Mypal/gfx/layers/composite/TextureHost.h

/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* 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_TEXTUREHOST_H
#define MOZILLA_GFX_TEXTUREHOST_H

#include <stddef.h>                     // for size_t
#include <stdint.h>                     // for uint64_t, uint32_t, uint8_t
#include "gfxTypes.h"
#include "mozilla/Assertions.h"         // for MOZ_ASSERT, etc
#include "mozilla/Attributes.h"         // for override
#include "mozilla/RefPtr.h"             // for RefPtr, already_AddRefed, etc
#include "mozilla/gfx/2D.h"             // for DataSourceSurface
#include "mozilla/gfx/Point.h"          // for IntSize, IntPoint
#include "mozilla/gfx/Types.h"          // for SurfaceFormat, etc
#include "mozilla/layers/Compositor.h"  // for Compositor
#include "mozilla/layers/CompositorTypes.h"  // for TextureFlags, etc
#include "mozilla/layers/LayersTypes.h"  // for LayerRenderState, etc
#include "mozilla/layers/LayersSurfaces.h"
#include "mozilla/mozalloc.h"           // for operator delete
#include "mozilla/UniquePtr.h"          // for UniquePtr
#include "nsCOMPtr.h"                   // for already_AddRefed
#include "nsDebug.h"                    // for NS_RUNTIMEABORT
#include "nsISupportsImpl.h"            // for MOZ_COUNT_CTOR, etc
#include "nsRegion.h"                   // for nsIntRegion
#include "nsTraceRefcnt.h"              // for MOZ_COUNT_CTOR, etc
#include "nscore.h"                     // for nsACString
#include "mozilla/layers/AtomicRefCountedWithFinalize.h"
#include "mozilla/gfx/Rect.h"

namespace mozilla {
namespace ipc {
class Shmem;
} // namespace ipc

namespace layers {

class BufferDescriptor;
class BufferTextureHost;
class Compositor;
class CompositableParentManager;
class ReadLockDescriptor;
class CompositorBridgeParent;
class SurfaceDescriptor;
class HostIPCAllocator;
class ISurfaceAllocator;
class TextureHostOGL;
class TextureReadLock;
class TextureSourceOGL;
class TextureSourceD3D9;
class TextureSourceD3D11;
class TextureSourceBasic;
class DataTextureSource;
class PTextureParent;
class TextureParent;
class WrappingTextureSourceYCbCrBasic;

/**
 * A view on a TextureHost where the texture is internally represented as tiles
 * (contrast with a tiled buffer, where each texture is a tile). For iteration by
 * the texture's buffer host.
 * This is only useful when the underlying surface is too big to fit in one
 * device texture, which forces us to split it in smaller parts.
 * Tiled Compositable is a different thing.
 */
class BigImageIterator
{
public:
  virtual void BeginBigImageIteration() = 0;
  virtual void EndBigImageIteration() {};
  virtual gfx::IntRect GetTileRect() = 0;
  virtual size_t GetTileCount() = 0;
  virtual bool NextTile() = 0;
};

/**
 * TextureSource is the interface for texture objects that can be composited
 * by a given compositor backend. Since the drawing APIs are different
 * between backends, the TextureSource interface is split into different
 * interfaces (TextureSourceOGL, etc.), and TextureSource mostly provide
 * access to these interfaces.
 *
 * This class is used on the compositor side.
 */
class TextureSource: public RefCounted<TextureSource>
{
public:
  MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(TextureSource)

  TextureSource();

  virtual ~TextureSource();

  virtual const char* Name() const = 0;

  /**
   * Should be overridden in order to deallocate the data that is associated
   * with the rendering backend, such as GL textures.
   */
  virtual void DeallocateDeviceData() {}


  /**
   * Return the size of the texture in texels.
   * If this is a tile iterator, GetSize must return the size of the current tile.
   */
  virtual gfx::IntSize GetSize() const = 0;

  /**
   * Return the pixel format of this texture
   */
  virtual gfx::SurfaceFormat GetFormat() const { return gfx::SurfaceFormat::UNKNOWN; }

