Decouple EventWithLatencyInfo and WebInputEventTraits [extern templates]

content/common/input/event_with_latency_info.cc

Index: content/common/input/event_with_latency_info.cc
diff --git a/content/common/input/event_with_latency_info.cc b/content/common/input/event_with_latency_info.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c83d2332ceebab3bbdea89c42c554ba4bbd31db4
--- /dev/null
+++ b/content/common/input/event_with_latency_info.cc
@@ -0,0 +1,238 @@
+// 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.
+
+#include "content/common/input/event_with_latency_info.h"
+
+#include <bitset>
+#include <limits>
+
+#include "base/logging.h"
+
+using blink::WebGestureEvent;
+using blink::WebInputEvent;
+using blink::WebKeyboardEvent;
+using blink::WebMouseEvent;
+using blink::WebMouseWheelEvent;
+using blink::WebTouchEvent;
+using std::numeric_limits;
+
+namespace content {
+namespace {
+
+const int kInvalidTouchIndex = -1;
+
+float GetUnacceleratedDelta(float accelerated_delta, float acceleration_ratio) {
+  return accelerated_delta * acceleration_ratio;
+}
+
+float GetAccelerationRatio(float accelerated_delta, float unaccelerated_delta) {
+  if (unaccelerated_delta == 0.f || accelerated_delta == 0.f)
+    return 1.f;
+  return unaccelerated_delta / accelerated_delta;
+}
+
+// Returns |kInvalidTouchIndex| iff |event| lacks a touch with an ID of |id|.
+int GetIndexOfTouchID(const WebTouchEvent& event, int id) {
+  for (unsigned i = 0; i < event.touchesLength; ++i) {
+    if (event.touches[i].id == id)
+      return i;
+  }
+  return kInvalidTouchIndex;
+}
+
+WebInputEvent::DispatchType MergeDispatchTypes(
+    WebInputEvent::DispatchType type_1,
+    WebInputEvent::DispatchType type_2) {
+  static_assert(WebInputEvent::DispatchType::Blocking <
+                    WebInputEvent::DispatchType::EventNonBlocking,
+                "Enum not ordered correctly");
+  static_assert(WebInputEvent::DispatchType::EventNonBlocking <
+                    WebInputEvent::DispatchType::ListenersNonBlockingPassive,
+                "Enum not ordered correctly");
+  static_assert(
+      WebInputEvent::DispatchType::ListenersNonBlockingPassive <
+          WebInputEvent::DispatchType::ListenersForcedNonBlockingPassive,
+      "Enum not ordered correctly");
+  return static_cast<WebInputEvent::DispatchType>(
+      std::min(static_cast<int>(type_1), static_cast<int>(type_2)));
+}
+
+bool CanCoalesce(const blink::WebMouseEvent& event_to_coalesce,
+                 const blink::WebMouseEvent& event) {
+  return event.type == event_to_coalesce.type &&
+         event.type == WebInputEvent::MouseMove;
+}
+
+void Coalesce(const WebMouseEvent& event_to_coalesce, WebMouseEvent* event) {
+  DCHECK(CanCoalesce(event_to_coalesce, *event));
+  // Accumulate movement deltas.
+  int x = event->movementX;
+  int y = event->movementY;
+  *event = event_to_coalesce;
+  event->movementX += x;
+  event->movementY += y;
+}
+
+bool CanCoalesce(const WebMouseWheelEvent& event_to_coalesce,
+                 const WebMouseWheelEvent& event) {
+  return event.modifiers == event_to_coalesce.modifiers &&
+         event.scrollByPage == event_to_coalesce.scrollByPage &&
+         event.phase == event_to_coalesce.phase &&
+         event.momentumPhase == event_to_coalesce.momentumPhase &&
+         event.hasPreciseScrollingDeltas ==
+             event_to_coalesce.hasPreciseScrollingDeltas;
+}
+
+void Coalesce(const WebMouseWheelEvent& event_to_coalesce,
+              WebMouseWheelEvent* event) {
+  DCHECK(CanCoalesce(event_to_coalesce, *event));
+  float unaccelerated_x =
+      GetUnacceleratedDelta(event->deltaX, event->accelerationRatioX) +
+      GetUnacceleratedDelta(event_to_coalesce.deltaX,
+                            event_to_coalesce.accelerationRatioX);
+  float unaccelerated_y =
+      GetUnacceleratedDelta(event->deltaY, event->accelerationRatioY) +
+      GetUnacceleratedDelta(event_to_coalesce.deltaY,
+                            event_to_coalesce.accelerationRatioY);
+  event->deltaX += event_to_coalesce.deltaX;
+  event->deltaY += event_to_coalesce.deltaY;
+  event->wheelTicksX += event_to_coalesce.wheelTicksX;
+  event->wheelTicksY += event_to_coalesce.wheelTicksY;
+  event->accelerationRatioX =
+      GetAccelerationRatio(event->deltaX, unaccelerated_x);
+  event->accelerationRatioY =
+      GetAccelerationRatio(event->deltaY, unaccelerated_y);
+}
+
+bool CanCoalesce(const WebTouchEvent& event_to_coalesce,
+                 const WebTouchEvent& event) {
+  if (event.type != event_to_coalesce.type ||
+      event.type != WebInputEvent::TouchMove ||
+      event.modifiers != event_to_coalesce.modifiers ||
+      event.touchesLength != event_to_coalesce.touchesLength ||
+      event.touchesLength > WebTouchEvent::touchesLengthCap)
+    return false;
+
+  static_assert(WebTouchEvent::touchesLengthCap <= sizeof(int32_t) * 8U,
+                "suboptimal touchesLengthCap size");
+  // Ensure that we have a 1-to-1 mapping of pointer ids between touches.
