Remove double-referencing from CkImage to SkImage (#22415)

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

@@ -46,22 +46,18 @@ Future<ui.Codec> skiaInstantiateWebImageCodec(
 
 /// A wrapper for `SkAnimatedImage`.
 class CkAnimatedImage implements ui.Image {
-  final SkAnimatedImage _skAnimatedImage;
-
   // Use a box because `SkImage` may be deleted either due to this object
   // being garbage-collected, or by an explicit call to [delete].
-  late final SkiaObjectBox box;
+  late final SkiaObjectBox<SkAnimatedImage> box;
 
-  CkAnimatedImage(SkAnimatedImage skAnimatedImage)
-      : this._(skAnimatedImage, null);
+  SkAnimatedImage get _skAnimatedImage => box.skObject;
 
-  CkAnimatedImage._(this._skAnimatedImage, SkiaObjectBox? boxToClone) {
-    if (boxToClone != null) {
-      assert(boxToClone.skObject == _skAnimatedImage);
-      box = boxToClone.clone(this);
-    } else {
-      box = SkiaObjectBox(this, _skAnimatedImage as SkDeletable);
-    }
+  CkAnimatedImage(SkAnimatedImage skAnimatedImage) {
+    box = SkiaObjectBox<SkAnimatedImage>(this, skAnimatedImage);
+  }
+
+  CkAnimatedImage.cloneOf(SkiaObjectBox<SkAnimatedImage> boxToClone) {
+    box = boxToClone.clone(this);
   }
 
   bool _disposed = false;
@@ -80,7 +76,7 @@ class CkAnimatedImage implements ui.Image {
         'Image.debugDisposed is only available when asserts are enabled.');
   }
 
-  ui.Image clone() => CkAnimatedImage._(_skAnimatedImage, box);
+  ui.Image clone() => CkAnimatedImage.cloneOf(box);
 
   @override
   bool isCloneOf(ui.Image other) {
@@ -143,21 +139,18 @@ class CkAnimatedImage implements ui.Image {
 
 /// A [ui.Image] backed by an `SkImage` from Skia.
 class CkImage implements ui.Image {
-  final SkImage skImage;
-
   // Use a box because `SkImage` may be deleted either due to this object
   // being garbage-collected, or by an explicit call to [delete].
-  late final SkiaObjectBox box;
+  late final SkiaObjectBox<SkImage> box;
 
-  CkImage(SkImage skImage) : this._(skImage, null);
+  SkImage get skImage => box.skObject;
 
-  CkImage._(this.skImage, SkiaObjectBox? boxToClone) {
-    if (boxToClone != null) {
-      assert(boxToClone.skObject == skImage);
-      box = boxToClone.clone(this);
-    } else {
-      box = SkiaObjectBox(this, skImage as SkDeletable);
-    }
+  CkImage(SkImage skImage) {
+    box = SkiaObjectBox<SkImage>(this, skImage);
+  }
+
+  CkImage.cloneOf(SkiaObjectBox<SkImage> boxToClone) {
+    box = boxToClone.clone(this);
   }
 
   bool _disposed = false;
@@ -180,7 +173,7 @@ class CkImage implements ui.Image {
   }
 
   @override
-  ui.Image clone() => CkImage._(skImage, box);
+  ui.Image clone() => CkImage.cloneOf(box);
 
   @override
   bool isCloneOf(ui.Image other) {

lib/web_ui/lib/src/engine/canvaskit/shader.dart

@@ -162,15 +162,15 @@ class CkGradientConical extends CkShader implements ui.Gradient {
 class CkImageShader extends CkShader implements ui.ImageShader {
   CkImageShader(
       ui.Image image, this.tileModeX, this.tileModeY, this.matrix4)
-      : _skImage = image as CkImage;
+      : _image = image as CkImage;
 
   final ui.TileMode tileModeX;
   final ui.TileMode tileModeY;
   final Float64List matrix4;
-  final CkImage _skImage;
+  final CkImage _image;
 
