shell/common/rasterizer.cc - external/github.com/flutter/engine - Git at Google

 // Copyright 2013 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.

 #include "flutter/shell/common/rasterizer.h"

 #include "flutter/shell/common/persistent_cache.h"

 #include <utility>

 #include "flutter/fml/time/time_delta.h"
 #include "flutter/fml/time/time_point.h"
 #include "third_party/skia/include/core/SkEncodedImageFormat.h"
 #include "third_party/skia/include/core/SkImageEncoder.h"
 #include "third_party/skia/include/core/SkPictureRecorder.h"
 #include "third_party/skia/include/core/SkSerialProcs.h"
 #include "third_party/skia/include/core/SkSurface.h"
 #include "third_party/skia/include/core/SkSurfaceCharacterization.h"
 #include "third_party/skia/include/utils/SkBase64.h"

 namespace flutter {

 // The rasterizer will tell Skia to purge cached resources that have not been
 // used within this interval.
 static constexpr std::chrono::milliseconds kSkiaCleanupExpiration(15000);

 // TODO(dnfield): Remove this once internal embedders have caught up.
 static Rasterizer::DummyDelegate dummy_delegate_;
 Rasterizer::Rasterizer(
     TaskRunners task_runners,
     std::unique_ptr<flutter::CompositorContext> compositor_context)
     : Rasterizer(dummy_delegate_,
                  std::move(task_runners),
                  std::move(compositor_context)) {}

 Rasterizer::Rasterizer(Delegate& delegate, TaskRunners task_runners)
     : Rasterizer(delegate,
                  std::move(task_runners),
                  std::make_unique<flutter::CompositorContext>(
                      delegate.GetFrameBudget())) {}

 Rasterizer::Rasterizer(
     Delegate& delegate,
     TaskRunners task_runners,
     std::unique_ptr<flutter::CompositorContext> compositor_context)
     : delegate_(delegate),
       task_runners_(std::move(task_runners)),
       compositor_context_(std::move(compositor_context)),
       user_override_resource_cache_bytes_(false),
       weak_factory_(this) {
   FML_DCHECK(compositor_context_);
 }

 Rasterizer::~Rasterizer() = default;

 fml::TaskRunnerAffineWeakPtr<Rasterizer> Rasterizer::GetWeakPtr() const {
   return weak_factory_.GetTaskRunnerAffineWeakPtr();
 }

 fml::WeakPtr<SnapshotDelegate> Rasterizer::GetSnapshotDelegate() const {
   return weak_factory_.GetWeakPtr();
 }

 void Rasterizer::Setup(std::unique_ptr<Surface> surface) {
   surface_ = std::move(surface);
   if (max_cache_bytes_.has_value()) {
     SetResourceCacheMaxBytes(max_cache_bytes_.value(),
                              user_override_resource_cache_bytes_);
   }
   compositor_context_->OnGrContextCreated();
   if (surface_->GetExternalViewEmbedder()) {
     const auto platform_id =
         task_runners_.GetPlatformTaskRunner()->GetTaskQueueId();
     const auto gpu_id = task_runners_.GetRasterTaskRunner()->GetTaskQueueId();
     raster_thread_merger_ =
         fml::MakeRefCounted<fml::RasterThreadMerger>(platform_id, gpu_id);
   }
 }

 void Rasterizer::Teardown() {
   compositor_context_->OnGrContextDestroyed();
   surface_.reset();
   last_layer_tree_.reset();
 }

 void Rasterizer::NotifyLowMemoryWarning() const {
   if (!surface_) {
     FML_DLOG(INFO) << "Rasterizer::PurgeCaches called with no surface.";
     return;
   }
   auto context = surface_->GetContext();
   if (!context) {
     FML_DLOG(INFO) << "Rasterizer::PurgeCaches called with no GrContext.";
     return;
   }
   context->freeGpuResources();
 }

 flutter::TextureRegistry* Rasterizer::GetTextureRegistry() {
   return &compositor_context_->texture_registry();
 }

 flutter::LayerTree* Rasterizer::GetLastLayerTree() {
   return last_layer_tree_.get();
 }

 void Rasterizer::DrawLastLayerTree() {
   if (!last_layer_tree_ || !surface_) {
     return;
   }
   DrawToSurface(*last_layer_tree_);
 }

 void Rasterizer::Draw(fml::RefPtr<Pipeline<flutter::LayerTree>> pipeline) {
   TRACE_EVENT0("flutter", "GPURasterizer::Draw");
   if (raster_thread_merger_ &&
       !raster_thread_merger_->IsOnRasterizingThread()) {
     // we yield and let this frame be serviced on the right thread.
     return;
   }
   FML_DCHECK(task_runners_.GetRasterTaskRunner()->RunsTasksOnCurrentThread());

   RasterStatus raster_status = RasterStatus::kFailed;
   Pipeline<flutter::LayerTree>::Consumer consumer =
       [&](std::unique_ptr<LayerTree> layer_tree) {
         raster_status = DoDraw(std::move(layer_tree));
       };

   PipelineConsumeResult consume_result = pipeline->Consume(consumer);
   // if the raster status is to resubmit the frame, we push the frame to the
   // front of the queue and also change the consume status to more available.
   if (raster_status == RasterStatus::kResubmit) {
     auto front_continuation = pipeline->ProduceIfEmpty();
     bool result =
         front_continuation.Complete(std::move(resubmitted_layer_tree_));
     if (result) {
       consume_result = PipelineConsumeResult::MoreAvailable;
     }
   } else if (raster_status == RasterStatus::kEnqueuePipeline) {
     consume_result = PipelineConsumeResult::MoreAvailable;
   }

   // Merging the thread as we know the next `Draw` should be run on the platform
   // thread.
   if (raster_status == RasterStatus::kResubmit) {
     auto* external_view_embedder = surface_->GetExternalViewEmbedder();
     // We know only the `external_view_embedder` can
     // causes|RasterStatus::kResubmit|. Check to make sure.
     FML_DCHECK(external_view_embedder != nullptr);
     external_view_embedder->EndFrame(raster_thread_merger_);
   }

