Event smoothing in CrOS gesture recognizer.

ui/aura/gestures/gesture_point.cc

 // 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.
 
 #include "ui/aura/gestures/gesture_point.h"
 
 #include "ui/aura/event.h"
 #include "ui/base/events.h"
+#include "base/basictypes.h"
 
 namespace {
 
 // TODO(girard): Make these configurable in sync with this CL
 //               http://crbug.com/100773
 const double kMaximumTouchDownDurationInSecondsForClick = 0.8;
 const double kMinimumTouchDownDurationInSecondsForClick = 0.01;
 const double kMaximumSecondsBetweenDoubleClick = 0.7;
 const int kMaximumTouchMoveInPixelsForClick = 20;
 const float kMinFlickSpeedSquared = 550.f * 550.f;
+const int kBufferedPoints = 10;
 
-}  // namespace aura
+}  // namespace
 
 namespace aura {
 
 GesturePoint::GesturePoint()
     : first_touch_time_(0.0),
       last_touch_time_(0.0),
       last_tap_time_(0.0),
-      x_velocity_(0.0),
-      y_velocity_(0.0) {
+      velocity_calculator_(kBufferedPoints) {
 }
 
 void GesturePoint::Reset() {
   first_touch_time_ = last_touch_time_ = 0.0;
-  x_velocity_ = y_velocity_ = 0.0;
+  velocity_calculator_.ClearHistory();
 }
 
 void GesturePoint::UpdateValues(const TouchEvent& event, GestureState state) {
+  const int64 event_timestamp_microseconds =
+    event.time_stamp().InMicroseconds();
   if (state != GS_NO_GESTURE && event.type() == ui::ET_TOUCH_MOVED) {
-    double interval(event.time_stamp().InSecondsF() - last_touch_time_);
-    x_velocity_ = (event.x() - last_touch_position_.x()) / interval;
-    y_velocity_ = (event.y() - last_touch_position_.y()) / interval;
+    velocity_calculator_.PointSeen(event.x(),
+                                   event.y(),
+                                   event_timestamp_microseconds);
   }
 
   last_touch_time_ = event.time_stamp().InSecondsF();
   last_touch_position_ = event.location();
 
   if (state == GS_NO_GESTURE) {
     first_touch_time_ = last_touch_time_;
     first_touch_position_ = event.location();
-    x_velocity_ = 0.0;
-    y_velocity_ = 0.0;
+    velocity_calculator_.ClearHistory();
+    velocity_calculator_.PointSeen(event.x(),
+                                   event.y(),
+                                   event_timestamp_microseconds);
   }
 }
 
 void GesturePoint::UpdateForTap() {
   // Update the tap-position and time, and reset every other state.
   last_tap_time_ = last_touch_time_;
   last_tap_position_ = last_touch_position_;
   Reset();
 }
 
@@ skipping 46 matching lines @@
 }
 
 bool GesturePoint::IsSecondClickInsideManhattanSquare(
     const TouchEvent& event) const {
   int manhattanDistance = abs(event.x() - last_tap_position_.x()) +
                           abs(event.y() - last_tap_position_.y());
   return manhattanDistance < kMaximumTouchMoveInPixelsForClick;
 }
 
 bool GesturePoint::IsOverMinFlickSpeed() const {
-  return (x_velocity_ * x_velocity_ + y_velocity_ * y_velocity_) >
-          kMinFlickSpeedSquared;
+  return velocity_calculator_.VelocitySquared() > kMinFlickSpeedSquared;
 }
 
 }  // namespace aura