Implement compositor thread VSync aligned event queue

ui/events/blink/blink_event_util.cc

Index: ui/events/blink/blink_event_util.cc
diff --git a/ui/events/blink/blink_event_util.cc b/ui/events/blink/blink_event_util.cc
index 360ca65c17de6a56d83d1568845873cb11930205..5148bf1600513a3e43c5be21b0fc44c54f5e3cd7 100644
--- a/ui/events/blink/blink_event_util.cc
+++ b/ui/events/blink/blink_event_util.cc
@@ -10,7 +10,9 @@
 #include <stddef.h>
 
 #include <algorithm>
+#include <bitset>
 #include <cmath>
+#include <limits>
 
 #include "base/time/time.h"
 #include "build/build_config.h"
@@ -27,13 +29,18 @@
 
 using blink::WebGestureEvent;
 using blink::WebInputEvent;
+using blink::WebMouseEvent;
+using blink::WebMouseWheelEvent;
 using blink::WebPointerProperties;
 using blink::WebTouchEvent;
 using blink::WebTouchPoint;
+using std::numeric_limits;
 
 namespace ui {
 namespace {
 
+const int kInvalidTouchIndex = -1;
+
 WebInputEvent::Type ToWebTouchEventType(MotionEvent::Action action) {
   switch (action) {
     case MotionEvent::ACTION_DOWN:
@@ -195,8 +202,243 @@ WebTouchPoint CreateWebTouchPoint(const MotionEvent& event,
   return touch;
 }
 
+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::ListenersForcedNonBlockingDueToFling,
+      "Enum not ordered correctly");
+  return static_cast<WebInputEvent::DispatchType>(
+      std::min(static_cast<int>(type_1), static_cast<int>(type_2)));
+}
+
+bool CanCoalesce(const WebMouseEvent& event_to_coalesce,
+                 const 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);
+  float old_deltaX = event->deltaX;
+  float old_deltaY = event->deltaY;
+  float old_wheelTicksX = event->wheelTicksX;
+  float old_wheelTicksY = event->wheelTicksY;
+  float old_movementX = event->movementX;
+  float old_movementY = event->movementY;
+  *event = event_to_coalesce;
+  event->deltaX += old_deltaX;
+  event->deltaY += old_deltaY;
+  event->wheelTicksX += old_wheelTicksX;
+  event->wheelTicksY += old_wheelTicksY;
+  event->movementX += old_movementX;
+  event->movementY += old_movementY;
+  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::kTouchesLengthCap)
+    return false;
+
+  static_assert(WebTouchEvent::kTouchesLengthCap <= sizeof(int32_t) * 8U,
+                "suboptimal kTouchesLengthCap size");
+  // Ensure that we have a 1-to-1 mapping of pointer ids between touches.
+  std::bitset<WebTouchEvent::kTouchesLengthCap> 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
 
+bool CanCoalesce(const blink::WebInputEvent& event_to_coalesce,
+                 const blink::WebInputEvent& event) {
+  if (blink::WebInputEvent::isGestureEventType(event_to_coalesce.type) &&
+      blink::WebInputEvent::isGestureEventType(event.type)) {
+    return CanCoalesce(
+        static_cast<const blink::WebGestureEvent&>(event_to_coalesce),
+        static_cast<const blink::WebGestureEvent&>(event));
+  }
+  if (blink::WebInputEvent::isMouseEventType(event_to_coalesce.type) &&
+      blink::WebInputEvent::isMouseEventType(event.type)) {
+    return CanCoalesce(
+        static_cast<const blink::WebMouseEvent&>(event_to_coalesce),
+        static_cast<const blink::WebMouseEvent&>(event));
+  }
+  if (blink::WebInputEvent::isTouchEventType(event_to_coalesce.type) &&
+      blink::WebInputEvent::isTouchEventType(event.type)) {
+    return CanCoalesce(
+        static_cast<const blink::WebTouchEvent&>(event_to_coalesce),
+        static_cast<const blink::WebTouchEvent&>(event));
+  }
+  if (event_to_coalesce.type == blink::WebInputEvent::MouseWheel &&
+      event.type == blink::WebInputEvent::MouseWheel) {
+    return CanCoalesce(
+        static_cast<const blink::WebMouseWheelEvent&>(event_to_coalesce),
+        static_cast<const blink::WebMouseWheelEvent&>(event));
+  }
+  return false;
+}
+
+void Coalesce(const blink::WebInputEvent& event_to_coalesce,
+              blink::WebInputEvent* event) {
+  if (blink::WebInputEvent::isGestureEventType(event_to_coalesce.type) &&
+      blink::WebInputEvent::isGestureEventType(event->type)) {
+    Coalesce(static_cast<const blink::WebGestureEvent&>(event_to_coalesce),
+             static_cast<blink::WebGestureEvent*>(event));
+    return;
+  }
+  if (blink::WebInputEvent::isMouseEventType(event_to_coalesce.type) &&
+      blink::WebInputEvent::isMouseEventType(event->type)) {
+    Coalesce(static_cast<const blink::WebMouseEvent&>(event_to_coalesce),
+             static_cast<blink::WebMouseEvent*>(event));
+    return;
+  }
+  if (blink::WebInputEvent::isTouchEventType(event_to_coalesce.type) &&
+      blink::WebInputEvent::isTouchEventType(event->type)) {
+    Coalesce(static_cast<const blink::WebTouchEvent&>(event_to_coalesce),
+             static_cast<blink::WebTouchEvent*>(event));
+    return;
+  }
+  if (event_to_coalesce.type == blink::WebInputEvent::MouseWheel &&
+      event->type == blink::WebInputEvent::MouseWheel) {
+    Coalesce(static_cast<const blink::WebMouseWheelEvent&>(event_to_coalesce),
+             static_cast<blink::WebMouseWheelEvent*>(event));
+  }
+}
+
 blink::WebTouchEvent CreateWebTouchEventFromMotionEvent(
     const MotionEvent& event,
     bool moved_beyond_slop_region) {
@@ -616,4 +858,28 @@ blink::WebInputEvent::Modifiers DomCodeToWebInputEventModifiers(DomCode code) {
   return static_cast<blink::WebInputEvent::Modifiers>(0);
 }
 
+bool IsGestureScollOrPinch(WebInputEvent::Type type) {
+  switch (type) {
+    case blink::WebGestureEvent::GestureScrollBegin:
+    case blink::WebGestureEvent::GestureScrollUpdate:
+    case blink::WebGestureEvent::GestureScrollEnd:
+    case blink::WebGestureEvent::GesturePinchBegin:
+    case blink::WebGestureEvent::GesturePinchUpdate:
+    case blink::WebGestureEvent::GesturePinchEnd:
+      return true;
+    default:
+      return false;
+  }
+}
+
+bool IsContinuousGestureEvent(WebInputEvent::Type type) {
+  switch (type) {
+    case blink::WebGestureEvent::GestureScrollUpdate:
+    case blink::WebGestureEvent::GesturePinchUpdate:
+      return true;
+    default:
+      return false;
+  }
+}
+
 }  // namespace ui