Implement LatencyInfo StructTraits

ui/events/mojo/latency_info_struct_traits.h

Index: ui/events/mojo/latency_info_struct_traits.h
diff --git a/ui/events/mojo/latency_info_struct_traits.h b/ui/events/mojo/latency_info_struct_traits.h
new file mode 100644
index 0000000000000000000000000000000000000000..92e2d22d166a235cf181e12d0b68eee5d5f08cf7
--- /dev/null
+++ b/ui/events/mojo/latency_info_struct_traits.h
@@ -0,0 +1,78 @@
+// Copyright 2016 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 UI_EVENTS_MOJO_LATENCY_INFO_STRUCT_TRAITS_H_
+#define UI_EVENTS_MOJO_LATENCY_INFO_STRUCT_TRAITS_H_
+
+#include "ui/events/latency_info.h"
+#include "ui/events/mojo/latency_info.mojom.h"
+
+namespace mojo {
+
+template <>
+struct StructTraits<ui::mojom::InputCoordinate,
+                    ui::LatencyInfo::InputCoordinate> {
+  static float x(const ui::LatencyInfo::InputCoordinate& input);
+  static float y(const ui::LatencyInfo::InputCoordinate& input);
+  static bool Read(ui::mojom::InputCoordinateDataView data,
+                   ui::LatencyInfo::InputCoordinate* out);
+};
+
+// A buffer used to read bytes directly from LatencyInfoDataView into
+// ui::LatencyInfo's input_coordinates_.
+struct InputCoordinateArray {
+  uint32_t size;
+  ui::LatencyInfo::InputCoordinate* data;
+};
+
+template <>
+struct ArrayTraits<InputCoordinateArray> {

[yzshen1, 2016/06/06 16:15:22]

Now that we have seen C array used in multiple places, maybe we should extra the
array traits for a pre-allocated C array as a common utility?

[Fady Samuel, 2016/06/06 18:00:23]

I'll do this in a follow-on CL. I added a TODO. Thanks!

+  using Element = ui::LatencyInfo::InputCoordinate;
+  static size_t GetSize(const InputCoordinateArray& b);
+  static Element* GetData(InputCoordinateArray& b);
+  static const Element* GetData(const InputCoordinateArray& b);
+  static Element& GetAt(InputCoordinateArray& b, size_t i);
+  static const Element& GetAt(const InputCoordinateArray& b, size_t i);
+  static void Resize(InputCoordinateArray& b, size_t size);
+};
+
+template <>
+struct StructTraits<ui::mojom::LatencyComponent,
+                    ui::LatencyInfo::LatencyComponent> {
+  static int64_t sequence_number(
+      const ui::LatencyInfo::LatencyComponent& component);
+  static base::TimeTicks event_time(
+      const ui::LatencyInfo::LatencyComponent& component);
+  static uint32_t event_count(
+      const ui::LatencyInfo::LatencyComponent& component);
+  static bool Read(ui::mojom::LatencyComponentDataView data,
+                   ui::LatencyInfo::LatencyComponent* out);
+};
+
+template <>
+struct StructTraits<ui::mojom::LatencyComponentId,
+                    std::pair<ui::LatencyComponentType, int64_t>> {
+  static ui::mojom::LatencyComponentType type(
+      const std::pair<ui::LatencyComponentType, int64_t>& id);
+  static int64_t id(const std::pair<ui::LatencyComponentType, int64_t>& id);
+  static bool Read(ui::mojom::LatencyComponentIdDataView data,
+                   std::pair<ui::LatencyComponentType, int64_t>* out);
+};
+
+template <>
+struct StructTraits<ui::mojom::LatencyInfo, ui::LatencyInfo> {
+  static std::string trace_name(const ui::LatencyInfo& info);

[yzshen1, 2016/06/06 16:15:22]

Getter for object fields will be called twice. Returning a value has unnecessary
costs.
Please return a ref for objects that are non-trivial to copy/construct.

If you need extra work to compute/setup the object that you want to return, such
as the latency_components() getter, you can save it in a context object, please
see here:
https://codesearch.chromium.org/chromium/src/mojo/public/cpp/bindings/struct_...

[Fady Samuel, 2016/06/06 18:00:23]

Done. Please let me know if I did this right for latency_components.

+  static mojo::Array<ui::mojom::LatencyComponentPairPtr> latency_components(
+      const ui::LatencyInfo& info);
+  static uint32_t input_coordinates_size(const ui::LatencyInfo& info);
+  static InputCoordinateArray input_coordinates(const ui::LatencyInfo& info);
+  static int64_t trace_id(const ui::LatencyInfo& info);
+  static bool coalesced(const ui::LatencyInfo& info);
+  static bool terminated(const ui::LatencyInfo& info);
+  static bool Read(ui::mojom::LatencyInfoDataView data, ui::LatencyInfo* out);
+};
+
+}  // namespace mojo
+
+#endif  // UI_EVENTS_MOJO_LATENCY_INFO_STRUCT_TRAITS_H_