fix: Dispose codec after completing frame creation (flutter#159945)

ref flutter#93404,
[comment](flutter#93404 (comment))
and
[comment](flutter#93404 (comment)).

Added a process to call `ui.Codec`'s `dispose`.
With this change,
[HtmlBlobCodec](https://github.com/flutter/flutter/blob/8e0993eda8b0bbf0e11162cf18df1effd134db09/engine/src/flutter/lib/web_ui/lib/src/engine/html_image_element_codec.dart#L100)'s
dispose will be called in Safari when using CanvasKit, and
`revokeObjectURL` will be executed as expected.

* https://api.flutter.dev/flutter/dart-ui/Codec/dispose.html
* https://bugs.webkit.org/show_bug.cgi?id=31253
*
https://developer.mozilla.org/en-US/docs/Web/API/URL/createObjectURL_static
*
https://developer.mozilla.org/en-US/docs/Web/API/URL/revokeObjectURL_static

If this fix looks good, I will open the
flutter#161481 to remove the
`AlearmClock` from the `BrowserImageDecoder`.

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Author: koji-1009

engine/src/flutter/lib/ui/painting.dart

@@ -2630,7 +2630,12 @@ void decodeImageFromList(Uint8List list, ImageDecoderCallback callback) {
 
 Future<void> _decodeImageFromListAsync(Uint8List list, ImageDecoderCallback callback) async {
   final Codec codec = await instantiateImageCodec(list);
-  final FrameInfo frameInfo = await codec.getNextFrame();
+  final FrameInfo frameInfo;
+  try {
+    frameInfo = await codec.getNextFrame();
+  } finally {
+    codec.dispose();
+  }
   callback(frameInfo.image);
 }
 

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

@@ -695,7 +695,12 @@ void decodeImageFromList(Uint8List list, ImageDecoderCallback callback) {
 
 Future<void> _decodeImageFromListAsync(Uint8List list, ImageDecoderCallback callback) async {
   final Codec codec = await instantiateImageCodec(list);
-  final FrameInfo frameInfo = await codec.getNextFrame();
+  final FrameInfo frameInfo;
+  try {
+    frameInfo = await codec.getNextFrame();
+  } finally {
+    codec.dispose();
+  }
   callback(frameInfo.image);
 }
 

packages/flutter/lib/src/painting/image_decoder.dart

@@ -25,6 +25,11 @@ import 'binding.dart';
 Future<ui.Image> decodeImageFromList(Uint8List bytes) async {
   final ui.ImmutableBuffer buffer = await ui.ImmutableBuffer.fromUint8List(bytes);
   final ui.Codec codec = await PaintingBinding.instance.instantiateImageCodecWithSize(buffer);
-  final ui.FrameInfo frameInfo = await codec.getNextFrame();
+  final ui.FrameInfo frameInfo;
+  try {
+    frameInfo = await codec.getNextFrame();
+  } finally {
+    codec.dispose();
+  }
   return frameInfo.image;
 }

packages/flutter/lib/src/painting/image_stream.dart

@@ -980,7 +980,8 @@ class MultiFrameImageStreamCompleter extends ImageStreamCompleter {
   /// Immediately starts decoding the first image frame when the codec is ready.
   ///
   /// The `codec` parameter is a future for an initialized [ui.Codec] that will
-  /// be used to decode the image.
+  /// be used to decode the image. This completer takes ownership of the passed
+  /// `codec` and will dispose it once it is no longer needed.
   ///
   /// The `scale` parameter is the linear scale factor for drawing this frames
   /// of this image at their intended size.
@@ -1071,7 +1072,11 @@ class MultiFrameImageStreamCompleter extends ImageStreamCompleter {
       final int completedCycles = _framesEmitted ~/ _codec!.frameCount;
       if (_codec!.repetitionCount == -1 || completedCycles <= _codec!.repetitionCount) {
         _decodeNextFrameAndSchedule();
+        return;
       }
+
+      _codec!.dispose();
+      _codec = null;
       return;
     }
     final Duration delay = _frameDuration! - (timestamp - _shownTimestamp);
@@ -1105,6 +1110,11 @@ class MultiFrameImageStreamCompleter extends ImageStreamCompleter {
       );
       return;
     }
+    if (_codec == null) {
+      // codec was disposed during getNextFrame
+      return;
+    }
+
     if (_codec!.frameCount == 1) {
       // ImageStreamCompleter listeners removed while waiting for next frame to
       // be decoded.
@@ -1119,6 +1129,9 @@ class MultiFrameImageStreamCompleter extends ImageStreamCompleter {
       );
       _nextFrame!.image.dispose();
       _nextFrame = null;
+
+      _codec!.dispose();
+      _codec = null;
       return;
     }
     _scheduleAppFrame();
@@ -1161,6 +1174,9 @@ class MultiFrameImageStreamCompleter extends ImageStreamCompleter {
       _chunkSubscription?.onData(null);
       _chunkSubscription?.cancel();
       _chunkSubscription = null;
+
+      _codec?.dispose();
+      _codec = null;
     }
   }
 }

packages/flutter/test/painting/image_stream_test.dart

@@ -41,10 +41,16 @@ class MockCodec implements Codec {
 
   int numFramesAsked = 0;
 
+  bool disposed = false;
+
   Completer<FrameInfo> _nextFrameCompleter = Completer<FrameInfo>();
 
   @override
   Future<FrameInfo> getNextFrame() {
+    if (disposed) {
+      throw StateError('Codec is disposed');
+    }
+
     numFramesAsked += 1;
     return _nextFrameCompleter.future;
   }
@@ -59,7 +65,13 @@ class MockCodec implements Codec {
   }
 
