Add timestamps to synthesized events.

content/browser/renderer_host/input/synthetic_smooth_scroll_gesture.cc

 // Copyright 2013 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 "content/browser/renderer_host/input/synthetic_smooth_scroll_gesture.h"
 
 #include "base/logging.h"
 #include "content/common/input/input_event.h"
 #include "ui/events/latency_info.h"
 #include "ui/gfx/point_f.h"
@@ skipping 17 matching lines @@
 
 SyntheticSmoothScrollGesture::SyntheticSmoothScrollGesture(
     const SyntheticSmoothScrollGestureParams& params)
     : params_(params),
       gesture_source_type_(SyntheticGestureParams::DEFAULT_INPUT),
       state_(SETUP) {}
 
 SyntheticSmoothScrollGesture::~SyntheticSmoothScrollGesture() {}
 
 SyntheticGesture::Result SyntheticSmoothScrollGesture::ForwardInputEvents(
-    const base::TimeDelta& interval, SyntheticGestureTarget* target) {
+    const base::TimeTicks& timestamp, SyntheticGestureTarget* target) {
   if (state_ == SETUP) {
     gesture_source_type_ = params_.gesture_source_type;
     if (gesture_source_type_ == SyntheticGestureParams::DEFAULT_INPUT)
       gesture_source_type_ = target->GetDefaultSyntheticGestureSourceType();
 
     if (!target->SupportsSyntheticGestureSourceType(gesture_source_type_))
       return SyntheticGesture::GESTURE_SOURCE_TYPE_NOT_SUPPORTED_BY_PLATFORM;
 
     state_ = STARTED;
+    start_time_ = timestamp;
   }
 
   DCHECK_NE(gesture_source_type_, SyntheticGestureParams::DEFAULT_INPUT);
   if (gesture_source_type_ == SyntheticGestureParams::TOUCH_INPUT)
-    ForwardTouchInputEvents(interval, target);
+    ForwardTouchInputEvents(timestamp, target);
   else if (gesture_source_type_ == SyntheticGestureParams::MOUSE_INPUT)
-    ForwardMouseInputEvents(interval, target);
+    ForwardMouseInputEvents(timestamp, target);
   else
     return SyntheticGesture::GESTURE_SOURCE_TYPE_NOT_IMPLEMENTED;
 
   return (state_ == DONE) ? SyntheticGesture::GESTURE_FINISHED
                           : SyntheticGesture::GESTURE_RUNNING;
 }
 
 void SyntheticSmoothScrollGesture::ForwardTouchInputEvents(
-    const base::TimeDelta& interval, SyntheticGestureTarget* target) {
+    const base::TimeTicks& timestamp, SyntheticGestureTarget* target) {
+  base::TimeTicks event_timestamp = timestamp;
   switch (state_) {
     case STARTED:
       // Check for an early finish.
       if (params_.distance.IsZero()) {
         state_ = DONE;
         break;
       }
       AddTouchSlopToDistance(target);
-      PressTouchPoint(target);
+      ComputeAndSetStopScrollingTime();
+      PressTouchPoint(target, event_timestamp);
       state_ = MOVING;
       break;
-    case MOVING:
-      total_delta_ += GetPositionDelta(interval);
-      MoveTouchPoint(target);
+    case MOVING: {
+      event_timestamp = ClampTimestamp(timestamp);
+      gfx::Vector2dF delta =
+          GetPositionDeltaAtTime(event_timestamp);
+      MoveTouchPoint(target, delta, event_timestamp);
 
-      if (HasScrolledEntireDistance()) {
+      if (HasScrolledEntireDistance(event_timestamp)) {
         if (params_.prevent_fling) {
           state_ = STOPPING;
         } else {
-          ReleaseTouchPoint(target);
+          ReleaseTouchPoint(target, event_timestamp);
           state_ = DONE;
         }
       }
-      break;
+    } break;
     case STOPPING:
-      total_stopping_wait_time_ += interval;
-      if (total_stopping_wait_time_ >= target->PointerAssumedStoppedTime()) {
+      if (timestamp - stop_scrolling_time_ >=
+          target->PointerAssumedStoppedTime()) {
+        event_timestamp =
+            stop_scrolling_time_ + target->PointerAssumedStoppedTime();
         // Send one last move event, but don't change the location. Without this
         // we'd still sometimes cause a fling on Android.
-        MoveTouchPoint(target);
-        ReleaseTouchPoint(target);
+        ForwardTouchEvent(target, event_timestamp);
+        ReleaseTouchPoint(target, event_timestamp);
         state_ = DONE;
       }
       break;
     case SETUP:
       NOTREACHED()
           << "State STARTED invalid for synthetic scroll using touch input.";
     case DONE:
       NOTREACHED()
           << "State DONE invalid for synthetic scroll using touch input.";
   }
 }
 
