cc:: Add remote mode to the compositor

cc/trees/remote_channel_impl.h

+// 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.
+
+#ifndef CC_TREES_REMOTE_CHANNEL_IMPL_H_
+#define CC_TREES_REMOTE_CHANNEL_IMPL_H_
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "cc/base/cc_export.h"
+#include "cc/base/completion_event.h"
+#include "cc/trees/channel_impl.h"
+#include "cc/trees/proxy.h"
+#include "cc/trees/proxy_impl.h"
+#include "cc/trees/remote_proto_channel.h"
+
+namespace cc {
+class LayerTreeHost;
+
+namespace proto {
+class CompositorMessage;
+class CompositorMessageToImpl;
+class CompositorMessageToMain;
+}
+
+// The Proxy and ChannelImpl implementation for the remote compositor.
+// The object life cycle and communication across threads is as follows:
+//
+// The RemoteChannelImpl is created by the remote client LayerTreeHost, which
+// initializes the impl side of the compositor.
+//
+//           Main Thread              |               Impl Thread
+//                                    |
+//         Proxy::Start               |
+//               |                    |
+//               |              RemoteChannelImpl
+// ---------------------------------------------------------------------------
+// RemoteChannelImpl::Start()---PostTask---> RemoteChannelImpl::
+//                                                    InitializeImplOnImpl
+//                                                          |
+//                                                   ProxyImpl::Create
+//                                                          |
+//                                                          .
+//                                                          .
+//                                          ProxyImpl::ScheduledActionBegin
+//                                                     OutputSurfaceCreation
+//                                                          |
+//                                         ChannelImpl::RequestNewOutputSurface
+//                                                          |
+// RemoteChannelImpl::                                      |
+//      RequestNewOutputSurface()<----PostTask--------------
+//              .
+//              .
+//              |
+// RemoteChannelImpl::
+//          ~RemoteChannelImpl() ---PostTask---> RemoteChannelImpl::
+//                                                      ShutdownImplOnImpl
+// ----------------------------------------------------------------------------
+//
+// The class is created and destroyed on the main thread but can be safely
+// called from the main or impl thread. It is safe to call RemoteChannelImpl on
+// the impl thread since:
+// 1) The only impl threaded callers of RemoteChannelImpl is the
+// RemoteChannelImpl itself and ProxyImpl which is created and owned by the
+// RemoteChannelImpl.
+// 2) The RemoteChannelImpl blocks the main thread in its dtor to wait for the
+// impl-thread teardown to complete, which ensures that any tasks queued to call
+// it on the impl thread are run before it is destroyed on the main thread.
+//
+// The RemoteChannelImpl receives and processes messages from the remote server
+// compositor on the main thread. The requests from ProxyImpl are received on
+// the impl thread which may be directed to the LayerTreeHost on the client
+// (for instance output surface requests) or sent to the LayerTreeHost on the
+// server. The messages to the server are created on the impl thread and sent
+// using the RemoteProtoChannel on the main thread.
+class CC_EXPORT RemoteChannelImpl : public ChannelImpl,
+                                    public RemoteProtoChannel::ProtoReceiver,
+                                    public Proxy {
+ public:
+  static scoped_ptr<RemoteChannelImpl> Create(
+      LayerTreeHost* layer_tree_host,
+      RemoteProtoChannel* remote_proto_channel,
+      TaskRunnerProvider* task_runner_provider);
+
+  ~RemoteChannelImpl() override;
+
+ protected:
+  RemoteChannelImpl(LayerTreeHost* layer_tree_host,
+                    RemoteProtoChannel* remote_proto_channel,
+                    TaskRunnerProvider* task_runner_provider);
+
+  // virtual for testing.
+  virtual scoped_ptr<ProxyImpl> CreateProxyImpl(
+      ChannelImpl* channel_impl,
+      LayerTreeHost* layer_tree_host,
+      TaskRunnerProvider* task_runner_provider,
+      scoped_ptr<BeginFrameSource> external_begin_frame_source);
+
+ private:
+  struct MainThreadOnly {
+    LayerTreeHost* layer_tree_host;
+    RemoteProtoChannel* remote_proto_channel;
+
+    bool started;
+
+    RendererCapabilities renderer_capabilities;
+
+    MainThreadOnly(LayerTreeHost* layer_tree_host,
+                   RemoteProtoChannel* remote_proto_channel);
+    ~MainThreadOnly();
+  };
+
+  struct CompositorThreadOnly {
+    scoped_ptr<ProxyImpl> proxy_impl;
+    scoped_ptr<base::WeakPtrFactory<ProxyImpl>> proxy_impl_weak_factory;
+
+    CompositorThreadOnly();
+    ~CompositorThreadOnly();
+  };
+
+  // called on main thread.
+  // RemoteProtoChannel::ProtoReceiver implementation.
+  void OnProtoReceived(scoped_ptr<proto::CompositorMessage> proto) override;
+
+  // Proxy implementation
+  void FinishAllRendering() override;
+  bool IsStarted() const override;
+  bool CommitToActiveTree() const override;
+  void SetOutputSurface(OutputSurface* output_surface) override;
+  void ReleaseOutputSurface() override;
+  void SetVisible(bool visible) override;
+  void SetThrottleFrameProduction(bool throttle) override;
+  const RendererCapabilities& GetRendererCapabilities() const override;
+  void SetNeedsAnimate() override;
+  void SetNeedsUpdateLayers() override;
+  void SetNeedsCommit() override;
+  void SetNeedsRedraw(const gfx::Rect& damage_rect) override;
+  void SetNextCommitWaitsForActivation() override;
+  void NotifyInputThrottledUntilCommit() override;
+  void SetDeferCommits(bool defer_commits) override;
+  void MainThreadHasStoppedFlinging() override;
+  bool CommitRequested() const override;
+  bool BeginMainFrameRequested() const override;
+  void Start(scoped_ptr<BeginFrameSource> external_begin_frame_source) override;
+  void Stop() override;
+  bool SupportsImplScrolling() const override;
+  void SetChildrenNeedBeginFrames(bool children_need_begin_frames) override;
+  void SetAuthoritativeVSyncInterval(const base::TimeDelta& interval) override;
+  void UpdateTopControlsState(TopControlsState constraints,
+                              TopControlsState current,
+                              bool animate) override;
+  bool MainFrameWillHappenForTesting() override;
+
+  // Called on impl thread.
+  // ChannelImpl implementation
+  void DidCompleteSwapBuffers() override;
+  void SetRendererCapabilitiesMainCopy(
+      const RendererCapabilities& capabilities) override;
+  void BeginMainFrameNotExpectedSoon() override;
+  void DidCommitAndDrawFrame() override;
+  void SetAnimationEvents(scoped_ptr<AnimationEventsVector> queue) override;
+  void DidLoseOutputSurface() override;
+  void RequestNewOutputSurface() override;
+  void DidInitializeOutputSurface(
+      bool success,
+      const RendererCapabilities& capabilities) override;
+  void DidCompletePageScaleAnimation() override;
+  void PostFrameTimingEventsOnMain(
+      scoped_ptr<FrameTimingTracker::CompositeTimingSet> composite_events,
+      scoped_ptr<FrameTimingTracker::MainFrameTimingSet> main_frame_events)
+      override;
+  void BeginMainFrame(
+      scoped_ptr<BeginMainFrameAndCommitState> begin_main_frame_state) override;
+
+  // called on main thread.

[ericrk, 2016/01/20 22:32:29]

why not move these up to the other "called on main thread" block?

[Khushal, 2016/01/22 01:03:24]

I was trying to write the interface implementations first, followed by the
methods for the class. Is there a preferred style here?

[ericrk, 2016/01/22 18:36:59]

hmm... yeah, that is the style, I guess we don't really have a standard for the
"called on X thread" stuff... so this seems fine.

+  void HandleProto(const proto::CompositorMessageToImpl& proto);
+
+  void InitializeImplOnImpl(CompletionEvent* completion,
+                            LayerTreeHost* layer_tree_host);
+  void ShutdownImplOnImpl(CompletionEvent* completion);
+
+  MainThreadOnly& main();
+  const MainThreadOnly& main() const;
+  CompositorThreadOnly& impl();
+  const CompositorThreadOnly& impl() const;
+
+  base::SingleThreadTaskRunner* MainThreadTaskRunner() const;
+  base::SingleThreadTaskRunner* ImplThreadTaskRunner() const;
+
+  // use accessors instead of these variables directly
+  MainThreadOnly main_thread_vars_unsafe_;
+  CompositorThreadOnly compositor_thread_vars_unsafe_;
+
+  TaskRunnerProvider* task_runner_provider_;
+
+  base::WeakPtr<ProxyImpl> proxy_impl_weak_ptr_;
+
+  DISALLOW_COPY_AND_ASSIGN(RemoteChannelImpl);
+};
+
+}  // namespace cc
+
+#endif  // CC_TREES_REMOTE_CHANNEL_IMPL_H_