author Lee Salzman <>
Thu, 18 Jul 2019 21:44:57 +0000
changeset 541453 b5b868d520a2ee6043adaddffb893bae932c24b3
parent 529755 9813ce146bc725dd83e8ff6f41bfc36dd17d935b
permissions -rw-r--r--
Bug 1563133 - limit GlyphBuffer capacity. r=jfkthame a=abillings Differential Revision:

/* -*- 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 */

#ifndef mozilla_layers_ShadowLayers_h
#define mozilla_layers_ShadowLayers_h 1

#include <stddef.h>  // for size_t
#include <stdint.h>  // for uint64_t
#include "gfxTypes.h"
#include "mozilla/Attributes.h"  // for override
#include "mozilla/gfx/Rect.h"
#include "mozilla/WidgetUtils.h"             // for ScreenRotation
#include "mozilla/ipc/SharedMemory.h"        // for SharedMemory, etc
#include "mozilla/HalScreenConfiguration.h"  // for ScreenOrientation
#include "mozilla/layers/CompositableForwarder.h"
#include "mozilla/layers/FocusTarget.h"
#include "mozilla/layers/LayersTypes.h"
#include "mozilla/layers/TextureForwarder.h"
#include "mozilla/layers/CompositorTypes.h"  // for OpenMode, etc
#include "mozilla/layers/CompositorBridgeChild.h"
#include "nsCOMPtr.h"                // for already_AddRefed
#include "nsRegion.h"                // for nsIntRegion
#include "nsTArrayForwardDeclare.h"  // for InfallibleTArray
#include "nsIWidget.h"
#include <vector>

namespace mozilla {
namespace layers {

class ClientLayerManager;
class CompositorBridgeChild;
class FixedSizeSmallShmemSectionAllocator;
class ImageContainer;
class Layer;
class PLayerTransactionChild;
class LayerTransactionChild;
class ShadowableLayer;
class SurfaceDescriptor;
class TextureClient;
class ThebesBuffer;
class ThebesBufferData;
class Transaction;

 * We want to share layer trees across thread contexts and address
 * spaces for several reasons; chief among them
 *  - a parent process can paint a child process's layer tree while
 *    the child process is blocked, say on content script.  This is
 *    important on mobile devices where UI responsiveness is key.
 *  - a dedicated "compositor" process can asynchronously (wrt the
 *    browser process) composite and animate layer trees, allowing a
 *    form of pipeline parallelism between compositor/browser/content
 *  - a dedicated "compositor" process can take all responsibility for
 *    accessing the GPU, which is desirable on systems with
 *    buggy/leaky drivers because the compositor process can die while
 *    browser and content live on (and failover mechanisms can be
 *    installed to quickly bring up a replacement compositor)
 * The Layers model has a crisply defined API, which makes it easy to
 * safely "share" layer trees.  The ShadowLayers API extends Layers to
 * allow a remote, parent process to access a child process's layer
 * tree.
 * ShadowLayerForwarder publishes a child context's layer tree to a
 * parent context.  This comprises recording layer-tree modifications
 * into atomic transactions and pushing them over IPC.
 * LayerManagerComposite grafts layer subtrees published by child-context
 * ShadowLayerForwarder(s) into a parent-context layer tree.
 * (Advanced note: because our process tree may have a height >2, a
 * non-leaf subprocess may both receive updates from child processes
 * and publish them to parent processes.  Put another way,
 * LayerManagers may be both LayerManagerComposites and
 * ShadowLayerForwarders.)
 * There are only shadow types for layers that have different shadow
 * vs. not-shadow behavior.  ColorLayers and ContainerLayers behave
 * the same way in both regimes (so far).
 * The mecanism to shadow the layer tree on the compositor through IPC works as
 * follows:
 * The layer tree is managed on the content thread, and shadowed in the
 * compositor thread. The shadow layer tree is only kept in sync with whatever
 * happens in the content thread. To do this we use IPDL protocols. IPDL is a
 * domain specific language that describes how two processes or thread should
 * communicate. C++ code is generated from .ipdl files to implement the message
 * passing, synchronization and serialization logic. To use the generated code
 * we implement classes that inherit the generated IPDL actor. the ipdl actors
 * of a protocol PX are PXChild or PXParent (the generated class), and we
 * conventionally implement XChild and XParent. The Parent side of the protocol
 * is the one that lives on the compositor thread. Think of IPDL actors as
 * endpoints of communication. they are useful to send messages and also to
 * dispatch the message to the right actor on the other side. One nice property
 * of an IPDL actor is that when an actor, say PXChild is sent in a message, the
 * PXParent comes out in the other side. we use this property a lot to dispatch
 * messages to the right layers and compositable, each of which have their own
 * ipdl actor on both side.
 * Most of the synchronization logic happens in layer transactions and
 * compositable transactions.
 * A transaction is a set of changes to the layers and/or the compositables
 * that are sent and applied together to the compositor thread to keep the
 * LayerComposite in a coherent state.
 * Layer transactions maintain the shape of the shadow layer tree, and
 * synchronize the texture data held by compositables. Layer transactions
 * are always between the content thread and the compositor thread.
 * Compositable transactions are subset of a layer transaction with which only
 * compositables and textures can be manipulated, and does not always originate
 * from the content thread. (See CompositableForwarder.h and ImageBridgeChild.h)