   @override
-  void dispose() {}
+  void dispose() {
+    if (disposed) {
+      throw StateError('Codec is already disposed');
+    }
+
+    disposed = true;
+  }
 }
 
 class FakeEventReportingImageStreamCompleter extends ImageStreamCompleter {
@@ -106,6 +118,7 @@ void main() {
     imageStream.addListener(ImageStreamListener(listener));
     await tester.idle();
     expect(mockCodec.numFramesAsked, 1);
+    expect(mockCodec.disposed, false);
   });
 
   testWidgets('Decoding starts when a codec is ready after a listener is added', (
@@ -130,6 +143,7 @@ void main() {
     completer.complete(mockCodec);
     await tester.idle();
     expect(mockCodec.numFramesAsked, 1);
+    expect(mockCodec.disposed, false);
   });
 
   testWidgets('Decoding does not crash when disposed', (WidgetTester tester) async {
@@ -156,7 +170,9 @@ void main() {
 
     final FrameInfo frame = FakeFrameInfo(const Duration(milliseconds: 200), image20x10);
     mockCodec.completeNextFrame(frame);
+    expect(mockCodec.disposed, false);
     imageStream.removeListener(streamListener);
+    expect(mockCodec.disposed, true);
     await tester.idle();
   });
 
@@ -334,6 +350,7 @@ void main() {
     await tester.idle();
 
     expect(tester.takeException(), 'frame completion error');
+    expect(mockCodec.disposed, false);
   });
 
   testWidgets('ImageStream emits frame (static image)', (WidgetTester tester) async {
@@ -362,7 +379,9 @@ void main() {
 
     final FrameInfo frame = FakeFrameInfo(const Duration(milliseconds: 200), image20x10);
     mockCodec.completeNextFrame(frame);
+    expect(mockCodec.disposed, false);
     await tester.idle();
+    expect(mockCodec.disposed, true);
 
     expect(emittedImages.every((ImageInfo info) => info.image.isCloneOf(frame.image)), true);
 
@@ -420,7 +439,9 @@ void main() {
     // quit the test without pending timers.
     await tester.pump(const Duration(milliseconds: 400));
 
+    expect(mockCodec.disposed, false);
     imageStream.removeListener(listener);
+    expect(mockCodec.disposed, true);
     imageCache.clear();
   });
 
@@ -469,7 +490,9 @@ void main() {
     // quit the test without pending timers.
     await tester.pump(const Duration(milliseconds: 200));
 
+    expect(mockCodec.disposed, false);
     imageStream.removeListener(listener);
+    expect(mockCodec.disposed, true);
     imageCache.clear();
   });
 
@@ -505,7 +528,9 @@ void main() {
     await tester.pump(); // first animation frame shows on first app frame.
     mockCodec.completeNextFrame(frame2);
     await tester.idle(); // let nextFrameFuture complete
+    expect(mockCodec.disposed, false);
     await tester.pump(const Duration(milliseconds: 200)); // emit 2nd frame.
+    expect(mockCodec.disposed, true);
     mockCodec.completeNextFrame(frame1);
     // allow another frame to complete (but we shouldn't be asking for it as
     // this animation should not repeat.
@@ -562,7 +587,9 @@ void main() {
     expect(mockCodec.numFramesAsked, 3);
 
     handle.dispose();
+    expect(mockCodec.disposed, false);
     imageStream.removeListener(listener);
+    expect(mockCodec.disposed, true);
     imageCache.clear();
   });
 
@@ -619,7 +646,9 @@ void main() {
     expect(emittedImages2[0].image.isCloneOf(frame1.image), true);
     expect(emittedImages2[1].image.isCloneOf(frame2.image), true);
 
+    expect(mockCodec.disposed, false);
     imageStream.removeListener(listener2);
+    expect(mockCodec.disposed, true);
   });
 
   testWidgets('timer is canceled when listeners are removed', (WidgetTester tester) async {
@@ -653,7 +682,9 @@ void main() {
     await tester.idle(); // let nextFrameFuture complete
     await tester.pump();
 
+    expect(mockCodec.disposed, false);
     imageStream.removeListener(ImageStreamListener(listener));
+    expect(mockCodec.disposed, true);
     // The test framework will fail this if there are pending timers at this
     // point.
   });
@@ -699,7 +730,9 @@ void main() {
     expect(mockCodec.numFramesAsked, 3);
     timeDilation = 1.0; // restore time dilation, or it will affect other tests
 
+    expect(mockCodec.disposed, false);
     imageStream.removeListener(listener);
+    expect(mockCodec.disposed, true);
   });
 
   testWidgets('error handlers can intercept errors', (WidgetTester tester) async {
@@ -734,6 +767,7 @@ void main() {
     // No exception is passed up.
     expect(tester.takeException(), isNull);
     expect(capturedException, 'frame completion error');
+    expect(mockCodec.disposed, false);
   });
 
   testWidgets(
@@ -772,6 +806,7 @@ void main() {
       await tester.pump(); // first animation frame shows on first app frame.
 
       await tester.pump(const Duration(milliseconds: 200)); // emit 2nd frame.
+      expect(mockCodec.disposed, false);
     },
   );
 
@@ -918,7 +953,9 @@ void main() {
 
     expect(onImageCount, 1);
 
+    expect(mockCodec.disposed, false);
     handle.dispose();
+    expect(mockCodec.disposed, true);
   });
 
   test('MultiFrameImageStreamCompleter - one frame image should only be decoded once', () async {