Better handle image codec instantiation failure (flutter#22809)

Author: yjbanov

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

@@ -44,7 +44,7 @@ class CanvasKit {
   external SkTextDirectionEnum get TextDirection;
   external SkFontWeightEnum get FontWeight;
   external SkFontSlantEnum get FontSlant;
-  external SkAnimatedImage MakeAnimatedImageFromEncoded(Uint8List imageData);
+  external SkAnimatedImage? MakeAnimatedImageFromEncoded(Uint8List imageData);
   external SkShaderNamespace get Shader;
   external SkMaskFilterNamespace get MaskFilter;
   external SkColorFilterNamespace get ColorFilter;

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

@@ -6,10 +6,9 @@
 part of engine;
 
 /// Instantiates a [ui.Codec] backed by an `SkAnimatedImage` from Skia.
-void skiaInstantiateImageCodec(Uint8List list, Callback<ui.Codec> callback,
+ui.Codec skiaInstantiateImageCodec(Uint8List list,
     [int? width, int? height, int? format, int? rowBytes]) {
-  final CkAnimatedImage codec = CkAnimatedImage.decodeFromBytes(list);
-  callback(codec);
+  return CkAnimatedImage.decodeFromBytes(list);
 }
 
 /// Instantiates a [ui.Codec] backed by an `SkAnimatedImage` from Skia after
@@ -49,7 +48,11 @@ class CkAnimatedImage extends ManagedSkiaObject<SkAnimatedImage> implements ui.C
 
   @override
   SkAnimatedImage createDefault() {
-    return canvasKit.MakeAnimatedImageFromEncoded(_bytes);
+    final SkAnimatedImage? animatedImage = canvasKit.MakeAnimatedImageFromEncoded(_bytes);
+    if (animatedImage == null) {
+      throw Exception('Failed to decode image');
+    }
+    return animatedImage;
   }
 
   @override

lib/web_ui/lib/src/ui/painting.dart

@@ -452,20 +452,14 @@ Future<Codec> instantiateImageCodec(
   int? targetWidth,
   int? targetHeight,
   bool allowUpscaling = true,
-}) {
-  return _futurize<Codec>((engine.Callback<Codec> callback) =>
-      // TODO: Implement targetWidth and targetHeight support.
-      _instantiateImageCodec(list, callback));
-}
-
-String? _instantiateImageCodec(Uint8List list, engine.Callback<Codec> callback) {
+}) async {
   if (engine.useCanvasKit) {
-    engine.skiaInstantiateImageCodec(list, callback);
-    return null;
+    // TODO: Implement targetWidth and targetHeight support.
+    return engine.skiaInstantiateImageCodec(list);
+  } else {
+    final html.Blob blob = html.Blob(<dynamic>[list.buffer]);
+    return engine.HtmlBlobCodec(blob);
   }
-  final html.Blob blob = html.Blob(<dynamic>[list.buffer]);
-  callback(engine.HtmlBlobCodec(blob));
-  return null;
 }
 
 Future<Codec> webOnlyInstantiateImageCodecFromUrl(Uri uri,
@@ -565,12 +559,9 @@ Future<Codec> _createBmp(
     }
   }
 
-  final Completer<Codec> codecCompleter = Completer<Codec>();
-  _instantiateImageCodec(
+  return instantiateImageCodec(
     bmpData.buffer.asUint8List(),
-    (Codec codec) => codecCompleter.complete(codec),
   );
-  return codecCompleter.future;
 }
 
 void decodeImageFromPixels(
@@ -587,16 +578,13 @@ void decodeImageFromPixels(
   if (engine.useCanvasKit) {
     engine.skiaInstantiateImageCodec(
       pixels,
-      (Codec codec) {
-        codec.getNextFrame().then((FrameInfo info) {
-          callback(info.image);
-        });
-      },
       width,
       height,
       format.index,
       rowBytes,
-    );
+    ).getNextFrame().then((FrameInfo info) {
+      callback(info.image);
+    });
     return;
   }
 

lib/web_ui/test/canvaskit/image_test.dart

@@ -4,6 +4,7 @@
 
 // @dart = 2.6
 import 'dart:html' show ProgressEvent;
+import 'dart:typed_data';
 
 import 'package:test/bootstrap/browser.dart';
 import 'package:test/test.dart';
@@ -114,6 +115,15 @@ void testMain() {
       expect((await image.toByteData(format: ui.ImageByteFormat.png)).lengthInBytes, greaterThan(0));
       testCollector.collectNow();
     });
+
+    test('Reports error when failing to decode image', () async {
+      try {
+        await ui.instantiateImageCodec(Uint8List(0));
+        fail('Expected to throw');
+      } on Exception catch (exception) {
+        expect(exception.toString(), 'Exception: Failed to decode image');
+      }
+    });
     // TODO: https://github.com/flutter/flutter/issues/60040
   }, skip: isIosSafari);
 }