Add a passthrough touch event queue.

content/browser/renderer_host/input/passthrough_touch_event_queue.cc

Index: content/browser/renderer_host/input/passthrough_touch_event_queue.cc
diff --git a/content/browser/renderer_host/input/passthrough_touch_event_queue.cc b/content/browser/renderer_host/input/passthrough_touch_event_queue.cc
new file mode 100644
index 0000000000000000000000000000000000000000..084023490ec87a56f96e1ee7590ef6ecafc8b72d
--- /dev/null
+++ b/content/browser/renderer_host/input/passthrough_touch_event_queue.cc
@@ -0,0 +1,376 @@
+// Copyright 2017 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/passthrough_touch_event_queue.h"
+
+#include <utility>
+
+#include "base/auto_reset.h"
+#include "base/macros.h"
+#include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
+#include "base/trace_event/trace_event.h"
+#include "content/browser/renderer_host/input/touch_timeout_handler.h"
+#include "content/common/input/web_touch_event_traits.h"
+#include "ui/events/base_event_utils.h"
+#include "ui/gfx/geometry/point_f.h"

[tdresser, 2017/02/23 15:10:45]

How thoroughly has this changed from legacy_touch_event_queue.cc?

Should I review the whole thing, or are there specific bits to focus on?

[dtapuska, 2017/02/23 16:52:12]

Will comment on the interesting bits.

+
+using blink::WebInputEvent;
+using blink::WebTouchEvent;
+using blink::WebTouchPoint;
+using ui::LatencyInfo;
+
+namespace content {
+namespace {
+
+// Compare all properties of touch points to determine the state.
+bool HasPointChanged(const WebTouchPoint& point_1,
+                     const WebTouchPoint& point_2) {
+  DCHECK_EQ(point_1.id, point_2.id);
+  if (point_1.screenPosition != point_2.screenPosition ||
+      point_1.position != point_2.position ||
+      point_1.radiusX != point_2.radiusX ||
+      point_1.radiusY != point_2.radiusY ||
+      point_1.rotationAngle != point_2.rotationAngle ||
+      point_1.force != point_2.force || point_1.tiltX != point_2.tiltX ||
+      point_1.tiltY != point_2.tiltY) {
+    return true;
+  }
+  return false;
+}
+
+}  // namespace
+
+PassthroughTouchEventQueue::TouchEventWithLatencyInfoAndAckState::
+    TouchEventWithLatencyInfoAndAckState(const TouchEventWithLatencyInfo& event)
+    : TouchEventWithLatencyInfo(event),
+      ack_state_(INPUT_EVENT_ACK_STATE_UNKNOWN) {}
+
+bool PassthroughTouchEventQueue::TouchEventWithLatencyInfoAndAckState::
+operator<(const TouchEventWithLatencyInfoAndAckState& other) const {
+  return event.uniqueTouchEventId < other.event.uniqueTouchEventId;
+}
+
+PassthroughTouchEventQueue::PassthroughTouchEventQueue(
+    TouchEventQueueClient* client,
+    const Config& config)
+    : client_(client),
+      has_handlers_(true),
+      maybe_has_handler_for_current_sequence_(false),
+      drop_remaining_touches_in_sequence_(false),
+      send_touch_events_async_(false) {
+  if (config.touch_ack_timeout_supported) {
+    timeout_handler_.reset(
+        new TouchTimeoutHandler(this, config.desktop_touch_ack_timeout_delay,
+                                config.mobile_touch_ack_timeout_delay));
+  }
+}
+
+PassthroughTouchEventQueue::~PassthroughTouchEventQueue() {}
+
+void PassthroughTouchEventQueue::SendTouchCancelEventForTouchEvent(
+    const TouchEventWithLatencyInfo& event_to_cancel) {
+  TouchEventWithLatencyInfo event = event_to_cancel;
+  WebTouchEventTraits::ResetTypeAndTouchStates(
+      WebInputEvent::TouchCancel,
+      // TODO(rbyers): Shouldn't we use a fresh timestamp?
+      event.event.timeStampSeconds(), &event.event);
+  SendTouchEventImmediately(&event, false);
+}
+
+void PassthroughTouchEventQueue::QueueEvent(
+    const TouchEventWithLatencyInfo& event) {
+  TRACE_EVENT0("input", "PassthroughTouchEventQueue::QueueEvent");
+  PreFilterResult filter_result = FilterBeforeForwarding(event.event);
+  if (filter_result != FORWARD_TO_RENDERER) {
+    client_->OnFilteringTouchEvent(event.event);

[dtapuska, 2017/02/23 16:52:12]

This is interesting code here. The Filtered touch is done right away but the ack
can get held onto to complete the sequence correctly.