class ShadowLayerForwarder final : public LayersIPCActor,
                                   public CompositableForwarder,
                                   public LegacySurfaceDescriptorAllocator {
  friend class ClientLayerManager;

  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ShadowLayerForwarder, override);

   * Setup the IPDL actor for aCompositable to be part of layers
   * transactions.
  void Connect(CompositableClient* aCompositable,
               ImageContainer* aImageContainer) override;

   * Adds an edit in the layers transaction in order to attach
   * the corresponding compositable and layer on the compositor side.
   * Connect must have been called on aCompositable beforehand.
  void Attach(CompositableClient* aCompositable, ShadowableLayer* aLayer);

   * Adds an edit in the transaction in order to attach a Compositable that
   * is not managed by this ShadowLayerForwarder (for example, by ImageBridge
   * in the case of async-video).
   * Since the compositable is not managed by this forwarder, we can't use
   * the compositable or it's IPDL actor here, so we use an ID instead, that
   * is matched on the compositor side.
  void AttachAsyncCompositable(const CompositableHandle& aHandle,
                               ShadowableLayer* aLayer);

   * Begin recording a transaction to be forwarded atomically to a
   * LayerManagerComposite.
  void BeginTransaction(const gfx::IntRect& aTargetBounds,
                        ScreenRotation aRotation,
                        hal::ScreenOrientation aOrientation);

   * The following methods may only be called after BeginTransaction()
   * but before EndTransaction().  They mirror the LayerManager
   * interface in Layers.h.

   * Notify the shadow manager that a new, "real" layer has been
   * created, and a corresponding shadow layer should be created in
   * the compositing process.
  void CreatedPaintedLayer(ShadowableLayer* aThebes);
  void CreatedContainerLayer(ShadowableLayer* aContainer);
  void CreatedImageLayer(ShadowableLayer* aImage);
  void CreatedColorLayer(ShadowableLayer* aColor);
  void CreatedCanvasLayer(ShadowableLayer* aCanvas);
  void CreatedRefLayer(ShadowableLayer* aRef);

   * At least one attribute of |aMutant| has changed, and |aMutant|
   * needs to sync to its shadow layer.  This initial implementation
   * forwards all attributes when any of the appropriate attribute
   * set is mutated.
  void Mutated(ShadowableLayer* aMutant);
  void MutatedSimple(ShadowableLayer* aMutant);

  void SetRoot(ShadowableLayer* aRoot);
   * Insert |aChild| after |aAfter| in |aContainer|.  |aAfter| can be
   * nullptr to indicated that |aChild| should be appended to the end of
   * |aContainer|'s child list.
  void InsertAfter(ShadowableLayer* aContainer, ShadowableLayer* aChild,
                   ShadowableLayer* aAfter = nullptr);
  void RemoveChild(ShadowableLayer* aContainer, ShadowableLayer* aChild);
  void RepositionChild(ShadowableLayer* aContainer, ShadowableLayer* aChild,
                       ShadowableLayer* aAfter = nullptr);

   * Set aMaskLayer as the mask on aLayer.
   * Note that only image layers are properly supported
   * LayerTransactionParent::UpdateMask and accompanying ipdl
   * will need changing to update properties for other kinds
   * of mask layer.
  void SetMask(ShadowableLayer* aLayer, ShadowableLayer* aMaskLayer);

   * See CompositableForwarder::UseTiledLayerBuffer
  void UseTiledLayerBuffer(
      CompositableClient* aCompositable,
      const SurfaceDescriptorTiles& aTileLayerDescriptor) override;

  void ReleaseCompositable(const CompositableHandle& aHandle) override;
  bool DestroyInTransaction(PTextureChild* aTexture) override;
  bool DestroyInTransaction(const CompositableHandle& aHandle);

  void RemoveTextureFromCompositable(
      CompositableClient* aCompositable, TextureClient* aTexture,
      const Maybe<wr::RenderRoot>& aRenderRoot) override;

