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diff --git a/gfx/layers/ipc/ImageBridgeChild.h b/gfx/layers/ipc/ImageBridgeChild.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MOZILLA_GFX_IMAGEBRIDGECHILD_H
+#define MOZILLA_GFX_IMAGEBRIDGECHILD_H
+
+#include <stddef.h>  // for size_t
+#include <stdint.h>  // for uint32_t, uint64_t
+#include <unordered_map>
+
+#include "mozilla/Attributes.h"  // for override
+#include "mozilla/Atomics.h"
+#include "mozilla/RefPtr.h"            // for already_AddRefed
+#include "mozilla/ipc/SharedMemory.h"  // for SharedMemory, etc
+#include "mozilla/layers/CompositableForwarder.h"
+#include "mozilla/layers/CompositorTypes.h"
+#include "mozilla/layers/PImageBridgeChild.h"
+#include "mozilla/layers/TextureForwarder.h"
+#include "mozilla/Mutex.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/webrender/WebRenderTypes.h"
+#include "nsRegion.h"  // for nsIntRegion
+#include "mozilla/gfx/Rect.h"
+#include "mozilla/ReentrantMonitor.h"  // for ReentrantMonitor, etc
+
+namespace mozilla {
+namespace ipc {
+class Shmem;
+}  // namespace ipc
+
+namespace layers {
+
+class ImageClient;
+class ImageContainer;
+class ImageContainerListener;
+class ImageBridgeParent;
+class CompositableClient;
+struct CompositableTransaction;
+class Image;
+class TextureClient;
+class SynchronousTask;
+
+/**
+ * Returns true if the current thread is the ImageBrdigeChild's thread.
+ *
+ * Can be called from any thread.
+ */
+bool InImageBridgeChildThread();
+
+/**
+ * The ImageBridge protocol is meant to allow ImageContainers to forward images
+ * directly to the compositor thread/process without using the main thread.
+ *
+ * ImageBridgeChild is a CompositableForwarder just like ShadowLayerForwarder.
+ * This means it also does transactions with the compositor thread/process,
+ * except that the transactions are restricted to operations on the
+ * Compositables and cannot contain messages affecting layers directly.
+ *
+ * ImageBridgeChild is also a ISurfaceAllocator. It can be used to allocate or
+ * deallocate data that is shared with the compositor. The main differerence
+ * with other ISurfaceAllocators is that some of its overriden methods can be
+ * invoked from any thread.
+ *
+ * There are three important phases in the ImageBridge protocol. These three
+ * steps can do different things depending if (A) the ImageContainer uses
+ * ImageBridge or (B) it does not use ImageBridge:
+ *
+ * - When an ImageContainer calls its method SetCurrentImage:
+ *   - (A) The image is sent directly to the compositor process through the
+ *   ImageBridge IPDL protocol.
+ *   On the compositor side the image is stored in a global table that
+ *   associates the image with an ID corresponding to the ImageContainer, and a
+ *   composition is triggered.
+ *   - (B) Since it does not have an ImageBridge, the image is not sent yet.
+ *   instead the will be sent to the compositor during the next layer
+ *   transaction (on the main thread).
+ *
+ * - During a Layer transaction:
+ *   - (A) The ImageContainer uses ImageBridge. The image is already available
+ *   to the compositor process because it has been sent with SetCurrentImage.
+ *   Yet, the CompositableHost on the compositor side will needs the ID
+ *   referring to the ImageContainer to access the Image. So during the Swap
+ *   operation that happens in the transaction, we swap the container ID rather
+ *   than the image data.
+ *   - (B) Since the ImageContainer does not use ImageBridge, the image data is
+ *   swaped.
+ *
+ * - During composition:
+ *   - (A) The CompositableHost has an AsyncID, it looks up the ID in the
+ *   global table to see if there is an image. If there is no image, nothing is
+ *   rendered.
+ *   - (B) The CompositableHost has image data rather than an ID (meaning it is
+ *   not using ImageBridge), then it just composites the image data normally.
+ *
+ * This means that there might be a possibility for the ImageBridge to send the
+ * first frame before the first layer transaction that will pass the container
+ * ID to the CompositableHost happens. In this (unlikely) case the layer is not
+ * composited until the layer transaction happens. This means this scenario is
+ * not harmful.
+ *
+ * Since sending an image through imageBridge triggers compositing, the main
+ * thread is not used at all (except for the very first transaction that
+ * provides the CompositableHost with an AsyncID).
+ */
+class ImageBridgeChild final : public PImageBridgeChild,
+                               public CompositableForwarder,
+                               public TextureForwarder {
+  friend class ImageContainer;
+
+  typedef nsTArray<AsyncParentMessageData> AsyncParentMessageArray;
+
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ImageBridgeChild, override);
+
+  TextureForwarder* GetTextureForwarder() override { return this; }
+  LayersIPCActor* GetLayersIPCActor() override { return this; }
+
+  /**
+   * Creates the image bridge with a dedicated thread for ImageBridgeChild.