+    client_->OnTouchEventAck(event,
+                             filter_result == ACK_WITH_NO_CONSUMER_EXISTS
+                                 ? INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS
+                                 : INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+    return;
+  }
+  TouchEventWithLatencyInfo cloned_event(event);
+  SendTouchEventImmediately(&cloned_event, true);
+}
+
+void PassthroughTouchEventQueue::PrependTouchScrollNotification() {
+  TRACE_EVENT0("input",
+               "PassthroughTouchEventQueue::PrependTouchScrollNotification");
+
+  TouchEventWithLatencyInfo touch(
+      WebInputEvent::TouchScrollStarted, WebInputEvent::NoModifiers,
+      ui::EventTimeStampToSeconds(ui::EventTimeForNow()), LatencyInfo());
+  touch.event.dispatchType = WebInputEvent::EventNonBlocking;
+  SendTouchEventImmediately(&touch, true);
+}
+
+void PassthroughTouchEventQueue::ProcessTouchAck(
+    InputEventAckState ack_result,
+    const LatencyInfo& latency_info,
+    const uint32_t unique_touch_event_id) {
+  TRACE_EVENT0("input", "PassthroughTouchEventQueue::ProcessTouchAck");
+  if (timeout_handler_ &&
+      timeout_handler_->ConfirmTouchEvent(unique_touch_event_id, ack_result))
+    return;
+
+  auto touch_event_iter = outstanding_touches_.begin();
+  while (touch_event_iter != outstanding_touches_.end()) {
+    if (unique_touch_event_id == touch_event_iter->event.uniqueTouchEventId)
+      break;
+    ++touch_event_iter;
+  }
+
+  if (touch_event_iter == outstanding_touches_.end()) {
+    NOTREACHED();
+    return;
+  }
+
+  TouchEventWithLatencyInfoAndAckState event = *touch_event_iter;
+  touch_event_iter = outstanding_touches_.erase(touch_event_iter);
+  event.latency.AddNewLatencyFrom(latency_info);
+  event.set_ack_state(ack_result);
+  outstanding_touches_.insert(touch_event_iter, event);
+
+  AckCompletedEvents();
+}
+
+void PassthroughTouchEventQueue::OnGestureScrollEvent(
+    const GestureEventWithLatencyInfo& gesture_event) {
+  if (gesture_event.event.type() == blink::WebInputEvent::GestureScrollUpdate &&
+      gesture_event.event.resendingPluginId == -1) {
+    send_touch_events_async_ = true;
+  }
+}
+
+void PassthroughTouchEventQueue::OnGestureEventAck(
+    const GestureEventWithLatencyInfo& event,
+    InputEventAckState ack_result) {
+  // Turn events sent during gesture scrolls to be async.
+  if (event.event.type() == blink::WebInputEvent::GestureScrollUpdate &&
+      event.event.resendingPluginId == -1) {
+    send_touch_events_async_ = (ack_result == INPUT_EVENT_ACK_STATE_CONSUMED);
+  }
+}
+
+void PassthroughTouchEventQueue::OnHasTouchEventHandlers(bool has_handlers) {
+  has_handlers_ = has_handlers;
+}
+
+bool PassthroughTouchEventQueue::IsPendingAckTouchStart() const {
+  if (outstanding_touches_.empty())
+    return false;
+
+  return (outstanding_touches_.begin()->event.type() ==
+          WebInputEvent::TouchStart);
+}
+
+void PassthroughTouchEventQueue::SetAckTimeoutEnabled(bool enabled) {
+  if (timeout_handler_)
+    timeout_handler_->SetEnabled(enabled);
+}
+
+void PassthroughTouchEventQueue::SetIsMobileOptimizedSite(
+    bool mobile_optimized_site) {
+  if (timeout_handler_)
+    timeout_handler_->SetUseMobileTimeout(mobile_optimized_site);
+}
+
+bool PassthroughTouchEventQueue::IsAckTimeoutEnabled() const {
+  return timeout_handler_ && timeout_handler_->IsEnabled();
+}
+
+bool PassthroughTouchEventQueue::Empty() const {
+  return outstanding_touches_.empty();
+}
+
+void PassthroughTouchEventQueue::FlushQueue() {
+  drop_remaining_touches_in_sequence_ = true;

