Initial checkin of the new Mozart compositor.

services/gfx/compositor/graph/snapshot.h

Index: services/gfx/compositor/graph/snapshot.h
diff --git a/services/gfx/compositor/graph/snapshot.h b/services/gfx/compositor/graph/snapshot.h
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+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SERVICES_GFX_COMPOSITOR_GRAPH_SNAPSHOT_H_
+#define SERVICES_GFX_COMPOSITOR_GRAPH_SNAPSHOT_H_
+
+#include <iosfwd>
+#include <memory>
+#include <unordered_set>
+
+#include "base/macros.h"
+#include "mojo/services/geometry/interfaces/geometry.mojom.h"
+#include "mojo/services/gfx/composition/interfaces/scheduling.mojom.h"
+
+namespace compositor {
+
+class SceneDef;
+class RenderFrame;
+
+// Describes a single frame snapshot of the scene graph, sufficient for
+// rendering and hit testing.  When the snapshot is made, all predicated and
+// blocked scene nodes are evaluated to produce a final description of
+// the frame along with its dependencies.
+//
+// The snapshot holds a list of dependencies for the scenes whose state was
+// originally used to produce it.  The snapshot must be invalidated whenever
+// any of these scenes change.  Note that the snapshot will contain a list
+// of dependencies even in the case where a frame could not be produced,
+// in which case the dependencies express the set of scenes which, if updated,
+// might allow composition to be unblocked and make progress on a subsequent
+// frame.
+//
+// Snapshot objects are not thread-safe since they have direct references to
+// the scene graph definition.  However, the snapshot's frame is thread-safe
+// and is intended to be shared by other components.
+class Snapshot {
+ public:
+  ~Snapshot();
+
+  // Returns true if the snapshot is valid.
+  bool valid() const { return valid_; }
+
+  // Gets the frame produced from this snapshot, or null if none.
+  //
+  // This is always null if |valid()| is false but it may be null even
+  // when |valid()| is true if composition was blocked and unable to produce
+  // a frame during the snapshot operation.
+  const std::shared_ptr<RenderFrame>& frame() const { return frame_; }
+
+  // Unconditionally marks the snapshot as invalid.
+  //
+  // Returns true if the snapshot became invalid as a result of this operation,
+  // or false if it was already invalid.
+  bool Invalidate();
+
+  // Invalidates the snapshot if it has a dependency on the specified scene.
+  // When this occurs, the entire list of dependencies is flushed (we no longer
+  // need them) in case the scene in question or its contents are about to
+  // be destroyed.
+  //
+  // Returns true if the snapshot became invalid as a result of this operation,
+  // or false if it was already invalid.
+  bool InvalidateScene(SceneDef* scene_def);
+
+ private:
+  friend class SnapshotBuilder;
+
+  Snapshot();
+
+  std::unordered_set<SceneDef*> dependencies_;
+  std::shared_ptr<RenderFrame> frame_;
+  bool valid_ = true;
+
+  DISALLOW_COPY_AND_ASSIGN(Snapshot);
+};
+
+// Builder for snapshots.
+class SnapshotBuilder {
+ public:
+  // Creates a snapshot builder.
+  //
+  // |block_log|, if not null, the snapshotter will append information to
+  // this stream describing the parts of the scene graph for which
+  // composition was blocked.
+  explicit SnapshotBuilder(std::ostream* block_log);
+  ~SnapshotBuilder();
+
+  // If not null, the snapshotter will append information to this stream
+  // describing the parts of the scene graph for which composition was blocked.
+  std::ostream* block_log() { return block_log_; }
+
+  // Adds a scene dependency to the snapshot.
+  void AddSceneDependency(SceneDef* scene);
+
+  // Builds a snapshot rooted at the specified scene.
+  std::unique_ptr<Snapshot> Build(
+      SceneDef* root_scene,
+      const mojo::Rect& viewport,
+      const mojo::gfx::composition::FrameInfo& frame_info);
+
+ private:
+  std::ostream* const block_log_;
+  std::unique_ptr<Snapshot> snapshot_;
+
+  DISALLOW_COPY_AND_ASSIGN(SnapshotBuilder);
+};
+
+}  // namespace compositor
+
+#endif  // SERVICES_GFX_COMPOSITOR_GRAPH_SNAPSHOT_H_