fix paint memory management

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(

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();
   }

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
@@ -277,38 +291,11 @@ class CkPaint extends ManagedSkiaObject<SkPaint> implements ui.Paint {
     _imageFilter = filter;
   }
 
-  CkManagedSkImageFilterConvertible? _imageFilter;
-
-  @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.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();
   }
 }
 

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),
+      );
+    });
+  });
+}