WIP Hittest Component.

components/viz/hit_test/display_hit_test_data.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_HIT_TEST_HIT_TEST_DATA_H_
+#define COMPONENTS_VIZ_HIT_TEST_HIT_TEST_DATA_H_
+
+#include <stdint.h>
+
+#include <map>
+#include <memory>
+
+#include "cc/surfaces/surface_id.h"
+#include "cc/surfaces/surface_observer.h"
+#include "components/viz/hit_test/hit_test_export.h"
+#include "components/viz/hit_test/public/interfaces/hit_test_data.mojom.h"
+#include "hit_test_aggregator.h"
+#include "ui/gfx/geometry/quad_f.h"
+
+namespace viz {
+
+// DiplayHitTestData contains the hit_test data for the Display.
+//
+// It is designed to be in shared memory so that
+// - the viz process can collect and write the hit_test data, and
+// - other processes can access without process hops or mojo calls

[rjkroege, 2017/06/07 21:19:04]

sentences need periods

[gklassen, 2017/06/08 20:33:20]

Done.

+//
+// One instance of this class contains a double buffer of entries -
+// the viz process will write into one half while client processes read from
+// the other.  front_offset_ is used to swap buffers atomically.
+
+// the child_count_ of the last region in the list is set to
+constexpr int kEndOfList = -1;
+
+struct DisplayHitTestRegion {
+  cc::FrameSinkId frame_sink_id_;
+  hit_test::mojom::HitTestRegionFlags flags_;
+  gfx::Rect rect_;
+  gfx::Transform transform_;
+  int child_count_;
+};
+
+struct DisplayHitTestData {
+  int size_;
+  base::subtle::Atomic32 front_offset_;

[rjkroege, 2017/06/07 21:19:04]

per my earlier blither... we could consider using BeginFrame instead of atomics.

+  DisplayHitTestRegion regions_[];

[rjkroege, 2017/06/07 21:19:04]

Some compilers don't like 0-length arrays. You might want to make this a
DisplayHitTestRegion*

[gklassen, 2017/06/08 20:33:20]

if it's a pointer then the struct won't be flat - the pointer will need to be
different in each process ( right? ).  It's possible that we could treat
DisplayHitTestData as a header and expect a following array but that seems odd
as well.  

+};
+
+}  // namespace viz
+
+#endif  //  COMPONENTS_VIZ_HIT_TEST_HIT_TEST_DATA_H_