cc/blimp: Add a LayerTreeHostRemote implementation.

cc/blimp/layer_tree_host_remote.cc

+// Copyright 2016 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 "cc/blimp/layer_tree_host_remote.h"
+
+#include "base/atomic_sequence_num.h"
+#include "base/memory/ptr_util.h"
+#include "cc/animation/animation_host.h"
+#include "cc/blimp/compositor_proto_state.h"
+#include "cc/blimp/remote_compositor_bridge.h"
+#include "cc/output/begin_frame_args.h"
+#include "cc/output/compositor_frame_sink.h"
+#include "cc/trees/layer_tree.h"
+#include "cc/trees/layer_tree_host_client.h"
+#include "cc/trees/layer_tree_host_common.h"
+#include "cc/trees/task_runner_provider.h"
+
+namespace cc {
+namespace {
+// We use a 16ms default frame interval because the rate at which the engine
+// produces main frames doesn't matter.
+base::TimeDelta kDefaultFrameInterval = base::TimeDelta::FromMilliseconds(16);
+
+static base::StaticAtomicSequenceNumber s_layer_tree_host_sequence_number;
+}  // namespace
+
+LayerTreeHostRemote::InitParams::InitParams() = default;
+
+LayerTreeHostRemote::InitParams::~InitParams() = default;
+
+LayerTreeHostRemote::LayerTreeHostRemote(InitParams* params)
+    : LayerTreeHostRemote(
+          params,
+          base::MakeUnique<LayerTree>(std::move(params->animation_host),
+                                      this)) {}
+
+LayerTreeHostRemote::LayerTreeHostRemote(InitParams* params,
+                                         std::unique_ptr<LayerTree> layer_tree)
+    : id_(s_layer_tree_host_sequence_number.GetNext() + 1),
+      main_frame_requested_from_bridge_(false),
+      client_(params->client),
+      task_runner_provider_(
+          TaskRunnerProvider::Create(std::move(params->main_task_runner),
+                                     nullptr)),
+      remote_compositor_bridge_(std::move(params->remote_compositor_bridge)),
+      settings_(*params->settings),
+      layer_tree_(std::move(layer_tree)),
+      weak_factory_(this) {
+  DCHECK(task_runner_provider_->IsMainThread());
+  DCHECK(remote_compositor_bridge_);
+  DCHECK(client_);
+  remote_compositor_bridge_->BindToClient(this);
+}
+
+LayerTreeHostRemote::~LayerTreeHostRemote() = default;
+
+int LayerTreeHostRemote::GetId() const {
+  return id_;
+}
+
+int LayerTreeHostRemote::SourceFrameNumber() const {
+  return source_frame_number_;
+}
+
+LayerTree* LayerTreeHostRemote::GetLayerTree() {
+  return layer_tree_.get();
+}
+
+const LayerTree* LayerTreeHostRemote::GetLayerTree() const {
+  return layer_tree_.get();
+}
+
+UIResourceManager* LayerTreeHostRemote::GetUIResourceManager() const {
+  // We shouldn't need a UIResourceManager. The layers which need this
+  // (UIResourceLayers and PaintedScrollbarLayers) are never used by the
+  // renderer compositor in remote mode.
+  NOTREACHED() << "UIResourceManager requested. Unsupported Layer type used";
+  return nullptr;
+}
+
+TaskRunnerProvider* LayerTreeHostRemote::GetTaskRunnerProvider() const {
+  return task_runner_provider_.get();
+}
+
+const LayerTreeSettings& LayerTreeHostRemote::GetSettings() const {
+  return settings_;
+}
+
+void LayerTreeHostRemote::SetFrameSinkId(const FrameSinkId& frame_sink_id) {
+  // We don't need to care about SurfaceLayers. The Surfaces system is
+  // relevant on the client only.
+}
+
+void LayerTreeHostRemote::SetLayerTreeMutator(
+    std::unique_ptr<LayerTreeMutator> mutator) {
+  // TODO(khushalsagar): Compositor-worker not supported. See crbug.com/650876.
+}
+
+void LayerTreeHostRemote::QueueSwapPromise(
+    std::unique_ptr<SwapPromise> swap_promise) {
+  swap_promise_manager_.QueueSwapPromise(std::move(swap_promise));
+}
+
+SwapPromiseManager* LayerTreeHostRemote::GetSwapPromiseManager() {
+  return &swap_promise_manager_;
+}
+
+void LayerTreeHostRemote::SetHasGpuRasterizationTrigger(bool has_trigger) {
+  // TODO(khushalsagar) : Take care of Gpu raster. See crbug.com/650431.
