1 files changed, 212 insertions, 0 deletions
diff --git a/gfx/layers/PersistentBufferProvider.h b/gfx/layers/PersistentBufferProvider.h
new file mode 100644
index 0000000000..2c6ab6f061
--- /dev/null
+++ b/gfx/layers/PersistentBufferProvider.h
@@ -0,0 +1,212 @@
+/* -*- 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_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/KnowsCompositor.h"
+#include "mozilla/layers/LayersTypes.h"
+#include "mozilla/RefCounted.h"
+#include "mozilla/gfx/Types.h"
+#include "mozilla/Vector.h"
+#include "mozilla/WeakPtr.h"
+
+namespace mozilla {
+
+namespace gfx {
+class SourceSurface;
+class DrawTarget;
+}  // namespace gfx
+
+namespace layers {
+
+class CopyableCanvasLayer;
+class TextureClient;
+
+/**
+ * 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 SupportsWeakPtr {
+ public:
+  MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(PersistentBufferProvider)
+
+  virtual ~PersistentBufferProvider() = default;
+
+  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
+   *                       ReturnDrawTarget.
+   */
+  virtual already_AddRefed<gfx::DrawTarget> BorrowDrawTarget(
+      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. The caller should forget any references to the DrawTarget.
+   */
+  virtual bool ReturnDrawTarget(already_AddRefed<gfx::DrawTarget> aDT) = 0;
+
+  virtual already_AddRefed<gfx::SourceSurface> BorrowSnapshot() = 0;
+
+  virtual void ReturnSnapshot(
+      already_AddRefed<gfx::SourceSurface> aSnapshot) = 0;
+
+  virtual TextureClient* GetTextureClient() { return nullptr; }
+
+  virtual void OnShutdown() {}
+
+  virtual bool SetKnowsCompositor(KnowsCompositor* aKnowsCompositor) {
+    return true;
+  }
+
+  virtual void ClearCachedResources() {}
+
+  /**
+   * Return true if this provider preserves the drawing state (clips,
+   * transforms, etc.) across frames. In practice this means users of the
+   * provider can skip popping all of the clips at the end of the frames and
+   * pushing them back at the beginning of the following frames, which can be
+   * costly (cf. bug 1294351).
+   */
+  virtual bool PreservesDrawingState() const = 0;
+};
+
+class PersistentBufferProviderBasic : public PersistentBufferProvider {
+ public:
+  MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(PersistentBufferProviderBasic,
+                                          override)
+
+  static already_AddRefed<PersistentBufferProviderBasic> Create(
+      gfx::IntSize aSize, gfx::SurfaceFormat aFormat,
+      gfx::BackendType aBackend);
+
+  explicit PersistentBufferProviderBasic(gfx::DrawTarget* aTarget);
+
+  LayersBackend GetType() override { return LayersBackend::LAYERS_BASIC; }
+
+  already_AddRefed<gfx::DrawTarget> BorrowDrawTarget(
+      const gfx::IntRect& aPersistedRect) override;
+
+  bool ReturnDrawTarget(already_AddRefed<gfx::DrawTarget> aDT) override;
+
+  already_AddRefed<gfx::SourceSurface> BorrowSnapshot() override;
+
+  void ReturnSnapshot(already_AddRefed<gfx::SourceSurface> aSnapshot) override;
+
+  bool PreservesDrawingState() const override { return true; }
+
+  void OnShutdown() override { Destroy(); }
+
+ protected:
+  void Destroy();
+
+ private:
+  virtual ~PersistentBufferProviderBasic();
+
+  RefPtr<gfx::DrawTarget> mDrawTarget;
+  RefPtr<gfx::SourceSurface> mSnapshot;
+};
+
+/**
+ * Provides access to a buffer which can be sent to the compositor without
+ * requiring a copy.
+ */
+class PersistentBufferProviderShared : public PersistentBufferProvider,
+                                       public ActiveResource {
+ public:
+  MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(PersistentBufferProviderShared,
+                                          override)
+
+  static already_AddRefed<PersistentBufferProviderShared> Create(
+      gfx::IntSize aSize, gfx::SurfaceFormat aFormat,
+      KnowsCompositor* aKnowsCompositor);
+
+  LayersBackend GetType() override;
+
+  already_AddRefed<gfx::DrawTarget> BorrowDrawTarget(
+      const gfx::IntRect& aPersistedRect) override;
+
+  bool ReturnDrawTarget(already_AddRefed<gfx::DrawTarget> aDT) override;
+
+  already_AddRefed<gfx::SourceSurface> BorrowSnapshot() override;
+
+  void ReturnSnapshot(already_AddRefed<gfx::SourceSurface> aSnapshot) override;
+
+  TextureClient* GetTextureClient() override;
+
+  void NotifyInactive() override;
+
+  void OnShutdown() override { Destroy(); }
+
+  bool SetKnowsCompositor(KnowsCompositor* aKnowsCompositor) override;
+
+  void ClearCachedResources() override;
+
+  bool PreservesDrawingState() const override { return false; }
+
+ protected:
+  PersistentBufferProviderShared(gfx::IntSize aSize, gfx::SurfaceFormat aFormat,
+                                 KnowsCompositor* aKnowsCompositor,
+                                 RefPtr<TextureClient>& aTexture);
+
+  ~PersistentBufferProviderShared();
+
+  TextureClient* GetTexture(const Maybe<uint32_t>& aIndex);
+  bool CheckIndex(uint32_t aIndex) { return aIndex < mTextures.length(); }
+
+  void Destroy();
+
+  gfx::IntSize mSize;
+  gfx::SurfaceFormat mFormat;
+  RefPtr<KnowsCompositor> mKnowsCompositor;
+  // We may need two extra textures if webrender is enabled.
+  static const size_t kMaxTexturesAllowed = 4;
+  Vector<RefPtr<TextureClient>, kMaxTexturesAllowed + 2> mTextures;
+  // Offset of the texture in mTextures that the canvas uses.
+  Maybe<uint32_t> mBack;
+  // Offset of the texture in mTextures that is presented to the compositor.
+  Maybe<uint32_t> mFront;
+  // Offset of the texture in mTextures which texture's readlock is unreliable.
+  // Therefore it should not be used as next back buffer.
+  Maybe<uint32_t> mTextureLockIsUnreliable;
+
+  RefPtr<gfx::DrawTarget> mDrawTarget;
+  RefPtr<gfx::SourceSurface> mSnapshot;
+  RefPtr<gfx::SourceSurface> mPreviousSnapshot;
+  size_t mMaxAllowedTextures = kMaxTexturesAllowed;
+};
+
+struct AutoReturnSnapshot final {
+  PersistentBufferProvider* mBufferProvider;
+  RefPtr<gfx::SourceSurface>* mSnapshot;
+
+  explicit AutoReturnSnapshot(PersistentBufferProvider* aProvider = nullptr)
+      : mBufferProvider(aProvider), mSnapshot(nullptr) {}
+
+  ~AutoReturnSnapshot() {
+    if (mBufferProvider) {
+      mBufferProvider->ReturnSnapshot(mSnapshot ? mSnapshot->forget()
+                                                : nullptr);
+    }
+  }
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif