Add timestamps to synthesized events.

content/browser/renderer_host/input/synthetic_pinch_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_pinch_gesture.h"
 
 #include <cmath>
 
 #include "base/logging.h"
 #include "content/common/input/input_event.h"
 #include "ui/events/latency_info.h"
 
 namespace content {
 
 SyntheticPinchGesture::SyntheticPinchGesture(
     const SyntheticPinchGestureParams& params)
     : params_(params),
-      current_y_0_(0.0f),
-      current_y_1_(0.0f),
+      start_y_0_(0.0f),
+      start_y_1_(0.0f),
       target_y_0_(0.0f),
       target_y_1_(0.0f),
       gesture_source_type_(SyntheticGestureParams::DEFAULT_INPUT),
       state_(SETUP) {
   DCHECK_GE(params_.total_num_pixels_covered, 0);
 }
 
 SyntheticPinchGesture::~SyntheticPinchGesture() {}
 
 SyntheticGesture::Result SyntheticPinchGesture::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
     return SyntheticGesture::GESTURE_SOURCE_TYPE_NOT_IMPLEMENTED;
 
   return (state_ == DONE) ? SyntheticGesture::GESTURE_FINISHED
                           : SyntheticGesture::GESTURE_RUNNING;
 }
 
 void SyntheticPinchGesture::ForwardTouchInputEvents(
-    const base::TimeDelta& interval, SyntheticGestureTarget* target) {
+    const base::TimeTicks& timestamp, SyntheticGestureTarget* target) {
   switch (state_) {
     case STARTED:
       // Check for an early finish.
       if (params_.total_num_pixels_covered == 0) {
         state_ = DONE;
         break;
       }
       SetupCoordinates(target);
-      PressTouchPoints(target);
+      PressTouchPoints(target, timestamp);
       state_ = MOVING;
       break;
-    case MOVING:
-      UpdateTouchPoints(interval);
-      MoveTouchPoints(target);
-      if (HasReachedTarget()) {
-        ReleaseTouchPoints(target);
+    case MOVING: {
+      base::TimeTicks event_timestamp = timestamp;
+      float delta = GetDeltaForPointer0AndUpdateTimestamp(&event_timestamp);
+      MoveTouchPoints(target, delta, event_timestamp);
+      if (HasReachedTarget(delta)) {
+        ReleaseTouchPoints(target, event_timestamp);
         state_ = DONE;
       }
-      break;
+    } break;
     case SETUP:
       NOTREACHED() << "State SETUP invalid for synthetic pinch.";
     case DONE:
       NOTREACHED() << "State DONE invalid for synthetic pinch.";
   }
 }
 
-void SyntheticPinchGesture::UpdateTouchPoints(base::TimeDelta interval) {
-  // Compute the delta for the first pointer. The other one moves exactly
-  // the same but in the opposite direction.
-  float delta = GetDeltaForPointer0(interval);
-  current_y_0_ += delta;
-  current_y_1_ -= delta;
+void SyntheticPinchGesture::PressTouchPoints(SyntheticGestureTarget* target,
+                                             const base::TimeTicks& timestamp) {
+  touch_event_.PressPoint(params_.anchor.x(), start_y_0_);
+  touch_event_.PressPoint(params_.anchor.x(), start_y_1_);
+  ForwardTouchEvent(target, timestamp);
 }
 
-void SyntheticPinchGesture::PressTouchPoints(SyntheticGestureTarget* target) {
-  touch_event_.PressPoint(params_.anchor.x(), current_y_0_);
-  touch_event_.PressPoint(params_.anchor.x(), current_y_1_);
-  ForwardTouchEvent(target);
-}
+void SyntheticPinchGesture::MoveTouchPoints(SyntheticGestureTarget* target,
+                                            float delta,
+                                            const base::TimeTicks& timestamp) {
+  // The two pointers move in opposite directions.
+  float current_y_0 = start_y_0_ + delta;
+  float current_y_1 = start_y_1_ - delta;
 
-void SyntheticPinchGesture::MoveTouchPoints(SyntheticGestureTarget* target) {
   // The current pointer positions are stored as float but the pointer
   // coordinates of the input event are integers. Floor both positions so that
   // in case of an odd distance one of the pointers (the one whose position goes
   // down) moves one pixel further than the other. The explicit flooring is only
   // needed for negative values.
-  touch_event_.MovePoint(0, params_.anchor.x(), floor(current_y_0_));
-  touch_event_.MovePoint(1, params_.anchor.x(), floor(current_y_1_));
-  ForwardTouchEvent(target);
+  touch_event_.MovePoint(0, params_.anchor.x(), floor(current_y_0));
+  touch_event_.MovePoint(1, params_.anchor.x(), floor(current_y_1));
+  ForwardTouchEvent(target, timestamp);
 }
 
-void SyntheticPinchGesture::ReleaseTouchPoints(SyntheticGestureTarget* target) {
+void SyntheticPinchGesture::ReleaseTouchPoints(
+    SyntheticGestureTarget* target, const base::TimeTicks& timestamp) {
   touch_event_.ReleasePoint(0);
   touch_event_.ReleasePoint(1);
-  ForwardTouchEvent(target);
+  ForwardTouchEvent(target, timestamp);
 }
 