  /**
   * Cast to a TextureSource for for each backend..
   */
  virtual TextureSourceOGL* AsSourceOGL() {
    gfxCriticalNote << "Failed to cast " << Name() << " into a TextureSourceOGL";
    return nullptr;
  }
  virtual TextureSourceD3D9* AsSourceD3D9() { return nullptr; }
  virtual TextureSourceD3D11* AsSourceD3D11() { return nullptr; }
  virtual TextureSourceBasic* AsSourceBasic() { return nullptr; }
  /**
   * Cast to a DataTextureSurce.
   */
  virtual DataTextureSource* AsDataTextureSource() { return nullptr; }
  virtual WrappingTextureSourceYCbCrBasic* AsWrappingTextureSourceYCbCrBasic() { return nullptr; }

  /**
   * Overload this if the TextureSource supports big textures that don't fit in
   * one device texture and must be tiled internally.
   */
  virtual BigImageIterator* AsBigImageIterator() { return nullptr; }

  virtual void SetCompositor(Compositor* aCompositor) {}

  virtual void Unbind() {}

  void SetNextSibling(TextureSource* aTexture) { mNextSibling = aTexture; }

  TextureSource* GetNextSibling() const { return mNextSibling; }

  /**
   * In some rare cases we currently need to consider a group of textures as one
   * TextureSource, that can be split in sub-TextureSources.
   */
  TextureSource* GetSubSource(int index)
  {
    switch (index) {
      case 0: return this;
      case 1: return GetNextSibling();
      case 2: return GetNextSibling() ? GetNextSibling()->GetNextSibling() : nullptr;
    }
    return nullptr;
  }

  void AddCompositableRef() { ++mCompositableCount; }

  void ReleaseCompositableRef() {
    --mCompositableCount;
    MOZ_ASSERT(mCompositableCount >= 0);
  }

  int NumCompositableRefs() const { return mCompositableCount; }

protected:

  RefPtr<TextureSource> mNextSibling;
  int mCompositableCount;
};

/// Equivalent of a RefPtr<TextureSource>, that calls AddCompositableRef and
/// ReleaseCompositableRef in addition to the usual AddRef and Release.
///
/// The semantoics of these CompositableTextureRefs are important because they
/// are used both as a synchronization/safety mechanism, and as an optimization
/// mechanism. They are also tricky and subtle because we use them in a very
/// implicit way (assigning to a CompositableTextureRef is less visible than
/// explicitly calling a method or whatnot).
/// It is Therefore important to be careful about the way we use this tool.
///
/// CompositableTextureRef is a mechanism that lets us count how many compositables
/// are using a given texture (for TextureSource and TextureHost).
/// We use it to run specific code when a texture is not used anymore, and also
/// we trigger fast paths on some operations when we can see that the texture's
/// CompositableTextureRef counter is equal to 1 (the texture is not shared
/// between compositables).
/// This means that it is important to observe the following rules:
/// * CompositableHosts that receive UseTexture and similar messages *must* store
/// all of the TextureHosts they receive in CompositableTextureRef slots for as
/// long as they may be using them.
/// * CompositableHosts must store each texture in a *single* CompositableTextureRef
/// slot to ensure that the counter properly reflects how many compositables are
/// using the texture.
/// If a compositable needs to hold two references to a given texture (for example
/// to have a pointer to the current texture in a list of textures that may be
/// used), it can hold its extra references with RefPtr or whichever pointer type
/// makes sense.
template<typename T>
class CompositableTextureRef {
public:
  CompositableTextureRef() {}

  explicit CompositableTextureRef(const CompositableTextureRef& aOther)
  {
    *this = aOther;
  }

  explicit CompositableTextureRef(T* aOther)
  {
    *this = aOther;
  }

  ~CompositableTextureRef()
  {
    if (mRef) {
      mRef->ReleaseCompositableRef();
    }
  }

  CompositableTextureRef& operator=(const CompositableTextureRef& aOther)
  {
    if (aOther.get()) {
      aOther->AddCompositableRef();
    }
    if (mRef) {
      mRef->ReleaseCompositableRef();
    }
    mRef = aOther.get();
    return *this;
  }