   // Consume as many pipeline items as possible. But yield the event loop
   // between successive tries.
   switch (consume_result) {
     case PipelineConsumeResult::MoreAvailable: {
       task_runners_.GetRasterTaskRunner()->PostTask(
           [weak_this = weak_factory_.GetTaskRunnerAffineWeakPtr(), pipeline]() {
             if (weak_this) {
               weak_this->Draw(pipeline);
             }
           });
       break;
     }
     default:
       break;
   }
 }

 sk_sp<SkImage> Rasterizer::DoMakeRasterSnapshot(
     SkISize size,
     std::function<void(SkCanvas*)> draw_callback) {
   TRACE_EVENT0("flutter", __FUNCTION__);

   sk_sp<SkSurface> surface;
   SkImageInfo image_info = SkImageInfo::MakeN32Premul(
       size.width(), size.height(), SkColorSpace::MakeSRGB());
   if (surface_ == nullptr || surface_->GetContext() == nullptr) {
     // Raster surface is fine if there is no on screen surface. This might
     // happen in case of software rendering.
     surface = SkSurface::MakeRaster(image_info);
   } else {
     if (!surface_->MakeRenderContextCurrent()) {
       return nullptr;
     }

     // When there is an on screen surface, we need a render target SkSurface
     // because we want to access texture backed images.
     surface = SkSurface::MakeRenderTarget(surface_->GetContext(),  // context
                                           SkBudgeted::kNo,         // budgeted
                                           image_info               // image info
     );
   }

   if (surface == nullptr || surface->getCanvas() == nullptr) {
     return nullptr;
   }

   draw_callback(surface->getCanvas());
   surface->getCanvas()->flush();

   sk_sp<SkImage> device_snapshot;
   {
     TRACE_EVENT0("flutter", "MakeDeviceSnpashot");
     device_snapshot = surface->makeImageSnapshot();
   }

   if (device_snapshot == nullptr) {
     return nullptr;
   }

   {
     TRACE_EVENT0("flutter", "DeviceHostTransfer");
     if (auto raster_image = device_snapshot->makeRasterImage()) {
       return raster_image;
     }
   }

   return nullptr;
 }

 sk_sp<SkImage> Rasterizer::MakeRasterSnapshot(sk_sp<SkPicture> picture,
                                               SkISize picture_size) {
   return DoMakeRasterSnapshot(picture_size,
                               [picture = std::move(picture)](SkCanvas* canvas) {
                                 canvas->drawPicture(picture);
                               });
 }

 sk_sp<SkImage> Rasterizer::ConvertToRasterImage(sk_sp<SkImage> image) {
   TRACE_EVENT0("flutter", __FUNCTION__);

   // If the rasterizer does not have a surface with a GrContext, then it will
   // be unable to render a cross-context SkImage.  The caller will need to
   // create the raster image on the IO thread.
   if (surface_ == nullptr || surface_->GetContext() == nullptr) {
     return nullptr;
   }

   if (image == nullptr) {
     return nullptr;
   }

   return DoMakeRasterSnapshot(image->dimensions(),
                               [image = std::move(image)](SkCanvas* canvas) {
                                 canvas->drawImage(image, 0, 0);
                               });
 }

 RasterStatus Rasterizer::DoDraw(
     std::unique_ptr<flutter::LayerTree> layer_tree) {
   FML_DCHECK(task_runners_.GetRasterTaskRunner()->RunsTasksOnCurrentThread());

   if (!layer_tree || !surface_) {
     return RasterStatus::kFailed;
   }

   FrameTiming timing;
   const fml::TimePoint frame_target_time = layer_tree->target_time();
   timing.Set(FrameTiming::kBuildStart, layer_tree->build_start());
   timing.Set(FrameTiming::kBuildFinish, layer_tree->build_finish());
   timing.Set(FrameTiming::kRasterStart, fml::TimePoint::Now());

   PersistentCache* persistent_cache = PersistentCache::GetCacheForProcess();
   persistent_cache->ResetStoredNewShaders();

   RasterStatus raster_status = DrawToSurface(*layer_tree);
   if (raster_status == RasterStatus::kSuccess) {
     last_layer_tree_ = std::move(layer_tree);
   } else if (raster_status == RasterStatus::kResubmit) {
     resubmitted_layer_tree_ = std::move(layer_tree);
     return raster_status;
   }

   if (persistent_cache->IsDumpingSkp() &&
       persistent_cache->StoredNewShaders()) {
     auto screenshot =
         ScreenshotLastLayerTree(ScreenshotType::SkiaPicture, false);
     persistent_cache->DumpSkp(*screenshot.data);
   }

   // TODO(liyuqian): in Fuchsia, the rasterization doesn't finish when
   // Rasterizer::DoDraw finishes. Future work is needed to adapt the timestamp
   // for Fuchsia to capture SceneUpdateContext::ExecutePaintTasks.
   const auto raster_finish_time = fml::TimePoint::Now();
   timing.Set(FrameTiming::kRasterFinish, raster_finish_time);
   delegate_.OnFrameRasterized(timing);

   if (raster_finish_time > frame_target_time) {
     fml::TimePoint latest_frame_target_time =
         delegate_.GetLatestFrameTargetTime();
     const auto frame_budget_millis = delegate_.GetFrameBudget().count();
     if (latest_frame_target_time < raster_finish_time) {
       latest_frame_target_time =
           latest_frame_target_time +
           fml::TimeDelta::FromMillisecondsF(frame_budget_millis);
     }
     const auto frame_lag =
         (latest_frame_target_time - frame_target_time).ToMillisecondsF();
     const int vsync_transitions_missed = round(frame_lag / frame_budget_millis);
     fml::tracing::TraceEventAsyncComplete(
         "flutter",                    // category
         "SceneDisplayLag",            // name
         raster_finish_time,           // begin_time
         latest_frame_target_time,     // end_time
         "frame_target_time",          // arg_key_1
         frame_target_time,            // arg_val_1
         "current_frame_target_time",  // arg_key_2
         latest_frame_target_time,     // arg_val_2
         "vsync_transitions_missed",   // arg_key_3
         vsync_transitions_missed      // arg_val_3
     );
   }

