Initial implementation of ui.Codec (a wrapper for SkCodec) (flutter/engine#4318)

This is the first step to support animated GIFs: flutter/flutter#204

TBD in following CLs:
 * Implement Codec.getNextFrame.
 * Add Framework side support to run animations.

engine/src/flutter/lib/ui/BUILD.gn

@@ -16,6 +16,8 @@ source_set("ui") {
     "dart_ui.h",
     "painting/canvas.cc",
     "painting/canvas.h",
+    "painting/codec.cc",
+    "painting/codec.h",
     "painting/gradient.cc",
     "painting/gradient.h",
     "painting/image.cc",

engine/src/flutter/lib/ui/dart_ui.cc

@@ -8,6 +8,7 @@
 #include "flutter/lib/ui/compositing/scene_builder.h"
 #include "flutter/lib/ui/dart_runtime_hooks.h"
 #include "flutter/lib/ui/painting/canvas.h"
+#include "flutter/lib/ui/painting/codec.h"
 #include "flutter/lib/ui/painting/gradient.h"
 #include "flutter/lib/ui/painting/image.h"
 #include "flutter/lib/ui/painting/image_decoding.h"
@@ -53,6 +54,7 @@ void DartUI::InitForGlobal() {
     CanvasGradient::RegisterNatives(g_natives);
     CanvasImage::RegisterNatives(g_natives);
     CanvasPath::RegisterNatives(g_natives);
+    Codec::RegisterNatives(g_natives);
     DartRuntimeHooks::RegisterNatives(g_natives);
     ImageDecoding::RegisterNatives(g_natives);
     ImageFilter::RegisterNatives(g_natives);

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

@@ -868,6 +868,45 @@ abstract class Image extends NativeFieldWrapperClass2 {
 /// Callback signature for [decodeImageFromList].
 typedef void ImageDecoderCallback(Image result);
 
+/// Information for a single animation frame.
+///
+/// Obtain a FrameInfo with [Codec.getNextFrame].
+abstract class FrameInfo extends NativeFieldWrapperClass2 {
+  // The duration this frame should be shown.
+  int get durationMillis native "FrameInfo_durationMillis";
+
+  // The Image object for this frame.
+  Image get image native "FrameInfo_image";
+}
+
+/// A handle to an image codec.
+abstract class Codec extends NativeFieldWrapperClass2 {
+  /// Number of frames in this image.
+  int get frameCount native "Codec_frameCount";
+
+  /// Number of times to repeat the animation.
+  ///
+  /// * 0 when the animation should be played once.
+  /// * -1 for infinity repetitions.
+  int get repetitionCount native "Codec_repetitionCount";
+
+  /// Returns the next animation frame.
+  ///
+  /// Wraps back to the first frame after returning the last frame.
+  FrameInfo getNextFrame() native "Codec_getNextFrame";
+
+  /// Release the resources used by this object. The object is no longer usable
+  /// after this method is called.
+  void dispose() native "Codec_dispose";
+}
+
+/// Callback signature for [imageCodecFromList].
+typedef void CodecCallback(Codec result);
+
+/// Instatiates a [Codec] object for an image binary data.
+void instantiateImageCodec(Uint8List list, CodecCallback callback)
+  native "instantiateImageCodec";
+
 /// Convert an image file from a byte array into an [Image] object.
 void decodeImageFromList(Uint8List list, ImageDecoderCallback callback)
     native "decodeImageFromList";

