Add viz-host HitTestQuery.

components/viz/host/hit_test/hit_test_query.h

+// 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_HOST_HIT_TEST_HIT_TEST_QUERY_H_
+#define COMPONENTS_VIZ_HOST_HIT_TEST_HIT_TEST_QUERY_H_
+
+#include <vector>
+
+#include "base/macros.h"
+#include "components/viz/common/hit_test/aggregated_hit_test_region.h"
+#include "ui/gfx/geometry/point.h"
+
+namespace viz {
+
+struct Target {
+  FrameSinkId frame_sink_id;
+  // Coordinates in the coordinate system of the target FrameSinkId.
+  gfx::Point location_in_target;
+  // Different flags are defined in services/viz/hit_test/public/interfaces/
+  // hit_test_region_list.mojom.
+  uint32_t flags = 0;
+};
+
+// Finds the target for a given location based on the AggregatedHitTestRegion
+// list aggregated by HitTestAggregator.
+// TODO(riajiang): Handle 3d space cases correctly.
+class HitTestQuery {
+ public:
+  HitTestQuery();
+  ~HitTestQuery();
+
+  // TODO(riajiang): Read from shmem directly once it's set up and delete this
+  // function. For now, use fake data.
+  void set_aggregated_hit_test_region_list(

[gklassen, 2017/07/18 13:12:57]

A recommendation: One method to set both the list and the size 

eg. set_aggregated_hit_test_region_list(AggregatedHitTestRegion*, uint32_t size)

would ensure that one is never set without the other. 

[riajiang, 2017/07/19 17:45:55]

Good point! Done.

+      AggregatedHitTestRegion* aggregated_hit_test_region_list) {
+    aggregated_hit_test_region_list_ = aggregated_hit_test_region_list;
+  }
+  void set_aggregated_hit_test_region_list_size(
+      uint32_t aggregated_hit_test_region_list_size) {
+    aggregated_hit_test_region_list_size_ =
+        aggregated_hit_test_region_list_size;
+  }
+
+  // Finds Target for |location_in_root|, including the FrameSinkId of the
+  // target, updated location in the coordinate system of the target and
+  // hit-test flags for the target.
+  // Assumptions about the AggregatedHitTestRegion list received.
+  // 1. The list is in ascending (front to back) z-order.
+  // 2. Children count includes children of children.
+  // 3. After applying transform to the incoming point, point is in the same
+  // coordinate system as the bounds it is comparing against.
+  // For example,
+  //  +e-------------+
+  //  |   +c---------|
+  //  | 1 |+a--+     |
+  //  |   || 2 |     |
+  //  |   |+b--------|
+  //  |   ||         |
+  //  |   ||   3     |
+  //  +--------------+
+  // In this case, after applying identity transform, 1 is in the coordinate
+  // system of e; apply the transfrom-from-e-to-c and transform-from-c-to-a
+  // then we get 2 in the coordinate system of a; apply the
+  // transfrom-from-e-to-c and transform-from-c-to-b then we get 3 in the
+  // coordinate system of b.
+  Target FindTargetForLocation(const gfx::Point& location_in_root);
+
+ private:
+  // Helper function to find |target| for |location_in_parent| in the |region|,
+  // returns true if a target is found and false otherwise. |location_in_parent|
+  // is in the coordinate space of |region|'s parent.
+  bool FindTargetInRegionForLocation(const gfx::Point& location_in_parent,
+                                     AggregatedHitTestRegion* region,
+                                     Target* target) const;
+
+  AggregatedHitTestRegion* aggregated_hit_test_region_list_ = nullptr;
+  uint32_t aggregated_hit_test_region_list_size_ = 0;
+
+  DISALLOW_COPY_AND_ASSIGN(HitTestQuery);
+};
+
+}  // namespace viz
+
+#endif  // COMPONENTS_VIZ_HOST_HIT_TEST_HIT_TEST_QUERY_H_