   // Pipeline pressure is applied from a couple of places:
   // rasterizer: When there are more items as of the time of Consume.
   // animator (via shell): Frame gets produces every vsync.
   // Enqueing here is to account for the following scenario:
   // T = 1
   //  - one item (A) in the pipeline
   //  - rasterizer starts (and merges the threads)
   //  - pipeline consume result says no items to process
   // T = 2
   //  - animator produces (B) to the pipeline
   //  - applies pipeline pressure via platform thread.
   // T = 3
   //   - rasterizes finished (and un-merges the threads)
   //   - |Draw| for B yields as its on the wrong thread.
   // This enqueue ensures that we attempt to consume from the right
   // thread one more time after un-merge.
   if (raster_thread_merger_) {
     if (raster_thread_merger_->DecrementLease() ==
         fml::RasterThreadStatus::kUnmergedNow) {
       return RasterStatus::kEnqueuePipeline;
     }
   }

   return raster_status;
 }

 RasterStatus Rasterizer::DrawToSurface(flutter::LayerTree& layer_tree) {
   TRACE_EVENT0("flutter", "Rasterizer::DrawToSurface");
   FML_DCHECK(surface_);

   auto frame = surface_->AcquireFrame(layer_tree.frame_size());

   if (frame == nullptr) {
     return RasterStatus::kFailed;
   }

   // There is no way for the compositor to know how long the layer tree
   // construction took. Fortunately, the layer tree does. Grab that time
   // for instrumentation.
   compositor_context_->ui_time().SetLapTime(layer_tree.build_time());

   auto* external_view_embedder = surface_->GetExternalViewEmbedder();

   SkCanvas* embedder_root_canvas = nullptr;
   if (external_view_embedder != nullptr) {
     external_view_embedder->BeginFrame(layer_tree.frame_size(),
                                        surface_->GetContext(),
                                        layer_tree.device_pixel_ratio());
     embedder_root_canvas = external_view_embedder->GetRootCanvas();
   }

   // If the external view embedder has specified an optional root surface, the
   // root surface transformation is set by the embedder instead of
   // having to apply it here.
   SkMatrix root_surface_transformation =
       embedder_root_canvas ? SkMatrix{} : surface_->GetRootTransformation();

   auto root_surface_canvas =
       embedder_root_canvas ? embedder_root_canvas : frame->SkiaCanvas();

   auto compositor_frame = compositor_context_->AcquireFrame(
       surface_->GetContext(),       // skia GrContext
       root_surface_canvas,          // root surface canvas
       external_view_embedder,       // external view embedder
       root_surface_transformation,  // root surface transformation
       true,                         // instrumentation enabled
       frame->supports_readback(),   // surface supports pixel reads
       raster_thread_merger_         // thread merger
   );

   if (compositor_frame) {
     RasterStatus raster_status = compositor_frame->Raster(layer_tree, false);
     if (raster_status == RasterStatus::kFailed) {
       return raster_status;
     }
     if (external_view_embedder != nullptr) {
       external_view_embedder->SubmitFrame(surface_->GetContext(),
                                           root_surface_canvas);
       // The external view embedder may mutate the root surface canvas while
       // submitting the frame.
       // Therefore, submit the final frame after asking the external view
       // embedder to submit the frame.
       frame->Submit();
       external_view_embedder->FinishFrame();
     } else {
       frame->Submit();
     }

     FireNextFrameCallbackIfPresent();

     if (surface_->GetContext()) {
       TRACE_EVENT0("flutter", "PerformDeferredSkiaCleanup");
       surface_->GetContext()->performDeferredCleanup(kSkiaCleanupExpiration);
     }

     return raster_status;
   }

   return RasterStatus::kFailed;
 }

 static sk_sp<SkData> SerializeTypeface(SkTypeface* typeface, void* ctx) {
   return typeface->serialize(SkTypeface::SerializeBehavior::kDoIncludeData);
 }

 static sk_sp<SkData> ScreenshotLayerTreeAsPicture(
     flutter::LayerTree* tree,
     flutter::CompositorContext& compositor_context) {
   FML_DCHECK(tree != nullptr);
   SkPictureRecorder recorder;
   recorder.beginRecording(
       SkRect::MakeWH(tree->frame_size().width(), tree->frame_size().height()));

   SkMatrix root_surface_transformation;
   root_surface_transformation.reset();

   // TODO(amirh): figure out how to take a screenshot with embedded UIView.
   // https://github.com/flutter/flutter/issues/23435
   auto frame = compositor_context.AcquireFrame(
       nullptr, recorder.getRecordingCanvas(), nullptr,
       root_surface_transformation, false, true, nullptr);

   frame->Raster(*tree, true);

   SkSerialProcs procs = {0};
   procs.fTypefaceProc = SerializeTypeface;

   return recorder.finishRecordingAsPicture()->serialize(&procs);
 }

 static sk_sp<SkSurface> CreateSnapshotSurface(GrContext* surface_context,
                                               const SkISize& size) {
   const auto image_info = SkImageInfo::MakeN32Premul(
       size.width(), size.height(), SkColorSpace::MakeSRGB());
   if (surface_context) {
     // There is a rendering surface that may contain textures that are going to
     // be referenced in the layer tree about to be drawn.
     return SkSurface::MakeRenderTarget(surface_context,  //
                                        SkBudgeted::kNo,  //
                                        image_info        //
     );
   }