[dtapuska, 2017/02/23 16:52:11]

This is interesting

+  while (!outstanding_touches_.empty()) {
+    auto iter = outstanding_touches_.begin();
+    TouchEventWithLatencyInfoAndAckState event = *iter;
+    outstanding_touches_.erase(iter);
+    if (event.ack_state() == INPUT_EVENT_ACK_STATE_UNKNOWN)
+      event.set_ack_state(INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS);
+    AckTouchEventToClient(event, event.ack_state());
+  }
+}
+
+void PassthroughTouchEventQueue::AckCompletedEvents() {

[dtapuska, 2017/02/23 16:52:11]

Interesting

+  while (!outstanding_touches_.empty()) {
+    auto iter = outstanding_touches_.begin();
+    if (iter->ack_state() == INPUT_EVENT_ACK_STATE_UNKNOWN)
+      break;
+    TouchEventWithLatencyInfoAndAckState event = *iter;
+    outstanding_touches_.erase(iter);
+    AckTouchEventToClient(event, event.ack_state());
+  }
+}
+
+void PassthroughTouchEventQueue::AckTouchEventToClient(
+    const TouchEventWithLatencyInfo& acked_event,
+    InputEventAckState ack_result) {
+  UpdateTouchConsumerStates(acked_event.event, ack_result);
+
+  // Skip ack for TouchScrollStarted since it was synthesized within the queue.
+  if (acked_event.event.type() != WebInputEvent::TouchScrollStarted) {
+    client_->OnTouchEventAck(acked_event, ack_result);
+  }
+}
+
+void PassthroughTouchEventQueue::SendTouchEventImmediately(
+    TouchEventWithLatencyInfo* touch,
+    bool wait_for_ack) {
+  // Note: Touchstart events are marked cancelable to allow transitions between
+  // platform scrolling and JS pinching. Touchend events, however, remain
+  // uncancelable, mitigating the risk of jank when transitioning to a fling.
+  if (send_touch_events_async_ &&
+      touch->event.type() != WebInputEvent::TouchStart)
+    touch->event.dispatchType = WebInputEvent::EventNonBlocking;
+
+  if (touch->event.type() == WebInputEvent::TouchStart)
+    touch->event.touchStartOrFirstTouchMove = true;
+
+  // For touchmove events, compare touch points position from current event
+  // to last sent event and update touch points state.
+  if (touch->event.type() == WebInputEvent::TouchMove) {
+    CHECK(last_sent_touchevent_);
+    if (last_sent_touchevent_->type() == WebInputEvent::TouchStart)
+      touch->event.touchStartOrFirstTouchMove = true;
+    for (unsigned int i = 0; i < last_sent_touchevent_->touchesLength; ++i) {
+      const WebTouchPoint& last_touch_point = last_sent_touchevent_->touches[i];
+      // Touches with same id may not have same index in Touches array.
+      for (unsigned int j = 0; j < touch->event.touchesLength; ++j) {
+        const WebTouchPoint& current_touchmove_point = touch->event.touches[j];
+        if (current_touchmove_point.id != last_touch_point.id)
+          continue;
+
+        if (!HasPointChanged(last_touch_point, current_touchmove_point))
+          touch->event.touches[j].state = WebTouchPoint::StateStationary;
+
+        break;
+      }
+    }
+  }
+
+  if (touch->event.type() != WebInputEvent::TouchScrollStarted) {
+    if (last_sent_touchevent_)
+      *last_sent_touchevent_ = touch->event;
+    else
+      last_sent_touchevent_.reset(new WebTouchEvent(touch->event));
+  }
+
+  if (timeout_handler_)
+    timeout_handler_->StartIfNecessary(*touch);
+  if (wait_for_ack)
+    outstanding_touches_.insert(*touch);
+  client_->SendTouchEventImmediately(*touch);
+}
+
+PassthroughTouchEventQueue::PreFilterResult
+PassthroughTouchEventQueue::FilterBeforeForwarding(const WebTouchEvent& event) {
+  if (event.type() == WebInputEvent::TouchScrollStarted)
+    return FORWARD_TO_RENDERER;
+
+  if (WebTouchEventTraits::IsTouchSequenceStart(event)) {
+    // We don't know if we have a handler until we get the ACK back so
+    // assume it is true.
+    maybe_has_handler_for_current_sequence_ = true;

[dtapuska, 2017/02/23 16:52:11]

maybe_ has been added here and inverted.

