterBorrow = void Function(SkImageFilter);
 
 /// An [ImageFilter] that can create a managed skia [SkImageFilter] object.
 ///
@@ -20,14 +22,13 @@ import 'skia_object_cache.dart';
 ///
 /// Currently implemented by [CkImageFilter] and [CkColorFilter].
 abstract class CkManagedSkImageFilterConvertible implements ui.ImageFilter {
-  ManagedSkiaObject<SkImageFilter> get imageFilter;
+  void imageFilter(SkImageFilterBorrow borrow);
 }
 
 /// The CanvasKit implementation of [ui.ImageFilter].
 ///
 /// Currently only supports `blur`, `matrix`, and ColorFilters.
-abstract class CkImageFilter extends ManagedSkiaObject<SkImageFilter>
-    implements CkManagedSkImageFilterConvertible {
+abstract class CkImageFilter implements CkManagedSkImageFilterConvertible {
   factory CkImageFilter.blur(
       {required double sigmaX,
       required double sigmaY,
@@ -39,31 +40,26 @@ abstract class CkImageFilter extends ManagedSkiaObject<SkImageFilter>
       required ui.FilterQuality filterQuality}) = _CkMatrixImageFilter;
 
   CkImageFilter._();
-
-  @override
-  ManagedSkiaObject<SkImageFilter> get imageFilter => this;
-
-  SkImageFilter _initSkiaObject();
-
-  @override
-  SkImageFilter createDefault() => _initSkiaObject();
-
-  @override
-  SkImageFilter resurrect() => _initSkiaObject();
-
-  @override
-  void delete() {
-    rawSkiaObject?.delete();
-  }
 }
 
 class CkColorFilterImageFilter extends CkImageFilter {
-  CkColorFilterImageFilter({required this.colorFilter}) : super._();
+  CkColorFilterImageFilter({required this.colorFilter}) : super._() {
+    final SkImageFilter skImageFilter = colorFilter.initRawImageFilter();
+    _ref = UniqueRef<SkImageFilter>(this, skImageFilter, 'ImageFilter.color');
+  }
 
   final CkColorFilter colorFilter;
 
+  late final UniqueRef<SkImageFilter> _ref;
+
   @override
-  SkImageFilter _initSkiaObject() => colorFilter.initRawImageFilter();
+  void imageFilter(SkImageFilterBorrow borrow) {
+    borrow(_ref.nativeObject);
+  }
+
+  void dispose() {
+    _ref.dispose();
+  }
 
   @override
   int get hashCode => colorFilter.hashCode;
@@ -84,12 +80,38 @@ class CkColorFilterImageFilter extends CkImageFilter {
 class _CkBlurImageFilter extends CkImageFilter {
   _CkBlurImageFilter(
       {required this.sigmaX, required this.sigmaY, required this.tileMode})
-      : super._();
+      : super._() {
+    /// Return the identity matrix when both sigmaX and sigmaY are 0. Replicates
+    /// effect of applying no filter
+    final SkImageFilter skImageFilter;
+    if (sigmaX == 0 && sigmaY == 0) {
+      skImageFilter = canvasKit.ImageFilter.MakeMatrixTransform(
+        toSkMatrixFromFloat32(Matrix4.identity().storage),
+        toSkFilterOptions(ui.FilterQuality.none),
+        null
+      );
+    } else {
+      skImageFilter = canvasKit.ImageFilter.MakeBlur(
+        sigmaX,
+        sigmaY,
+        toSkTileMode(tileMode),
+        null,
+      );
+    }
+    _ref = UniqueRef<SkImageFilter>(this, skImageFilter, 'ImageFilter.blur');
+  }
 
   final double sigmaX;
   final double sigmaY;
   final ui.TileMode tileMode;
 
+  late final UniqueRef<SkImageFilter> _ref;
+
+  @override
+  void imageFilter(SkImageFilterBorrow borrow) {
+    borrow(_ref.nativeObject);
+  }
+
   String get _modeString {
     switch (tileMode) {
       case ui.TileMode.clamp:
@@ -103,25 +125,6 @@ class _CkBlurImageFilter extends CkImageFilter {
     }
   }
 