  CompositableTextureRef& operator=(T* aOther)
  {
    if (aOther) {
      aOther->AddCompositableRef();
    }
    if (mRef) {
      mRef->ReleaseCompositableRef();
    }
    mRef = aOther;
    return *this;
  }

  T* get() const { return mRef; }
  operator T*() const { return mRef; }
  T* operator->() const { return mRef; }
  T& operator*() const { return *mRef; }

private:
  RefPtr<T> mRef;
};

typedef CompositableTextureRef<TextureSource> CompositableTextureSourceRef;
typedef CompositableTextureRef<TextureHost> CompositableTextureHostRef;

/**
 * Interface for TextureSources that can be updated from a DataSourceSurface.
 *
 * All backend should implement at least one DataTextureSource.
 */
class DataTextureSource : public TextureSource
{
public:
  DataTextureSource()
    : mOwner(0)
    , mUpdateSerial(0)
  {}

  virtual const char* Name() const override { return "DataTextureSource"; }

  virtual DataTextureSource* AsDataTextureSource() override { return this; }

  /**
   * Upload a (portion of) surface to the TextureSource.
   *
   * The DataTextureSource doesn't own aSurface, although it owns and manage
   * the device texture it uploads to internally.
   */
  virtual bool Update(gfx::DataSourceSurface* aSurface,
                      nsIntRegion* aDestRegion = nullptr,
                      gfx::IntPoint* aSrcOffset = nullptr) = 0;

  /**
   * A facility to avoid reuploading when it is not necessary.
   * The caller of Update can use GetUpdateSerial to see if the number has changed
   * since last update, and call SetUpdateSerial after each successful update.
   * The caller is responsible for managing the update serial except when the
   * texture data is deallocated in which case the TextureSource should always
   * reset the update serial to zero.
   */
  uint32_t GetUpdateSerial() const { return mUpdateSerial; }
  void SetUpdateSerial(uint32_t aValue) { mUpdateSerial = aValue; }

  // By default at least set the update serial to zero.
  // overloaded versions should do that too.
  virtual void DeallocateDeviceData() override
  {
    SetUpdateSerial(0);
  }

#ifdef DEBUG
  /**
   * Provide read access to the data as a DataSourceSurface.
   *
   * This is expected to be very slow and should be used for mostly debugging.
   * XXX - implement everywhere and make it pure virtual.
   */
  virtual already_AddRefed<gfx::DataSourceSurface> ReadBack() { return nullptr; };
#endif

  void SetOwner(TextureHost* aOwner)
  {
    auto newOwner = (uintptr_t)aOwner;
    if (newOwner != mOwner) {
      mOwner = newOwner;
      SetUpdateSerial(0);
    }
  }

  bool IsOwnedBy(TextureHost* aOwner) const { return mOwner == (uintptr_t)aOwner; }

  bool HasOwner() const { return !IsOwnedBy(nullptr); }

private:
  // We store mOwner as an integer rather than as a pointer to make it clear
  // it is not intended to be dereferenced.
  uintptr_t mOwner;
  uint32_t mUpdateSerial;
};

/**
 * TextureHost is a thin abstraction over texture data that need to be shared
 * between the content process and the compositor process. It is the
 * compositor-side half of a TextureClient/TextureHost pair. A corresponding
 * TextureClient lives on the content-side.
 *
 * TextureHost only knows how to deserialize or synchronize generic image data
 * (SurfaceDescriptor) and provide access to one or more TextureSource objects
 * (these provide the necessary APIs for compositor backends to composite the
 * image).
 *
 * A TextureHost implementation corresponds to one SurfaceDescriptor type, as
 * opposed to TextureSource that corresponds to device textures.
 * This means that for YCbCr planes, even though they are represented as
 * 3 textures internally (3 TextureSources), we use 1 TextureHost and not 3,
 * because the 3 planes are stored in the same buffer of shared memory, before
 * they are uploaded separately.
 *
 * There is always one and only one TextureHost per TextureClient, and the
 * TextureClient/Host pair only owns one buffer of image data through its
 * lifetime. This means that the lifetime of the underlying shared data
 * matches the lifetime of the TextureClient/Host pair. It also means
 * TextureClient/Host do not implement double buffering, which is the
 * reponsibility of the compositable (which would use two Texture pairs).
 *
 * The Lock/Unlock mecanism here mirrors Lock/Unlock in TextureClient.
 *
 */
class TextureHost
  : public AtomicRefCountedWithFinalize<TextureHost>
{
  /**
   * Called once, just before the destructor.
   *
   * Here goes the shut-down code that uses virtual methods.
   * Must only be called by Release().
   */
  void Finalize();