   @override
-  SkShader createDefault() => _skImage.skImage.makeShader(
+  SkShader createDefault() => _image.skImage.makeShader(
     toSkTileMode(tileModeX),
     toSkTileMode(tileModeY),
     toSkMatrixFromFloat64(matrix4),

lib/web_ui/lib/src/engine/canvaskit/skia_object_cache.dart

@@ -250,11 +250,11 @@ abstract class OneShotSkiaObject<T extends Object> extends SkiaObject<T> {
 ///
 /// The [delete] method may be called any number of times. The box
 /// will only delete the object once.
-class SkiaObjectBox {
-  SkiaObjectBox(Object wrapper, SkDeletable skObject)
-      : this._(wrapper, skObject, <SkiaObjectBox>{});
+class SkiaObjectBox<T> {
+  SkiaObjectBox(Object wrapper, T skObject)
+      : this._(wrapper, skObject, skObject as SkDeletable, <SkiaObjectBox>{});
 
-  SkiaObjectBox._(Object wrapper, this.skObject, this._refs) {
+  SkiaObjectBox._(Object wrapper, this.skObject, this._skDeletable, this._refs) {
     if (assertionsEnabled) {
       _debugStackTrace = StackTrace.current;
     }
@@ -280,7 +280,8 @@ class SkiaObjectBox {
   }
 
   /// The Skia object whose lifecycle is being managed.
-  final SkDeletable skObject;
+  final T skObject;
+  final SkDeletable _skDeletable;
 
   /// Whether this object has been deleted.
   bool get isDeleted => _isDeleted;
@@ -295,10 +296,10 @@ class SkiaObjectBox {
   /// Returns a clone of this object, which increases its reference count.
   ///
   /// Clones must be [dispose]d when finished.
-  SkiaObjectBox clone(Object wrapper) {
+  SkiaObjectBox<T> clone(Object wrapper) {
     assert(!_isDeleted, 'Cannot clone from a deleted handle.');
     assert(_refs.isNotEmpty);
-    return SkiaObjectBox._(wrapper, skObject, _refs);
+    return SkiaObjectBox<T>._(wrapper, skObject, _skDeletable, _refs);
   }
 
   /// Decrements the reference count for the [skObject].
@@ -316,7 +317,7 @@ class SkiaObjectBox {
     assert(removed);
     _isDeleted = true;
     if (_refs.isEmpty) {
-      _scheduleSkObjectCollection(skObject);
+      _scheduleSkObjectCollection(_skDeletable);
     }
   }
 }

lib/web_ui/test/canvaskit/skia_objects_cache_test.dart

@@ -155,13 +155,11 @@ void _tests() {
     });
   });
 
-
   group(SkiaObjectBox, () {
     test('Records stack traces and respects refcounts', () async {
-      TestOneShotSkiaObject.deleteCount = 0;
-      final TestOneShotSkiaObject skObject = TestOneShotSkiaObject();
+      TestSkDeletable.deleteCount = 0;
       final Object wrapper = Object();
-      final SkiaObjectBox box = SkiaObjectBox(wrapper, skObject);
+      final SkiaObjectBox<TestSkDeletable> box = SkiaObjectBox<TestSkDeletable>(wrapper, TestSkDeletable());
 
       expect(box.debugGetStackTraces().length, 1);
 
@@ -178,7 +176,7 @@ void _tests() {
 
       // Let any timers elapse.
       await Future<void>.delayed(Duration.zero);
-      expect(TestOneShotSkiaObject.deleteCount, 0);
+      expect(TestSkDeletable.deleteCount, 0);
 
       expect(clone.debugGetStackTraces().length, 1);
       expect(box.debugGetStackTraces().length, 1);
@@ -188,7 +186,7 @@ void _tests() {
 
       // Let any timers elapse.
       await Future<void>.delayed(Duration.zero);
-      expect(TestOneShotSkiaObject.deleteCount, 1);
+      expect(TestSkDeletable.deleteCount, 1);
 
       expect(clone.debugGetStackTraces().length, 0);
       expect(box.debugGetStackTraces().length, 0);
@@ -196,6 +194,15 @@ void _tests() {
   });
 }
 
+class TestSkDeletable implements SkDeletable {
+  static int deleteCount = 0;
+
+  @override
+  void delete() {
+    deleteCount++;
+  }
+}
+
 class TestOneShotSkiaObject extends OneShotSkiaObject<SkPaint> implements SkDeletable {
   static int deleteCount = 0;