   // There is no rendering surface, assume no GPU textures are present and
   // create a raster surface.
   return SkSurface::MakeRaster(image_info);
 }

 static sk_sp<SkData> ScreenshotLayerTreeAsImage(
     flutter::LayerTree* tree,
     flutter::CompositorContext& compositor_context,
     GrContext* surface_context,
     bool compressed) {
   // Attempt to create a snapshot surface depending on whether we have access to
   // a valid GPU rendering context.
   auto snapshot_surface =
       CreateSnapshotSurface(surface_context, tree->frame_size());
   if (snapshot_surface == nullptr) {
     FML_LOG(ERROR) << "Screenshot: unable to create snapshot surface";
     return nullptr;
   }

   // Draw the current layer tree into the snapshot surface.
   auto* canvas = snapshot_surface->getCanvas();

   // There is no root surface transformation for the screenshot layer. Reset the
   // matrix to identity.
   SkMatrix root_surface_transformation;
   root_surface_transformation.reset();

   // We want to ensure we call the base method for
   // CompositorContext::AcquireFrame instead of the platform-specific method.
   // Specifically, Fuchsia's CompositorContext handles the rendering surface
   // itself which means that we will still continue to render to the onscreen
   // surface if we don't call the base method.
   auto frame = compositor_context.flutter::CompositorContext::AcquireFrame(
       surface_context, canvas, nullptr, root_surface_transformation, false,
       true, nullptr);
   canvas->clear(SK_ColorTRANSPARENT);
   frame->Raster(*tree, true);
   canvas->flush();

   // Prepare an image from the surface, this image may potentially be on th GPU.
   auto potentially_gpu_snapshot = snapshot_surface->makeImageSnapshot();
   if (!potentially_gpu_snapshot) {
     FML_LOG(ERROR) << "Screenshot: unable to make image screenshot";
     return nullptr;
   }

   // Copy the GPU image snapshot into CPU memory.
   auto cpu_snapshot = potentially_gpu_snapshot->makeRasterImage();
   if (!cpu_snapshot) {
     FML_LOG(ERROR) << "Screenshot: unable to make raster image";
     return nullptr;
   }

   // If the caller want the pixels to be compressed, there is a Skia utility to
   // compress to PNG. Use that.
   if (compressed) {
     return cpu_snapshot->encodeToData();
   }

   // Copy it into a bitmap and return the same.
   SkPixmap pixmap;
   if (!cpu_snapshot->peekPixels(&pixmap)) {
     FML_LOG(ERROR) << "Screenshot: unable to obtain bitmap pixels";
     return nullptr;
   }

   return SkData::MakeWithCopy(pixmap.addr32(), pixmap.computeByteSize());
 }

 Rasterizer::Screenshot Rasterizer::ScreenshotLastLayerTree(
     Rasterizer::ScreenshotType type,
     bool base64_encode) {
   auto* layer_tree = GetLastLayerTree();
   if (layer_tree == nullptr) {
     FML_LOG(ERROR) << "Last layer tree was null when screenshotting.";
     return {};
   }

   sk_sp<SkData> data = nullptr;

   GrContext* surface_context = surface_ ? surface_->GetContext() : nullptr;

   switch (type) {
     case ScreenshotType::SkiaPicture:
       data = ScreenshotLayerTreeAsPicture(layer_tree, *compositor_context_);
       break;
     case ScreenshotType::UncompressedImage:
       data = ScreenshotLayerTreeAsImage(layer_tree, *compositor_context_,
                                         surface_context, false);
       break;
     case ScreenshotType::CompressedImage:
       data = ScreenshotLayerTreeAsImage(layer_tree, *compositor_context_,
                                         surface_context, true);
       break;
   }

   if (data == nullptr) {
     FML_LOG(ERROR) << "Screenshot data was null.";
     return {};
   }

   if (base64_encode) {
     size_t b64_size = SkBase64::Encode(data->data(), data->size(), nullptr);
     auto b64_data = SkData::MakeUninitialized(b64_size);
     SkBase64::Encode(data->data(), data->size(), b64_data->writable_data());
     return Rasterizer::Screenshot{b64_data, layer_tree->frame_size()};
   }

   return Rasterizer::Screenshot{data, layer_tree->frame_size()};
 }

 void Rasterizer::SetNextFrameCallback(const fml::closure& callback) {
   next_frame_callback_ = callback;
 }

 void Rasterizer::FireNextFrameCallbackIfPresent() {
   if (!next_frame_callback_) {
     return;
   }
   // It is safe for the callback to set a new callback.
   auto callback = next_frame_callback_;
   next_frame_callback_ = nullptr;
   callback();
 }

 void Rasterizer::SetResourceCacheMaxBytes(size_t max_bytes, bool from_user) {
   user_override_resource_cache_bytes_ |= from_user;

   if (!from_user && user_override_resource_cache_bytes_) {
     // We should not update the setting here if a user has explicitly set a
     // value for this over the flutter/skia channel.
     return;
   }

   max_cache_bytes_ = max_bytes;
   if (!surface_) {
     return;
   }

   GrContext* context = surface_->GetContext();
   if (context) {
     int max_resources;
     context->getResourceCacheLimits(&max_resources, nullptr);
     context->setResourceCacheLimits(max_resources, max_bytes);
   }
 }

 std::optional<size_t> Rasterizer::GetResourceCacheMaxBytes() const {
   if (!surface_) {
     return std::nullopt;
   }
   GrContext* context = surface_->GetContext();
   if (context) {
     size_t max_bytes;
     context->getResourceCacheLimits(nullptr, &max_bytes);
     return max_bytes;
   }
   return std::nullopt;
 }

 Rasterizer::Screenshot::Screenshot() {}

 Rasterizer::Screenshot::Screenshot(sk_sp<SkData> p_data, SkISize p_size)
     : data(std::move(p_data)), frame_size(p_size) {}

 Rasterizer::Screenshot::Screenshot(const Screenshot& other) = default;

 Rasterizer::Screenshot::~Screenshot() = default;

 }  // namespace flutter
	// Copyright 2013 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.