-  @override
-  SkImageFilter _initSkiaObject() {
-    /// Return the identity matrix when both sigmaX and sigmaY are 0. Replicates
-    /// effect of applying no filter
-    if (sigmaX == 0 && sigmaY == 0) {
-      return canvasKit.ImageFilter.MakeMatrixTransform(
-        toSkMatrixFromFloat32(Matrix4.identity().storage),
-        toSkFilterOptions(ui.FilterQuality.none),
-        null
-      );
-    }
-    return canvasKit.ImageFilter.MakeBlur(
-      sigmaX,
-      sigmaY,
-      toSkTileMode(tileMode),
-      null,
-    );
-  }
-
   @override
   bool operator ==(Object other) {
     if (runtimeType != other.runtimeType) {
@@ -146,18 +149,23 @@ class _CkMatrixImageFilter extends CkImageFilter {
   _CkMatrixImageFilter(
       {required Float64List matrix, required this.filterQuality})
       : matrix = Float64List.fromList(matrix),
-        super._();
-
-  final Float64List matrix;
-  final ui.FilterQuality filterQuality;
-
-  @override
-  SkImageFilter _initSkiaObject() {
-    return canvasKit.ImageFilter.MakeMatrixTransform(
+        super._() {
+    final SkImageFilter skImageFilter = canvasKit.ImageFilter.MakeMatrixTransform(
       toSkMatrixFromFloat64(matrix),
       toSkFilterOptions(filterQuality),
       null,
     );
+    _ref = UniqueRef<SkImageFilter>(this, skImageFilter, 'ImageFilter.matrix');
+  }
+
+  final Float64List matrix;
+  final ui.FilterQuality filterQuality;
+
+  late final UniqueRef<SkImageFilter> _ref;
+
+  @override
+  void imageFilter(SkImageFilterBorrow borrow) {
+    borrow(_ref.nativeObject);
   }
 
   @override

engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/layer.dart

@@ -179,6 +179,7 @@ class BackdropFilterEngineLayer extends ContainerLayer
     final CkPaint paint = CkPaint()..blendMode = _blendMode;
     paintContext.internalNodesCanvas
         .saveLayerWithFilter(paintBounds, _filter, paint);
+    paint.dispose();
     paintChildren(paintContext);
     paintContext.internalNodesCanvas.restore();
   }
@@ -340,6 +341,7 @@ class OpacityEngineLayer extends ContainerLayer
     final ui.Rect saveLayerBounds = paintBounds.shift(-_offset);
 
     paintContext.internalNodesCanvas.saveLayer(saveLayerBounds, paint);
+    paint.dispose();
     paintChildren(paintContext);
     // Restore twice: once for the translate and once for the saveLayer.
     paintContext.internalNodesCanvas.restore();
@@ -403,6 +405,7 @@ class ImageFilterEngineLayer extends ContainerLayer
     final CkPaint paint = CkPaint();
     paint.imageFilter = _filter;
     paintContext.internalNodesCanvas.saveLayer(paintBounds, paint);
+    paint.dispose();
     paintChildren(paintContext);
     paintContext.internalNodesCanvas.restore();
     paintContext.internalNodesCanvas.restore();
@@ -439,6 +442,7 @@ class ShaderMaskEngineLayer extends ContainerLayer
 
     paintContext.leafNodesCanvas!.drawRect(
         ui.Rect.fromLTWH(0, 0, maskRect.width, maskRect.height), paint);
+    paint.dispose();
     paintContext.leafNodesCanvas!.restore();
 
     paintContext.internalNodesCanvas.restore();
@@ -539,6 +543,7 @@ class PhysicalShapeEngineLayer extends ContainerLayer
       // anti-aliased drawPath will always have such artifacts.
       paintContext.leafNodesCanvas!.drawPaint(paint);
     }
+    paint.dispose();
 
     paintChildren(paintContext);
 
@@ -570,6 +575,7 @@ class ColorFilterEngineLayer extends ContainerLayer
     paint.colorFilter = filter;
 
     paintContext.internalNodesCanvas.saveLayer(paintBounds, paint);
+    paint.dispose();
     paintChildren(paintContext);
     paintContext.internalNodesCanvas.restore();
   }

engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/mask_filter.dart

@@ -5,33 +5,25 @@
 import 'package:ui/ui.dart' as ui;
 
 import 'canvaskit_api.dart';
-import 'skia_object_cache.dart';
+import 'native_memory.dart';
 