  friend class AtomicRefCountedWithFinalize<TextureHost>;
public:
  explicit TextureHost(TextureFlags aFlags);

protected:
  virtual ~TextureHost();

public:
  /**
   * Factory method.
   */
  static already_AddRefed<TextureHost> Create(
    const SurfaceDescriptor& aDesc,
    ISurfaceAllocator* aDeallocator,
    LayersBackend aBackend,
    TextureFlags aFlags);

  /**
   * Lock the texture host for compositing.
   */
  virtual bool Lock() { return true; }
  /**
   * Unlock the texture host after compositing. Lock() and Unlock() should be
   * called in pair.
   */
  virtual void Unlock() {}

  /**
   * Lock the texture host for compositing without using compositor.
   */
  virtual bool LockWithoutCompositor() { return true; }
  /**
   * Similar to Unlock(), but it should be called with LockWithoutCompositor().
   */
  virtual void UnlockWithoutCompositor() {}

  /**
   * Note that the texture host format can be different from its corresponding
   * texture source's. For example a ShmemTextureHost can have the ycbcr
   * format and produce 3 "alpha" textures sources.
   */
  virtual gfx::SurfaceFormat GetFormat() const = 0;
  /**
   * Return the format used for reading the texture.
   * Apple's YCBCR_422 is R8G8B8X8.
   */
  virtual gfx::SurfaceFormat GetReadFormat() const { return GetFormat(); }

  virtual YUVColorSpace GetYUVColorSpace() const { return YUVColorSpace::UNKNOWN; }

  /**
   * Called during the transaction. The TextureSource may or may not be composited.
   *
   * Note that this is called outside of lock/unlock.
   */
  virtual void PrepareTextureSource(CompositableTextureSourceRef& aTexture) {}

  /**
   * Called at composition time, just before compositing the TextureSource composited.
   *
   * Note that this is called only withing lock/unlock.
   */
  virtual bool BindTextureSource(CompositableTextureSourceRef& aTexture) = 0;

  /**
   * Called when another TextureHost will take over.
   */
  virtual void UnbindTextureSource();

  /**
   * Is called before compositing if the shared data has changed since last
   * composition.
   * This method should be overload in cases like when we need to do a texture
   * upload for example.
   *
   * @param aRegion The region that has been changed, if nil, it means that the
   * entire surface should be updated.
   */
   void Updated(const nsIntRegion* aRegion = nullptr);

  /**
   * Sets this TextureHost's compositor.
   * A TextureHost can change compositor on certain occasions, in particular if
   * it belongs to an async Compositable.
   * aCompositor can be null, in which case the TextureHost must cleanup  all
   * of it's device textures.
   */
  virtual void SetCompositor(Compositor* aCompositor) {}

  /**
   * Should be overridden in order to deallocate the data that is associated
   * with the rendering backend, such as GL textures.
   */
  virtual void DeallocateDeviceData() {}

  /**
   * Should be overridden in order to deallocate the data that is shared with
   * the content side, such as shared memory.
   */
  virtual void DeallocateSharedData() {}

  /**
   * Should be overridden in order to force the TextureHost to drop all references
   * to it's shared data.
   *
   * This is important to ensure the correctness of the deallocation protocol.
   */
  virtual void ForgetSharedData() {}

  virtual gfx::IntSize GetSize() const = 0;

  /**
   * Should be overridden if TextureHost supports crop rect.
   */
  virtual void SetCropRect(nsIntRect aCropRect) {}

  /**
   * Debug facility.
   * XXX - cool kids use Moz2D. See bug 882113.
   */
  virtual already_AddRefed<gfx::DataSourceSurface> GetAsSurface() = 0;

  /**
   * XXX - Flags should only be set at creation time, this will be removed.
   */
  void SetFlags(TextureFlags aFlags) { mFlags = aFlags; }

