Implement HitTestAggregator

components/viz/service/hit_test/hit_test_aggregator.h

Index: components/viz/service/hit_test/hit_test_aggregator.h
diff --git a/components/viz/service/hit_test/hit_test_aggregator.h b/components/viz/service/hit_test/hit_test_aggregator.h
new file mode 100644
index 0000000000000000000000000000000000000000..2977c37a76a317a87a393555375b15eacb48eace
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+++ b/components/viz/service/hit_test/hit_test_aggregator.h
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+// Copyright 2017 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 COMPONENTS_VIZ_SERVICE_HIT_TEST_HIT_TEST_AGGREGATOR_H_
+#define COMPONENTS_VIZ_SERVICE_HIT_TEST_HIT_TEST_AGGREGATOR_H_
+
+#include "cc/surfaces/surface_observer.h"
+#include "components/viz/common/hit_test/aggregated_hit_test_region.h"
+#include "components/viz/common/surfaces/surface_id.h"
+#include "components/viz/service/viz_service_export.h"
+#include "services/viz/hit_test/public/interfaces/hit_test_region_list.mojom.h"
+
+namespace viz {
+
+// HitTestAggregator collects HitTestRegionList objects from surfaces and
+// aggregates them into a DisplayHitTesData structue made available in
+// shared memory to enable efficient hit testing across processes.
+//
+// This is intended to be created in the viz or GPU process. For mus+ash this
+// will be true after the mus process split.
+class VIZ_SERVICE_EXPORT HitTestAggregator : public cc::SurfaceObserver {
+ public:
+  HitTestAggregator();
+  ~HitTestAggregator();
+
+  // Called when HitTestRegionList is submitted along with every call
+  // to SubmitCompositorFrame.  This is collected in pending_ until
+  // surfaces are aggregated and put on the display.
+  void SubmitHitTestRegionList(
+      mojom::HitTestRegionListPtr hit_test_region_list);
+
+  // Called after surfaces have been aggregated into the DisplayFrame.
+  // In this call HitTestRegionList structures received from active surfaces
+  // are aggregated into the HitTestRegionList structure in
+  // shared memory used for event targetting.
+  void Aggregate(SurfaceId display_surface_id);
+
+  // Performs the work of Aggregate by creating a PostTask so that
+  // the work is not directly on the call.
+  void PostTaskAggregate(SurfaceId display_surface_id);
+
+  // Called at BeginFrame. Swaps buffers in shared memory.
+  void Swap();
+
+ protected:
+  // cc::SurfaceObserver:
+  void OnSurfaceCreated(const SurfaceInfo& surface_info) override {}
+  void OnSurfaceDestroyed(const SurfaceId& surface_id) override {}
+  bool OnSurfaceDamaged(const SurfaceId& surface_id,
+                        const cc::BeginFrameAck& ack) override;
+  void OnSurfaceDiscarded(const SurfaceId& surface_id) override;
+  void OnSurfaceDamageExpected(const SurfaceId& surface_id,
+                               const cc::BeginFrameArgs& args) override {}
+
+  // Called when a surface has been aggregated and added to the
+  // display frame.  HitTestRegionList objects are held but ignored until
+  // this happens.  HitTestRegionList for the surface is copied from |pending_|
+  // to |active_| in this method.
+  void OnSurfaceWillDraw(const SurfaceId& surface_id) override;
+
+  // The collection of received HitTestRegionList objects that have not yet
+  // been added to the DisplayFrame (OnSurfaceWillDraw has not been called).
+  std::map<SurfaceId, mojom::HitTestRegionListPtr> pending_;
+
+  // The collection of HitTestRegionList objects that have been added to the
+  // DisplayFrame (OnSurfaceWillDraw has been called).
+  std::map<SurfaceId, mojom::HitTestRegionListPtr> active_;
+
+  // Keeps track of the number of regions in the active list
+  // so that we know when we exceed the available length.
+  int active_region_count_ = 0;
+
+  mojo::ScopedSharedBufferHandle read_handle_;
+  mojo::ScopedSharedBufferHandle write_handle_;
+
+  // The number of elements allocated.
+  int read_size_ = 0;
+  int write_size_ = 0;
+
+  mojo::ScopedSharedBufferMapping read_buffer_;
+  mojo::ScopedSharedBufferMapping write_buffer_;
+
+ private:
+  // Allocates memory for the AggregatedHitTestRegion array.
+  void AllocateHitTestRegionArray();
+  void AllocateHitTestRegionArray(int length);
+
+  // Appends the root element to the AggregatedHitTestRegion array.
+  void AppendRoot(SurfaceId surface_id);
+
+  // Appends a region to the HitTestRegionList structure to recursively
+  // build the tree.
+  int AppendRegion(AggregatedHitTestRegion* regions,
+                   int region_index,
+                   const mojom::HitTestRegionPtr& region);
+
+  // Handles the case when this object is deleted after
+  // the PostTaskAggregation call is scheduled but before invocation.
+  base::WeakPtrFactory<HitTestAggregator> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(HitTestAggregator);
+};
+
+}  // namespace viz
+
+#endif  // COMPONENTS_VIZ_SERVICE_HIT_TEST_HIT_TEST_AGGREGATOR_H_