 /// The CanvasKit implementation of [ui.MaskFilter].
-class CkMaskFilter extends ManagedSkiaObject<SkMaskFilter> {
+class CkMaskFilter {
   CkMaskFilter.blur(ui.BlurStyle blurStyle, double sigma)
       : _blurStyle = blurStyle,
-        _sigma = sigma;
-
-  final ui.BlurStyle _blurStyle;
-  final double _sigma;
-
-  @override
-  SkMaskFilter createDefault() => _initSkiaObject();
-
-  @override
-  SkMaskFilter resurrect() => _initSkiaObject();
-
-  SkMaskFilter _initSkiaObject() {
-    return canvasKit.MaskFilter.MakeBlur(
+        _sigma = sigma {
+    final SkMaskFilter skMaskFilter = canvasKit.MaskFilter.MakeBlur(
       toSkBlurStyle(_blurStyle),
       _sigma,
       true,
     )!;
+    _ref = UniqueRef<SkMaskFilter>(this, skMaskFilter, 'MaskFilter');
   }
 
-  @override
-  void delete() {
-    rawSkiaObject?.delete();
-  }
+  final ui.BlurStyle _blurStyle;
+  final double _sigma;
+
+  late final UniqueRef<SkMaskFilter> _ref;
+
+  SkMaskFilter get skiaObject => _ref.nativeObject;
 }

engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/painting.dart

@@ -22,11 +22,25 @@ import 'skia_object_cache.dart';
 ///
 /// This class is backed by a Skia object that must be explicitly
 /// deleted to avoid a memory leak. This is done by extending [SkiaObject].
-class CkPaint extends ManagedSkiaObject<SkPaint> implements ui.Paint {
-  CkPaint();
+class CkPaint implements ui.Paint {
+  CkPaint() : skiaObject = SkPaint() {
+    skiaObject.setAntiAlias(_isAntiAlias);
+    skiaObject.setColorInt(_defaultPaintColor.toDouble());
+    _ref = UniqueRef<SkPaint>(this, skiaObject, 'Paint');
+  }
+
+  final SkPaint skiaObject;
+  late final UniqueRef<SkPaint> _ref;
+  CkManagedSkImageFilterConvertible? _imageFilter;
 
   static const int _defaultPaintColor = 0xFF000000;
 
+  /// Returns the native reference to the underlying [SkPaint] object.
+  ///
+  /// This should only be used in tests.
+  @visibleForTesting
+  UniqueRef<SkPaint> get debugRef => _ref;
+
   @override
   ui.BlendMode get blendMode => _blendMode;
   @override
@@ -260,50 +274,28 @@ class CkPaint extends ManagedSkiaObject<SkPaint> implements ui.Paint {
     if (_imageFilter == value) {
       return;
     }
+    final CkManagedSkImageFilterConvertible? filter;
     if (value is ui.ColorFilter) {
-      _imageFilter = createCkColorFilter(value as EngineColorFilter);
+      filter = createCkColorFilter(value as EngineColorFilter);
     }
     else {
-      _imageFilter = value as CkManagedSkImageFilterConvertible?;
+      filter = value as CkManagedSkImageFilterConvertible?;
     }
-    _managedImageFilter = _imageFilter?.imageFilter;
-    skiaObject.setImageFilter(_managedImageFilter?.skiaObject);
+
+    if (filter != null) {
+      filter.imageFilter((SkImageFilter skImageFilter) {
+        skiaObject.setImageFilter(skImageFilter);
+      });
+    }
+
+    _imageFilter = filter;
   }
 
-  CkManagedSkImageFilterConvertible? _imageFilter;
-  ManagedSkiaObject<SkImageFilter>? _managedImageFilter;
-
-  @override
-  SkPaint createDefault() {
-    final SkPaint paint = SkPaint();
-    paint.setAntiAlias(_isAntiAlias);
-    paint.setColorInt(_color.toDouble());
-    return paint;
-  }
-
-  @override
-  SkPaint resurrect() {
-    final SkPaint paint = SkPaint();
-    // No need to do anything for `invertColors`. If it was set, then it
-    // updated `_managedColorFilter`.
-    paint.setBlendMode(toSkBlendMode(_blendMode));
-    paint.setStyle(toSkPaintStyle(_style));
-    paint.setStrokeWidth(_strokeWidth);
-    paint.setAntiAlias(_isAntiAlias);
-    paint.setColorInt(_color.toDouble());
-    paint.setShader(_shader?.getSkShader(_filterQuality));
-    paint.setMaskFilter(_ckMaskFilter?.skiaObject);
-    paint.setColorFilter(_effectiveColorFilter?.skiaObject);
-    paint.setImageFilter(_managedImageFilter?.skiaObject);
-    paint.setStrokeCap(toSkStrokeCap(_strokeCap));
-    paint.setStrokeJoin(toSkStrokeJoin(_strokeJoin));
-    paint.setStrokeMiter(_strokeMiterLimit);
-    return paint;
-  }
-
-  @override
-  void delete() {
-    rawSkiaObject?.delete();
+  /// Disposes of this paint object.
+  ///
+  /// This object cannot be used again after calling this method.
+  void dispose() {
+    _ref.dispose();
   }
 }
 

engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/text.dart

@@ -13,7 +13,6 @@ import 'font_fallbacks.dart';
 import 'native_memory.dart';
 import 'painting.dart';
 import 'renderer.dart';
-import 'skia_object_cache.dart';
 import 'text_fragmenter.dart';
 import 'util.dart';
 