  /**
   * XXX - Flags should only be set at creation time, this will be removed.
   */
  void AddFlag(TextureFlags aFlag) { mFlags |= aFlag; }

  TextureFlags GetFlags() { return mFlags; }

  /**
   * Allocate and deallocate a TextureParent actor.
   *
   * TextureParent< is an implementation detail of TextureHost that is not
   * exposed to the rest of the code base. CreateIPDLActor and DestroyIPDLActor
   * are for use with the managing IPDL protocols only (so that they can
   * implement AllocPTextureParent and DeallocPTextureParent).
   */
  static PTextureParent* CreateIPDLActor(HostIPCAllocator* aAllocator,
                                         const SurfaceDescriptor& aSharedData,
                                         LayersBackend aLayersBackend,
                                         TextureFlags aFlags,
                                         uint64_t aSerial);
  static bool DestroyIPDLActor(PTextureParent* actor);

  /**
   * Destroy the TextureChild/Parent pair.
   */
  static bool SendDeleteIPDLActor(PTextureParent* actor);

  static void ReceivedDestroy(PTextureParent* actor);

  /**
   * Get the TextureHost corresponding to the actor passed in parameter.
   */
  static TextureHost* AsTextureHost(PTextureParent* actor);

  static uint64_t GetTextureSerial(PTextureParent* actor);

  /**
   * Return a pointer to the IPDLActor.
   *
   * This is to be used with IPDL messages only. Do not store the returned
   * pointer.
   */
  PTextureParent* GetIPDLActor();

  /**
   * Specific to B2G's Composer2D
   * XXX - more doc here
   */
  virtual LayerRenderState GetRenderState()
  {
    // By default we return an empty render state, this should be overridden
    // by the TextureHost implementations that are used on B2G with Composer2D
    return LayerRenderState();
  }

  // If a texture host holds a reference to shmem, it should override this method
  // to forget about the shmem _without_ releasing it.
  virtual void OnShutdown() {}

  // Forget buffer actor. Used only for hacky fix for bug 966446.
  virtual void ForgetBufferActor() {}

  virtual const char *Name() { return "TextureHost"; }
  virtual void PrintInfo(std::stringstream& aStream, const char* aPrefix);

  /**
   * Indicates whether the TextureHost implementation is backed by an
   * in-memory buffer. The consequence of this is that locking the
   * TextureHost does not contend with locking the texture on the client side.
   */
  virtual bool HasIntermediateBuffer() const { return false; }

  void AddCompositableRef() { ++mCompositableCount; }

  void ReleaseCompositableRef()
  {
    --mCompositableCount;
    MOZ_ASSERT(mCompositableCount >= 0);
    if (mCompositableCount == 0) {
      UnbindTextureSource();
      // Send mFwdTransactionId to client side if necessary.
      NotifyNotUsed();
    }
  }

  int NumCompositableRefs() const { return mCompositableCount; }

  void SetLastFwdTransactionId(uint64_t aTransactionId);

  void DeserializeReadLock(const ReadLockDescriptor& aDesc,
                           ISurfaceAllocator* aAllocator);

  TextureReadLock* GetReadLock() { return mReadLock; }

  virtual Compositor* GetCompositor() = 0;

  virtual BufferTextureHost* AsBufferTextureHost() { return nullptr; }

protected:
  void ReadUnlock();

  void RecycleTexture(TextureFlags aFlags);

  virtual void UpdatedInternal(const nsIntRegion *Region) {}

  /**
   * Called when mCompositableCount becomes 0.
   */
  void NotifyNotUsed();

  // for Compositor.
  void CallNotifyNotUsed();

  PTextureParent* mActor;
  RefPtr<TextureReadLock> mReadLock;
  TextureFlags mFlags;
  int mCompositableCount;
  uint64_t mFwdTransactionId;

  friend class Compositor;
  friend class TextureParent;
  friend class TiledLayerBufferComposite;
};