+    send_touch_events_async_ = false;
+    last_sent_touchevent_.reset();
+
+    drop_remaining_touches_in_sequence_ = false;
+    if (!has_handlers_) {
+      drop_remaining_touches_in_sequence_ = true;
+      return ACK_WITH_NO_CONSUMER_EXISTS;
+    }
+  }
+
+  if (timeout_handler_ && timeout_handler_->FilterEvent(event))
+    return ACK_WITH_NO_CONSUMER_EXISTS;
+
+  if (drop_remaining_touches_in_sequence_ &&
+      event.type() != WebInputEvent::TouchCancel) {
+    return ACK_WITH_NO_CONSUMER_EXISTS;
+  }
+
+  if (event.type() == WebInputEvent::TouchStart) {
+    return (has_handlers_ || maybe_has_handler_for_current_sequence_)
+               ? FORWARD_TO_RENDERER
+               : ACK_WITH_NO_CONSUMER_EXISTS;
+  }
+
+  if (maybe_has_handler_for_current_sequence_) {
+    // Only forward a touch if it has a non-stationary pointer that is active
+    // in the current touch sequence.
+    for (size_t i = 0; i < event.touchesLength; ++i) {
+      const WebTouchPoint& point = event.touches[i];
+      if (point.state == WebTouchPoint::StateStationary)
+        continue;
+
+      // |last_sent_touchevent_| will be non-null as long as there is an
+      // active touch sequence being forwarded to the renderer.
+      if (!last_sent_touchevent_)
+        continue;
+
+      for (size_t j = 0; j < last_sent_touchevent_->touchesLength; ++j) {
+        if (point.id != last_sent_touchevent_->touches[j].id)
+          continue;
+
+        if (event.type() != WebInputEvent::TouchMove)
+          return FORWARD_TO_RENDERER;
+
+        // All pointers in TouchMove events may have state as StateMoved,
+        // even though none of the pointers have not changed in real.
+        // Forward these events when at least one pointer has changed.
+        if (HasPointChanged(last_sent_touchevent_->touches[j], point))
+          return FORWARD_TO_RENDERER;
+
+        // This is a TouchMove event for which we have yet to find a
+        // non-stationary pointer. Continue checking the next pointers
+        // in the |event|.
+        break;
+      }
+    }
+  }
+
+  return ACK_WITH_NO_CONSUMER_EXISTS;
+}
+
+void PassthroughTouchEventQueue::UpdateTouchConsumerStates(
+    const WebTouchEvent& event,
+    InputEventAckState ack_result) {
+  if (event.type() == WebInputEvent::TouchStart) {
+    if (ack_result == INPUT_EVENT_ACK_STATE_CONSUMED)
+      send_touch_events_async_ = false;
+
+    // Once we have the ack back for the sequence we know if there

[dtapuska, 2017/02/23 16:52:12]

This is an interesting block.

+    // is a handler or not. Other touch-starts sent can upgrade
+    // whether we have a handler or not as well.
+    if (WebTouchEventTraits::IsTouchSequenceStart(event)) {
+      maybe_has_handler_for_current_sequence_ =
+          ack_result != INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS;
+    } else {
+      maybe_has_handler_for_current_sequence_ |=
+          ack_result != INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS;
+    }
+  } else if (WebTouchEventTraits::IsTouchSequenceEnd(event)) {
+    maybe_has_handler_for_current_sequence_ = false;
+  }
+}
+
+size_t PassthroughTouchEventQueue::SizeForTesting() const {
+  return outstanding_touches_.size();
+}
+
+bool PassthroughTouchEventQueue::IsTimeoutRunningForTesting() const {
+  return timeout_handler_ && timeout_handler_->IsTimeoutTimerRunning();
+}
+
+const TouchEventWithLatencyInfo&
+PassthroughTouchEventQueue::GetLatestEventForTesting() const {
+  return *outstanding_touches_.rbegin();
+}
+
+}  // namespace content