Ensure that Scene::toImage renders texture backed images.

ci/licenses_golden/licenses_flutter

@@ -507,6 +507,7 @@ FILE: ../../../flutter/lib/ui/isolate_name_server/isolate_name_server_natives.cc
 FILE: ../../../flutter/lib/ui/isolate_name_server/isolate_name_server_natives.h
 FILE: ../../../flutter/lib/ui/plugins/callback_cache.cc
 FILE: ../../../flutter/lib/ui/plugins/callback_cache.h
+FILE: ../../../flutter/lib/ui/snapshot_delegate.h
 FILE: ../../../flutter/runtime/dart_service_isolate_unittests.cc
 FILE: ../../../flutter/shell/common/isolate_configuration.cc
 FILE: ../../../flutter/shell/common/isolate_configuration.h

lib/ui/BUILD.gn

@@ -23,8 +23,8 @@ source_set("ui") {
     "painting/canvas.h",
     "painting/codec.cc",
     "painting/codec.h",
-    "painting/engine_layer.h",
     "painting/engine_layer.cc",
+    "painting/engine_layer.h",
     "painting/frame_info.cc",
     "painting/frame_info.h",
     "painting/gradient.cc",
@@ -65,6 +65,7 @@ source_set("ui") {
     "semantics/semantics_update.h",
     "semantics/semantics_update_builder.cc",
     "semantics/semantics_update_builder.h",
+    "snapshot_delegate.h",
     "text/asset_manager_font_provider.cc",
     "text/asset_manager_font_provider.h",
     "text/font_collection.cc",

lib/ui/compositing/scene.cc

@@ -53,46 +53,6 @@ void Scene::dispose() {
   ClearDartWrapper();
 }
 
-static sk_sp<SkImage> CreateSceneSnapshot(GrContext* context,
-                                          sk_sp<SkPicture> picture,
-                                          const SkSize& size) {
-  TRACE_EVENT0("flutter", "CreateSceneSnapshot");
-  auto image_info =
-      SkImageInfo::MakeN32Premul(SkISize::Make(size.width(), size.height()));
-
-  sk_sp<SkSurface> surface;
-
-  if (context) {
-    surface = SkSurface::MakeRenderTarget(context, SkBudgeted::kNo, image_info);
-  }
-
-  if (!surface) {
-    surface = SkSurface::MakeRaster(image_info);
-  }
-
-  if (!surface) {
-    return nullptr;
-  }
-
-  auto canvas = surface->getCanvas();
-
-  if (!canvas) {
-    return nullptr;
-  }
-
-  if (picture) {
-    canvas->drawPicture(picture.get());
-  }
-
-  auto snapshot = surface->makeImageSnapshot();
-
-  if (!snapshot) {
-    return nullptr;
-  }
-
-  return snapshot->makeRasterImage();
-}
-
 Dart_Handle Scene::toImage(uint32_t width,
                            uint32_t height,
                            Dart_Handle raw_image_callback) {
@@ -110,67 +70,70 @@ Dart_Handle Scene::toImage(uint32_t width,
   }
 
   auto dart_state = UIDartState::Current();
-
   auto image_callback = std::make_unique<tonic::DartPersistentValue>(
       dart_state, raw_image_callback);
+  auto unref_queue = dart_state->GetSkiaUnrefQueue();
+  auto ui_task_runner = dart_state->GetTaskRunners().GetUITaskRunner();
+  auto gpu_task_runner = dart_state->GetTaskRunners().GetGPUTaskRunner();
+  auto snapshot_delegate = dart_state->GetSnapshotDelegate();
 
   // We can't create an image on this task runner because we don't have a
   // graphics context. Even if we did, it would be slow anyway. Also, this
   // thread owns the sole reference to the layer tree. So we flatten the layer
   // tree into a picture and use that as the thread transport mechanism.
 
-  auto bounds_size = SkSize::Make(width, height);
-  auto picture = m_layerTree->Flatten(SkRect::MakeSize(bounds_size));
+  auto picture_bounds = SkISize::Make(width, height);
+  auto picture = m_layerTree->Flatten(SkRect::MakeWH(width, height));
+
   if (!picture) {
     // Already in Dart scope.
     return tonic::ToDart("Could not flatten scene into a layer tree.");
   }
 