/**
 * TextureHost that wraps a random access buffer such as a Shmem or some raw
 * memory.
 *
 * This TextureHost is backend-independent and the backend-specific bits are
 * in the TextureSource.
 * This class must be inherited to implement GetBuffer and DeallocSharedData
 * (see ShmemTextureHost and MemoryTextureHost)
 *
 * Uploads happen when Lock is called.
 *
 * BufferTextureHost supports YCbCr and flavours of RGBA images (RGBX, A, etc.).
 */
class BufferTextureHost : public TextureHost
{
public:
  BufferTextureHost(const BufferDescriptor& aDescriptor, TextureFlags aFlags);

  ~BufferTextureHost();

  virtual uint8_t* GetBuffer() = 0;

  virtual size_t GetBufferSize() = 0;

  virtual bool Lock() override;

  virtual void Unlock() override;

  virtual void PrepareTextureSource(CompositableTextureSourceRef& aTexture) override;

  virtual bool BindTextureSource(CompositableTextureSourceRef& aTexture) override;

  virtual void UnbindTextureSource() override;

  virtual void DeallocateDeviceData() override;

  virtual void SetCompositor(Compositor* aCompositor) override;

  virtual Compositor* GetCompositor() override { return mCompositor; }

  /**
   * Return the format that is exposed to the compositor when calling
   * BindTextureSource.
   *
   * If the shared format is YCbCr and the compositor does not support it,
   * GetFormat will be RGB32 (even though mFormat is SurfaceFormat::YUV).
   */
  virtual gfx::SurfaceFormat GetFormat() const override;

  virtual YUVColorSpace GetYUVColorSpace() const override;

  virtual gfx::IntSize GetSize() const override { return mSize; }

  virtual already_AddRefed<gfx::DataSourceSurface> GetAsSurface() override;

  virtual bool HasIntermediateBuffer() const override { return mHasIntermediateBuffer; }

  virtual BufferTextureHost* AsBufferTextureHost() override { return this; }

  const BufferDescriptor& GetBufferDescriptor() const { return mDescriptor; }

protected:
  bool Upload(nsIntRegion *aRegion = nullptr);
  bool MaybeUpload(nsIntRegion *aRegion = nullptr);
  bool EnsureWrappingTextureSource();

  virtual void UpdatedInternal(const nsIntRegion* aRegion = nullptr) override;

  BufferDescriptor mDescriptor;
  RefPtr<Compositor> mCompositor;
  RefPtr<DataTextureSource> mFirstSource;
  nsIntRegion mMaybeUpdatedRegion;
  gfx::IntSize mSize;
  gfx::SurfaceFormat mFormat;
  uint32_t mUpdateSerial;
  bool mLocked;
  bool mNeedsFullUpdate;
  bool mHasIntermediateBuffer;

  class DataTextureSourceYCbCrBasic;
};

/**
 * TextureHost that wraps shared memory.
 * the corresponding texture on the client side is ShmemTextureClient.
 * This TextureHost is backend-independent.
 */
class ShmemTextureHost : public BufferTextureHost
{
public:
  ShmemTextureHost(const mozilla::ipc::Shmem& aShmem,
                   const BufferDescriptor& aDesc,
                   ISurfaceAllocator* aDeallocator,
                   TextureFlags aFlags);

protected:
  ~ShmemTextureHost();

public:
  virtual void DeallocateSharedData() override;

  virtual void ForgetSharedData() override;

  virtual uint8_t* GetBuffer() override;

  virtual size_t GetBufferSize() override;

  virtual const char *Name() override { return "ShmemTextureHost"; }

  virtual void OnShutdown() override;

protected:
  UniquePtr<mozilla::ipc::Shmem> mShmem;
  RefPtr<ISurfaceAllocator> mDeallocator;
};

/**
 * TextureHost that wraps raw memory.
 * The corresponding texture on the client side is MemoryTextureClient.
 * Can obviously not be used in a cross process setup.
 * This TextureHost is backend-independent.
 */
class MemoryTextureHost : public BufferTextureHost
{
public:
  MemoryTextureHost(uint8_t* aBuffer,
                    const BufferDescriptor& aDesc,
                    TextureFlags aFlags);

protected:
  ~MemoryTextureHost();

public:
  virtual void DeallocateSharedData() override;

  virtual void ForgetSharedData() override;

  virtual uint8_t* GetBuffer() override;

  virtual size_t GetBufferSize() override;

  virtual const char *Name() override { return "MemoryTextureHost"; }

protected:
  uint8_t* mBuffer;
};

class MOZ_STACK_CLASS AutoLockTextureHost
{
public:
  explicit AutoLockTextureHost(TextureHost* aTexture)
    : mTexture(aTexture)
  {
    mLocked = mTexture ? mTexture->Lock() : false;
  }