	#include "flutter/shell/common/rasterizer.h"

	#include "flutter/shell/common/persistent_cache.h"

	#include <utility>

	#include "flutter/fml/time/time_delta.h"
	#include "flutter/fml/time/time_point.h"
	#include "third_party/skia/include/core/SkEncodedImageFormat.h"
	#include "third_party/skia/include/core/SkImageEncoder.h"
	#include "third_party/skia/include/core/SkPictureRecorder.h"
	#include "third_party/skia/include/core/SkSerialProcs.h"
	#include "third_party/skia/include/core/SkSurface.h"
	#include "third_party/skia/include/core/SkSurfaceCharacterization.h"
	#include "third_party/skia/include/utils/SkBase64.h"

	namespace flutter {

	// The rasterizer will tell Skia to purge cached resources that have not been
	// used within this interval.
	static constexpr std::chrono::milliseconds kSkiaCleanupExpiration(15000);

	// TODO(dnfield): Remove this once internal embedders have caught up.
	static Rasterizer::DummyDelegate dummy_delegate_;
	Rasterizer::Rasterizer(
	TaskRunners task_runners,
	std::unique_ptr<flutter::CompositorContext> compositor_context)
	: Rasterizer(dummy_delegate_,
	std::move(task_runners),
	std::move(compositor_context)) {}

	Rasterizer::Rasterizer(Delegate& delegate, TaskRunners task_runners)
	: Rasterizer(delegate,
	std::move(task_runners),
	std::make_unique<flutter::CompositorContext>(
	delegate.GetFrameBudget())) {}

	Rasterizer::Rasterizer(
	Delegate& delegate,
	TaskRunners task_runners,
	std::unique_ptr<flutter::CompositorContext> compositor_context)
	: delegate_(delegate),
	task_runners_(std::move(task_runners)),
	compositor_context_(std::move(compositor_context)),
	user_override_resource_cache_bytes_(false),
	weak_factory_(this) {
	FML_DCHECK(compositor_context_);
	}

	Rasterizer::~Rasterizer() = default;

	fml::TaskRunnerAffineWeakPtr<Rasterizer> Rasterizer::GetWeakPtr() const {
	return weak_factory_.GetTaskRunnerAffineWeakPtr();
	}

	fml::WeakPtr<SnapshotDelegate> Rasterizer::GetSnapshotDelegate() const {
	return weak_factory_.GetWeakPtr();
	}

	void Rasterizer::Setup(std::unique_ptr<Surface> surface) {
	surface_ = std::move(surface);
	if (max_cache_bytes_.has_value()) {
	SetResourceCacheMaxBytes(max_cache_bytes_.value(),
	user_override_resource_cache_bytes_);
	}
	compositor_context_->OnGrContextCreated();
	if (surface_->GetExternalViewEmbedder()) {
	const auto platform_id =
	task_runners_.GetPlatformTaskRunner()->GetTaskQueueId();
	const auto gpu_id = task_runners_.GetRasterTaskRunner()->GetTaskQueueId();
	raster_thread_merger_ =
	fml::MakeRefCounted<fml::RasterThreadMerger>(platform_id, gpu_id);
	}
	}

	void Rasterizer::Teardown() {
	compositor_context_->OnGrContextDestroyed();
	surface_.reset();
	last_layer_tree_.reset();
	}

	void Rasterizer::NotifyLowMemoryWarning() const {
	if (!surface_) {
	FML_DLOG(INFO) << "Rasterizer::PurgeCaches called with no surface.";
	return;
	}
	auto context = surface_->GetContext();
	if (!context) {
	FML_DLOG(INFO) << "Rasterizer::PurgeCaches called with no GrContext.";
	return;
	}
	context->freeGpuResources();
	}

	flutter::TextureRegistry* Rasterizer::GetTextureRegistry() {
	return &compositor_context_->texture_registry();
	}

	flutter::LayerTree* Rasterizer::GetLastLayerTree() {
	return last_layer_tree_.get();
	}

	void Rasterizer::DrawLastLayerTree() {
	if (!last_layer_tree_ \|\| !surface_) {
	return;
	}
	DrawToSurface(*last_layer_tree_);
	}

	void Rasterizer::Draw(fml::RefPtr<Pipeline<flutter::LayerTree>> pipeline) {
	TRACE_EVENT0("flutter", "GPURasterizer::Draw");
	if (raster_thread_merger_ &&
	!raster_thread_merger_->IsOnRasterizingThread()) {
	// we yield and let this frame be serviced on the right thread.
	return;
	}
	FML_DCHECK(task_runners_.GetRasterTaskRunner()->RunsTasksOnCurrentThread());

	RasterStatus raster_status = RasterStatus::kFailed;
	Pipeline<flutter::LayerTree>::Consumer consumer =
	[&](std::unique_ptr<LayerTree> layer_tree) {
	raster_status = DoDraw(std::move(layer_tree));
	};

	PipelineConsumeResult consume_result = pipeline->Consume(consumer);
	// if the raster status is to resubmit the frame, we push the frame to the
	// front of the queue and also change the consume status to more available.
	if (raster_status == RasterStatus::kResubmit) {
	auto front_continuation = pipeline->ProduceIfEmpty();
	bool result =
	front_continuation.Complete(std::move(resubmitted_layer_tree_));
	if (result) {
	consume_result = PipelineConsumeResult::MoreAvailable;
	}
	} else if (raster_status == RasterStatus::kEnqueuePipeline) {
	consume_result = PipelineConsumeResult::MoreAvailable;
	}

	// Merging the thread as we know the next `Draw` should be run on the platform
	// thread.
	if (raster_status == RasterStatus::kResubmit) {
	auto* external_view_embedder = surface_->GetExternalViewEmbedder();
	// We know only the `external_view_embedder` can
	// causes\|RasterStatus::kResubmit\|. Check to make sure.
	FML_DCHECK(external_view_embedder != nullptr);
	external_view_embedder->EndFrame(raster_thread_merger_);
	}