engine/src/flutter/lib/ui/painting/codec.cc

@@ -0,0 +1,136 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/lib/ui/painting/codec.h"
+
+#include "flutter/common/threads.h"
+#include "flutter/glue/trace_event.h"
+#include "lib/fxl/functional/make_copyable.h"
+#include "lib/tonic/dart_binding_macros.h"
+#include "lib/tonic/dart_library_natives.h"
+#include "lib/tonic/dart_state.h"
+#include "lib/tonic/logging/dart_invoke.h"
+#include "lib/tonic/typed_data/uint8_list.h"
+#include "third_party/skia/include/codec/SkCodec.h"
+
+using tonic::DartInvoke;
+using tonic::DartPersistentValue;
+using tonic::ToDart;
+
+namespace blink {
+
+IMPLEMENT_WRAPPERTYPEINFO(ui, Codec);
+
+#define FOR_EACH_BINDING(V) \
+  V(Codec, frameCount)      \
+  V(Codec, repetitionCount) \
+  V(Codec, dispose)
+
+FOR_EACH_BINDING(DART_NATIVE_CALLBACK)
+
+void Codec::dispose() {
+  ClearDartWrapper();
+}
+
+MultiFrameCodec::MultiFrameCodec(std::unique_ptr<SkCodec> codec)
+    : codec_(std::move(codec)) {
+  frameCount_ = codec_->getFrameCount();
+  repetitionCount_ = codec_->getRepetitionCount();
+}
+
+namespace {
+
+static constexpr const char* kInitCodecTraceTag = "InitCodec";
+
+std::unique_ptr<SkCodec> InitCodec(sk_sp<SkData> buffer, size_t trace_id) {
+  TRACE_FLOW_STEP("flutter", kInitCodecTraceTag, trace_id);
+  TRACE_EVENT0("blink", "InitCodec");
+
+  if (buffer == nullptr || buffer->isEmpty()) {
+    return nullptr;
+  }
+
+  return SkCodec::MakeFromData(buffer);
+}
+
+void InvokeCodecCallback(std::unique_ptr<SkCodec> codec,
+                         int frameCount,
+                         int repetitionCount,
+                         std::unique_ptr<DartPersistentValue> callback,
+                         size_t trace_id) {
+  tonic::DartState* dart_state = callback->dart_state().get();
+  if (!dart_state) {
+    TRACE_FLOW_END("flutter", kInitCodecTraceTag, trace_id);
+    return;
+  }
+  tonic::DartState::Scope scope(dart_state);
+  if (!codec) {
+    DartInvoke(callback->value(), {Dart_Null()});
+  } else {
+    fxl::RefPtr<Codec> resultCodec = MultiFrameCodec::Create(std::move(codec));
+    DartInvoke(callback->value(), {ToDart(resultCodec)});
+  }
+  TRACE_FLOW_END("flutter", kInitCodecTraceTag, trace_id);
+}
+
+void InitCodecAndInvokeCodecCallback(
+    std::unique_ptr<DartPersistentValue> callback,
+    sk_sp<SkData> buffer,
+    size_t trace_id) {
+  std::unique_ptr<SkCodec> codec = InitCodec(std::move(buffer), trace_id);
+  int frameCount = codec->getFrameCount();
+  int repetitionCount = codec->getRepetitionCount();
+  Threads::UI()->PostTask(fxl::MakeCopyable([
+    callback = std::move(callback), codec = std::move(codec), trace_id,
+    frameCount, repetitionCount
+  ]() mutable {
+    InvokeCodecCallback(std::move(codec), frameCount, repetitionCount,
+                        std::move(callback), trace_id);
+  }));
+}
+
+void InstantiateImageCodec(Dart_NativeArguments args) {
+  static size_t trace_counter = 1;
+  const size_t trace_id = trace_counter++;
+  TRACE_FLOW_BEGIN("flutter", kInitCodecTraceTag, trace_id);
+
+  Dart_Handle exception = nullptr;
+
+  tonic::Uint8List list =
+      tonic::DartConverter<tonic::Uint8List>::FromArguments(args, 0, exception);
+  if (exception) {
+    TRACE_FLOW_END("flutter", kInitCodecTraceTag, trace_id);
+    Dart_ThrowException(exception);
+    return;
+  }
+
+  Dart_Handle callback_handle = Dart_GetNativeArgument(args, 1);
+  if (!Dart_IsClosure(callback_handle)) {
+    TRACE_FLOW_END("flutter", kInitCodecTraceTag, trace_id);
+    Dart_ThrowException(ToDart("Callback must be a function"));
+    return;
+  }
+
+  auto buffer = SkData::MakeWithCopy(list.data(), list.num_elements());
+
+  Threads::IO()->PostTask(fxl::MakeCopyable([
+    callback = std::make_unique<DartPersistentValue>(
+        tonic::DartState::Current(), callback_handle),
+    buffer = std::move(buffer), trace_id
+  ]() mutable {
+    InitCodecAndInvokeCodecCallback(std::move(callback), std::move(buffer),
+                                    trace_id);
+  }));
+}
+
+}  // namespace
+
+void Codec::RegisterNatives(tonic::DartLibraryNatives* natives) {
+  natives->Register({
+      {"instantiateImageCodec", InstantiateImageCodec, 2, true},
+  });
+  natives->Register({FOR_EACH_BINDING(DART_REGISTER_NATIVE)});
+}
+
+}  // namespace blink