   * Communicate to the compositor that aRegion in the texture identified by
   * aLayer and aIdentifier has been updated to aThebesBuffer.
  void UpdateTextureRegion(CompositableClient* aCompositable,
                           const ThebesBufferData& aThebesBufferData,
                           const nsIntRegion& aUpdatedRegion) override;

   * See CompositableForwarder::UseTextures
  void UseTextures(CompositableClient* aCompositable,
                   const nsTArray<TimedTextureClient>& aTextures,
                   const Maybe<wr::RenderRoot>& aRenderRoot) override;
  void UseComponentAlphaTextures(CompositableClient* aCompositable,
                                 TextureClient* aClientOnBlack,
                                 TextureClient* aClientOnWhite) override;

   * Used for debugging to tell the compositor how long this frame took to
   * paint.
  void SendPaintTime(TransactionId aId, TimeDuration aPaintTime);

   * End the current transaction and forward it to LayerManagerComposite.
   * |aReplies| are directions from the LayerManagerComposite to the
   * caller of EndTransaction().
  bool EndTransaction(const nsIntRegion& aRegionToClear, TransactionId aId,
                      bool aScheduleComposite, uint32_t aPaintSequenceNumber,
                      bool aIsRepeatTransaction,
                      const mozilla::VsyncId& aVsyncId,
                      const mozilla::TimeStamp& aVsyncTime,
                      const mozilla::TimeStamp& aRefreshStart,
                      const mozilla::TimeStamp& aTransactionStart,
                      bool aContainsSVG, const nsCString& aURL, bool* aSent,
                      const InfallibleTArray<CompositionPayload>& aPayload =

   * Set an actor through which layer updates will be pushed.
  void SetShadowManager(PLayerTransactionChild* aShadowManager);

   * Layout calls here to cache current plugin widget configuration
   * data. We ship this across with the rest of the layer updates when
   * we update. Chrome handles applying these changes.
  void StorePluginWidgetConfigurations(
      const nsTArray<nsIWidget::Configuration>& aConfigurations);

  void StopReceiveAsyncParentMessge();

  void ClearCachedResources();

  void ScheduleComposite();

   * True if this is forwarding to a LayerManagerComposite.
  bool HasShadowManager() const { return !!mShadowManager; }
  LayerTransactionChild* GetShadowManager() const {
    return mShadowManager.get();

  // Send a synchronous message asking the LayerTransactionParent in the
  // compositor to shutdown.
  void SynchronouslyShutdown();

  virtual void WindowOverlayChanged() { mWindowOverlayChanged = true; }

   * The following Alloc/Open/Destroy interfaces abstract over the
   * details of working with surfaces that are shared across
   * processes.  They provide the glue between C++ Layers and the
   * LayerComposite IPC system.
   * The basic lifecycle is
   *  - a Layer needs a buffer.  Its ShadowableLayer subclass calls
   *    AllocBuffer(), then calls one of the Created*Buffer() methods
   *    above to transfer the (temporary) front buffer to its
   *    LayerComposite in the other process.  The Layer needs a
   *    gfxASurface to paint, so the ShadowableLayer uses
   *    OpenDescriptor(backBuffer) to get that surface, and hands it
   *    out to the Layer.
   * - a Layer has painted new pixels.  Its ShadowableLayer calls one
   *   of the Painted*Buffer() methods above with the back buffer
   *   descriptor.  This notification is forwarded to the LayerComposite,
   *   which uses OpenDescriptor() to access the newly-painted pixels.
   *   The LayerComposite then updates its front buffer in a Layer- and
   *   platform-dependent way, and sends a surface descriptor back to
   *   the ShadowableLayer that becomes its new back back buffer.
   * - a Layer wants to destroy its buffers.  Its ShadowableLayer
   *   calls Destroyed*Buffer(), which gives up control of the back
   *   buffer descriptor.  The actual back buffer surface is then
   *   destroyed using DestroySharedSurface() just before notifying
   *   the parent process.  When the parent process is notified, the
   *   LayerComposite also calls DestroySharedSurface() on its front
   *   buffer, and the double-buffer pair is gone.

  bool IPCOpen() const override;

   * Construct a shadow of |aLayer| on the "other side", at the
   * LayerManagerComposite.
  LayerHandle ConstructShadowFor(ShadowableLayer* aLayer);

   * Flag the next paint as the first for a document.
  void SetIsFirstPaint() { mIsFirstPaint = true; }
  bool GetIsFirstPaint() const { return mIsFirstPaint; }