	// Consume as many pipeline items as possible. But yield the event loop
	// between successive tries.
	switch (consume_result) {
	case PipelineConsumeResult::MoreAvailable: {
	task_runners_.GetRasterTaskRunner()->PostTask(
	[weak_this = weak_factory_.GetTaskRunnerAffineWeakPtr(), pipeline]() {
	if (weak_this) {
	weak_this->Draw(pipeline);
	}
	});
	break;
	}
	default:
	break;
	}
	}

	sk_sp<SkImage> Rasterizer::DoMakeRasterSnapshot(
	SkISize size,
	std::function<void(SkCanvas*)> draw_callback) {
	TRACE_EVENT0("flutter", __FUNCTION__);

	sk_sp<SkSurface> surface;
	SkImageInfo image_info = SkImageInfo::MakeN32Premul(
	size.width(), size.height(), SkColorSpace::MakeSRGB());
	if (surface_ == nullptr \|\| surface_->GetContext() == nullptr) {
	// Raster surface is fine if there is no on screen surface. This might
	// happen in case of software rendering.
	surface = SkSurface::MakeRaster(image_info);
	} else {
	if (!surface_->MakeRenderContextCurrent()) {
	return nullptr;
	}

	// When there is an on screen surface, we need a render target SkSurface
	// because we want to access texture backed images.
	surface = SkSurface::MakeRenderTarget(surface_->GetContext(), // context
	SkBudgeted::kNo, // budgeted
	image_info // image info
	);
	}

	if (surface == nullptr \|\| surface->getCanvas() == nullptr) {
	return nullptr;
	}

	draw_callback(surface->getCanvas());
	surface->getCanvas()->flush();

	sk_sp<SkImage> device_snapshot;
	{
	TRACE_EVENT0("flutter", "MakeDeviceSnpashot");
	device_snapshot = surface->makeImageSnapshot();
	}

	if (device_snapshot == nullptr) {
	return nullptr;
	}

	{
	TRACE_EVENT0("flutter", "DeviceHostTransfer");
	if (auto raster_image = device_snapshot->makeRasterImage()) {
	return raster_image;
	}
	}

	return nullptr;
	}

	sk_sp<SkImage> Rasterizer::MakeRasterSnapshot(sk_sp<SkPicture> picture,
	SkISize picture_size) {
	return DoMakeRasterSnapshot(picture_size,
	[picture = std::move(picture)](SkCanvas* canvas) {
	canvas->drawPicture(picture);
	});
	}

	sk_sp<SkImage> Rasterizer::ConvertToRasterImage(sk_sp<SkImage> image) {
	TRACE_EVENT0("flutter", __FUNCTION__);

	// If the rasterizer does not have a surface with a GrContext, then it will
	// be unable to render a cross-context SkImage. The caller will need to
	// create the raster image on the IO thread.
	if (surface_ == nullptr \|\| surface_->GetContext() == nullptr) {
	return nullptr;
	}

	if (image == nullptr) {
	return nullptr;
	}

	return DoMakeRasterSnapshot(image->dimensions(),
	[image = std::move(image)](SkCanvas* canvas) {
	canvas->drawImage(image, 0, 0);
	});
	}

	RasterStatus Rasterizer::DoDraw(
	std::unique_ptr<flutter::LayerTree> layer_tree) {
	FML_DCHECK(task_runners_.GetRasterTaskRunner()->RunsTasksOnCurrentThread());

	if (!layer_tree \|\| !surface_) {
	return RasterStatus::kFailed;
	}

	FrameTiming timing;
	const fml::TimePoint frame_target_time = layer_tree->target_time();
	timing.Set(FrameTiming::kBuildStart, layer_tree->build_start());
	timing.Set(FrameTiming::kBuildFinish, layer_tree->build_finish());
	timing.Set(FrameTiming::kRasterStart, fml::TimePoint::Now());

	PersistentCache* persistent_cache = PersistentCache::GetCacheForProcess();
	persistent_cache->ResetStoredNewShaders();

	RasterStatus raster_status = DrawToSurface(*layer_tree);
	if (raster_status == RasterStatus::kSuccess) {
	last_layer_tree_ = std::move(layer_tree);
	} else if (raster_status == RasterStatus::kResubmit) {
	resubmitted_layer_tree_ = std::move(layer_tree);
	return raster_status;
	}

	if (persistent_cache->IsDumpingSkp() &&
	persistent_cache->StoredNewShaders()) {
	auto screenshot =
	ScreenshotLastLayerTree(ScreenshotType::SkiaPicture, false);
	persistent_cache->DumpSkp(*screenshot.data);
	}

	// TODO(liyuqian): in Fuchsia, the rasterization doesn't finish when
	// Rasterizer::DoDraw finishes. Future work is needed to adapt the timestamp
	// for Fuchsia to capture SceneUpdateContext::ExecutePaintTasks.
	const auto raster_finish_time = fml::TimePoint::Now();
	timing.Set(FrameTiming::kRasterFinish, raster_finish_time);
	delegate_.OnFrameRasterized(timing);

	if (raster_finish_time > frame_target_time) {
	fml::TimePoint latest_frame_target_time =
	delegate_.GetLatestFrameTargetTime();
	const auto frame_budget_millis = delegate_.GetFrameBudget().count();
	if (latest_frame_target_time < raster_finish_time) {
	latest_frame_target_time =
	latest_frame_target_time +
	fml::TimeDelta::FromMillisecondsF(frame_budget_millis);
	}
	const auto frame_lag =
	(latest_frame_target_time - frame_target_time).ToMillisecondsF();
	const int vsync_transitions_missed = round(frame_lag / frame_budget_millis);
	fml::tracing::TraceEventAsyncComplete(
	"flutter", // category
	"SceneDisplayLag", // name
	raster_finish_time, // begin_time
	latest_frame_target_time, // end_time
	"frame_target_time", // arg_key_1
	frame_target_time, // arg_val_1
	"current_frame_target_time", // arg_key_2
	latest_frame_target_time, // arg_val_2
	"vsync_transitions_missed", // arg_key_3
	vsync_transitions_missed // arg_val_3
	);
	}