+  std::bitset<WebTouchEvent::touchesLengthCap> unmatched_event_touches(
+      (1 << event.touchesLength) - 1);
+  for (unsigned i = 0; i < event_to_coalesce.touchesLength; ++i) {
+    int event_touch_index =
+        GetIndexOfTouchID(event, event_to_coalesce.touches[i].id);
+    if (event_touch_index == kInvalidTouchIndex)
+      return false;
+    if (!unmatched_event_touches[event_touch_index])
+      return false;
+    unmatched_event_touches[event_touch_index] = false;
+  }
+  return unmatched_event_touches.none();
+}
+
+void Coalesce(const WebTouchEvent& event_to_coalesce, WebTouchEvent* event) {
+  DCHECK(CanCoalesce(event_to_coalesce, *event));
+  // The WebTouchPoints include absolute position information. So it is
+  // sufficient to simply replace the previous event with the new event->
+  // However, it is necessary to make sure that all the points have the
+  // correct state, i.e. the touch-points that moved in the last event, but
+  // didn't change in the current event, will have Stationary state. It is
+  // necessary to change them back to Moved state.
+  WebTouchEvent old_event = *event;
+  *event = event_to_coalesce;
+  for (unsigned i = 0; i < event->touchesLength; ++i) {
+    int i_old = GetIndexOfTouchID(old_event, event->touches[i].id);
+    if (old_event.touches[i_old].state == blink::WebTouchPoint::StateMoved)
+      event->touches[i].state = blink::WebTouchPoint::StateMoved;
+  }
+  event->movedBeyondSlopRegion |= old_event.movedBeyondSlopRegion;
+  event->dispatchType = MergeDispatchTypes(old_event.dispatchType,
+                                           event_to_coalesce.dispatchType);
+}
+
+bool CanCoalesce(const WebGestureEvent& event_to_coalesce,
+                 const WebGestureEvent& event) {
+  if (event.type != event_to_coalesce.type ||
+      event.sourceDevice != event_to_coalesce.sourceDevice ||
+      event.modifiers != event_to_coalesce.modifiers)
+    return false;
+
+  if (event.type == WebInputEvent::GestureScrollUpdate)
+    return true;
+
+  // GesturePinchUpdate scales can be combined only if they share a focal point,
+  // e.g., with double-tap drag zoom.
+  if (event.type == WebInputEvent::GesturePinchUpdate &&
+      event.x == event_to_coalesce.x && event.y == event_to_coalesce.y)
+    return true;
+
+  return false;
+}
+
+void Coalesce(const WebGestureEvent& event_to_coalesce,
+              WebGestureEvent* event) {
+  DCHECK(CanCoalesce(event_to_coalesce, *event));
+  if (event->type == WebInputEvent::GestureScrollUpdate) {
+    event->data.scrollUpdate.deltaX +=
+        event_to_coalesce.data.scrollUpdate.deltaX;
+    event->data.scrollUpdate.deltaY +=
+        event_to_coalesce.data.scrollUpdate.deltaY;
+    DCHECK_EQ(
+        event->data.scrollUpdate.previousUpdateInSequencePrevented,
+        event_to_coalesce.data.scrollUpdate.previousUpdateInSequencePrevented);
+  } else if (event->type == WebInputEvent::GesturePinchUpdate) {
+    event->data.pinchUpdate.scale *= event_to_coalesce.data.pinchUpdate.scale;
+    // Ensure the scale remains bounded above 0 and below Infinity so that
+    // we can reliably perform operations like log on the values.
+    if (event->data.pinchUpdate.scale < numeric_limits<float>::min())
+      event->data.pinchUpdate.scale = numeric_limits<float>::min();
+    else if (event->data.pinchUpdate.scale > numeric_limits<float>::max())
+      event->data.pinchUpdate.scale = numeric_limits<float>::max();
+  }
+}
+
+}  // namespace
+
+template <class T>
+bool EventWithLatencyInfo<T>::CanCoalesceWith(
+    const EventWithLatencyInfo& other) const {
+  if (other.event.type != event.type)
+    return false;
+
+  DCHECK_EQ(sizeof(T), event.size);
+  DCHECK_EQ(sizeof(T), other.event.size);
+
+  return CanCoalesce(other.event, event);
+}
+
+template <class T>
+void EventWithLatencyInfo<T>::CoalesceWith(const EventWithLatencyInfo& other) {
+  // |other| should be a newer event than |this|.
+  if (other.latency.trace_id() >= 0 && latency.trace_id() >= 0)
+    DCHECK_GT(other.latency.trace_id(), latency.trace_id());
+
+  // New events get coalesced into older events, and the newer timestamp
+  // should always be preserved.
+  const double time_stamp_seconds = other.event.timeStampSeconds;
+  Coalesce(other.event, &event);
+  event.timeStampSeconds = time_stamp_seconds;
+
+  // When coalescing two input events, we keep the oldest LatencyInfo
+  // for Telemetry latency tests, since it will represent the longest
+  // latency.
+  other.latency = latency;
+  other.latency.set_coalesced();
+}
+
+// Explicit instantiations.
+template class EXPORT_TEMPLATE_DEFINE(CONTENT_EXPORT)
+    EventWithLatencyInfo<blink::WebGestureEvent>;
+template class EXPORT_TEMPLATE_DEFINE(CONTENT_EXPORT)
+    EventWithLatencyInfo<blink::WebMouseWheelEvent>;
+template class EXPORT_TEMPLATE_DEFINE(CONTENT_EXPORT)
+    EventWithLatencyInfo<blink::WebMouseEvent>;
+template class EXPORT_TEMPLATE_DEFINE(CONTENT_EXPORT)
+    EventWithLatencyInfo<blink::WebTouchEvent>;
+
+}  // namespace content