@@ -552,16 +551,6 @@ SkFontStyle toSkFontStyle(ui.FontWeight? fontWeight, ui.FontStyle? fontStyle) {
 }
 
 /// The CanvasKit implementation of [ui.Paragraph].
-///
-/// This class does not use [ManagedSkiaObject] because it requires that its
-/// memory is reclaimed synchronously. This protects our memory usage from
-/// blowing up if within a single frame the framework needs to layout a lot of
-/// paragraphs. One common use-case is `ListView.builder`, which needs to layout
-/// more of its content than it actually renders to compute the scroll position.
-/// More generally, this protects from the pattern of laying out a lot of text
-/// while painting a small subset of it. To achieve this a
-/// [SynchronousSkiaObjectCache] is used that limits the number of live laid out
-/// paragraphs at any point in time within or outside the frame.
 class CkParagraph implements ui.Paragraph {
   CkParagraph(SkParagraph skParagraph, this._paragraphStyle) {
     _ref = UniqueRef<SkParagraph>(this, skParagraph, 'Paragraph');

engine/src/flutter/lib/web_ui/test/canvaskit/filter_test.dart

@@ -52,8 +52,11 @@ void testMain() {
     test('can be constructed', () {
       final CkImageFilter imageFilter = CkImageFilter.blur(sigmaX: 5, sigmaY: 10, tileMode: ui.TileMode.clamp);
       expect(imageFilter, isA<CkImageFilter>());
-      expect(imageFilter.createDefault(), isNotNull);
-      expect(imageFilter.resurrect(), isNotNull);
+      SkImageFilter? skFilter;
+      imageFilter.imageFilter((SkImageFilter value) {
+        skFilter = value;
+      });
+      expect(skFilter, isNotNull);
     });
 
 
@@ -82,11 +85,12 @@ void testMain() {
       final CkPaint paint = CkPaint();
       paint.imageFilter = CkImageFilter.blur(sigmaX: 5, sigmaY: 10, tileMode: ui.TileMode.clamp);
 
-      final ManagedSkiaObject<Object> managedFilter = paint.imageFilter! as ManagedSkiaObject<Object>;
-      final Object skiaFilter = managedFilter.skiaObject;
+      final CkManagedSkImageFilterConvertible managedFilter1 = paint.imageFilter! as CkManagedSkImageFilterConvertible;
 
       paint.imageFilter = CkImageFilter.blur(sigmaX: 5, sigmaY: 10, tileMode: ui.TileMode.clamp);
-      expect((paint.imageFilter! as ManagedSkiaObject<Object>).skiaObject, same(skiaFilter));
+      final CkManagedSkImageFilterConvertible managedFilter2 = paint.imageFilter! as CkManagedSkImageFilterConvertible;
+
+      expect(managedFilter1, same(managedFilter2));
     });
 
     test('does not throw for both sigmaX and sigmaY set to 0', () async {

engine/src/flutter/lib/web_ui/test/canvaskit/painting_test.dart

@@ -0,0 +1,34 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:test/bootstrap/browser.dart';
+import 'package:test/test.dart';
+
+import 'package:ui/src/engine.dart';
+
+import '../common/matchers.dart';
+import 'common.dart';
+
+void main() {
+  internalBootstrapBrowserTest(() => testMain);
+}
+
+void testMain() {
+  group('CkPaint', () {
+    setUpCanvasKitTest();
+
+    test('lifecycle', () {
+      final CkPaint paint = CkPaint();
+      expect(paint.skiaObject, isNotNull);
+      expect(paint.debugRef.isDisposed, isFalse);
+      paint.dispose();
+      expect(paint.debugRef.isDisposed, isTrue);
+      expect(
+        reason: 'Cannot dispose more than once',
+        () => paint.dispose(),
+        throwsA(isAssertionError),
+      );
+    });
+  });
+}