	// Pipeline pressure is applied from a couple of places:
	// rasterizer: When there are more items as of the time of Consume.
	// animator (via shell): Frame gets produces every vsync.
	// Enqueing here is to account for the following scenario:
	// T = 1
	// - one item (A) in the pipeline
	// - rasterizer starts (and merges the threads)
	// - pipeline consume result says no items to process
	// T = 2
	// - animator produces (B) to the pipeline
	// - applies pipeline pressure via platform thread.
	// T = 3
	// - rasterizes finished (and un-merges the threads)
	// - \|Draw\| for B yields as its on the wrong thread.
	// This enqueue ensures that we attempt to consume from the right
	// thread one more time after un-merge.
	if (raster_thread_merger_) {
	if (raster_thread_merger_->DecrementLease() ==
	fml::RasterThreadStatus::kUnmergedNow) {
	return RasterStatus::kEnqueuePipeline;
	}
	}

	return raster_status;
	}

	RasterStatus Rasterizer::DrawToSurface(flutter::LayerTree& layer_tree) {
	TRACE_EVENT0("flutter", "Rasterizer::DrawToSurface");
	FML_DCHECK(surface_);

	auto frame = surface_->AcquireFrame(layer_tree.frame_size());

	if (frame == nullptr) {
	return RasterStatus::kFailed;
	}

	// There is no way for the compositor to know how long the layer tree
	// construction took. Fortunately, the layer tree does. Grab that time
	// for instrumentation.
	compositor_context_->ui_time().SetLapTime(layer_tree.build_time());

	auto* external_view_embedder = surface_->GetExternalViewEmbedder();

	SkCanvas* embedder_root_canvas = nullptr;
	if (external_view_embedder != nullptr) {
	external_view_embedder->BeginFrame(layer_tree.frame_size(),
	surface_->GetContext(),
	layer_tree.device_pixel_ratio());
	embedder_root_canvas = external_view_embedder->GetRootCanvas();
	}

	// If the external view embedder has specified an optional root surface, the
	// root surface transformation is set by the embedder instead of
	// having to apply it here.
	SkMatrix root_surface_transformation =
	embedder_root_canvas ? SkMatrix{} : surface_->GetRootTransformation();

	auto root_surface_canvas =
	embedder_root_canvas ? embedder_root_canvas : frame->SkiaCanvas();

	auto compositor_frame = compositor_context_->AcquireFrame(
	surface_->GetContext(), // skia GrContext
	root_surface_canvas, // root surface canvas
	external_view_embedder, // external view embedder
	root_surface_transformation, // root surface transformation
	true, // instrumentation enabled
	frame->supports_readback(), // surface supports pixel reads
	raster_thread_merger_ // thread merger
	);

	if (compositor_frame) {
	RasterStatus raster_status = compositor_frame->Raster(layer_tree, false);
	if (raster_status == RasterStatus::kFailed) {
	return raster_status;
	}
	if (external_view_embedder != nullptr) {
	external_view_embedder->SubmitFrame(surface_->GetContext(),
	root_surface_canvas);
	// The external view embedder may mutate the root surface canvas while
	// submitting the frame.
	// Therefore, submit the final frame after asking the external view
	// embedder to submit the frame.
	frame->Submit();
	external_view_embedder->FinishFrame();
	} else {
	frame->Submit();
	}

	FireNextFrameCallbackIfPresent();

	if (surface_->GetContext()) {
	TRACE_EVENT0("flutter", "PerformDeferredSkiaCleanup");
	surface_->GetContext()->performDeferredCleanup(kSkiaCleanupExpiration);
	}

	return raster_status;
	}

	return RasterStatus::kFailed;
	}

	static sk_sp<SkData> SerializeTypeface(SkTypeface* typeface, void* ctx) {
	return typeface->serialize(SkTypeface::SerializeBehavior::kDoIncludeData);
	}

	static sk_sp<SkData> ScreenshotLayerTreeAsPicture(
	flutter::LayerTree* tree,
	flutter::CompositorContext& compositor_context) {
	FML_DCHECK(tree != nullptr);
	SkPictureRecorder recorder;
	recorder.beginRecording(
	SkRect::MakeWH(tree->frame_size().width(), tree->frame_size().height()));

	SkMatrix root_surface_transformation;
	root_surface_transformation.reset();

	// TODO(amirh): figure out how to take a screenshot with embedded UIView.
	// https://github.com/flutter/flutter/issues/23435
	auto frame = compositor_context.AcquireFrame(
	nullptr, recorder.getRecordingCanvas(), nullptr,
	root_surface_transformation, false, true, nullptr);

	frame->Raster(*tree, true);

	SkSerialProcs procs = {0};
	procs.fTypefaceProc = SerializeTypeface;

	return recorder.finishRecordingAsPicture()->serialize(&procs);
	}

	static sk_sp<SkSurface> CreateSnapshotSurface(GrContext* surface_context,
	const SkISize& size) {
	const auto image_info = SkImageInfo::MakeN32Premul(
	size.width(), size.height(), SkColorSpace::MakeSRGB());
	if (surface_context) {
	// There is a rendering surface that may contain textures that are going to
	// be referenced in the layer tree about to be drawn.
	return SkSurface::MakeRenderTarget(surface_context, //
	SkBudgeted::kNo, //
	image_info //
	);
	}

