Event smoothing in CrOS gesture recognizer.

ui/aura/gestures/velocity_calculator.h

+// Copyright (c) 2012 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_AURA_GESTURES_VELOCITY_CALCULATOR_H_
+#define UI_AURA_GESTURES_VELOCITY_CALCULATOR_H_
+#pragma once
+
+#include <vector>
+#include "ui/aura/aura_export.h"
+
+namespace aura {
+
+class AURA_EXPORT VelocityCalculator {
+ public:
+  explicit VelocityCalculator(int bufferSize);
+  ~VelocityCalculator();
+  void PointSeen(float x, float y, double time);
+  void Velocity(float* x, float*y);

[Ian Vollick, 2012/02/02 16:40:23]

Since we want to get the velocity after every point is added, it would make
sense to update the calculated velocities in PointSeen, and then you could have
simple accessors like velocity_x() and velocity_y() for getting the current
estimates.

+  void ClearHistory();

[Ian Vollick, 2012/02/02 16:40:23]

newline between lines 20 and 21

+ private:
+  struct Point {
+    float x;
+    float y;
+    double time;
+  };
+
+  typedef std::vector<Point> HistoryBuffer;

[rjkroege, 2012/02/02 15:58:37]

since the array is fixed size, why not an array?

+  HistoryBuffer buffer_;
+
+  // index_ points directly after the last point added
+  int index_;
+  size_t num_valid_entries_;
+  const size_t buffer_size_;
+};
+}  // namespace aura
+
+#endif  // UI_AURA_GESTURES_VELOCITY_CALCULATOR_H_