   * Set the current focus target to be sent with the next paint.
  void SetFocusTarget(const FocusTarget& aFocusTarget) {
    mFocusTarget = aFocusTarget;

  void SetLayersObserverEpoch(LayersObserverEpoch aEpoch);

  static void PlatformSyncBeforeUpdate();

  bool AllocSurfaceDescriptor(const gfx::IntSize& aSize,
                              gfxContentType aContent,
                              SurfaceDescriptor* aBuffer) override;

  bool AllocSurfaceDescriptorWithCaps(const gfx::IntSize& aSize,
                                      gfxContentType aContent, uint32_t aCaps,
                                      SurfaceDescriptor* aBuffer) override;

  void DestroySurfaceDescriptor(SurfaceDescriptor* aSurface) override;

  void UpdateFwdTransactionId() override;
  uint64_t GetFwdTransactionId() override;

  void UpdateTextureLocks();
  void SyncTextures(const nsTArray<uint64_t>& aSerials);

  void ReleaseLayer(const LayerHandle& aHandle);

  bool InForwarderThread() override { return NS_IsMainThread(); }

  PaintTiming& GetPaintTiming() { return mPaintTiming; }

  ShadowLayerForwarder* AsLayerForwarder() override { return this; }

  // Returns true if aSurface wraps a Shmem.
  static bool IsShmem(SurfaceDescriptor* aSurface);

  void SyncWithCompositor() override;

  TextureForwarder* GetTextureForwarder() override {
    return GetCompositorBridgeChild();
  LayersIPCActor* GetLayersIPCActor() override { return this; }

  ActiveResourceTracker* GetActiveResourceTracker() override {
    return mActiveResourceTracker.get();

  CompositorBridgeChild* GetCompositorBridgeChild();

  nsIEventTarget* GetEventTarget() { return mEventTarget; };

  bool IsThreadSafe() const override { return false; }

  RefPtr<KnowsCompositor> GetForMedia() override;

  virtual ~ShadowLayerForwarder();

  explicit ShadowLayerForwarder(ClientLayerManager* aClientLayerManager);

#ifdef DEBUG
  void CheckSurfaceDescriptor(const SurfaceDescriptor* aDescriptor) const;
  void CheckSurfaceDescriptor(const SurfaceDescriptor* aDescriptor) const {}

  RefPtr<CompositableClient> FindCompositable(
      const CompositableHandle& aHandle);

  bool InWorkerThread();

  RefPtr<LayerTransactionChild> mShadowManager;
  RefPtr<CompositorBridgeChild> mCompositorBridgeChild;

  ClientLayerManager* mClientLayerManager;
  Transaction* mTxn;
  MessageLoop* mMessageLoop;
  DiagnosticTypes mDiagnosticTypes;
  bool mIsFirstPaint;
  FocusTarget mFocusTarget;
  bool mWindowOverlayChanged;
  InfallibleTArray<PluginWindowData> mPluginWindowData;
  UniquePtr<ActiveResourceTracker> mActiveResourceTracker;
  uint64_t mNextLayerHandle;
  nsDataHashtable<nsUint64HashKey, CompositableClient*> mCompositables;
  PaintTiming mPaintTiming;
   * ShadowLayerForwarder might dispatch tasks to main while puppet widget and
   * browserChild don't exist anymore; therefore we hold the event target since
   * its lifecycle is independent of these objects.
  nsCOMPtr<nsIEventTarget> mEventTarget;

class CompositableClient;

 * A ShadowableLayer is a Layer can be shared with a parent context
 * through a ShadowLayerForwarder.  A ShadowableLayer maps to a
 * Shadow*Layer in a parent context.
 * Note that ShadowLayers can themselves be ShadowableLayers.
class ShadowableLayer {
  virtual ~ShadowableLayer();

  virtual Layer* AsLayer() = 0;

   * True if this layer has a shadow in a parent process.
  bool HasShadow() { return mShadow.IsValid(); }

   * Return the IPC handle to a Shadow*Layer referring to this if one
   * exists, nullptr if not.
  const LayerHandle& GetShadow() { return mShadow; }

  void SetShadow(ShadowLayerForwarder* aForwarder, const LayerHandle& aShadow) {
    MOZ_ASSERT(!mShadow, "can't have two shadows (yet)");
    mForwarder = aForwarder;
    mShadow = aShadow;

  virtual CompositableClient* GetCompositableClient() { return nullptr; }

  ShadowableLayer() {}

  RefPtr<ShadowLayerForwarder> mForwarder;
  LayerHandle mShadow;

}  // namespace layers
}  // namespace mozilla

#endif  // ifndef mozilla_layers_ShadowLayers_h