engine/src/flutter/lib/ui/painting/codec.h

@@ -0,0 +1,54 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_LIB_UI_PAINTING_CODEC_H_
+#define FLUTTER_LIB_UI_PAINTING_CODEC_H_
+
+#include "lib/tonic/dart_wrappable.h"
+#include "third_party/skia/include/codec/SkCodec.h"
+
+namespace tonic {
+class DartLibraryNatives;
+}  // namespace tonic
+
+namespace blink {
+
+// A handle to an SkCodec object.
+//
+// Doesn't mirror SkCodec's API but provides a simple sequential access API.
+class Codec : public fxl::RefCountedThreadSafe<Codec>,
+              public tonic::DartWrappable {
+  DEFINE_WRAPPERTYPEINFO();
+
+ public:
+  virtual int frameCount() = 0;
+  virtual int repetitionCount() = 0;
+  void dispose();
+
+  static void RegisterNatives(tonic::DartLibraryNatives* natives);
+};
+
+class MultiFrameCodec : public Codec {
+  FRIEND_MAKE_REF_COUNTED(MultiFrameCodec);
+
+ public:
+  static fxl::RefPtr<MultiFrameCodec> Create(std::unique_ptr<SkCodec> codec) {
+    return fxl::MakeRefCounted<MultiFrameCodec>(std::move(codec));
+  }
+
+  int frameCount() { return frameCount_; }
+  int repetitionCount() { return repetitionCount_; }
+
+  static void RegisterNatives(tonic::DartLibraryNatives* natives);
+
+ private:
+  MultiFrameCodec(std::unique_ptr<SkCodec> codec);
+
+  const std::unique_ptr<SkCodec> codec_;
+  int frameCount_;
+  int repetitionCount_;
+};
+}  // namespace blink
+
+#endif  // FLUTTER_LIB_UI_PAINTING_CODEC_H_

engine/src/flutter/testing/dart/codec_test.dart

@@ -0,0 +1,43 @@
+// Copyright 2017 The Chromium 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 'dart:async';
+import 'dart:io';
+import 'dart:ui' as ui;
+import 'dart:typed_data';
+
+import 'package:test/test.dart';
+import 'package:path/path.dart' as path;
+
+void main() {
+
+  test('Animation metadata', () async {
+    Uint8List data = await _getSkiaResource('alphabetAnim.gif').readAsBytes();
+    Completer<ui.Codec> completer = new Completer<ui.Codec>();
+    ui.instantiateImageCodec(data, completer.complete);
+    ui.Codec codec = await completer.future;
+    expect(codec.frameCount, 13);
+    expect(codec.repetitionCount, 0);
+    codec.dispose();
+
+    data = await _getSkiaResource('test640x479.gif').readAsBytes();
+    completer = new Completer<ui.Codec>();
+    ui.instantiateImageCodec(data, completer.complete);
+    codec = await completer.future;
+    expect(codec.frameCount, 4);
+    expect(codec.repetitionCount, -1);
+  });
+}
+
+/// Returns a File handle to a file in the skia/resources directory.
+File _getSkiaResource(String fileName) {
+  // As Platform.script is not working for flutter_tester
+  // (https://github.com/flutter/flutter/issues/12847), this is currently
+  // assuming the curent working directory is engine/src.
+  // This is fragile and should be changed once the Platform.script issue is
+  // resolved.
+  String assetPath =
+    path.join('third_party', 'skia', 'resources', fileName);
+  return new File(assetPath);
+}