	// There is no rendering surface, assume no GPU textures are present and
	// create a raster surface.
	return SkSurface::MakeRaster(image_info);
	}

	static sk_sp<SkData> ScreenshotLayerTreeAsImage(
	flutter::LayerTree* tree,
	flutter::CompositorContext& compositor_context,
	GrContext* surface_context,
	bool compressed) {
	// Attempt to create a snapshot surface depending on whether we have access to
	// a valid GPU rendering context.
	auto snapshot_surface =
	CreateSnapshotSurface(surface_context, tree->frame_size());
	if (snapshot_surface == nullptr) {
	FML_LOG(ERROR) << "Screenshot: unable to create snapshot surface";
	return nullptr;
	}

	// Draw the current layer tree into the snapshot surface.
	auto* canvas = snapshot_surface->getCanvas();

	// There is no root surface transformation for the screenshot layer. Reset the
	// matrix to identity.
	SkMatrix root_surface_transformation;
	root_surface_transformation.reset();

	// We want to ensure we call the base method for
	// CompositorContext::AcquireFrame instead of the platform-specific method.
	// Specifically, Fuchsia's CompositorContext handles the rendering surface
	// itself which means that we will still continue to render to the onscreen
	// surface if we don't call the base method.
	auto frame = compositor_context.flutter::CompositorContext::AcquireFrame(
	surface_context, canvas, nullptr, root_surface_transformation, false,
	true, nullptr);
	canvas->clear(SK_ColorTRANSPARENT);
	frame->Raster(*tree, true);
	canvas->flush();

	// Prepare an image from the surface, this image may potentially be on th GPU.
	auto potentially_gpu_snapshot = snapshot_surface->makeImageSnapshot();
	if (!potentially_gpu_snapshot) {
	FML_LOG(ERROR) << "Screenshot: unable to make image screenshot";
	return nullptr;
	}

	// Copy the GPU image snapshot into CPU memory.
	auto cpu_snapshot = potentially_gpu_snapshot->makeRasterImage();
	if (!cpu_snapshot) {
	FML_LOG(ERROR) << "Screenshot: unable to make raster image";
	return nullptr;
	}

	// If the caller want the pixels to be compressed, there is a Skia utility to
	// compress to PNG. Use that.
	if (compressed) {
	return cpu_snapshot->encodeToData();
	}

	// Copy it into a bitmap and return the same.
	SkPixmap pixmap;
	if (!cpu_snapshot->peekPixels(&pixmap)) {
	FML_LOG(ERROR) << "Screenshot: unable to obtain bitmap pixels";
	return nullptr;
	}

	return SkData::MakeWithCopy(pixmap.addr32(), pixmap.computeByteSize());
	}

	Rasterizer::Screenshot Rasterizer::ScreenshotLastLayerTree(
	Rasterizer::ScreenshotType type,
	bool base64_encode) {
	auto* layer_tree = GetLastLayerTree();
	if (layer_tree == nullptr) {
	FML_LOG(ERROR) << "Last layer tree was null when screenshotting.";
	return {};
	}

	sk_sp<SkData> data = nullptr;

	GrContext* surface_context = surface_ ? surface_->GetContext() : nullptr;

	switch (type) {
	case ScreenshotType::SkiaPicture:
	data = ScreenshotLayerTreeAsPicture(layer_tree, *compositor_context_);
	break;
	case ScreenshotType::UncompressedImage:
	data = ScreenshotLayerTreeAsImage(layer_tree, *compositor_context_,
	surface_context, false);
	break;
	case ScreenshotType::CompressedImage:
	data = ScreenshotLayerTreeAsImage(layer_tree, *compositor_context_,
	surface_context, true);
	break;
	}

	if (data == nullptr) {
	FML_LOG(ERROR) << "Screenshot data was null.";
	return {};
	}

	if (base64_encode) {
	size_t b64_size = SkBase64::Encode(data->data(), data->size(), nullptr);
	auto b64_data = SkData::MakeUninitialized(b64_size);
	SkBase64::Encode(data->data(), data->size(), b64_data->writable_data());
	return Rasterizer::Screenshot{b64_data, layer_tree->frame_size()};
	}

	return Rasterizer::Screenshot{data, layer_tree->frame_size()};
	}

	void Rasterizer::SetNextFrameCallback(const fml::closure& callback) {
	next_frame_callback_ = callback;
	}

	void Rasterizer::FireNextFrameCallbackIfPresent() {
	if (!next_frame_callback_) {
	return;
	}
	// It is safe for the callback to set a new callback.
	auto callback = next_frame_callback_;
	next_frame_callback_ = nullptr;
	callback();
	}

	void Rasterizer::SetResourceCacheMaxBytes(size_t max_bytes, bool from_user) {
	user_override_resource_cache_bytes_ \|= from_user;

	if (!from_user && user_override_resource_cache_bytes_) {
	// We should not update the setting here if a user has explicitly set a
	// value for this over the flutter/skia channel.
	return;
	}

	max_cache_bytes_ = max_bytes;
	if (!surface_) {
	return;
	}

	GrContext* context = surface_->GetContext();
	if (context) {
	int max_resources;
	context->getResourceCacheLimits(&max_resources, nullptr);
	context->setResourceCacheLimits(max_resources, max_bytes);
	}
	}

	std::optional<size_t> Rasterizer::GetResourceCacheMaxBytes() const {
	if (!surface_) {
	return std::nullopt;
	}
	GrContext* context = surface_->GetContext();
	if (context) {
	size_t max_bytes;
	context->getResourceCacheLimits(nullptr, &max_bytes);
	return max_bytes;
	}
	return std::nullopt;
	}

	Rasterizer::Screenshot::Screenshot() {}

	Rasterizer::Screenshot::Screenshot(sk_sp<SkData> p_data, SkISize p_size)
	: data(std::move(p_data)), frame_size(p_size) {}

	Rasterizer::Screenshot::Screenshot(const Screenshot& other) = default;

	Rasterizer::Screenshot::~Screenshot() = default;

	} // namespace flutter