-
-void SyntheticPinchGesture::ForwardTouchEvent(SyntheticGestureTarget* target)
-    const {
+void SyntheticPinchGesture::ForwardTouchEvent(
+    SyntheticGestureTarget* target, const base::TimeTicks& timestamp) {
+  touch_event_.timeStampSeconds = ConvertTimestampToSeconds(timestamp);
   target->DispatchInputEventToPlatform(
       InputEvent(touch_event_, ui::LatencyInfo(), false));
 }
 
 void SyntheticPinchGesture::SetupCoordinates(SyntheticGestureTarget* target) {
   const float kTouchSlopInDips = target->GetTouchSlopInDips();
   float inner_distance_to_anchor = 2 * kTouchSlopInDips;
   float outer_distance_to_anchor = inner_distance_to_anchor +
                                    params_.total_num_pixels_covered / 2.0f +
                                    kTouchSlopInDips;
 
   // Move pointers away from each other to zoom in
   // or towards each other to zoom out.
   if (params_.zoom_in) {
-    current_y_0_ = params_.anchor.y() - inner_distance_to_anchor;
-    current_y_1_ = params_.anchor.y() + inner_distance_to_anchor;
+    start_y_0_ = params_.anchor.y() - inner_distance_to_anchor;
+    start_y_1_ = params_.anchor.y() + inner_distance_to_anchor;
     target_y_0_ = params_.anchor.y() - outer_distance_to_anchor;
     target_y_1_ = params_.anchor.y() + outer_distance_to_anchor;
   } else {
-    current_y_0_ = params_.anchor.y() - outer_distance_to_anchor;
-    current_y_1_ = params_.anchor.y() + outer_distance_to_anchor;
+    start_y_0_ = params_.anchor.y() - outer_distance_to_anchor;
+    start_y_1_ = params_.anchor.y() + outer_distance_to_anchor;
     target_y_0_ = params_.anchor.y() - inner_distance_to_anchor;
     target_y_1_ = params_.anchor.y() + inner_distance_to_anchor;
   }
 }
 
-float SyntheticPinchGesture::GetDeltaForPointer0(
-    const base::TimeDelta& interval) const {
-  float total_abs_delta =
-      params_.relative_pointer_speed_in_pixels_s * interval.InSecondsF();
+float SyntheticPinchGesture::GetDeltaForPointer0AndUpdateTimestamp(
+    base::TimeTicks* timestamp) const {
+  float total_abs_delta = params_.relative_pointer_speed_in_pixels_s *

[jdduke (slow), 2014/01/03 18:24:30]

DCHECK(timestamp);

[Dominik Grewe, 2014/01/06 11:46:07]

Done.

+                          (*timestamp - start_time_).InSecondsF();
 
   // Make sure we're not moving too far in the final step.
-  total_abs_delta =
-      std::min(total_abs_delta, ComputeAbsoluteRemainingDistance());
+  if (total_abs_delta > ComputeAbsoluteDistance()) {
+    total_abs_delta = ComputeAbsoluteDistance();
+
+    // Update timestamp to match the end of the gesture.
+    int total_duration_in_ms = (1000.0f * ComputeAbsoluteDistance()) /

[jdduke (slow), 2014/01/03 18:24:30]

Nit: This may be slightly more readable as: 

1000.f * (ComputeAbsoluteDistance() /
params_.relative_pointer_speed_in_pixels_s);

[Dominik Grewe, 2014/01/06 11:46:07]

Done.

+                               params_.relative_pointer_speed_in_pixels_s;
+    *timestamp =
+        start_time_ + base::TimeDelta::FromMilliseconds(total_duration_in_ms);
+  }
 
   float abs_delta_pointer_0 = total_abs_delta / 2;
   return params_.zoom_in ? -abs_delta_pointer_0 : abs_delta_pointer_0;
 }
 
-float SyntheticPinchGesture::ComputeAbsoluteRemainingDistance() const {
-  float distance_0 = params_.zoom_in ? (current_y_0_ - target_y_0_)
-                                     : (target_y_0_ - current_y_0_);
+float SyntheticPinchGesture::ComputeAbsoluteDistance() const {
+  float distance_0 =
+      params_.zoom_in ? (start_y_0_ - target_y_0_) : (target_y_0_ - start_y_0_);
   DCHECK_GE(distance_0, 0);
 
   // Both pointers move the same overall distance at the same speed.
   return 2 * distance_0;
 }
 
-bool SyntheticPinchGesture::HasReachedTarget() const {
-  return ComputeAbsoluteRemainingDistance() == 0;
+bool SyntheticPinchGesture::HasReachedTarget(float delta) const {
+  return start_y_0_ + delta == target_y_0_;

[jdduke (slow), 2014/01/03 18:24:30]

Is it possible we'd run into floating point precision issues here? Is this worth
an epsilon check?

[Dominik Grewe, 2014/01/06 11:46:07]

I don't think that this could cause problems. In the final step delta is set to
|(+/-)params.total_num_pixels_covered / 2| (I got rid of
ComputeAbsoluteDistance), where |params.total_num_pixels_covered| is an integer,
which is exactly the difference between |start_y_0_| and |target_y_0_| (see
SetupCoordinates).

 }
 
 }  // namespace content