 void SyntheticSmoothScrollGesture::ForwardMouseInputEvents(
-    const base::TimeDelta& interval, SyntheticGestureTarget* target) {
+    const base::TimeTicks& timestamp, SyntheticGestureTarget* target) {
   switch (state_) {
     case STARTED:
       // Check for an early finish.
       if (params_.distance.IsZero()) {
         state_ = DONE;
         break;
       }
+      ComputeAndSetStopScrollingTime();
       state_ = MOVING;
       // Fall through to forward the first event.
-    case MOVING:
-      {
-        // Even though WebMouseWheelEvents take floating point deltas,
-        // internally the scroll position is stored as an integer. We therefore
-        // keep track of the discrete delta which is consistent with the
-        // internal scrolling state. This ensures that when the gesture has
-        // finished we've scrolled exactly the specified distance.
-        total_delta_ += GetPositionDelta(interval);
-        gfx::Vector2d delta_discrete =
-            FloorTowardZero(total_delta_ - total_delta_discrete_);
-        ForwardMouseWheelEvent(target, delta_discrete);
-        total_delta_discrete_ += delta_discrete;
-      }
-      if (HasScrolledEntireDistance())
+    case MOVING: {
+      // Even though WebMouseWheelEvents take floating point deltas,
+      // internally the scroll position is stored as an integer. We therefore
+      // keep track of the discrete delta which is consistent with the
+      // internal scrolling state. This ensures that when the gesture has
+      // finished we've scrolled exactly the specified distance.
+      base::TimeTicks event_timestamp = ClampTimestamp(timestamp);
+      gfx::Vector2dF total_delta =
+          GetPositionDeltaAtTime(event_timestamp);
+      gfx::Vector2d delta_discrete =
+          FloorTowardZero(total_delta - total_delta_discrete_);
+      ForwardMouseWheelEvent(target, delta_discrete, event_timestamp);
+      total_delta_discrete_ += delta_discrete;
+
+      if (HasScrolledEntireDistance(event_timestamp))
         state_ = DONE;
-      break;
+    } break;
     case SETUP:
       NOTREACHED()
           << "State STARTED invalid for synthetic scroll using touch input.";
     case STOPPING:
       NOTREACHED()
           << "State STOPPING invalid for synthetic scroll using touch input.";
     case DONE:
       NOTREACHED()
           << "State DONE invalid for synthetic scroll using touch input.";
-    }
+  }
 }
 
 void SyntheticSmoothScrollGesture::ForwardTouchEvent(
-    SyntheticGestureTarget* target) const {
+    SyntheticGestureTarget* target, const base::TimeTicks& timestamp) {
+  touch_event_.timeStampSeconds = ConvertTimestampToSeconds(timestamp);
+
   target->DispatchInputEventToPlatform(
       InputEvent(touch_event_, ui::LatencyInfo(), false));
 }
 
 void SyntheticSmoothScrollGesture::ForwardMouseWheelEvent(
-    SyntheticGestureTarget* target, const gfx::Vector2dF& delta) const {
+    SyntheticGestureTarget* target,
+    const gfx::Vector2dF& delta,
+    const base::TimeTicks& timestamp) const {
   blink::WebMouseWheelEvent mouse_wheel_event =
       SyntheticWebMouseWheelEventBuilder::Build(delta.x(), delta.y(), 0, false);
 
   mouse_wheel_event.x = params_.anchor.x();
   mouse_wheel_event.y = params_.anchor.y();
 
