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// Copyright 2015 Google Inc. All Rights Reserved.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
#include <map>
#include "base/memory/scoped_ptr.h"
#include "base/optional.h"
#include "base/time.h"
#include "cobalt/renderer/submission.h"
namespace cobalt {
namespace browser {
// Combines rendering layers (such as the main, splash screen, and
// debug console). Caches the individual trees as they are produced.
// Re-renders when any tree changes.
class RenderTreeCombiner {
// Layer represents the render layer corresponding to the main web
// module, the splash screen, or the debug console and are used to
// create and submit a combined tree to the RendererModule's
// pipeline. Layers are combined in order of the |z_index| specifed
// at the Layers' creation. The RenderTreeCombiner stores pointers
// to Layers. The Layers are owned by the caller of
// RenderTreeCombiner::CreateLayer.
class Layer {
void Reset() {
render_tree_ = base::nullopt;
receipt_time_ = base::nullopt;
// Submit render tree to the layer, and specify whether the time
// received should be stored.
void Submit(
const base::optional<renderer::Submission>& render_tree_submission);
bool HasRenderTree() { return !!render_tree_; }
// Returns a current submission object that can be passed into a renderer
// for rasterization. If the render tree does not exist, this will
// return a base::nullopt.
base::optional<renderer::Submission> GetCurrentSubmission();
friend class RenderTreeCombiner;
explicit Layer(RenderTreeCombiner* render_tree_combiner = NULL);
// Returns the current submission time for this particular layer. This is
// called by the RenderTreeCombiner on the |timeline_layer_| to determine
// which value to pass in as the submission time for the renderer.
base::optional<base::TimeDelta> CurrentTimeOffset();
RenderTreeCombiner* render_tree_combiner_;
base::optional<renderer::Submission> render_tree_;
base::optional<base::TimeTicks> receipt_time_;
~RenderTreeCombiner() {}
// Create a Layer with a given |z_index|. If a Layer already exists
// at |z_index|, return NULL, and no Layer is created.
scoped_ptr<Layer> CreateLayer(int z_index);
// Returns a current submission object that can be passed into a renderer
// for rasterization. If no layers with render trees exist, this will return
// a base::nullopt.
base::optional<renderer::Submission> GetCurrentSubmission();
// Names a single layer as the one responsible for providing the timeline
// id and configuration to the output combined render tree. Only a single
// layer can be responsible for providing the timeline.
void SetTimelineLayer(Layer* layer);
// Returns true if the specified layer exists in this render tree combiner's
// current list of layers (e.g. |layers_|).
bool OwnsLayer(Layer* layer);
// The layers keyed on their z_index.
std::map<int, Layer*> layers_;
// Removes a layer from |layers_|. Called by the Layer destructor.
void RemoveLayer(const Layer* layer);
// Which layer is currently controlling the receipt time submitted to the
// rasterizer.
RenderTreeCombiner::Layer* timeline_layer_;
} // namespace browser
} // namespace cobalt