+}
+
+void LayerTreeHostRemote::SetVisible(bool visible) {
+  // The visibility of the compositor is controlled on the client, which is
+  // why this value is not sent there, since the client has the current true
+  // state.
+  visible_ = visible;
+}
+
+bool LayerTreeHostRemote::IsVisible() const {
+  return visible_;
+}
+
+void LayerTreeHostRemote::SetCompositorFrameSink(
+    std::unique_ptr<CompositorFrameSink> compositor_frame_sink) {
+  NOTREACHED()
+      << "The LayerTreeHostClient is never asked for a CompositorFrameSink";
+}
+
+std::unique_ptr<CompositorFrameSink>
+LayerTreeHostRemote::ReleaseCompositorFrameSink() {
+  // Since we never have a CompositorFrameSink, this is always a no-op.
+  return nullptr;
+}
+
+void LayerTreeHostRemote::SetNeedsAnimate() {
+  MainFrameRequested(FramePipelineStage::ANIMATE);
+}
+
+void LayerTreeHostRemote::SetNeedsUpdateLayers() {
+  MainFrameRequested(FramePipelineStage::UPDATE_LAYERS);
+}
+
+void LayerTreeHostRemote::SetNeedsCommit() {
+  MainFrameRequested(FramePipelineStage::COMMIT);
+}
+
+bool LayerTreeHostRemote::BeginMainFrameRequested() const {
+  return requested_pipeline_stage_for_next_frame_ != FramePipelineStage::NONE;
+}
+
+bool LayerTreeHostRemote::CommitRequested() const {
+  return requested_pipeline_stage_for_next_frame_ == FramePipelineStage::COMMIT;
+}
+
+void LayerTreeHostRemote::SetDeferCommits(bool defer_commits) {
+  defer_commits_ = defer_commits;
+  ScheduleMainFrameIfNecessary();
+}
+
+void LayerTreeHostRemote::LayoutAndUpdateLayers() {
+  NOTREACHED() << "Only supported in single-threaded mode and this class"
+               << " does not support single-thread since it is out of process";
+}
+
+void LayerTreeHostRemote::Composite(base::TimeTicks frame_begin_time) {
+  NOTREACHED() << "Only supported in single-threaded mode and this class"
+               << " does not support single-thread since it is out of process";
+}
+
+void LayerTreeHostRemote::SetNeedsRedraw() {
+  // The engine shouldn't need to care about draws. CompositorFrames are never
+  // used here.
+  NOTREACHED();
+}
+
+void LayerTreeHostRemote::SetNeedsRedrawRect(const gfx::Rect& damage_rect) {
+  // The engine shouldn't need to care about draws. CompositorFrames are never
+  // used here.
+  // TODO(khushalsagar): The caller could be waiting for an Ack for this redraw.
+  // We need a better solution for this. See crbug.com/651141.
+  NOTIMPLEMENTED();
+}
+
+void LayerTreeHostRemote::SetNextCommitForcesRedraw() {
+  // Ideally the engine shouldn't need to care about draw requests at all. The
+  // compositor that produces CompositorFrames is on the client and draw
+  // requests should be made directly to it on the client itself.
+  NOTREACHED();
+}
+
+void LayerTreeHostRemote::NotifyInputThrottledUntilCommit() {
+  // This notification is used in the case where the renderer handles an input
+  // event, and needs to send an Ack to the browser when the resulting main
+  // frame is committed. If the compositor is taking too long on the pending
+  // tree, the commit processing will be delayed blocking all input as a result.
+  // So this is used to have the compositor activate the pending tree faster, so
+  // the pending commit can be processed.
+  // In remote mode, we don't send such notifications to the client because the
+  // most likely bottleneck is the transport instead of raster. Also, input is
+  // queued on the client, so if raster does end up being a bottleneck, the
+  // input handling code on the client informs the LayerTreeHostInProcess
+  // directly.
+  NOTIMPLEMENTED();
+}
+
+void LayerTreeHostRemote::UpdateTopControlsState(TopControlsState constraints,
+                                                 TopControlsState current,
+                                                 bool animate) {
+  NOTREACHED() << "Using TopControls animations is not supported";
+}
+
+const base::WeakPtr<InputHandler>& LayerTreeHostRemote::GetInputHandler()
+    const {
+  // Input on the compositor thread is handled on the client, so this is always
+  // null.
+  return input_handler_weak_ptr_;
+}
+
+void LayerTreeHostRemote::DidStopFlinging() {
+  // TODO(khushalsagar): This should not happen. See crbug.com/652000.
+  NOTIMPLEMENTED() << "We shouldn't be sending fling gestures to the engine";
+}
+
+void LayerTreeHostRemote::SetDebugState(
+    const LayerTreeDebugState& debug_state) {
+  // TODO(khushalsagar): Figure out if we need to send these to the client.
+  NOTREACHED();
+}
+
+const LayerTreeDebugState& LayerTreeHostRemote::GetDebugState() const {
+  return debug_state_;
+}
+
+int LayerTreeHostRemote::ScheduleMicroBenchmark(
+    const std::string& benchmark_name,
+    std::unique_ptr<base::Value> value,
+    const MicroBenchmark::DoneCallback& callback) {
+  NOTREACHED();
+  return 0;
+}
+
+bool LayerTreeHostRemote::SendMessageToMicroBenchmark(
+    int id,
+    std::unique_ptr<base::Value> value) {
+  NOTREACHED();
+  return false;
+}
+
+SurfaceSequenceGenerator* LayerTreeHostRemote::GetSurfaceSequenceGenerator() {
+  // TODO(khushalsagar): Eliminate the use of this in blink. See
+  // crbug.com/650876.
+  return &surface_sequence_generator_;
+}
+
+void LayerTreeHostRemote::SetNextCommitWaitsForActivation() {
+  // This is used only by layers that need resource synchronization, i.e.,
+  // texture and surface layers, both of which are not supported.
+  NOTIMPLEMENTED() << "Unsupported Layer type used";
+}
+
+void LayerTreeHostRemote::ResetGpuRasterizationTracking() {
+  // TODO(khushalsagar): Take care of Gpu raster. See crbug.com/650431.
+}
+
+void LayerTreeHostRemote::MainFrameRequested(
+    FramePipelineStage requested_pipeline_stage) {
+  DCHECK_NE(FramePipelineStage::NONE, requested_pipeline_stage);
+
+  swap_promise_manager_.NotifySwapPromiseMonitorsOfSetNeedsCommit();
+
+  // If we are inside a main frame update right now and the requested pipeline
+  // stage is higher than the pipeline stage that we are at, then we'll get to
+  // in this main frame update itself. Update the
+  // |max_pipeline_stage_for_current_frame_| to ensure we go through the
+  // requested pipeline stage.
+  if (current_pipeline_stage_ != FramePipelineStage::NONE &&
+      requested_pipeline_stage > current_pipeline_stage_) {
+    max_pipeline_stage_for_current_frame_ = std::max(
+        max_pipeline_stage_for_current_frame_, requested_pipeline_stage);
+    return;
+  }
+
+  // Update the pipeline stage for the next frame and schedule an update if it
+  // has not been scheduled already.
+  requested_pipeline_stage_for_next_frame_ = std::max(
+      requested_pipeline_stage_for_next_frame_, requested_pipeline_stage);
+
+  ScheduleMainFrameIfNecessary();
+}
+
+void LayerTreeHostRemote::ScheduleMainFrameIfNecessary() {
+  // If the client hasn't asked for a main frame, don't schedule one.
+  if (requested_pipeline_stage_for_next_frame_ == FramePipelineStage::NONE)
+    return;
+
+  // If the client does not want us to run main frame updates right now, don't
+  // schedule one.
+  if (defer_commits_)
+    return;
+
+  // If a main frame request is already pending with the
+  // RemoteCompositorBridge, we don't need to scheduler another one.
+  if (main_frame_requested_from_bridge_)
+    return;
+
+  remote_compositor_bridge_->ScheduleMainFrame();
+  main_frame_requested_from_bridge_ = true;
+}
+
+void LayerTreeHostRemote::BeginMainFrame() {
+  DCHECK(main_frame_requested_from_bridge_);
+  DCHECK(task_runner_provider_->IsMainThread());
+
+  main_frame_requested_from_bridge_ = false;
+
+  // The client might have suspended main frames in the meantime. Early out now,
+  // we'll come back here when they enable main frames again.