+   *
+   * We may want to use a specifi thread in the future. In this case, use
+   * CreateWithThread instead.
+   */
+  static void InitSameProcess(uint32_t aNamespace);
+
+  static void InitWithGPUProcess(Endpoint<PImageBridgeChild>&& aEndpoint,
+                                 uint32_t aNamespace);
+  static bool InitForContent(Endpoint<PImageBridgeChild>&& aEndpoint,
+                             uint32_t aNamespace);
+  static bool ReinitForContent(Endpoint<PImageBridgeChild>&& aEndpoint,
+                               uint32_t aNamespace);
+
+  /**
+   * Destroys the image bridge by calling DestroyBridge, and destroys the
+   * ImageBridge's thread.
+   *
+   * If you don't want to destroy the thread, call DestroyBridge directly
+   * instead.
+   */
+  static void ShutDown();
+
+  /**
+   * returns the singleton instance.
+   *
+   * can be called from any thread.
+   */
+  static RefPtr<ImageBridgeChild> GetSingleton();
+
+  static void IdentifyCompositorTextureHost(
+      const TextureFactoryIdentifier& aIdentifier);
+
+  void BeginTransaction();
+  void EndTransaction();
+
+  FixedSizeSmallShmemSectionAllocator* GetTileLockAllocator() override;
+
+  /**
+   * Returns the ImageBridgeChild's thread.
+   *
+   * Can be called from any thread.
+   */
+  nsISerialEventTarget* GetThread() const override;
+
+  base::ProcessId GetParentPid() const override { return OtherPid(); }
+
+  void SyncWithCompositor(
+      const Maybe<uint64_t>& aWindowID = Nothing()) override;
+
+  PTextureChild* AllocPTextureChild(
+      const SurfaceDescriptor& aSharedData, ReadLockDescriptor& aReadLock,
+      const LayersBackend& aLayersBackend, const TextureFlags& aFlags,
+      const uint64_t& aSerial,
+      const wr::MaybeExternalImageId& aExternalImageId);
+
+  bool DeallocPTextureChild(PTextureChild* actor);
+
+  PMediaSystemResourceManagerChild* AllocPMediaSystemResourceManagerChild();
+  bool DeallocPMediaSystemResourceManagerChild(
+      PMediaSystemResourceManagerChild* aActor);
+
+  mozilla::ipc::IPCResult RecvParentAsyncMessages(
+      nsTArray<AsyncParentMessageData>&& aMessages);
+
+  mozilla::ipc::IPCResult RecvDidComposite(
+      nsTArray<ImageCompositeNotification>&& aNotifications);
+
+  mozilla::ipc::IPCResult RecvReportFramesDropped(
+      const CompositableHandle& aHandle, const uint32_t& aFrames);
+
+  // Create an ImageClient from any thread.
+  RefPtr<ImageClient> CreateImageClient(CompositableType aType,
+                                        ImageContainer* aImageContainer);
+
+  // Create an ImageClient from the ImageBridge thread.
+  RefPtr<ImageClient> CreateImageClientNow(CompositableType aType,
+                                           ImageContainer* aImageContainer);
+
+  void UpdateImageClient(RefPtr<ImageContainer> aContainer);
+
+  void UpdateCompositable(const RefPtr<ImageContainer> aContainer,
+                          const RemoteTextureId aTextureId,
+                          const RemoteTextureOwnerId aOwnerId,
+                          const gfx::IntSize aSize, const TextureFlags aFlags,
+                          const RefPtr<FwdTransactionTracker> aTracker);
+
+  /**
+   * Flush all Images sent to CompositableHost.
+   */
+  void FlushAllImages(ImageClient* aClient, ImageContainer* aContainer);
+
+  bool IPCOpen() const override { return mCanSend; }
+
+ private:
+  /**
+   * This must be called by the static function DeleteImageBridgeSync defined
+   * in ImageBridgeChild.cpp ONLY.
+   */
+  virtual ~ImageBridgeChild();
+
+  // Helpers for dispatching.
+  void CreateImageClientSync(SynchronousTask* aTask,
+                             RefPtr<ImageClient>* result,
+                             CompositableType aType,
+                             ImageContainer* aImageContainer);
+
+  void FlushAllImagesSync(SynchronousTask* aTask, ImageClient* aClient,
+                          ImageContainer* aContainer);
+
+  void ProxyAllocShmemNow(SynchronousTask* aTask, size_t aSize,
+                          mozilla::ipc::Shmem* aShmem, bool aUnsafe,
+                          bool* aSuccess);
+  void ProxyDeallocShmemNow(SynchronousTask* aTask, mozilla::ipc::Shmem* aShmem,
+                            bool* aResult);
+
+  void UpdateTextureFactoryIdentifier(
+      const TextureFactoryIdentifier& aIdentifier);
+
+ public:
+  // CompositableForwarder
+
+  void Connect(CompositableClient* aCompositable,
+               ImageContainer* aImageContainer) override;
+
+  bool UsesImageBridge() const override { return true; }
+
+  /**
+   * See CompositableForwarder::UseTextures
+   */
+  void UseTextures(CompositableClient* aCompositable,
+                   const nsTArray<TimedTextureClient>& aTextures) override;
+
+  void UseRemoteTexture(CompositableClient* aCompositable,
+                        const RemoteTextureId aTextureId,
+                        const RemoteTextureOwnerId aOwnerId,
+                        const gfx::IntSize aSize, const TextureFlags aFlags,
+                        const RefPtr<FwdTransactionTracker>& aTracker) override;
+
+  void ReleaseCompositable(const CompositableHandle& aHandle) override;
+
+  void ForgetImageContainer(const CompositableHandle& aHandle);
+
+  /**
+   * Hold TextureClient ref until end of usage on host side if
+   * TextureFlags::RECYCLE is set. Host side's usage is checked via
+   * CompositableRef.