+  mouse_wheel_event.timeStampSeconds = ConvertTimestampToSeconds(timestamp);
+
   target->DispatchInputEventToPlatform(
       InputEvent(mouse_wheel_event, ui::LatencyInfo(), false));
 }
 
 void SyntheticSmoothScrollGesture::PressTouchPoint(
-    SyntheticGestureTarget* target) {
+    SyntheticGestureTarget* target, const base::TimeTicks& timestamp) {
   touch_event_.PressPoint(params_.anchor.x(), params_.anchor.y());
-  ForwardTouchEvent(target);
+  ForwardTouchEvent(target, timestamp);
 }
 
 void SyntheticSmoothScrollGesture::MoveTouchPoint(
-    SyntheticGestureTarget* target) {
-  gfx::PointF touch_position = params_.anchor + total_delta_;
+    SyntheticGestureTarget* target,
+    const gfx::Vector2dF& delta,
+    const base::TimeTicks& timestamp) {
+  gfx::PointF touch_position = params_.anchor + delta;
   touch_event_.MovePoint(0, touch_position.x(), touch_position.y());
-  ForwardTouchEvent(target);
+  ForwardTouchEvent(target, timestamp);
 }
 
 void SyntheticSmoothScrollGesture::ReleaseTouchPoint(
-    SyntheticGestureTarget* target) {
+    SyntheticGestureTarget* target, const base::TimeTicks& timestamp) {
   touch_event_.ReleasePoint(0);
-  ForwardTouchEvent(target);
+  ForwardTouchEvent(target, timestamp);
 }
 
 void SyntheticSmoothScrollGesture::AddTouchSlopToDistance(
     SyntheticGestureTarget* target) {
   // Android uses euclidean distance to compute if a touch pointer has moved
   // beyond the slop, while Aura uses Manhattan distance. We're using Euclidean
   // distance and round up to the nearest integer.
   // For vertical and horizontal scrolls (the common case), both methods produce
   // the same result.
-  gfx::Vector2dF touch_slop_delta = ProjectLengthOntoScrollDirection(
-      target->GetTouchSlopInDips());
+  gfx::Vector2dF touch_slop_delta =
+      ProjectLengthOntoScrollDirection(target->GetTouchSlopInDips());
   params_.distance += CeilFromZero(touch_slop_delta);
 }
 
-gfx::Vector2dF SyntheticSmoothScrollGesture::GetPositionDelta(
-    const base::TimeDelta& interval) const {
-  float delta_length = params_.speed_in_pixels_s * interval.InSecondsF();
+gfx::Vector2dF SyntheticSmoothScrollGesture::GetPositionDeltaAtTime(
+    const base::TimeTicks& timestamp) const {
+  // Make sure the final delta is correct. Using the computation below can lead
+  // to issues with floating point precision.
+  if (timestamp == stop_scrolling_time_)

[jdduke (slow), 2014/01/06 21:41:14]

Let's re-use the check below:

HasScrolledEntireDistance(timestamp)

+    return -params_.distance;
 
-  // Make sure we're not scrolling too far.
-  gfx::Vector2dF remaining_delta = ComputeRemainingDelta();
-  if (delta_length > remaining_delta.Length())
-    // In order to scroll in a certain direction we need to move the
-    // touch pointer/mouse wheel in the opposite direction.
-    return -remaining_delta;
-  else
-    return -ProjectLengthOntoScrollDirection(delta_length);
+  float delta_length =
+      params_.speed_in_pixels_s * (timestamp - start_time_).InSecondsF();
+  return -ProjectLengthOntoScrollDirection(delta_length);
 }
 
 gfx::Vector2dF SyntheticSmoothScrollGesture::ProjectLengthOntoScrollDirection(
     float delta_length) const {
   const float kTotalLength = params_.distance.Length();
   return ScaleVector2d(params_.distance, delta_length / kTotalLength);
 }
 
-gfx::Vector2dF SyntheticSmoothScrollGesture::ComputeRemainingDelta() const {
-  return params_.distance + total_delta_;
+void SyntheticSmoothScrollGesture::ComputeAndSetStopScrollingTime() {
+  int64 total_duration_in_us = static_cast<int64>(
+      1e6 * (params_.distance.Length() / params_.speed_in_pixels_s));
+  stop_scrolling_time_ =
+      start_time_ + base::TimeDelta::FromMicroseconds(total_duration_in_us);
 }
 
-bool SyntheticSmoothScrollGesture::HasScrolledEntireDistance() const {
-  return ComputeRemainingDelta().IsZero();
+base::TimeTicks SyntheticSmoothScrollGesture::ClampTimestamp(
+    const base::TimeTicks& timestamp) const {
+  return std::min(timestamp, stop_scrolling_time_);
+}
+
+bool SyntheticSmoothScrollGesture::HasScrolledEntireDistance(
+    const base::TimeTicks& timestamp) const {
+  return timestamp == stop_scrolling_time_;

[jdduke (slow), 2014/01/06 21:41:14]

Let's make this general with

return timestamp >= stop_scrolling_time_;

 }
 
 }  // namespace content