-  auto resource_context = dart_state->GetResourceContext();
-  auto ui_task_runner = dart_state->GetTaskRunners().GetUITaskRunner();
-  auto unref_queue = dart_state->GetSkiaUnrefQueue();
-
-  // The picture has been prepared on the UI thread.
-  dart_state->GetTaskRunners().GetIOTaskRunner()->PostTask(
-      fml::MakeCopyable([picture = std::move(picture),                    //
-                         bounds_size,                                     //
-                         resource_context = std::move(resource_context),  //
-                         ui_task_runner = std::move(ui_task_runner),      //
-                         image_callback = std::move(image_callback),      //
-                         unref_queue = std::move(unref_queue)             //
-  ]() mutable {
-        // Snapshot the picture on the IO thread that contains an optional
-        // GrContext.
-        auto image = CreateSceneSnapshot(resource_context.get(),
-                                         std::move(picture), bounds_size);
-
-        // Send the image back to the UI thread for submission back to the
-        // framework.
-        ui_task_runner->PostTask(
-            fml::MakeCopyable([image = std::move(image),                    //
-                               image_callback = std::move(image_callback),  //
-                               unref_queue = std::move(unref_queue)         //
-        ]() mutable {
-              auto dart_state = image_callback->dart_state().lock();
-              if (!dart_state) {
-                // The root isolate could have died in the meantime.
-                return;
-              }
-              tonic::DartState::Scope scope(dart_state);
-
-              if (!image) {
-                tonic::DartInvoke(image_callback->Get(), {Dart_Null()});
-                return;
-              }
-
-              auto dart_image = CanvasImage::Create();
-              dart_image->set_image({std::move(image), std::move(unref_queue)});
-              auto raw_dart_image = tonic::ToDart(std::move(dart_image));
-
-              // All done!
-              tonic::DartInvoke(image_callback->Get(), {raw_dart_image});
-            }));
-      }));
+  auto ui_task = fml::MakeCopyable([ui_task_runner,
+                                    image_callback = std::move(image_callback),
+                                    unref_queue](
+                                       sk_sp<SkImage> raster_image) mutable {
+    // Send the raster image back to the UI thread for submission to the
+    // framework.
+    ui_task_runner->PostTask(fml::MakeCopyable([raster_image,
+                                                image_callback =
+                                                    std::move(image_callback),
+                                                unref_queue]() mutable {
+      auto dart_state = image_callback->dart_state().lock();
+      if (!dart_state) {
+        // The root isolate could have died in the meantime.
+        return;
+      }
+      tonic::DartState::Scope scope(dart_state);
+
+      if (!raster_image) {
+        tonic::DartInvoke(image_callback->Get(), {Dart_Null()});
+        return;
+      }
+
+      auto dart_image = CanvasImage::Create();
+      dart_image->set_image({std::move(raster_image), std::move(unref_queue)});
+      auto raw_dart_image = tonic::ToDart(std::move(dart_image));
+
+      // All done!
+      tonic::DartInvoke(image_callback->Get(), {raw_dart_image});
+    }));
+  });
+
+  auto gpu_task = fml::MakeCopyable([gpu_task_runner, picture, picture_bounds,
+                                     snapshot_delegate, ui_task]() {
+    gpu_task_runner->PostTask([snapshot_delegate, picture, picture_bounds,
+                               ui_task]() {
+      // Snapshot the picture on the GPU thread. This thread has access to the
+      // GPU contexts that may contain the sole references to a texture backed
+      // images in the picture.
+      ui_task(snapshot_delegate->MakeRasterSnapshot(picture, picture_bounds));
+    });
+  });
+
+  // Kick things off on the GPU.
+  gpu_task();
 
   return Dart_Null();
 }

lib/ui/snapshot_delegate.h

@@ -0,0 +1,21 @@
+// Copyright 2018 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.
+
+#ifndef FLUTTER_LIB_UI_SNAPSHOT_DELEGATE_H_
+#define FLUTTER_LIB_UI_SNAPSHOT_DELEGATE_H_
+
+#include "third_party/skia/include/core/SkImage.h"
+#include "third_party/skia/include/core/SkPicture.h"
+
+namespace blink {
+
+class SnapshotDelegate {
+ public:
+  virtual sk_sp<SkImage> MakeRasterSnapshot(sk_sp<SkPicture> picture,
+                                            SkISize picture_size) = 0;
+};
+
+}  // namespace blink
+
+#endif  // FLUTTER_LIB_UI_SNAPSHOT_DELEGATE_H_