+   */
+  void HoldUntilCompositableRefReleasedIfNecessary(TextureClient* aClient);
+
+  /**
+   * Notify id of Texture When host side end its use. Transaction id is used to
+   * make sure if there is no newer usage.
+   */
+  void NotifyNotUsed(uint64_t aTextureId, uint64_t aFwdTransactionId);
+
+  void CancelWaitForNotifyNotUsed(uint64_t aTextureId) override;
+
+  bool DestroyInTransaction(PTextureChild* aTexture) override;
+  bool DestroyInTransaction(const CompositableHandle& aHandle);
+
+  void RemoveTextureFromCompositable(CompositableClient* aCompositable,
+                                     TextureClient* aTexture) override;
+
+  // ISurfaceAllocator
+
+  /**
+   * See ISurfaceAllocator.h
+   * Can be used from any thread.
+   * If used outside the ImageBridgeChild thread, it will proxy a synchronous
+   * call on the ImageBridgeChild thread.
+   */
+  bool AllocUnsafeShmem(size_t aSize, mozilla::ipc::Shmem* aShmem) override;
+  bool AllocShmem(size_t aSize, mozilla::ipc::Shmem* aShmem) override;
+
+  /**
+   * See ISurfaceAllocator.h
+   * Can be used from any thread.
+   * If used outside the ImageBridgeChild thread, it will proxy a synchronous
+   * call on the ImageBridgeChild thread.
+   */
+  bool DeallocShmem(mozilla::ipc::Shmem& aShmem) override;
+
+  PTextureChild* CreateTexture(
+      const SurfaceDescriptor& aSharedData, ReadLockDescriptor&& aReadLock,
+      LayersBackend aLayersBackend, TextureFlags aFlags,
+      const dom::ContentParentId& aContentId, uint64_t aSerial,
+      wr::MaybeExternalImageId& aExternalImageId) override;
+
+  bool IsSameProcess() const override;
+
+  FwdTransactionCounter& GetFwdTransactionCounter() override {
+    return mFwdTransactionCounter;
+  }
+
+  bool InForwarderThread() override { return InImageBridgeChildThread(); }
+
+  void HandleFatalError(const char* aMsg) override;
+
+  wr::MaybeExternalImageId GetNextExternalImageId() override;
+
+ protected:
+  explicit ImageBridgeChild(uint32_t aNamespace);
+  bool DispatchAllocShmemInternal(size_t aSize, Shmem* aShmem, bool aUnsafe);
+
+  void Bind(Endpoint<PImageBridgeChild>&& aEndpoint);
+  void BindSameProcess(RefPtr<ImageBridgeParent> aParent);
+
+  void SendImageBridgeThreadId();
+
+  void WillShutdown();
+  void ShutdownStep1(SynchronousTask* aTask);
+  void ShutdownStep2(SynchronousTask* aTask);
+  void MarkShutDown();
+
+  void ActorDestroy(ActorDestroyReason aWhy) override;
+
+  bool CanSend() const;
+  bool CanPostTask() const;
+
+  static void ShutdownSingleton();
+
+ private:
+  uint32_t mNamespace;
+
+  CompositableTransaction* mTxn;
+  UniquePtr<FixedSizeSmallShmemSectionAllocator> mSectionAllocator;
+
+  mozilla::Atomic<bool> mCanSend;
+  mozilla::Atomic<bool> mDestroyed;
+
+  /**
+   * Transaction id of CompositableForwarder.
+   * It is incrementaed by UpdateFwdTransactionId() in each BeginTransaction()
+   * call.
+   */
+  FwdTransactionCounter mFwdTransactionCounter;
+
+  /**
+   * Hold TextureClients refs until end of their usages on host side.
+   * It defer calling of TextureClient recycle callback.
+   */
+  std::unordered_map<uint64_t, RefPtr<TextureClient>>
+      mTexturesWaitingNotifyNotUsed;
+
+  /**
+   * Mapping from async compositable IDs to image containers.
+   */
+  Mutex mContainerMapLock MOZ_UNANNOTATED;
+  std::unordered_map<uint64_t, RefPtr<ImageContainerListener>>
+      mImageContainerListeners;
+  RefPtr<ImageContainerListener> FindListener(
+      const CompositableHandle& aHandle);
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif