text: /* -*- 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_PersistentBUFFERPROVIDER_H
  #define MOZILLA_GFX_PersistentBUFFERPROVIDER_H
  
  #include "mozilla/Assertions.h"         // for MOZ_ASSERT, etc
  #include "mozilla/RefPtr.h"             // for RefPtr, already_AddRefed, etc
  #include "mozilla/layers/LayersTypes.h"
  #include "mozilla/layers/CompositableForwarder.h"
  #include "mozilla/gfx/Types.h"
  
  namespace mozilla {
  namespace layers {
  
  class CopyableCanvasLayer;
  
  /**
   * A PersistentBufferProvider is for users which require the temporary use of
   * a DrawTarget to draw into. When they're done drawing they return the
   * DrawTarget, when they later need to continue drawing they get a DrawTarget
   * from the provider again, the provider will guarantee the contents of the
   * previously returned DrawTarget is persisted into the one newly returned.
   */
  class PersistentBufferProvider : public RefCounted<PersistentBufferProvider>
  {
  public:
    MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(PersistentBufferProvider)
  
    virtual ~PersistentBufferProvider() { }
  
    virtual LayersBackend GetType() { return LayersBackend::LAYERS_NONE; }
  
    /**
     * Get a DrawTarget from the PersistentBufferProvider.
     *
     * \param aPersistedRect This indicates the area of the DrawTarget that needs
     *                       to have remained the same since the call to
     *                       ReturnAndUseDT.
     */
    virtual gfx::DrawTarget* GetDT(const gfx::IntRect& aPersistedRect) = 0;
    /**
     * Return a DrawTarget to the PersistentBufferProvider and indicate the
     * contents of this DrawTarget is to be considered current by the
     * BufferProvider
     */
    virtual bool ReturnAndUseDT(gfx::DrawTarget* aDT) = 0;
  
    virtual already_AddRefed<gfx::SourceSurface> GetSnapshot() = 0;
  protected:
  };
  
  class PersistentBufferProviderBasic : public PersistentBufferProvider
  {
  public:
    MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(PersistentBufferProviderBasic)
  
    PersistentBufferProviderBasic(gfx::IntSize aSize, gfx::SurfaceFormat aFormat,
                                  gfx::BackendType aBackend);
    explicit PersistentBufferProviderBasic(gfx::DrawTarget* aTarget) : mDrawTarget(aTarget) {}
  
    bool IsValid() { return !!mDrawTarget; }
    virtual LayersBackend GetType() { return LayersBackend::LAYERS_BASIC; }
    gfx::DrawTarget* GetDT(const gfx::IntRect& aPersistedRect) { return mDrawTarget; }
    bool ReturnAndUseDT(gfx::DrawTarget* aDT) { MOZ_ASSERT(mDrawTarget == aDT); return true; }
    virtual already_AddRefed<gfx::SourceSurface> GetSnapshot() { return mDrawTarget->Snapshot(); }
  private:
    RefPtr<gfx::DrawTarget> mDrawTarget;
  };
  
  } // namespace layers
  } // namespace mozilla
  
  #endif
  