lib/ui/ui_dart_state.cc

@@ -16,6 +16,7 @@ namespace blink {
 UIDartState::UIDartState(TaskRunners task_runners,
                          TaskObserverAdd add_callback,
                          TaskObserverRemove remove_callback,
+                         fml::WeakPtr<SnapshotDelegate> snapshot_delegate,
                          fml::WeakPtr<GrContext> resource_context,
                          fml::RefPtr<flow::SkiaUnrefQueue> skia_unref_queue,
                          std::string advisory_script_uri,
@@ -25,6 +26,7 @@ UIDartState::UIDartState(TaskRunners task_runners,
     : task_runners_(std::move(task_runners)),
       add_callback_(std::move(add_callback)),
       remove_callback_(std::move(remove_callback)),
+      snapshot_delegate_(std::move(snapshot_delegate)),
       resource_context_(std::move(resource_context)),
       advisory_script_uri_(std::move(advisory_script_uri)),
       advisory_script_entrypoint_(std::move(advisory_script_entrypoint)),
@@ -99,6 +101,10 @@ void UIDartState::AddOrRemoveTaskObserver(bool add) {
   }
 }
 
+fml::WeakPtr<SnapshotDelegate> UIDartState::GetSnapshotDelegate() const {
+  return snapshot_delegate_;
+}
+
 fml::WeakPtr<GrContext> UIDartState::GetResourceContext() const {
   return resource_context_;
 }

lib/ui/ui_dart_state.h

@@ -15,6 +15,7 @@
 #include "flutter/fml/build_config.h"
 #include "flutter/fml/memory/weak_ptr.h"
 #include "flutter/lib/ui/isolate_name_server/isolate_name_server.h"
+#include "flutter/lib/ui/snapshot_delegate.h"
 #include "third_party/dart/runtime/include/dart_api.h"
 #include "third_party/skia/include/gpu/GrContext.h"
 #include "third_party/tonic/dart_microtask_queue.h"
@@ -47,6 +48,8 @@ class UIDartState : public tonic::DartState {
 
   fml::RefPtr<flow::SkiaUnrefQueue> GetSkiaUnrefQueue() const;
 
+  fml::WeakPtr<SnapshotDelegate> GetSnapshotDelegate() const;
+
   fml::WeakPtr<GrContext> GetResourceContext() const;
 
   IsolateNameServer* GetIsolateNameServer();
@@ -68,6 +71,7 @@ class UIDartState : public tonic::DartState {
   UIDartState(TaskRunners task_runners,
               TaskObserverAdd add_callback,
               TaskObserverRemove remove_callback,
+              fml::WeakPtr<SnapshotDelegate> snapshot_delegate,
               fml::WeakPtr<GrContext> resource_context,
               fml::RefPtr<flow::SkiaUnrefQueue> skia_unref_queue,
               std::string advisory_script_uri,
@@ -89,6 +93,7 @@ class UIDartState : public tonic::DartState {
   const TaskRunners task_runners_;
   const TaskObserverAdd add_callback_;
   const TaskObserverRemove remove_callback_;
+  fml::WeakPtr<SnapshotDelegate> snapshot_delegate_;
   fml::WeakPtr<GrContext> resource_context_;
   const std::string advisory_script_uri_;
   const std::string advisory_script_entrypoint_;