+  if (defer_commits_)
+    return;
+
+  DCHECK_EQ(current_pipeline_stage_, FramePipelineStage::NONE);
+  DCHECK_EQ(max_pipeline_stage_for_current_frame_, FramePipelineStage::NONE);
+  DCHECK_NE(requested_pipeline_stage_for_next_frame_, FramePipelineStage::NONE);
+
+  // Start the main frame. It should go till the requested pipeline stage.
+  max_pipeline_stage_for_current_frame_ =
+      requested_pipeline_stage_for_next_frame_;
+  requested_pipeline_stage_for_next_frame_ = FramePipelineStage::NONE;
+
+  client_->WillBeginMainFrame();
+
+  current_pipeline_stage_ = FramePipelineStage::ANIMATE;
+  base::TimeTicks now = base::TimeTicks::Now();
+  client_->BeginMainFrame(BeginFrameArgs::Create(
+      BEGINFRAME_FROM_HERE, now, now + kDefaultFrameInterval,
+      kDefaultFrameInterval, BeginFrameArgs::NORMAL));
+  // We don't run any animations on the layer because threaded animations are
+  // disabled.
+  // TODO(khushalsagar): Revisit this when adding support for animations.
+  DCHECK(!layer_tree_->animation_host()->needs_push_properties());
+  client_->UpdateLayerTreeHost();
+
+  current_pipeline_stage_ = FramePipelineStage::UPDATE_LAYERS;
+  LayerList layer_list;
+  if (max_pipeline_stage_for_current_frame_ >=
+      FramePipelineStage::UPDATE_LAYERS) {
+    // Pull updates for all layers from the client.
+    // TODO(khushalsagar): Investigate the data impact from updating all the
+    // layers. See crbug.com/650885.
+    LayerTreeHostCommon::CallFunctionForEveryLayer(
+        layer_tree_.get(),
+        [&layer_list](Layer* layer) { layer_list.push_back(layer); });
+
+    bool content_is_suitable_for_gpu = false;
+    bool layers_updated =
+        layer_tree_->UpdateLayers(layer_list, &content_is_suitable_for_gpu);
+
+    // If pulling layer updates resulted in any content updates, we need to go
+    // till the commit stage.
+    if (layers_updated)
+      max_pipeline_stage_for_current_frame_ = FramePipelineStage::COMMIT;
+  }
+
+  current_pipeline_stage_ = FramePipelineStage::COMMIT;
+  client_->WillCommit();
+
+  if (max_pipeline_stage_for_current_frame_ < current_pipeline_stage_) {
+    // There is nothing to commit so break the swap promises.
+    swap_promise_manager_.BreakSwapPromises(
+        SwapPromise::DidNotSwapReason::COMMIT_NO_UPDATE);
+
+    // For the client, the commit was successful.
+    MainFrameComplete();
+    return;
+  }
+
+  // TODO(khushalsagar): Serialize current state/reset dirty state tracking and
+  // return the result to the bridge instead.
+  std::unique_ptr<CompositorProtoState> compositor_state =
+      base::MakeUnique<CompositorProtoState>();
+  remote_compositor_bridge_->ProcessCompositorStateUpdate(
+      std::move(compositor_state));
+
+  MainFrameComplete();
+
+  // We can not wait for updates dispatched from the client about the state of
+  // drawing or swaps for frames sent. Since these calls can be used by the
+  // LayerTreeHostClient to throttle further frame updates, so dispatch them
+  // right after the update is processed by the bridge.
+  // TODO(khushalsagar): We can not really know what these callbacks end up
+  // being used for. Consider migrating clients to understand/cope with the fact
+  // that there is no actual compositing happening here.
+  task_runner_provider_->MainThreadTaskRunner()->PostTask(
+      FROM_HERE, base::Bind(&LayerTreeHostRemote::DispatchDrawAndSwapCallbacks,
+                            weak_factory_.GetWeakPtr()));
+}
+
+void LayerTreeHostRemote::MainFrameComplete() {
+  DCHECK_EQ(current_pipeline_stage_, FramePipelineStage::COMMIT);
+
+  current_pipeline_stage_ = FramePipelineStage::NONE;
+  max_pipeline_stage_for_current_frame_ = FramePipelineStage::NONE;
+  source_frame_number_++;
+
+  client_->DidCommit();
+  client_->DidBeginMainFrame();
+}
+
+void LayerTreeHostRemote::DispatchDrawAndSwapCallbacks() {
+  client_->DidCommitAndDrawFrame();
+  client_->DidCompleteSwapBuffers();
+}
+
+}  // namespace cc