  ~AutoLockTextureHost()
  {
    if (mTexture && mLocked) {
      mTexture->Unlock();
    }
  }

  bool Failed() { return mTexture && !mLocked; }

private:
  RefPtr<TextureHost> mTexture;
  bool mLocked;
};

class MOZ_STACK_CLASS AutoLockTextureHostWithoutCompositor
{
public:
  explicit AutoLockTextureHostWithoutCompositor(TextureHost* aTexture)
    : mTexture(aTexture)
  {
    mLocked = mTexture ? mTexture->LockWithoutCompositor() : false;
  }

  ~AutoLockTextureHostWithoutCompositor()
  {
    if (mTexture && mLocked) {
      mTexture->UnlockWithoutCompositor();
    }
  }

  bool Failed() { return mTexture && !mLocked; }

private:
  RefPtr<TextureHost> mTexture;
  bool mLocked;
};

/**
 * This can be used as an offscreen rendering target by the compositor, and
 * subsequently can be used as a source by the compositor.
 */
class CompositingRenderTarget: public TextureSource
{
public:

  explicit CompositingRenderTarget(const gfx::IntPoint& aOrigin)
    : mClearOnBind(false)
    , mOrigin(aOrigin)
    , mHasComplexProjection(false)
  {}
  virtual ~CompositingRenderTarget() {}

  virtual const char* Name() const override { return "CompositingRenderTarget"; }

#ifdef MOZ_DUMP_PAINTING
  virtual already_AddRefed<gfx::DataSourceSurface> Dump(Compositor* aCompositor) { return nullptr; }
#endif

  /**
   * Perform a clear when recycling a non opaque surface.
   * The clear is deferred to when the render target is bound.
   */
  void ClearOnBind() {
    mClearOnBind = true;
  }

  const gfx::IntPoint& GetOrigin() const { return mOrigin; }
  gfx::IntRect GetRect() { return gfx::IntRect(GetOrigin(), GetSize()); }

  /**
   * If a Projection matrix is set, then it is used for rendering to
   * this render target instead of generating one.  If no explicit
   * projection is set, Compositors are expected to generate an
   * orthogonal maaping that maps 0..1 to the full size of the render
   * target.
   */
  bool HasComplexProjection() const { return mHasComplexProjection; }
  void ClearProjection() { mHasComplexProjection = false; }
  void SetProjection(const gfx::Matrix4x4& aNewMatrix, bool aEnableDepthBuffer,
                     float aZNear, float aZFar)
  {
    mProjectionMatrix = aNewMatrix;
    mEnableDepthBuffer = aEnableDepthBuffer;
    mZNear = aZNear;
    mZFar = aZFar;
    mHasComplexProjection = true;
  }
  void GetProjection(gfx::Matrix4x4& aMatrix, bool& aEnableDepth, float& aZNear, float& aZFar)
  {
    MOZ_ASSERT(mHasComplexProjection);
    aMatrix = mProjectionMatrix;
    aEnableDepth = mEnableDepthBuffer;
    aZNear = mZNear;
    aZFar = mZFar;
  }
protected:
  bool mClearOnBind;

private:
  gfx::IntPoint mOrigin;

  gfx::Matrix4x4 mProjectionMatrix;
  float mZNear, mZFar;
  bool mHasComplexProjection;
  bool mEnableDepthBuffer;
};

/**
 * Creates a TextureHost that can be used with any of the existing backends
 * Not all SurfaceDescriptor types are supported
 */
already_AddRefed<TextureHost>
CreateBackendIndependentTextureHost(const SurfaceDescriptor& aDesc,
                                    ISurfaceAllocator* aDeallocator,
                                    TextureFlags aFlags);

} // namespace layers
} // namespace mozilla

#endif