runtime/dart_isolate.cc

@@ -38,6 +38,7 @@ std::weak_ptr<DartIsolate> DartIsolate::CreateRootIsolate(
     fml::RefPtr<DartSnapshot> shared_snapshot,
     TaskRunners task_runners,
     std::unique_ptr<Window> window,
+    fml::WeakPtr<SnapshotDelegate> snapshot_delegate,
     fml::WeakPtr<GrContext> resource_context,
     fml::RefPtr<flow::SkiaUnrefQueue> unref_queue,
     std::string advisory_script_uri,
@@ -54,14 +55,15 @@ std::weak_ptr<DartIsolate> DartIsolate::CreateRootIsolate(
   // isolate lifecycle is entirely managed by the VM).
   auto root_embedder_data = std::make_unique<std::shared_ptr<DartIsolate>>(
       std::make_shared<DartIsolate>(
-          vm,                           // VM
-          std::move(isolate_snapshot),  // isolate snapshot
-          std::move(shared_snapshot),   // shared snapshot
-          task_runners,                 // task runners
-          std::move(resource_context),  // resource context
-          std::move(unref_queue),       // skia unref queue
-          advisory_script_uri,          // advisory URI
-          advisory_script_entrypoint,   // advisory entrypoint
+          vm,                            // VM
+          std::move(isolate_snapshot),   // isolate snapshot
+          std::move(shared_snapshot),    // shared snapshot
+          task_runners,                  // task runners
+          std::move(snapshot_delegate),  // snapshot delegate
+          std::move(resource_context),   // resource context
+          std::move(unref_queue),        // skia unref queue
+          advisory_script_uri,           // advisory URI
+          advisory_script_entrypoint,    // advisory entrypoint
           nullptr  // child isolate preparer will be set when this isolate is
                    // prepared to run
           ));
@@ -101,6 +103,7 @@ DartIsolate::DartIsolate(DartVM* vm,
                          fml::RefPtr<DartSnapshot> isolate_snapshot,
                          fml::RefPtr<DartSnapshot> shared_snapshot,
                          TaskRunners task_runners,
+                         fml::WeakPtr<SnapshotDelegate> snapshot_delegate,
                          fml::WeakPtr<GrContext> resource_context,
                          fml::RefPtr<flow::SkiaUnrefQueue> unref_queue,
                          std::string advisory_script_uri,
@@ -109,6 +112,7 @@ DartIsolate::DartIsolate(DartVM* vm,
     : UIDartState(std::move(task_runners),
                   vm->GetSettings().task_observer_add,
                   vm->GetSettings().task_observer_remove,
+                  std::move(snapshot_delegate),
                   std::move(resource_context),
                   std::move(unref_queue),
                   advisory_script_uri,
@@ -520,6 +524,7 @@ Dart_Isolate DartIsolate::DartCreateAndStartServiceIsolate(
           vm->GetSharedSnapshot(),   // shared snapshot
           null_task_runners,         // task runners
           nullptr,                   // window
+          {},                        // snapshot delegate
           {},                        // resource context
           {},                        // unref queue
           advisory_script_uri == nullptr ? ""
@@ -630,6 +635,7 @@ DartIsolate::CreateDartVMAndEmbedderObjectPair(
             (*raw_embedder_isolate)->GetIsolateSnapshot(),  // isolate_snapshot
             (*raw_embedder_isolate)->GetSharedSnapshot(),   // shared_snapshot
             null_task_runners,                              // task_runners
+            fml::WeakPtr<SnapshotDelegate>{},               // snapshot_delegate
             fml::WeakPtr<GrContext>{},                      // resource_context
             nullptr,                                        // unref_queue
             advisory_script_uri,         // advisory_script_uri

runtime/dart_isolate.h

@@ -12,6 +12,7 @@
 #include "flutter/fml/compiler_specific.h"
 #include "flutter/fml/macros.h"
 #include "flutter/fml/mapping.h"
+#include "flutter/lib/ui/snapshot_delegate.h"
 #include "flutter/lib/ui/ui_dart_state.h"
 #include "flutter/lib/ui/window/window.h"
 #include "flutter/runtime/dart_snapshot.h"
@@ -44,6 +45,7 @@ class DartIsolate : public UIDartState {
       fml::RefPtr<DartSnapshot> shared_snapshot,
       TaskRunners task_runners,
       std::unique_ptr<Window> window,
+      fml::WeakPtr<SnapshotDelegate> snapshot_delegate,
       fml::WeakPtr<GrContext> resource_context,
       fml::RefPtr<flow::SkiaUnrefQueue> unref_queue,
       std::string advisory_script_uri,
@@ -54,6 +56,7 @@ class DartIsolate : public UIDartState {
               fml::RefPtr<DartSnapshot> isolate_snapshot,
               fml::RefPtr<DartSnapshot> shared_snapshot,
               TaskRunners task_runners,
+              fml::WeakPtr<SnapshotDelegate> snapshot_delegate,
               fml::WeakPtr<GrContext> resource_context,
               fml::RefPtr<flow::SkiaUnrefQueue> unref_queue,
               std::string advisory_script_uri,

runtime/dart_isolate_unittests.cc

@@ -35,6 +35,7 @@ TEST_F(DartIsolateTest, RootIsolateCreationAndShutdown) {
       vm->GetSharedSnapshot(),   // shared snapshot
       std::move(task_runners),   // task runners
       nullptr,                   // window
+      {},                        // snapshot delegate
       {},                        // resource context
       nullptr,                   // unref qeueue
       "main.dart",               // advisory uri
@@ -64,6 +65,7 @@ TEST_F(DartIsolateTest, IsolateShutdownCallbackIsInIsolateScope) {
       vm->GetSharedSnapshot(),   // shared snapshot
       std::move(task_runners),   // task runners
       nullptr,                   // window
+      {},                        // snapshot delegate
       {},                        // resource context
       nullptr,                   // unref qeueue
       "main.dart",               // advisory uri